Layer-by-layer self-assembly polytungstogermanate multilayer films and their photocatalytic properties under sunlight irradiation

Seven different types of thio- and/or amine-modified cellulose resin materials were synthesized and their mercury (II) ion adsorption properties determined. All seven resins showed good mercury (II) adsorption capability in the more neutral pH regions. However, the o-benzenedithiol- and o-aminothiophenol-modified cellulosic resins were found to be very effective in removing mercury (II) ions from strongly acidic media. For example, 93.5-100% mercury (II) ion recoveries from very acid aqueous solutions (nitric acid concentration ranged from 0.1 to 2.0 mol/L) were obtained using the o-benzenedithiol-modified resin while recoveries ranged from ca. 50% to 60% for the o-aminothiophenol-modified resin. An adsorption capacity of 23 mg (as Hg atoms) per gram of resin was observed for the o-benzenedithiol-modified cellulose in the presence of 1.0 mol/L nitric acid. This same resin shows very good selectivity for mercury (II) as only ruthenium (II) also somewhat adsorbed onto it out of 14 other metal ions studied (Ag(+), Al(3+), As(3+), Co(2+), Cd(2+), Cr(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), Pt(2+), Pb(2+), Ru(2+), and Zn(2+)).     

Synthesis and optical properties of self-assembled flower-like CdS architectures by mixed solvothermal process

Self-assembled CdS architectures with flower-like structures have been synthesized by a mixed solvothermal method using ethylene glycol and oleic acid as the mixed solvent at 160°C for 12 h. The results of X-ray diffraction (XRD) patterns, field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images indicate that the product exists as the hexagonal wurtzite phase and conatins of larger numbers of flower-like CdS architectures with diameters of 1.8–3 μm. The selected-area electron diffraction (SAED) pattern and the high resolution transmission electron microscope (HRTEM) image reveal that the grain has better crystallinity. The optical properties of flower-like CdS architectures were also investigated by ultraviolet-visable (UV-vis) and photoluminescence spectroscopy at room temperature. A strong peak at 490 nm is shown in the UV-vis absorption, while an emission at 486 nm and another strong emission at 712 nm are shown in the PL spectrum.      

Efficient photocatalytic degradation of rhodamine-B by Fe doped CuS diluted magnetic semiconductor nanoparticles under the simulated sunlight irradiation

The present work is planned for a simple, inexpensive and efficient approach for the synthesis of Cu_1-xFe_xS (x = 0.00, 0.01, 0.03, 0.05 and 0.07) nanoparticles via simplistic chemical co-precipitation route by using ethylene diamine tetra acetic acid (EDTA) as a capping molecules. As synthesized nanoparticles were used as competent catalysts for degradation of rhodamine-B organic dye pollutant. The properties of prepared samples were analyzed with energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible optical absorption spectroscopy, Fourier transform infrared (FTIR) spectra, Raman spectra and vibrating sample magnetometer (VSM). EDAX spectra corroborated the existence of Fe in prepared nanoparticles within close proximity to stoichiometric ratio. XRD, FTIR and Raman patterns affirmed that configuration of single phase hexagonal crystal structure as that of (P6₃/mmc) CuS, without impurity crystals. The average particle size estimated by TEM scrutiny is in the assortment of 5–10 nm. UV-visible optical absorption measurements showed that band gap narrowing with increasing the Fe doping concentration. VSM measurements revealed that 3% Fe doped CuS nanoparticles exhibited strong ferromagnetism at room temperature and changeover of magnetic signs from ferromagnetic to the paramagnetic nature with increasing the Fe doping concentration in CuS host lattice. Among all Fe doped CuS nanoparticles, 3% Fe inclusion CuS sample shows better photocatalytic performance in decomposition of RhB compared with the pristine CuS. Thus as synthesized Cu_0·97Fe_0·03S nanocatalysts are tremendously realistic compounds for photocatalytic fictionalization in the direction of organic dye degradation under visible light.     

原位合成具有高可见光催化活性的C3N4/CdS纳米复合材料

以硫氰酸铵和氯化镉为原料,采用无模板混合高温煅烧法一步合成氮化碳/硫化镉纳米晶(C3N4/CdS)的复合半导体材料。采用X射线衍射、傅立叶变换红外光谱和透射电镜等技术对其结构和形貌进行了表征。以有机污染物罗丹明B (RhB)为模拟污染物对复合催化剂的可见光催化活性进行测试。结果表明, C3N4/CdS复合材料中CdS以六方相纳米晶的形式均匀分散; CdS的复合基本不改变C3N4主体结构及聚合度;与纯C3N4相比,复合材料在可见区的光吸收能力有所增强。合适的能带匹配有利于光生载流子的迁移,抑制了其复合速率。在可见光照射下,复合半导体能够更加快速的降解有机污染物,且保持很好的稳定性。     

