Water-dispersible TiO2 nanoparticles via a biphasic solvothermal reaction method.

A biphasic solvothermal reaction method has been used for the synthesis of TiO2 nanoparticles (NPs). In this method, hydrolysis and nucleation occur at the interface of organic phase (titanium (IV) n-propoxide and stearic acid dissolved in toluene) and water phase (tert-butylamine dissolved in water) resulting in the nucleation of the stearic acid-capped TiO2 NPs. These NPs are hydrophilic due to hydrophobic stearic acid ligands and could be dispersed in toluene, but not in water. These stearic acid-capped TiO2 NPs were surface-modified with 2,3-dimercaptosuccinic acid (DMSA) in order to make them water soluble. The resultant TiO2 NPs were easily redispersed in water without any noticeable aggregation. The Rietveld profile fitting of X-ray diffraction (XRD) pattern of the TiO2 NPs revealed highly crystalline anatase structure. The average crystallite size of TiO2 NPs was calculated to be 6.89 nm, which agrees with TEM results. These results have important implications for the use of TiO2 in biomedical, environmental, and industrial applications.

Self-induced gate dielectric for graphene field-effect transistor.

We report the electronic characteristics of an avant-garde graphene-field-effect transistor (G-FETs) based on ZnO microwire as top-gate electrode with self-induced dielectric layer. Surface-adsorbed oxygen is wrapped up the ZnO microwire to provide high electrostatic gate-channel capacitance. This nonconventional device structure yields an on-current of 175 µA, on/off current ratio of 55, and a device mobility exceeding 1630 cm(2)/(V s) for holes and 1240 cm(2)/(V s) for electrons at room temperature. Self-induced gate dielectric process prevents G-FETs from impurity doping and defect formation in graphene lattice and facilitates the lithographic process. Performance degradation of G-FETs can be overcome by this avant-garde device structure.

ZnO piezoelectric fine wire gated graphene oxide field effect transistor.

Here we report the fabrication and characteristics of graphene oxide (GO) field effect transistor gated with piezopotential of ZnO fine wires on a flexible substrate. The FET device consists of GO thin film on the bottom and ZnO piezoelectric fine wire (PFW) on the top. In the FET device the GO serves as a carrier transport channel and ZnO PFW acts as a gate. When the substrate is bent, a piezopotential is generated in the ZnO PFW. The piezopotential created by the strain in the ZnO PFW was used to control the carrier transport in the GO channel. This device demonstrates the application of piezoelectric ZnO PFW for creating the gating effect on the semiconducting performance of GO film.

Application of aligned ZnO nanowires/nanobelts as a room temperature NO gas sensor.

Gas sensing properties of devices fabricated using ZnO nanowires/nanobelts (NS) aligned between two electrodes using dielectrophoresis technique were investigated. ZnO nanostructures were synthesized by carbothermal method. The devices were characterized as gas sensors and showed high sensitivity for detection of NO gas at room temperature. Typical sensor response, defined as the relative change in resistance, due to the introduction of the gas was found to be approximately 500% for 40 ppm of NO gas. The devices showed average response and recovery times of about 30 s and 1 min respectively. The results demonstrate the potential of fabricating nanosized sensors using single nanowires/nanobelts.