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In this review, we present a systematic and comprehensive summary of the recent developments in the synthetic strategies of 2-(2-hydroxyarylsubstituted)-benzothiazole (HBT) framework along with incorporation of various substituents on phenolic and benzothiazole rings which affect the emission process. The literature, spanning the years 2015–2024, on excited-state intramolecular proton transfer (ESIPT)-based studies of HBT derivatives comprising the effects of solvent polarity, substituents, and extended conjugation on fluorophores has been searched. ESIPT, intramolecular charge transfer, and aggregation-induced emissions enable these fluorescent probes to specifically interact with analytes, thereby altering their luminescence characteristics to achieve analyte detection. These fluorescent probes exhibit large Stokes shifts, high quantum yields, and excellent color transitions. Finally, the applications of HBTs as ESIPT-based fluorescent probes for the detection of cations, anions, and biomolecules have been summarized. We anticipate that this review will provide a comprehensive overview of the current state of research in this field and encourage researchers to develop novel ESIPT-based fluorophores with new applications. [ABSTRACT FROM AUTHOR]

Tetracycline (TC) is a commonly used antibiotic in human therapy and animal husbandry. Public concerns about TC residues inflated due to their negative impact on the environment, food, and human health concerns. To ensure human health and safety, there is a need for fluorogenic chemosensors that can easily detect TC antibiotics with high selectivity and sensitivity in the aqueous medium. This mini‐review discusses the progress and achievements in several fluorometric antibiotic tetracycline detection methods. Fluorogenic chemosensors for tetracycline antibiotics with easy‐to‐use, high selectivity, and sensitivity have been essentially required to regulate food safety and secure human health and safety. Moreover, we gave more attention to the practical applicability of chemosensors for tetracycline antibiotics in food and water quality assessment. This article starts with a section that constitutes an overview of the problems of antibiotics and the typical features of traditional techniques of antibiotic detection. It then goes on to describe up‐to‐date optical methods for the selective detection and efficient removal of TC. These methods involve a variety of platforms, like tetraphenylethylene polymers, metal complexes, self‐assembled CuNCs, and hydrogel. The article also discusses the practical applicability of chemosensors for tetracycline antibiotics in food and water quality. [ABSTRACT FROM AUTHOR]

Cerium accumulation in the environment increases the health risk of humans due to the unavoidable usage of cerium in our day-to-day life. Therefore, developing a chemosensory scaffold for the rapid detection of cerium is necessary. With the objective of assessing and understanding the various factors involved in the sensing of Ce4+, this review consolidates all the 34 chemosensory molecules, mechanisms, techniques, matrices and discusses all the relevant parameters comprehensively. 23 out of 34 probes are directly utilizing the oxidative capability of Ce4+ for the detection and undergo color changes. Probes that are demonstrated with metal enhanced fluorescence exhibit lower detection limits. Based on the survey, we suggest that the investigation of the rigidity of "probe- Ce4+" and its impact on the emission/quenching should be considered for designing an efficient Ce4+ sensor. This is the first review report on the Ce4+ sensors and it could serve as a one-point reference source. [ABSTRACT FROM AUTHOR]

Utilizing a high-dilution condition method, a new aza-oxo macrocycle, referred to as L, was synthesized as a chemosensor. The chemosensing capabilities of L were thoroughly investigated using fluorescence studies. The obtained results demonstrate that L effectively responds to the presence of zinc ions, leading to a significant increase in fluorescence intensity. Comparative studies were conducted to investigate the impact of various metal cations, including Cr(III), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(I), Cu(II), Zn(II), Cd(II), Gd(III), Na(I), K(I), Ba(II), Mg(II), Al(III), Pb(II), Sn(II), Hg(II), and Ag(I), on the fluorescence of L in an aqueous ethanol environment. During our investigations, a binding constant value of 7.81 × 105 M−1, with a 1:1 stoichiometry for Zn2+–L interactions, was established. Additionally, a low detection limit of 2.51 × 10−8 M and a rapid response time were observed. Furthermore, the chemical inputs of Zn2+ and Cu2+ ions meet the conditions of an INHIBIT molecular logic gate. [ABSTRACT FROM AUTHOR]

Thioureas are preferred structures in the disciplines of chemosensors, organic, and pharmaceutical field. Thioureas, a class of tuneable organosulfur compounds, and their derivatives are widely used in both biological and nonbiological fields. These compounds, which include sulfur (S) and nitrogen (N) atoms, have nucleophilic characteristics that assist in intra‐ or intermolecular H‐bonding among the molecules or analytes. Hence, the incorporation of the thiourea moiety into a wide spectrum of organic molecules has resulted in very versatile compounds with widespread applications in a variety of domains. Thiourea derivatives have been frequently produced and researched due to their chemosensing capability. Finally, in this work, a detailed comparison and analysis of the detecting capabilities of thiourea‐based cation sensor is performed. The knowledge gained in this work will be extremely useful in future endeavours to create organic sensors based on Fluorescence (Fl) and colorimetry, for the recognition of physiologically relevant metal ions. [ABSTRACT FROM AUTHOR]

Fe3+ ion plays a very active role in life, agriculture, and industry. Human health and the environment are seriously affected by the abnormal presence or excess of this cation. Therefore, the development of a fast, reliable, sensitive, and simple fluorescent probe to detect this cation is crucial. In the present paper, polycaprolactone-capped zinc oxide quantum dots were prepared for the determination of Fe3+ ions. The proposed fluorescent chemosensor exhibited a fluorometric and strong quenching effect toward Fe3+ ions at two wavelengths (303 and 602 nm). The limit of detection (LOD) was calculated as 0.410, and 0.333µM at the mentioned wavelengths. Also, the binding stoichiometric ratio was calculated as 1:1 by Job's plot. The findings indicated that the PCL@ZnO colorimetric chemosensor could be successfully applied with reliable, and good accuracy for the detection of Fe3+ ions in real seawater samples. [ABSTRACT FROM AUTHOR]

