Amrita Chatterjee

Selective Fluorogenic and Chromogenic Probe for Detection of Silver Ions and Silver Nanoparticles in Aqueous Media

A novel rhodamine-based fluorogenic and chromogenic probe for Ag(+) ions in aqueous media is developed, which can be also used for the detection of AgNPs. The sensing mechanism is based on irreversible tandem ring-opening and -forming processes promoted by Ag(+)-coordination to the iodide of the probe, which is accompanied by both color and turn-on type fluorescence changes. The probe shows remarkably high selectivity over other metal ions and detects silver ions up to 14 ppb.

Reaction-Based Fluorescent Sensing of Au(I)/Au(III) Species: Mechanistic Implications on Vinylgold Intermediates

A rhodamine-derived alkyne shows turn-on fluorescence change only toward Au(I)/Au(III) species among various other metal species examined. A formyloxazole compound is formed as the major product in aqueous media, presumably via a vinylgold intermediate, which casts new mechanistic implications on vinylgold intermediates.

Fluorescence Turn-on Chemosensor for the Detection of Dissolved CO2 Based on Ion-Induced Aggregation of Tetraphenylethylene Derivative

Herein, a sensitive fluorimetric assay for dissolved carbon dioxide (dCO2) was developed by using ion-induced self-assembly of a tetraphenylethylene derivative by taking advantage of its aggregation induced emission property. Chitosan, a commercially available polymer having amine functionality was utilized for the ion induced assay. In the presence of dCO2, the amine groups in the chitosan get protonated to convert neutral chitosan to a positively charged species, triggering negatively charged tetraphenylethene derivative (probe 1) to aggregate with it by electrostatic interaction. The aggregation causes intense blue fluorescence output from the system. The extent of the aggregation is reliant on the charge density of polymer, which is equivalent to dCO2 concentration. A linear relationship from 5 to 50 μM of dCO2, with a limit of detection of 5 × 10(-6) M (0.00127 hPa) was obtained. This is the first report for detecting dCO2 utilizing the AIE property.

An aggregation-induced emission based “turn-on” fluorescent chemodosimeter for the selective detection of Pb2+ ions

An aggregation-induced emission (AIE) based “turn-on” fluorescent chemodosimeter for the selective detection of ascorbate ions has been developed, making use of the azide–alkyne “click” reaction between two tetraphenylethene (TPE) derivatives (propergyl–TPE and TPE–azide). The present method offers a rapid, economic and effective way to detect ascorbic acid (Vitamin C) in aqueous media with high selectivity and sensitivity.

A reaction based turn-on type fluorogenic and chromogenic probe for the detection of trace amount of nitrite in water

A turn-on fluorescent probe for the detection of nitrite ion in water is developed based on diazotization reaction of the amino group of the probe in an acidic solution (pH 1). The probe responds selectively to nitrite ion over various other anions with a turn-on type fluorogenic change from colorless to orange by the formation of rhodamine B via an analyte triggered fragmentation process. The fluorescence titration is complete within 1h with 1 equivalent of nitrite ion. The probe is highly efficient, cost-effective and shows a detection limit of 4.6 ppb.

A GREEN CHEMICAL APPROACH FOR THE N-ALKYLATION OF ALDOXIMES TO FORM NITRONES IN ORGANIZED AQUEOUS MEDIA AND THEIR IN SITU CYCLOADDITION WITH OLEFINS

Aldoximes react with α,β-unsaturated carbonyl and sulfonyl compounds in organized aqueous media (nanoreactor system) using dodecylbenzenesulfonic acid (DBSA) as surfactant to generate N-alkylated nitrones, which undergo intermolecular cycloaddition in the same pot with maleimides to give the desired cycloadduct in absence of any organic solvent and catalyst. Divinyl sulfone was successfully used for both N-alkylation and intramolecular cycloaddition, affording only one cycloadduct. This is a new example of green chemistry and provides a new aspect of reactions in water.

Amine functionalized tetraphenylethylene: a novel aggregation-induced emission based fluorescent chemodosimeter for nitrite and nitrate ions

A novel AIE-based fluorescent probe for the detection of trace amounts of nitrite and nitrate ions in water has been developed. The probe, a monoamine of tetraphenylethylene, spontaneously detects nitrites (or nitrates) by a fluorescence “turn-off” method via diazotization followed by formation of a non fluorescent TPE-azodye. The salient features of this method are high sensitivity and selectivity, cost effective synthesis, fast detection process and low detection limit.

Selective colorimetric sensing of geometrical isomers of dicarboxylates in water by using functionalized gold nanoparticles.

A colorimetric sensing system based on gold nanoparticles functionalized with a water-soluble anion-recognition motif, an o-(carboxamido)trifluoroacetophenone analogue, has been developed. The nanoparticle system selectively senses specific isomers of dicarboxylates that are geometrically favorable for the binding-induced aggregation process; thus, it discriminates a trans-dicarboxylate fumarate from its cis-isomer maleate, and benzene-1,4-dicarboxylate from its isomeric benzene-1,2-and benzene-1,3-dicarboxylates in water, exhibiting a color change from red to blue.

A PEGylated-rhodamine based sensor for “turn-on” fluorimetric and colorimetric detection of Hg2+ ions in aqueous media

A water soluble turn-on fluorescent probe for the detection of mercury ions in water is developed by appending a water-compatible PEG-unit onto a rhodamine derivative. The probe, Rh1 responds to Hg2+ ions with an intense pink colour and orange fluorescence due to Hg2+ ion-induced opening of the spirolactam ring with high selectivity and sensitivity. The Jobs plot reveals that a 1 : 1 stoichiometry was most favourable for the binding mode of Hg2+ and the probe. Preliminary studies revealed that the probe molecule is fairly non-toxic and can successfully penetrate the cell surface of HeLa cells and interact with intercellular Hg2+ ions, indicating its usefulness for monitoring Hg2+ ions in biological samples as well. The probe is highly efficient, cost-effective and shows a low detection limit of 0.14 ppm.

d-Glucose derived novel gemini surfactants: synthesis and study of their surface properties, interaction with DNA, and cytotoxicity

Four new D-glucose derived m-s-m type gemini surfactants with variable spacer and tail length have been synthesized by a simple and efficient synthetic methodology utilizing the free C-3 hydroxy group of diisopropylidene glucose. The synthetic route to these gemini surfactants with a quaternary ammonium group as polar head group involves a sequence of simple reactions including alkylation, imine formation, quaternization of amine etc. The surface properties of the new geminis were evaluated by surface tension and conductivity measurements. These gemini surfactants showed low cytotoxicity by MTT assay on HeLa cell line. The DNA binding capabilities of these surfactants were determined by agarose gel electrophoresis, fluorescence titration, and DLS experiments. The preliminary studies by agarose gel electrophoresis indicated chain length dependent DNA binding abilities, further supported by ethidium bromide exclusion experiments. Two of the D-glucose derived gemini surfactants showed effective binding with pET-28a plasmid DNA (pDNA) at relatively low N/P ratio (i.e., cationic nitrogen/DNA phosphate molar ratio).