Virtually specific UV-molecular probe for nitrite sensing

1607-1612  A highly sensitive and selective UV-molecular probe has been developed for detection of low concentrations of nitrite in aqueous solution based on monotonous increase in absorbance of rhodamine 6G at 385 nm. Addition of nitrite also results in a bathochromic shift in UV absorption maximum of rhodamine 6G from 355 to 385 nm. The optimal conditions for parameters like concentration of H2SO4 and rhodamine 6G, response time and stability is reported. Under optimised conditions, the developed UV-probe enables the determination of 0 to 0.5 mgL-1 of nitrite. On the other hand, the addition of other anions like I-, SCN-, ClO4-, [HgI4]2- and [Zn(SCN)4]2- shows a bathochromic shift from 525 (the visible range absorption maximum) to 575 nm with no perceptible absorption at 385 nm. This enabled a virtually specific UV-molecular probe for rapid, precise and reliable monitoring of traces of nitrite in environmental samples and food materials with no interference from other anionic or cationic species. Studies with pyronine G also exhibit similar spectral characteristics on addition of nitrite. </span

Simple and Cost-Effective Quantum Dot Chemodosimeter for Visual Detection of Biothiols in Human Blood Serum

An emission “turn-off” chemodosimeter for the naked-eye detection of biothiols using silica-overcoated cadmium selenide quantum dots is developed. Hole scavenging by the thiol group of cysteine, homocysteine, or glutathione on interaction with quantum dots resulted in an instant and permanent emission quenching under physiologically relevant conditions. Also, the emission suppression is so specific that thiols and substituted thiols (methionine and cystine) can easily be distinguished. A pilot experiment for the visual detection of serum thiols in human blood was also conducted. Densitometry analysis proved the potential of this system as a new methodology in clinical chemistry and research laboratories for routine blood and urine analyses using a simple procedure. This method enables one to visually distinguish biothiols and oxidized biothiols, whose ratio plays a crucial role in maintaining “redox thiol status” in the blood