Chemosensors, Volume 11, Issue 3 (March 2023) – 51 articles

Molecularly imprinted plasmonic nanosensors are robust devices capable of selective target interaction, and in some cases reaction catalysis. Recent advances in control of nanoscale structure have opened the door for development of a wide range of chemosensors for environmental monitoring. The soaring rate of environmental pollution through human activities and its negative impact on the ecosystem demands an urgent interest in developing rapid and efficient techniques that can easily be deployed for in-field assessment and environmental monitoring purposes. Organophosphate pesticides (OPPs) play a significant role for agricultural use; however, they also present environmental threats to human health due to their chemical toxicity. Plasmonic sensors are thus vital analytical detection tools that have been explored for many environmental applications and OPP detection due to their excellent properties such as high sensitivity, selectivity, and rapid recognition capability. Molecularly imprinted polymers (MIPs) have also significantly been recognized as a highly efficient, low-cost, and sensitive synthetic sensing technique that has been adopted for environmental monitoring of a wide array of environmental contaminants, specifically for very small molecule detection. In this review, the general concept of MIPs and their synthesis, a summary of OPPs and environmental pollution, plasmonic sensing with MIPs, surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS) MIP sensors, and nanomaterial-based sensors for environmental monitoring applications and OPP detection have been elucidated according to the recent literature. In addition, a conclusion and future perspectives section at the end summarizes the scope of molecularly imprinted plasmonic sensors for environmental applications. Full article

Recently, people are becoming more concerned about their physical health and putting forward higher requirements for an early and painless diagnosis of diseases. Traditional methods, such as surface plasmon resonance (SPR), enzyme-linked immunosorbent assay (ELISA), surface-enhanced raman spectroscopy (SERS), and colorimetric methods have been used for the detection of biomarkers with high selectivity and sensitivity; however, these methods still need to be further improved for immediate and rapid diagnosis. Herein, organic thin-film transistors (OTFTs)-based biosensors offer the advantages of good flexibility, low-cost fabrication, reasonable sensitivity, and great biocompatibility for efficient determination of biomarkers in complex samples, including saliva, sweat, urine, and blood, respectively, exhibiting great potential in early disease diagnosis and clinical treatment. Full article

Ammonium (NH₄⁺) ions are a primary contaminant in the river and along the waterside near an agricultural area, therefore, necessitating sensitive detection of pollutants before irreversibly damaging environment. Herein, a new approach of metal-organic framework-derived tungsten ethoxide/polypyrrole-reduced graphene oxide (MOFs-W(OCH₂CH₃)₆/Ppy-rGO) electrochemical sensors are introduced. Through a simple hydrothermal process, Ppy-rGO is linked to tungsten ethoxide as an organic linker. This creates the MOFs-W(OCH₂CH₃)₆/Ppy-rGO nanocrystal through hydrogen bonding. The synergistic combination of tungsten ethoxide and Ppy-rGO provides three-fold advantages: stabilization of Ppy-rGO for extended usage, enabling detection of analytes at ambient temperature, and availability of multiple pathways for effective detection of analytes. This is demonstrated through excellent detection of NH₄⁺ ions over a dynamic concentration range of 0.85 to 3.35 µM with a ppb level detection limit of 0.278 µM (9.74 ppb) and a quantitation limit of 0.843 µM (29.54 ppb). The increment in the concentration of NH₄⁺ ions contributes to the increment in proton (H⁺) concentration. The increment in proton concentration in the solution will increase the bonding activity and thus increase the conductivity. The cyclic voltammetry curves of all concentrations of NH₄⁺ analytes at the operating potential window between −1.5 and 1.5 V exhibit a quasi-rectangular shape, indicating consistent electronic and ionic transport. The distinctive resistance changes of the MOFs-W(OCH₂CH₃)₆/Ppy-rGO to various NH₄⁺ ion concentrations and ultrasensitive detection provide an extraordinary platform for its application in the agriculture industry. Full article

