Aldoxime-Derived Water-Soluble Polymer for the Multiple Analyte Sensing: Consecutive and Selective Detection of Hg2+, Ag+, ClO–, and Cysteine in Aqueous Media

Thin colorimetric film array for rapid and selective detection of v-type nerve agent mimic in potentially contaminated areas

The expeditious detection and quantification of V-series nerve agents (VX) on potentially contaminated surfaces are crucial for the prevention of regional conflict incidents, acts of terrorism, or illicit activities. However, the low volatility and high toxicity of VX make these tasks challenging. Herein, we designed two novel colorimetric thin polymeric films to rapidly and sensitively detect demeton-S, a VX mimic, in contaminated areas. The polymeric films were specifically engineered to include a coordination site for Au (III) ions. Initially, these films were coordinated with Au (III), causing a discernible alteration in color due to enhancement in intramolecular charge transfer process. In the presence of demeton-S, the Au (III) ligands in the films are displaced with demeton-S, resulting in the restoration of the original color of the film, as the enhanced intramolecular charge transfer process is inhibited and thereby serving as an indicator of the presence of demeton-S. The polymeric films exhibit remarkable selectivity toward demeton-S compared to G-type nerve agents and other interference. The reusability of the polymeric films for demeton-S detection was achieved owing to the reversibility of the films during the alternative exposure of Au (III) and demeton-S. The polymeric films demonstrated their applicability for demeton-S detection and quantification in several contaminated areas, including different water, soil, and skin, rendering them highly suitable for on-site measurements.

Design and Synthesis of Novel Fluorescent Probe Based on Cyanobiphenyl and its Application in Detection of Hypochlorite

Hypochlorite is an important biological reactive oxygen species, which plays a pivotal role in various life activities. Excessive presence in the human body or excessive intake in life causes a series of diseases. To monitor the hypochlorite level in living cells, organisms and environment water samples, we herein designed and synthesized three organic small molecule fluorescent probes with different recognition sites based on nitrile biphenyl. Through performance comparison, it was found that probe A-HM exhibited the best detection performance for hypochlorite with a low detection limit of 2.47 × 10^-6 M. The introduction of hypochlorite will induce probe fluorescence A-HM to turn on, and the fluorescence colour will change from colourless to green. The application of A-HM in biological systems has been demonstrated by the imaging monitoring of hypochlorite in MCF-7, L929 cells and zebrafish. Furthermore, A-HM was also used for the accurate determination of the hypochlorite level in real water samples with high sensitivity and good recoveries.

A dual-mode probe based on AIE and TICT effects for the detection of the hypochlorite anion and its bioimaging in living cells

Based on aggregation-induced emission (AIE) and twisted intramolecular charge transfer (TICT) mechanisms, a fluorescent probe SWJT-12 for the detection of ClO^- was designed by using the CN bond as a reactive group. This synthesized probe can react with ClO^- in a high aqueous phase, and it shows a large Stokes shift (144 nm) and low biological toxicity. Its limit of detection was calculated to be 0.28 μM. Furthermore, SWJT-12 was successfully used for ratiometric imaging of the exogenous hypochlorite anion in living cells.

A Review on Conducting Polymers for Colorimetric and Fluorescent Detection of Noble Metal Ions (Ag+, Pd2+, Pt2+/4+, and Au3+)

Conducting polymers (CPs) are conductive materials composed of organic polymers. CPs have excellent properties such as easy synthesis and effortless fabrication, tunable electrical property, high environmental stability, high mechanical and optical properties. These unique properties have attracted researchers to discover a wide variety of uses, such as batteries, solar cells, sensors, supercapacitors, electrochromic devices, and biochemical applications. Although CPs have many limitations in their pristine form, hybridization with other materials overcomes these limitations. Here in this review article, we discuss different CPs based chemosensors for colorimetric and fluorimetric detection and determination of noble metal ions (Ag+, Pd2+, Pt2+/4+, and Au3+) in different environmental, agricultural, and biological samples. Further, the sensing performances of these chemosensors have been compared and discussed. We hope this article will help the readers with the future design of CPs based optical sensor (colorimetric and fluorescent) for detecting noble metal cations.