In this paper, a novel azo Schiff base chemosensor was synthesized via condensation reaction of 4-Aminoantipyrine with 1-(3-Formyl-4-hydroxyphenylazo)-3-nitrobenzene. The imine sensor was studied via spectroscopic methods IR, 1HNMR and UV-Vis. The chromogenic behavior of colorimetric chemosensor toward various anions was investigated by UV–Vis spectroscopic. The chemosensor show abrupt changes towards CN− and OAC−anions in DMF/H2O solution in comparison with other anions. Upon the addition of CN− and OAC− ions to the receptor, the color of the L solution was changed from yellow to purple that was detectable with naked-eye and without any optical instrument. No color changes towards other anions were observed. The detection limits of the azo-azomethin sensor for OAC− and CN− anions were 2.6 ×10-5 and 1.4 ×10-6 mol L-1, respectively. Using the association constant value for sensor towards OAC− and CN− anions was calculated to be 4.2 ×103 and 3.07 ×104 M-1.

Cancer stem cells are pivotal players in tumors initiation, growth, and metastasis. While several markers have been identified, there remain challenges particularly in heterogeneous malignancies like adult soft tissue sarcomas, where conventional markers are inherently overexpressed. Here, we designed BODIPY scaffold fluorescence probes (BD‐IMC‐1, BD‐IMC‐2) that activate via disaggregation targeting for cyclooxygenase (COX), a potential marker for CSCs in sarcoma in clinical pathology. Based on their structures, BD‐IMC‐1 showcased higher susceptibility to disaggregation compared to BD‐IMC‐2, consistent with their selective interaction with COX. Notably, the BD‐IMC‐1 revealed positive cooperativity binding to COX‐2 at sub‐micromolar ranges. Both probes showed significant fluorescence turn‐on upon LPS or PMA triggered COX‐2 upregulation in live RAW264.7, HeLa, and human sarcoma cell line (Saos‐LM2) up to 2‐fold increase with negligible toxicity. More importantly, the BD‐IMC‐1 demonstrated their practical imaging for COX‐2 positive cells in paraffin‐fixed human sarcoma tissue. Considering the fixed tissues are most practiced pathological sample, our finding suggests a potential of disaggregation activated chemosensor for clinical applications. [ABSTRACT FROM AUTHOR]

An effective, GFP‐inspired fluorescent Zn2+ sensor is developed for two–photon microscopy and related biological application that features an 8‐methoxyquinoline moiety. Excellent photophysical characteristics including a 37‐fold fluorescence enhancement with excitation and emission maxima at 440 nm and 505 nm, respectively, as well as a high two–photon cross–section of 73 GM at 880 nm are reported. Based on the experimental data, the relationship between the structure and properties was elucidated and explained backed up by DFT calculations, particularly the observed PeT phenomenon for the turn–on process. Biological validation and detailed experimental and theoretical characterization of the free and the zinc–bound compounds are presented. [ABSTRACT FROM AUTHOR]

Chemosensor A, (E)-(4-(2-((2-hydroxynaphthalene-1-yl)methylene)hydrazinyl)benzonitrile has been synthesized by condensation of 4-cyanophenylhydrazine hydrochloride with 2-hydroxy-1-naphthaldehyde in ethanol solvent at ∼80°C. The chemosensor A, has been characterized by FT-IR, ESI-MS and 1H-NMR spectroscopic techniques. The chemosensor A has been investigated for selective cyanide ion sensing ability through UV–visible and fluorescence spectra. Further the chemosensor A was also employed as live cell imaging reagent for intra-cellular detection of cyanide ion in SW480 cells. [ABSTRACT FROM AUTHOR]

Water pollution has become a serious issue, and mercury(II) ion (Hg(II)) is highly toxic even at low concentrations. Therefore, Hg(II) concentration should be strictly monitored. This study evaluated pyrazoline compounds as fluorescence chemosensor agents for Hg(II) detection. These compounds were prepared from vanillin via etherification, Claisen–Schmidt, and cyclocondensation reactions, to yield benzothiazole–pyrazoline–styrene hybrid compounds. The hybrid compound without styrene was successfully synthesized in 97.70% yield with limit of detection (LoD) and limit of quantification (LoQ) values of 323.5 and 1078 μM, respectively. Conversely, the hybrid compound was produced in 97.29% yield with the LoD and LoQ values of 8.94 and 29.79 nM, respectively. Further spectroscopic investigations revealed that Hg(II) ions can either chelate with three nitrogen of pyridine, pyrazoline, and benzothiazole structures or two oxygen of vanillin and styrene. Furthermore, the hybrid compound was successfully applied in the direct quantification of Hg(II) ions in tap and underground water samples with a validity of 91.63% and 86.08%, respectively, compared with mercury analyzer measurement. The regeneration of pyrazoline was also easily achieved via the addition of an ethylenediaminetetraacetic acid solution. These findings show the promising application of the benzothiazole–pyrazoline–styrene hybrid compound for Hg(II) monitoring in real environmental samples. [ABSTRACT FROM AUTHOR]

