Application of microwave superheating for the synthesis of TiO2 rods

Sn4+ doping induced novel morphological evolution in zinc titanate heteronanostructures and studies on their optical properties

Novel morphological evolution has been demonstrated in Sn⁴⁺ doped zinc titanate heteronanostructures synthesized via an ethylene glycol mediated route.

Influence of calcination temperatures on the formation of anatase TiO2nano rods with a polyol-mediated solvothermal method

A simple and convenient method has been demonstrated for large-scale synthesis of anatase titanium dioxide (TiO₂) nanorods.

One pot microwave-assisted synthesis of Ag decorated yolk@shell structured TiO2 microspheres

A facile and extremely fast one-pot microwave-assisted synthesis of Ag decorated yolk@shell structured TiO₂ microspheres was reported.

Review of the progress in preparing nano TiO2: an important environmental engineering material

TiO2 nanomaterial is promising with its high potential and outstanding performance in photocatalytic environmental applications, such as CO2 conversion, water treatment, and air quality control. For many of these applications, the particle size, crystal structure and phase, porosity, and surface area influence the activity of TiO2 dramatically. TiO2 nanomaterials with special structures and morphologies, such as nanospheres, nanowires, nanotubes, nanorods, and nanoflowers are thus synthesized due to their desired characteristics. With an emphasis on the different morphologies of TiO2 and the influence factors in the synthesis, this review summarizes fourteen TiO2 preparation methods, such as the sol-gel method, solvothermal method, and reverse micelle method. The TiO2 formation mechanisms, the advantages and disadvantages of the preparation methods, and the photocatalytic environmental application examples are proposed as well.

DNA mediated wire-like clusters of self-assembled TiO₂ nanomaterials: supercapacitor and dye sensitized solar cell applications

A new route for the formation of wire-like clusters of TiO₂ nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO₂ nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO₂ NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 ± 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO₂ nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO₂ nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g(-1) was observed for TiO₂ having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO₂ nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO₂ nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water.

Microwave-assisted fabrication of nanoparticulate TiO(2) microspheres for synergistic photocatalytic removal of Cr(VI) and methyl orange

High yield production of micro/nanostructured nanoparticulate TiO2 microspheres (NTMs) via a facile microwave-assisted hydrothermal approach was investigated. The rapid and uniform microwave heating could reduce the reaction time to 30 min, an order of magnitude shorter than that of conventional hydrothermal methods. The characterization data confirmed that the resultant NTMs were highly uniform in size, having an average diameter of ∼0.5 μm. The obtained NTMs were found to be constructed by well-crystallized anatase phase nanoparticles ranging from 5 to 10 nm that can be readily controlled by the microwave radiation temperature. Nitrogen sorption isotherm analysis revealed that the obtained NTMs possessed abundant mesoporous structures with a high specific surface area of 124 m(2) g(-1). An in situ self-aggregation formation process under controllable pH in presence of urea was proposed. The results obtained from the application of NTMs for simultaneous photocatalytic decontamination of Cr(VI) and methyl orange (MO) demonstrated a strong synergistic effect that dramatically enhanced both Cr(VI) reduction and MO oxidation removal efficiencies. This work not only enriched the synthesis methods of the micro/nanostructured TiO2, but also provided a new means to improve the photocatalytic efficiency via structural-induced synergistic effect, applicable to the other catalysis systems.

Application of graphene oxide as a hydrothermal catalyst support for synthesis of TiO2 whiskers

How graphene oxide (GO) with its step edges and wrinkles (∼1–2 nm) acts as a catalyst in hydrothermal nucleation and growth is demonstrated.

Microwave-assisted synthesis of colloidal inorganic nanocrystals

Colloidal inorganic nanocrystals stand out as an important class of advanced nanomaterials owing to the flexibility with which their physical-chemical properties can be controlled through size, shape, and compositional engineering in the synthesis stage and the versatility with which they can be implemented into technological applications in fields as diverse as optoelectronics, energy conversion/production, catalysis, and biomedicine. The use of microwave irradiation as a non-classical energy source has become increasingly popular in the preparation of nanocrystals (which generally involves complex and time-consuming processing of molecular precursors in the presence of solvents, ligands and/or surfactants at elevated temperatures). Similar to its now widespread use in organic chemistry, the efficiency of "microwave flash heating" in dramatically reducing overall processing times is one of the main advantages associated with this technique. This Review illustrates microwave-assisted methods that have been developed to synthesize colloidal inorganic nanocrystals and critically evaluates the specific roles that microwave irradiation may play in the formation of these nanomaterials.

