Efficient solid- and solution-state emissive reusable solvatochromic fluorophores for colorimetric and fluorometric detection of CN.

In this work, a novel organic receptor, CPI [(E)-3-(4-(9H-carbazol-9-yl)phenyl)-2-(1H-benzo[d]imidazol-2-yl)acrylonitrile], was rationally designed and successfully fabricated for selective and sole recognition of CN- ions over other competitive anions through an obvious chromogenic and ratiometric emission change in DMSO. The distinct and prominent color change upon the addition of CN- can be attributed to the typical ICT process, which is induced by the deprotonation of acidic NH protons in the imidazole moiety. The sensor displayed strong solvatochromic effects in commonly used organic solvents such as n-hexane, toluene, diethyl ether, DCM, THF, DMF and DMSO. The chemical structure of the sensor was characterized by single-crystal X-ray diffraction, 1HNMR, 13CNMR, IR and mass spectroscopy. Significantly, the probe can function as a fluorescence-based sensor for the efficient detection of low-level water in organic solvents. The solid-state emission properties of CPI were successfully applied to recognise cyanide in a solid-state platform with naked eye-visualized distinct color change. The probe can be made reusable by adding TFA into the CN- treated probe solution. The detection limit of CPI towards CN- was determined to be 4.48 × 10-8 M. More importantly, the sensor is capable of detecting CN- in food samples and has been employed for wastewater treatment. Besides, easy-to-prepare CPI-coated test strips provide a simple, reusable and easy-to-handle protocol for the qualitative identification of CN- conveniently. Finally, density functional theory and time-dependent density functional theory were performed to verify the experimental outcomes theoretically.

A chemodosimetric approach for the visual detection of nerve agent simulant diethyl chlorophosphate (DCP) in liquid and vapour phase.

In this work, a novel fluorescent ratiometric switch, 8-((6-(1H-benzo[d]imidazol-2-yl)pyridin-2-yl)methoxy)quinoline (BIPQ), has been introduced for sensing an organophosphorus (OP) chemical vapor threat, diethyl chlorophosphate (DCP), the low-toxic mimic of the real nerve agent sarin (GB). BIPQ is efficient at detecting DCP in both solution and gaseous phase and has potential practical application with high sensitivity and selectivity. The probe shows significant ratiometric emission in the presence of DCP along with a distinct color change from blue to cyan under UV light. The sensing mechanism of the chemodosimeter is based on the generation of a new adduct, BIPQ-DCP, through a nucleophilic substitution reaction with DCP followed by a ring-closure process to form the final product. The detection limit of BIPQ for DCP was determined to be in the order of 10-8 (M) in the liquid state. DFT and TDDFT computational techniques were carried out in order to interpret the electronic properties theoretically.

A biphenyl thiosemicarbazide based fluorogenic chemosensor for selective recognition of Cd2+: application in cell bioimaging.

A diversified biphenyl thiosemicarbazide based chemosensor (HBMC) has been fabricated and reported for the specific detection of Cd2+ in a MeOH : H2O (4 : 1) solution. We observed a chromogenic change from colorless to light yellow colour, and it showed a "turn-on" fluorogenic change from non fluorescent to blooming cyan colour. In fluorometric titration a sharp "turn-on" emission for Cd2+ was observed with a ∼16 fold increase in fluorescence intensity value at 496 nm by incremental addition of Cd2+ ions in the MeOH : H2O (4 : 1) solution. The reversibility of the chemosensor (HBMC) was confirmed by a sequential addition of the EDTA solution. Again the binding stoichiometry of HBMC with Cd2+ was found to be 2 : 1, as confirmed by Job's plot analysis and HRMS spectra of the HBMC-Cd2+ complex. The mechanism for Cd2+ sensing in MeOH : H2O (4 : 1) is based upon the inhibition of CN isomerization and ESIPT process and simultaneously turning on the CHEF (chelation enhanced fluorescence) process. The limit of detection for Cd2+ was found to be in the order of 10-8 (M), which implies that HBMC is an efficient probe to detect Cd2+ at the microscopic level. A reusability study was performed and on-sight detection of cadmium ions by the chemosensor (HBMC) was established by dip-stick experiment. In vitro detection of Cd2+ in human breast cancer cells (MDA-MB-231) by HBMC discloses its cell permeability and biocompatible nature. Computational studies (DFT and TDDFT) with the probe HBMC and HBMC-Cd2+ complex were also performed.

Fabrication of a New Coumarin Based Fluorescent "turn-on" Probe for Distinct and Sequential Recognition of Al3+ and F- Along With Its Application in Live Cell Imaging.

A new coumarin based fluorescent switch PCEH is fabricated which displays high selective sensing towards Al3+ among other metal cations at physiological pH. On gradual addition of Al3+, PCEH shows a brilliant "turn-on" emission enhancement in MeOH/H2O (4/1, v/v) solution. This new fluorescent switch is proven to be a reversible probe by gradual addition of F- into the PCEH-Al3+ solution. Detection limit as well as binding constant values are calculated to be in the order of 10-9 M and 104 M-1 respectively. We have also explored its potential as a biomarker in the application of live cell imaging using breast cancer cells (MDA-MB-231 cell).