Rhodamine B embedded silver nanogranules for selective sensing of l-cysteine.

Sensing of amino acid serves as the frontier research area for early diagnosis and monitoring various diseases. Among various amino acids, the sensing of L-Cysteine is much important for detection of human diseases like neurotoxic effect and coronary heart disease which arises due to excess of L-Cysteine. To address this, we propose a very simple method of L-Cys sensing via fluorescence "TURN ON" mechanism involving silver centred Rhodamine B nanogranules (AgNPs/RhB) stabilized via electrostatic interaction. The as-synthesized nanocomposite fluorescence probe shows highly selective sensing towards L-Cysteine aided by the preferential formation of stable covalent linkage between AgNPs and thiol group of L-Cys which is supported by FTIR and XPS study. The superior selectivity of L-Cysteine in presence of other amino acids and interactive ions with a limit of detection (LOD) of 1.084 µM and working linear range of 100-2200 µM makes the study a useful addition to the existing literature. The responsiveness of nanogranules to extreme conditions of ionic strength and pH further establishes its stability and suitability for present application. Moreover, the excellent recovery percentages obtained in real human serum samples establishes its effectiveness in diagnostic fields.