Search Results (46)

This paper presents the design and evaluation of a fluorescent probe based on fluorescein hydrazide for the selective detection of hypochlorite (ClO⁻), bromide (Br⁻), and iodide (I⁻) ions in solution. The starting chemosensor, fluorescein hydrazide, is suitable for detecting hypochlorite anions in solution, as observed for the first time. The Br⁻ and I⁻ ions could be discovered after activating the probe with hypochlorite. Upon interaction with ClO⁻ ions, the proposed probe exhibits a significant increase in fluorescence emission, a sharp rise in absorbance, and a distinct color change, which is attributed to the conversion from the spirolactam closed form to the open form of the fluorescein ring. ClO⁻ and Br⁻ ions added together were found to brominate the probe in an acetonitrile–water mixture, resulting in a pronounced bathochromic shift in both absorption and emission spectra. Notably, the combination of ClO⁻ and I⁻ was more effective in cleaving the spirolactam ring than hypochlorite alone. Quantum chemical calculations were used to understand the detection mechanism of Br and I ions in a probe–hypochlorite mixture. The probe demonstrated exceptional selectivity and rapid response towards the target analytes, with detection limits determined to be 2.61 μM for ClO⁻, 66 nM for Br⁻, and 13 nM for I⁻. Furthermore, it successfully monitored fluctuations in ClO⁻, Br⁻, and I⁻ concentrations within complex systems, highlighting its potential application in environmental and biological monitoring. Full article

Two positively charged amphiphilic benzothiadiazoles (2–3), functionalized with 2,3-dimethylbenzo[d]thiazol-3-ium and 2,3-dimethylnaphtho[2,1-d]thiazol-3-ium acceptor moieties, synthesized earlier in our research group, from 7-(4-methoxyphenyl)benzo[c][1,2,5]thiadiazole-4-carbaldehyde (1), were evaluated concerning their optical chemosensory capabilities towards different anions in DMSO and in a DMSO/water (75:25) solution. Spectrophotometric and spectrofluorimetric titrations were performed, demonstrating that both compounds were highly sensitive to cyanide in DMSO. Compound 2 showed fluorescence quenching at 657 nm with 5 equivalents of CN⁻, while compound 3 displayed a decrease in absorption at 480 nm and emission at 666 nm with seven equivalents of CN⁻ in DMSO solution. Nevertheless, in the DMSO/water mixture, the sensitivity decreased, requiring 50–70 equivalents of cyanide for fluorescence quenching. Full article

Rationally designing and synthesizing chemosensors capable of simultaneously detecting both anions and cations via water content modulation is challenging. In this study, we synthesized and characterized a novel triazine calixarene derivative-based iodide and copper ion-selective fluorescent “turn-off” sensor. This dual-channeled fluorescent probe is able to recognize Cu²⁺ and I⁻ ions simultaneously in aqueous systems. The fluorescent sensor s4 was synthesized by displacement reaction of acridine with 1, 3-bis (dichloro-mono-triazinoxy) benzene in acetonitrile. Mass spectrometry (MS), UV-vis, and fluorescence spectra were acquired to characterize the fluorescence response of s4 to different cations and anions, while infrared (IR) spectroscopy and isothermal titration calorimetry (ITC) were employed to study the underlying selectivity mechanism of s4 to Cu²⁺ and I⁻. In detail, s4 displayed extremely high sensitivity to Cu²⁺ with over 80% fluorescence decrement caused by the paramagnetic nature of Cu²⁺ in the aqueous media. The reversible fluorescence response to Cu²⁺ and the responses to Cu²⁺ in the solution of other potential interferent cations, such as Li⁺, Na⁺, K⁺, Ca²⁺, Cd²⁺, Zn²⁺, Sr²⁺, Ni²⁺, Co²⁺ were also investigated. Probe s4 also exhibited very good fluorescence selectivity to iodide ions under various anion (F⁻, Cl⁻, Br⁻, NO₃⁻, HSO₄⁻, ClO₄⁻, PF₆⁻, AcO⁻, H₂PO₄⁻) interferences. In addition to the fluorescent response to I⁻, s4 showed a highly selective naked-eye-detectable color change from colorless to yellow with the other tested anions. Full article

