Shape and SPR evolution of thorny gold nanoparticles promoted by silver ions

The gold-seed-mediated growth approach is developed to obtain three-dimensional (3D) thorny gold nanoparticles, and their morphology can be tailored by introducing different amounts of Ag+ ions into the reaction systems of HAuCl4 and NH2OH in the absence of templates and surfactants. Changing the concentration of silver ions from 0 to 2.5 x 10(-6) M leads to the gradual deviations of the resulted nanoparticle morphology from the spherical geometry. The morphology of gold nanoparticles can be tuned from sphere to the anomalous nonspheres, to the gold nanoparticles with short thorns, to the gold nanoparticles with long thorns of more than 100 nm. At too high concentrations (above 2.5 x 10(-6) M), the number of the nanothorns on each gold nanoparticle decreased and the central parts of the 3D gold nanostructures (the body) expanded. For the gold nanoparticles with short thorns, most of the short thorns are single crystals and the rest are 2- or 5-fold twinned crystals. However, the long gold thorns consist mainly of 2-fold twinned crystals and a few 5-fold twinned crystals. The 3D thorny gold nanoparticles exhibit a broad absorption peak at 600-1100 nm in the visible and near-infrared range, and their spectral properties can be tuned by altering their shapes. These 3D thorny gold nanoparticles have great potential for the applications in chemical imaging and biomedical sciences.