Optimizing the shape anisotropy of gold nanoparticles for enhanced light harvesting and photocatalytic applications

Hybrid nanoparticles (NP) of bismutite nanodisks (BSC ND) with gold nanoparticles (Au NP) of different aspect ratios (AR), such as spheres, rods and etched rods were synthesized via a facile sonochemical method. To better control the shapes of Au NP deposited on the substrate, these were pre-synthesized prior to the deposition using a modified seed mediated growth method by altering the pH and supersaturation of the growth solution. The shift in the peak position and shape of the localized surface plasmon resonance (LSPR) absorption band associated with fine-tuning of the shape of Au NP, led to enhanced light harvesting capabilities of the hybrid. Introducing shape anisotropy in the NP brought about narrowing of bandgap and lowering of PL intensity in the hybrids, suggesting better electronic contact of the NP with BSC, and effective suppression of recombination effects. Hybrids of BSC with Au nanorods showed 14% improved degradation of methylene blue (MB) dye compared to the hybrids with nanospheres. With this study, we provide a novel promising strategy to maximize the light harvesting capacity of semiconductors by tailoring the AR of Au NP, for improved solar to chemical energy conversion.