Ag Nanoparticle Embedded TiO₂ Composite Nanorod Arrays Fabricated by Oblique Angle Deposition: Toward Plasmonic Photocatalysis

Abstract

Using a unique oblique angle co-deposition technique, well-aligned arrays of Ag nanoparticle embedded TiO2 composite nanorods have been fabricated with different concentrations of Ag. The structural, optical, and photocatalytic properties of the composite nanostructures are investigated using a variety of experimental techniques and compared with those of pure TiO2 nanorods fabricated similarly. Ag nanoparticles are formed in the composite nanorods, which increase the visible light absorbance due to localized surface plasmon resonance. The Ag concentrations and the annealing conditions are found to affect the size and the density of Ag nanoparticles and their optical properties. The Ag nanoparticle embedded TiO2 nanostructures exhibit enhanced photocatalytic activity compared to pure TiO2 under visible- or UV-light illumination. Ag plays different roles in assisting the photocatalysis with different light sources. Ag can be excited and can inject electrons to TiO2, working as an electron donor under visible light. While under UV illumination, Ag acts as an electron acceptor to trap the photogenerated electrons in TiO2. Due to the opposite electron transfer direction under UV and visible light, the presence of Ag may not result in a greater enhancement in the photocatalytic performance.

Graphene oxide and Ag engulfed TiO2 nanotube arrays for enhanced electron mobility and visible-light-driven photocatalytic performance

“…In most cases, GO sheets were used as an electron sink to facilitate photogenerated electrons separation and store the separated electrons. [59][60][61][62][63][64] Herein, the electrons generated by the LSPR effect in Ag NPs diffuse into the CB of TNTs. 9a shows that GO can accumulate the electrons injected from the photogenerated MB because of the p-conjugated network and higher work function of GO than that of the excited MB.…”

“…The involvement of some functional groups on the surface of GO in the adsorption of MB is shown in Fig. [59][60][61][62][63][64] The electrons react with O 2 to produce superoxide radical anion cO 2 À . † In contrast, GO-Ag-TNTs showed a greater stability in the reuse study of 2-CP with a total loss of 19.5% as the physically adsorbed 2-CP can be eluted and more active sites in GO are available for the degradation or charge transfer.…”

Nanocolumnar growth of thin films deposited at oblique angles: Beyond the tangent rule

“…[1][2][3] This anisotropy combined with their high open porosity [4][5][6][7] are essential for other applications such as Bragg reflectors with tunable optical response, 8 templates for nanocomposite films, [9][10][11][12] broad band antireflection coatings, 13,14 optical microresonators, 15 light emitting diodes, 16 photovoltaic cells, 17 advanced plasmon photocatalysis, 18,19 microfluidic sensors, 20 transparent conductive electrodes 21 and many others. In this technique, a given material is sublimated in a vacuum reactor, either thermally or assisted by an electron beam, yielding vapor species that follow straight trajectories in a "line of sight" configuration with respect to the substrate, and giving rise to thin films with well-defined tilted nanocolumnar structures.…”

Preparation of M@BiFeO3 Nanocomposites (M = Ag, Au) Bowl Arrays with Enhanced Visible Light Photocatalytic Activity

“…[3][4][5][6] However, because of the large band gap (3.2 eV) and the fast recombination rate of the photogenerated electron-hole pairs, the photocatalytic efficiency of TiO 2 is greatly limited. Although many efforts have been devoted to enhance the photocatalytic efficiency of TiO 2 by modifying TiO 2 with metals, 7,8 nonmetals, 9,10 the visible light utilization rate is still very low. To efficiently take advantage of solar energy to drive photocatalytic reaction, it is very necessary to develop efficient visible-light photocatalysts for the photodegradation of organic pollutants.…”