A Novel Colorimetric and Fluorometric Dual-Channel Chemosensor based on A Conjugated Perylene-Benzothiazole System for Highly Selective Detection of Cyanide in Aqueous Media

A novel cyanine compound based on the conjugated perylene-benzothiazole system (PBI) as a colorimetric and fluorometric dual-channel sensor for cyanide (CN- ) detection was synthesized and characterized via UV-vis and fluorescence spectroscopy. PBI exhibited a high sensitivity and rapid optical response for CN- due to the intramolecular charge transfer (ICT) mechanism. The detection limit of PBI for CN- was 1.15×10-7  M in the mixture of DMSO/H2 O (1 : 1, v/v). Moreover, probe PBI demonstrated high selectivity and sensitivity for CN- over other common anions, including Cl- , Br- , F- , I- , AcO- , ClO4 - , HSO4 - , SO4 2- , NO2 - , NO3 - and SCN- . This work provided a simple and effective approach to trace the toxic CN- ion with rapid response, high selectivity, and sensitivity that is possibly applied in environmental control and agricultural management.

Recent development of small-molecule fluorescent probes based on phenothiazine and its derivates

Fluorescence probes, as analytical tools with the ability to perform rapid and sensitive detection of target analytes, have made outstanding contributions to environmental analysis and bioassays. Considering the expanding developments in these areas, fluorophores play a key role in the de-sign of fluorescence probes. Compared to classical fluorophores, phenothiazines with elec-tron-rich characteristics have been widely applied to construct electron donor-acceptor dyes, which exhibit outstanding performance in both fluorimetric and colorimetric analysis. In addition, these probes also exhibit the pronounced ability in both solution and solid-state, achieving portable detection for environmental analysis. In this review, we summarize recent advances in the performance of phenothiazine-based fluorescent probes for detecting various analytes, especially in cations, anions, ROS/RSS, enzyme and other small molecules. The general design rules, response mechanisms and practical applications of the probes are analyzed, followed by a discussion of exiting challenges and future research perspectives. It is hoped that this review will provide a few strategies for the development of phenothiazine-based fluorescent probes.

Naked-Eye Chromogenic Test Strip for Cyanide Sensing Based on Novel Phenothiazine Push-Pull Derivatives

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.

Colorimetric recognition of hydrazine in aqueous solution by a bromophenol blue-tethered ion-pair-like ratiometric probe

Hydrazine or hydrazine hydrate (N₂H₄·H₂O) is a potential neurotoxin and has several mutagenic effects in physiological systems. Therefore, the development of synthetic organic probes that are sensitive and selective to hydrazine is of tremendous importance. Unfortunately, however, the hydrazine-selective sensing probes that rely upon minimum usage of the organic solvents (≤5%, v/v) are still rarer. In this work, an ion-pair-like mono acetate derivative of bromophenol blue has been developed as a fairly selective ratiometric probe for the naked-eye recognition of hydrazine in a solution of tris buffer and EtOH (19:1, v/v) at physiological pH. The chromogenic signalling relies upon hydrazine-induced cleavage of an ester moiety of the probe to its resonance stabilized quinonoid form, resulting in momentous variations in its spectrophotometric profile. Meanwhile, the colour of the probe solution changed from mustard yellow to blue within few minutes. This sensing assay could be successfully applied in the recognition of hydrazine in real environmental and pharmaceutical samples with satisfactory recoveries. Given the cost-effectiveness, simplicity and versatility, for instance, direct analysis of colorimetric probes, it is reasonable to propose that the present method can serve as a complementary method for prompt inspection of hydrazine in boiler feed water.

