Investigation of shape effect of silver nanostructures and governing physical mechanisms on photo-activity: Zinc oxide/silver plasmonic photocatalyst

Plasmonic composites consisting of silver nanostructures and zinc oxide semiconductor have better photocatalytic performance than pure zinc oxide. To prepare the composites, nanostructures of zinc oxide particles, gold spheres, and three different silver morphology including cubes, spheres, and wires were synthesized. A detailed study of the main mechanisms governing the activity of plasmonic photocatalysts showed that the improvement of photocatalytic performance is attributed to localized surface plasmon resonance-mediated energy transfer from silver to zinc oxide. This mechanism, which is performed using non-radiative (near-field) and radiation (far-field) processes, led to an increase in the concentration of e^?/h⁺ pairs near the semiconductor. We also showed that the increase of the photocatalytic activity depends on the shape of the silver nanostructures in the composites. Our theoretical and experimental studies have shown that composites containing silver cubes have the highest increase of photocatalytic activity compared to other morphologies. The percentage of photocatalytic degradation of methylene blue solution in presence of silver cubes was about 15% higher than that of other morphologies. Therefore, by controlling the shape of noble metal nanostructures, the photocatalytic activity of a semiconductor can be maximized and adjusted.