Mesoporous titanium dioxide nanobelts: Synthesis, morphology evolution, and photocatalytic properties
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Xin Wanga) Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100, People’s Republic of China (Received 10 January 2012; accepted 25 April 2012)
Mesoporous titanium dioxide (TiO2) and lithium (Li)-doped TiO2 nanobelts were synthesized via a facile solvothermal process. The crystalline structure and morphology of the nanobelts were characterized in detail. The x-ray diffraction patterns, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images indicate that the nanobelts have uniform monoclinic geometry with a length of 3–4 lm and a width of 40–200 nm, the pores are also uniform with 5–7 nm in diameter. scanning electron microscopy and TEM studies demonstrate the as-prepared TiO2 nanobelts have varied morphologies that strongly depend on the volume ratio of the reaction medium and the pressure. Ultraviolet-visible diffuse reflectance spectroscopy was used to study the photocatalytic degradation of Malachite green over the lithium nanoparticle-loaded mesoporous TiO2 nanobelts. The doping of lithium does not change the crystalline phase but the results form infrared spectrums confirm that the Li1 ion incorporates into the lattice of TiO2 nanobelts, decomposes it by replacing Ti41 and thus reduces the photocatalytic activity.
I. INTRODUCTION
One-dimensional (1D) titanium dioxide (TiO2) nanostructures have received a great deal of research interest in recent years because of their promising applications in many fields such as solar cells, biomaterials, optical devices, sensors and photocatalysts.1–8 Much research has demonstrated that 1D nanowires or nanobelts have advantages over commonly used nanospheres or nanoparticles: in the first place, visible light scattering and absorption are highly enhanced in nanowires duo to their high length-to-diameter ratio9; second, the 1D geometry facilitates rapid, diffusionfree electron transport along the longest direction10–13; moreover, the high degree of crystallinity of the nanowires/ nanobelts and the low number of grain boundaries may exhibit lower recombination rates.14,15 Therefore, numerous approaches have been developed to prepare TiO2 nanowires/nanobelts with high surface-to-volume ratio that can offer more active sites. Metal-doped TiO2 nanobelts are expected to have effective visible light response, high surface-to- volume ratio and fast charge transfer, and thereby high visible photocatalytic activity. Recently, Wang et al.7 reported that silver nanoparticles-loaded TiO2 nanobelts were prepared via hydrothermal processing and subsequent heat treatment, and
found that silver (Ag) particles could be absorbed onto nanobelts in high density to produce stable Ag/TiO2 nanobelt composites, which hold application potentials in photocatalysis and photoelectronics. Anatase TiO2 nanobelts doped with rare earth ions of ytterbium or erbium, Yb31, Er31 or Yb31/Er31 by Ji et al.6 show strong visible up-conversion fluorescence under 980 nm excitation. However, Li1/TiO2 photocatalysts16,17 prepared by the same sol-gel technique ind
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