Tandem Detection of Sub-Nano Molar Level CN- and Hg2+ in Aqueous Medium by a Suitable Molecular Sensor: A Viable Solution for Detection of CN- and Development of the RGB-Based Sensory Device

An inimitable urea-based multichannel chemosensor, DTPH [1,5-bis-(2,6-dichloro-4-(trifluoromethyl)phenyl)carbonohydrazide], was examined to be highly proficient to recognize CN- based on the H-bonding interaction between sensor -NH moiety and CN- in aqueous medium with explicit selectivity. In the absorption spectral titration of DTPH, a new peak at higher wavelength was emerged in titrimetric analytical studies of CN- with the zero-order reaction kinetics affirming the substantial sensor-analyte interaction. The isothermal titration calorimetry (ITC) experiment further affirmed that the sensing process was highly spontaneous with the Gibbs free energy of -26 × 104 cal/mol. The binding approach between DTPH and CN- was also validated by more than a few experimental studies by means of several spectroscopic tools along with the theoretical calculations. A very low detection limit of the chemosensor toward CN- (0.15 ppm) further instigated to design an RGB-based sensory device based on the colorimetric upshots of the chemosensor in order to develop a distinct perception regarding the presence of innocuous or precarious level of the CN- in a contaminated solution. Moreover, the reversibility of the sensor in the presence of CN- and Hg2+ originated a logic gate mimic ensemble. Additionally, the real-field along with the in vitro CN- detection efficiency of the photostable DTPH was also accomplished by using various biological specimens.

A sensitive photoluminescent chemosensor for cyanide in water based on a zinc coordination polymer bearing ditert-butyl-bipyridine

Sensitive and direct sensing of cyanide in buffered aqueous solutions at pH = 7.0 by three new blue photoluminescent zinc-1,4-cyclohexanedicarboxylato coordination polymers bearing di-alkyl-2,2′-bipyridines has been achieved.

A highly selective fluorescent and chromogenic probe for CN- detection and its applications in bioimaging

In this study, 3-ethyl-2-methylbenzothiazolium iodide and nitrophenyl-2-furancarboxaldehyde were used to synthesize a new fluorescent and chromogenic dual channel signal cyanide ion probe M, which showed high selectivity towards CN^- analysis and strong antijamming capability towards other anions. When CN^- is present in the solution, probe M indicates an obvious blue shift in UV-vis absorbance spectra, which can be observed clearly by unaided eyes. The limits of detection (LODs) of CN^- based on fluorescence and UV-vis absorbance were 0.11 μM and 0.16 μM, respectively. The mechanism of fluorescent and chromogenic cyanide ion detection refers to the nucleophilic addition of cyanide ion to carbon atom of -C˭N- in the benzothiazole. The π-conjugation and ICT transition between furfural and benzothiazole were broken due to this non-reversible reaction, resulting in the color change and fluorescent characterizations. In addition, probe M also showed the excellent optical properties and high biocompatibility, which enables the practical application of CN^- tracing in biomedical systems.

10-[1,1-Dichloro-4-(trimethylsilyl)but-1-en-3-yn-2-yl]-10H-phenothiazine

The title compound, C19H17Cl2NSSi, is an enamine derivative, in which the N atom adopts a shallow trigonal–pyramidal geometry [displacement from the plane of its attached C atoms = 0.1383 (18) Å]. The dihedral angle between the plane through the three amino carbon atoms and the vinyl group is 89.47 (7)°. The phenothiazine unit has a butterfly structure and the central six-membered ring adopts a boat conformation. The fold angle between the benzene rings is 28.52 (7)°. The crystal structure features weak Csp3—H...Cl hydrogen bonds, H...S contacts and π–π stacking interactions between phenothiazine units.

A benzopyrylium–phenothiazine conjugate of a flavylium derivative as a fluorescent chemosensor for cyanide in aqueous media and its bioimaging

A new benzopyrylium–phenothizine conjugate (BP) has been synthesized for CN⁻sensing.

