海绵状Ag2O/ZnO复合光催化剂的制备及对甲醛的可见光降解

为克服纳米ZnO晶体可见光光催化活性低的缺点,以六水合硝酸锌、六亚甲基四胺和二水合草酸为原料,采用液相共沉淀-热分解法制备了六方纤锌矿型海绵状ZnO,然后在碱性条件下复合纳米Ag₂O颗粒,得到海绵状Ag₂O/ZnO复合光催化剂,并采用XRD、FTIR、紫外-可见漫反射（UV-Vis DRS）、FESEM、TEM和BET测量仪对其进行了表征;采用可见光光源,甲醛（HCHO）液体为光催化反应模型物,研究了不同摩尔比下Ag₂O/ZnO复合光催化剂的暗吸附及光催化性能。结果表明,随着Ag₂O相对含量的增加,HCHO暗吸附效果出现先增大后减小的趋势,当Ag₂O与ZnO摩尔比为1∶5时,HCHO去除率达到43.34%;另一方面,在可见光下Ag₂O/ZnO复合光催化剂对HCHO的降解率呈先增大后减小的趋势,其中Ag₂O与ZnO的摩尔比为1∶10时取得最佳降解效果,经过90 min的可见光光照后HCHO降解率达到78%,总的HCHO去除率为85%。      

The fabrication of hollow cubic-like CuInS2 cages using Cu2O crystals as sacrificing template

Hollow cubic-like CuInS₂ cages were prepared with cubic Cu₂O nanocrystals as self-sacrificing template through solvothermal process. The formation of these hollow structures could be attributed to the migration of copper ions and the copy of cubic Cu₂O template based on the Kirkendall effect and the Ostwald ripening process. Such process and mechanism might be extended to synthesize other hollow ternary chalcogenide materials.     

Preparation of graphene nanosheets/SnO2 composites by pre-reduction followed by in-situ reduction and their electrochemical performances

The Graphene nanosheets/SnO₂ composites were synthesized using stannous chloride to restore the semi-reduction graphene oxide (SRGO) under a simple hydrothermal reduction procedure. First graphene oxide was pre-reduced by glucose for a certain time to get SRGO, which keeps the good water-solubility of graphite oxide (GO) and has a good conductivity like graphene nanosheets. The higher electrostatic attraction between SRGO and Sn²⁺ makes SnO₂ nanoparticles tightly anchor on the graphene sheets in the hydrothermal reduction process. The formation mechanism of the composite was investigated by SEM, TEM, XRD, AFM and Raman. Moreover, the electrochemical behaviors of the Graphene nanosheets/SnO₂ nanocomposites were studied by cyclic voltammogram, electrical impedance spectroscopy (EIS) and chronopotentiometry. Results showed that the Graphene nanosheets/SnO₂ composites have excellent supercapacitor performances: the specific capacitance reached 368 F g⁻¹ at a current density of 5 mA cm⁻², and the energy density was much improved to 184 Wh kg⁻¹ with a power density of 16 kW kg⁻¹, and capacity retention was more than 95% after cycling 500 cycles with a constant current density of 50 mA cm⁻². The experimental results and the thorough analysis described in this work not only provide a potential electrode material for supercapacitors but also give us a new way to solve the reunification of the graphene sheets.     

Synthesis and solid characterization of nitrogen and sulfur-doped TiO2 photocatalysts active under near visible light

A series of N, S-substituted Titanium (IV) (diisopropoxide) bis (2,4-pentadionate) precursor were synthesized by the sol-gel method. The obtained solids were calcined at 550 °C for two hours to obtain photoactive phases. A thermogravimetric analysis of the solid precipitates shows that crystallization has been almost completed at this value of calcination temperature. The samples were characterized by X-Ray diffraction (XRD), determination of the BET specific surface area and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the obtained catalyst was estimated on a basis of decolouration of Congo red dye under near visible light.     