Arrays of zinc oxide (ZnO) nanorods were synthesized over quartz substrates by the hydrothermal method. These nanorods were grown in a predominantly vertical orientation with lengths of 500–800 nm and an average cross-sectional size of 40–80 nm. Gold, with average sizes of 9 ± 1 nm and 4 ± 0.5 nm, and tin nanoclusters, with average sizes of 30 ± 5 nm and 15 ± 3 nm, were formed on top of the ZnO nanorods. Annealing was carried out at 300 °C for 2 h to form ZnO/SnO₂ and ZnO/Au nanorods. The resulting nanorod-arrayed films were comprehensively studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). To fabricate resistive sensor elements, the films were supplied with V/Ni contact metallization on top of the nanorods. The gas sensor performance of the prepared films was evaluated at various temperatures in order to select 200 °C as the optimum one which enabled a selective detection of NO₂. Adding UV-viz irradiation via a light-emitting diode, λ = 400 nm, allowed us to reduce the working temperature to 50 °C and to advance the detection limit of NO₂ to 0.5 ppm. The minimum response time of the samples was 92 s, which is 9 times faster than in studies without exposure to UV-viz radiation. Full article

Inorganic/organic hybrids of ZnO nanorods (NRs)/bisindolo quinoxaline (BIQ) were fabricated for broadband photosensing applications. Multiple material characterizations revealed the BIQ was self-assembled in a regular form of rod-like domain and an irregular form of amorphous aggregation that were distributed on the ZnO NRs. Optical measurements showed that BIQ can absorb visible light with a wavelength up to 630 nm and effectively generate photoelectrons. Moreover, clustering of BIQ can be observed via the 3D optical microscopy. ZnO/BIQ hybrids were promising for future UV and visible light environmental monitoring applications. Full article

In the present work, we describe the electrochemical behaviour of two opioids structurally related to aroyl amides of forensic interest, namely U-47700 and AH-7921. The data obtained allowed for the mise-au-point of a voltammetric determination protocol, that relies on differential pulse voltammetry (DPV) at a glassy carbon electrode in ethanol/0.1 M lithium perchlorate/0.10 M 2,6-lutidine. To apply the method to the analysis of real samples (urines), a clean-up and a preconcentration strategy by solid phase extraction (SPE) using the adsorbent Florisil have been developed. LOQ of 0.2 μg·mL⁻¹ in urine samples with an enrichment factor of 20 and linear range from 5 to 150 μg·mL⁻¹ were obtained. Full article

Being abundant as natural intelligence, plants have attracted huge attention from researchers. Soft film sensors present a novel and promising approach to connect plants with artificial devices, helping us to investigate plants’ intelligence further. Here, recent developments for micro/nano soft film sensors that can be used for establishing intelligent plant systems are summarized, including essential materials, fabrications, and application scenarios. Conductive metals, nanomaterials, and polymers are discussed as basic materials for active layers and substrates of soft film sensors. The corresponding fabrication techniques, such as laser machining, printing, coating, and vapor deposition, have also been surveyed and discussed. Moreover, by combining soft film sensors with plants, applications for intelligent plant systems are also investigated, including plant physiology detection and plant-hybrid systems. Finally, the existing challenges and future opportunities are prospected. Full article

Surface plasmon polaritons (SPPs) are optical surface waves propagating along a metal surface. They exhibit attributes such as field enhancement and sub-wavelength localization, which make them attractive for surface sensing, as they are heavily exploited in surface plasmon biosensors. Electrochemistry also occurs on metal surfaces, and electrochemical techniques are also commonly applied in biosensors. As metal surfaces are integral in both, it is natural to combine these techniques into a single platform. Motivations include: (i) realising a multimodal biosensor (electrochemical and optical), (ii) using SPPs to probe the electrochemical double layer or to probe electrochemical activity, thus revealing complementary information on redox reactions, or (iii) using SPPs to pump electrochemical reactions by creating non-equilibrium energetic electrons and holes in a working electrode through the absorption of SPPs thereon. The latter is of interest as it may yield novel redox reaction pathways (i.e., plasmonic electrocatalysis). Full article

The growing interest in bio-inspired materials is driven by the need for increasingly targeted and efficient devices that also have a low ecological impact. These devices often use specially developed materials (e.g., polymers, aptamers, monoclonal antibodies) capable of carrying out the process of recognizing and capturing a specific target in a similar way to biomaterials of natural origin. In this article, we present two case studies, in which the target is a biomolecule of medical interest, in particular, α-thrombin and cytokine IL-6. In these examples, different biomaterials are compared to establish, with a theoretical-computational procedure known as proteotronics, which of them has the greatest potential for use in a biodevice. Full article