Recyclable macromolecular thermogels for Hg(II) detection and separation via sol-gel transition in complex aqueous environments

The sensitive detection and quantitative separation of toxic heavy metal ions in aqueous media are of great importance. In this study, a thermogelling poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) triblock copolymer (P1) was synthesized, and difluoroboron dipyrromethene (BODIPY) fluorophore integrated with thiosemicarbazide units was attached to the chain ends of P1 through consecutive post-polymerization modifications, leading to P4. P4 exhibited rapid and selective detection of Hg(II) in 100% aqueous media via turn-on fluorescence emission with a limit of detection (LOD) of as low as 0.461 μM. This turn-on emission behavior is attributed to the suppression of C˭N isomerization caused by the formation of a coordination complex between P4 and Hg(II) ions. The selective and quantitative removal of Hg(II) among various metal ions was achieved by trapping chelated Hg(II) ions inside the dehydrated P4 gel via thermo-controlled sol-gel-dehydrated gel transitions. Treating the Hg(II) ion-trapped dehydrated gels with sodium sulfide (Na₂S) in acetone/water at room temperature led to HgS precipitates, and P4 in solution was dried and recycled. This recyclable thermoresponsive macromolecular probe is promising for not only Hg(II) detection but also its separation and removal from complex aqueous environments.

A Review on Schiff Base Fluorescent Chemosensors for Cell Imaging Applications

Fluorescent determinations of analytes have proven to be a powerful method due to their simplicity, low cost, detection limit, rapid photoluminescence response, and applicability to bioimaging. Fluorescence imaging as a powerful tool for monitoring biomolecules within the living systems. Schiff base has been extensively used as strongly absorbing and colorful chromophores in the design of chemosensors. In recent years, Schiff base based fluorescent probes have been developed for the detection of various toxic analytes and imaging of various analytes in biological systems. This review gives an overview of the important fluorescent sensors which are based on Schiff base, their approaches for molecular recognition, and their potential application in bioimaging studies.

A Reusable Polymeric Film for the Alternating Colorimetric Detection of a Nerve Agent Mimic and Ammonia Vapor with Sub-Parts-per-Million Sensitivity

Thin polymeric films were developed for the vapor-phase sequential colorimetric detection of a nerve agent mimic and ammonia with high sensitivity. N-(4-Benzoylphenyl)acrylamide (BPAm), N,N-dimethylacrylamide (DMA), and (E)-2-(methyl(4-(pyridine-4yldiazenyl)phenyl)amino)ethyl acrylate (MPDEA, M1) were copolymerized via free radical polymerization (FRP) to yield p(BPAm-co-DMA-co-MPDEA), hereafter referred to as P1. P1 exhibits selective sensing properties toward diethyl chlorophosphate (DCP), a nerve agent mimic, in pure aqueous media. Upon the addition of DCP, the pyridine groups of P1 were quaternized with DCP, accompanied by a color change from yellow to pink due to the enhancement of the intramolecular charge transfer (ICT) effect. In situ generated quaternized P1, hereafter referred to as P2, after DCP sensing was used to selectively detect ammonia via dequaternization in an aqueous medium. Ammonia detection was indicated by a color change in the solution from pink back to yellow. A surface-immobilized P1 film was prepared and employed for the vapor-phase detection of DCP, demonstrating that an amount of as low as 2 ppm was detectable. Ammonia vapor was also successfully detected by the P2 film via the ammonia-triggered removal of the quaternized phosphates. Alternating exposure of the film to DCP and ammonia resulted in the corresponding color changes, thereby demonstrating the reversibility of the system. The reusability of the polymeric film for detecting DCP and ammonia in the vapor phase was confirmed by performing four sequential colorimetric detection cycles.

Naphthalimide based smart sensor for CN−/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging

Probe R designed as tailor-fit triple action smart chemosensor for the sequential detection of CN⁻ and Fe³⁺via colorimetric and fluorometric ‘on–off’ method and H₂S through colorimetric method in semi-aqueous conditions.