A comprehensive review presents an illuminating exploration of the vast potential of isatin, an easily accessible organic compound. This review is a valuable resource, offering a concise yet comprehensive account of the recent breakthroughs in isatin applications in medicinal chemistry, fluorescence sensing, and organic synthesis. Moreover, it dives into the exciting advancements in isatin‐based chemosensors, demonstrating their remarkable ability to detect and recognize diverse cations and anions with exceptional precision. Researchers and scientists in the fields of sensing and organic chemistry will find this review indispensable for sparking innovation and developing cutting‐edge technologies with significant real‐world impact. [ABSTRACT FROM AUTHOR]

In this investigation, a novel and promising chemosensor incorporating a dihydropyrimidinone moiety, namely; (E)‐4‐(4‐(dimethylamino)phenyl)‐5‐(3‐(4‐(dimethylamino)phenyl)acryloyl)‐6‐methyl‐3,4 dihydropyrimidin‐2(1H)‐one (DPDAD), has been successfully synthesized and characterized. The DPDAD chemosensor's response was evaluated in diverse solvents with varying polarities, shedding light on its solvatochromic behavior. The assessment of colorimetric and optical sensing attributes toward a range of metal ions such as Al(III), Cr(III), Mn II), Fe(III), Co(II), Ni(II), and Cu(II) was undertaken. Notably, DPDAD displayed discernible color alterations upon interaction with all the examined metal ions, with a significant bathochromic shift observed in the absorption spectra in the presence of Al(III), distinguishing it from the other metal ions. Furthermore, through detailed absorption and emission spectral analyses, DPDAD exhibited remarkable selectivity, sensitivity, and an on‐off‐on switchable behavior specifically with Al(III) ions, over the other metal ions. The binding constant was determined as 0.39×105 M−1, accompanied by a limit of detection (LOD) of 1.03×10−5 M. Notably, the DPDAD′s potential extends beyond metal ion sensing; it was computationally assessed for its capability to inhibit the γ‐secretase enzyme. Moreover, DPDAD′s antioxidant attributes were probed, and its inhibitory effect against a range of cancer cell lines was verified in‐vitro. [ABSTRACT FROM AUTHOR]

The rapid advancement of biotechnology over the recent decades has amplified the importance of DNA detection and quantification assays. Many of these assays, such as gel electrophoresis, microscopy, flow cytometry, and the detection of amplification in quantitative polymerase chain reaction (qPCR), rely on the use of DNA‐binding fluorescent dyes. This article presents a comprehensive study of six Thiazole‐Orange‐based fluorescent DNA‐binding dyes: SYBR Safe, SYBR Green, Pico Green, SYTO‐16, SYTO‐9, and the benzothiazole‐based analogue (TOPhBu) of the latter. The selected DNA markers were synthesized at a 10‐milligram scale and characterised spectroscopically to quantify their fluorescence enhancement upon binding to double‐stranded DNA. The ability of the dyes to detect DNA at low concentrations was evaluated using two new metrics, absolute fluorescence enhancement (AFE) and relative fluorescence enhancement (RFE). Quantum chemical calculations shed new light on the mechanism of their fluorogenicity through modelling the excited state behaviour and DNA binding of the dyes. Their analytical performance was further tested in qPCR experiments. The experimental results of this work highlight some important differences in the sensitivity and qPCR efficiency of the studied DNA‐binding dyes which will facilitate the DNA marker selection for analytical purposes and the future development of novel DNA sensors. [ABSTRACT FROM AUTHOR]

A novel chemosensor has been developed for the precise detection of Zn2+ in cosmetics creams and water samples, exhibiting remarkable accuracy. This new chemosensor is composed of NH2–UiO–MOF serving as the base MOF, with 2‐acetyl‐6‐bromopyridine acting as the ligand, referred to as the 2A6BrP=N–UiO–MOF chemosensor. Extensive studies have been conducted to optimize the spectrophotometric and fluorometric detection of Zn2+ ions using this new chemosensor. Achieving a consistent and stable spectroscopic signal with the 2A6BrP=N–UiO–MOF chemosensor necessitated a response time of less than 30 s. Validation of the proposed methods followed ICH (International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use) guidelines, ensuring precision in determining limits of detection (LODs), limits of quantification (LOQs), linearity, and precision. The spectrophotometric and fluorometric techniques yielded highly sensitive LOD values of 15.50 (ppb) and 8.70 ppb, respectively, for Zn2+ ions. Furthermore, research indicated that the 2A6BrP=N–UiO–MOF chemosensor can be efficiently recycled up to eight times by treating it with 0.1 M HCl, showcasing its potential for sustainability. Subsequently, the application of the 2A6BrP=N–UiO–MOF chemosensor demonstrated its remarkable efficacy in detecting Zn2+ in various real water samples. Its exceptional sensitivity and selectivity make it a valuable tool for accurate Zn2+ detection in practical environmental settings. [ABSTRACT FROM AUTHOR]

The concept of a lab-on-a-molecule, which was proposed just short of two decades ago, has captured the imagination of scientists. From originally being proposed as an AND logic gate driven by three chemical inputs as a direct way of detecting congregations of chemical species, the definition of what constitutes a lab-on-a-molecule has broadened over the years. In this review, molecules that can detect multiple analytes by fluorescence, among other techniques, are reviewed and discussed, in the context of molecular logic and multi-analyte sensing. The review highlights challenges and suggestions for moving the frontiers of research in this field to the next dimension. [ABSTRACT FROM AUTHOR]

