Visualization of Photoinduced Charge Distribution of Au Nanoparticle Assembly by SPM

Introduction

Composites of metal nanoparticles and semiconductors are representative heterogeneous photocatalysts which enable a wide range of photochemical conversions. For example, composites of gold (Au) nanoparticles (AuNP) and titanium dioxide (TiO₂) have been widely researched, as they possess promising reactivity as photocatalysts. When TiO₂ absorbs incident light corresponding to its bandgap energy, the excited electrons in its conduction band of the TiO₂ are transferred to AuNP immobilized on its surface, preventing chargerecombinationintheTiO₂.Visualizationofthecharge distribution is effective for elucidating this phenomenon. Moreover, visualization is also useful in control of integrated structures which are important in the creation of novel functional bio-devices utilizing metalloproteins involved in electron transfer. Kelvin probe force microscopy (KPFM) is an analytical technique in which Kelvin’s law is applied to the scanning probe microscope (SPM), and makes it possible to measure not only the surface shape of samples, but also their surface potential distribution. Here, visualization of the photoinduced charge distribution (charge separation) on the surface of a hybrid TiO₂ material with an AuNP assembly immobilized on its surface was attempted by KPFM measurements under ultraviolet (UV) irradiation.

July 9, 2020 GMT