Modified photochemical strategy to support highly-purity, dense and monodisperse Au nanospheres on graphene oxide for...

The integration of highly-purity, dense and monodisperse plasmonic nanoparticles (NPs) on two-dimensional (2D) graphene-like support possesses great potential for optimizing surface-enhanced Raman spectroscopy (SERS). Based on ultraviolet (UV) laser-induced modified photochemical reaction, we report an ingenious and green strategy to support highly dispersed Au NPs with controllable distribution on graphene oxide (GO). Without using any stabilizing agents or other complex chemical additives, the GO with abundant oxygen-containing functional groups can be effectively excited by 375 nm laser irradiation in HAuCl₄ solution, resulting in controlled reduction of Au ions and then overgrowth of highly-purity Au NPs. Highly dense and monodisperse Au NPs with uniform diameter of ~20 nm formed on GO supports can be achieved by 30 min irradiation, which can offer maximized SERS activity in comparison with GO/Au NPs obtained by other irradiation times. The optimized GO/Au NPs give rise to ultralow SERS analyses of (10^-14 M) methylene blue (MB), (10^-13 M) rhodamine 6G (R6G) and (10^-13 M) malachite green (MG), respectively. More importantly, it can also simultaneously analyze these three aromatic dyes in a mixture condition at detection limits as low as nano-mole level (10^-9-10^-11 M), achieving the urgent requirement of mutually independent SERS trace detection. Therefore, the obtained GO/Au NPs with extremely high SERS activity and superior spectroscopic identification will be a prominent candidate for widespread SERS applications in real-word scenarios.