The current report provides an overview of the rapidly developing class of pyrazolines having a benzothiazole moiety at N1. The synthetic approaches (mainly through the [3 + 2] cyclo-condensation of chalcone analogs with 2-hydrazinobenzothiazole) toward these particular pyrazolines, along with their chemical transformation to pyrazoles through oxidation are outlined. The photophysical properties (absorption and emission spectra) along with their applications as fluorescent chemosensors have been summarized. 1-(2-Benzothiazolyl)pyrazolines exhibit significant fluorescence quenching mostly in the presence of transition metal ions, such as Fe3+, Cu2+, Hg2+, Zn2+, or Ni2+, but also toward Al3+, thus enabling the selective detection of these analytes. In addition, examples of 1-(2-benzothiazolyl)pyrazolines acting as chemosensors for anions such as S2− or F− are also available. Comprehensive examination of the biological properties of 1-(2-benzothiazolyl)pyrazolines shows that members of this class possess either broad or selective significant antimicrobial activity, along with tuberculostatic activity and cytotoxicity that is sometimes better than that of positive controls. The antidiabetic, anti-inflammatory, anthelmintic, and antimalarial activity of these compounds, along with their potential for inhibition of enzymes such as carbonic anhydrase or acetylcholinesterase have been briefly explored. [ABSTRACT FROM AUTHOR]

Two new Schiff bases were synthesized from 1‐(2,4‐dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV–Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6‐31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation‐recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4‐(1‐(pyridin‐4‐ylimino)ethyl)benzene‐1,3‐diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4′‐((pyridine‐2,3‐diylbis(azanylylidene))bis(ethan‐1‐yl‐1‐ylidene))bis(benzene‐1,3‐diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)–chelation‐enhanced fluorescence (CHEF) effect and chelation‐enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 × 10−6 and 2.16 × 10−7 M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 × 10−4 M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells. [ABSTRACT FROM AUTHOR]

A mesogenic glycine based Schiff base compound of the type, (E)‐methyl 2‐((2‐hydroxy‐4‐(tetradecyloxy)benzylidene)amino)acetate (HL) has been successfully synthesized and characterized using analytical and spectroscopic techniques. The Schiff base compound was evaluated for chemosensor activity towards different metal ions using fluorescence spectroscopy. The experiment reveals highly efficient and selective "turn‐on" and "turn‐off" responses of the fluorescence intensity towards zinc(II) and copper(II), respectively, in presence of other metal ions. The binding constant and the stoichiometry ratio were determined using Benesi‐Hildebrand equation giving 1 : 1 stoichiometry. The limits of detection for both the metal ions were estimated from the fluorescence titration experiments. The reversibility nature of the Schiff base probe was also studied using EDTA as chelating ligand. The compound, HL exhibits two INHIBIT logic gates with chemical inputs (i) Zn2+ (IN1) and Cu2+ (IN2) and (ii) Zn2+ (IN1) and EDTA (IN2). An IMPLICATION logic gate was also obtained when Cu2+ (IN1) and EDTA (IN2) serve as chemical inputs. The compound was found to exhibit potent antibacterial activity and efficient binding interaction with BSA. Molecular docking studies were carried out in order to ascertain the degree of interaction and the nature of binding of the compound with the proteins. [ABSTRACT FROM AUTHOR]

The N1,N2‐diphenyloxalohydrazide OX(HA)2 chemosensor was synthesized and used as a colorimetric and fluorescent receptor to detect Cu2+ and Fe3+ ions in the presence of other metal ions. A range of physicochemical approaches were utilized to characterize the symmetrical oxalohydrazide‐based receptor, including FT‐IR, 1H and 13C NMR, TGA, and mass spectrometry. According to single crystal X‐ray diffraction investigation, OX(HA)2 crystallizes in monoclinic with space group C2/c. UV‐Vis and fluorescence spectroscopy were used to thoroughly explore OX(HA)2's sensing capabilities towards diverse cations. Using measurements of fluorescence intensity, the binding constant for OX(HA)2 with Cu2+/Fe3+ ions was calculated to be 2.78×103 M−1 and 1.12×103 M−1 with the lower detection limit of 0.43 μM and 0.2 μM respectively. With a 1 : 1 binding mechanism validated by Job's plot, mass spectral analysis, FT‐IR spectra, and density functional theory, the dual‐sensing receptor exhibits remarkable selectivity and sensitivity towards Cu2+ and Fe3+ ions. The average fluorescence lifetimes of OX(HA)2, OX(HA)2+Cu2+, and OX(HA)2+Fe3+ were calculated to be 2.19 ns, 1.73 ns, and 1.26 ns, respectively. This fluorescence lifetime measurement results strongly support the complexation of Cu2+ and Fe3+. When Cu2+ and Fe3+ ions bind with OX(HA)2, they induce the 'Turn‐Off' signal. Then, fluorescence imaging of the OX(HA)2 receptor in MDA‐MB‐231 demonstrated that the receptor holds a lot of promise for usage in bioimaging and their IC50 value for cytotoxicity is 96.96 μg. Furthermore, fluorescence microscopy experiments demonstrate that OX(HA)2 can be utilized as a fluorescent probe for detecting Cu2+ and Fe3+ ions in living cells, making it potentially helpful as an anticancer medication. [ABSTRACT FROM AUTHOR]

Pyridine derivatives are the most common and significant heterocyclic compounds, which play an important role in various fields ranging from medicinal to chemosensing applications. Pyridine derivatives possess different biological activities such as antifungal, antibacterial, antioxidant, antiglycation, analgesic, antiparkinsonian, anticonvulsant, anti-inflammatory, ulcerogenic, antiviral, and anticancer activity. Furthermore, these derivatives have a high affinity for various ions and neutral species and can be used as a highly effective chemosensor for the determination of different species. In this review article, generally used synthetic routes of pyridine, structural characterization, medicinal applications, and potential of pyridine derivatives in analytical chemistry as chemosensors have been discussed. We hope this study will support the new thoughts to design biological active compounds and highly selective and effective chemosensors for the detection of various species (anions, cations, and neutral species) in various samples (environmental, agricultural, and biological). [ABSTRACT FROM AUTHOR]