The present contribution proposes an optical method for the detection of glyphosate (GLY) using a Cu(II) bis-(oxamate) complex ([Cu(opba)]²⁻) as the fluorescent probe. It wa found that in acetonitrile solution, its fluorescence increases in the presence of GLY and scales linearly (R² = 0.99) with GLY concentration in the range of 0.7 to 5.5 µM, which is far below that established by different international regulations. The probe is also selective to GLY in the presence of potential interferents, namely aminomethyl phosphonic acid and N-nitrosoglyphosate. Theoretical results obtained by time-dependent density functional theory coupled to a simplified treatment of the liquid environment by using a self-consistent reaction-field revealed that GLY molecules do not coordinate with the central Cu²⁺ ion of [Cu(opba)]²⁻; instead, they interact with its peripheral ligand through hydrogen bond formation. Thereby, GLY plays mainly the role of the proton donor. The results also suggest that GLY increases the dielectric constant of the medium when it contributes to the stabilization of the excited state of the [Cu(opba)]²⁻ and enhancement of its fluorescence. Full article

In this study, a high-voltage (HV) oscillatory square pulse was used to re-excite the laser-induced breakdown spectroscopy (LIBS) signal produced by a nanosecond laser on different loamy soil samples at two different temperatures: ambient and 400 °C. The optimal delay was found for each experimental scheme to maximize the emission signal-to-noise ratio. The detection limits of various contaminants in the soil were studied for different experimental configurations. It was found that the lowest detection limits were achieved by combining HV discharges with LIBS on heated samples, resulting in improvements of up to a factor of 7 compared to LIBS on room temperature samples. Plasma characterization shows that the increased detection sensitivity is due to the rise in plasma temperature and electron density with HV re-excitation, while an increase in removed matter contributes to the emission intensification observed when samples are heated. Full article

A carbon dot-functionalized solution-gated graphene transistor (CD-SGGT) was designed and prepared via the modification of CDs on the gate of SGGT. The above CDs were hydrothermally synthesized using DL-thioctic acid and triethylenetramine as C, N and S sources. The average size of CDs was ~6.2 nm, and there were many amino and carboxyl groups on the CDs’ surfaces. The CDs was then used as a probe for preparation of CD-SGGT sensor for the cobalt(II) (Co²⁺) ions detection. The CD-SGGT sensor showed excellent sensitivity and high selectivity. Remarkably, the limit of detection (LOD) reached 10⁻¹⁹ M. The linear detection range was obtained from 10⁻¹⁹ to 10⁻¹⁵ M. Additionally, the CD-SGGT also showed fast response and good stability. Full article

The easy and rapid analytical tool, electrochemically polymerized (EP) glycine (GN) layered carbon paste electrode (LCPE), was used for the analysis of levofloxacin (LN) using cyclic voltammogram (CV) and differential pulse voltammetry (DPV). The surface features and activities of the electrochemical sensors EPGNLCPE and bare carbon paste electrode (BCPE) were analyzed using electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), CV and DPV methods. The modified sensor (EPGNLCPE)offers a vibrant and sensitive electrochemical LN oxidation peak by controlling overpotential and the electrode material fouling effect unlike BCPE. Under improved experimental conditions, the DPV method was used to analyze LN on EPGNLCPE by varying its concentration in 0.2 M phosphate buffer solution from 30 to 90 µM, resulting in a good linear relationship(between peak current and concentration), lower limit of detection (LOD: 8.436 × 10⁻⁷ M) and lower limit of quantification (LOQ: 2.812 × 10⁻⁶ M). Finally, real-time application of the sensor was tested by analyzing LN in medicinal samples, and good LN recovery was observed. Full article

Flavin mononucleotides (FMNs) and flavin adenine nucleotide (FAD) play vital roles in the electron-transfer processes in diverse enzymatic reactions. Owing to the isoalloxazine chromophore, flavins are easily detectable by surface-enhanced Raman spectroscopy (SERS), a surface-sensitive technique. However, the details of the adsorption of flavins on SERS-active materials have never been investigated. In this study, a comprehensive SERS analysis of flavins containing lumichrome and lumiflavin on silver nanoparticles was conducted. With the aid of density-functional-theory calculations, our results suggested that the flavin molecules were adsorbed on the silver nanoparticles via the N₃ site of the isoalloxazine moiety, which had a stronger adsorption ability than the adenine moiety in the FAD. The SERS spectra of the flavins at different pH values also supported this conclusion. This study demonstrated the feasibility of SERS for the structural characterization of flavins, paving the way for the functional exploration of flavin-labeled detection sensors and flavoprotein researches. Full article

