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Review

Phthalocyanine-Modified Electrodes Used in the Electroanalysis of Monoamine Neurotransmitters

by
Anton Alexandru Ciucu
1,*,
Mihaela Buleandră
1,
Dana Elena Popa
1 and
Dragoș Cristian Ștefănescu
2
1
Department of Analytical Chemistry and Physical Chemistry, University of Bucharest, 90–92 Panduri Av., District 5, 050663 Bucharest, Romania
2
Faculty of Medicine, “Carol Davila” University of Medicine and Pharmacy, 37th Dionisie Lupu Street, 020022 Bucharest, Romania
*
Author to whom correspondence should be addressed.
Chemosensors 2025, 13(7), 243; https://doi.org/10.3390/chemosensors13070243
Submission received: 13 June 2025 / Revised: 4 July 2025 / Accepted: 4 July 2025 / Published: 7 July 2025
(This article belongs to the Special Issue New Electrodes Materials for Electroanalytical Applications)

Abstract

Metallo-phthalocyanines (MPcs) are versatile materials with applications in electroanalysis because of their superior catalytic properties. This review presents the electrochemical methods based on MPc-modified electrodes and reports some of their remarkable properties and applications in the electroanalysis of monoamine neurotransmitters and biomolecules that play a crucial role in vital functions of the human body. The development of electrocatalytic chemically modified electrodes is based on their ability to provide a selective and rapid response toward a specific analyte in complex media without the need for sample pretreatment. The explanation of several phenomena occurring at the MPc-modified electrode surface (e.g., MPc-mediated electrocatalysis), the advantages of promoting different electron transfer reactions, and the detection mechanism are also presented. The types of MPcs and different materials, such as carbon nanotubes and graphene, used as substrates for modified working electrodes are discussed. Modifying the properties of MPcs through various interactions, or combining MPcs with carbonaceous materials, creates a synergistic effect. Such hybrid materials present both extraordinary catalytic and increased conductivity properties. We conducted a compilation study based on recent works to demonstrate the efficacy of the developed sensors and methods in sensing monoamine neurotransmitters. We emphasize the analyte type, optimized experimental parameters, working range, limits of detection and quantification, and application to real samples. MPc–carbon hybrids have led to the development of sensors with superior sensitivity and improved selectivity, enabling the detection of analytes at lower concentrations. We highlight the main advantages and drawbacks of the discussed methods. This review summarizes recent progress in the development and application of metallo-phthalocyanine-modified electrodes in the electroanalysis of monoamine neurotransmitters. Some possible future trends are highlighted.

1. Introduction

Electrochemical detection is an alternative to classical chemical analysis and has attracted attention due to its simplicity, along with a minimal sample preparation, rapid response, low-cost instruments and an affordable cost per sample analysis [1]. Modern electrochemical methods are sensitive, selective and easily applicable in the electroanalysis of different compounds. These characteristics make them a versatile tool for a variety of applications.
Electrochemical devices offer specific properties to address the challenges of analytical chemistry, including the simultaneous determination of analytes with similar structures. Of these, electrochemical sensors hold an important position among the available detection systems being widely used in electro-analytical applications. In voltammetric detection, the current signal is generated as a function of an analyte redox reaction at the surface of the working electrode. The potential applied between the working and reference electrodes represent the driving force for the electron transfer reaction of the electroactive species. Electrons crossing the electrode–solution interface can be determined by measuring the current, which is a direct measure of the rate of the electron transfer reaction and is proportional to the concentration of the target analyte [2].
Electrochemical sensors utilize modifiers such as metallo-phthalocyanines (MPcs), metal Schiff bases and metallo-porphyrins, which have been used in the design of chemically modified electrodes (CMEs). The modifiers introduce some new chemical and electrochemical properties that the bare electrodes do not have [3]. Such electrodes have allowed the study of various chemical compounds that, on conventional electrodes, exhibit a very slow heterogeneous electron transfer rate and, consequently, irreversible electrochemical behavior. The primary advantages of MPc modifiers include the increase in the electrode response toward new analytes that are either poorly or not at all electrolyzed at bare electrodes, the major control of electrode selectivity and surfaces that are more resistant to electrode fouling [2].
By using MPcs in conjunction with carbonaceous materials, like carbon nanotubes or graphene, it is possible to produce hybrid materials. These MPc hybrids have shown tremendous advantages in electrochemical sensor design. Carbonaceous materials substantially enhance the electrical conductivity and surface area of sensors, allowing improved detection. Furthermore, they increase the sensing performance through their catalytic activity and signal amplification. The nanomaterials add structure support and a more active surface area, while the MPcs improve the electron transfer processes. These synergistic effects can lead to enhanced performance in applications like catalysis and sensing.

2. Metallo-Phthalocyanines

MPcs are a class of compounds with four fused benzo rings containing an 18 π electron conjugated system in which diverse metals and non-metals can be included (Figure 1). The incorporation of different ring substituents in the peripheral and non-peripheral positions is possible [4].
They have applications in the paint industry [5], photodynamic therapy [6], optical sensing [7], optical computer rewritable discs and information storage systems [8], liquid crystal display devices [9], photovoltaic cells [10], fuel cells [11], semiconductor devices [12] and electrochemical sensors [13,14,15,16,17,18]. Many analytes of biological and environmental relevance, including pesticides [19], nitric oxide [20], thiols [21], hydrazine [22] and phenols [23], were detected by MPc-modified electrodes.

2.1. Metallo-Phthalocyanine Properties

MPcs are involved in the fast redox reactions of a plethora of analytes and play the role of electron mediators or electrocatalysts in the electron transfer process at the electrode–solution interface. A major factor contributing to this use is the physical and chemical stability of MPcs during the oxido-reduction reactions.
The reactive centers of MPcs are clearly identified and their reactivity can be modulated by changing the nature of the central metal or peripheral substituents on the phthalocyanine ring. MPcs have rich redox behavior and the well-defined oxidation–reduction peaks can be attributed to the phthalocyanine (Pc) ligand and the metal atoms included in the structure of MPcs. Redox properties of MPcs are correlated with their electrocatalytic characteristics. In the neutral state, the Pc ring has an oxidation state of −2 (Pc2−) [24]. The Pc ring can be oxidized by the successive elimination of up to two electrons and reduced by the successive acceptance of up to four electrons [25,26]. The redox potential of MPcs can be easily modulated by introducing the appropriate substituents on peripheral or non-peripheral positions of the phthalocyanine ligand. In this way the catalytic activity of MPcs for the oxidation or reduction of analytes can be “tuned” by manipulating the formal potential by using the proper groups on the ligand. The central metal ion in MPcs also contribute to tuning the catalytic properties. Among the MPcs, transition metals, such as Co(II), Fe(II), Fe(III) Cu(II), Ni(II) and Mn(II), are commonly used as metal centers in Pcs and assume the role of modifiers (electrocatalysts). Metal oxidation or reduction occurs at potentials between those corresponding to ligand reduction or oxidation. The metal atom at the center of MPcs can undergo reversible redox reactions. Moreover, the MPc central metal atom can be customized to associate specifically with explicit analytes. Copper phthalocyanine has a high affinity for nitrogen-containing compounds, while cobalt phthalocyanines are known for their catalytic activity in oxygen reduction reactions. MPcs have wide working potentials in both anodic and cathodic directions, which allows for the oxidation and reduction of analytes in a large potential window. The redox potentials of the central metal ion in MPcs can be tuned by the choice of the central metal or by the surrounding ligands, leading to synergistic effects in electrocatalysis for different reactions.
The redox properties and catalytic activity of MPcs can be modified by changing the central metal, its oxidation state, and the nature of the axial ligands and ring substituents (substituents at the alpha (α) and beta (β) positions) [27]. As electrocatalysts, the majority of metallo-phthalocyanine complexes involve a change in the oxidation state of the central metal. However, few MPcs have shown ring-based catalysis instead of the central atom catalysis, i.e., the central metal is inactive.
Some MPcs have been studied in both homogeneous and heterogeneous phases as active catalysts in electron transfer reactions involving a great number of molecules [28]. They catalyze the electrooxidation of oxalic acid [29], glucose [30], H2O2 [31], hydrazine [32], mercaptoethanol [33], L-cysteine [34], hydroxylamine [35], dopamine [36,37,38] and phenols [39,40], and the electroreduction of H2O2 [41], alkyl chlorides [42] and cystine [43]. They have been found to enhance the response for solutes whose direct oxidation or reduction is not kinetically favored. Moreover, MPcs have the capacity to mimic the catalytic activity of certain enzymes [44,45,46].

2.2. Electrocatalysis

MPcs are known to mediate/electrocatalyze the redox process at the central metal [47,48,49] and/or ring [50], facilitating the electron transfer of different analytes. The mechanism for the electrocatalytic oxidation process due to the metal center and that for the one due to the ring are described elsewhere [51]. The electrocatalytic effect is evidenced by a shift in the electrode reaction overpotential to a lower value, an increase in the current or both.
Figure 2 shows an electrocatalytic reduction process at the surface of an MPc-based electrode. The MPcs do not participate in the overall reaction, but its role is to shuttle electrons between the analyte and the electrode surface. During the electrocatalytic reduction process, MPc changes its oxidation state by interacting with the analyte and returns to its initial state by donating electrons to the electrode. Electrocatalytic activities are usually observed at potentials close to the formal potential of the MPc.
The use of chemical modifiers (mediators/electrocatalysts) has resulted in better-performing sensors that exhibit increased electron transfer kinetics and electrocatalytic activity, better sensitivity and improved selectivity toward analytes by reducing the influence of the interferents on the electrode response [52].

3. Metallo-Phthalocyanine-Modified Electrodes

Modifying the electrode surface transfers the modifier’s new physicochemical properties to the electrode, providing molecular-level control over the fabrication of the sensing interface. Electrocatalysis of an analyte–electrode reaction represents an important reason for surface modification, which improves the chemical and electrochemical properties of the electrodes. Based on their good electrocatalytic properties, MPc-modified electrodes can reduce the residual current and consequently increase the current response, lowering the detection limits, improving the selectivity and reducing the analysis time.
The only drawback of MPcs used in sensor design is related to the fact that they exhibit semiconducting properties [53]. As a result, new hybrid materials have been developed that combine MPcs with a highly conductive material (e.g., carbon nanotubes). The two modifiers (mediator and carbon nanotubes) show a synergistic effect when co-used to modify the electrode by further lowering the detection potential and increasing the generated currents [54]. The MPc-modified electrodes provide an alternative way to prepare electrochemical sensors that reveal new types of transduction mechanisms [55,56,57,58,59,60,61,62,63,64].

3.1. Carbonaceous Materials for Electrode Modification

Carbon-based nanomaterials have received great attention in research and application in diverse fields. They exhibit a large surface area, biocompatibility, chemical and electrochemical stability, and good electrical conductivity, and are also inexpensive [65]. Such nanomaterials include carbon nanotubes [66], graphene oxide nanosheets [67] and fullerenes (carbon balls) [68]. Graphite is the main source of nanosized carbon materials. Graphite can be oxidized and exfoliated to form graphene oxide nanosheets, which, in turn, can be folded into different shapes, resulting in carbon nanotubes and fullerenes.

3.1.1. Carbon Nanotubes

Carbon nanotubes (CNTs) were discovered by Iijima and they were produced from a cathode by a carbon arc discharge method [69]. They are molecular-scale tubes of graphitic carbon and have become attractive materials for a wide range of applications, including the field of electrochemical sensors [70,71]. This is mainly due to their unique structural, electronic and mechanical properties. These 2D, rigid and strong fibers present a closed topology and tubular structure, along with a hollow core suitable for storing guest molecules. Their large length-to-diameter ratios result in high surface-to-volume ratios.
There are two categories of carbon nanotubes: single-wall (SW) and multi-wall (MW) carbon nanotubes [72]. SWCNTs have a cylindrical nanostructure formed by rolling up a single sheet of graphite (graphene) into a tube with either open or closed ends, depending on the fabrication methodology [73]. The closure of the cylinder is due to pentagonal inclusion in the hexagonal carbon network of the nanotube walls during the growth process. SWCNTs typically have diameters of ~1 nm, with the smallest diameter reported to date of 0.4 nm [74]. The structure of individual graphene tubes is defined by the unit cell, where the open ends may have “zig-zag”, “arm-chair” and “chiral” geometries [75]. MWCNTs are coaxial assemblies of concentrically nested graphene cylinders with an interlayer spacing of 0.34 nm [76], with dimensions ranging from 2 to 30 nm in diameter and several microns in length [77].
The electroanalytical applications of CNTs stem from their excellent electroactivity, resulting in electrocatalytic behavior, and the ability to promote and mediate fast electron transfer kinetics in electrochemical reactions involving a wide range of electroactive species when CNTs are used as electrode materials [78]. CNT-modified electrodes improve electron transfer compared with their unmodified counterparts [79,80,81,82,83]. The origin of electron transfer for CNTs is at the open end of the nanotubes and along the tube axis, where defect sites exist and at which electron transfer is reported to be faster than that of the pristine sidewalls of the nanotubes [84,85].
From the perspective of the electrochemical reactivity, the sidewalls of CNTs are suggested to have properties similar to those of the basal plane of highly oriented pyrolytic graphite (HOPG), while their open ends resemble the edge planes of HOPG. Accordingly, electron transfer rates similar to those of a graphite edge plane electrode can be expected. The open end of an MWCNT has a fast electron transfer rate comparable with that of a graphite edge plane electrode, while an SWCNT presents a very slow electron transfer rate and a low specific capacitance, equivalent to that of the graphite basal plane [86].
The electrocatalytic activity of CNTs is associated with their dimensions, electronic structure and topological defects present on the tube surface [87,88]. The presence of pentagonal defects produces regions of higher charge density than those observed in the region of hexagonal graphite, either in planar or in tubular structures, demonstrating the relationship between topological defects and the electroactivity of CNTs [87]. Compton’s group assumed that this enhanced electrocatalytic activity was due to the edge-plane-like sites located at the ends and in the “defects” areas of the tubes [88]. Moreover, it has been shown that the electrocatalytic activity of MWCNTs strongly depends on the CNT fabrication method and the dispersing agent used to immobilize the CNTs on the electrode surface [89]. The oxygenated species residing at the edge-plane-like sites (defects) of the carbon nanotubes are also considered; it is well known that electrochemically active species may interact favorably or detrimentally with surface oxygenated species [84].
Carbon Nanotubes as Electrode Material
Before application in electroanalytical assays, the synthesized CNTs can be treated to functionalize their surfaces. The functionalization and surface immobilization of CNTs represent a critical step in sensor design. Chemical functionalization of CNTs was used to attach the desired chemical compounds to them. End [90] and/or sidewall [91] functionalization, use of surfactants with sonication [92], polymer wrapping of nanotubes [93] and protonation by superacids [94] have been used for this purpose. The preparation of homogeneous dispersions of CNTs suitable for processing into thin films is of great importance [74]. This has permitted the realization of composite electrodes consisting of CNTs well-dispersed in a suitable polymer matrix [95].
In general, some pre-treatment of the CNTs is required to remove metallic impurities, and/or to improve the electron transfer properties and/or to allow further functionalization. CNT walls are not reactive, but their fullerene-like tips are known to be more reactive, so the end-functionalization of CNTs is used to generate functional groups (e.g., −COOH, −OH or −C=O). The protocols are based on the oxidation of CNTs under different conditions. Treatment with strong acids removes the end caps; may shorten the length of the CNTs; and also adds oxide groups, primarily carboxylic acids, and phenolic groups to the tube ends and defect sites. These functional groups provide sites for the covalent bonding of CNTs to biorecognition elements (or other materials) or for their integration onto polymer surface structures. These oxide groups can undergo further chemical reactions, allowing for functionalization with groups like amides and thiols. Activation by treatment in acidic solutions has been widely used. Solutions of sulfuric [81], nitric [96] and hydrochloric [97] acids, concentrated or diluted, alone or mixed [96], have been used at room temperature.
Electrochemical treatments have also been employed, and in some cases, they were based on a combination of different chemical and electrochemical protocols [98].
The non-covalent functionalization of CNTs by small molecules can alter the electrochemical properties of the material [99]. This type of functionalization is based on weak interactions and can be used to attach small molecules or biochemically active molecules. The CNT solubilization by covalent modification was reported by Luong et al. [100]. Other derivatization methods include defect functionalization [101].
Lower overvoltage and higher peak currents are observed in the voltammetric response of several molecules at CNT-modified electrodes. Due to these unique properties, CNTs have received enormous attention for the preparation of electrochemical sensors, as was extensively reviewed [102,103,104,105,106,107].
Carbon Nanotube Paste Electrodes
By analogy with carbon paste and composite electrodes, similar matrices that involve CNTs have been used in the construction of electrochemical sensors. CNTs can be distributed within the polymer matrix in either a random or vertical orientation. A variety of binders (e.g., mineral oil, Teflon or epoxy resins) were used to produce CNT pastes or composites. CNT paste electrodes have been obtained by mixing CNT powder with deionized water [108], bromoform [109] or mineral oil [110]. The high surface area of CNTs allows the construction of stable, robust paste electrodes with high amounts of mineral oil (50% CNTs and 50% mineral oil).

