A sensitive and selective BINOL based ratiometric fluorescence sensor for the detection of cyanide ions

Fluorescence-based ratiometric sensors as emerging tools for CN- detection: Chemical structures, sensing mechanisms and applications

Hazardous cyanide anions (CN-) are increasingly threatening the environment and human health due to their widespread use in industry and many other fields. Over the past three decades, a large number of probes have been reported to sensitively and selectively detect this toxic anion, while a rather limited number of ratiometric fluorescent probes have been developed. The ratiometric probes have significant potential in bio-imaging and biomedical applications because of the ability to detect CN- in a quick, convenient and affordable way. In this review, we introduce 42 ratiometric fluorescent probes reported in the past 6 years (2018-2023) for CN- detection. Our description includes the chemical structures, photo-physical properties, CN- sensing mechanisms, solution color changes, limits of detection (LODs) and/or various applications of these chemical probes. This review provides guidelines for design and development of a new ratiometric probe for effective CN- detection.

Selective visualization of cyanide in food, living cells and zebrafish by a mitochondria targeted NIR-emitting fluorescent probe

Cyanide is a highly toxic substance, and the detection of cyanide in the environment and food samples is critical to public health care. Herein, we rationally designed a mitochondria-targeted near-infrared fluorescent probe BTC for ratiometric monitoring of CN^- in water, food, living cells, and zebrafish. BTC exhibits a remarkable colorimetric ratiometric fluorescence response to CN^- with high selectivity, low detection limit (54.3 nM), and large Stokes shift. The cyanide sensing mechanism was demonstrated by NMR and ESI-MS analysis and density functional theory (DFT). More importantly, BTC was used for efficient naked-eye colorimetric detection of CN^- in sprouting potatoes, almonds, and ginkgo fruit samples. Further, the BTC is capable of situ tracking and imaging cyanide in mitochondria of SMMC-7721 cells and in zebrafish via dual emission channels, and was prepared into a kit for convenient and visual on-site sensing of cyanide in food samples.

Zinc ion detection using a benzothiazole-based highly selective fluorescence "turn-on" chemosensor and its real-time application

A new photochromic fluorescence chemosensor was devised and effectively synthesized using benzothiazole and imidazopyridine derivatives. A "turn-on" fluorescence sensor BIPP for Zn²⁺ detection was developed and has a quick response, excellent sensitivity, and remarkable selectivity over other metal ions. When Zn²⁺ was added to the BIPP solution, a new strong fluorescence emission peak at 542 nm formed with a considerable increase in intensity. The fluorescence color of the BIPP solution changed from blue to bright green. The binding ratio 8 : 2 was found between BIPP and Zn²⁺ by the results of Job's plot, HRMS and ¹H-NMR. The detection limit (LOD) of BIPP towards Zn²⁺ was determined to be 2.36 × 10^-8, which is remarkably low. The ability to detect Zn²⁺ in real water samples demonstrates that BIPP may also be used in environmental systems. Additionally, BIPP can be used to measure Zn²⁺ levels in living cells.

A coumarin coupled tetraphenylethylene based multi-targeted AIEgen for cyanide ion and nitro explosive detection, and cellular imaging

A coumarin coupled tetraphenylethylene based AIEgen (TPE-Lac) with an intense greenish-yellow emission has been synthesized and utilized for multipurpose sensing and imaging applications. TPE-Lac acts as a sensitive sensor for the detection of cyanide ions (CN^-) with an immediate turn-off response in the presence of many other interfering cations and anions. The limit of detection (LOD) was as low as 33 nM, which is well below the permissible limit set by the World Health Organization (WHO). Cyanide detection in the solid phase was successfully demonstrated by drop-casting the solution of the TPE-Lac probe on TLC plates and measuring and analysing the fluorescence response by ImageJ analysis. TPE-Lac was further employed in the detection of explosive nitroaromatics in solution and solid phases. Also, TPE-Lac was found suitable as an imaging agent and could easily percolate into live H520 cells giving bright fluorescence from the intra-cellular region. Easy and cost-effective synthesis, fast response and low LODs are some of the advantages of this AIEgen over available molecular probes for the same purpose.

A benzothiazole-based new fluorogenic chemosensor for the detection of CN− and its real-time application in environmental water samples and living cells

Since the cyanide ion is used in a wide range of industries and is harmful to both human health and the environment, a number of research efforts are dedicated to creating fluorescence sensors for the detection of cyanide (CN⁻). Herein, for the fluorescence detection of CN⁻, a new highly selective and sensitive sensor 2-(3-(benzo[d]thiazol-2-yl)-4-hydroxybenzylidene)-1H-indene-1,3(2H)-dione (BID) was created by conjugating a benzothiazole moiety with 1H-indene-1,3(2H)-dione. The donor and acceptor components of this hybrid receptor were covalently connected through a double bond. The nucleophilic addition of a cyanide anion to the BID inhibits the intramolecular charge transfer (ICT) transition, resulting in spectral and colour alterations in the receptor. When the solvent polarity was increased from n-hexane to methanol, this molecule exhibited a bathochromic shift in the emission wavelength (610 to 632 nm), suggesting the presence of a solvatochromic action. The sensor BID has shown strong specificity towards CN⁻ by interrupting its internal charge transfer (ICT), resulting in a significant change in the UV-vis spectrum and a notable blue shift in the fluorescence emission spectrum. The cyanide anion (CN⁻) is responsible for the optical alterations observed by BID, as opposed to the other anions examined. The detection limit was 5.97 nM, significantly less than the WHO's permitted amount of CN⁻ in drinking water. The experimental findings indicate that BID's fluorescence response to CN⁻ is pH insensitive throughout a wide pH range of 6.0 to 12.0. The interaction mechanism between the BID and CN⁻ ions has been studied by HRMS, ¹H-NMR titration experiments, FT-IR, and DFT, which confirmed the nucleophilic addition of CN⁻ on vinylidene and subsequent disturbance of ICT. Additionally, we demonstrated the real-time detection application of CN⁻ in environmental water samples and live-cell imaging.

Since the cyanide ion is used in a wide range of industries and is harmful to both human health and the environment, a number of research efforts are dedicated to creating fluorescence sensors for the detection of cyanide (CN⁻).