Surface imprinting used for protein recognition in functional cavities is highly effective in imprinting biomacromolecules to avoid template encapsulation during the formation of a molecularly imprinted polymer (MIP) matrix. Herein, we introduce a facile surface-imprinting method based on two-step spin-coating and photopolymerization to design highly efficient imprinted sites on polymeric films to detect trypsin (TRY). Well-distributed template imprinting is successfully achieved for maximized sensing responses by controlling the composition of functional monomers and crosslinkers in the precursor solution and the concentration of TRY in the imprinting solution. The MIP film exhibits higher sensitivity (−841 ± 65 Hz/(μg/mL)) with a coefficient of determination of 0.970 and a higher imprinting factor of 4.5 in a 0.24 µg/mL TRY solution compared to the nonimprinted polymer (NIP) film. Moreover, the limit of detection and limit of quantification are calculated to be 25.33 and 84.42 ng/mL, respectively. Finally, the selectivity coefficient is within the range of 3.90–6.78 for TRY against other proteins. These sensing properties are superior to those of the corresponding nonimprinted polymer matrix. Thus, the proposed facile surface-imprinting method is highly effective for protein imprinting with high sensitivity and selectivity. Full article

In air pollutant monitoring using sensors, moisture can adversely affect the analytical accuracy of volatile organic compounds (VOCs). Therefore, a new moisture pretreatment device (KPASS–Odor) for analyzing VOCs in the air was developed, based on frost and created by a desublimation process inside a cold tube. The performance of KPASS–Odor was compared with conventional devices (i.e., a Nafion^TM dryer and a cooler) through the measurements of low water-soluble VOCs (i.e., benzene, toluene, ethyl benzene, p-xylene, and styrene) and relatively high ones (i.e., methyl-ethyl ketone, methyl isobutyl ketone, butyl acetate, and isobutyl alcohol) using gas chromatography (GC) and sensor methods. Regarding the GC method, the recovery rates for KPASS–Odor and the cooler were >95% and >80%, respectively, at a flow rate of 500 mL/min for all compounds. For the Nafion^TM dryer, the recovery rates differed between low and high water-soluble compounds, which exhibited the rates ≥88% and ≤86%, respectively. In terms of the sensor method, the VOC recovery rates of KPASS–Odor and the Nafion^TM dryer were found to be >90% and <50%, respectively. Therefore, KPASS–Odor was determined to be the most suitable moisture pretreatment device for highly soluble VOCs of concern in this study. Full article

Nanocomposites of SmFeO₃/YFeO₃ (1:0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, and 0:1) with different molar proportions were prepared by the sol–gel method. The material’s properties were characterized by various test methods, such as scanning-electron microscopy (SEM) and X-ray photoelectron-diffraction spectrometry (XPS). The gas-sensing characteristics of the sensor were tested in darkness and under illumination using monochromatic light with various selected wavelengths. The test results show that the SmFeO₃/YFeO₃ sensor with the molar ratio of 0.4:0.6 had the highest gas response to volatile organic compound (VOC) gases and that the optimum operating temperature was lower (120 °C). The light illumination improved the sensor’s sensitivity to gas. Under the 370-nanometer light illumination, the sensor’s responses to 30 ppm of ethanol, acetone, and methanol gases were 163.59, 134.02, and 111.637, respectively, which were 1.35, 1.28, and 1.59 times higher, respectively, than those without light. The high gas sensitivity of the sensor was mainly due to the adsorption of oxygen on the material’s surface and the formation of a p–p heterojunction. The SmFeO₃/YFeO₃ sensor, which can respond to different VOC gases, can be used to detect the safety of unknown environments and provide a timely warning of the presence of dangerous gases in working environments. Full article