3.1.2. Graphene

In 2004, researchers Geim and Novoselov discovered and isolated graphene, a two-dimensional atomic crystal with a hexagonal lattice of carbon atoms [111]. Some authors describe graphene as a material “which consists of a single atomic sheet of conjugated sp2 carbon atoms” [112]. The International Union of Pure and Applied Chemistry (IUPAC) defines it as “a single carbon layer of the graphite structure, describing its nature by analogy to a polycyclic aromatic hydrocarbon of quasi-infinite size” [113]. Graphene is the basic structure of all graphitic materials and is a one-atom-thick planar sheet of sp2-bonded carbon atoms in a rigid honeycomb lattice [114]. It resembles a large polyaromatic molecule of semi-infinite size, emerging as a true two-dimensional nanomaterial.
Graphene has excellent properties, such as a high surface-to-volume ratio, high thermal conductivity [115], high electron transfer rates and extraordinary electron mobility [116]. Its thermal stability, robust mechanical strength and flexibility, pliability, impermeability and low energy dynamics of electrons with atomic thickness, as well as good biocompatibility [117], make graphene ideal for fabricating sensitive electrochemical devices. Graphene is an excellent conductor of electrical charge, and heterogeneous electron transfer occurs at its edges or at defects in the basal plane [118]. Furthermore, the high surface area of graphene facilitates the presence of large amounts of defects and electroactive sites [119].
Graphene-based electrodes have shown superior performance in terms of electrocatalytic activity and macroscopic scale conductivity compared with CNT-based ones [120,121]. The main drawback of using CNTs for electrode modification is the presence of electrochemically active metallic impurities [122,123] that can influence the electrochemistry of CNTs. Since graphene does not contain metallic impurities, it is gradually competing with CNTs in many applications [124,125]. Another reason for the considerable interest in graphene is its easy availability.

3.2. Methods of Electrode Modification

Various techniques can be used to modify electrodes with MPcs, which include covalent bonding [126], adsorption (dip drying [127] and drop drying [128]), spin coating [129], electropolymerization [130], the Langmuir–Blodgett technique [131], vapor deposition [132], self-assembled monolayers [133], click chemistry [134] and electrografting [135].
The method of covalent bonding is complicated and involves functional groups of CNTs, such as −COOH or −NH2, which are generally reacted with MPcs. Amino-substituted MPcs complexes can be covalently linked to CNTs via amide bond formation [126].
Non-substituted MPc complexes are adsorbed onto carbon materials via π–π interactions by immersing the electrode in a solution of the complexes for several minutes or placing a drop of a solution containing a known amount of the complexes on the electrode surface. This is a simple and rapid method of electrode modification. This method was chosen because MPcs have a readily available π electron system that can interact with the π electron system of the carbon electrodes, thereby forming a relatively stable π-stacked catalyst film on the electrode surface.
Drop drying is preferable to dip drying because it is possible to control the amount of modifier adsorbed to a certain degree, thereby increasing the reproducibility of the experimental conditions and results. The drop-drying technique is used to deposit the suspension solution of the composite MPc–MWCNT material to the main electrode. It has been observed that phthalocyanine–CNTs complexes have the excellent catalytic properties of phthalocyanines without losing any of the electronic properties of carbon nanotubes [136].
More stable electrodes can be achieved by the electrodeposition of MPc complexes on the electrode surface [13,130,137].

4. Analytical Applications of MPc-Modified Electrodes for Detection of Monoamine Neurotransmitters

Neurotransmitters are the primary biochemical messengers of the central and peripheral nervous systems. As electrochemical signaling molecules, neurotransmitters are essential for proper brain function, including the perception, behavior, motor control, cognitive behavior and emotional states of an organism. They affect and adjust the muscle tone and heart rate, and regulate learning, sleeping, memory, consciousness, mood and appetite [138]. These neurotransmitters are essential for human health and any imbalance in their activities can cause serious mental disorders.
There are more than 100 known neurotransmitter molecules [139]. Neurotransmitters have been classified as either excitatory or inhibitory based on their behavior between two neurons and as amino acids, peptides, monoamines, gas transmitters, trace amines or purines according to their chemical structure. Those with a single amino functional group are classified as monoamine neurotransmitters (Figure 3) [140] and include serotonin (5-hydroxytryptamine, 5-HT) and catecholamines: dopamine (DA), epinephrine (EP) and norepinephrine (NP).
Changes in the concentrations of neurotransmitters in the central nervous system have been associated with many mental and physical disorders, including Parkinson’s disease, Alzheimer’s disease, schizophrenia, glaucoma, Huntington’s disease, epilepsy, arrhythmias, thyroid hormone deficiency, congestive heart failure, sudden infant death syndrome, addiction, Tourette’s syndrome, depression and anxiety [141,142,143,144,145,146,147]. It is essential to monitor the concentrations of monoamine neurotransmitters when studying and diagnosing these disorders.
Hence, the detection of neurotransmitters and measurement of their activity in biological samples is of fundamental importance in both basic neurophysiology and clinical neurology research. It is vital in the diagnosis and treatment of brain diseases.
Electrochemical techniques have been identified as simple, inexpensive and less time-consuming. Electrochemical analysis is based on the redox behaviors of monoamine neurotransmitters, as well as of their metabolites. Various electroanalytical techniques have been employed to detect and monitor neurotransmitters, such as cyclic voltammetry, differential pulse voltammetry, square wave voltammetry and amperometry. These electrochemical sensing strategies have the potential to achieve the rapid, sensitive, selective, and low-cost detection of biomolecules relevant to clinical diagnosis and treatment monitoring.

4.1. Determination of Dopamine

Dopamine (3, 4-dihydroxyphenyl ethylamine or [2,(3,4-dihydroxyphenyl) ethylamine]) exists in the brain and central nervous system of mammals. It is both an inhibitory and an excitatory neurotransmitter and it is partially responsible for motor activity, as well as the physiological regulation of behavior, mood, memory, perception and learning [148]. DA regulates cardiovascular, hormonal, renal and gastrointestinal functions, among others [149,150,151,152,153]. Disruptions to the DA balance in the human body have been associated with conditions such as Parkinson’s disease, dementia, epilepsy, schizophrenia and melancholia [154]. Increased dopaminergic activity may result in perceptual errors, like hallucinations, and is a characteristic of certain psychiatric disorders, such as schizophrenia. On the other hand, a reduction in dopaminergic neurons is often seen in certain neurological and motor illnesses, such as Parkinson’s disease. DA is essential for processing rewards, regulating emotional states, and influencing human motivation and goal-directed behavior [155]. Therefore, the detection and quantification of DA are significant for disease diagnosis.
Table 1 summarizes the electrochemical studies that have addressed the determination of DA using MPc-modified electrodes, as well as the performance characteristics of the developed methods. As can be seen, more than half of them have used a glassy carbon electrode (GCE) [13,15,36,38,58,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177] as a substrate for surface modification. However, carbon paste [47,178,179,180,181,182], indium tin oxide [18,183,184,185,186,187,188] and gold [189,190,191,192] electrodes also have unique properties that make them useful for DA detection.
One challenge in DA quantitative determination is its low concentration in biological samples, such as serum, urine and plasma, so the analytical methods developed must be sensitive. The synergistic effect of modifying electrode surfaces with MPcs and different types of nanomaterials has led to numerous composite sensors with different catalytic properties compared with unmodified electrodes. At the same time, the modified electrodes have significantly increased the peak current of DA redox reactions, allowing for lower detection limits and a greater linearity range.
The main challenge of all the investigations remains determining the DA in the presence of other biologically important molecules, such as AA and UA, which are compounds that coexist at high concentrations in biological matrices.
It was possible to determine DA and AA in the same sample due to the electrocatalytic oxidation of these compounds using CPEs modified with FeTSPc [179] and nanosized CoPc particles [180]. In the first case, the concentrations of DA and AA could be determined from the shift of the half-wave potential as a function of the concentration ratio of the two compounds. In the other case, the anodic peak potentials of DA and AA were separated with good sensitivity in the presence of CTAB. The simultaneous and sensitive electrochemical determinations of DA and AA were also possible with MWCNT-decorated CoPc-modified GCE [166] and with NiPc-modified ceramic matrices prepared by the sol–gel method [194]. The modified electrodes were stable, sensitive and reproducible for the micromolar detection of AA and DA.
GCEs were also used as substrates for modification to simultaneously determine DA and UA. Electrode surface properties were improved by electropolymerizing MPcs containing thiazole moieties (Mn, Zn) [165], drop-covering CoTfurNH2Pc [167], and electropolymerizing or electrodepositing carbazole-linked ZnPc and CoPc [172].
There are also electrochemical methods that use MPc-modified electrodes and can determine DA, AA and UA simultaneously. PdTAPc immobilized on the GCE surface through self-assembled monolayer technique, as well as the larger surface area with an enriched active site of the MWCNTs, induced the faster electron transfer during the electrochemical sensing of AA. The MWCNT-dispersed PdTAPc-modified electrode was used for the simultaneous determination of DA, AA and UA in urine samples [163]. A simple and green method was used to fabricate CoPc embedded with ganciclovir units to modify the GCE surface. Using the modified electrode, AA was determined from commercial tablets, DA from dopamine hydrochloride injection and UA in human urine samples [58]. Chen et al. [168] described a pyrolytic method for the preparation of ultrafine Fe3C nanoparticles incorporated into N-doped graphitic carbon nanosheets, with the hybrid nanocomposite being placed on a GCE. The modified electrode exhibited increased peak currents and enhanced peak separations for AA, DA, UA and XA oxidation due to its distinctive porous configuration and cooperative effects between N, Fe and carbon capsules. Studies of simultaneous determination were also performed using a Cu-MAPA polymer-modified electrode with silver nanoparticles for AA, DA and UA. The modified electrode was shown to have good electrochemical catalytic activity for the electrooxidation of the species, enhancing the analytical signal and reducing the overpotential compared with studies on bare electrodes [170]. Another study investigated the sensor performances of piperidine-substituted CoPc and CuPc for the detection of DA, AA and UA. Non-peripheral CoPc exhibited a good linear range and low detection limit for the electrochemical determination of AA. Meanwhile, non-peripheral CuPc demonstrated a high sensitivity and a low detection limit, particularly for AA and UA [174].
There is considerable interest in developing electrodes for the electrochemical determination of DA and other important molecules, particularly neurotransmitters. At conventional electrodes, DA exhibits oxidation peak potentials that are very close to those of EP, NP and 5-HT. This results in overlapping voltammetric responses, which makes it difficult to detect them electrochemically. Oni and Nyokong [47] used CPEs containing FePc and [FeTSPc]4− to detect DA and 5-HT. They compared the catalytic activities of FePc and [FeTSPc]4− with those of CoPc, NiPc [CoTSPc]4− and [NiTSPc]4− complexes. The results showed that the CoPc and NiPc complexes exhibited less catalytic behavior toward detecting 5-HT and DA than the FePc complexes. The simultaneous determination of 5-HT and DA on FeTSPc/CPE revealed that these species did not significantly interact with each other. Moreover, AA did not interfere with the detection of DA or 5-HT.
The versatility of FePc to form distinct supramolecular arrangements in thin films was used to adjust the electro-oxidation of catecholamines. The production of thin films of FePc on ITO electrodes was achieved using both Langmuir–Schaefer and electrodeposition techniques [18]. Electrodes modified by electrodeposition exhibited two distinct oxidation peaks in mixtures of DA and its amino acid precursor, L-Dopa. The separation of oxidation peaks can be attributed to different interactions with the surface of the electrodeposited FePc film. Moreover, the higher oxidation currents observed at the modified electrodes suggest that the FePc molecules are arranged in a manner that favors electron transfer from the analyte to the electrode [18].

