Here, we demonstrate for the first time a strategy to self-assemble ZnO nanoparticles (NP) on a large area by a facile one-step process. First, rough and random ZnO nanocrystals (NC), were produced by free-stabilizing aqueous synthesis. Therefore, a post thermal treatment at various temperatures ranging from 80 to 800 °C was necessary to obtain size-tunable and photoluminescent crystalline NP. The fabricated NP had both efficient UV photoluminescence and photocatalytic activity by photo-degradation of Methylene Blue (MB) dye. The annealed NP showed an absorption blue shift in the UV region with decreasing size. This shift was attributed to high quantum confinement effect since ZnO NP diameter reached values lower than the Bohr radius of ZnO (~2.7 nm). The photocatalytic activity displayed dependency on the particle’s size, number, and crystallinity. Subsequently, the NP were self-assembled inside poly(methyl methacrylate) (PMMA) nanoholes. Subsequently, large area substrate of homogenous properties ZnO NP was obtained. Moreover, the synthesis facility, photoemission and photocatalytic properties of ZnO NP could be a new insight into the realization of high performance and low cost UV laser devices.
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).
Surface-enhanced Raman scattering (SERS) substrates consisting of stacked ultrathin nanoporous gold layers are used to detect very low concentrations of molecules in liquids or gases. The SERS substrates are obtained by copper chemical etching of alternative copper and gold stacked nanolayers. This process is a reliable method for fabricating uniform and reproducible SERS substrates, with a robust SERS response at extremely low detection limits. By optimizing fabrication conditions combined with a thorough analysis of the SERS mappings and using 2,2-bipyridine (BP) as probe molecules, the detection threshold corresponding to a detectable SERS response reaches a BP concentration of 10–18 mol·L–1 in water. An additional Raman mechanism is also highlighted by μ-surface enhancement spatially offset Raman spectroscopy (μ-SESORS): gold ligaments, inside nanoporous layers, act as waveguides for the incident light, leading to a significant increase in the size of the active SERS area. Moreover, these SERS substrates could be stored for several days without a significant decrease in their properties, and they can be reactivated and reused after SERS analysis. The ability to detect low BP vapor pressure is also demonstrated.
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