Tailoring Nanoparticle Morphology to Match Application: Growth under Low-Intensity Polychromatic Light Irradiation Governs the Morphology and Optical Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) are incredibly versatile nanostructures that present a broad spectrum of applications, from nanomedicine to advanced optoelectronic materials. All AgNP properties strongly depend on nanoparticle size and shape. However, controlling these parameters in a cost-effective way is still a challenge. In this scenario, this study presents a modification of a classical two-step seed-mediated synthesis for photoinduced control of the morphology and optical properties of AgNP under low-intensity light-emitting diode (LED) irradiation in the presence of citrate as the sole additive. The LED irradiation wavelength determines the final morphology of these particles because of the shape dependence of the AgNP plasmon spectrum. Kinetics of photochemical transformation were monitored by electronic absorption, transmission electron microscopy, and X-ray diffraction studies. Data fitting revealed that particle growth follows an unusual two-step photoinduced mechanism that includes (i) a photoinduced fusion of AgNP and (ii) a light-driven autocatalytic anisotropic growth along a favorable silver crystal axis following the Finke–Watzky kinetic model. The proposed mechanism highlights the importance of interweaving both crystallographic and surface chemistry arguments in order to discern the overall mechanism of nanoparticle growth. Therefore, the presented methodology allows obtaining very complex metallic nanostructures using a simple and low-cost methodology aiming the development of size-controllable nanoparticles for optical and (photo)catalytic applications.