4.2. Determination of Epinephrine and Norepinephrine

Both EP (adrenaline) and NP (noradrenaline) are catecholamines that function as neurotransmitters that signal between nerve cells, as well as hormones that travel through the bloodstream [197]. These compounds can impact various physiological functions, including the heart rate, brain muscle activity, blood sugar levels and blood vessel circulation. Although it increases both the heart rate and blood pressure, EP primarily affects the heart and muscles, while NP has a greater impact on blood vessels and blood pressure regulation [198]. They both play a critical role in the body’s “fight-or-flight” response, but they have distinct clinical significances. EP is used in emergency situations, like anaphylaxis, cardiac arrest and to treat asthma [199], while NP is used for conditions requiring sustained vasopressor support, particularly in septic shock and critical hypotension [200].
The EP and NP structures differ only by a methyl group on the amine side chain (Figure 3). Because of this, they have very similar electro-oxidation potentials, making it difficult to distinguish one from the other when they are present in a binary mixture. Consequently, few studies have examined the simultaneous determination of EP and NP. Several methods have been developed using unmodified electrodes and different voltammetric techniques. These include carbon fiber microelectrodes and fast-scan cyclic voltammetry [201], GCEs and DPV combined with chemometric methods [202], printed carbon electrodes and SWCV [203], and PGEs and SWCV [197]. However, some studies also used modified electrodes. Examples include a carbon nanotube paste electrode modified with 2-(4-oxo-3-phenyl-3,4-dihydro-quinazolinyl)-N-phenyl-hydrazine carbothioamide [204], a MWCNT-modified edge-plane pyrolytic graphite electrode [205] and a glassy carbon electrode modified with CTAB-assisted SnO2 nanoparticles synthesized by microwave irradiation [206].
As shown in Table 2, MPcs were not effective as working electrode surface modifiers for the simultaneous determination of EP and NP. However, studies investigated the electrochemical behavior and quantitative determination of the two transmitters separately. Some of these were performed in an attempt to detect them in the presence of dopamine [189,190,191,192,193].
In this context, the combination of MWCNTs, metal oxides (Fe3O4, ZnO), nanoparticles, and phthalocyanines employed for GCE surface modification resulted in enhanced EP and NP oxidation signals compared with using a bare GCE [57]. The catalysis of EP was favored on MWCNT/Fe3O4/29H,31H-P/GCE, while MWCNT/ZnO/29H,31H-P/GCE exhibited the highest sensitivity for NP.
A series of studies [189,191,192] examined the covalent immobilization of thin films of CoTCPhOPc, CoOAClPc and FeOAClPc on PEA-grafted gold electrodes. The presence of carboxylic acid terminal groups on the modified gold electrodes was confirmed by negatively and positively charged redox probes, [Fe(CN)6]3−/4− and [Ru(NH3)6]2+/3+, respectively. Modified electrodes enabled the determinations of DA, EP and NP, as well as the screening of ascorbic acid [189,190,191,192,193,194,195].
It is known that carbon paste is a convenient matrix for incorporating chemical modifiers, so CPEs modified with FePc [208] and CoPc [209] have been proposed for the determination of EP in the presence of uric acid or ascorbic acid. Electrochemical investigations revealed the electrode’s efficient catalytic activity for the electro-oxidation of EP, improving the reversibility of the modified electrode response and decreasing its overpotential [208,209].
Miniaturized sensors were developed using CV to test screen-printed electrodes modified with ionic liquids for the detection of DA, EP and dobutamine in aqueous solutions. The ionic liquids played a dual role, acting both as a binder and a chemical modifier. Using CoTBuPc as an electron-conductive additive increased the electrochemical signals and lowered the detection limits [193].

4.3. Determination of Serotonin

Serotonin (5-HT, 5-hydroxytryptamine) is an inhibitory neurotransmitter that can also act as a neuromodulator, affecting appetite, learning, and mood and sleep regulation [209]. It also controls other processes, such as learning, memory, body temperature, sleep and appetite. Irregularities in its optimization in the nervous system can cause illnesses, such as liver regeneration, depression, anxiety, stress and psychosis [210]. Additionally, there is a connection between the decreased density of serotonergic receptors and aging and Alzheimer’s disease [211]. Disruptions in serotoninergic and noradrenergic systems are associated with some eating disorders, such as bulimia and anorexia nervosa [212].
As in the case of other neurotransmitters, problems encountered when determining 5-HT levels include the presence of other electroactive biomolecules and the low concentration of 5-HT in biological samples. Additionally, 5-HT oxidation products can adsorb onto the surface of conventional electrodes. A literature review [213] revealed that although several methods have been developed for the electrochemical determination of 5-HT, only a few address the use of MPcs for the surface modification of working electrodes (Table 3).
Among the studied metallic phthalocyanines, NiTsPc is the most promising metallic phthalocyanine for 5-HT electroanalysis. Compared with unsubstituted NiPc, the sulfonated groups of NiTsPc decrease the electronic density of the metal center and facilitate Ni oxidation [217]. Layer-by-layer films containing alternating layers of CuNPs and NiTsPc in indium-doped tin oxide electrodes were used to produce a composite material with high electrochemical stability and sensitivity for detecting 5-HT [217]. De Irazu et al.’s study [214] revealed that carbon fiber microelectrodes modified with NiTsPc and Nafion coatings exhibited electrochemical activity for 5-HT oxidation. The Nafion layer eliminates interference from ascorbic acid. Other catecholamines (EP and DA) are oxidized at different potentials and do not interfere with the 5-HT determination.
A large-scale study examined the ability of several dot microsensors based on carbon materials (graphite, graphene and carbon nanopowder) to detect 5-HT in urine samples [216]. The plain paste obtained from each of these materials and paraffin oil was modified with TiO2, Pc, Fe(III)Pc and Fe(II)Pc. The authors demonstrated that G-Fe(II)Pc produced the most stable and sensitive results. However, the most consistent and lowest limits of detection for 5-HT were recorded using G-Fe(III)Pc- or GR-Fe(III)Pc-modified microsensors.
One fascinating topic in the field of electrochemical sensor construction is that of biosensors, in which enzymes are immobilized on or inside the supporting substrate and serve as recognition elements. A biosensor was fabricated for the detection and quantification of 5-HT using carbon nanopowder as the substrate, tyrosinase as the biocatalyst and CoPc as the electron mediator. Tyrosinase was immobilized on the carbon nanopowder using the drop-and-dry method, followed by cross-linking with glutaraldehyde [215]. The determination of 5-HT in walnut samples was performed using amperometry, yielding good results.

5. Conclusions and Future Prospects

This review surveys several approaches adopted for the selective quantification of monoamine neurotransmitters using specific MPcs. We describe several possible applications of MPcs-modified electrodes, emphasizing the remarkable properties of MPcs and carbon nanomaterials that create a host of application possibilities in sensor design. The interest in this field arises from the versatility of MPcs and carbon materials and the ability to generate novel properties and applications. Future efforts will need to be directed toward increasing the selectivity and sensitivity of MPc-modified electrodes by preventing the non-specific adsorption of molecules onto the electrode surface. Further improvements may be expected by expanding the range of modifying molecules that can be attached to the electrode surface; so far, enzymes and nucleic acids have been mostly employed for this purpose. However, the development of a sensing platform with high sensitivity and selectivity is challenging, and it has been found to be a bottleneck step in the analysis of neurotransmitters.

Author Contributions

Conceptualization, writing review and editing, supervision, A.A.C.; validation, resources, writing-original draft preparation, M.B.; methodology, investigation, D.E.P. methodology, investigation, D.C.Ș. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
29H,31H-Pc29H,31H-Phthalocyanine
3N-CoPcnon-peripheral cobalt phthalocyanine
3N-CuPcnon-peripheral copper phthalocyanine
5-HTserotonin
ABSacetate buffer solution
AETaminoethanethiol
AmGQDsaminated graphene quantum dots
AGCEactivated glassy carbon electrode
AgNPssilver nanoparticles
Ampamperometry
AAascorbic acid
BRBBritton–Robinson buffer
CAchronoamperometry
Carcarbazole
CCEcarbon ceramic electrode
CFEcarbon fiber electrode
Clicked-α-CoPc-flav3clicked film of an asymmetric A3B (A = 3-oxyflavone, B = α-(ethynyl)benzyl alcohol) CoPc complex
CNPcarbon nanoparticles
CoOCAPccobalt(II) octa acyl chloride phthalocyanine
CoPccobalt phthalocyanine
CoTAPccobalt tetra-amino phthalocyanine
CoTBuPcCo(III) tetrakis-(tert-butyl)-phthalocyanine
CoTCPhOPccobalt(II) tetra-(3-carboxyphenoxy) phthalocyanine
CoTfurNH2Pccobalt (II) tetra furfurylamide phthalocyanine
CoTGPcganciclovir-cobalt (II) phthalocyanine
CoTMBANAPctetra8[(E)(4methoxybenzylidene)amino] naphthalene1amine cobalt (II) phthalocyanine
CoTNBAPccobalt (II) tetra[β-N-(4-nitrophenyl) benzamide] phthalocyanine
CPEcarbon paste electrode
CTABcetyltrimethylammonium bromide
Cu-MAPAcopper monoamino-phthalocyanine-acrylate
CuNPscopper nanoparticles
CuTsPccopper(II) tetrasulfophthalocyanine
CVcyclic voltammetry
DAdopamine
Dbcationic 1,4-diazoniabicyclo [2.2.2]octane group of silsesquioxane
DMZdimetridazole
DPVdifferential pulse voltammetry
DPSVdifferential pulse stripping voltammetry
DS01antimicrobial peptide dermaseptin 01
EDelectrodeposition
EPepinephrine
ERGOelectrochemically reduced graphene oxide
FeOCAPciron octa carboxylic acid phthalocyanine
FePciron phthalocyanine
FeTAPciron(II) tetraaminophthalocyanine
FeTBImPciron tetrabenzimidazole phthalocyanine
FeTsPciron(II) tetrasulfonated phthalocyanine
FIAflow injection analysis
f-MWCNTsfunctionalized multi-walled carbon nanotubes
Ggraphite
GCEglassy carbon electrode
GOgraphene oxide
GPEgraphite paste carbon
Grgraphene
GQDsgraphene quantum dots
IPAisophthalic acid
ITOEindium tin oxide electrode
L-dopalevodopa
LSVlinear scan voltammetry
MPCsmetallo-phthalocyanines
MnPcmanganese phthalocyanine
Mn-TPPmanganese tetraphenylporphyrin
MWCNTsmultiwalled carbon nanotubes
Na+MMTsodium montmorillonite clay
N-Gnitrogen-doped graphene
NGCSsN-doped graphitic carbon nanosheets
NGQDsnitrogen-doped graphene quantum dots
NiTAPcnickel(II) tetraaminophthalocyanine
NiTsPcnickel tetrasulfonated phthalocyanine
NPnorepinephrine
OSWVOsteryoung square wave voltammetry
P8BTpoly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzothiadia-zol-4,8-diyl)]
PAHspoly allylamine hydrocarbons
PAMAMpoly (amidoamine)
PANIpolyaniline
PARparacetamol
Pdotspolymer dots
PECphotoelectrochemical cell
PBSphosphate buffer solution
PdTAPcpalladium(II) tetraaminophthalocyanine
PEAphenylethylamine
PEIpolyelectrolyte
PGEpencil graphite electrode
PPOpolyphenol oxidase
rGOreduced graphene oxide
SAMself-assembled monolayer
SPCEscreen-printed carbon electrode
SPGEscreen-printed graphite electrode
SWCNTssingle-wall carbon nanotubes
SWVsquare wave voltammetry
TRIStris[hydroxymethyl]aminomethane hydrochloride
UAuric acid
XOxanthine
ZnONPszinc oxide nanoparticles
ZnPczinc phthalocyanine
ZnTPEBIPczinc tetra [4-{2-[(E)-2-phenylethenyl]-1H-benzimidazol-1-yl}]phthalocyanine

