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

A series of TiO₂–Cu₂O 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), N₂ 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 TiO₂–Cu₂O composite oxides exhibited better photocatalytic activity than Cu₂O or TiO₂ alone. Among these composite oxides, the 5%TiO₂–Cu₂O 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.     

Flower-like ZnO/BiOI p–n heterojunction composites for enhanced photodegradation of formaldehyde and dyes

Journal of Materials Science: Materials in Electronics - The fabrication of p–n heterojunctions was considered as a promising strategy to improve the photocatalytic efficiency of the...     

Preparation and properties of antibacterial TiO2@C/Ag core–shell composite

Abstract

An environment-friendly hydrothermal method was used to prepare TiO₂@C core–shell composite using TiO₂ as core and sucrose as carbon source. TiO₂@C served as a support for the immobilization of Ag by impregnation in silver nitrate aqueous solution. The chemical structures and morphologies of TiO₂@C and TiO₂@C/Ag composite were characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy and Brunauer–Emmett–Teller (BET) analysis. The antibacterial properties of the TiO₂@C/Ag core–shell composite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the viable cell counting method. The results indicate that silver supported on the surface of TiO₂@C shows excellent antibacterial activity.     

Bifunctional Fe3O4@C/YVO4:Sm composites with the core–shell structure

A novel Fe₃O₄@C/YVO₄:Sm³⁺ composites with magnetic and luminescent properties were reported. Firstly, the as-synthesized Fe₃O₄ nanoparticles were coated by carbon as a shell via a simple hydrothermal method. Furthermore, the Fe₃O₄@C nanoparticles were modified by YVO₄:Sm³⁺ phosphors through a simple sol–gel process to prepared the Fe₃O₄@C/YVO₄:Sm³⁺ microspheres. The characterization of as-prepared products were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and vibrating sample magnetometer (VSM). It is shown that Fe₃O₄@C/YVO₄:Sm³⁺ composites with well-crystallized and core–shell structure were prepared. Additionally, the Fe₃O₄@C/YVO₄:Sm³⁺ composites show excellent magnetic properties (13 emu/g) and luminescent properties, which made the composites useful for applications in biomedical devices such as magnetic bio-separation and drug/gene delivery.     

Optical properties of core–shell structured Ag/SiO2 nanocomposites

Silver nanoclusters coated by SiO₂ were synthesized by a reverse micelle technique to obtain a core–shell microstructure with tunable particle size less than 50 nm. The refractive indices of the Ag/SiO₂ nanocomposites were calculated based on a theoretical model for binary composite materials which illustrated a strong correlation to the size of the metallic core and the dielectric shell. Dynamic light scattering analysis of the Ag/SiO₂ nanocomposites revealed that the refractive index of the nanocomposites was about 2.40, which was well in the range predicted by theoretical modeling. Optical absorption spectra and silver quantum dot size induced color change of the Ag/SiO₂ nanocomposites suspension were also investigated.     

Synthesis and properties of magnetic solid superacid: SO4/ZrO2–B2O3–Fe3O4

A magnetic SO₄²⁻/ZrO₂–B₂O₃–Fe₃O₄ solid superacid catalyst is prepared via a simple chemical co-precipitation approach. The obtained materials were characterized in detailed by X-ray powder diffraction, thermogravimetric analysis–different scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), electron microscopy (SEM and TEM), and Mossbauer spectra. Powder X-ray diffraction patterns show that in this composite oxide the transformation temperature of ZrO₂ from tetragonal to monoclinic phase is higher compared to the pristine SO₄²⁻/ZrO₂ material. The introduction of Fe₃O₄ endows the superacid with a super-paramagnetic property while in a ferromagnetic state after calcination. The superacid exhibits high catalytic activity in forming ethyl acetate by esterification.     

Optical properties and structure of R2O–Ga2O3–SiO2 and RO–Ga2O3–SiO2 glasses

Refractive index and molar refraction of Li₂O–, Na₂O–, CaO–, and BaO–Ga₂O₃–SiO₂ glasses have been used to test the validity of a structural model of silicate glasses containing Ga₂O₃ glasses. Ga₂O₃ enters these types of glass in a similar manner as Al₂O₃. It is assumed that, for (SiO₂/Ga₂O₃) >1 and (Ga₂O₃/R₂O) ≤1, Ga₂O₃ associates primarily with modifier oxides to form GaO₄ units. The rest of modifier oxide forms silicate units with non-bridging oxygen ions. Silicate structural units have the same factors as found for binary alkali- and alkaline earth silicate glasses. Differences between experimental and model values suggest another structure for (Ga₂O₃/SiO₂) ≥1.     

