Highly selective silver nanoparticles based label free colorimetric sensor for nitrite anions.

Highly selective label free colorimetric sensor based on AgNPs stabilized by phenolic chelating ligand, N,N'-bis(2-hydroxybenzyl)-1,2-diaminobenzene (1), for NO(2-) anions has been developed. Addition of NO(2-) showed selective decolourisation of brownish yellow colour of 1-AgNPs with the detection limit of 10(-7)M. Absorption studies showed the complete disappearance of 1-AgNPs peak at 426 nm due to the conversion of AgNPs to silver ions. The presence silver ions were confirmed by white precipitates of AgCl formation with NaCl. The interference studies confirmed the high selectivity of NO(2-) sensing in presence of anions as well as cations by 1-AgNPs. A linear relationship was observed between the change of absorption and concentration of NO(2-). The present approach could be performed at room temperature and ambient conditions. The practical applications of 1-AgNPs for selective sensing of NO(2-) in different water samples such as ground, river, pond and tap water have also been demonstrated.