Zhengping Fu

Synthesis of Ag/ZnO nanorods array with enhanced photocatalytic performance

Silver-modified ZnO nanorods array has been prepared and the effect of silver modification has been studied. ZnO nanorods array were fabricated through a wet chemical route and a photo deposition method was taken to fabricate silver nano particulate on the ZnO nanorods. The structural and optical properties were characterized by field emission scanning electron microscope, high resolution transmission electron microscope, X-ray photoelectron spectroscopy, Raman, UV-vis and photoluminescence (PL) spectra. The UV photocatalytic activity of these materials was studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The photocatalytic performance indicated that Ag deposit acted as not only electron sinks to enhance the separation of photoexcited electrons from holes, but also charge carrier recombination centers, so the optimized amount of Ag deposit was investigated.

An intense ultraviolet photoluminescence in sol?gel ZnO?SiO2 nanocomposites

We report the phenomenon that the intensity of the ultraviolet (UV) photoluminescence (PL) from ZnO was greatly enhanced by incorporating ZnO into the SiO2 matrix. PL excitation results show that both the ZnO nanoparticles and the SiO2 matrix in the nanocomposites contribute to the luminescence process for the UV band. On the basis of the x-ray photoelectron spectra, we suggest that interface energy states are formed due to the presence of Zn?O?Si bonds between ZnO nanoparticles and the SiO2 matrix. A tentative model concerning the contribution of the ZnO nanoparticles, SiO2 matrix, and ZnO?SiO2 interface is suggested to explain the PL enhancement effect.

Low magnetic field response single-phase multiferroics under high temperature

A single-phase material where ferroelectricity and ferromagnetism coexist at room temperature (RT) is hardly available at present, and it is even more rare for such a material to further have an intrinsic and low magnetic field response magnetoelectric (ME) coupling at temperatures higher than RT. In this communication, a new single-phase Aurivillius compound, SrBi5Fe0.5Co0.5Ti4O18 has been discovered that exhibits a plausible intrinsic ME coupling. Remarkably, this property appears at a high temperature of 100 °C, surpassing all single-phase multiferroic materials currently under investigation. With a magnetocapacitance effect detectable at 100 °C and under a low response magnetic field, a RT functioning device was demonstrated to convert an external magnetic field variation directly into an electric voltage output. The availability of such a single-phase material with an intrinsic and low magnetic field response that is multiferroic at high temperature is important to the fundamental understanding of physics and to potential applications in sensing, memory devices, quantum control, etc.

Visible light responsive Bi7Fe3Ti3O21 nanoshelf photocatalysts with ferroelectricity and ferromagnetism

In this work, single-phase ferroelectric (FE) and ferromagnetic (FM) layer-structured semiconductive Aurivillius Bi7Fe3Ti3O21 nanoshelves with a direct band gap of ∼2.22 eV were controllably synthesized by a facile hydrothermal method. The nanoshelf structure could suppress the unwanted aggregation problem introduced by spontaneous polarization and ensure a high Brunauer–Emmett–Teller surface area. The Bi7Fe3Ti3O21 nanoshelves with co-existing FE and FM properties were demonstrated as visible-light-driven photocatalysts for decomposing Rhodamine B. This finding may open a window for developing new visible-light-driven photocatalysts because the used layer-structured Aurivillius phase has significant potential in elemental doping and further structural engineering applications.

Nanosheet array assembled by TiO2 nanocrystallites with {116} facets parallel to the nanosheet surface

An anatase TiO2 nanosheet array (TNSA) assembled by {116} facet-oriented nanocrystallites with {116} facets parallel to the surface is synthesized directly on a fluorine-doped tin oxide substrate via a two-step process, and exhibits 50% higher photocatalytic activity than {001} facet-oriented TNSA. The precursor and TNSA are both suggested to be grown via the “oriented attachment” mechanism.