Fabrication,physiochemical and optoelectronic characterization of SiO2/CdS core–shell nanostructures

Silica/CdS core–shell nanostructures have been developed using a simple wet chemical route. This method utilizes silica spheres formation followed by successive ionic layer adsorption and reaction method assisted CdS shell layer formation. The morphological studies revealed the uniformity in size distribution with core size of 250 nm and shell thickness of 9 nm. The electron microscopic images also indicate the irregular morphology of CdS shell layer. The structural studies indicate the simple cubic system of CdS shell with no other trace for impurities in the crystal structure. This CdS layer exhibit the band gap energy of 2.66 eV, due to weak quantum confinement and numerous defects presence. The studies on room temperature photoluminescence measurement indicate the emission properties and the corresponding electronic energy levels of defect states. Further, the physiochemical understanding of core–shell formation mechanism clearly matches with the motive behind the defects present in the CdS shell layer.     

Novel and simple route for the synthesis of core–shell chitosan–gold nanocomposites

This work presents a novel and simple route for the synthesis of water-soluble core–shell chitosan–gold nanocomposites. The experimental procedure can be summarized by the following steps: (i) chitosan deacetylation, (ii) chitosan depolymerization, (iii) chitosan nanoparticles’ formation and (iv) chitosan–gold nanocomposite formation. FT-IR spectroscopic results indicate that the formation of chitosan nanoparticles (ChtNPs) occurs via NH₃⁺ and PO⁻ groups electrostatic interactions, while UV–vis spectra points to a possible embedding of gold nanoparticles into the ChtNPs. This feature was confirmed by electronic transmission microscopy measurements. Chitosan and gold are biocompatible materials. Added to this, the obtained chitosan–gold nanocomposites presented thermal and absorbance properties which strongly point to their potential use in phototherapeutic processes.     

阳离子部分取代Cu2ZnSnS4的研究进展

P型半导体Cu_2ZnSnS_4(CZTS)由于具有最佳的直接带隙(1.0~1.5eV)、高的光吸收系数(超过104 cm~(-1))以及丰富、无毒的元素组成,使其成为商业化低成本太阳能电池最有希望的候选材料之一。然而,材料本身的一些缺陷制约了CZTS薄膜太阳能电池效率的提高。为了提高CZTS薄膜太阳能电池的效率,研究者们使用其他阳离子部分取代Cu、Zn或Sn来改善CZTS的缺陷。从CZTS的3种不同取代位置出发,综述了近年来各种阳离子部分取代CZTS的研究进展,同时对阳离子部分取代CZTS材料的发展前景进行了展望。     

磁控溅射制备Cu2ZnSnS4薄膜的研究进展

Cu_2ZnSnS_4(CZTS)薄膜由于其合适的禁带宽度、高的光吸收系数以及组分无毒、储量丰富等特性,被视为薄膜太阳能电池最佳的吸收层材料之一。磁控溅射是制备CZTS薄膜的主要方法之一,因为其制备过程相对简单且可以产业化,一直是太阳能电池领域的研究热点。从磁控溅射制备CZTS薄膜的3种路径出发,综述了近年来各种路径在制备CZTS薄膜方面的研究进展,比较了3种路径的优缺点,同时对磁控溅射制备CZTS薄膜的发展前景进行了展望。     

Structural and optical properties of individual GaP/ZnO core–shell nanowires

Structural and optical properties of ZnO–GaP core–shell nanowires were studied by means of electron microscopy and microphotoluminescence. A thin ZnO shell layer was deposited by RF sputtering on GaP nanowires, which were grown on GaP (111)B substrates under vapour–liquid–solid mode by MOVPE. The SEM and TEM characterization showed that the ZnO shells fully covered the surface of the NWs from top to bottom. Each GaP NW core is composed of many well-defined twinned segments with the planes of twinning oriented in perpendicular to the growth direction. This was contradicted in kinked GaP NWs: their growth direction was initially perpendicular to the twinning planes, but once the NW had kinked, it changed to lie within the twinning planes. The ZnO shell deposited on the GaP core has a columnar morphology. The columns are inclined at a positive angle close to 70° with respect to the GaP growth axis. All observed columns were tilted at this angle to the growth direction. Micro-photoluminescence study showed that thermal annealing improved the quality of the ZnO crystallographic structure; the annealing made observable the photoluminescence peak related to the band-to-band transition in ZnO.     

Glasses and glass-ceramics in the SrO–TiO2–Al2O3–SiO2–B2O3 system and the effect of P2O5 additions

The glass formation abilities of various compositions in SrO–TiO₂–Al₂O₃–SiO₂, SrO–TiO₂–B₂O₃–SiO₂, SrO–TiO₂–Al₂O₃–B₂O₃, and SrO–TiO₂–Al₂O₃–SiO₂–B₂O₃ systems were studied. Many new compositions were found to be suitable for the casting of crack-free, optically clear glasses of different color and with glass transition temperatures ranging from 595 to 775 °C. The crystallization behavior, structure, and thermal expansion behavior of selected glasses were analyzed by DTA, XRD, dilatometry, and heat treatment. The effect of P₂O₅ on the glass structure and crystallization behavior was also studied. P₂O₅ played a dual role depending on composition. In some glasses it acted as a nucleating agent while in others it suppressed crystallization. Heat treatment of borate and borosilicate glasses transformed them into glass-ceramics while comparable SrO–TiO₂–Al₂O₃–SiO₂ glasses showed a lower tendency to crystallize and form glass-ceramics under the same conditions.     