The synthesis of a variety of polyazamacrocyclic compounds comprising structural units of tris(3-aminopropyl)amine (TRPN) and oxadiamines, decorated with one or two fluorophore groups (dansyl or quinoline) at different nitrogen atoms, was carried out using Pd(0)-catalyzed amination. The dependence of the yields of the macrocycles on the synthetic path was observed. The spectrophotometric and fluorescent properties of the target compounds were studied, and their coordination with metal cations using UV–vis, fluorescence spectra as well as NMR titration was investigated. The stoichiometry and binding constants of several complexes with Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) were established. Three of the six studied macrocycles can be judged as prospective detectors of Zn(II) cations due to the substantial enhancement of fluorescence. Full article

Accurate and effective diagnosis and individualized management of gout can be potentially achieved by detecting uric acid (UA) and xanthine (XT) simultaneously using an easy-to-use method. Herein, we report simultaneous detection of UA and XT using a 3-dimensional (3D) macroporous gold nanoparticle-incorporated reduced graphene oxide–carbon nanotube nanocomposite (GNP/rGO-CNT). The GNP/rGO-CNT was simply prepared on a glassy carbon electrode (GCE) by one-step electrochemical deposition/co-reduction. It displayed highly sensitive and selective responses to UA and XT, showing excellent stability and good reproducibility in neutral pH. It was demonstrated that 3D GNP/rGO-CNT on GCE could detect UA and XT in human saliva and blood serum simultaneously. This GNP/rGO-CNT for simultaneous detection of UA and XT in human body fluids can be utilized for monitoring drug adherence for gout treatment, together with gout diagnosis. Full article

The development of fluorometric detection methods for toxic metal ions in real samples and inside cellular environments using fluorescent dyes has gained tremendous research interest. This work represents the design and synthesis of a 1,8-naphthalimide-based visible light absorbing fluorescence probe His-NMI-Bu showing an intramolecular charge transfer (ICT) feature. Photophysical properties of the fluoroprobe are investigated in-depth through a combination of steady-state, time-resolved spectroscopic techniques, and DFT calculation. The probe displays outstanding pH tolerance in the pH range of 5–10 as evident from UV–Vis. and fluorescence measurements. The fluoroprobe exhibits chelation with Hg²⁺-induced fluorescence attenuation via PET in the solution, thus acting as a suitable fluorescence sensor for mercury ions with LOD 0.52 µM. The high sensitivity and selectivity of the probe towards Hg²⁺ are validated from fluorescence titration with various metal ions. Banking on its intriguing solid-state emissive properties, dye-loaded filter paper-based sensing of Hg²⁺ is also developed demonstrating the sensitivity in the micromolar range. Finally, His-NMI-Bu fluorophore depicts its selective localization inside the lysosomal compartment of live cells which assists further to monitor the presence of mercury ions inside the lysosome showing similar Hg²⁺-induced fluorescence depletion. Full article

In recent years, pollution incidents caused by red tide occur frequently, and the red tide biotoxins brought by it make the food safety problem of seafood become a difficult problem to be solved urgently, which has caused great damage to the mariculture industry. Red tide toxin is also known as “shellfish toxin”. Saxitoxin (STX), is one of the strongest paralytic shellfish toxins and is also one of the most toxic marine toxins, which is extremely harmful. Aiming at the problems existing in the current research on the detection of red tide biotoxin in complex water bodies, this research developed an aptamer sensor based on hybrid chain reaction and a CRISPR-Cas9 gene editing system to detect the toxins of the clam and analyzed the feasibility of this method for the detection of the toxins of the clam. The results showed that the linear range of this method is 5.0 fM to 50 pM, and the detection limit is 1.2 fM. Meanwhile, the recovery rate of this sensor for the detection of toxins is 102.4–104.1% when applied in shellfish extract, which shows significant specificity and the reliability of this detection method. Full article

The increasing portability and accessibility of miniaturized NIR spectrometers are promoting the spread of in-field and online applications. Alongside the successful outcomes, there are also several problems related to the acquisition strategies for each instrument and to experimental factors that can influence the collected signals. An insightful investigation of such factors is necessary and could lead to advancements in experimental set-up and data modelling. This work aimed to identify variation sources when using miniaturized NIR sensors and to propose a methodology to investigate such sources based on a multivariate method (ANOVA—Simultaneous Component Analysis) that considers the effects and interactions between them. Five different spectrometers were chosen for their different spectroscopic range and technical characteristics, and samples of worldwide interest were chosen as the case study. Comparing various portable sensors is interesting since results could significantly vary in the same application, justifying the idea that this kind of spectrometer is not to be treated as a general class of instruments. Full article