Correlation between 577cm−1 Raman scattering and green emission in ZnO ordered nanostructures

We have investigated resonant Raman scattering (RRS) and photoluminescence of ZnO inverse opal prepared by electrodeposition. The intensities of both 577cm−1 Raman scattering and green emission get weaker after aging or UV laser irradiation. The RRS and green emission intensities are highly correlated for different samples, regardless of the means of sample treatment. According to the deposition-temperature and annealing-temperature dependences, we propose that the origins of the two peaks are related to surface hydroxide.

Enhanced visible photocatalytic activity of hybrid Pt/α-Fe2O3 nanorods

α-Fe2O3 nanorods with highly defective surfaces were used as a support to further synthesize hybrid Pt/α-Fe2O3 nanorods. Transmission electron microscopy analyses suggest that Pt nanoparticles are selectively deposited on the surface defects such as edge-steps. Pt nanoparticles in metallic and electron deficient states, as well as the correlation between chemisorbed oxygen species and the peripheral Pt area, were revealed by the X-ray photoelectron spectroscopy spectra. The hybrid nanorods with an optimized amount of Pt nanoparticles and a large peripheral Pt area exhibit far better visible light photocatalytic activity for degrading methylene blue than α-Fe2O3.

Observation of Exchange Anisotropy in Single-Phase Layer-Structured Oxides with Long Periods.

A remarkable exchange bias effect arising from the temperature-dependent interaction among the ferromagnetic-like cluster glasses and antiferromagnetic regions was observed in a newly developed single-phase multiferroic compound of Bi10Fe6Ti3O30 which has a nine-layer Aurivillius structure. Inhomogeneous distribution of magnetic Fe ions inside this long-period layered structure was experimentally identified via the atomic level imaging. The results confirmed the presence of the short-range magnetic ordering (the cluster glassy state) and the canted antiferromagnetism, and then the direct interaction among them was further confirmed. Finding of this new single-phase material accompanying this remarkable exchange bias effect would be beneficial to both basic physics understanding and the potential device development.

Enhanced yellow–green photoluminescence from ZnO–SiO2 composite opal

A remarkably enhanced yellow–green photoluminescence (PL) was observed from ZnO nanocrystals infiltrated into SiO2 opal photonic crystals. It was clearly visible to the naked eye under the excitation of an Xe lamp and had substantially improved thermal stability over pure ZnO nanocrystals. The PL spectrum shape of a ZnO–SiO2 composite opal can be modified by annealing an SiO2 opal or choosing an SiO2 opal with different lattice parameters. The enhancement of PL intensity is interpreted based on the dependence of the PL intensity on the size of SiO2 microspheres as well as the anisotropy of the photoluminescence excitation (PLE) spectra. Our results may be interesting for further application.

Multifunctional Single-Phase Photocatalysts: Extended Near Infrared Photoactivity and Reliable Magnetic Recyclability.

A practical photocatalyst should be able to integrate together various functions including the extended solar conversion, a feasible and economic recyclability, and above the room temperature operation potential, et al., in order to fulfill the spreading application needs in nowadays. In this report, a multifunctional single-phase photocatalyst which possesses a high photoactivity extended into the near infrared region, an easy magnetic recyclability and the high temperature stability was developed by doping Co into a new layer-structured Bi7Fe3Ti3O21 material. Light absorption and photocatalytic activity of the resulted Bi7Fe3-xCoxTi3O21 photocatalyst were extended to the long wavelength as far as 800 nm. Its strong ferromagnetism above the room temperature enables the nanopowders fully recyclable in viscous solutions simply with a magnet bar in an experimental demonstration. Furthermore, such photoactivity and magnetic recyclability were heavily tested under high-temperature and high-viscosity conditions, which was intended to simulate the actual industrial environments. This work brings the bright light to a full availability of a new multifunctional photocatalyst, via integrating the much enhanced ferromagnetic, ferroelectric, optoelectronic properties, most importantly, into a single-phase structure.