Simultaneous recognition of cysteine and cytosine using thiophene-based organic nanoparticles decorated with Au NPs and bio-imaging of cells

Biomolecules like cysteine and cytosine play a significant role in many physiological processes, and their unusual level in biological systems can lead to many diseases including cancer. Indeed, the need for selective detection of these moieties by a fluorescence probe is imperative. Thus, thiophene based Schiff N,N'-bis(thiophene-2-ylmethylene)thiophenemethane (BMTM) was synthesized and then characterized using several analytical techniques before converting it into organic nanoparticles (ONPs). Then, fluorescent organic inorganic nanohybrids (FONs) were obtained after decorating ONPs with AuNPs to yield BMTM-Au-ONPs (FONPs). The morphology of the particles, analyzed using a Transmission Electron Microscope (TEM), shows that AuNPs were embedded with low density organic matter (ONPs). FONPs were employed to recognize cysteine and cytosine simultaneously. No interference was observed from other moieties such as guanine, uracyl, NADH, NAD, ATP, and adenine during the detection. It means that the intensity of the fluorescence signal was significantly changed (enhanced for cytosine and quenched for cysteine). So, FONPs were used to detect cysteine and cytosine in real samples, like Saccharomyces cerevisiae cells. As expected, no considerable fluorescence signal for cysteine was observed, while for cytosine, strong fluorescence signals were detected in the cells. DFT was used to explain the interaction of FONPs with cysteine or cytosine.

BODIPY-Derived Polymeric Chemosensor Appended with Thiosemicarbazone Units for the Simultaneous Detection and Separation of Hg(II) Ions in Pure Aqueous Media

Developing a simple and cheap analytical method for the selective detection and quantitative separation of toxic ions present in aqueous media is the biggest challenge faced by the chemosensing research community. Here, a 5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-derived water-soluble polymer integrated with thiosemicarbazone units was rationally designed and synthesized for the simultaneous detection and separation of Hg(II) ions in pure aqueous solution. The water-soluble polymer scaffold poly( N, N'-dimethyl acrylamide- co-5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-2-carbaldehyde) was synthesized by reversible addition-fragmentation chain transfer polymerization, followed by post-polymerization modification with thiosemicarbazide, leading to the formation of the target probe, P1. The nonemitting P1 exhibited bright yellow emission upon exposure to Hg(II) ions, with a limit of detection as low as 0.37 μM. This turn-on emission behavior triggered by Hg(II) ions might originate from the suppression of isomerization around the C═N bond of the thiosemicarbazone moiety caused by the formation of a coordination complex between P1 and Hg(II) ions. In addition, P1 displayed excellent selectivity toward Hg(II) ions over other metal cations. Finally, the selective removal of Hg(II) ions from an aqueous solution containing various metal ions was achieved by precipitation, which is probably caused by the fact that coordination complexes whereby Hg(II) ions acted as bridgeheads between P1 molecules had formed.

Amino acid-derived alternating polyampholyte luminogens

A unique polyampholyte luminogen comprised of alternatively placed oppositely charged moieties onto the poly(styrene-alt-maleimide) skeleton was synthesized, and used for the specific detection of carbon disulfide (CS₂) in both solution and vapor phases.

Thermo-tunable colorimetric detection of mercury(ii) ions driven by the temperature-dependent assembly and disassembly of a block copolymer

A thermo-responsive double-hydrophilic block copolymer (DHBC) was synthesized for the thermo-tunable detection of mercury(ii) ions modulated by a temperature-dependent morphological transition between unimers and micellar aggregates.

Polymeric Micelles Based on Light-Responsive Block Copolymers for the Phototunable Detection of Mercury(II) Ions Modulated by Morphological Changes