This work proposes a high-performance asymmetric gold/graphene/platinum photodetector. The new photodetector, operating without bias, integrates interdigitated 100 nm spaced metallic contacts that induce a built-in potential and a short carrier path, allowing an improvement in the separation and collection of the photocarriers. A chemical vapor deposition graphene layer is transferred onto the interdigitated electrodes elaborated using high-resolution electron-beam lithography. Three devices with different side dimensions (100, 1000, and 3000 µm) are fabricated, and their photoresponsivities are evaluated at different wavelengths. The 100 µm device shows the highest photoresponsivity of 358 A/W at a 400 nm illumination. These promising results confirm the proposed design’s ability to increase the photodetector’s active area, improve light absorption, and achieve high separation and collection of photogenerated carriers. This makes it of great interest for optoelectronic applications. Full article

This paper presents a systematic study of the investigation of nanoparticle (NP) agglomerate films fabricated via depositing spark-generated Au, Ag, and Au/Ag NPs onto quartz microscope coverslips in a low-pressure inertial impactor. The primary focus of the study is to characterize these nanostructures and to examine their potential application in surface-enhanced Raman spectroscopy (SERS). The characterization of the produced nanostructures was carried out by performing optical absorbance measurements, morphology, and composition analysis, as well as testing the SERS performance of the NP films at three different excitation laser wavelengths in the visible range. The study aims to investigate the relationship between the optical properties, the morphology, and the enhancement of the produced samples at different excitations, and the results are presented and discussed. The study highlights the potential of using spark ablation and inertial impaction-based deposition as a method for producing nanoparticle films for SERS. Full article

Neurotransmitters (NTs) are known as endogenous chemical messengers with important roles in the normal functioning of central and peripheral nervous systems. Abnormal levels of certain NTs, such as dopamine, serotonin and epinephrine, have been linked with several neurodegenerative diseases (such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease). To date, various strategies have been employed for the quantitative determination of NTs, and nanocomposite materials based on conducting polymers and metal nanoparticles constitute a cornerstone for the development of electrochemical sensors with low costs, stability, fast response rates and high selectivity and sensitivity. The preparation and analytical applications of nanocomposite materials based on metal nanoparticles in the electrochemical sensing of neurotransmitters are discussed in this paper. Recent developments in the electrochemical sensing of neurotransmitters are also discussed with emphasis on the benefits brought by metal nanoparticles in improving the sensitivity of the analytical measurements. The electrochemical synthesis methods for the in situ generation of metal nanoparticles within conducting polymer layers are reviewed. The analytical applications of the nanocomposite-sensing materials towards the detection of neurotransmitters such as dopamine, epinephrine and serotonin are discussed in terms of detection and quantification limits, linear response range, sensitivity and selectivity. Full article

The aim of the present study is to evaluate the potential of mid-infrared spectroscopy in combination with two-dimensional correlation spectroscopy (2DCOS) and partial least squares discriminant analysis (PLS-DA) to monitor molecular structure evolution of milk mixtures of two species (cow and camel) during enzymatic coagulation. Molecular structure changes and texture characteristics were investigated on five different milk formulations by mixing camel milk (CaM) and cow milk (CM) (i.e., CaM, CaM3:CM1, CaM1:CM1, CaM1:CM3, and CM, (v/v)). Regarding MIR spectroscopy, two spectral regions were considered to monitor milk coagulation, the fatty acid acyl-chain region (3000–2800 cm⁻¹) and the protein region (1700–1500 cm⁻¹). Different formulation dissimilarities were revealed through the synchronous 2DCOS spectra and their respective auto-peaks. Moreover, using the cross-peak symbols of the synchronous and asynchronous spectra helps to establish the sequence of molecular structure modifications during coagulation. Finally, the analysis of the 2DCOS-MIR synchronous and asynchronous maps by PLS-DA gave good discriminant accuracy (88 to 100%) between each formulation. Those results highlighted that different synchronous and asynchronous chemical phenomena occurred during milk coagulation depending on the milk formulation. Texture attributes were influenced by camel milk ratio in mixtures based on the initial composition of milks. Samples containing more than 50% of CM showed significantly higher hardness compared to pure CaM and CaM3:CM; however, CM gel displayed lower springiness contrary to CaM. Textural characteristics of the resulted gels also confirmed that 2DCOS MIR observations are consistent with textural observations of the gels obtained after milk mixtures coagulation. Full article

