Search Results (14)

The design, characterization, and analytical application of a green optical sensor for the selective determination of Fe(II) ions is proposed. The sensor is based on the immobilization of the chromogenic reagent picolinaldehyde salicyloylhydrazone (SHPA) within a polymer inclusion membrane. To reduce solvent usage, the reagent was synthesized using a green mechanochemical procedure. The components for sensor preparation were optimized with a sequential simplex method and the optimal composition was found to be 0.59 g cellulose triacetate (base polymer), 0.04 g SHPA (chemosensor reagent), 4.9 mL dibutyl phthalate (plasticizer), and 38 mL dichloromethane (solvent). The conditions of iron analysis were also optimized resulting in pH 6 for aqueous solution, 90 min exposure time and 10 min short-term stability. The optical sensor showed a linear range from the limit of detection (0.48 µmol L⁻¹) to 54 µmol L⁻¹ Fe(II). The precision of the method was found to be 1.44% and 1.19% for 17.9 and 45 µmol L⁻¹ Fe(II), respectively. The characteristics of the sensor allowed the design of a Fe(II)/Fe(III) speciation scheme. The methodology was successfully applied to the determination of iron in food preservatives, food additives, and dietary supplement. Additionally, the Fe speciation scheme was successfully applied to an agricultural fertilizer. Full article

A carboxylic acid azo dye, Dabcyl, was synthesized and evaluated as a colorimetric chemosensor for metal cations with biological and environmental importance. The dye was prepared in high yield and characterized by ¹H and ¹³C NMR and UV–Vis absorption spectroscopies. A preliminary chemosensing study showed that Dabcyl displayed a marked color change from light yellow to pink, for Hg²⁺, Fe²⁺, Pd²⁺, Sn²⁺ and Al³⁺ in acetonitrile solution. Consequently, spectrophotometric titrations were carried out for this dye with selected cations, which clearly indicated that Dabcyl has potential application as a chromogenic probe for the cations under study with remarkable sensitivity and with a marked color change. Full article

Herein, we report the synthesis and chromo-fluorogenic behavior of a BODIPY derivative. The BODIPY core was functionalized with a phenyl group at the meso-position and a formyl group at position 2 introduced through the Vilsmeier Haack reaction. The compound showed an absorption band at 492 nm and an emission band at 508 nm, with a Φ_F = 0.84. The evaluation of the chemosensing ability of the BODIPY was investigated in the presence of several anions with environmental and biomedical relevance, and a simultaneous colorimetric and fluorimetric response was observed for cyanide and fluoride anions. Full article

For the detection of Cd(II) in aquatic media, a novel dicyanomethylene dihydrofuran hydrazone(DCDHFH)-based colorimetric chemosensor was developed. DCDHFH was prepared by an azo-coupling process involving the diazonium chloride of 2, 4-dichloroaniline and a dicyanomethylene dihydrofuran heterocyclic moiety bearing an active methyl group. The DCDHFH chromophore showed strong solvatochromism depending on solvent polarity due to electronic delocalization. The pH sensory effects of the DCDHFH chromophore were also explored. DCDHFH could be used to identify Cd(II) in the presence of other competitive metals, as indicated by variations in color and absorbance spectra. In the presence of cadmium ions, the synthesized DCDHFH probe with hydrazone recognition moiety exhibited a significant sensitivity and selectivity to cadmium ions at the ppm concentration level (10–250 ppm). A DCDHFH-immobilized paper test strip was also prepared and effectively used for the detection of cadmium in aqueous media at various concentrations. According to CIE Lab’s criteria, colorimetric strength (K/S), and the UV–Vis absorbance spectra, the cadmium detection abilities of the DCDHFH-immobilized paper strips were evaluated. The optimal pH range for the determination of Cd(II) was monitored in the area of 5.5–6.3, with a fast chromogenic change from yellow to red relying on the Cd(II) concentration. The deposition of dicyanomethylene dihydrofuran hydrazone onto the paper strip’s surface was studied by scanning electron microscopy (SEM). Full article

Monitoring and detection of cyanide are of crucial interest as the latter plays versatile roles in many biological events, is ubiquitous in environment, and responsible for several acute poisoning and adverse health effects if ingested. We describe herein the synthesis and characterization of novel phenothiazine-based push–pull chromogenic chemosensors suitable for naked eye cyanide sensing. Indeed, specific detections were achieved for cyanide with a LOD of ca 9.12 to 4.59 µM and, interestingly, one of the new chemosensors has also revealed an unprecedented affinity for acetate with a LOD of ca 2.68 µM. Moreover, as proof of concept for practical applications, a paper test strip was prepared allowing its use for efficient qualitative naked eye cyanide sensing. Full article

