Enhanced photodetector performance in gold nanoparticle decorated ZnO microrods

Herein, we present a facile synthesis of ZnO microrods and surface decoration with gold nanoparticles using a low-cost deposition apparatus. The ZnO microrods were fabricated via a single-step solid-state reaction, and the gold nanoparticles were synthesized on the surface of the microrods by the deposition of gold thin films and sequential heat treatment. The size of the gold nanoparticles was controlled by varying the thickness of the gold thin films and the annealing temperature. The intensity of green emission in the photoluminescence spectra decreased with increasing gold nanoparticle size. A surface plasmon resonance peak originating from the gold nanoparticles appeared at ~570 nm in the absorption spectra, and the peak redshifted as the nanoparticle size increased. The ultraviolet (UV) on???off current ratio and response speed of single ZnO microrod photodetectors significantly increased after surface decoration by gold nanoparticles. However, the performance of the photodetector degraded as the size of the gold nanoparticles increased owing to the absorption of incident UV light. The enhanced photodetector performance of the surface-modified ZnO microrods is explained by the transfer of energetic electrons excited by surface plasmon resonance from the defect level to the conduction band of the ZnO microrods. ?? 2020 Elsevier Inc

Self-Assembly of Nanoparticle-Spiked Pillar Arrays for Plasmonic Biosensing

9 pags. 5 figs.Plasmonic biosensors have demonstrated superior performance in detecting various biomolecules with high sensitivity through simple assays. Scaled-up, reproducible chip production with a high density of hotspots in a large area has been technically challenging, limiting the commercialization and clinical translation of these biosensors. A new fabrication method for 3D plasmonic nanostructures with a high density, large volume of hotspots and therefore inherently improved detection capabilities is developed. Specifically, Au nanoparticle-spiked Au nanopillar arrays are prepared by utilizing enhanced surface diffusion of adsorbed Au atoms on a slippery Au nanopillar arrays through a simple vacuum process. This process enables the direct formation of a high density of spherical Au nanoparticles on the 1 nm-thick dielectric coated Au nanopillar arrays without high-temperature annealing, which results in multiple plasmonic coupling, and thereby large effective volume of hotspots in 3D spaces. The plasmonic nanostructures show signal enhancements over 8.3 × 10-fold for surface-enhanced Raman spectroscopy and over 2.7 × 10-fold for plasmon-enhanced fluorescence. The 3D plasmonic chip is used to detect avian influenza-associated antibodies at 100 times higher sensitivity compared with unstructured Au substrates for plasmon-enhanced fluorescence detection. Such a simple and scalable fabrication of highly sensitive 3D plasmonic nanostructures provides new opportunities to broaden plasmon-enhanced sensing applications.This work was supported by the Fundamental Research Program (PNK 6070) of the Korean Institute of Materials Science (KIMS) and the Ministry of Trade, Industry and Energy (Grant N0002310). S.A.M. acknowledges ONR Global, the EPSRSC Reactive Plasmonics Programme (EP/M013812/1), the Lee-Lucas Chair in Physics, and the Bavarian Solar Energies Go Hybrid (SolTech) programme. X.X. was supported by Lee Family Scholars. H.I. was supported in part by National Cancer Institute of the National Institutional of Health under award number R00CA201248