A primary challenge in the further development of anion sensors in real water samples of environmental concern is the need for highly water-soluble compounds that are able to detect low concentrations of analytes. Small-molecule sensors can mitigate solubility constraints and highly aromatic or conjugated systems may provide a new way to recognize target analytes with high sensitivity and/or selectivity. Organic aggregates that have the ability to form large frameworks can exhibit aggregated-induced emissions to detect target analytes, and their coagulation can provide enhanced detection via colorimetric or fluorescent measurements. This review aims to draw attention to the emerging area of small-molecule organic chemosensors that utilize aggregation to detect environmentally detrimental anions in an aqueous solution. A number of mechanisms of interaction for anion recognition are recognized and discussed here, including electrostatic interactions, covalent bond formation, hydrophobic interactions, and even complexation. Full article

Recently, 4-(pyrrol-1-yl)pyridine has been found to act as a supramolecular chemodosimeter, sensing nitrite ions in an aqueous solution with naked eye detection and a low limit of detection of 0.330 ppm. This work explores the anion-sensing properties of related derivatives, 4-(2,5-dimethyl-pyrrol-1-yl)pyridine and 4-(2,4-dimethyl-pyrrol-1-yl)pyridine, and provides a comparison with the parent compound. These molecules are determined to be effective sensors for nitrite ions with limits of detection of 1.06 ppm and 1.05 ppm, respectively. The high sensitivity and selectivity to nitrite remain even in the presence of competing anions such as SO₃²⁻, NO₃²⁻, PO₄³⁻, SO₄²⁻, Cl⁻, F⁻, I⁻, Br⁻, AcO⁻, and CN⁻. Analogous to the 4-(pyrrol-1-yl)pyridine system, the sensing mechanism appears to be the result of changes in the supramolecular aggregate system upon the interaction of an anion; this is further explored through dynamic light scattering, the Tyndall effect, and NMR spectroscopy. The two methylated derivative systems reported herein, 4-(2,5-dimethyl-pyrrol-1-yl)pyridine and 4-(2,4-dimethyl-pyrrol-1-yl)pyridine, are shown to affect the size of the supramolecular system and provide further insight into the unique mechanism of action. Full article

A tert-butyldiphenylsilyl-containing polyimide (PI-OSi) has been established as a colorimetric and ratiometric chemosensor for rapid detecting fluoride ions (F⁻). The UV-vis absorbance ratio value (A₃₂₂/A₂₈₈) of PI-OSi in a DMF solution displays a wide linear range change to F⁻ concentrations with a detection limit (DL) value of 2.13 μM. Additionally, adding incremental amounts of F⁻ to a DMF solution of PI-OSi shows an immediate color change to yellow and finally to green from colorless. More interestingly, the resulting PI-OSi plus F⁻ system (PI-OSi·F) could detect trace water in DMF. The A₂₉₂/A₃₂₂ value of PI-OSi·F almost linearly increases with low water content, which suggests convenient quantitative sensing of trace water content in DMF. The DL value of PI-OSi·F for sensing water in DMF is determined to be 0.00149% (v/v). The solution color of PI-OSi·F returns to colorless when the water content increases, indicating that PI-OSi·F can conveniently estimate water content in DMF by naked-eye detection. The detection mechanisms confirmed by an ¹H NMR study and a DFT calculation involve a F⁻-induced desilylation reaction of PI-OSi to form phenolate anion followed by protonation with trace water. Finally, PI-OSi film was fabricated for the colorimetric detection of F⁻ and water in CH₃CN. Full article

Bearing in mind the interest in the development and application of amino acids/peptides as bioinspired systems for sensing, a series of new phenylalanine derivatives bearing thiosemicarbazone and hydrazone units at the side chain were synthesised and evaluated as fluorimetric chemosensors for ions. Thiosemicarbazone and hydrazone moieties were chosen because they are considered both proton-donor and proton-acceptor, which is an interesting feature in the design of chemosensors. The obtained compounds were tested for the recognition of organic and inorganic anions (such as AcO⁻, F⁻, Cl⁻, Br⁻, I⁻, ClO₄⁻, CN⁻, NO₃⁻, BzO⁻, OH⁻, H₂PO₄⁻ and HSO₄⁻) and of alkaline, alkaline-earth, and transition metal cations, (such as Na⁺, K⁺, Cs⁺, Ag⁺, Cu⁺, Cu²⁺, Ca²⁺, Cd²⁺, Co²⁺, Pb²⁺, Pd²⁺, Ni²⁺, Hg²⁺, Zn²⁺, Fe²⁺, Fe³⁺ and Cr³⁺) in acetonitrile and its aqueous mixtures in varying ratios via spectrofluorimetric titrations. The results indicate that there is a strong interaction via the donor N, O and S atoms at the side chain of the various phenylalanines, with higher sensitivity for Cu²⁺, Fe³⁺ and F⁻ in a 1:2 ligand-ion stoichiometry. The photophysical and metal ion-sensing properties of these phenylalanines suggest that they might be suitable for incorporation into peptide chemosensory frameworks. Full article

