High selectivity of colorimetric detection of p-nitrophenol based on Ag nanoclusters

Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) with different terminal groups and molecular weights had been developed as a special optical sensor for detecting p-nitrophenol (p-NP). When adding p-NP into Ag NCs, an obvious color change from pale yellow to deep yellow could be observed by naked eyes, accompanying with an apparent red-shift of absorption peak, and the reason was attributed to the formation of oxygen anion of p-NP based on the transfer of H + from p-NP to amine groups of PEI. The molecular weights of template would greatly affect the sensitivity of p-NP. Ag NCs capped by PEI terminated ethylenediamine (EDA) possessed better sensitivity than other Ag NCs, showing good linear range from 5 to 140   μM with the limit of detection as low as 1.28   μM. Most importantly, this present system displayed high selectivity toward p-NP even in the presence of other nitrophenols and nitrotoluenes . This reliable method had been successfully applied for the detection of p-NP in real water and soil samples.