Polymeric micelles based on light-responsive block copolymers were prepared and used for the phototunable detection of mercury(II) ions. 2-Nitrobenzyl acrylate (NBA) and ( E)-2-((4-((4-formylphenyl)diazenyl)phenyl)(methyl)amino) ethyl acrylate (FPDEA) were copolymerized from a poly(ethylene oxide) (PEO) macroinitiator via atom transfer radical polymerization (ATRP), leading to a well-defined block copolymer of PEO₁₁₃- b-[p(NBA₁₀- co-FPDEA₃)] with a low polydispersity index (PDI = 1.16). After polymerization, the aldehyde groups of PEO- b-[p(NBA- co-FPDEA)] were converted to aldoxime groups by reacting with hydroxylamine, leading to the formation of a final oxime-containing polymeric probe, PEO- b-[p(NBA- co-HPDEA)], P1. The resulting block copolymer, P1, was self-assembled in water to yield spherical micelles that consist of a PEO block forming a hydrophilic shell and a copolymer of light-responsive NBA and a mercury(II) ion-detecting HPDEA block forming a hydrophobic core. Upon the addition of mercury(II) ions to this micellar solution, no detection was observed since water-soluble mercury(II) ions have limited accessability to the oxime units of P1, which are located in the hydrophobic core. After UV light irradiation, however, the photolabile 2-nitrobenzyl moieties were cleaved, and hydrophobic PNBA was transformed to hydrophilic poly(acrylic acid) (PAA), leading to the photoinduced dissociation of micelles to unimers. As a result, the oxime units of P1 were exposed to a hydrophilic environment and could react with mercury(II) ions to form nitrile groups, resulting in the turn-on detection of mercury(II) ions by UV light irradiation.

2-(Hydroxyimino)aldehydes: Photo- and Physicochemical Properties of a Versatile Functional Group for Monomer Design

In the context of our research on stimuli-responsive polymers bearing the 2-(hydroxyimino)aldehyde (HIA) group, we have explored the photochemical behavior and physicochemical properties of a number of HIAs. Interpretation of the experimental data is supported by quantum mechanical calculations. HIAs are expected to undergo photoisomerization, chelate metal ions, yield hydrogen-bonded dimers or oligomers, exhibit relatively low pK_a s, and form >C=NO^. radicals through OH hydrogen abstraction or oxidation of the oximate ion. Besides the well-established E/Z oxime photoisomerism, we observed a Norrish-Yang cyclization resulting in cyclobutanol oximes, to our knowledge not previously described in the literature. The acidity, bond dissociation enthalpies, and electrochemical properties of the HIAs are compared with literature data of simple oximes. The results are discussed in relation to the many potential applications for HIAs, with emphasis on the synthesis of novel HIA-containing responsive polymers.

A coumarin Schiff's base two-photon fluorescent probe for hypochlorite in living cells and zebrafish

Selective and sensitive fluorescent probes for ClO⁻ are desirable due to the importance of ClO⁻ in biological processes. Here, a coumarin Schiff's base, compound 1, has been developed and successfully used as a one- and two-photon fluorescent probe for ClO⁻ with high selectivity. This probe can recognize ClO⁻ with obvious color change from yellow-green to colorless and green to blue fluorescence emission, which can be observed by the naked eye. The properties of low cytotoxicity and good cell permeability allow it to be used for ClO⁻ detection in living cells and zebrafish by both one- and two-photon microscopy imaging. All these results indicate that the compound is a sensitive probe with potential for analysis of ClO⁻ in biological samples. The mechanism by which probe 1 recognizes ClO⁻ is possibly nucleophilic addition followed by hydrolysis.

A coumarin Schiff's base compound can selectively recognize ClO⁻ and can be successfully applied to the detection of ClO⁻ in living cells and zebrafish by one- and two-photon fluorescence modes.

BODIPY-derived multi-channel polymeric chemosensor with pH-tunable sensitivity: selective colorimetric and fluorimetric detection of Hg2+ and HSO4− in aqueous media

A water-soluble BODIPY-containing polymeric chemosensor was synthesized for the selective colorimetric and turn-on fluorimetric detection of Hg²⁺ and HSO₄⁻ ions, respectively, in 100% aqueous media at physiological pH.

Hypochlorite-promoted inhibition of photo-induced electron transfer in phenothiazine–borondipyrromethene donor–acceptor dyad: a cost-effective and metal-free “turn-on” fluorescent chemosensor for hypochlorite

APTZ-BODIPY based fluorescent chemosensor was designed and used for hypochlorite detection.

A single fluorescent probe for multiple analyte sensing: efficient and selective detection of CN−, HSO3− and extremely alkaline pH

A water-soluble broadly emitting (500–650 nm) fluorescent probe (IECBT) for the selective and sensitive detection of multiple analytes, including CN⁻, HSO₃⁻ and extremely alkaline pH, is designed and synthesized.