Ferene is the most commonly used chromogenic agent for the determination of serum iron in blood. In this work we have successfully synthesized Ferene-S-conjugated silver nanoparticles (Ferene-S-AgNPs) for the first time characterized by UV-visible, Fourier-Transform Infrared Spectroscopy (FTIR), and Matrix-Assisted Laser Desorption/Ionization-Time Of Flight (MALDI-TOF) mass spectrometry techniques. Particle size of the synthesized nanoparticles was determined by atomic-force microscopy and scanning electron microscopy techniques with size ranges from 10–90 nm in diameter. Ferene-S-AgNPs were explored for their chemosensing potential with various metal ions such as Sb³⁺, Pb²⁺, Ca²⁺, Fe²⁺, K⁺, Co²⁺, Ba²⁺, V⁵⁺, Cu⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Fe³⁺, Mg²⁺, Mn²⁺, Al³⁺, and Cr³⁺. Ferene-S-AgNPs were found to show selective quenching effects and slight bathochromic shifts to the surface plasmon resonance absorption band after treatment with Fe²⁺. Furthermore, the developed chemosensor also exhibited substantial selectivity towards Fe²⁺ in the presence of other competitive ions. We observed that Ferene-S-AgNPs mimic the selectivity of the parent compound of Ferene towards Fe²⁺. The system obeyed Beer’s law over concentration ranges of 110–190 nM. The detection limit was found to be 110 nM. Full article

Small molecule-based chromogenic and fluorogenic probes play an indispensable role in many sensing applications. Ideal optical chemosensors should provide selectivity and sensitivity towards a variety of analytes. Synthetic accessibility and attractive photophysical properties have made squaraine dyes an enticing platform for the development of chemosensors. This review highlights the versatility of modular assemblies of squaraine-based chemosensors and chemodosimeters that take advantage of the availability of various structurally and functionally diverse recognition motifs, as well as utilizing additional recognition capabilities due to the unique structural features of the squaraine ring. Full article

In this work, we prepared a fluorescein hydrazide-appended Ni(MOF) (Metal–Organic Framework) [Ni₃(BTC)₂(H₂O)₃]·(DMF)₃(H₂O)₃ composite, FH@Ni(MOF). This composite was well-characterized by PXRD (powder X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), N₂ adsorption isotherm, TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), and FESEM (field emission scanning electron microscopy). This composite was then tested with different heavy metals and was found to act as a highly selective and sensitive optical sensor for the Hg²⁺ ion. It was found that the aqueous emulsion of this composite produces a new peak in absorption at 583 nm, with a chromogenic change to a pink color visible to the naked eye upon binding with Hg²⁺ ions. In emission, it enhances fluorescence with a fluorogenic change to green fluorescence upon complexation with the Hg²⁺ ion. The binding constant was found to be 9.4 × 10⁵ M⁻¹, with a detection limit of 0.02 μM or 5 ppb. This sensor was also found to be reversible and could be used for seven consecutive cycles. It was also tested for Hg²⁺ ion detection in practical water samples from ground water, tap water, and drinking water. Full article

Electrospun nanofibers (ENFs) are remarkable analytical tools for quantitative analysis since they are inexpensive, easily produced in uniform homogenous mats, and provide a high surface area-to-volume ratio. Taking advantage of these characteristics, a near-infrared (NIR)-dye was doped as chemosensor into ENFs of about 500 nm in diameter electrospun into 50 µm thick mats on indium tin oxide (ITO) supports. The mats were made of cellulose acetate (CA) and used as a sensor layer on optical dipsticks for the determination of biogenic amines (BAs) in food. The ENFs contained the chromogenic amine-reactive chameleon dye S0378 which is green and turns blue upon formation of a dye-BA conjugate. This S_N1-reaction of the S0378 dye with various BAs was monitored by reflectance measurements at 635 nm where the intrinsic absorption of biological material is low. The difference of the reflectance before and after the reaction is proportional to BA levels from 0.04–1 mM. The LODs are in the range from 0.03–0.09 mM, concentrations that can induce food poisoning but are not recognized by the human nose. The calibration plots of histamine, putrescine, spermidine, and tyramine are very similar and suggesting the use of the dipsticks to monitor the total sample BA content. Furthermore, the dipsticks are selective to primary amines (both mono- and diamines) and show low interference towards most nucleophiles. A minute interference of proteins in real samples can be overcome by appropriate sample pretreatment. Hence, the ageing of seafood samples could be monitored via their total BA content which rose up to 21.7 ± 3.2 µmol/g over six days of storage. This demonstrates that optically doped NFs represent viable sensor and transducer materials for food analysis with dipsticks. Full article