Dry autoclaving for the nanofabrication of sulfides, selenides, borides, phosphides, nitrides, carbides, and oxides

This review compiles various nanostructures fabricated by a distinct "dry autoclaving" approach, where the chemical reactions are carried out without solvents; above the dissociation temperature of the chemical precursor(s) at elevated temperature in a closed reactor. The diversity to fabricate carbides (SiC, Mo(2) C, WC), oxides (VOx-C, ZnO, Eu(2) O(3) , Fe(3) O(4) , MoO(2) ), hexaborides (LaB(6) , CeB(6) , NdB(6) , SmB(6) , EuB(6) , GdB(6) ), nitrides (TiN, NbN, TaN), phosphides (PtP(2) , WP), sulfides (ZnS, FeS/C, SnS/C, WS(2) , WS(2) /C), and selenides (Zn(1-x) Mn(x) Se/C, Cd(1-x) Mn(x) Se/C), with various shapes and sizes is accounted with plausible applications. This unique single-step, solvent-free synthetic process opens up a new route in the growing nanomaterials science; owing to its considerable advantages on the existing approaches.

Investigation of the formation of CuInS2 nanoparticles by the oleylamine route: comparison of microwave-assisted and conventional syntheses

The formation of copper indium disulfide nanoparticles via the oleylamine route using copper iodide, indium chloride, and elemental sulfur has been investigated by applying conventional thermal heating as well as microwave irradiation. Oleylamine thereby acts as a capping ligand as well as a solvent. In an initial set of experiments, the onset of the reaction was determined to be around 115 °C by an in situ X-ray study using Synchrotron radiation. Using comparatively low synthesis temperatures of 120 °C, it is already possible to obtain nanoparticles of 2-4 nm with both heating methods but with irregular shape and size distribution. By applying higher temperatures of 220 °C, more crystalline and larger nanoparticles were obtained with slight differences in crystallite size and size distribution depending on the synthesis route. The size of the nanoparticles is in the range of 3-10 nm depending on the heating time. Using microwave irradiation, it is possible to obtain nanoparticles in only 90 s of total synthesis time. Control experiments to probe a nonthermal microwave effect were carried out ensuring an identical experimental setup, including the heating profile, the stirring rate, and the volume and concentration of the solutions. These experiments clearly demonstrate that for the preparation of CuInS(2) nanoparticles described herein no differences between conventional and microwave heating could be observed when performed at the same temperature. The nanoparticles obtained by microwave and thermal methods have the same crystal phase, primary crystallite size, shape, and size distribution. In addition, they show no significant differences concerning their optical properties.

Preparation of silver-modified TiO2 via microwave-assisted method and its photocatalytic activity for toluene degradation

Silver-modified TiO(2) (Ag-TiO(2)) with various Ag/Ti molar ratios were prepared by the microwave-assisted method and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS). Compared with the hydrothermal method, Ag-TiO(2) of small crystallite size and high crystallinity can be obtained by the microwave-assisted preparation method. When the Ag/Ti molar ratio increased from 0 to 2%, the doping of Ag promoted the phase transformation and inhibited the growth of anatase crystallite. The absorption edge of Ag-TiO(2) shifted to longer wavelength, and the band gap energy of Ag-TiO(2) decreased. However, after increasing the molar ratio Ag/Ti further from 2 to 4%, the anatase content, the crystallite size and the band gap energy of Ag-TiO(2) only increased slightly. In photodegradation gaseous toluene, the photocatalytic activity of Ag-TiO(2) increased with the increase of Ag/Ti molar ratio from 0 to 1%, but declined with the further increase to 2%. The optimal Ag/Ti molar ratio for photocatalytic activity of Ag-TiO(2) was found as 1%, with the content of anatase, rutile and brookite of 71.1, 14.5 and 14.4%, respectively. Compared with TiO(2), Ag-TiO(2) exhibited a better photostability in toluene degradation.