A simple molten salt method to synthesize single-crystalline potassium titanate nanobelts
Introduction
One-dimensional (1D) nanostructures, such as nanorods, nanowires, nanotubes, and nanobelts, have attracted extraordinary interests because of their fascinating size-dependent optical, electronic, magnetic, thermal, mechanical, and chemical properties and their potential applications in nanodevices [1], [2]. Among a large amount of nanomaterials, TiO2-related nanowires or nanotubes are particularly interesting, partly because they have large specific surfaces and may enhance the photocatalytic activity, leading to a higher potential applications in environmental purification, degradation of toxic substances and decomposition of pure water and for oxygen electrodes in potentiometric sensors for O2 and CO2 [3], [4], [5], [6].
Potassium titanates with the formula K2TinO2n + 1 consisting of titanium oxide layers and interlayer cations have unique layered and tunnel crystal structure, which shows excellent ion-exchange and intercalation ability besides their high photocatalytic activity. Many methods have been developed to synthesize 1D Potassium titanates nanostructures [7], [8], [9], [10], [11]. Among the various alkali metal titanates, K2Ti4O9 and K2Ti6O13 are of great interest for their possible applications such as whisker-reinforced plastics and metals [12], [13]. In most cases, K2Ti6O13 nanowires are fabricated by the time-consuming hydrothermal method [14], [15], [16]. Xu et al. have reported the discovery of K2Ti6O13 nanorings formed by self-spiraling of K2Ti6O13 nanobelts, which were prepared by molten salt synthesis (MSS) in the presence of a nonionic surfactant (NP9) [17]. Li et al. presented the formation of high quality K2Ti6O13 whiskers via MSS, followed by boiling water treatment and reheating [18]. In this letter, we propose a facile, no organic dispersant or surfactant, veriest green-chemistry route to prepare K2Ti6O13 nanobelts. At the same time, the influences of the experimental conditions on the formation of pure phase potassium titanate nanobelts are investigated.
Section snippets
Experimental details
In a typical procedure of fabricating K2Ti6O13 nanobelts, analytical-grade reagents KCl and TiO2 nonoparticles (anatase, 40–80 nm) were used as starting materials. 0.02 g TiO2 nanoparticles and 10 g KCl were mixed, ground homogeneously in a mortar for 20 min. The mixture was then placed in an alumina crucible, and annealed at 950 °C for 3 h in a crucible furnace, and subsequently naturally cooled to room temperature. Samples were collected, washed several times with distilled water to remove
Results and discussion
The crystal structures of the products was examined on a X-ray diffractometer (XRD) with Cu Ka radiation (λ = 1.54 Å). Fig. 1 shows the XRD pattern of the potassium titanate nanobelts. All of the diffraction peaks can be indexed to a pure monoclinic phase of K2Ti6O13 (JCPDS 74-0275) with a = 15.58 Å, b = 3.820 Å, c = 9.112 Å, and β = 99.764°. The XRD data show that the reaction was complete under the current synthetic conditions.
The morphology of as-synthesized potassium titanate nanobelts was
Conclusions
In summary, potassium titanate nanobelts with diameters ranging from 100 to 300 nm and lengths up to 50 μm were synthesized on a large scale with a facile and simple one-step solid-state chemical reaction. The effects of the reaction temperature, the reaction time, and the weight ratio of TiO2 to KCl on the ultimate products were discussed. This method may also be extended to the fabrication of other ternary oxide 1D nanostructure with different chemical compositions. Further work involves the
Acknowledgement
This work was supported by the National Key Project of Fundamental Research of China (No.2005CB623605).
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