A novel graphene-based label-free fluorescence 'turn-on' nanosensor for selective and sensitive detection of phosphorylated species in biological samples and living cells

A novel label-free fluorescence 'turn-on' nanosensor has been developed for highly selective and sensitive detection of phosphorylated species (Ps) in biological samples and living cells. The design strategy relies on the use of Ti(4+)-immobilized polydopamine (PDA) coated reduced graphene oxide (rGO@PDA-Ti(4+)) that serves as an attractive platform to bind riboflavin 5'-monophosphate molecules (FMNs) through ion-pair interactions between phosphate groups and Ti(4+). The as-prepared rGO@PDA-Ti(4+)-FMNs (nanosensor), fluoresce only weakly due to the ineffective Förster resonance energy transfer between the FMNs and rGO@PDA-Ti(4+). The experimental findings revealed that the microwave-assisted interaction of the nanosensor with α-, β-casein, ovalbumin, human serum, non-fat milk, egg white, and living cells (all containing Ps) releases FMNs (due to the high formation constant between phosphate groups and Ti(4+)), leading to an excellent fluorescence 'turn-on' response. The fluorescence spectroscopy, confocal microscopy, and MALDI-TOF MS spectrometry were used to detect Ps both qualitatively and quantitatively. Under the optimized conditions, the nanosensor showed a detection limit of ca. 118.5, 28.9, and 54.8 nM for the tryptic digests of α-, β-casein and ovalbumin, respectively. Furthermore, the standard addition method was used as a bench-mark proof for phosphopeptide quantification in egg white samples. We postulate that the present quantitative assay for Ps holds tremendous potential and may pave the way to disease diagnostics in the near future.

Off–on fluorometric detection of cyanide anions in an aqueous mixture by an indane-based receptor

An indanedione–coumarin conjugate behaves as an off–on type fluorescent receptor for rapid, selective, and sensitive detection of cyanide anions in an aqueous mixture via a nucleophilic interaction with the electrophilic β-carbon of the receptor.

A reversible fluorescent chemosensor for the rapid sensing of CN− in water: utilization of the intramolecular charge transfer blocking

A reversible fluorescent sensor combines naphthyridine groups as signaling subunits and the presence of the active hydrogen of the primary amine confers the recognition capacity toward cyanide ions in water.

Benzoindolium–triarylborane conjugates: a ratiometric fluorescent chemodosimeter for the detection of cyanide ions in aqueous medium

A new ratiometric fluorescent chemodosimeter has been synthesized and characterized that exhibits high selectivity and sensitivity toward CN⁻ ions in aqueous medium.

Graphene-Based Nanomaterials as Efficient Peroxidase Mimetic Catalysts for Biosensing Applications: An Overview

"Artificial enzymes", a term coined by Breslow for enzyme mimics is an exciting and promising branch of biomimetic chemistry aiming to imitate the general and essential principles of natural enzymes using a variety of alternative materials including heterogeneous catalysts. Peroxidase enzymes represent a large family of oxidoreductases that typically catalyze biological reactions with high substrate affinity and specificity under relatively mild conditions and thus offer a wide range of practical applications in many areas of science. The increasing understanding of general principles as well as intrinsic drawbacks such as low operational stability, high cost, difficulty in purification and storage, and sensitivity of catalytic activity towards atmospheric conditions of peroxidases has triggered a dynamic field in nanotechnology, biochemical, and material science that aims at joining the better of three worlds by combining the concept adapted from nature with the processability of catalytically active graphene-based nanomaterials (G-NMs) as excellent peroxidase mimetic catalysts. This comprehensive review discusses an up-to-date synthesis, kinetics, mechanisms, and biosensing applications of a variety of G-NMs that have been explored as promising catalysts to mimic natural peroxidases.

Phenothiazine-based bipolar green-emitters containing benzimidazole units: synthesis, photophysical and electroluminescence properties

A series of bipolar green emitters bearing hole-transporting phenothiazine and electron-transporting N-phenylbenzimidazole are synthesized and characterized by their photophysical, electrochemical and thermal properties.

Fluorescent probes for the detection of cyanide ions in aqueous medium: cellular uptake and assay for β-glucosidase and hydroxynitrile lyase

A chemodosimetric reagent for specific detection of cyanide species and its possible use in imaging applications as well as assay development for important enzymes.