References

  1. Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; John Wiley & Sons Inc.: New York, NY, USA, 2001. [Google Scholar]
  2. Ciucu, A.A. Chemically modified electrodes in biosensing. J. Biosens. Bioelectron. 2014, 5, 3. [Google Scholar]
  3. Elliot, C.M.; Murray, R.W. Chemically modified carbon electrodes. Anal. Chem. 1976, 48, 1247–1254. [Google Scholar] [CrossRef]
  4. Demir, E.; Silah, H.; Uslu, B. Phthalocyanine modified electrodes in electrochemical analysis. Crit. Rev. Anal. Chem. 2020, 52, 425–461. [Google Scholar] [CrossRef] [PubMed]
  5. Dahlen, M.A. The phthalocyanines a new class of synthetic pigments and dyes. Ind. Eng. Chem. 1939, 31, 839–847. [Google Scholar] [CrossRef]
  6. Velloso, N.V.; Muehlmann, L.A.; Longo, J.P.F.; da Silva, J.R.; Zancanela, D.C.; Tedesco, A.C.; de Azevedo, R.B. Aluminum-phthalocyanine chloride-based photodynamic therapy inhibits PI3K/Akt/Mtor pathway in oral squamous cell carcinoma cells in vitro. Chemotherapy 2012, 1, 107. [Google Scholar]
  7. Basova, T.; Plyashkevich, V.; Hassan, A.; Gürek, A.G.; Gümüş, G.; Ahsen, V. Phthalocyanine films as active layers of optical sensors for pentachlorophenol detection. Sens. Actuat. B Chem. 2009, 139, 557–562. [Google Scholar] [CrossRef]
  8. Ao, R.; Kummert, L.; Haarer, D. Present limits of data storage using dye molecules in solid matrices. Adv. Mater. 1995, 5, 495–499. [Google Scholar] [CrossRef]
  9. Ng, D.K.P.; Yeung, Y.O.; Chan, W.K.; Yu, S.C. Columnar liquid crystals based on 2,3-naphthalocyanine core. Tet. Lett. 1997, 38, 6701–6704. [Google Scholar] [CrossRef]
  10. Wörhle, D.; Meissener, D. Organic solar cells. Adv. Mater. 1991, 3, 129–138. [Google Scholar]
  11. Jahnke, H.; Schonborn, M.; Zimmermann, G. Organic dyestuffs as catalysts for fuel cells. Top. Curr. Chem. 1976, 61, 133–181. [Google Scholar]
  12. Iwamoto, M. Nanometric electrostatic interfacial phenomena in organic semiconducting thin films. J. Mater. Chem. 2000, 10, 99–106. [Google Scholar] [CrossRef]
  13. Sajjan, V.A.; Mohammed, I.; Nemakal, M.; Aralekallu, S.; Kumar, H.K.R.; Swamy, S.; Sannegowda, L.K. Synthesis and electropolymerization of cobalt tetraaminebenzamide phthalocyanine macrocycle for the amperometric sensing of dopamine. J. Electroanal. Chem. 2019, 838, 33–40. [Google Scholar] [CrossRef]
  14. Zeng, Z.; Fang, X.; Miao, W.; Liu, Y.; Maiyalagan, T.; Mao, S. Electrochemically sensing of trichloroacetic acid with Iron(II) phthalocyanine and Zn-based metal organic framework nanocomposites. ACS Sens. 2019, 4, 1934–1941. [Google Scholar] [CrossRef]
  15. Diab, N.; Morales, D.M.; Andronescu, C.; Masoud, M.; Schuhmann, W. A sensitive and selective graphene/cobalt tetrasulfonated phthalocyanine sensor for detection of dopamine. Sens. Actuat. B Chem. 2019, 285, 17–23. [Google Scholar] [CrossRef]
  16. Yuan, B.; Wang, H.; Cai, J.; Peng, Y.; Niu, Y.; Chen, H.; Bai, L.; Zhang, S.; Jin, J.; Liu, L.; et al. A novel oxidation-reduction method for highly selective detection of cysteine over reduced glutathione based on synergistic effect of fully fluorinated cobalt phthalocyanine and ordered mesoporous carbon. Sens. Actuat. B Chem. 2019, 288, 180–187. [Google Scholar] [CrossRef]
  17. Jilani, B.S.; Mruthyunjayachari, C.D.; Malathesh, P.; Mounesh, M.N.; Sharakumar, T.M.; Reddy, V.K.R. Electrochemical sensing based MWCNT-cobalt tetra substituted sorbaamide phthalocyanine onto the glassy carbon electrode towards the determination of 2-amino phenol: A voltammetric study. Sens. Actuat. B Chem. 2019, 301, 127078. [Google Scholar] [CrossRef]
  18. Martin, C.S.; Alessio, P.; Crespilho, F.N.; Brett, C.M.A.; Constantino, C.J.L. Influence of the supramolecular arrangement of iron phthalocyanine thin films on catecholamine oxidation. J. Electroanal. Chem. 2019, 836, 7–15. [Google Scholar] [CrossRef]
  19. Ciucu, A.; Negulescu, C.; Baldwin, R.P. Detection of pesticides using an amperometric biosensor based on ferrophthalocyanine chemically modified carbon paste electrode and immobilized bi-enzymatic system. Biosens. Bioelectron. 2003, 18, 293–300. [Google Scholar] [CrossRef]
  20. Wang, M.; Zhu, L.; Zhang, S.; Lou, Y.; Zhao, S.; Tan, Q.; He, L.; Du, M. A copper(II) phthalocyanine-based metallo-covalent organic framework decorated with silver nanoparticle for sensitively detecting nitric oxide released from cancer cells. Sens. Actuat. B Chem. 2021, 338, 129826. [Google Scholar] [CrossRef]
  21. Xu, H.; Xiao, J.; Liu, B.; Griveau, S.; Bedioui, F. Enhanced electrochemical sensing of thiols based on cobalt phthalocyanine immobilized on nitrogen-doped graphene. Biosens. Bioelectron. 2015, 66, 438–444. [Google Scholar] [CrossRef]
  22. Mpeta, L.S.; Sen, P.; Nyokong, T. Development of manganese phthalocyanine decorated with silver nanoparticles nanocomposite for improved electrocatalytic oxidation of hydrazine. J. Electroanal. Chem. 2020, 866, 114173. [Google Scholar] [CrossRef]
  23. Yin, H.-S.; Zhou, Y.-L.; Ai, S.-Y. Preparation and characteristic of cobalt phthalocyanine modified carbon paste electrode for bisphenol A detection. J. Electroanal. Chem. 2009, 626, 80–88. [Google Scholar] [CrossRef]
  24. Myers, J.F.; Canham, R.G.W.; Lever, A.B.P. Higher oxidation level phthalocyanine complexes of chromium, iron, cobalt and zinc. Phthalocyanine radical species. Inorg. Chem. 1975, 14, 461–468. [Google Scholar] [CrossRef]
  25. Clack, D.W.; Hush, N.S.; Woosley, I.S. Reduction potentials of some metal phthalocyanines. Inorg. Chim. Acta 1976, 19, 129–132. [Google Scholar] [CrossRef]
  26. Louati, A.; Meray, M.E.I.; Andre, J.J.; Simon, J.; Kadish, K.M.; Gross, M.; Giraurdeau, A. Electrochemical reduction of new, good electron acceptors: The metallooctacyanophthalocyanines. Inorg. Chem. 1985, 24, 1175–1179. [Google Scholar] [CrossRef]
  27. Lever, A.B.P.; Pickens, S.R.; Minor, P.C.; Licoccia, L.; Ramaswamy, B.S.; Magnell, K. Charge-transfer spectra of metallophthalocyanines: Correlation with electrode potentials. J. Am. Chem. Soc. 1981, 103, 6800–6806. [Google Scholar] [CrossRef]
  28. Manassen, J. Metal complexes of porphirin like compounds as heterogeneous catalysts. Catal. Rev. Sci. Eng. 1974, 9, 223–243. [Google Scholar] [CrossRef]
  29. Santos, L.M.; Baldwin, R.P. Electrocatalytic response of cobalt phthalocyanine chemically modified electrodes toward oxalic acid and alpha-keto acids. Anal. Chem. 1986, 58, 848–852. [Google Scholar] [CrossRef]
  30. Ozoemena, K.I.; Nyokong, T. Novel amperometric glucose biosensor based on an ether-linked cobalt(II) phthalocyanine–cobalt(II) tetraphenylporphyrin pentamer as a redox mediator. Electrochim. Acta 2006, 51, 5131–5136. [Google Scholar] [CrossRef]
  31. Ozoemena, K.I.; Zhao, Z.; Nyokong, T. Immobilized cobalt(II) phthalocyanine–cobalt(II) porphyrin pentamer at a glassy carbon electrode: Applications to efficient amperometric sensing of hydrogen peroxide in neutral and basic media. Electrochem. Commun. 2005, 7, 679–684. [Google Scholar] [CrossRef]
  32. Geraldo, D.A.; Togo, C.A.; Limson, J.; Nyokong, T. Electrooxidation of hydrazine catalyzed by noncovalently functionalized single-walled carbon nanotubes with CoPc. Electrochim. Acta 2008, 53, 8051–8057. [Google Scholar] [CrossRef]
  33. Sehlotho, N.; Griveau, S.; Ruille, N.; Boujtita, M.; Nyokong, T.; Bedioui, F. Electro-catalyzed oxidation of reduced glutathione and 2-mercaptoethanol by cobalt phthalocyanine-containing screen printed graphite electrodes. Mater. Sci. Eng. C 2008, 28, 606–612. [Google Scholar] [CrossRef]
  34. Halbert, M.K.; Baldwin, R.P. Electrocatalytic and analytical response of cobalt phthalocyanine containing carbon paste electrodes toward sulfhydryl compounds. Anal. Chem. 1985, 57, 591–595. [Google Scholar] [CrossRef]
  35. Zhang, J.; Tse, Y.-H.; Pietro, W.J.; Lever, A.B.P. Electrocatalytic activity of N,N′,N″,N‴-tetramethyl-tetra-3,4-pyridoporphyrazinocobalt(II) adsorbed on a graphite electrode towards the oxidation of hydrazine and hydroxylamine. J. Electroanal. Chem. 1996, 406, 203–211. [Google Scholar] [CrossRef]
  36. Moraes, F.C.; Cabral, M.F.; Machado, S.A.S.; Mascaro, L.H. Electrocatalytic behavior of glassy carbon electrodes modified with multiwalled carbon nanotubes and cobalt phthalocyanine for selective analysis of dopamine in presence of ascorbic acid. Electroanalysis 2008, 20, 851–857. [Google Scholar] [CrossRef]
  37. Goux, A.; Bedioui, F.; Robbiola, L.; Pontie, M. Nickel tetraaminophthalocyanine based films for the electrocatalytic activation of dopamine. Electroanalysis 2003, 15, 969–974. [Google Scholar] [CrossRef]
  38. Kang, T.F.; Shen, G.L.; Yu, R.Q. Voltammetric behaviour of dopamine at nickel phthalocyanine polymer modified electrodes and analytical applications. Anal. Chim. Acta 1997, 354, 343–349. [Google Scholar] [CrossRef]
  39. Ureta-Zañartu, M.S.; Berrios, C.; Pavez, J.; Zagal, J.; Gutierrez, C.; Marco, J.F. Electrooxidation of 2-chlorophenol on polyNiTSPc-modified glassy carbon electrodes. J. Electroanal. Chem. 2003, 553, 147–156. [Google Scholar] [CrossRef]
  40. Obirai, J.; Bedioui, F.; Nyokong, T. Electro-oxidation of phenol and its derivatives on poly-Ni(OH)TPhPyPc modified vitreous carbon electrodes. J. Electroanal. Chem. 2005, 576, 323–332. [Google Scholar] [CrossRef]
  41. Jiang, R.; Dong, S. Study on the electrocatalytic reduction of H2O2 at iron protoporphyrin modified electrode with a rapid rotation-scan method. Electrochim. Acta 1990, 35, 1227–1232. [Google Scholar] [CrossRef]
  42. Elliot, C.M.; Marrese, C.A. Catalytic reduction of some alkyl halides by iron porphyrin modified carbon electrodes. J. Electroanal. Chem. 1981, 119, 395–401. [Google Scholar] [CrossRef]
  43. Wang, Z.; Pang, D. Electrocatalysis of metalloporphyrins: Part 9. Catalytic electroreduction of cystine using water-soluble cobalt porphyrins. J. Electroanal. Chem. 1990, 283, 349–358. [Google Scholar] [CrossRef]
  44. Sorokin, A.; Meunier, B. Efficient H2O2 oxidation of chlorinated phenols catalysed by supported iron phthalocyanines. J. Chem. Soc. Chem. Commun. 1994, 15, 1799–1800. [Google Scholar] [CrossRef]
  45. Hadasch, A.; Sorokin, A.; Rabion, A.; Meunier, B. Sequential addition of H2O2, pH and solvent effects as key factors in the oxidation of 2,4,6-trichlorophenol catalyzed by iron tetrasulfophthalocyanine. New J. Chem. 1998, 22, 45–51. [Google Scholar] [CrossRef]
  46. Sanchez, M.; Hadasch, A.; Fell, R.T.; Meunier, B. Key role of the phosphate buffer in the H2O2 oxidation of aromatic pollutants catalyzed by iron tetrasulfophthalocyanine. J. Catal. 2001, 202, 177–186. [Google Scholar] [CrossRef]
  47. Oni, J.; Nyokong, T. Simultaneous voltammetric determination of dopamine and serotonin on carbon paste electrodes modified with iron(II) phthalocyanine complexes. Anal. Chim. Acta 2001, 432, 9–21. [Google Scholar] [CrossRef]
  48. Zagal, J.H. Metallophthalocyanines as catalysts in electrochemical reactions. Coord. Chem. Rev. 1992, 119, 89–136. [Google Scholar] [CrossRef]
  49. Grootboom, N.; Nyokong, T. Electrooxidation of cresols on carbon electrodes modified with phthalocyaninato and octabutoxyphthalocyaninato cobalt(II) complexes. Anal. Chim. Acta 2001, 432, 49–57. [Google Scholar] [CrossRef]
  50. Caro, C.A.; Bedioui, F.; Páez, M.A.; Cárdenas-Jirón, G.I.; Zagal, J.H. Experimental and theoretical study of the activity of substituted metallophthalocyanines for nitrite electro-oxidation. J. Electrochem. Soc. 2004, 151, E32. [Google Scholar] [CrossRef]
  51. Agboola, B.O. Catalytic Activities of Metallophthalocyanines Towards Detection and Transformation of Pollutants. Ph.D. Thesis, Rhodes University, Makhanda, South Africa, 2007. Available online: https://commons.ru.ac.za/vital/access/services/Download/vital:4427/SOURCEPDF (accessed on 15 March 2025).
