Controllable hot electron transfer in the Ag/MoO layer by layer system: Thickness-dependent MoO layer.

The Ag and MoO layer-by-layer sputtering method was employed to fabricate Ag/MoO coated on a polystyrene (PS) array (Ag/MoO@PS), which exhibited excellent surface-enhanced Raman scattering (SERS) activity. The thickness of the MoO layer was controlled by changing the sputtering power. The SERS intensity of 4-aminothiophenol (PATP) on Ag/MoO@PS with a 2 nm thickness of the MoO layer was comparable to that on pure Ag coated on the PS array (Ag@PS). This is possible because hot electrons were injected from Ag into the MoO layer to enhance the photocatalyst reaction; thus, the SERS spectra of coupled PATP were obtained. The transport of hot electrons rapidly decayed and was blocked with increasing thickness of the MoO layer from 2 nm to 9 nm. Thus, the SERS intensity decreased, and interestingly, the b mode of PATP decreased and nearly disappeared. This study provides new insight into the control of hot electron reduction for catalytic reduction process monitoring.