Cations and anions are indispensable resources for the development of nature and modern industry and agriculture, and exploring more efficient technology to monitor them is urgently needed. A multifunctional fluorescent probe based on 1,8-naphthalimide, N-(2-thiophenhydrazide)acetyl-4-morpholine-1,8-naphthalimide (TMN), was successfully designed and synthesized for the detection of Co²⁺, F⁻, and CN⁻, with N-carboxymethyl-4-morpholine-1,8-naphthalimide and thiophene-2-carbohydrazide as starting materials. TMN displayed superior stability in MeCN with an “on–off” mode towards Co²⁺, F⁻, and CN⁻ by the naked eye. The linear response ranges of TMN were 0–3 and 4–19 μM with a detection limit of 0.21 μM for detecting Co²⁺, 0–5 and 5–22 μM with a detection limit of 0.36 μM for F⁻, and 0–10 and 10–25 μM with a detection limit of 0.49 μM for CN⁻. TMN could also recognize Co²⁺, F⁻, and CN⁻ in real samples. Finally, the possible sensing mechanisms of TMN for detecting Co²⁺, F⁻, and CN⁻ were deeply investigated. These results implied that TMN could be a potential chemosensor for monitoring metal cations and anions sensitively and selectively and could be used in real sample detection. Full article

A dinitrophenol-based colorimetric chemosensor sequentially sensing Cu²⁺ and S²⁻, HDHT ((E)-2-(2-(2-hydroxy-3,5-dinitrobenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium), was designed and synthesized. The HDHT selectively detected Cu²⁺ through a color change of yellow to colorless. The calculated detection limit of the HDHT for Cu²⁺ was 6.4 × 10⁻² μM. In the interference test, the HDHT was not considerably inhibited by various metal ions in its detection of Cu²⁺. The chelation ratio of the HDHT to Cu²⁺ was determined as 1:1 by using a Job plot and ESI-MS experiment. In addition, the HDHT–Cu²⁺ complex showed that its color selectively returned to yellow only in the presence of S²⁻. The detection limit of the HDHT–Cu²⁺ complex for S²⁻ was calculated to be 1.2 × 10⁻¹ μM. In the inhibition experiment for S²⁻, the HDHT–Cu²⁺ complex did not significantly interfere with other anions. In the real water-sample test, the detection performance of the HDHT for Cu²⁺ and S²⁻ was successfully examined. The detection features of HDHT for Cu²⁺ and the HDHT–Cu²⁺ for S²⁻ were suggested by the Job plot, UV–Vis, ESI-MS, FT-IR spectroscopy, and DFT calculations. Full article

Improvements in the design of receptors for the detection and quantification of anions are desirable and ongoing in the field of anion chemistry, and remarkable progress has been made in this direction. In this regard, the development of luminescent chemosensors for sensing anions is an imperative and demanding sub-area in supramolecular chemistry. This decade, in particular, witnessed advancements in chemosensors based on ruthenium and iridium complexes for anion sensing by virtue of their modular synthesis and rich chemical and photophysical properties, such as visible excitation wavelength, high quantum efficiency, high luminescence intensity, long lifetimes of phosphorescence, and large Stokes shifts, etc. Thus, this review aims to summarize the recent advances in the development of ruthenium(II) and iridium(III)-based complexes for their application as luminescent chemosensors for anion sensing. In addition, the focus was devoted to designing aspects of polypyridyl complexes of these two transition metals with different recognition motifs, which upon interacting with different inorganic anions, produces desirable quantifiable outputs. Full article

