Zhengying Wu

Smart photocatalytic removal of ammonia through molecular recognition of zinc ferrite/reduced graphene oxide hybrid catalyst under visible-light irradiation

Zinc ferrite loaded with reduced graphene oxide (ZnFe2O4/rGO) and zinc ferrite (ZnFe2O4) catalysts were synthesized via a one-spot method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, surface photovoltage spectroscopy and X-ray photoelectron spectroscopy. Results revealed that the as-synthesized ZnFe2O4/rGO and ZnFe2O4 particles were cubic spinel-type ZnFe2O4 with space group number of Fd3m, and that their average diameters were 7.4 and 7.0 nm, respectively. The photocatalytic results indicated that the ZnFe2O4/rGO hybrid catalyst possesses higher activity than that of the single ZnFe2O4 component under visible-light irradiation. More importantly, the ZnFe2O4/rGO catalyst could recognize ammonia from an organic pollutant-ammonia mixed solution and selectively degrade ammonia and nitrogen gas based on the coordination recognition between Zn cations on ZnFe2O4 and ammonia in solution. Fourier-transform infrared, Raman and X-ray photoelectron spectra confirmed that ammonia was selectively adsorbed on ZnFe2O4 particles. The shifts of Zn 2p3/2 and Zn 2p1/2 binding energies confirmed the coordination between Zn cations and ammonia. The surface photovoltage spectra revealed that the photo-generated holes moved to the surface of ZnFe2O4 particles upon incident visible-light irradiation, and degraded ammonia adsorbed on the catalyst surface. These findings will encourage more investigations of photocatalysis based on coordination recognition.

Fabrication of mesoporous Al-SBA-15 as a methylene blue capturer via a spontaneous infiltration route

Different amounts of aluminum (Al) species were infiltrated and incorporated into SBA-15 by grinding the mixture of aluminum nitrate and SBA-15 followed with a subsequent calcination. A novel series of methylene blue adsorbents were thus obtained and characterized by X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared and 27Al Nuclear Magnetic Resonance (NMR) techniques. Results show that the newly synthesized Al-SBA-15 materials have well-preserved mesostructures, high BET surface areas, enlarged pore sizes and predominantly tetrahedrally coordinated Al species. All Al-SBA-15 materials show a greater adsorption capacity to methylene blue than SBA-15, where the sample (Al/Si = 0.05) has the largest capacity to remove MB from water solution. Diffuse reflectance measurements, Langmuir and Freundlich equations and the pseudo-second-order kinetic model were further used to describe the adsorption behavior of MB onto SBA-15 and Al-SBA-15 materials. Finally, recycling tests were performed to evaluate the stability of the Al-SBA-15 material and the textural and NMR properties of the used samples were also detected.

Graphene sheet-starch platform based on the groove recognition for the sensitive and highly selective determination of iodide in seafood samples

The functionalization of graphene nanosheets was realized using a simple starch mixture to achieve a highly selective recognition of iodide, thereby surmounting the complicated reactions possibly leading to low yield during functionalization. The groove recognition for starch to iodide, a novel recognition model, was established. The starch-to-graphene nanosheet mass ratio of 3:2 produced an optimal current signal. The recognition and measurement procedures were conducted in different cells, respectively. These procedures improved the selectivity and sensitivity, and overcame the possibility of interference from coexisting ions. Under optimal conditions, the graphene sheet-starch electrode was immersed in a recognition cell at pH 2.0 for 10min, afterward, in a measurement cell at pH 1.0 for quantitative analysis, resulting in the highest current signals obtained. The quantitative electrochemical measurements yielded a mean value of 214.6mg/kg in actual samples of commercially available seafood sample, whereas the spectrophotometric measurements produced a mean value of 226.7mg/kg. If the spectrophotometric value for the seafood sample is accurate, the percentage error for the electrochemical method is only 5.3%. Therefore, the electrochemical method is reliable for qualitative iodide measurements. The groove recognition was highlighted to elucidate the specific selectivity.

