Selective colorimetric detection of copper (II) by a protein-based nanoprobe.

In this work, we report a novel protein-based nanoprobe (PNP) that can be employed for quantitative analysis of Cu in pure water medium and real samples. Structurally, the proposed nanoprobe comprises a biofriendly protein (hen egg-white lysozyme (HEWL)) and a Cu-specific chromogenic agent, where HEWL acts as a nanocarrier encapsulating a structurally tailored rhodamine B derivate. The resulting PNP exhibits a hydrodynamic diameter of ~ 106 nm and efficiently disperses in water, enabling the detection of Cu in pure aqueous systems without the aid of any organic co-solvents. The high sensitivity and selectivity of PNP allow the colorimetric detection of Cu in the presence of other metal interferents with a low detection limit of 160 nM. The satisfying recovery of trace level Cu in environmental samples demonstrate the great potential of employing PNP for the determination of Cu in actual applications. Most importantly, the simple co-grinding method employing proteins and chromogenic agents provides a novel strategy to generate sensing systems that are useful detection of pollutants in aqueous samples.