Plasmon‐Enhanced Photoluminescence and Photocatalysis Reactions in Metal‐Semiconductor Nanomaterials: UV‐Generated Hot Electron in Gold‐Zinc Oxide

Abstract

Herein, we introduce a mechanistic study to design a hybrid junction in metallic‐semiconductor (M/SC) nanostructures. UV‐light‐induced hot electron generation in ZnO nanostructures is used to precisely tune the photoluminescence (PL) and photocatalytic (PC) properties in hybrid Au/ZnO nanomaterials. Both enhancement and quenching of the PL and PC functionalities are observed, depending on the properties of the Au nanoparticles (AuNPs) and the Au/ZnO molecular distance. Under UV irradiation free‐ligand AuNPs quench the luminescence of ZnONPs through direct charge transfer (CT) from ZnO to the AuNPs. In contrast, capped AuNPs enhance the ZnO emission through indirect CT from AuNPs to ZnONPs facilitated by the distance created by the CTAB ligand between both constituents of the hybrid systems. It is necessary to optimise the Au/ZnO molecular distance to achieve an enhancement of both the plasmonic photocatalysis reaction and photoelectric properties of M/SC nanostructures. This phenomena is mediated by the energy transfer (ET) from ZnONPs to AuNPs. The resulting PL enhancement is described by the plasmon‐induced resonance energy transfer effect (PIRET effect).

Plasmon-Enhanced Photocatalysis Based on Plasmonic Nanoparticles for Energy and Environmental Solutions: A Review

“…Akil et al designed and optimized a nanostructure consisting of metal/semiconductor, i.e., Au–ZnO in order to enhance both photocatalytic and photoluminescence properties of the hybrid material under visible light irradiation (Figure c). It was shown that by using CTAB as a shell of AuNPs and spacer between two components, the photoluminescence characteristic of ZnO as a result of the SPR effect of AuNPs was enhanced.…”

“…To conclude, these perfect results came from improved photocatalytic activities originating from the plasmon-enhanced photoabsorption and rapid separation of photogenerated electron−hole pairs in the heterostructure as shown in Figure 3b. Akil et al 37 designed and optimized a nanostructure consisting of metal/semiconductor, i.e., Au−ZnO in order to enhance both photocatalytic and photoluminescence properties of the hybrid material under visible light irradiation (Figure 3c). It was shown that by using CTAB as a shell of AuNPs and spacer between two components, the photoluminescence characteristic of ZnO as a result of the SPR effect of AuNPs was enhanced.…”

“…Copyright 2018 Elsevier. (c) The proposed mechanism for the plasmon-enhanced photocatalysis of the Au/ZnO nanohybrids, reproduced with permission from ref . Copyright 2020 Wiley.…”

Localized Energy Band Bending in ZnO Nanorods Decorated with Au Nanoparticles

“…The surface decoration of semiconductor nanostructures with metallic nanoparticles (NPs) usually leads to an improvement of their catalytic and electrical properties [ 10 , 11 , 12 , 13 , 14 ]. The formation of nano-Schottky junctions at the metal–semiconductor interface leads to the creation of a strong electric field directed toward the surface and to a significant modification of the ZnO NRs energy band profiles [ 15 , 16 , 17 , 18 , 19 ]. As a consequence, space charge regions and surface-localized electric fields promote a catalytic effect and modify the radiative recombination process.…”

“…Such a process could be the consequence of a significant bending of electronic energy bands into ZnO just below the metal nanoparticle, inducing free carrier depletion. Such an effect in decorated ZnO nanorods allows the application of these composite materials in UV sensing and light-induced catalysis [ 11 , 16 , 18 , 19 , 30 , 31 ].…”