Polyamine-capped gold nanorod as a localized surface Plasmon resonance probe for rapid and sensitive copper(II) ion detection

Polyamine-capped gold nanorods (AuNRs) were developed as nanoprobes for localized surface Plasmon resonance (LSPR)-based simple, selective, and sensitive detection of Cu2+ ions. Poly(sodium-4-styrenesulfonate) (PSS) and polyethylenimine (PEI) was successively adsorbed on the positively charged AuNRs via electrostatic adsorption, resulting in polyamine-capped AuNRs (called PEI-PSS-AuNRs thereafter), in which PEI offered bifunctions of providing sufficient positive charges and static hindrance to ensure stability of the AuNRs and serving as a Cu2+ ion recognition molecule via specific chelation. The as-prepared PEI-PSS-AuNRs were characterized by UV-vis spectroscopy, zeta potential analyzer, and transmission electron microscopy (TEM). Experimental results show that the polyelectrolytes HS and PEI have been successfully adsorbed on AuNRs. The PEI-PSS-AuNRs were then employed as nanoprobes for Cu2+ ion detection. A linear range from 1 mu M to 5 mM and a detection limit (3 sigma/k) of 0.24 mu M were achieved in PBS. The concentration dependent shifts of longitudinal extinction peak of PEI-PSS-AuNRs notably results from the specific PEI-Cu2+ chelation-induced changes of dielectric property of polyelectrolyte film attached on nanoprobes. The negligible interference from other metal ions demonstrates good selectivity of the PEI-PSS-AuNRs for Cu2+ sensing. Moreover; the developed probes were successfully used to detect Cu2+ in river water, demonstrating their feasibility for analysis of surface water sample. (C) 2014 Elsevier Inc. All rights reserved.