  52. Sajid, M.; Nazal, M.K.; Mansha, M.; Alsharaa, A.; Jillani, S.M.S.; Basheer, C. Chemically modified electrodes for electrochemical detection of dopamine in the presence of uric acid and ascorbic acid: A review. Trends Anal. Chem. 2016, 76, 15–29. [Google Scholar] [CrossRef]
  53. Fan, F.R.; Faulkner, L.R. Phthalocyanine thin films as semiconductor electrodes. J. Am. Chem. Soc. 1979, 101, 4779–4787. [Google Scholar] [CrossRef]
  54. Yang, W.; Zhang, R.; Luo, K.; Zhang, W.; Zhao, J. Electrocatalytic performances of multi-walled carbon nanotubes chemically modified by metal phthalocyanines in Li/SOCl2 batteries. RSC Adv. 2016, 6, 75632–75639. [Google Scholar] [CrossRef]
  55. Foster, C.W.; Pillay, J.; Metters, J.P.; Banks, C.E. Cobalt phthalocyanine modified electrodes utilised in electroanalysis: Nano-structured modified electrodes vs. bulk modified screen-printed electrodes. Sensors 2014, 14, 21905–21922. [Google Scholar] [CrossRef] [PubMed]
  56. Griveau, S.; Gulppi, M.; Pavez, J.; Zagal, J.H.; Bedioui, F. Cobalt phthalocyanine-based molecular materials for the electrocatalysis and electroanalysis of 2-mercaptoethanol, 2-mercaptoethanesulfonic acid, reduced glutathione and L-cysteine. Electroanalysis 2003, 15, 779–785. [Google Scholar] [CrossRef]
  57. Mphuthi, N.G.; Adekunle, A.S.; Ebenso, E.E. Electrocatalytic oxidation of epinephrine and norepinephrine at metal oxide doped phthalocyanine/MWCNT Composite Sensor. Sci. Rep. 2016, 6, 26938. [Google Scholar] [CrossRef]
  58. Mounesh; Malathesh, P.; Kumara, N.Y.P.; Jilani, B.S.; Mruthyunjayachari, C.D.; Reddy, K.R.V. Synthesis and characterization of tetra-ganciclovir cobalt (II) phthalocyanine for electroanalytical applications of AA/DA/UA. Heliyon 2019, 5, e01946. [Google Scholar] [CrossRef]
  59. Lei, P.; Zhou, Y.; Zhu, R.; Liu, Y.; Dong, C.; Shuang, S. Facile synthesis of iron phthalocyanine functionalized n, b–doped reduced graphene oxide nanocomposites and sensitive electrochemical detection for glutathione. Sens. Actuat. B Chem. 2019, 297, 126756. [Google Scholar] [CrossRef]
  60. Porto, L.S.; da Silva, D.N.; Silva, M.C.; Pereira, A.C. Electrochemical sensor based on multi-walled carbon nanotubes and cobalt phthalocyanine composite for pyridoxine determination. Electroanalysis 2019, 31, 820–828. [Google Scholar] [CrossRef]
  61. Pari, M.; Ramareddy, K.; Reddy, V. Electrochemical investigation of uric acid using MWCNTs-decorated novel substituted cobalt (II) phthalocyanine modified GCE. Anal. Bioanal. Electrochem. 2019, 11, 1383–1397. [Google Scholar]
  62. Ozoemena, K.I. Anodic oxidation and amperometric sensing of hydrazine at a glassy carbon electrode modified with cobalt (II) phthalocyanine-cobalt (II) tetraphenylporphyrin (Copc-(Cotpp)(4)) supramolecular complex. Sensors 2006, 6, 874–891. [Google Scholar] [CrossRef]
  63. Lopes, I.C.; De Souza, D.; Machado, S.A.S.; Tanaka, A.A. Voltammetric detection of paraquat pesticide on a phthalocyanine-based pyrolitic graphite electrode. Anal. Bioanal. Chem. 2007, 388, 1907–1914. [Google Scholar] [CrossRef] [PubMed]
  64. Ozoemena, K.I.; Stefan, R.I.; Nyokong, T. Determination of 2’, 3-dideoxyinosine using iron(II) phthalocyanine modified carbon paste electrode. Anal. Lett. 2004, 37, 2641–2648. [Google Scholar] [CrossRef]
  65. Liu, S.; Zeng, T.H.; Hofmann, M.; Burcombe, E.; Wei, J.; Jiang, R.; Kong, J.; Chen, Y. Antibacterial activity of graphite, graphite oxide, graphene oxide, and reduced graphene oxide: Membrane and oxidative stress. ACS Nano 2011, 5, 6971–6980. [Google Scholar] [CrossRef] [PubMed]
  66. Maschmann, M.R.; Amama, P.B.; Goyal, A.; Iqbal, Z.; Fisher, T.S. Freestanding vertically oriented single-walled carbon nanotubes synthesized using microwave plasma-enhanced CVD. Carbon 2006, 44, 2758–2763. [Google Scholar] [CrossRef]
  67. Wang, G.; Wang, B.; Park, J.; Yang, J.; Shen, X.; Yao, J. Synthesis of enhanced hydrophilic and hydrophobic graphene oxide nanosheets by a solvothermal method. Carbon 2009, 47, 68–72. [Google Scholar] [CrossRef]
  68. Takehara, H.; Fujiwara, M.; Arikawa, M.; Diener, M.D.; Alford, J.M. Experimental study of industrial scale fullerene production by combustion synthesis. Carbon 2005, 43, 311–319. [Google Scholar] [CrossRef]
  69. Iijima, S. Helical microtubules of graphitic carbon. Nature 1991, 354, 56–58. [Google Scholar] [CrossRef]
  70. Rivas, G.A.; Rubianes, M.D.; Rodríguez, M.C.; Ferreyra, N.F.; Luque, G.L.; Pedano, M.L.; Miscoria, S.A.; Parrado, C. Carbon nanotubes for electrochemical biosensing. Talanta 2007, 74, 291–307. [Google Scholar] [CrossRef]
  71. Wu, K.; Fei, J.; Hu, S. Simultaneous determination of dopamine and serotonin on a glassy carbon electrode coated with a film of carbon nanotubes. Anal. Biochem. 2003, 318, 100–106. [Google Scholar] [CrossRef]
  72. Ajayan, P.M. Nanotubes from carbon. Chem. Rev. 1999, 99, 1787–1800. [Google Scholar] [CrossRef]
  73. Gullapalli, S.; Wong, M.S. Nanotechnology: A guide to nano-objects. Chem. Engin. Prog. 2011, 107, 28–32. [Google Scholar]
  74. Merkoçi, A.; Pumera, M.; Llopis, X.; Pérez, B.; del Valle, M.; Alegret, S. New materials for electrochemical sensing VI: Carbon nanotubes. Trends Anal. Chem. 2005, 24, 826–838. [Google Scholar] [CrossRef]
  75. Yu, M.F.; Lourie, O.; Dyer, M.J.; Moloni, K.; Kelly, T.F.; Rouff, R.S. Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load. Science 2000, 287, 637–640. [Google Scholar] [CrossRef]
  76. Baughman, R.H.; Zakhidov, A.; de Heer, W.A. Carbon nanotubes—The route toward applications. Science 2002, 297, 787–792. [Google Scholar] [CrossRef]
  77. Nugent, J.M.; Santhanam, K.S.V.; Rubio, A.; Ajayan, P.M. Fast electron transfer kinetics on multiwalled carbon nanotube microbundle electrodes. Nano Lett. 2001, 1, 87–91. [Google Scholar] [CrossRef]
  78. Wang, J. Carbon-nanotube based electrochemical biosensors: A review. Electroanalysis 2005, 17, 7–14. [Google Scholar] [CrossRef]
  79. Luo, H.; Shi, Z.; Li, N.; Gu, Z.; Zhuang, Q. Investigation of the electrochemical and electrocatalytic behavior of single-wall carbon nanotube film on a glassy carbon electrode. Anal. Chem. 2001, 73, 915–920. [Google Scholar] [CrossRef]
  80. Wang, J.; Li, M.; Shi, Z.; Li, N.; Gu, Z. Direct Electrochemistry of cytochrome c at a glassy carbon electrode modified with single-wall carbon nanotubes. Anal. Chem. 2002, 74, 1993–1997. [Google Scholar] [CrossRef]
  81. Musameh, M.; Wang, J.; Merkoçi, A.; Lin, Y. Low-potential stable NADH detection at carbon-nanotube-modified glassy carbon electrodes. Electrochem. Comm. 2002, 4, 743–746. [Google Scholar] [CrossRef]
  82. Wu, F.H.; Zhao, G.-C.; Wei, X.-W. Electrocatalytic oxidation of nitric oxide at multi-walled carbon nanotubes modified electrode. Electrochem. Comm. 2002, 4, 690–694. [Google Scholar] [CrossRef]
  83. Guo, M.; Chen, J.; Li, J.; Tao, B.; Yao, S. Fabrication of polyaniline/carbon nanotube composite modified electrode and its electrocatalytic property to the reduction of nitrite. Anal. Chim. Acta 2005, 532, 71–77. [Google Scholar] [CrossRef]
  84. Ji, X.B.; Kadara, R.O.; Krussma, J.; Chen, Q.Y.; Banks, C.E. Understanding the physicoelectrochemical properties of carbon nanotubes: Current state of the art. Electroanalysis 2010, 22, 7–19. [Google Scholar] [CrossRef]
  85. Banks, C.E.; Moore, R.R.; Davies, T.J.; Compton, R.G. Investigation of modified basal plane pyrolytic graphite electrodes: Definitive evidence for the electrocatalytic properties of the ends of carbon nanotubes. Chem. Comm. 2004, 16, 1804–1805. [Google Scholar] [CrossRef] [PubMed]
  86. McCreery, L. Electroanalytical Chemistry; Bard, A.J., Ed.; Marcel Dekker: New York, NY, USA, 1991; Volume 17. [Google Scholar]
  87. Britto, P.J.; Santhanam, K.S.V.; Alonso, V.; Rubio, A.; Ajayan, P.M. Improved charge transfer at carbon nanotube electrodes. Adv. Mater. 1999, 11, 154–157. [Google Scholar] [CrossRef]
  88. Banks, C.E.; Davies, T.J.; Wildgoose, G.G.; Compton, R.G. Electrocatalysis at graphite and carbon nanotube modified electrodes: Edge-plane sites and tube ends are the reactive sites. Chem. Commun. 2005, 7, 829–841. [Google Scholar] [CrossRef]
  89. Agüí, L.; Yáñez-Sedeño, P.; Pingarrón, J.M. Role of carbon nanotubes in electroanalytical chemistry: A review. Anal. Chim. Acta 2008, 622, 11–47. [Google Scholar] [CrossRef]
  90. Chen, J.; Hamon, M.A.; Hu, H.; Chen, Y.; Rao, A.M.; Eklund, P.C.; Haddon, R.C. Solution properties of single-walled carbon nanotubes. Science 1998, 282, 95–98. [Google Scholar] [CrossRef]
  91. Tasis, D.; Tagmatarchis, N.; Georgakilas, V.; Prato, M. Soluble carbon nanotubes. Chem. Eur. J. 2003, 9, 4000–4008. [Google Scholar] [CrossRef]
  92. Islam, M.F.; Rojas, E.; Bergey, D.M.; Johnson, A.T.; Yodh, A.G. High weight fraction surfactant solubilization of single-wall carbon nanotubes in water. Nano Lett. 2003, 3, 269–273. [Google Scholar] [CrossRef]
  93. Star, A.; Stoddart, J.F.; Steuerman, D.; Diehl, M.; Boukai, A.; Wong, E.W.; Yang, X.; Chung, S.W.; Choi, H.; Heath, J.R. Preparation and properties of polymer-wrapped single-walled carbon nanotubes. Angew. Chem. Int. Ed. 2001, 40, 1721–1725. [Google Scholar] [CrossRef]
  94. Ramesh, S.; Ericson, L.M.; Davis, V.A.; Saini, R.K.; Pasquali, C.K.M.; Billups, W.E.; Adams, W.; Hauge, R.H.; Smalley, R.E. Dissolution of pristine single walled carbon nanotubes in superacids by direct protonation. J. Phys. Chem. B 2004, 108, 8794–9798. [Google Scholar] [CrossRef]
  95. Wang, J.; Musameh, M.; Lin, Y. Solubilization of carbon nanotubes by Nafion toward the preparation of amperometric biosensors. J. Am. Chem. Soc. 2003, 125, 2408–2409. [Google Scholar] [CrossRef]
  96. Hu, C.G.; Wang, W.L.; Liao, K.J.; Liu, G.B.; Wang, Y.T. Systematic investigation on the properties of carbon nanotube electrodes with different chemical treatments. J. Phys. Chem. Solids 2004, 65, 1731–1736. [Google Scholar] [CrossRef]
  97. Wang, Z.H.; Liang, Q.-L.; Wang, Y.-M.; Luo, G.-A. Carbon nanotube-intercalated graphite electrodes for simultaneous determination of dopamine and serotonin in the presence of ascorbic acid. J. Electroanal. Chem. 2003, 540, 129–134. [Google Scholar] [CrossRef]
  98. Valentini, F.; Orlanducci, S.; Terranova, M.L.; Amine, A.; Palleschi, G. Carbon nanotubes as electrode materials for the assembling of new electrochemical biosensors. Sens. Actuat. B Chem. 2004, 100, 117–125. [Google Scholar] [CrossRef]
  99. Jacobs, C.B.; Peairs, M.J.; Venton, B.J. Review: Carbon nanotube based electrochemical sensors for biomolecules. Anal. Chim. Acta 2010, 662, 105–127. [Google Scholar] [CrossRef]
  100. Luong, J.H.T.; Hrapovic, S.; Wang, D.; Bensebaa, F.; Simard, B. Solubilization of multiwall carbon nanotubes by 3-aminopropyltriethoxysilane towards the fabrication of electrochemical biosensors with promoted electron transfer. Electroanalysis 2004, 16, 132–139. [Google Scholar] [CrossRef]
  101. Hirsch, A. Functionalization of single-walled carbon nanotubes. Angew. Chemie Int. Ed. 2002, 41, 1853–1859. [Google Scholar] [CrossRef]
  102. Wong, S.S.; Joselevich, E.; Woolley, A.T.; Cheung, C.L.; Lieber, C.M. Covalently functionalized nanotubes as nanometre- sized probes in chemistry and biology. Nature 1998, 394, 52–55. [Google Scholar] [CrossRef]
  103. Dai, L.; He, P.; Li, S. Functionalized surfaces based on polymers and carbon nanotubes for some biomedical and optoelectronic applications. Nanotechnology 2003, 14, 1081–1097. [Google Scholar] [CrossRef]
  104. Merkoci, A. Carbon nanotubes in analytical sciences. Microchim. Acta 2006, 152, 157–174. [Google Scholar] [CrossRef]
  105. Banks, C.E.; Crossley, A.; Salter, C.; Wilkins, S.J.; Compton, R.G. Carbon nanotubes contain metal impurities which are responsible for the “electrocatalysis” seen at some nanotube-modified electrodes. Angew. Chem. Int. Ed. 2006, 45, 2533–2537. [Google Scholar] [CrossRef] [PubMed]
  106. Gooding, J.J. Nanostructuring electrodes with carbon nanotubes: A review on electrochemistry and applications for sensing. Electrochim. Acta 2005, 50, 3049–3060. [Google Scholar] [CrossRef]