Adsorption of phenol from aqueous solution by a hierarchical micro-nano porous carbon material

A hierarchical micro-nano porous carbon material (MNC) was prepared using expanded graphite (EG), sucrose, and phosphoric acid as raw materials, followed by sucrose-phosphoric acid solution impregnation, solidification, carbonization and activation. Nitrogen adsorption and mercury porosimetry show that mixed nanopores and micropores coexist in MNC with a high specific surface area of 1978 m2·g−1 and a total pore volume of 0.99 cm3·g−1. In addition, the MNC is found to consist of EG and activated carbon with the latter deposited on the interior and the exterior surfaces of the EG pores. The thickness of the activated carbon layer is calculated to be about one hundred nanometers and is further confirmed by scanning electron microscope (SEM) and transmission election microscope (TEM). A maximum static phenol adsorption of 241.2 mg·g−1 was obtained by using MNC, slightly higher than that of 220.4 mg·g−1 by using commercial activated carbon (CAC). The phenol adsorption kinetics were investigated and the data fitted well to a pseudo-second-order model. Also, an intra-particle diffusion mechanism was proposed. Furthermore, it is found that the dynamic adsorption capacity of MNC is nearly three times that of CAC. The results suggest that the MNC is a more efficient adsorbent than CAC for the removal of phenol from aqueous solution.

Synthesis and electro-magnetic properties of flower-like Fe2O3-Ag nanocomposite using direct subsidence loading method

Novel flower-like Fe2O3/Ag nanocomposites were synthesized by a simple direct subsidence loading method. The composition and morphology of the obtained samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SEAD) techniques. The Ag nanoparticles which loaded on the surface of petals exhibit spherical morphology. Further, the magnetic and electrical conductive properties reveal the well controllable performance. Room temperature magnetic measurement of the flower-like nanocomposites demonstrated its ferromagnetic properties and the saturation magnetization (Ms) decreased from 0.6 to 0.11 emu/g.

Effects of period number and sputtering time on optical properties of Si/Ge multilayer films deposited by magnetron sputtering

Si/Ge multilayer films were deposited by radio frequency magnetron sputtering method, and effects of period number and sputtering time on structure and optical absorption properties of the films were investigated by XP-1 profilometer, XRD, SEM, AFM, Ramman and UV–Vis techniques. Results indicated that the films exhibited the incomplete crystallization, and the appropriate period number benefited the ordering of the Si. Simultaneously, the films showed smooth growth, and the islands were spread all over the surface, and changing of the roughness was attributed to the interface effects. Strong absorption range in the UV–Vis spectra was enlarged with increasing period numbers, and there was a general trend for the band gaps to decrease with increasing period numbers, accompanied the gradually decreasing amplitude. Theoretical calculation and analysis displayed that the ECB value gradually increased and the EVB value gradually decreased with the increasing period number, eventually resulting in the decreasing band gap, and the corresponding values remained stable at different sputtering time when period number was 5.

Excellent Surface Enhanced Raman Scattering of SiO 2 Fiber Membrane Embedded with Ag Nanoparticles

Uniformly distributed Ag nanoparticles supported on SiO2 fiber membrane materials were successfully synthesized using electrospinning and pyrolysis. In this study, the electrostatic spinning solution is composed mainly of polyvinyl pyrrolidone, ethyl silicate (TEOS) and AgNO3. The structural and morphological studies of the materials after calcination were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and thermogravimetric analysis–differential scanning calorimetry (TG–DSC). The results indicated that the samples had a rough surface structure. The load on the nanofibers was silver (Ag) metal, and the number and grain size of Ag nanoparticles increased as the relative amounts of AgNO3 increased. Furthermore, the surface enhanced Raman scattering (SERS) activity of the Ag/SiO2 was investigated using the common antibiotic enrofloxacin as a probe. It was found that the amorphous silica fiber with uniform loading of Ag nanoparticles exhibited a strong SERS enhancement effect. Due to the analytical performance, the predicted potential for SERS detection of trace antibiotics is excellent.

Facile Synthesis of Mn 3 O 4 Nanoparticles Decorated Graphene as Enhanced Performance Electrode for Supercapacitor

Graphene was prepared by using the plant stem as a biotemplate through high temperature carbonization and Mn3O4/graphene composites were then prepared via a simple hydrothermal process. The surface morphology and structure of the Mn3O4/graphene hybrids were characterized by X-ray diffraction spectroscopy (XRD), Raman spectra, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrogram (XPS), N2 adsorption–desorption isotherms and electrochemical test. The results showed that the metal oxide nanoparticles were uniformly supported on the surface of graphene. Judging from the XRD, XPS and Raman, we could acquire that the Mn3O4 nanoparticle was in the crystal form while the average crystallite size was about 21 nm. The composites exhibited excellent specific capacitance as high as 196 F/g and the capacitance of the composites was 88% retained after 1000 cycles in 1 M Na2SO4 electrolyte at a charging rate of 2 A/g. The superior electrochemical properties could be due to the improved accessible area for ions in electrolytes and enhanced conductivities. The present study provides a facile way to design a high-performance Mn3O4/graphene based supercapacitor electrode and the concept is extendable to other pseudo capacitive electrodes.