Jianyi Shen

Photocatalytic degradation of dodecyl-benzenesulfonate over TiO2-Cu2O under visible irradiation.

A series of TiO(2)-Cu(2)O mixed oxides were prepared by the hydrolysis of titanium butoxide and reduction of copper acetate with hydrazine. These composite oxides were characterized by X-ray diffraction (XRD), inductively coupled plasma spectrometry (ICP), high-resolution transmission electron microscopy (HRTEM), N(2) adsorption and UV-vis techniques. Photocatalytic degradation of dodecyl-benzenesulfonate (DBS) under visible irradiation was performed, and effects of composition of catalysts and reaction conditions were studied. It was observed that TiO(2)-Cu(2)O composite oxides exhibited better photocatalytic activity than Cu(2)O or TiO(2) alone. Among these composite oxides, the 5%TiO(2)-Cu(2)O displayed the highest activity, and the degradation percentage of DBS and COD reached 97.3% and 65%, respectively. In addition, it was found that the decomposition of DBS followed the first-order kinetics and the adsorption of DBS followed the Langmuir model. Oxygen in solution played a vital role in the elimination of COD.

New synthesis method for nickel phosphide nanoparticles: solid phase reaction of nickel cations with hypophosphites

Nanoparticles of Ni2P were simply prepared by a solid phase reaction of H2PO2− with Ni2+ in N2 at relatively low temperatures, which exhibited high activity for the hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of quinoline.

Reduction of supported iron oxide studied by temperature-programmed reduction combined with mössbauer spectroscopy and X-ray diffraction

The reduction of iron oxide supported on alumina, anatase and rutile and the interactions between iron oxides and these supports have been studied using temperature-programmed reduction, Mossbauer spectroscopy and X-ray diffraction. The intermediates formed during reduction depend strongly on the nature of the support, the iron loading and the reduction conditions used. Several iron species such as bulk α-Fe2O3, superparamagnetic α-Fe2O3 and surface iron–aluminium oxides are found in the alumina-supported iron oxide samples. The iron–aluminium species can be formed either by incorporation of Al3+ into the structure of iron oxide in acidic solution during the preparation of the samples or by incorporation of Fe2+ into the structure of the alumina support under high-temperature reduction. For the as-prepared Fe/TiO2 samples, the anatase and rutile have only weak interactions with the iron oxide as only bulk α-Fe2O3 species have been detected. However, some intermediates such as (1 –x)FeTiO3–xFe2O3 solid solution, surface iron–titanium oxide and bulk FeTiO3 phase can be formed during reduction because of the reducibility and mobility of titanium ions on the surface. Surface titanium ions can act as an electron-transfer medium for the reduction of Fe3+ to Fe2+ and can even be substituted for Fe3+ ions in the octahedral sites of magnetite formed during the reduction. In all cases, when the loading of iron oxide is low, Fe3+ and Fe2+ ions are stable during reduction due to the formation of iron oxide–support intermediates by strong interactions between iron oxides and the supports.

Mesoporous carbon materials prepared from carbohydrates with a metal chloride template

A new and facile method was developed for the preparation of mesoporous carbon materials from soluble and hydrolyzable carbohydrates with a metal chloride template. The preparation procedure and related mechanism were demonstrated using fructose and ZnCl2 as examples of the carbon precursor and template, respectively. Since both fructose and ZnCl2 are soluble in water, they can be mixed homogeneously initially. Fructose was first hydrolyzed to hydroxymethylfurfural, which was then polymerized to form a resin; both reactions were catalyzed by the acidic ZnCl2. During the carbonization, ZnCl2 might act as an activation agent promoting the carbonization of cured resin and a template for the formation of mesopores. Mesoporous carbon materials with high surface areas (1400–2000 m2 g−1), large pore volumes (1.44–2.72 cm3 g−1) and 100% mesopores with an average size of 3–7 nm can be prepared by using this simple and cost-effective method. The materials could be used as adsorbents and catalyst supports for relatively large molecules.

Enhanced ultraviolet photoluminescence from SiO2/Ge:SiO2/SiO2 sandwiched structure

SiO2/Ge:SiO2/SiO2 sandwiched structure was fabricated for exploring efficient light emission. After annealed in N2 (O2<1%), this structure shows three photoluminescence (PL) bands at 293, 395, and 780 nm. The intensity of the 395 nm band is largely enhanced in comparison with that from the monolayered Ge:SiO2 film. Spectral analyses suggest that the three PL bands originate from S1→S0, T∑(T∏)→S0, and T∏′→S0 optical transitions in GeO color centers, respectively. The improvement of the GeO density resulting from the confinement on Ge diffusion is responsible for the enhanced ultraviolet PL. This structure is expected to have important applications in optoelectronics.