Photocatalytic activity of nitrogen doped rutile TiO2 nanoparticles under visible light irradiation

This work provides the design and synthesis of nitrogen doped rutile TiO₂ nanoparticles working as efficient photocatalysts under visible light irradiation. Nitrogen doped rutile TiO₂ nanoparticles are synthesized through the surface nitridation of rutile nanoparticles, which have been prepared in advance. The experimental results show that the nitrogen element is easily doped into the lattice of TiO₂ nanoparticles and its doping amount increases with the decrease of nanocrystallite size. The photocatalytic activity of the nanoparticles under visible light irradiation is correlated not only with the amount of doped nitrogen element but also with the morphology and crystallinity of nanoparticles.     

磁控溅射制备Cu2O和Cu2O/TiO2复合膜及其光催化活性

采用直流反应磁控溅射的方法在普通玻璃上沉积得到Cu2O、TiO2和Cu2O/TiO2复合薄膜.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线能谱仪(EDS)对薄膜的晶体结构、表面形态和薄膜元素组成进行了分析.XRD结果表明,当反应溅射时间为5 min时,Cu2O薄膜由单一的(111)晶面组成;反应时间的延长促进了Cu2O(110)和(220)晶面的生长.通过计算得出Cu2O(111)更有利于对O2的吸附.进一步使用氙灯作为光源,用薄膜对亚甲基蓝(MB)的降解率来表征光催化活性.结果表明,Cu2O/TiO2复合薄膜的光催化效果随着Cu2O含量的增加升高而后降低,当Cu2O含量为2.6mol%时,光催化活性最高.光催化效率的提高主要归因于Cu2O的加入引起光生电子-空穴的分离,而过量的Cu2O会延长光生电子迁移到Cu2O/TiO2界面和空穴迁移至表面所需要的时间,使电子和空穴复合的几率增大,从而降低了量子效率.     

Predicted formation reactions for the solid-state syntheses of the semiconductor materials Cu2SnX3 and Cu2ZnSnX4 (X = S, Se) starting from binary chalcogenides

The compounds Cu₂ZnSnX₄ and Cu₂SnX₃ (X = S or Se) are promising semiconductor materials for thin film photovoltaic applications. Based on a crystallographic growth model we derive the solid-state reactions for these four compounds starting from the binary sulphides and selenides of copper, zinc and tin. Exploiting these predicted solid-state reactions which are promoted by epitaxial relations between the educts will result in fast formation reactions as preferred in technical processes. The direct formation of Cu₂ZnSnX₄ is concurring with a two-step process in which Cu₂SnX₃ occurs as an intermediate product.     

POMs/ZrO2纳米可见光催化材料的制备及性能研究

多金属氧酸盐-氧化锆(POMs/ZrO2)复合材料是我们研制的一类具有可见光催化活性的新材料.本文结合可见光催化领域研究的最新进展,重点介绍POMs/ZrO2微孔纳米材料,包括它们的复合膜材料的制备、表征、表面物理特性、网络结构形成机理以及在可见光作用下对有机染料分子降解的光催化性能.     

Preparation and characterization of ZnO-TiO2 nanocomposite for photocatalytic disinfection of bacteria and detoxification of cyanide under visible light

ZnO-TiO₂ nanocomposite was prepared by modified ammonia-evaporation-induced synthetic method. It was characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray, UV-visible diffuse reflectance, photoluminescence and electrochemical impedance spectroscopies. Incorporation of ZnO leads to visible light absorption, larger charge transfer resistance and lower capacitance. The nanocomposite effectively catalyzes the inactivation of E. coli under visible light. Further, the prepared nanocomposite displays selective photocatalysis. While its photocatalytic efficiency to detoxify cyanide with visible light is higher than that of TiO₂ P25, its efficiency to degrade methylene blue, sunset yellow and rhodamine B dyes under UV-A light is less than that of TiO₂ P25.     

