Rapid sol-gel synthesis of honeycomb-layered Na3Ni2BiO6 and orthorhombic Na3Ca2BiO6

The A₃M₂M'O₆ type materials Na₃Ca₂BiO₆ and Na₃Ni₂BiO₆ were successfully synthesised through two sol-gel techniques - a method based on a natural deep eutectic solvent, and a biopolymer-mediated synthesis. The materials were analysed using Scanning Electron Microscopy to determine if there was a difference in final morphology between the two methods, and it was found that the natural deep eutectic solvent method resulted in a more porous morphology. For both materials, the optimum dwell temperature was found to be 800 °C, which in the case of Na₃Ca₂BiO₆ was a much less energy-intensive synthesis process than its seminal solid-state synthesis. Magnetic susceptibility measurements were undertaken on both materials. It was found that Na₃Ca₂BiO₆ exhibits only weak, temperature independent paramagnetism. Na₃Ni₂BiO₆ was found to be antiferromagnetic, with a Néel temperature of 12 K, in line with previously reported results.

Highly efficient catalytic/sonocatalytic reduction of 4-nitrophenol and antibacterial activity through a bifunctional Ag/ZnO nanohybrid material prepared via a sodium alginate method

In this work, a bifunctional nanohybrid silver/zinc oxide material (Ag/ZnO) has been synthesized by a rapid route using sodium alginate simultaneously as a sacrificial template and silver reducing agent. The obtained samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid diffuse reflectance and liquid state UV-visible spectroscopy (DRS, UV-visible), and nitrogen adsorption-desorption analysis (BET-BJH). The XRD patterns showed that the Ag/ZnO sample is composed of a hexagonal zinc oxide structure with cubic metallic silver (Ag°). SEM micrographs exhibited a porous structure which was confirmed by BET-BJH methods to be mesoporous. The Ag/ZnO material was used as a nanocatalyst in the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as well as an antibacterial agent against Escherichia coli and Staphylococcus aureus. It was found that an efficient 4-NP reduction to 4-AP in the presence of NaBH₄ shows a rate constant of 0.418 min^-1 under ultrasonic energy and 0.316 min^-1 without ultrasonic energy. Both the catalysis reaction and antibacterial activity analysis were conducted in water solution and showed a synergetic effect of metallic silver loading.

A TiO2/C catalyst having biomimetic channels and extremely low Pt loading for formaldehyde oxidation

This study presents a TiO₂/C hybrid material with biomimetic channels fabricated using a wood template. Repeated impregnations of pretreated wood chips in a Ti precursor were conducted, followed by calcination at 400–600 °C for 4 hours under a nitrogen atmosphere. The generated TiO₂ nanocrystals were homogenously distributed inside a porous carbon framework. With an extremely low Pt catalyst loading (0.04–0.1 wt%), the obtained porous catalyst could effectively oxidize formaldehyde to CO₂ and H₂O even under room temperature (conv. ∼100%). Wood acted as both a structural template and reduction agent for Pt catalyst generation in sintering. Therefore, no post H₂ reduction treatment for catalyst activation was required. The hierarchal channel structures, including 2–10 nm mesopores and 20 μm diameter channels, could be controlled by calcination temperature and atmosphere, which was confirmed by SEM and BET characterizations. Based on the abundant availability of wood templates and reduced cost for low Pt loading, this preparation method shows great potential for large-scale applications.

This study presents a TiO₂/C hybrid material with biomimetic channels fabricated using a wood template.

New synthesis of a Foamlike Fe3O4/C composite via a self-expanding process and its electrochemical performance as anode material for lithium-ion batteries

A novel foamlike Fe3O4/C composite is prepared via a sol-gel type method with gelatin as the carbon source and ferric nitrate as the iron source, following a postannealing treatment. Its lithium storage properties as anode material for a lithium-ion battery are thoroughly investigated in this work. With the interaction between ferric nitrate and gelatin, the foamlike architecture is attained through a unique self-expanding process. The Fe3O4/C composite possesses abundant porous structure along with highly dispersed Fe3O4 nanocrystal embedment in the carbon matrix. In the constructed architecture, the 3D porous network property ensures electrolyte accessibility; meanwhile, nanosized Fe3O4 promotes lithiation/delithiation, owing to numerous active sites, large electrolyte contact area, and a short lithium ion diffusion path. As a result, this Fe3O4/C composite electrode demonstrates an excellent cycling stability with a reversible capacity of 1008 mA h g(-1) over 400 cycles at 0.2C (1C = 1000 mA g(-1)), as well as a superior rate performance with reversible capacity of 660 and 580 mA h g(-1) at 3C and 5C, respectively.

In situ TEM observation of a microcrucible mechanism of nanowire growth

The growth of metal oxide nanowires can proceed via a number of mechanisms such as screw dislocation, vapor-liquid-solid process, or seeded growth. Transmission electron microscopy (TEM) can resolve nanowires but invariably lacks the facility for direct observation of how nanowires form. We used a transmission electron microscope equipped with an in situ heating stage to follow the growth of quaternary metal oxide nanowires. Video-rate imaging revealed barium carbonate nanoparticles diffusing through a porous matrix containing copper and yttrium oxides to subsequently act as catalytic sites for the outgrowth of Y₂BaCuO₅ nanowires on reaching the surface. The results suggest that sites on the rough surface of the porous matrix act as microcrucibles and thus provide insights into the mechanisms that drive metal oxide nanowire growth at high temperatures.

Formation of superconducting yttrium barium copper oxide using sulphur-containing templates

Protein from the acorn barnacle used to template high temperature superconductors.

One-step route to a hybrid TiO2/Ti x W1-x N nanocomposite by in situ selective carbothermal nitridation

Metal oxide/nitride nanocomposites have many existing and potential applications, e.g. in energy conversion or ammonia synthesis. Here, a hybrid oxide/nitride nanocomposite (anatase/Ti _x W_1-x N) was synthesized by an ammonia-free sol-gel route. Synchrotron x-ray diffraction, complemented with electron microscopy and thermogravimetric analysis, was used to study the structure, composition and mechanism of formation of the nanocomposite. The nanocomposite contained nanoparticles (<5 nm diameter) of two highly intermixed phases. This was found to arise from controlled nucleation and growth of a single oxide intermediate from the gel precursor, followed by phase separation and in situ selective carbothermal nitridation. Depending on the preparation conditions, the composition varied from anatase/Ti _x W_1-x N at low W content to an isostructural mixture of Ti-rich and W-rich Ti _x W_1-x N at high W content. In situ selective carbothermal nitridation offers a facile route to the synthesis of nitride-oxide nanocomposites. This conceptually new approach is a significant advance from previous methods, which generally require ammonolysis of a pre-synthesized oxide.

Self-assembled TiO2 nanospheres by using a biopolymer as a template and its optoelectronic application

Self-assembled TiO(2) nanoparticulate materials with well-defined spherical morphologies were synthesized by using a biopolymer sodium alginate as a template under different synthesis conditions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) techniques were used to characterize the TiO(2) nanoparticles. N(2) sorption analysis revealed the moderately good surface area (124.0 m(2) g(-1)) and pore volume (0.44 cm(3) g(-1)) of these TiO(2) nanoparticles. The biopolymer templating pathway leads to good-quality self-assembled TiO(2) nanoparticles with dimensions of ca. 10-12 nm within the synthesis temperature range of 0-60 °C. These porous TiO(2) nanomaterials showed high photogenerated current in the presence of a dye (Rose Bengal), used as a sensitizer for several photo on/off cycles.