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Synthesis of Atomically Thin WO 3 Sheets from Hydrated Tungsten Trioxide. -Nanosheets of atomically thin WO3 layers are prepared by mechanical exfoliation of WO3·2H2O (obtained from pieces of tungsten foil in HNO3 at 80°C for 6 h) using a piece of an adhesive tape, followed by annealing at 300°C. The samples are characterized by XRD, SEM, TEM, and AFM. The sheets have thicknesses that are multiples of the unit cell height (about 1.4 nm). Raman spectroscopy demonstrates that thinning of WO3 significantly affects physical and chemical behavior. Li intercalation causes significant changes in the Raman spectra for thin samples. The prepared sheets may have great potential in developing two-dimensional electronic and photonic devices such as planar photodiodes and transistors. -(KALANTAR-ZADEH*, K.; VIJAYARAGHAVAN, A.; HAM, M.-H.; ZHENG, H.; BREEDON, M.; STRANO, M. S.; Chem.

Anodization at elevated temperatures in nitric acid has been used for the production of highly porous and thick tungsten trioxide nanostructured films for photosensitive device applications. The anodization process resulted in platelet crystals with thicknesses of 20-60 nm and lengths of 100-1000 nm. Maximum thicknesses of approximately 2.4 microm were obtained after 4 h of anodization at 20 V. X-ray diffraction analysis revealed that the as-prepared anodized samples contain predominantly hydrated tungstite phases depending on voltage, while films annealed at 400 degrees C for 4 h are predominantly orthorhombic WO3 phase. Photocurrent measurements revealed that the current density of the 2.4 microm nanostructured anodized film was 6 times larger than the nonanodized films. Dye-sensitized solar cells developed using these films produced 0.33 V and 0.65 mA/cm2 in open- and short-circuit conditions.

Among the available metal oxide nanostructures, tungsten oxide has remained, at times, troublesome to fabricate, with many synthetic methods often requiring exotic equipment and or reagents. In this work, we present a systematic investigation demonstrating a new method for the deposition of anhydrous and hydrated nanostructured tungsten oxide thin films via spin coating. The attributes of these materials include the following: high surface area, controllable deposition, and compatibility with existing semiconductor fabrication infrastructure making this method a suitable candidate for application in the manufacture of gas sensors and dye sensitized solar cells. We will show that it is possible to form micrometer thick highly crystalline nanostructured thin films and, using Raman, SEM, XRD, XPS, and TEM analysis, will prove that these nanostructures can be rendered into anhydrous or partially or fully hydrated tungsten oxides. We further demonstrate the application of these materials in the fabrication of an inexpensive NO2 gas sensor, capable of sensing sub-ppm levels of NO2 concentrations at a modest operating temperature of 175 °C.

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This paper reports the electrowetting properties of ZnO nanorods. These nanorods were grown on indium tin oxide (ITO) substrates using different liquid-phase deposition techniques and hydrophobized with sputtered Teflon. The surfaces display superhydrophobic properties. When the applied voltages are less than 35 V, the contact angle change is small and exhibits instant reversibility. For higher voltages, larger contact angle changes were observed. However, the surface was not reversible after removing the applied voltage and required mechanical agitation to return to its initial superhydrophobic state.

Progressive restrictions on the use of toxic chromate-based corrosion inhibitors present serious technical challenges.

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