Structure and electrochemical performance of Fe3O4/graphene nanocomposite as anode material for lithium-ion batteries

Using hydrothermal method, Fe₃O₄/graphene nanocomposite is prepared by synthesizing Fe₃O₄ particles in graphene. The synthesized Fe₃O₄ is nano-sized sphere particles (100–200 nm) and uniformly distributed on the planes of graphene. Fe₃O₄/graphene nanocomposite as anode material for lithium ion batteries shows high reversible specific capacity of 771 mAh g⁻¹ at 50th cycle and good rate capability. The excellent electrochemical performance of the nanocomposite can be attributed to the high surface area and good electronic conductivity of graphene. Due to the high surface area, graphene can prevent Fe₃O₄ nanoparticles from aggregating and provide enough space to buffer the volume change during the Li insertion/extraction processes in Fe₃O₄ nanoparticles.     

氧化石墨烯/H2O2可见光催化性能影响因素

为了研究氧化石墨烯/H₂O₂可见光催化处理含难降解有机物废水影响因素,用改进的Hummers法制备了氧化石墨烯(GO),通过扫描电镜(SEM)、电子能谱(EDS)、拉曼光谱对GO的微观形貌、成分及结构进行了表征.以甲基橙(MO)为难降解有机物代表,通过改变光照、pH值以及GO的量探究了不同条件对GO/H₂O₂复合试剂降解甲基橙的光催化效果.研究表明：GO/H₂O₂复合试剂可以通过光催化产生羟基自由基降解污染物,通过改变光照、pH值及GO的量增加自由基含量可提升催化效果; 采用GO/H₂O₂复合试剂比单独使用H₂O₂在48 h内对甲基橙的降解率可提高79.09%(pH=2).用改良的Hummers法制备GO成本较低,采用GO/H₂O₂复合试剂光催化降解甲基橙时,GO用量较少,且不产生危险废弃物,为实际应用中处理难降解有机物污水提供了一个绿色环保、节能高效的思路.     

Photophysical and photocatalytic properties of novel Y2GaSbO7 and Y2YbSbO7 photocatalysts under visible light irradiation

Y₂GaSbO₇ and Y₂YbSbO₇ were synthesized by solid state reaction method for the first time. The crystallinity, composition, bandgap, morphology, and grain size of Y₂GaSbO₇ and Y₂YbSbO₇ were characterized by a series of analytical techniques. The lattice parameter a for Y₂GaSbO₇ was found to be 10.17981(1) ?, and the lattice parameters for Y₂YbSbO₇ were found to be a = 10.49741(9) ?, b = 7.45088(3) ?, c = 7.47148(7) ?, respectively. The values of band gap for Y₂GaSbO₇ and Y₂YbSbO₇ were calculated to be 2.245 and 2.521 eV, respectively. The photocatalytic degradation of rhodamine B (RhB) with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst was investigated under visible light irradiation. The results showed that Y₂GaSbO₇ and Y₂YbSbO₇ owned higher photocatalytic activity compared with Bi₂InTaO₇. Moreover, Y₂GaSbO₇ showed higher photocatalytic activity compared with Y₂YbSbO₇ for the photocatalytic degradation of RhB. The photocatalytic degradation of RhB followed the first-order reaction kinetics. The first-order rate constant, k, was 0.01817, 0.01341, and 0.00329 min⁻¹ for Y₂GaSbO₇, Y₂YbSbO₇, and Bi₂InTaO₇, respectively. Complete removal of RhB was realized after visible light irradiation for 220 or 240 min with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst. The reduction of the total organic carbon and the evolution of CO₂ were also realized and these results indicated the continuous mineralization of RhB during the photocatalytic process with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst. The possible photocatalytic degradation pathway of RhB was revealed under visible light irradiation. Methylene blue and neutral red could be degraded efficiently with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst under visible light irradiation.     

