Sujoy Das

Pyrene appended thymine derivative for selective turn-on fluorescence sensing of uric acid in live cells

A new ‘turn-ON’ fluorescent probe, pyrene appended thymine acetamide (PTA), with high sensitivity and selectivity for the detection of uric acid (UA) was developed and first time imaging of uric acid in living cells in water was achieved. 1H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between probe PTA and UA.

Simple Bisthiocarbonohydrazone as a Sensitive, Selective, Colorimetric, and Ratiometric Fluorescent Chemosensor for Picric Acids

A bisthiocarbonohydrazone-based chemosensor molecule (R1) containing a tetrahydro-8-hydroxyquinolizine-9-carboxaldehyde moiety has been synthesized and characterized as a new ratiometric fluorescent probe for picric acid (PA). The ratiometric probe R1 is a highly selective and sensitive colorimetric chemosensor for PA. The association between the chemosensor and PA and the ratiometric performance enabled by the key role of excited state intramolecular proton transfer in the detection process are demonstrated. Selectivity experiments proved that R1 has excellent selectivity to PA over other nitroaromatic chemicals. Importantly, the ratiometric probe exhibited a noteworthy change in both colorimetric and emission color, and this key feature enables R1 to be employed for detection of PA by simple visual inspection in silica-gel-coated thin-layer chromatography plates. Probe R1 has been shown to detect PA up to 3.2 nM at pH 7.4. Microstructural features of R1 and its PA complex have been measured by a field emission scanning electron microscope, and it clearly proves that their morphological features differ dramatically both in shape and size. Density function theory and time-dependent density function theory calculations were performed to establish the sensing mechanism and the electronic properties of probe R1. Furthermore, we have demonstrated the utility of probe R1 for the detection of PA in live Vero cells for ratiometric fluorescence imaging.

“Turn-on” fluorescence sensing of cytosine: development of a chemosensor for quantification of cytosine in human cancer cells

A simple new chemosensor, pyrene-appended 5-hydroxyisophthalic acid derivative (PIA), was developed and characterized for selective detection and quantification of cytosine in different human cancer cells. PIA shows “turn-on” fluorescence in presence of cytosine through intermolecular hydrogen bonding with a detection limit of 32 nM at neutral pH.

Visualisation of DCP, a nerve agent mimic, in Catfish brain by a simple chemosensor

A chemosensor, 3-aminophenol-based rhodamine conjugate (ARC) has been developed for visualisation of diethylchlorophosphate (DCP), mimic of a chemical warfare agent, in Catfish brain. The simple detection of DCP by “turn-on” fluorescence property of the chemosensor makes it unique for easy and rapid in vivo and in vitro detection of DCP with the detection limit of 5.6 nM.

Consumption of H2S from Our Daily Diet: Determination by a Simple Chemosensing Method

A unique method has been developed for comparative analysis of H2S produced from food samples from our daily diet, both qualitatively and quantitatively. The selective detection of H2S has been executed by introducing a simple chemodosimeter (PN-N3) that gives response on the basis of intramolecular charge transfer. UV–vis, fluorimetric, and NMR titrations were performed to demonstrate the sensing mechanism and electronic environment of PN-N3 in the presence of H2S. Density functional theory calculations were performed to validate the mechanism of azide (PN-N3) reduction to amine (PN-NH2) by the strong reducing power of H2S. The potentiality of this chemosensing method is that it could be treated as a simple, less-time-consuming, and cost-effective method for determining H2S in biological samples in the nanomolar range.