  107. Katz, E.; Willner, I. Biomolecule-functionalized carbon nanotubes: Applications in nanobioelectronics. Chem. Phys. Chem. 2004, 5, 1084–1104. [Google Scholar] [CrossRef]
  108. Davis, J.J.; Coles, R.J.; Hill, A.O. Protein electrochemistry at carbon nanotube electrodes. J. Electroanal Chem. 1997, 440, 279–282. [Google Scholar]
  109. Britto, P.J.; Santhanam, K.S.V.; Ajayan, P.M. Carbon nanotube electrode for oxidation of dopamine. Bioelectrochem. Bioenerg. 1996, 41, 121–125. [Google Scholar] [CrossRef]
  110. Rubianes, M.D.; Rivas, G.A. Enzymatic biosensors based on carbon nanotubes paste electrodes. Electroanalysis 2005, 17, 73–78. [Google Scholar] [CrossRef]
  111. Novoselov, K.S.; Geim, A.K.; Morozov, S.V.; Jiang, D.; Zhang, Y.; Dubonos, S.V.; Grigorieva, I.V.; Firsov, A.A. Electric field effect in atomically thin carbon films. Science 2004, 306, 666–669. [Google Scholar] [CrossRef]
  112. Cano-Márquez, A.; Rodríguez-Macías, F.; Campos-Delgado, J.; Espinosa-González, C.; Tristán-López, F.; Ramírez-González, D.; Cullen, D.; Smith, D.; Terrones, M.; Vega-Cantú, Y. Ex-mwnts: Graphene sheets and ribbons produced by lithium intercalation and exfoliation of carbon nanotubes. Nano Lett. 2009, 9, 1527–1533. [Google Scholar] [CrossRef]
  113. Fitzer, E.; Köchling, K.-H.; Boehm, H.P.; Marsh, H. Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995). Pure Appl. Chem. 1995, 67, 473–506. [Google Scholar] [CrossRef]
  114. Allen, M.J.; Tung, V.C.; Kaner, R.B. Honeycomb carbon: A review of graphene. Chem. Rev. 2010, 110, 132–145. [Google Scholar] [CrossRef] [PubMed]
  115. Choi, W.; Lahiri, I.; Seelaboyina, R.; Kang, Y. Synthesis of graphene and its applications: A review. Crit. Rev. Solid State Mater. Sci. 2010, 35, 52–71. [Google Scholar] [CrossRef]
  116. Geim, A.; Novoselov, K. The rise of graphene. Nat. Mater. 2007, 6, 183–191. [Google Scholar] [CrossRef] [PubMed]
  117. Ferrari, A.; Meyer, J.; Scardaci, V.; Casiraghi, C.; Lazzeri, M.; Mauri, F.; Piscanec, S.; Jiang, D.; Novoselov, K.; Roth, S. Raman spectrum of graphene and graphene layers. Phys. Rev. Lett. 2006, 97, 644–648. [Google Scholar] [CrossRef]
  118. Ostrovsky, P.M.; Gornyi, I.V.; Mirlin, A.D. Electron transport in disordered graphene. Phys. Rev. B 2006, 74, 235443. [Google Scholar] [CrossRef]
  119. Lawal, A.T. Synthesis and utilization of grapheme for fabrication of electrochemical sensors. Talanta 2015, 131, 424–443. [Google Scholar] [CrossRef]
  120. Wang, Y.; Li, Y.M.; Tang, L.H.; Lu, J.; Li, J.H. Application of graphene-modified electrode for selective detection of dopamine. Electrochem. Commun. 2009, 11, 889–892. [Google Scholar] [CrossRef]
  121. Alwarappan, S.; Erdem, A.; Liu, C.; Li, C.Z. Probing the electrochemical properties of graphene nanosheets for biosensing applications. J. Phys. Chem. C 2009, 113, 8853–8857. [Google Scholar] [CrossRef]
  122. Pumera, M. Electrochemistry of graphene: New horizons for sensing and energy storage. Chem. Rec. 2009, 9, 211–223. [Google Scholar] [CrossRef]
  123. Pumera, M. Graphene-based nanomaterials and their electrochemistry. Chem. Soc. Rev. 2010, 39, 4146–4157. [Google Scholar] [CrossRef]
  124. Kuila, T.; Bosea, S.; Khanra, P.; Mishra, A.K.; Kim, N.H.; Lee, J.H. Recent advances in graphene-based biosensors. Biosens. Bioelectron. 2011, 26, 4637–4648. [Google Scholar] [CrossRef] [PubMed]
  125. Segal, M. Selling graphene by the ton. Nat. Nanotechnol. 2009, 4, 612–614. [Google Scholar] [CrossRef]
  126. de la Torre, G.; Blau, W.; Torres, T. A survey on the functionalization of single-walled nanotubes. The chemical attachment of phthalocyanine moieties. Nanotechnology 2003, 14, 765–771. [Google Scholar] [CrossRef]
  127. Oyama, N.; Anson, F.C. Facile attachment of transition metal complexes to graphite electrodes coated with polymeric ligands. Observation and control of metal-ligand coordination among reactants confined to electrode surfaces. J. Am. Chem. Soc. 1979, 101, 739–741. [Google Scholar] [CrossRef]
  128. Caro, C.A.; Bedioui, F.; Zagal, J.H. Electrocatalytic oxidation of nitrite on a vitreous carbon electrode modified with cobalt phthalocyanine. Electrochim. Acta 2002, 47, 1489–1494. [Google Scholar] [CrossRef]
  129. Cook, M.J. Thin film formulations of substituted phthalocyanines. J. Mater. Chem. 1996, 6, 677–689. [Google Scholar] [CrossRef]
  130. Griveau, S.; Pavez, J.; Zagal, J.H.; Bedioui, F. Electro-oxidation of 2-mercaptoethanol on adsorbed monomeric and electropolymerized cobalt tetra-aminophthalocyanine films. Effect of film thickness. J. Electroanal. Chem. 2001, 497, 75. [Google Scholar] [CrossRef]
  131. Cook, M.J. Phthalocyanine thin films. Pure Appl. Chem. 1999, 71, 2145–2151. [Google Scholar] [CrossRef]
  132. Vukusic, P.S.; Sambles, J.R. Cobalt phthalocyanine as a basis for the optical sensing of nitrogen dioxide using surface plasmon resonance. Thin Solid Film. 1992, 221, 311–317. [Google Scholar] [CrossRef]
  133. Chambrier, I.; Cook, M.J.; Russell, D.A. Synthesis and characterisation of functionalized phthalocyanine compounds for fabrication of self-assembled monolayers. Synthesis 1995, 10, 1283–1286. [Google Scholar] [CrossRef]
  134. Fomo, G.; Nwaji, N.; Nyokong, T. Low symmetric metallophthalocyanine modified electrode via click chemistry for simultaneous detection of heavy metals. J. Electroanal. Chem. 2018, 813, 58–66. [Google Scholar] [CrossRef]
  135. Bélanger, D.; Pinson, J. Electrografting: A powerful method for surface modification. Chem. Soc. Rev. 2011, 40, 3995–4048. [Google Scholar] [CrossRef] [PubMed]
  136. Wang, X.; Liu, Y.; Qiu, W.; Zhu, D. Immobilization of tetra-tert-butylphthalocyanines on carbon nanotubes: A first step towards the development of new nanomaterials. J. Mater. Chem. 2002, 12, 1636–1639. [Google Scholar] [CrossRef]
  137. Ciucu, A.; Baldwin, R.P. Determination of 2-thiothiazolidine-4-carboxylic acid in urine by liquid chromatography with electrochemical detection. Electroanalysis 1992, 4, 515–519. [Google Scholar] [CrossRef]
  138. Cooper, J.R.; Bloom, F.E.; Roth, R.H. The Biochemical Basis of Neuropharmacology, 8th ed.; Oxford University Press: New York, NY, USA, 2003. [Google Scholar]
  139. Kovács, G.L. The Endocrine Brain: Pathophysiological Role of Neuropeptide-Neurotransmitter Interactions. EJIFCC 2004, 15, 107–112. [Google Scholar]
  140. Lövheim, H. A new three-dimensional model for emotions and monoamine neurotransmitters. Med. Hypotheses 2012, 78, 341–348. [Google Scholar] [CrossRef]
  141. Day, M.; Wang, Z.; Ding, J.; An, X.; Ingham, C.A.; Shering, A.F.; Wokosin, D.; Ilijic, E.; Sun, Z.; Sampson, A.R.; et al. Selective elimination of glutamatergic synapses on striatopallidal neurons in Parkinson disease models. Nat. Neurosci. 2006, 9, 251–259. [Google Scholar] [CrossRef] [PubMed]
  142. Paterson, D.S.; Trachtenberg, F.L.; Thompson, E.G.; Belliveau, R.A.; Beggs, A.H.; Darnall, R. Multiple serotonergic brainstem abnormalities in sudden infant death syndrome. JAMA 2006, 296, 2124–2132. [Google Scholar] [CrossRef]
  143. Pluto, R.; Bürger, P. Normal values of catecholamines in blood plasma determined by high-performance liquid chromatography with amperometric detection. Int. J. Sports Med. 1988, 9, 75–78. [Google Scholar] [CrossRef]
  144. Gutiérrez, A.; Primo, E.N.; Eguílaz, M.; Parrado, C.; Rubianes, M.D.; Rivas, G.A. Quantification of neurotransmitters and metabolically related compounds at glassy carbon electrodes modified with bamboo-like carbon nanotubes dispersed in double stranded DNA. Microchem. J. 2017, 130, 40–46. [Google Scholar] [CrossRef]
  145. Yu, D.; Zeng, Y.; Qi, Y.; Zhou, T.; Shi, G. A novel electrochemical sensor for determination of dopamine based on AuNPs@SiO2 core-shell imprinted composite. Biosens. Bioelectron. 2012, 38, 270–277. [Google Scholar] [CrossRef]
  146. Babaei, A.; Sohrabi, M.; Afrasiabi, M. A Sensitive simultaneous determination of epinephrine and piroxicam using a glassy carbon electrode modified with a nickel hydroxide nanoparticles/multiwalled carbon nanotubes composite. Electroanalysis 2012, 24, 2387–2394. [Google Scholar] [CrossRef]
  147. Chiara, G.D. The principles of nerve cell communication. Alcohol Health Res. World 1997, 21, 108–114. [Google Scholar]
  148. Babaei, A.; Taheri, A. Nafion/Ni(OH)2 nanoparticles-carbon nanotube composite modified glassy carbon electrode as a sensor for simultaneous determination of dopamine and serotonin in the presence of ascorbic acid. Sens. Actuators B Chem. 2013, 176, 543–555. [Google Scholar] [CrossRef]
  149. Venton, B.J.; Wightman, R.M. Psychoanalytical electrochemistry: Dopamine and behavior. Anal. Chem. 2003, 75, 414A–421A. [Google Scholar] [CrossRef]
  150. Wightman, R.M.; Amatore, C.; Engstrom, R.C.; Hale, P.D.; Kristensen, E.W.; Kubr, W.G.; May, L.J. Real-time characterization of dopamine overflow and uptake in the rat striatum. Neuroscience 1988, 25, 513–523. [Google Scholar] [CrossRef] [PubMed]
  151. Kawagoe, T.K.; Wightman, R.M. Characterization of amperometry for in vivo measurement of dopamine dynamics in the rat brain. Talanta 1994, 41, 865–874. [Google Scholar] [CrossRef]
  152. Wang, C.; Liu, Q.; Shao, X.; Hu, X. Voltammetric determination of dopamine in human serum and urine at a glassy carbon electrode modified by cysteic acid based on electrochemical oxidation of L-cysteine. Anal. Lett. 2007, 40, 689–704. [Google Scholar] [CrossRef]
  153. Sarkar, C.; Basu, B.; Chakroborty, D.; Dasgupta, P.S.; Basu, S. The immunoregulatory role of dopamine: An update. Brain Behav. Immunol. 2010, 24, 525–528. [Google Scholar] [CrossRef]
  154. Adekunle, A.S.; Agboola, B.O.; Pillay, J.; Ozoemena, K.I. Electrocatalytic detection of dopamine at single-walled carbon nanotubes–iron (III) oxide nanoparticles platform. Sens. Actuators B Chem. 2010, 148, 93–102. [Google Scholar] [CrossRef]
  155. Pecina, M.; Mickey, B.J.; Love, T.; Wang, H.; Langenecker, S.A.; Hodgkinson, C.; Shen, P.H.; Villafuerte, S.; Hsu, D.; Weisenbach, S.L.; et al. DRD2 polymorphisms modulate reward and emotion processing, dopamine neurotransmission and openness to experience. Cortex 2013, 49, 877–890. [Google Scholar] [CrossRef]
  156. Siqueira, J.R., Jr.; Gasparotto, L.H.S.; Oliveira, O.N., Jr.; Zucolotto, V. Processing of electroactive nanostructured films incorporating carbon nanotubes and phthalocyanines for sensing. J. Phys. Chem. C 2008, 112, 9050–9055. [Google Scholar] [CrossRef]
  157. Fashedemi, O.O.; Ozoemena, K.I. A facile approach to the synthesis of hydrophobic iron tetrasulfophthalocyanine (FeTSPc) nano-aggregates on multi-walled carbon nanotubes: A potential electrocatalyst for the detection of dopamine. Sens. Actuat. B. 2011, 160, 7–14. [Google Scholar] [CrossRef]
  158. Yang, J.; Mu, D.; Gao, Y.; Tan, J.; Lu, A.; Ma, D. Cobalt phthalocyanine-graphene complex for electro-catalytic oxidation of dopamine. J. Nat. Gas Chem. 2012, 21, 265–269. [Google Scholar] [CrossRef]
  159. Shaidarova, L.G.; Gedmina, A.V.; Artamonova, M.L.; Chelnokova, I.A.; Budnikov, H.C. Voltammetry determination of dopamine by the electrocatalytic response of an electrode modified by a polyaniline film with an inclusion of copper(II) tetrasulfophthalocyanine. J. Anal. Chem. 2013, 68, 516–524. [Google Scholar] [CrossRef]
  160. Karuppiah, C.; Devasenathipathy, R.; Chen, S.M.; Arulraj, D.; Palanisamy, S.; Mani, V.; Vasantha, V.S. Fabrication of nickel tetrasulfonated phthalocyanine functionalized multiwalled carbon nanotubes on activated glassy carbon electrode for the detection of dopamine. Electroanalysis 2015, 27, 485–493. [Google Scholar] [CrossRef]
  161. Xu, H.; Xiao, J.; Yan, L.; Zhu, L.; Liu, B. An electrochemical sensor for selective detection of dopamine based on nickel tetrasulfonated phthalocyanine functionalized nitrogen-doped graphene nanocomposites. J. Electroanal. Chem. 2016, 779, 92–98. [Google Scholar] [CrossRef]
