We have developed a novel approach to the rapid visual
detection of Cu2+ in natural samples based on the copper-mediated
leaching of gold nanorods (GNRs). In the presence of hexadecyltrimethylammonium
bromide, which can reduce the redox potential of Au(I)/
Au, the GNRs are catalytically etched by Cu2+ preferentially along the
longitudinal direction. And as a result, the localized surface plasmon
resonance extinction peak shifts to short wavelength, accompanied by a
color change from blue to red. The leaching mechanism has been carefully
discussed in a series of control experiments. Under optimal conditions, this
sensor exhibits good sensitivity (LOD = 0.5 nM). Most importantly, the
approach is highlighted by its high selectivity for and tolerance of
interference, which enables the sensor to detect Cu2+ directly in a complex
matrix, especially in seawater. Moreover, such a nanoparticle-based sensor
is also successfully applied to test paper for the visual detection of Cu2+.