The paper presents the results of the study of the possibilities of using color metal complexes to detect the presence of chemical warfare agents (CWA) in liquid or aerosol form. Aluminon/Fe³⁺ and Eriochrome Cyanine R/Cu²⁺ coordination complexes and their ability to detect CWA in liquid phase are discussed. Detection systems have been demonstrated on instances of simple detection papers exposed to drops of real CWAs. Detection papers showed a positive response to G-series nerve agents and vesicant lewisite. Other liquid CWA do not interfere and the systems are also resistant to common organic solvents and a wide range of industrial chemicals. Full article

This work provides a summary of our results in the area of the experimental development of detection paper for the detection of liquid phase chemical warfare agents (drops, aerosol), the presence of which is demonstrated by the development of characteristic coloring visible to the naked eye. The basis of the detection paper is a cellulose carrier saturated with the dithienobenzotropone monomer (RM1a)–chromogenic chemosensor sensitive to nerve agents of the G type, blister agent lewisite, or choking agent diphosgene. We achieve a higher coloring brilliance and the limit certain interferences by using this chemosensor in the mix of the o-phenylendiamine-pyronine (PY-OPD). We prove that the addition of the Bromocresol Green pH indicator even enables detection of nerve agents of the V type, or, nitrogen mustards, while keeping a high stability of the detection paper and its functions for other chemical warfare agents. We resolve the resistance against the undesirable influence of water by providing a hydrophobic treatment of the carrier surface. Full article

The zinc(II) ion forms stable complexes with a wide variety of ligands, but those related to Schiff-bases are among the most largely investigated. This review deals with the peculiar aggregation characteristics of Zn(II) Schiff-base complexes from tetradentate N₂O₂ salen-type ligands, L, derivatives from salicylaldehydes and 1,2-diamines, and is mostly focused on their spectroscopic properties in solution. Thanks to their Lewis acidic character, ZnL complexes show interesting structural, nanostructural, and aggregation/deaggregation properties in relation to the absence/presence of a Lewis base. Deaggregation of these complexes is accompanied by relevant changes of their spectroscopic properties that can appropriately be exploited for sensing Lewis bases. Thus, ZnL complexes have been investigated as chromogenic and fluorogenic chemosensors of charged and neutral Lewis bases, including cell imaging, and have shown to be selective and sensitive to the Lewis basicity of the involved species. From these studies emerges that these popular, Lewis acidic bis(salicylaldiminato)Zn(II) Schiff-base complexes represent classical coordination compounds for modern applications. Full article

[m.n] Multinuclear ferrocenophanes prepared by aza-Wittig reaction of bisiminophosphoranes derived from 1,1'-diazidoferrocene and isophthaladelhyde or 2,5-diformylthiophene, behave as efficient electrochemical and chromogenic chemosensor molecules for Zn²⁺, Pb²⁺, and Hg²⁺ metal cations. Whereas the OSWV of receptor 3, bearing two m-phenylene units in the bridges, display one oxidation peak, receptor 4 incorporating two thiophene rings in the bridges, exhibits two well-separated oxidation peaks. In both receptors only the addition of Zn²⁺, Pb²⁺, and Hg²⁺ metal cations induced a remarkable anodic shift of ferrocene/ferrocenium redox couple. Likewise, in the absorption spectra of these receptors the low energy band is red-shifted by Δλ = 165 − 209 nm, and these changes promoted a significant color changes which could be used for the naked eye detection of these metal cations. The coordination modes for two representative cases were unveiled by DFT calculations that show an unsual coordination in the [4₂Pb]²⁺ complex with the Pb²⁺ cation in a distorted cubic N₄S₄ donor cage. Full article

A test paper for high-selectivity detecting Hg²⁺ ions in mixed acetonitrile-watersolutions has been achieved using a bis(ferrocenyl) azine, as chromogenic chemosensormolecule, and a solid cellulose fibre, as a substrate. Depending on the amount of mercuryions in contact with the detecting molecule a spectacular color change in the celluloseindicator is produced, being possible to determine the concentration of Hg²⁺ ions either bynaked eye or spectroscopically. Full article