Chromium occurs in the environment primarily in two valence states, trivalent Cr3+ and hexavalent Cr6+, which have different physicochemical and biochemical properties. However, the higher concentration of Cr3+/6+ can cause various adverse effects on human health. Therefore, detecting Cr3+/6+ ions is important in various samples. Colorimetric and fluorescent chemosensors are the most powerful tools for the detection of Cr3+/6+ ions. These chemosensors have excellent bioimaging capability and significant sensitivity and selectivity. In this article, different colorimetric and fluorescent chemosensors based on organic compounds, including Schiff base, antipyrine, diarylethene, pyrene, crown ether, dansyl, pyridine, thiazole, coumarin, boradiazaindacene, rhodamine, imidazole, hydrazone, and other functional groups for detection of Cr3+/6+ ions have been reviewed, classified them according to different fluorophore and recognition mode. I hope this article will help the readers for the future design of highly effective, sensitive, and selective chemosensors for the detection and determination of Cr3+/6+ ions. [ABSTRACT FROM AUTHOR]

In this paper, a novel azo Schiff base chemosensor was synthesized via condensation reaction of 4-Aminoantipyrine with 1-(3-Formyl-4-hydroxyphenylazo)-3-nitrobenzene. The imine sensor was studied via spectroscopic methods IR, 1HNMR and UV-Vis. The chromogenic behavior of colorimetric chemosensor toward various anions was investigated by UV--Vis spectroscopic. The chemosensor show abrupt changes towards CN- and OAC--anions in DMF/H2O solution in comparison with other anions. Upon the addition of CN- and OAC- ions to the receptor, the color of the L solution was changed from yellow to purple that was detectable with naked-eye and without any optical instrument. No color changes towards other anions were observed. The detection limits of the azo-azomethin sensor for OAC- and CN- anions were 2.6 ×10-5 and 1.4 ×10-6 mol L-1, respectively. Using the association constant value for sensor towards OAC- and CN- anions was calculated to be 4.2 ×10³ and 3.07 ×104 M-1. [ABSTRACT FROM AUTHOR]

Resorcinol based carbonyl precursors such as 4, 6-Diacetylresorcinol, 2, 4-dihydroxy- acetophenone and 2, 4-dihydroxybenzaldehyde were used for the synthesis of different Schiff bases mainly through conventional method of synthesis. The reviewed Schiff bases were synthesized by condensation reactions between either of these resorcinol based carbonyls and primary amines such as o-aminophenol, o-phenylenediamine, oxalyldihydrazine,1,8-naphthalenediamine,4-methyl-2-amino phenol, hydrazine monohydrate and isatin, 2-amino-4-methylthiazole,4-halo aniline, aminated silica gel, amine derived from hydrazine hydrate, carbon disulfide and benzyl chloride, ethanolamine, 3-hydrazino-5,6-diphenyl-1,2,4-triazine, p-phenylene diamine, semicarbazide hydrochloride, chitosan,α-naphthylamine, paraaminophenol, 4-aminoantipyrine 3,3-Dimethoxybenzidine and benzoylhydrazide. These Schiff bases were formed from different complexes by reacting with different first row transition metal ions. The structures of the Schiff bases and their complexes were elucidated mainly by infrared, UV–visible, nuclear magnetic resonance, mass spectroscopies and elemental analysis. The complexes were also characterized by ESR spectroscopy, conductance & magnetic susceptibility measurement and thermogravimetric analysis. The Schiff base ligands and their first row transition metal complexes were screened for activities including biological, catalytic and chemosensor activities. This review incorporates the progresses that have been observed from 2007 through 2021 on synthesis, characterization and application studies of resorcinol based Schiff bases and their first row transition metal complexes.

ABSTRACTMulberry silkworms have provided many valuable byproducts to humans for 5,000 years. However, numerous possibilities for their utilization still exist owing to the countless varieties of silkworms. Here, we report the application of Yeonnokjam silk (pistachio silk, PS), one of the characteristic silk varieties in Korea, as a smart fabric environmental sensor. Unlike the previously reported extrinsically modified silk varieties, this new silk textile emits fluorescence under external stimuli. PS cocoons were exposed to different concentrations of HCl vapors. Due to the large surface-to-volume ratio of the cocoon textile, a very low concentration (5 ppm) of HCl vapor can be detected by reading the decrease in the fluorescence intensity. At a lethal concentration (3000 ppm), an instantaneous fluorescence response is obtained. Additionally, the fluorescent pigment in PS can respond to temperature and can be extracted using ethanol, indicating that PS exhibits temperature and ethanol-sensing capabilities. The findings of this study prove that natural PS can be used in bio-optical applications.