Synthesis and photocatalytic activity of nanocrystalline TiO2-SrO composite powders under visible light irradiation

Nano-sized homogeneously distributed TiO₂-20, -40, -60 wt.% SrO composite powders were successfully synthesized by a sol-gel method. The as-received amorphous TiO₂—20 wt.% SrO composite powders were crystallized with anatase TiO₂ at around 750 °C. As calcination temperatures increased, the anatase TiO₂ crystalline phase was transformed to rutile TiO₂ at about 900 °C, whereas nano-sized, squarish SrTiO₃ phase was detected. The peaks obtained after calcining at 1050 °C mainly exhibited the rutile TiO₂ and SrTiO₃ phases. However, a small number of SrO₂ peaks were also detected. For the comparison of photocatalytic activity depending on light sources, TiO₂-SrO composite powders were tested in phenol degradation. TiO₂-60 wt.% SrO composite powder showed good visible light photoactivity for the photo-oxidation of phenol.     

Photocatalytic degradation of RhB over MgFe2O4/TiO2 composite materials

MgFe₂O₄/TiO₂ (MFO/TiO₂) composite photocatalysts were successfully synthesized using a mixing-annealing method. The synthesized composites exhibited significantly higher photocatalytic activity than a naked semiconductor in the photodegradation of Rhodamine B. Under UV and visible light irradiation, the optimal percentages of doped MgFe₂O₄ (MFO) were 2 wt.% and 3 wt.%, respectively. The effects of calcination temperature on photocatalytic activity were also investigated. The origin of the high level of activity was discussed based on the results of X-ray diffraction, UV-vis diffuse reflection spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen physical adsorption. The enhanced activity of the catalysts was mainly attributed to the synergetic effect between the two semiconductors, the band potential of which matched suitably.     

Preparation of porous SnO2 helical nanotubes and SnO2 sheets

We report a surfactant-free chemical solution route for synthesizing one-dimensional porous SnO₂ helical nanotubes templated by helical carbon nanotubes and two-dimensional SnO₂ sheets templated by graphite sheets. Transmission electron microscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic discharge–charge analysis are used to characterize the SnO₂ samples. The unique nanostructure and morphology make them promising anode materials for lithium-ion batteries. Both the SnO₂ with the tubular structure and the sheet structure shows small initial irreversible capacity loss of 3.2% and 2.2%, respectively. The SnO₂ helical nanotubes show a specific discharge capacity of above 800 mAh g⁻¹ after 10 charge and discharge cycles, exceeding the theoretical capacity of 781 mAh g⁻¹ for SnO₂. The nanotubes remain a specific discharge capacity of 439 mAh g⁻¹ after 30 cycles, which is better than that of SnO₂ sheets (323 mAh g⁻¹).     

Characterization of Cu3SbS4 microflowers produced by a cyclic microwave radiation

Copper antimony sulfide (Cu₃SbS₄) crystals were produced from mixtures of different molar ratios of CuCl, SbCl₃ and thiourea in 40 and 60 ml ethylene glycol (EG) by a 300 W cyclic microwave radiation (CMR) for different lengths of time. In the present research, tetragonal Cu₃SbS₄ microflowers, characterized by X-ray and electron diffraction including electron microscopy and Raman analyses, were successfully produced in the 40 ml solution containing 2:2:4 molar ratio Cu:Sb:S for 40 cycles. Their UV-visible absorption was studied to determine the energy gap (E_g). A formation mechanism was also proposed to relate with the experimental results.     

Facile synthesis of Ag dendrites on Al foil via galvanic replacement reaction with [Ag(NH3)2]Cl for ultrasensitive SERS detecting of biomolecules

Symmetric silver dendrites have been synthesized on commercial aluminum foil via galvanic replacement reaction with [Ag(NH₃)₂]Cl. This process is facile and environmentally friendly, without the use of any templates, surfactants or oxidants, and also avoiding the introduction of fluoride anions as a strong toxicity resulting in hypocalcemia. The products were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and X-ray diffraction (XRD). SEM characterizations and electrochemical measurements including an electrochemical direct current polarization method and OCP-t technique demonstrate that chloride has proven to be the key factor to the formation of well-defined dendritic shape. The as-prepared Ag dendrites are developed as a surface-enhanced Raman scattering (SERS)-active platform for detection of folic acid, DNA and RNA with well resolved bands and high Raman intensities. The detection concentration for the three biomolecules reaches the level of 10⁻¹² M, and thus the symmetric silver dendrites can potentially be employed as effective SERS sensors for label-free and ultrasensitive biomolecule detection.     