A new Near InfraRed (NIR) fluorescent chemosensor for metal ions and anions is herein presented. The fluorophore is based on a styrylflavylium dye, a synthetic analogue of the natural anthocyanin family, with a di-(2-picolyl)amine (DPA) moiety as the metal chelating unit. The substitution pattern of the styrylflavylium core (with tertiary amines on positions 7 and 4′) shifts the optical properties of the dye towards the NIR region of the electronic spectra, due to a strong push-pull character over the π-conjugated system. The NIR chemosensor is highly sensitive to the presence of Zn²⁺, which induces a strong CHelation Enhanced Fluorescence (CHEF) effect upon binding to the DPA unit (2.7 fold increase). The strongest competing ion is Cu²⁺, with a complete fluorescence quenching, while other metals induce lower responses on the optical properties of the chemosensor. Subsequent anion screening of the Zn²⁺-chemosensor coordination compound has demonstrated a distinct selectivity towards adenosine 5′-triphosphate (ATP) and adenosine 5′-diphosphate (ADP), with high association constants (K ~ 10⁶ M⁻¹) and a strong CHEF effect (2.4 and 2.9 fold fluorescence increase for ATP and ADP, respectively). Intracellular studies with the Zn²⁺-complexed sensor showed strong luminescence in the cellular membrane of Gram^– bacteria (E. coli) and mitochondrial membrane of mammalian cells (A659), which highlights its possible application for intracellular labelling. Full article

A novel diamino triazine based 1,8-naphthalimide (NI-DAT) has been designed and synthesized. Its photophysical properties have been investigated in different solvents and its sensory capability evaluated. The fluorescence emission of NI-DAT is significantly impacted by the solvent polarity due to its inherent intramolecular charge transfer character. Moreover, the fluorescence emission quenched at higher pH as a result of photo-induced electron transfer (PET) from triazine moiety to 1,8-naphthalimide after cleaving hydrogen bonds in the self-associated dimers. Furthermore, the new chemosensor exhibited a good selectivity and sensitivity towards Hg²⁺ among all the used various cations and anions in the aqueous solution of ethanol (5:1, v/v, pH = 7.2, Tampon buffer). NI-DAT emission at 540 nm was quenched remarkably only by Hg²⁺, even in the presence of other cations or anions as interfering analytes. Job’s plot revealed a 2:1 stoichiometric ratio for NI-DAT/Hg²⁺ complex, respectively. 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

A simple and cost-effective optical sensing system based on quinizarin fluorescent dye (QZ) for the selective and reversible sensing of CH₃COO⁻ anions is reported. The anion binding affinity of QZ towards different anions was monitored using electronic absorption and fluorescence emission titration studies in DMSO. The UV-visible absorption spectrum of QZ showed a decrease in the intensity of the characteristic absorption peaks at λ = 280, 323, and 475 nm, while a new peak appeared at λ = 586 nm after the addition of CH₃COO⁻ anions. Similarly, the initial strong emission intensity of QZ was attenuated following titration with CH₃COO⁻ anions. Notably, similar titration using other anions, such as F⁻, Cl⁻, I⁻, NO₃⁻, NO₂^−, and H₂PO₄^-, caused no observable changes in both absorption and emission spectra. The selective sensing of CH₃COO⁻ anions was also reflected by a sharp visual color change from bright green to faint green under room light. Further, the binding was found to be reversible, and this makes QZ a potential optical and colorimetric sensor for selective, reversible, and ppb-level detection of CH₃COO⁻ anions in a DMSO medium. Full article

The search for accurate and sensitive methods to detect chemical substances, namely cations and anions, is urgent and widely sought due to the enormous impact that some of these chemical species have on human health and on the environment. Here, we present a new platform for the efficient sensing of Cu²⁺ and Li⁺ cations. For this purpose, two novel photoactive diketopyrrolopyrrole-rhodamine conjugates were synthesized through the condensation of a diketopyrrolopyrrole dicarbaldehyde with rhodamine B hydrazide. The resulting chemosensors 1 and 2, bearing one or two rhodamine hydrazide moieties, respectively, were characterized by ¹H and ¹³C NMR and high-resolution mass spectrometry, and their photophysical and ion-responsive behaviours were investigated via absorption and fluorescence measurements. Chemosensors 1 and 2 displayed a rapid colorimetric response upon the addition of Cu²⁺, with a remarkable increase in the absorbance and fluorescence intensities. The addition of other metal ions caused no significant effects. Moreover, the resulting chemosensor-Cu²⁺ complexes revealed to be good probes for the sensing of Li⁺ with reversibility and low detection limits. The recognition ability of the new chemosensors was investigated by absorption and fluorescence titrations and competitive studies. Full article