In this work, we designed and synthesized a novel, simple, low-cost, and effective chromone–based Schiff base ligand (HL) and its application as a chemosensor for Fe3+ detection. The structure of the synthesized sensor bears carboxylic, azomethine, and carbonyl groups which act as chelating sites for the detection of Fe3+ ions. The chemosensor HL exhibited highly selective detection of Fe3+via a significant colour change from yellow to brown. The colour change is due to the ligand-to-metal charge-transfer (LMCT) mechanism. The sensor (HL) was characterized using UV-Vis, FTIR, NMR (1H- and 13C), and mass spectroscopy. The ligand solubility, detection condition, and sensitivity assessment suggested optimal use of DMF-water (9:1 v/v) as a working solvent at pH 7.0. Among a list of 15 metal ions screened, HL was highly selective, with instant response, towards Fe3+ ions without significant interferences with the other metal ions. The complexation ratio and association constants of HL to Fe3+ was determined by Job's plot and Benesi–Hildebrand methods, and were 2:1 and 2.24 × 103 M−1, respectively, with a detection limit of 2.86 μM. The HL probe was also applied to detect Fe3+ in real samples with acceptable performance. The simple test strips have been successfully developed and applied to the visual monitoring of Fe3+ ions with a detection limit of 68 µM. The DFT was used to examine the best interaction mode of HL with Fe metal to be Fe(III)–L or Fe(III)–2L. The chemical-reactivity and molecular electrostatic optional were figured to predict the interaction behaviour of the tested compounds. [ABSTRACT FROM AUTHOR]

The few commercially available chemosensors and published probes for in vitro Zn2+ detection in two-photon microscopy are compromised by their flawed spectroscopic properties, causing issues in selectivity or challenging multistep syntheses. Herein, we present the development of an effective small molecular GFP chromophore-based fluorescent chemosensor with a 2,2′-bipyridine chelator moiety (GFZnP BIPY) for Zn2+ detection that has straightforward synthesis and uncompromised properties. Detailed experimental characterizations of the free and the zinc-bound compounds within the physiologically relevant pH range are presented. Excellent photophysical characteristics are reported, including a 53-fold fluorescence enhancement with excitation and emission maxima at 422 nm and 492 nm, respectively. A high two-photon cross section of 3.0 GM at 840 nm as well as excellent metal ion selectivity are reported. In vitro experiments on HEK 293 cell culture were carried out using two-photon microscopy to demonstrate the applicability of the novel sensor for zinc bioimaging. [ABSTRACT FROM AUTHOR]

A novel platform of a polydiacetylene combined with rhodamine B (PDA-Rho) colorimetric chemosensor array was prepared from a diacetylene monomer and rhodamine B derivative. Rhodamine B derivative as the ion-recognition element was embedded in the polydiacetylene matrix. To fabricate chemosensor, diacetylene monomer connected rhodamine B derivatives (DA-Rho) was coated onto a filter paper surface via drop-casting technique and transformed to polydiacetylene by polymerisation through ultraviolet (UV) irradiation. From the result, PDA-Rhoen exhibited high sensitivity and selectivity for Au3+ and could be monitored directly by naked eyes providing a fast, portable and easy-to-use as a molecular device in the real system. The DFT calculation results showed a stable complex between PDA-Rho and Au3+. We believe that, this method offers a sensitive and accurate process for Au3+ ion detection in real environmental and biological applications. [ABSTRACT FROM AUTHOR]

A colorimetric turn-on chemosensor based on gold nanorods, Au NRs, has been developed to enable rapid, facile, and simultaneous detection of hazardous metal ions. This study involved the functionalization of gold nanorods with (9,10-dioxo-9,10-dihydro-anthracen-1-yl)-dithiocarbamic acid (DTAD) through the utilization of synthetic photo-irradiation and ultrasound techniques. Various spectroscopic methods were employed to characterize both the synthesized gold nanorods and the chemosensor. The optical response of this sensor was investigated with respect to a range of metal ions, including Mg2+, K+, Ca2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+. The results reveal that the DTAD-functionalized gold nanorods chemosensor effectively discriminates all the investigated metal ions, with Cd2+ ions exhibiting higher sensitivity and selectivity compared to the other metal ions. Moreover, the anticancer impact of both gold nanorods and DTAD-functionalized gold nanorods was investigated on a panel of cell lines as breast cancer (MCF-7), liver cancer (HepG-2), and colon cancer (Caco-2) using MTT assay. Further, the morphological features and Annexin V using flow cytometry were carried. Comparative analysis with a free chemosensor showed that fluorescence images of living cells were notably brighter in the presence of Cd2+, highlighting the efficacy of DTAD-functionalized gold nanorods as a fluorescent biosensor for Cd2+ ions. Additionally, the in vitro anticancer study showed that gold nanorods significantly inhibited the growth of all cancer cells than DTAD-functionalized gold nanorods with best antiproliferative effect on HepG-2 hepatocellular carcinoma with IC50 values equal to 1.971 ± 1.28, 40.95 ± 2.56 µg/mL, respectively, compared to DOX. Also, the alteration in the HepG-2 morphological shape and Annexin V results confirmed the great antineoplastic effect of Au NRs than DTAD-Au NRs. [ABSTRACT FROM AUTHOR]

In this study, we report a new syringe aldehyde-derived hydrazinyl-imidazole based fluorescent sensor (L) for sensitive detection of different inorganic quenchers (halide ions, bicarbonate ion, sulphide ion and transition metal ions). The chromophore (L) was obtained in good yield by the 1:1 condensation reaction of 2-hydrazino-4,5-dihydroimidazole hydrobromide and 4-hydroxy-3,5-dimethoxy benzaldehyde. L exhibited strong fluorescence in the visible region (around 380 nm) and its interaction with different quenchers was studied in details via fluorescence technique. For the halide ions series, its sensitivity is higher for NaF (Climit = 4 × 10− 4 M) than for NaCl while the fluorescence quenching occurred mainly through a dynamic process. Similar considerations were observed for HCO3− and S2− quencher too, when static and dynamic quenching take place simultaneously. Regarding transition metal ions, at a fixed ion concentration (4 × 10− 6 M), best performance was achieved for Cu2+ and Fe2+ (fluorescence intensity was reduced by 79% and 84.9% respectively), while for other metal ions, the sensor performance was evaluated and found to be very less (< 40%). Thus, minimum detection limits (10− 6 – 10− 5 M range) recommended the use of such derivatives as highly sensitive sensors capable to monitor delicate changes in varied environments. [ABSTRACT FROM AUTHOR]