Photoinduced charge property of nanosized perovskite-type LaFeO3 and its relationships with photocatalytic activity under visible irradiation

In this paper, ABO₃-type perovskite LaFeO₃ nanosized photocatalysts were synthesized by a sol-gel method, using citric acid (HOOCCH₂C(OH)(COOH)CH₂COOH) as complexing reagent and La(NO₃)₃·6H₂O and Fe (NO₃)₃·9H₂O as raw materials. The as-prepared samples also were characterized by several testing techniques, such as thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET), infrared spectrum (IR), ultraviolet-visible diffuse reflection spectrum (UV-vis DRS), photoluminescence spectrum (PL), surface photovoltage spectroscopy (SPS) and electrical field induced surface photovoltage spectroscopy (EFISPS). The sample activity of different LaFeO₃ nanoparticles for degrading Rhodamine B solution under visible irradiation (λ > 400 nm) was evaluated. The effects of thermal treatment temperature on photoinduced charge property and photocatalytic activity were mainly investigated, together with their relationships. The results show that the LaFeO₃ sample calcined at 500 °C exhibits higher activity, and the activity decreases with increasing calcination temperature, which is in good agreement with the characterization results. The weaker is the PL and SPS signal, the higher is the photocatalytic activity. Moreover, the activity of all as-prepared LaFeO₃ samples is higher than that of international P-25 TiO₂ under visible irradiation.     

Photocatalytic activity of Ca3Ti2O7 layered-perovskite doped with Rh under visible light irradiation

The photocatalytic activities of layered-perovskite Ca₃Ti₂O₇ doped with Rh were investigated with visible light irradiation. Although the Rh-doped Ca₃Ti₂O₇ as prepared showed low activity after an induction period, the photocatalytic activity was highly enhanced by treating the samples in reducing atmosphere without the need for an induction period. The rate of H₂ evolution from an aqueous methanol solution by 3 mol% Rh-doped Ca₃Ti₂O₇ after the reduction treatment was about 5 times higher than that before the reduction. The layered photocatalytic compounds, Ca₃Ti_2 − xRh_xO₇, showed higher stability in air than CaTi_1 − xRh_xO₃, which consists of a simple perovskite structure.     

Synthesis and photoluminescence of In2O3 nanocrystals and submicron crystals from InCl3•4H2O and thiourea

Two routes have been proposed for the synthesis of In₂O₃ powders from InCl₃•4H₂O and thiourea. One route involved a two-step procedure (that is, firstly, In₂S₃ clusters constructed with mainly nanoflakes were synthesized by heating the mixture of InCl₃•4H₂O and thiourea in air from room temperature to 200 °C, coupled with a subsequent washing treatment; secondly, In₂O₃ was obtained by calcining the In₂S₃ clusters in air at 600 °C for 6 h), and the other route was a one-step procedure (that is, In₂O₃ was synthesized directly by calcining the mixture of InCl₃•4H₂O and thiourea in air at 600 °C for 6 h). The resultant products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electronic microscope and room temperature photoluminescence (RT-PL) spectra. It was observed that the In₂O₃ nanocrystals obtained via the two-step procedure exhibited PL peaks at about 453 and 471 nm, corresponding to the defeat-related emission; while the In₂O₃ submicron polyhedral crystals obtained via the one-step procedure and In₂O₃ pyramids obtained by calcining the only InCl₃•4H₂O in air at 600 °C for 6 h displayed a PL band centered at around 338 nm, corresponding to the band edge emission.