Herein, two new iridium(III) complexes, namely Ir2 and Ir3, with a phenyl or triphenylamine (TPA) moiety at the 4-position of the phenyl ring at 2-phenylbenzothiazole, have been synthesized, and their emission properties have been studied systematically compared with the non-substituted complex Ir1. These three complexes exhibit aggregation-induced emission (AIE) in H₂O/CH₃CN. The TPA-substituted complex Ir3 shows the highest AIE activity. All complexes can be used as sensors to detect picric acid (PA) in water. The Stern–Volmer constant (K_SV) of Ir3 for the detection of PA was determined to be 1.96 × 10⁶ M⁻¹, with a low limit of detection of 2.52 nM. Proton nuclear magnetic resonance spectra, high-resolution mass spectrometry analysis, and density function theory calculations confirm that the emission quenching mechanism of Ir3 is caused by photo-induced electron transfer. Furthermore, the efficient detection of PA in natural water proves that Ir1–Ir3 can be used as promising sensors in the natural environment. These results suggest that the AIE-active iridium(III) complexes can be used to detect PA under environment-friendly conditions. Full article

Ochratoxin A (OTA) is considered the most toxic member of the ochratoxin group. Herein, a novel label-free electrochemical sensor based on the horseradish peroxidase (HRP) enzyme is developed for OTA detection. The HRP enzyme was covalently immobilized on the working electrode of a planar boron-doped diamond (BDD) electrochemical microcell previously covered with diazonium film and grafted with single-walled carbon nanotubes (SWCNTs). Each surface modification step was evaluated by cyclic voltammetry and scanning electron microscopy. Square wave voltammetry was used for the detection of OTA. The linear working range of the biosensors ranged between 10⁻¹⁴ and 0.1 M, with a limit of detection (LOD) of 10 fM, an RSD equal to 5%, and a sensitivity of 0.8 µA per decade. In addition, the sensor showed good selectivity in the presence of OTA analogs; it was validated in samples such as corn, feed, and wheat. The metrological performance of the present sensor makes it a good alternative for OTA detection. Full article

Succinylcholine (SUX) is a clinical anesthetic that induces temporary paralysis and is degraded by endogenous enzymes within the body. In high doses and without respiratory support, it results in rapid and untraceable death by asphyxiation. A potentiometric thread-based method was developed for the in-field and rapid detection of SUX for forensic use. We fabricated the first solid-contact SUX ion-selective electrodes from cotton yarn, a carbon black ink, and a polymeric ion-selective membrane. The electrodes could selectively measure SUX in a linear range of 1 mM to 4.3 $\mathsf{\mu }$M in urine, with a Nernstian slope of 27.6 mV/decade. Our compact and portable yarn-based SUX sensors achieved 94.1% recovery at low concentrations, demonstrating feasibility in real-world applications. While other challenges remain, the development of a thread-based ion-selective electrode for SUX detection shows that it is possible to detect this poison in urine and paves the way for other low-cost, rapid forensic diagnostic devices. Full article

In this work, the stability, electrical conductivity, and versatility of graphite-based inks were taken advantage of to fabricate a nitrate potentiometric sensor. One other key property that was exploited for the design of an ion-selective electrode was the hydrophobicity of graphite. This prevented the formation of a water layer between the solid contact and the polymeric selective membrane. Moreover, given the use of printing technologies for electrode fabrication, it was possible to easily miniaturize the sensors and achieve lower fabrication costs. In this article, a printed sensor, composed of a graphite working electrode and a Ag/AgCl reference electrode, is presented and thoroughly characterized. The working electrode was modified with a well-known PVC-ionophore membrane, and the reference electrode was protected with a PVB-NaCl saturated membrane. It showed almost-Nernstian sensitivity of −(55.4 ± 0.7) mV/dec to NO₃⁻, stability of up to 25 days of operation, limit of detection of 0.204 ± 0.009 mM, and repeatability of 99.02 % (N = 3). Coupled with its high selectivity compared with other anions, this low-cost, mass-producible sensor is a great alternative for environmental and industrial applications. Full article