  162. Sakthinathan, S.; Lee, H.F.; Chen, S.M.; Tamizhdurai, P. Electrocatalytic oxidation of dopamine based on non-covalent functionalization of manganese tetraphenylporphyrin/reduced graphene oxide nanocomposite. J. Colloid Interface Sci. 2016, 468, 120–127. [Google Scholar] [CrossRef]
  163. Nemakal, M.; Aralekallu, S.; Imadadulla, M.; Prabhu, C.P.K.; Lokesh, K.S. Chemisorbed palladium phthalocyanine for simultaneous determination of biomolecules. Microchem. J. 2018, 143, 82–91. [Google Scholar] [CrossRef]
  164. Prabhu, C.P.K.; Nemakal, M.; Aralekallu, S.; Imadadulla, M.; Palanna, M.; Sajjan, V.A.; Akshitha, D.; Sannegowda, L.K. A comparative study of carboxylic acid and benzimidazole phthalocyanines and their surface modification for dopamine sensing. J. Electroanal. Chem. 2019, 847, 113262. [Google Scholar] [CrossRef]
  165. Demir, F.; Yenilmez, H.Y.; Koca, A.; Bayir, Z.A. Metallo-phthalocyanines containing thiazole moieties: Synthesis, characterization, electrochemical and spectroelectrochemical properties and sensor applications. J. Electroanal. Chem. 2019, 832, 254–265. [Google Scholar] [CrossRef]
  166. Mounesh; Jilani, B.S.; Pari, M.; Reddy, K.R.V.; Lokesh, K.S. Simultaneous and sensitive detection of ascorbic acid in presence of dopamine using MWCNTs-decorated cobalt (II) phthalocyanine modified GCE. Microchem. J. 2019, 147, 755–763. [Google Scholar] [CrossRef]
  167. Jilani, B.S.; Mounesh, P.M.; Reddy, K.R.V. Tetrafurfurylamine anchored N4-macrocycle as potential catalyst for electrochemical redox reactions of biomolecules. Anal. Bioanal. Electrochem. 2019, 11, 892–912. [Google Scholar]
  168. Chen, Y.; Zhang, X.F.; Wang, A.J.; Zahng, Q.L.; Huang, H.; Feng, J.J. Ultrafine Fe3C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine. Microchim. Acta 2019, 186, 651–660. [Google Scholar] [CrossRef]
  169. Pari, M.; Reddy, K.R.V.; Fasiulla; Chandrakala, K.B. Amperometric determination of dopamine based on an interface platform comprising tetra-substituted Zn2+ phthalocyanine film layer with embedment of reduced graphene oxide. Sens. Actuat. A 2020, 316, 112377. [Google Scholar] [CrossRef]
  170. Fredj, Z.; Ali, M.B.; Abbas, M.N.; Dempsey, E. Simultaneous determination of ascorbic acid, uric acid and dopamine using silver nanoparticles and copper monoamino-phthalocyanine functionalized acrylate polymer. Anal. Methods 2020, 12, 3883–3891. [Google Scholar] [CrossRef]
  171. Ndebele, N.; Sen, P.; Nyokong, T. Electrochemical detection of dopamine using phthalocyanine-nitrogen-doped graphene quantum dot conjugates. J. Electroanal. Chem. 2021, 886, 115111. [Google Scholar] [CrossRef]
  172. Sariogullari, H.; Sengul, I.F.; Gurek, A.G. Comparative study on sensing and optical properties of carbazole linked novel zinc (II) and cobalt (II) phthalocyanines. Polyhedron 2022, 227, 116139. [Google Scholar] [CrossRef]
  173. Sudhakara, S.M.; Kotresh, H.M.N.; Devendrachari, M.C.; Khan, F. Synthesis and electrochemical investigation of tetra amino cobalt (II) phthalocyanine functionalized polyaniline nanofiber for the selective detection of dopamine. Electroanalysis 2020, 32, 1807–1817. [Google Scholar] [CrossRef]
  174. Akyuz, D.; Demirbas, U. Sensor performances of novel piperidine substituted cobalt (II) and copper (II) phthalocyanines for detection of dopamine, ascorbic acid and uric acid. J. Organomet. Chem. 2022, 982, 122537. [Google Scholar] [CrossRef]
  175. Wu, B.; Li, M.; Ramachandran, R.; Niu, G.; Zhang, M.; Zhao, C.; Xu, Z.; Wang, F. GQDs incorporated CoPc nanorods for electrochemical detection of dopamine and uric acid. Adv. Mater. Interfaces 2023, 10, 2200738. [Google Scholar] [CrossRef]
  176. Luhana, C.; Mashazi, P. Simultaneous detection of dopamine and paracetamol on electroreduced graphene oxide–cobalt phthalocyanine polymer nanocomposite electrode. Electrocatalysis 2023, 14, 406–417. [Google Scholar] [CrossRef]
  177. Shoba, S.; Mambanda, A.; Booysen, I.N. Electrocatalytic effects of a clicked film of an asymmetric A3B (A = 3-oxyflavone, B = α-(ethynyl)benzyl alcohol) CoPc complex on a glassy carbon electrode for the detection of dopamine. J. Electroanal. Chem. 2024, 956, 118086. [Google Scholar] [CrossRef]
  178. Ozsoz, M.; Erdern, A.; Kilinc, E.; Gokgunnec, L. Mushroom-based cobalt phthalocyanine dispersed amperometric biosensor for the determination of phenolic compounds. Electroanalysis 1996, 8, 147–150. [Google Scholar] [CrossRef]
  179. Oni, J.; Westbroek, P.; Nyokong, T. Electrochemical behavior and detection of dopamine and ascorbic acid at an iron(II)-tetrasulfo-phthalocyanine modified carbon paste microelectrode. Electroanalysis 2003, 15, 848–954. [Google Scholar] [CrossRef]
  180. Yang, G.J.; Xu, J.J.; Wang, K.; Chen, H.Y. Electrocatalytic oxidation of dopamine and ascorbic acid on carbon paste electrode modified with nanosized cobalt phthalocyanine particles: Simultaneous determination in the presence of CTAB. Electroanalysis 2006, 18, 282–290. [Google Scholar] [CrossRef]
  181. Patrascu, D.; David, I.; David, V.; Mihailciuc, C.; Stamatin, I.; Ciurea, J.; Nagy, L.; Nagy, G.; Ciucu, A.A. Selective voltammetric determination of electroactive neuromodulating species in biological samples using iron(II) phthalocyanine modified multi-wall carbon nanotubes paste electrode. Sens. Actuat. B 2011, 156, 731–736. [Google Scholar] [CrossRef]
  182. Deon, M.; Caldas, E.M.; da Rosa, D.S.; de Menezes, E.W.; Dias, S.L.P.; Pereira, M.B.; Costa, T.M.H.; Arenas, L.T.; Benvenutti, E.V. Mesoporous silica xerogel modified with bridged ionic silsesquioxane used to immobilize copper tetrasulfonated phthalocyanine applied to electrochemical determination of dopamine. J. Solid State Electrochem. 2015, 19, 2095–2105. [Google Scholar] [CrossRef]
  183. Zampa, F.M.; de Brito, A.C.; Kitagawa, I.L.; Constantino, J.L.C.; Oliviera, O.N., Jr.; Da Cunha, N.H.; Zucolotto, V.; Jose, R.D.S., Jr.; Eiras, C. Natural gum-assisted phthalocyanine immobilization in electroactive nanocomposites:  Physicochemical characterization and sensing applications. Biomacromolecules 2007, 8, 3408–3413. [Google Scholar] [CrossRef]
  184. Alessio, P.; Rodriguez-Mendez, M.L.; De Saja Saez, J.A.; Constantino, C.J.L. Iron phthalocyanine in non-aqueous medium forming layer-by-layer films: Growth mechanism, molecular architecture and applications. Phys. Chem. Chem. Phys. 2010, 12, 3972–3983. [Google Scholar] [CrossRef]
  185. Zampa, M.F.; Araujo, I.M.S.; dos Santos, J.R., Jr.; Zucolotto, V.; Leite, J.R.S.A.; Eiras, C. Development of a novel biosensor using cationic antimicrobial peptide and nickel phthalocyanine ultrathin films for electrochemical detection of dopamine. Int. J. Anal. Chem. 2012, 2012, 850969. [Google Scholar] [CrossRef] [PubMed]
  186. de Lucena, N.C.; Miyazaki, C.M.; Shimizu, F.M.; Constantino, C.J.L.; Ferreira, M. Layer-by-layer composite film of nickel phthalocyanine and montmorillonite clay for synergistic effect on electrochemical detection of dopamine. Appl. Surf. Sci. 2018, 436, 957–966. [Google Scholar] [CrossRef]
  187. Peng, J.; Zhuge, W.; Liu, Y.; Zhang, C.; Yang, W.; Huang, Y. Photoelectrochemical dopamine sensor based on Cu-doped Bi2WO6 micro-flowers sensitized cobalt tetraaminophthalocyanine functionalized graphene oxide. J. Electrochem. Soc. 2019, 166, B1612–B1619. [Google Scholar] [CrossRef]
  188. Peng, J.; Li, X.; Liu, Y.; Zhuge, W.; Zhang, C.; Huang, Y. Photoelectrochemical sensor based on zinc phthalocyanine semiconducting polymer dots for ultrasensitive detection of dopamine. Sens. Actuat. B 2022, 360, 131619. [Google Scholar] [CrossRef]
  189. Chernyshov, D.V.; Shvedene, N.V.; Antipova, E.R.; Pletnev, I.V. Ionic liquid-based miniature electrochemical sensors for the voltammetric determination of catecholamines. Anal. Chim. Acta 2008, 621, 178–184. [Google Scholar] [CrossRef] [PubMed]
  190. Barros, S.B.A.; Rahim, A.; Tanaka, A.A.; Arenas, L.T.; Landers, R.; Gushikem, Y. In situ immobilization of nickel(II) phthalocyanine on mesoporous SiO2/C carbon ceramic matrices prepared by the sol–gel method: Use in the simultaneous voltammetric determination of ascorbic acid and dopamine. Electrochim. Acta 2013, 87, 140–147. [Google Scholar] [CrossRef]
  191. Rahim, A.; Barros, S.B.A.; Kubota, L.T.; Gushikem, Y. SiO2/C/Cu(II)phthalocyanine as a biomimetic catalyst for dopamine monooxygenase in the development of an amperometric sensor. Electrochim. Acta 2011, 56, 10116–10121. [Google Scholar] [CrossRef]
  192. Tshenkeng, K.; Mashazi, P. Covalent attachment of cobalt (II) tetra-(3-carboxyphenoxy) phthalocyanine onto pre-grafted gold electrode for the determination of catecholamine neurotransmitters. Electrochim. Acta 2020, 360, 137015. [Google Scholar] [CrossRef]
  193. Luhana, C.; Moyo, I.; Tshenkeng, K.; Mashazi, P. In-sera selectivity detection of catecholamine neurotransmitters using covalent composite of cobalt phthalocyanine and aminated graphene quantum dots. Microchem. J. 2022, 180, 107605. [Google Scholar] [CrossRef]
  194. Moyo, I.; Mwanza, D.; Mashazi, P. Novel covalent immobilization of cobalt (II) octa acyl chloride phthalocyanines onto phenylethylamine pre-grafted gold via spontaneous amidation. Electrochim. Acta 2022, 422, 140550. [Google Scholar] [CrossRef]
  195. Moyo, I.; Mwanza, D.; Mashazi, P. pH sensitive thin films of iron phthalocyanines as electrocatalysts for the detection of neurotransmitters. J. Organomet. Chem. 2023, 990, 122662. [Google Scholar] [CrossRef]
  196. da Silva, V.N.C.; Farias, E.A.O.; Araujo, A.R.; Magalhaes, F.E.X.; Fernandes, J.R.N.; Souza, J.M.T.; Eiras, C.; da Silva, D.A.; do Vale Bastos, V.H.; Teixeira, S.S. Rapid and selective detection of dopamine in human serum using an electrochemical sensor based on zinc oxide nanoparticles, nickel phthalocyanines, and carbon nanotubes. Biosens. Bioelectron. 2022, 210, 114211. [Google Scholar]
  197. Buleandra, M.; Popa, D.E.; David, I.G.; Ciucu, A.A. A simple and efficient cyclic square wave voltammetric method for simultaneous determination of epinephrine and norepinephrine using an activated pencil graphite electrode. Microchem. J. 2021, 160, 105621. [Google Scholar] [CrossRef]
  198. Lechin, F.; Van der Dijs, B.; Lechin, A.E. Circulating serotonin, catecholamines and CNS circuitry related to some cardiorespiratory and vascular disorders. J. Appl. Res. 2005, 5, 605–621. [Google Scholar]
  199. Wood, J.P.; Traub, S.J.; Lipinski, C. Safety of epinephrine for anaphylaxis in the emergency setting. World J. Emerg. Med. 2013, 4, 245–251. [Google Scholar] [CrossRef] [PubMed]
  200. Zimmerman, J.; Cahalan, M. Vasopressors and inotropes. In Pharmacology and Physiology for Anesthesia; Hemmings, H.C., Egan, T.D., Eds.; Saunders (Elsevier): Amsterdam, The Netherlands, 2013; pp. 390–404. [Google Scholar]
  201. Pihel, K.; Schroeder, T.J.; Wightman, R.M. Rapid and selective cyclic voltammetric measurements of epinephrine and norepinephrine as a method to measure secretion from single bovine adrenal medullary cells. Anal. Chem. 1994, 66, 4532–4537. [Google Scholar] [CrossRef]
  202. Ni, Y.; Gui, Y.I.; Kokot, S. Application of multiway-variate calibration to simultaneous voltammetric determination of three catecholamines. Anal. Methods 2011, 3, 385–392. [Google Scholar] [CrossRef]
  203. Cho, T.; Wang, J. Selective voltammetric measurements of epinephrine and norepinephrine in presence of common interferences using cyclic square-voltammetry at unmodified carbon electrodes. Electroanalysis 2018, 30, 1028–1032. [Google Scholar] [CrossRef]
  204. Beitollahi, H.; Karimi-Maleh, H.; Khabazzadeh, H. Nanomolar and selective determination of epinephrine in the presence of norepinephrine using CPE modified with carbon nanotubes and novel 2-(4-Oxo-3-phenyl-3,4-dihydro-quinazolinyl)-N-phenylhydrazinecarbothioamide. Anal. Chem. 2008, 80, 9848–9851. [Google Scholar] [CrossRef]
