Influence of Colloidal Au on the Growth of ZnO Nanostructures

Abstract

Vapor-liquid-solid processes allow growing high-quality nanowires from a catalyst. An alternative to the conventional use of catalyst thin films, colloidal nanoparticles offer advantages not only in terms of cost, but also in terms of controlling the location, size, density, and morphology of the grown nanowires. In this work, we report on the influence of different parameters of a colloidal Au nanoparticle suspension on the catalyst-assisted growth of ZnO nanostructures by a vapor-transport method. Modifying colloid parameters such as solvent and concentration, and growth parameters such as temperature, pressure, and Ar gas flow, ZnO nanowires, nanosheets, nanotubes and branched-nanowires can be grown over silica on silicon and alumina substrates. High-resolution transmission electron microscopy reveals the high-crystal quality of the ZnO nanostructures obtained. The photoluminescence results show a predominant emission in the ultraviolet range corresponding to the exciton peak, and a very broad emission band in the visible range related to different defect recombination processes. The growth parameters and mechanisms that control the shape of the ZnO nanostructures are here analyzed and discussed. The ZnO-branched nanowires were grown spontaneously through catalyst migration. Furthermore, the substrate is shown to play a significant role in determining the diameters of the ZnO nanowires by affecting the surface mobility of the metal nanoparticles.

ZnO-Loaded Graphene for NO2 Gas Sensing

“…Additionally, the G-ba position reveals information about the thickness of the layer [32]; specifically, thicker l ers tend to shift the G-band to lower energies. Thereby, Figure 2a,b show the peak around 1580 cm− 1 , revealing that a thin graphene layer was achieved [33]. In addition, intensity of the G-and D-band peaks confirms the good crystallinity of both studied g phene materials.…”

“…In Figure 4, one can observe the TEM images obtained for this nanocomposite. A spherically shaped dark black nanoparticle on a sheet of graphene can be clearly seen in Figure 4a, which corresponds to a ZnO nanoparticle at a magnification of 500 K. Figure 4b also exhibits a typical morphology similar to graphene-based materials with a clear vision of the numerous ZnO NPs (dark black spherical nanoparticles) decorated on the graphene sheets at a magnification of 80 K. The quantity and type of defects in ZnO can be estimated based on PL measurements [33]. Figure 5 shows the PL results for the ZnO-loaded graphene G95/5 sample.…”

“…In Figure 4, one can observe the TEM images obtained for this nanocomposite. A spherically shaped dark black nanoparticle on a sheet of graphene can be clearly seen in Figure 4a, which corresponds to a ZnO nanoparticle at a magnification of 500 K. The quantity and type of defects in ZnO can be estimated based on PL measurements [33]. Figure 5 shows the PL results for the ZnO-loaded graphene G95/5 sample.…”

“…A near band edge (NBE) emission in the UV at around 390 nm is associated with exciton recombination processes [34], and a broader deep level (DL) defect emission band in the visible range from 480 to 630 nm [35]. The DL broad emission band showed the maximum emission intensity The quantity and type of defects in ZnO can be estimated based on PL measurements [33]. Figure 5 shows the PL results for the ZnO-loaded graphene G95/5 sample.…”

ZnO-based nanomaterials approach for photocatalytic and sensing applications: recent progress and trends

“…4 In addition, much effort has been put into fabricating low-dimensional nanostructures such as nanocrystals, nanorods, nanotubes, and nanowires, among others, due to the advantages offered by their large surface-to-volume ratio. 1 The great variety of nanostructures (0D to 3D) that can be produced with this material system strongly motivates its integration into different modern devices. Recently, several nanostructure subtypes have been demonstrated to be suitable candidates for their implementation into nanodevices.…”