Synthesis of Visible Light-Sensitive ZnO Nanostructures: Subwavelength Waveguides

Abstract

Single crystalline ZnO nanowires and nanorods were synthesized by a new sol-gel method carried out through formation of liposome-ZnO nanocomposites with or without hydrothermal reaction, respectively, and they were characterized to be hexagonal wurtzite structure by measurements of XRD patterns and SEM and TEM images. The UV-visible absorption spectrum of the nanowires was observed to exhibit a very high absorption of visible light from 400 to 600 nm as compared to that of the nanorods. The photoluminescence (PL) images and spectra of the single nanowires and nanorods were measured upon excitation with a 415 nm femtosecondpulsed laser beam by a confocal scanning microscope-coupled PL spectral system, and the single nanowires were observed to exhibit waveguided red-emission at the tip whereas unguided emission only was observed by UV-excitation. Analysis of the dependence of nanowire length on the waveguide mode spacing indicated that the subwavelength waveguide is operated by the axial Fabry-Pe ˙rot-type microcavity resonance. These results demonstrated that the ZnO nanowires can exhibit the subwavelength waveguide behavior as long as the defects are excited directly with visible light, suggesting that the present ZnO nanowires will be a promising nanomaterial for future visible light-sensitive lasing cavity and optoelectronic devices.

Surface‐Plasmon‐Enhanced Band Emission of ZnO Nanoflowers Decorated with Au Nanoparticles

“…Recently, ZnO materials have attracted considerable interest as candidates for photoanodes in dye-sensitized solar cells because of their high electron mobility (115-155 cm 2 V À1 s À1 ) and simple fabrication of the nanostructures, [7][8][9] although titanium dioxide has been considered as the primary and most-promising material. [10][11] ZnO nanostructures, such as nanorods, nanowires, and nanoflowers, are considered to be suitable materials for making advanced devices, such as optical switching [12][13][14][15][16] and high-order waveguides, [17][18][19][20] owing to their large surface-to-volume ratios and the photon-confinement effect. It is well-known that ZnO exhibits one emission peak in the UV region, owing to the recombination of free excitons, and another one (or more) peaks in the visiblelight range, owing to defects such as oxygen vacancies [21] and zinc vacancies.…”

Enhanced ethanol sensing properties based on Sm2O3-doped ZnO nanocomposites

“…The band gap energy of as-prepared ZS-x is lower than that of bulk ZnO (3.37 eV), which may be related to surface defects density. 21 In addition, the results indicate that the addition of samaria does not affect ZnO band gap. This may indicate that no incorporation of Sm 3+ in ZnO lattice has occurred because Sm 3+ ions have a larger radius (0.0958 nm)…”

Single Nanoparticle Photoluminescence Studies of Visible Light-Sensitive TiO2and ZnO Nanostructures

“…This fact has been postulated to be due to a decrease in the density of defects by increased exciton migration from the band edge to lower energy-defect state with the higher UV energy excitation. 50 51 which can absorb whole visible light as approved by the diffuse reflectance absorption spectrum (Figure 10 (C). The ZnO nanowires are Wurtzite single crystalline having aspect ratio of 7.5~50 with about 400 nm in diameter and 3~20 μm in length.…”