  205. Goyal, R.N.; Bishnoi, S. Simultaneous determination of epinephrine and norepinephrine in human blood plasma and urine samples using nanotubes modified edge plane pyrolytic graphite electrode. Talanta 2011, 84, 78–83. [Google Scholar] [CrossRef]
  206. Lavanya, N.; Sekar, C. Electrochemical sensor for simultaneous determination of epinephrine and norepinephrine based on cetyltrimethylammonium bromide assisted SnO2 nanoparticles. J. Electroanal. Chem. 2017, 801, 503–510. [Google Scholar] [CrossRef]
  207. Shahrokhian, S.; Ghalkhani, M.; Amini, M.K. Application of carbon-paste electrode modified with iron phthalocyanine for voltammetric determination of epinephrine in the presence of ascorbic acid and uric acid. Sens. Actuat. B 2009, 137, 669–675. [Google Scholar] [CrossRef]
  208. Moraes, F.C.; Golinelli, D.L.C.; Mascaro, L.H.; Machado, S.A.S. Determination of epinephrine in urine using multi-walled carbon nanotube modified with cobalt phthalocyanine in a paraffin composite electrode. Sens. Actuat. B 2010, 148, 492–497. [Google Scholar] [CrossRef]
  209. Young, S.N.; Leyton, M. The role of serotonin in human mood and social interaction. Insight from altered tryptophan levels. Pharmacol. Biochem. Behav. 2002, 71, 857–865. [Google Scholar] [CrossRef]
  210. Isbister, G.K.; Bowe, S.J.; Dawson, A.H.; Whyte, I.M. Relative toxicity of selective serotonin reuptake inhibitors (SSRIs) in overdose. J. Toxicol. Clin. Toxicol. 2004, 42, 277–285. [Google Scholar] [CrossRef] [PubMed]
  211. Seyedabadi, M.; Fakhfouri, G.; Ramezani, V.; Mehr, S.E.; Rahimian, R. The role of serotonin in memory: Interactions with neurotransmitters and downstream signaling. Exp. Brain Res. 2014, 232, 723. [Google Scholar] [CrossRef] [PubMed]
  212. Kaye, W.H.; Weltzin, T.E.; Hsu, L.G. Serotonin and norepinephrine activity in anorexia and bulimia nervosa: Relationship to nutrition, feeding, and mood. In Biology of Depressive Disorders, Part B: Subtypes of Depression and Comorbid Disorders; Mann, J.J., Kupfe, D.J., Eds.; Plenum Press: New York, NY, USA, 1993; pp. 127–149. [Google Scholar]
  213. Sharma, S.; Singh, N.; Tomar, V.; Chandra, R. A review on electrochemical detection of serotonin based on surface modified electrodes. Biosens. Bioelectron. 2018, 107, 76–93. [Google Scholar] [CrossRef]
  214. de Irazu, S.; Unceta, N.; Samedro, M.B.; Goicolea, M.A.; Barrio, B.R. Multimembrane carbon fiber microelectrodes for amperometric determination of serotonin in human urine. Analyst 2001, 126, 495–500. [Google Scholar] [CrossRef]
  215. Apetrei, I.M.; Apetrei, C. Amperometric tyrosinase based biosensors for serotonin detection. Rom. Biotechnol. Lett. 2013, 18, 8253–8262. [Google Scholar]
  216. Staden, J.F.; Georgescu, R.; Staden, R.I.S.; Calinescu, I. Evaluation of amperometric dot microsensors for the analysis of serotonin in urine samples. J. Electrochem. Soc. 2014, 161, B49–B54. [Google Scholar] [CrossRef]
  217. de Oliveira, M.S.; de Oliveira Farias, E.A.; de Sousa, A.M.S.; Dionisio, N.A.; Teixeira, P.R.S.; Teixeira, A.S.N.M.; da Silva, D.A.; Eiras, C. Composite films based on copper nanoparticles and nickel phthalocyanine as electrochemical sensors for serotonin detection. Surf. Interfaces 2021, 25, 101245. [Google Scholar] [CrossRef]
Figure 1. General chemical structure of MPc; α—non-peripheral, β—peripheral.
Figure 1. General chemical structure of MPc; α—non-peripheral, β—peripheral.
Chemosensors 13 00243 g001
Figure 2. Schematic presentation of an electrocatalytic reduction process on an MPc-modified electrode.
Figure 2. Schematic presentation of an electrocatalytic reduction process on an MPc-modified electrode.
Chemosensors 13 00243 g002
Figure 3. Monoamine neurotransmitters.
Figure 3. Monoamine neurotransmitters.
Chemosensors 13 00243 g003
Table 1. Electrochemical sensors based on phthalocyanines reported for DA detection.
Table 1. Electrochemical sensors based on phthalocyanines reported for DA detection.
AnalytesElectrode and MediumDetection TechniqueLinear Range [×10−6 mol·L−1]Detection Limit [×10−6 mol·L−1]SampleRecovery (%)Ref.
DANiTAPc/GCE
0.1 M PBS, pH 7.4
LSV0.2–200.09Pharmaceuticals
Plasma
Urine
96.5–103.0
97.3–103.5
95.7–103.6
[38]
DAMWCNT/CoPc/GCE
0.1 PBS, pH 4.0
DPV3.11–93.250.256--[36]
DAMWCNT/PAMAM/
NiTsPc/GCE
0.1 M H2SO4
CV2.5–2400.54--[156]
DAf-MWCNT/Nano-FeTSPc/GCE
0.1 M PBS, pH 7
SWV20–510.35--[157]
DACoPc/Gr/GCE
0.2 M PBS, pH 4
SWV3–75---[158]
DANafion/CuTsPc/PANI/GCE
0.1 M H2SO4
FIA0.01–10000.005--[159]
DAMWCNT/NiTsPc/AGCE
0.1 M PBS, pH 4.0
SWV0.02–13840.001Human serum98.4–100.7[160]
DAN-G/NiTsPc/GCE
0.1 M PBS, pH 7.4
Amp0.1–2000.1--[161]
DArGO/Mn-TPP/GCE
0.05 M PBS, pH 7
Amp0.3–188.80.008Pharmaceuticals
Human urine
90.06–92.06
90.6–97.5
[162]
DA + AA + UAMWCNTs/PdTAPc/GCE
0.25 M H2SO4
CVDA: 2–16
AA: 3–24
UA: 5–40
DA: 0.6
AA: 1.0
UA: 1.5
Human urineDA: 102–103.3
AA: 99–100.6
UA: 99.9–101.3
[163]
DACNP/FeTCAPc/GCE
PBS (pH 7)
CA0.05–0.500.016--[164]
DACNP/polyFeTBImPc/GCE
PBS, pH 7
CA0.05–0.500.01Pharmaceuticals100.32–102[164]
DACoTSPc/Gr/GCE
0.1 M PBS, pH 7.3
DPSV0.02–2200.00087--[15]
DACoPc/GCE
0.1 M PBS, pH 7.4
DPV0.223–8.5130.0205--[165]
DA + UAMnPc/GCE
0.1 M PBS, pH 7.4
DPVDA: 0.029–6.239
UA: 1.127–10.977
DA: 0.0020
UA: 0.0146
--[165]
DA + UAZnPc/GCE
0.1 M PBS, pH 7.4
DPVDA: 0.021–7.441
UA: 0.014–8.577
DA: 0.0105
UA: 0.0305
--[165]
DA + AAMWCNT/CoTMBANAPc/GCE
PBS, pH 7
DPVDA: 7.5–67.5
AA: 7.5–67.5
DA: 0.33
AA: 6.66
--[166]
DA + AA + UACoTGPc/GCE
PBS, pH 7
DPVDA: 2–12
AA: 2–12
UA: 2–12
DA: 1.2
AA: 0.5
UA: 0.5
Pharmaceuticals
Urine
DA: 107.5
AA: 102
UA: 96.7–101.2
[58]
DAPoly(CoTNBAPc)/GCE
0.1 M PBS, pH 7
Amp0.1–10.02Pharmaceuticals102–104[13]
DA + UA / DMZCoTfurNH2Pc/GCE
PBS, pH 7
DPVDA: 3–21
UA: 2–14
DMZ: 0.3–2.1
DA: 1
UA: 0.66
DMZ: 0.1
Milk powder
Urine
DA: –
UA: 99.8–101.2
DMZ: 97.5–101.0
[167]
DA + AA + UA + XOFe3C@NGCSs/GCE
PBS, pH 6
DPVDA: 1.2–120.8
AA: 54–5491
UA: 4.8–263
XA: 4.8–361
DA: 0.34
AA: 16.7
UA: 1.4
XA: 1.5
SerumDA: 98.8
AA: 103.16
UA: 97.26
XA: 101.22
[168]
DArGO/ZnTPEBIPc/GCE
PBS, pH 4
Amp0.02–10.006Pharmaceuticals96.7–107.5[169]
DA + AA + UAAgNPs/Cu-MAPA/GCE
0.1 M PBS, pH 7.4
DPVDA: 0.01–10
AA: 0.01–10
UA: 0.01–10
DA: 0.0007
AA: 0.0025
UA: 0.005
Articial urine94–107[170]
DANGQD/CoPc/GCE
0.1 M PBS
CA100–10000.12--[171]
DA + UAGr/Car-ZnPc/GCE
0.1 M PBS, pH 7
DPVDA: 2–16
UA: 20–160
DA: 0.079
UA: 0.33
Tap waterUA: 93.33–95[172]
DA + UAGr/Car-CoPc/GCE
0.1 M PBS, pH 7
DPVDA: 2–14
UA: 12–84
DA: 0.206
UA: 0.53
Tap water-[172]
DATACoPc/PANI/GCE
0.1 M PBS, pH 7
CA20–2000.064Pharmaceuticals103–103.6[173]
DA + AA + UAPoly-3N-CoPc/GCE
PBS, pH 7.4
DPVDA: 3.83–19
AA: 1.4–60
UA: 3.94–53
DA: 3.12
AA: 0.49
UA: 0.87
--[174]
DA + AA + UAPoly-3N-CuPc/GCE
PBS, pH 7.4
DPVDA: 3.71–19
AA: 3.69–53
UA: 3.55–53
DA: 2.53
AA: 0.52
UA: 1.31
--[174]
DA + UACoPc/GQDs/GCE
0.001 M PBS, pH 7
DPVDA: 2.91–16.2
UA: 10.76–3003
DA: 0.021
UA: 0.145
Human urineDA: 91.3–104.5
UA: 91–95.2
[175]
DA + PARPoly-CoTAPc/ERGO/GCE
0.1 M PBS, pH 7.4
DPVDA: 2–100
PA: 7–90
DA: 0.095
PA: 0.104
Synthetic urineDA: 99.5–103
PA: 96–101
[176]
DAClicked-α-CoPc-flav3/GCE
PBS, pH 6.3
SWV2–140.31Wastewater97.1[177]
DAPPO/CoPc/CPE
0.05 M PBS, pH 7.4
AmpUp to 1.87.5Urine-[178]
DA + 5-HTFePc/CPE
FeTSPc/CPE
FeTAPc/CPE
TRIS, pH 7.4
OSWVDA: 1–15
5-HT: 1–15
DA: 1
5-HT: 1
--[47]
DA + AAFeTSPc/CPE
pH 7.4
CV-DA: 0.45
AA: 0.75
--[179]
DA + AANano-CoPc/CPE
0.025 M PBS, pH 7.4 + 4×-10−4 M CTAB
DPVDA: 3–100
AA: 5–300
DA: 1
AA: 1.7
PharmaceuticalsDA: 97.5–103.9
AA: 96.9–104.5
[180]
DAMWCNT/FePc/CPE
PBS, pH 7.4
DPV5–250.205Serum-[181]
DASi-Db/CuTsPc/CPE
0.1 M PBS, pH 4.5
CA9.9–107.10.42--[182]
DA(PAH/NiTsPc)5/ITOE
0.05 M H2SO4
CV-0.089--[183]
DA(PAH/Chicha/PAH/NiTsPc)5/ITOE
0.05 M H2SO4
CV0.025–30.105--[183]
DAPAH/FePc/AgNP/ITOE
0.1 M KCl
CV2–970.86--[184]
DADS01/NiTsPc/ITOE
0.05 M H2SO4
CV0–19.61.665--[185]
DA(PEI/Na+MMT/PEI/NiTsPc)10/ITOE
0.1 M PBS, pH 7.0
DPV5–1501Human urine94–111[186]
DA + L-DopaFePc/ED/ITOE
0.1 M KCl
DPVDA: 2–80
LD: 2–120
DA: 0.288
LD: 0.564
--[18]
DACoTAPc-GO/Cu-Bi2WO6/ITOE
BRB, pH 7.4
PEC sensor0.05–5
5–250
0.0072Pharmaceuticals99.2–106.7[187]
DAZnPc-P8BT-Pdots/ITOEPEC sensor0.0025–1250.00169--[188]
DACoTCPhOPc/PEA/AuE
PBS, pH 7.4
CV5–1001.32--[189]
DAAmGQDs-CoTCPhOPc/IPA/AuE
0.1 M PBS, pH 7.4
DPV1–500.20Calf serum101–106[190]
DACoOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV500.064--[191]
DAFeOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV1–500.25Calf serum96.9–105[192]
DACoTBuPc/IL/SPGE
0.1 M H2SO4 + 0.01 M KCl, pH 1
CV3.9–1001.2--[193]
DA + AANiPc/CCE
0.5 M KCl, pH 5
DPVDA: 40–1080
AA: 90–2110
DA: 0.26
AA: 0.45
SyntheticDA: 107.25–108.25
AA: 101.25–108.75
[194]
DASiO2/C/CuPc disk electrode
0.08 M BRB, pH 6
Amp10–1400.6Synthetic100[195]
DANiTsPc/ZnONPs/CNT/PGE
0.1 M KH2PO4, pH 3.4
DPV
CA
0–15
0–7
0.007
0.024
Human serum100.83–104[196]
Table 2. Electrochemical sensors based on phthalocyanines reported for EP and NP detection.
Table 2. Electrochemical sensors based on phthalocyanines reported for EP and NP detection.
AnalytesElectrode and MediumDetection TechniqueLinear Range [×10−6 mol·L−1]Detection Limit [×10−6 mol·L−1]SampleRecovery (%)Ref.
EPFePc/CPE
0.1 M ABS, pH 4
DPV1–3000.5Pharmaceuticals103.8[207]
EPParaffin-MWCNT-CoPc/CPE
0.1 M PBS, pH 6
DPV1.33–5.50.0156Human urine95.7–98.1[208]
EPMWCNT/Fe3O4/29H,31H-P/GCE
PBS, pH 7.2
DPV7.5–564.6--[57]
EPMWCNT/ZnO/29H,31H-P/GCE
PBS, pH 7.2
DPV7.5–566.5--[57]
EPCoTCPhOPc/PEA/AuE
PBS, pH 7.4
CV5–1003.08--[189]
EPAmGQDs-CoTCPhOPc/IPA/AuE
0.1 M PBS, pH 7.4
DPV1–500.23Calf serum89–92[190]
EPCoOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV5–500.22--[191]
EPFeOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV1–300.45Calf serum101–106[192]
EPCoTBuPc/IL/SPGE
0.1 M H2SO4 + 0.01 M KCl, pH 1
CV0.29–1001.13--[193]
NPMWCNT/Fe3O4/29H,31H-P/GCE
PBS, pH 7.2
DPV7.5–482.2--[57]
NPMWCNT/ZnO/29H,31H-P/GCE
PBS, pH 7.2
DPV7.5–481.7--[57]
NPCoTCPhOPc/PEA/AuE
PBS, pH 7.4
CV5–1002.11--[189]
NPAmGQDs-CoTCPhOPc/IPA/AuE
0.1 M PBS, pH 7.4
DPV1–500.45Calf serum85–102[190]
NPCoOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV0.5–500.17--[191]
NPFeOCAPc/PEA/AuE
0.1 M PBS, pH 7.4
DPV1–500.34Calf serum93.5–100[192]
Table 3. Electrochemical sensors based on phthalocyanines reported for 5-HT detection.
Table 3. Electrochemical sensors based on phthalocyanines reported for 5-HT detection.
AnalytesElectrode and MediumDetection TechniqueLinear Range [×10−6 mol·L−1]Detection Limit [×10−6 mol·L−1]SampleRecovery (%)Ref.
5-HTNiTSPc/Nafion/CFE
0.1 M PBS, pH 7.4
SWV0.005–0.090.0038Urine92–93[214]
5-HTTyr-CoPc/CPE
0.1 M PBS, pH 7
Amp4–1400.84Walnuts97–104[215]
5-HTG-FePc/GPE
0.1 M KCl + PBS, pH 3
DPV1–10000.76Urine96.41[216]
5-HTGR-FePc/GPE
0.1 M KCl + PBS, pH 3
DPV1–10000.734Urine97.07[216]
5-HT(PAH/NiTsPc/PAH/
CuNPs)/ITOE
0.1 M BRB, pH 2.2
CV0.35–1350.13--[217]
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Ciucu, A.A.; Buleandră, M.; Popa, D.E.; Ștefănescu, D.C. Phthalocyanine-Modified Electrodes Used in the Electroanalysis of Monoamine Neurotransmitters. Chemosensors 2025, 13, 243. https://doi.org/10.3390/chemosensors13070243

AMA Style

Ciucu AA, Buleandră M, Popa DE, Ștefănescu DC. Phthalocyanine-Modified Electrodes Used in the Electroanalysis of Monoamine Neurotransmitters. Chemosensors. 2025; 13(7):243. https://doi.org/10.3390/chemosensors13070243

Chicago/Turabian Style

Ciucu, Anton Alexandru, Mihaela Buleandră, Dana Elena Popa, and Dragoș Cristian Ștefănescu. 2025. "Phthalocyanine-Modified Electrodes Used in the Electroanalysis of Monoamine Neurotransmitters" Chemosensors 13, no. 7: 243. https://doi.org/10.3390/chemosensors13070243

APA Style

Ciucu, A. A., Buleandră, M., Popa, D. E., & Ștefănescu, D. C. (2025). Phthalocyanine-Modified Electrodes Used in the Electroanalysis of Monoamine Neurotransmitters. Chemosensors, 13(7), 243. https://doi.org/10.3390/chemosensors13070243

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