The chalcone compound DHPO was synthesized through a chemical reaction between 1-(2-hydroxyphenyl)-ethanone and 3,4-dimethoxy benzaldehyde under ultrasound irradiation. The interaction between the DHPO compound and several metal ions was studied using fluorescence behavior, revealing that the chalcone function as a "turn on and turn off" switch fluorescent sensor, for selectively and sensitively detecting Fe3+ ions. The process of fluorescence quenching and complexation of DHPO with Fe3+ ion was further studied using methods such as Benesi-Hildebrand, Stern-Volmer plot, and job plot. [ABSTRACT FROM AUTHOR]

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier‐transform infrared (FTIR), proton (1H)‐ and carbon‐13 (13C)‐nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X‐ray diffraction analysis. Chemosensor 1 is composed of a 1H‐imidazole core with specific substituents, including a 4‐(2‐(4,5‐c‐2‐yl)naphthalene‐3‐yloxy)butoxy)naphthalene‐1‐yl moiety. However, chemosensor 2 features a 1H‐imidazole core with distinct substituents, such as 4‐methyl‐2‐(4,5‐diphenyl‐1H‐imidazole‐2‐yl)phenoxy)butoxy)‐5‐methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi–Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104 M−1, respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+, the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity. [ABSTRACT FROM AUTHOR]

Oxadiazoles, especially 1,3,4-oxadiazole scaffolds, stand among the foremost heterocyclic fragments with a broad spectrum of applications in diverse fields, including pharmacology, polymers, material science, and organic electronics, among others. In this comprehensive review, we summarize the pivotal synthetic strategies for 1,3,4-oxadiazole derivatives including dehydrogenative cyclization of 1,2-diacylhydrazines, oxidative cyclization of acylhydrazones, condensation cyclization, C-H activation of oxadiazole ring, decarboxylative cyclization and oxidative annulation along with plausible mechanisms. The set of 1,3,4-oxadiazoles selected from the literature and discussed herein epitomize the ease of synthesis as well as the possibility of linking π-conjugated groups; thereby encouraging the use of these molecules as important starting building blocks for a wide variety of fluorescent frameworks, particularly in the development of potential chemosensors. High photoluminescent quantum yield, excellent thermal and chemical stability, and the presence of potential coordination (N and O donor atoms) sites make these molecules a prominent choice for metal-ions sensors. An overview of selective metal-ion sensing, the detection limit along with the sensing mechanisms (photo-induced electron transfer, excited-state intramolecular proton transfer, and complex formation) is also included. [ABSTRACT FROM AUTHOR]

Early-stage detection and diagnosis of diseases is essential to the prompt commencement of treatment regimens, curbing the spread of the disease, and improving human health. Thus, the accurate detection of disease biomarkers through the development of robust, sensitive, and selective diagnostic tools has remained cutting-edge scientific research for decades. Due to their merits of being selective, stable, simple, and having a low preparation cost, molecularly imprinted polymers (MIPs) are increasingly becoming artificial substitutes for natural receptors in the design of state-of-the-art sensing devices. While there are different MIP preparation approaches, electrochemical synthesis presents a unique and outstanding method for chemical sensing applications, allowing the direct formation of the polymer on the transducer as well as simplicity in tuning the film properties, thus accelerating the trend in the design of commercial MIP-based sensors. This review evaluates recent achievements in the applications of electrosynthesized MIP sensors for clinical analysis of disease biomarkers, identifying major trends and highlighting interesting perspectives on the realization of commercial MIP-endowed testing devices for rapid determination of prevailing diseases. [ABSTRACT FROM AUTHOR]

A new adeninecarboxamide ligand, N-(9 H-purin-6-yl) pyridine-2-carboxamide (H2pzac) has been synthesized by a green chemistry method using tetrabutylammunium bromide (TBAB) ionic liquid as an environmentally friendly reaction medium. The H2pzac ligand was anchored on modified SBA-15-Cl and utilized for detection of Hg2+ in aqueous solution. The as-constructed SBA-15@Hpzac sensor shows a high specific surface area as well as pore volume of 250 m2/g and 0.54 cm3/g, respectively. The fluorescence assessment indicated that the designed SBA-15@Hpzac sensor presented highly sensitive and selective behavior to Hg2+ ion over different cations including Zn2+, Ni2+, Co2+, Cu2+, Mn2+, Pb2+, Ba2+, Mg2+, Ca2+, Na+, Fe3+, Fe2+, Al3+, Cd2+ and K+. The fluorescence response of the SBA-15@Hpzac sensor for selective detection of Hg2+ ion is excellent with detection limit (LOD) of 1.07 × 10− 6 M. The application of the SBA-15@Hpzac sensor in determination of Hg2+ ions in two real water samples was also investigated. [ABSTRACT FROM AUTHOR]

Detection of correct oxidation state of a metal ion is important to understand its speciation and redox properties. Some of rhodamine derivatives can identify Al3+, Cr3+ and Fe3+ as the trivalent cations. We have synthesized a rhodamine derivative, HL‐qui, from the reaction of N‐(rhodamine‐6G)lactam‐ethylenediamine with quinoline‐2‐carboxaldehyde for the colorimetric as well as fluorogenic detection of all of metal ions with +3 oxidation state such as Al3+, Cr3+, Fe3+, Ga3+, In3+, Tl3+ and Gd3+. In the presence of these trivalent cations, colorless and nonfluorescent HL‐qui turns pink and strongly fluorescent in HEPES buffer (10 mM) in H2O/ethanol=1/9 (v/v) (pH 7.4) as its spirolactam ring gets open to show the changes in color and fluorescence properties. High sensitivity of the probe towards the cations is reflected from the limit of detection values that are in nM range. To the best of our knowledge, there is no such report where fluorescence sensing has been utilized to determine oxidation state. This multi‐ion sensing feature has been used for fabrication of multi input‐output based logic circuit using Boolean algebraic method. It has been used in imaging of metal ions in living cell (L6 cells). [ABSTRACT FROM AUTHOR]

