Mesoporous carbon capsules encapsulated with Fe₃O₄ nanoparticles were prepared by the successive coating of a silica layer and a subsequent mesoporous silica/carbon layer on the surface of Fe₃O₄ nanoparticles followed by chemical etching with NaOH solution. TEM observations show that the as-obtained samples had a rattle-like structure: Fe₃O₄ nanoparticles were encapsulated in the interior of the mesoporous carbon capsules. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1570 m² g⁻¹, and the total pore volume is about 3.02 cm³ g⁻¹. The porous wall structure of the lateral carbon capsules provides the sufficient spaces that contribute to high adsorption capacities and faster adsorption rates of pollutants molecules in aqueous media. The nanocomposites are superparamagnetic at room temperature with a saturation magnetization of 5.5 emu g⁻¹, which provides the prerequisite for the fast magnetic separation in wastewater treatment application. Water treatment experiments indicated that the as-prepared samples exhibited higher adsorption rates and more effective removal capacity of organic pollutants compared with commercial activated carbon (AC), and their maximum adsorption capabilities for methylene blue (MB), congo red (CR), and phenol reached 608.04, 1656.9 and 108.38 mg g⁻¹, respectively. The multifunctional nanocomposites can be potentially used as absorbents for fast, convenient, and highly efficient removal of pollutants from the wastewater, which will play important roles in the purification or desalination of natural water and industrial effluents.

An effective electric current model based on defect engineering is proposed, and by applying this model, α-MoO ₃ , a non-SERS or weak SERS, active substrate, can be transformed into a SERS-active substrate with an enhancement factor as high as 1.8 × 10 ⁷ and a detection limit of 10 ⁻⁸ M for R6G. This model can be used to predict the SERS performance of other metal oxide semiconductors.

Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe₃O₄@SiO₂@TiO₂ nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO₂ (P25), pure TiO₂ microspheres, Fe₃O₄@SiO₂@TiO₂ and annealed Ag@Fe₃O₄@SiO₂@TiO₂ nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe₃O₄@SiO₂@TiO₂ hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe₃O₄@SiO₂@TiO₂ photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues.

The optical properties of $\delta \text{-}{\mathrm{Bi}}_2{\mathrm{O}}_3$ thin films were investigated using spectroscopic ellipsometry and optical absorption spectrum. $\delta \text{-}{\mathrm{Bi}}_2{\mathrm{O}}_3$ thin films were grown on Si and quartz substrates under different oxygen flow ratios (OFR) by radio frequency reactive magnetron sputtering. The Tauc-Lorentz dispersion method was adopted to model the optical dispersion functions of the thin films. The optical bandgap was obtained by three different methods. It was found that refractive index and extinction coefficient decrease, and the optical bandgap has a slight blue shift with increasing the OFR. Factors influencing the optical constants and optical bandgap are discussed.

This paper reports the phase transition temperature regulation of VO₂ (M) nanoparticles using interfacial defects and size effect other than the traditional doping routine. The nanoparticles exhibit excellent thermochromic performance and a low threshold voltage.