Rahul Kaushik

Alizarin red S–zinc(II) fluorescent ensemble for selective detection of hydrogen sulphide and assay with an H2S donor

A new Alizarin Red S based fluorescent probe ARS–Zn(II) has been reported for the detection of H2S in aqueous buffer solution. In the presence of zinc ions, ARS displayed an increase in fluorescence intensity through the formation of an ARS–Zn(II) ensemble. The addition of H2S to the ensemble caused the disassembly of the metal and ARS, which restored the fluorescence intensity of ARS. This sensing ensemble exhibited H2S-selectivity over other biothiols and biologically relevant analytes. The calculated detection limit of ARS–Zn(II) with H2S was 92 nM. ARS–Zn(II) also detected H2S in serum under physiological conditions. Moreover, as a practical application, it could be used for the real time monitoring of H2S released from the H2S-donor molecule benzoic (methyl carbonic) dithioperoxyanhydride and also applied to live cell imaging. The reported ensemble ARS–Zn(II) has advantages like ready availability, high selectivity with good sensitivity, fast response time, higher excitation (520 nm) and emission (625 nm) wavelengths and real time fluorescence assay with H2S donors.

Anion responsive and morphology tunable tripodal gelators

We report the syntheses and characterization of three isomers of trisamide tripodal derivatives. All these compounds act as low-molecular-weight gelators and the variation of the gel morphology with respect to the solvent combination has been analysed. The anion binding studies revealed that these tris-amide derivatives also act as suitable receptors for appropriate analytes. In this work, we have explored the role of geometry or extent of receptor–anion interaction on the gel architecture in the presence of anions such as F−, CN−, CH3COO− and H2PO4−. We have discussed the anion responsive gel formation of one isomer after incorporation of anions in the solution phase as well as into the gel morphology.

Colorimetric sensor for the detection of H2S and its application in molecular half-subtractor

Azine based new colorimetric sensor 1 for the detection of gasotransmitter H2S has been reported. Sensor 1 used to detect the H2S with a remarkable red shift of 105 nm in the absorption spectra with a colour change from light yellow to brown red. Importantly, rare example of azine derivative has been used as a colorimetric probe for H2S detection using deprotonation mechanism. H2S induced deprotonation of one of the -OH proton followed by a change in resonance of 1 is responsible for the ratiometric spectral and colour change. The detection response was quick and the LOD calculated as 18.2 μM. Sensor 1 was also explored in the detection of H2S in biological fluids such as human serum and mouse serum. Moreover, for the first time, we have shown the applicability of H2S for the construction of half subtractor molecular logic gate.

Selective Detection of H2S by Copper Complex Embedded in Vesicles through Metal Indicator Displacement Approach

A new approach for the detection of hydrogen sulfide (H2S) was constructed within vesicles comprising phospholipids and amphiphilic copper complex as receptor. 1,2-Distearoyl- sn-glycero-3-phosphocholine (DSPC) vesicles with embedded metal complex receptor (1.Cu) sites have been prepared. The vesicles selectively respond to H2S in a buffered solution and show colorimetric as well as spectral transformation. Other analytes such as reactive sulfur species, reactive nitrogen species, biological phosphates, and other anions failed to induce changes. The H2S detection is established through a metal indicator displacement (MIDA) process, where Eosin-Y (EY) was employed as an indicator. Fluorescence, UV-vis spectroscopy, and the naked eye as the signal readout studies confirm the high selectivity, sensitivity, and lower detection limit of the vesicular receptor. The application of vesicular receptors for real sample analysis was also confirmed by fluorescence live cell imaging.