In this study, we present an unprecedented reaction of BOPHY. Although tetrabrominated BOPHY (BrBPH) is known to give a substitution reaction with amines, we found that this reaction proceeds through an addition mechanism in the dilute medium. Upon this reaction, the absorption and fluorescence bands of BrBPH decrease dramatically. We used this newly presented reaction for the fluorimetric detection and quantification of amines. BrBPH‐adsorbed TLC plates were also utilized for the determination of food spoilage. [ABSTRACT FROM AUTHOR]

Croconaine dyes have been repeatedly mentioned in scientific literature for their applications in imaging and photothermal therapy. However, they have not been adequately researched and represented compared to their more well-known analog, squaraine dyes. Although croconaine dyes exhibit favorable properties such as absorption in the near infra-red region and thermal stability upon laser light irradiation, the full realization of these properties for potential applications has not gained considerable attention. While numerous reviews on squaraine dyes are available, the corresponding number for croconaine dyes remains relatively insignificant. The current study aims to revisit the long-known oxocarbon analog, citing literature concerning its applications in various fields, especially analyte detection, photothermal therapy, and biological theranostics, thereby re-establishing its significance. [ABSTRACT FROM AUTHOR]

• A chromone-based ratiometric fluorescent probe L2 was developed for the selective detection of Hg(II) in a semi-aqueous medium. • Job's plot reveals that the probe forms a 1:1 stoichiometry complex with L2 with a K a = 9.1 × 103 M−1 estimated by the BH plot method. • Probe L2 detects Hg(II) with an LOD of 22.5 nM without interference with other ions. • Probe L2 was applied for Caenorhabditis elegans (Nematode worm) bioimaging of Hg(II) ions. A chromone-based ratiometric fluorescent probe L2 was developed for the selective detection of Hg(II) in a semi-aqueous solution based on aggregation-induced emission (AIE) and chelation-enhanced fluorescence (CHEF) effect. The probe L2 fluoresced significantly at 498 nm in its aggregated state, and when chelated with Hg(II), the soluble state fluoresced 1-fold higher. In addition, Job's plot reveals that the probe forms a 1:1 stoichiometry complex with Hg(II) with an association constant of 9.10 × 103 M−1 estimated by the BH plot. The probe L2 detects Hg(II) down to 22.47 nM without interference from other interfering ions. The FTIR, ESI mass, and DFT-based computational studies investigated the binding mechanism of probe L2 with Hg(II). Taking advantage of its AIE characteristics, the probe L2 was successfully applied for bio-capability analysis in Caenorhabditis elegans (a nematode worm) imaging of Hg(II) in a living model. [ABSTRACT FROM AUTHOR]

For over five millennia, humans have benefited from the valuable byproducts of Bombyx mori silkworms nourished on mulberry leaves and a multitude of potential applications remains available due to the diverse array of silkworm varieties. In this work, we discuss the utilization of Daehwangjam (DHJ), golden silk (GS), and Juhwangjam (JHJ), distinctive colored silks found in Korea, as chemosensors. These novel silks emit fluorescence under external stimuli and show a diminishing fluorescence intensity when exposed to HCl vapor. The considerable surface-to-volume ratio of these cocoons allows for the identification of 5 ppm, 300 ppm, and 3000 ppm HCl vapors through decreased fluorescence intensity. The results show the suitability of natural DHJ, GS, and JHJ for applications in biosensing applications. [ABSTRACT FROM AUTHOR]

Metals are extensively used for different applications in agriculture and industry. Accumulations of these metals in the environment lead to serious health concerns. Currently, fast and accurate detection of metal ions in the environment or biological system has become a critical issue. Hence, developing an appropriate tool for the detection of metals can help reduce environmental metal pollution and reduce health concerns. In the present study, a hybrid fluorescent probe or chemosensor for parallelly detecting two important metal ions (Mercury and Aluminium) has been designed and tested for its detection efficiency. The newly synthesized chemosensor 3′,6′-bis(ethylamino)-2′,7′-dimethyl-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one (RS) was found to specifically detect Hg2+ and Al3+ ions with high sensitivity and selectivity. The chemical and physical properties of chemosensor RS were tested using single-crystal X-ray diffraction, UV and Fluorescence analysis. The quick response to Hg2+ and Al3+ is attributable to the creation of a coordinate bond present between the chemosensor RS and the metal ion. The selective sensing of chemosensor RS is due to the spirolactam ring opening followed by the development of proper coordinate geometry in the chemosensor. 1H NMR titration experiment and Job’s approach studies suggest a significant binding stoichiometry between the chemosensor RS and the metal ions at a 1:1 ratio. The limit of detection (LOD) of chemosensor RS was determined to be 1.88 µM for Al3+ and 1.75 µM for Hg2+ ions. The in vivo studies using two experimental animal models, Drosophila melanogaster (fruit fly) and Poecilia reticulate (guppy fish), clearly demonstrate its efficiency in detecting endogenously absorbed Hg2+ and Al3+. Thus, chemosensor RS can selectively and simultaneously detect Hg2+ and Al3+ in biological or environmental samples and can help us in monitoring metal leaching into the environment.