Large nanoparticle-induced enhancement of recognition selectivity for Cu2+ ion

A new fluorescent excited state intramolecular proton transfer compound, 2-(2-hydroxy-4-carbaldehydephenyl)benzoxazole (HCPBO), has been synthesized for the detection of Cu2+, based on its fluorescence quenching. In molecular monodispersed solution, the recognition selectivity for Cu2+ was poor as Co2+ and Ni2+ gave similar results in fluorescence quenching. However, the nanoparticles of HCPBO, prepared in ethanol–water (1:4, v/v), greatly enhanced the recognition selectivity for Cu2+. The mechanism was discussed as energy transfer (ET), energy migration (EM) and the more quantity of formed HCPBO–Cu2+ complex than other metal ions in the nanoparticle conditions enhanced the recognition selectivity for Cu2+ together.