A study of Fe-Ni-B ultrafine alloy particles produced by reduction with borohydride

Fe‐B, Fe‐Ni‐B, and Ni‐B ultrafine alloy particles have been prepared by reduction of metal ions in aqueous solution with borohydride. It is shown that iron and nickel contents in the particles can be easily varied by changing the Ni/(Ni+Fe) ratio in the aqueous solution; however, the boron content is constant when the concentration of the borohydride is kept constant. Several experimental results show that the alloy particles are amorphous. The scanning electron microscopic image indicates that the surface morphology of Fe35Ni15B26 alloy particles looks like cotton clusters. From the high‐resolution image, the average size of the high‐resolution image, the average size of the particles was determined to be about 30±5 nm and the fine structure of the particles indicates that there is an obvious boundary between the outer shell with a thickness of about 5 nm and the inner core with a diameter of about 20 nm. The particles are partially crystallized on the outer shell while the inner core is almost completel...

Investigation of Ni–P–B ultrafine amorphous alloy particles produced by chemical reduction

Ni–P–B ultrafine amorphous alloy particles have been prepared by chemical reaction of nickel chloride, sodium hypophosphite, and potassium borohydride in aqueous solution. Two samples prepared at different initial pH values (pH=5 and 9) have been characterized by different experimental methods. X‐ray and electron diffraction indicated that both samples were amorphous in nature, and transmission electron microscopy gave average diameters of 50 and 30 nm for particles prepared at pH=5 and 9, respectively. X‐ray photoelectron spectroscopy revealed that nickel and phosphorus existed exclusively in their elemental states, while boron existed mainly in its elemental state but with some trace of its oxide on the surface. The crystallization process of the amorphous samples was investigated by differential scanning calorimetry and by x‐ray diffraction after annealing the samples at various temperatures. The results are correlated with the microstructure of the as‐prepared samples. It is found that when the initial pH of the reaction mixture is adjusted to 9, the pH value can be maintained automatically throughout the reaction and the sample thus formed has a fairly homogeneous microstructure.

The preparation of Ni‐P ultrafine amorphous alloy particles by chemical reduction

Ni‐P ultrafine amorphous alloy particles have been prepared by reacting nickel chloride and sodium hypophosphite in an aqueous solution. X‐ray diffraction revealed the amorphous structure of the particles and transmission electron microscopy showed that the particles are spherical, with an average diameter of about 150 nm. X‐ray photoelectron spectroscopy confirmed that all nickel and phosphorus atoms are in the elementary state on the surface of the particles, which implied the alloying state of the particles. The dynamic process of the reaction has been studied. It is found that the reaction ended within 65 min at a pH value of 10 and 351 K when the sodium hypophosphite was exhausted, and the unreacted solid residue Ni(OH)2 should be washed out with ammonia solution to obtain ‘‘pure’’ Ni‐P ultrafine amorphous alloy particles.

Spherical amorphous nickel-phosphorus alloy particles with uniform size prepared at room temperature☆

A new chemical method for preparing ultrafine amorphous Ni85P15 alloy particles with uniform size and spherical shape is reported. The particles were prepared by reduction of nickel chloride with sodium hypophosphite initiated with a drop of potassium borohydride solution at room temperature. The preparation mechanism, which consists of primary nucleation of NiB followed by autocatalytic deposition of the components, is discussed. The amorphous structure of the particles was identified by X-ray diffraction and selected area electron diffraction. X-ray photoelectron spectroscopy indicated that nickel and phosphorus are present as an alloy. Transmission election microscopy revealed that the particles are uniform and spherical with a diameter of about 100 nm.

Evidence for ferroelectric border traps near the SrBi2Ta2O9/Si interface through capacitance–voltage measurement

A metal–ferroelectric–semiconductor (MFS) structure has been developed by depositing SrBi2Ta2O9 (SBT) films directly on n-type (100) Si by pulsed laser deposition. In the MFS structure, evidence for ferroelectric border traps in the SBT film has been obtained by high-frequency capacitance–voltage (C–V) measurement. When the ramp rate of voltage is higher than 200 mV/s, typical ferroelectric C–V hysteresis loops with the counterclockwise direction are obtained in C–V plots. When the ramp rate is lower than 80 mV/s, the ferroelectric hysteresis loops are replaced by the trap-induced ones with the clockwise direction. This pronounced change results from the fact that more and more border traps in SBT can communicate with the underlying Si. The border-trap density at the ramp rate of 10 mV/s is as high as 1.8×1012 cm−2. Moreover, the width of the hysteresis loops changes linearly with the logarithmic decrease in ramp rate, which is consistent with the ferroelectric border traps communicating with Si by tunnel...