Preparation and characterization of high-performance Ni-based core–shell catalyst for ethanol steam reforming

Journal of Materials Science - A core–shell catalyst, based on nickel nanoparticles supported on silica nanospheres and surrounded by ceria, was tested for ethanol steam reforming (ESR)...     

Highlighting of structural units of B2O3–Li2O–P2O5 system under heat treatment

As technology evolves towards the design of small size – high efficiency devices there is a necessity for the development of solid, stable electrolytes that can be fabricated in various shapes. Accordingly, a glass system of xB₂O₃·0.4Li₂O·(0.6 − x)P₂O₅ with 0 ≤ x ≤ 0.6 mol%, was prepared by melting the raw materials at 1200 °C and rapidly cooling the melts at room temperature. The samples were afterwards heat treated to develop crystalline structures, for better identification of the units that build up the network.     

Surfactant assisted synthesis and multifunctional features of Fe3O4@ZnO@SiO2 core–shell nanostructure

In this study, hybrid core–shell magnetic nanostructure comprising Fe₃O₄ core with multiple shells of zinc oxide and silica having well defined morphologies are produced by a simple synthetic approach based on an effective chemical precipitation technique. Semi-solid and hydrophilic poly ethylene glycol was used as the stabilizing agent to control the particle size of the magnetic nanostructures. 1-Hexadecyltrimethyl ammonium chloride was employed as the surfactant to achieve the core–shell nanostructure. The formation of the core–shell nanostructures were confirmed by X-ray diffraction, Fourier transform infra-red spectroscopy and high resolution transmission electron microscopy respectively. We also observed the pronounced ferromagnetic features of ZnO coated Fe₃O₄ core–shell nanostructure that substantiates the magnetization reversal mechanism of the spinel magnetite. The coating of dense SiO₂ on Fe₃O₄@ZnO was found to shift the magnetic behaviour from ferromagnetic to super-paramagnetic even at room temperature. The optical features of the material are observed by UV–Vis Spectrometer and Photoluminescence spectrometer.     

Synthesis and properties of glasses in the K2O–SiO2–Bi2O3–TiO2 system and bismuth titanate (Bi4Ti3O12) nano glass–ceramics thereof

Glasses were prepared by the melt-quench technique in the K₂O–SiO₂–Bi₂O₃–TiO₂ (KSBT) system and crystallized bismuth titanate, BiT (Bi₄Ti₃O₁₂) phase in it by controlled heat-treatment at various temperature and duration. Different physical, thermal, optical, and third-order susceptibility (χ³) of the glasses were evaluated and correlated with their composition. Systematic increase in refractive index (n) and χ³ with increase in BiT content is attributed to the combined effects of high polarization and ionic refraction of bismuth and titanium ions. Microstructural evaluation by FESEM shows the formation of polycrystalline spherical particles of 70–90 nm along with nano-rods of average diameter of 85–90 nm after prolonged heat treatment. A minor increase in dielectric constants (ε_r) has been observed with increase in polarizable components of BiT in the glasses, whereas a sharp increase in ε_r in glass–ceramics is found to be caused by the formation of non-centrosymmetric and ferroelectric BiT nanocrystals in the glass matrix.     

Synthesis,characterization and bactericidal activity of silica/silver core–shell nanoparticles

Silica/silver core–shell nanoparticles (NPs) were synthesized by coating silver NPs on silica core particles (size ~300 ± 10 nm) via electro less reduction method. The core–shell NPs were characterized for their structural, morphological, compositional and optical behavior using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and UV–Visible spectroscopy, respectively. The size (16–35 nm) and loaded amount of silver NPs on the silica core were found to be dependent upon reaction time and activation method of silica. The bactericidal activity of the NPs was tested by broth micro dilution method against both Bacillus subtilis (gram positive) and Escherichia coli ATCC25922 (gram negative) bacterium. The bactericidal activity of silica/silver core–shell NPS is more against E. coli ATCC25922, when compared to B. subtilis. The minimal inhibitory concentration of the core–shell NPs ranged from 7.8 to 250 μg/mL and is found to be dependent upon the amount of silver on silica, the core. These results suggest that silica/silver core–shell NPs can be utilized as a strong substitutional candidate to control pathogenic bacterium, which are otherwise resistant to antibiotics, making them applicable in diverse medical devices.