原位合成具有高可见光催化活性的C3N4/CdS纳米复合材料

以硫氰酸铵和氯化镉为原料,采用无模板混合高温煅烧法一步合成氮化碳/硫化镉纳米晶(C3N4/CdS)的复合半导体材料。采用X射线衍射、傅立叶变换红外光谱和透射电镜等技术对其结构和形貌进行了表征。以有机污染物罗丹明B (RhB)为模拟污染物对复合催化剂的可见光催化活性进行测试。结果表明, C3N4/CdS复合材料中CdS以六方相纳米晶的形式均匀分散; CdS的复合基本不改变C3N4主体结构及聚合度;与纯C3N4相比,复合材料在可见区的光吸收能力有所增强。合适的能带匹配有利于光生载流子的迁移,抑制了其复合速率。在可见光照射下,复合半导体能够更加快速的降解有机污染物,且保持很好的稳定性。     

Facile solvothermal synthesis of highly active monoclinic scheelite BiVO4 for photocatalytic degradation of methylene blue under white LED light irradiation

In this study, BiVO₄ was successfully synthesized via the solvothermal process using a solvent mixture of ethylene glycol and water under different synthesis conditions of temperature and pH. Physicochemical properties such as crystal phase, morphology, and optical absorption of the as-synthesized BiVO₄ samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible diffraction reflection spectroscopy (UV–vis DRS). The XRD analysis showed that different synthesis conditions of temperature and pH significantly affected the growth of monoclinic BiVO₄ crystals oriented along (0 4 0) facets. Form SEM results, the synthesis conditions, including pH and temperature, have a great effect on the morphology of monoclinic structured BiVO₄. As the pH value increases in the range of 0–9 and temperature increases from 80 °C to 180 °C, the morphology of BiVO₄ changed from peanut-, rod-, and leaf-like shapes. The photocatalytic activities of as-synthesized BiVO₄ photocatalysts were evaluated by the photodegradation of methylene blue (MB) dye under irradiation of white LED light. We have found that by using appropriate synthesis conditions (the synthesis temperature of 140 °C and the synthesis pH of 7) the BiVO₄ exhibited high photocatalytic efficiency for MB degradation (about 82.30% after 180 min of irradiation). This result is due to the development of the BiVO₄ crystals oriented along (0 4 0) facets with an increase in the intensity ratio of I_(0 4 0)/I_(1 2 1). The growth of BiVO₄ crystals oriented along (0 4 0) facets may be beneficial to enhance the photocatalytic activity of monoclinic scheelite BiVO₄.     

TiO2 nanotube/ZnO nanorod/CdS on Ti mesh with three-dimensional array structure for photocatalytic degradation under visible light irradiation

Research on Chemical Intermediates - The three-dimensional (3D) TiO2 nanotube arrays (TNTA) were prepared by electrochemical anodization of Ti mesh in a mixed electrolyte solution of (NH4)2SO4 and...     

Studies on optical absorption and structural properties of Fe doped CdS quantum dots

Fe doped CdS quantum dots have been prepared using simple precursors by chemical precipitation technique. Fe doped CdS quantum dots have been synthesized by mixing cadmium nitrate, sodium sulfide and adding Fe under suitable conditions. X-ray diffraction analysis reveals that undoped and Fe doped CdS crystallizes in hexagonal structure. The lattice constants of Fe doped CdS nanoparticles decreased slightly with incorporation of Fe and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.8–4.2 nm. HRTEM results show that undoped and 3.75% Fe doped CdS nanoparticles exhibit a uniform size distribution and average size of the nanoparticles is about 2–3 nm. Raman spectra show that 1LO and 2LO peaks of the Fe doped CdS samples are slightly red shifted compared with those of undoped CdS. Optical absorption spectra of Fe doped CdS nanoparticles exhibited red shift.     

Facile preparation of BiVO4 thin film by screen-printing technique for its photocatalytic performance in the degradation of tetracycline under simulated sunlight irradiation

BiVO₄ films were prepared by a screen-printing technique on Corning glass substrate. The material employed to prepare the films was synthetized by the hydrothermal method. For comparative purposes, the BiVO₄ was synthesized via solid state reaction and deposited in film form by the same technique. From the X-ray diffraction structural characterization it has been stated that BiVO₄ films crystallized in the monoclinic structure. The characterization of BiVO₄ films was complemented with scanning electron microscopy, which revealed a morphology of irregular form and dendritic type depending on the starting material. The thickness of the BiVO₄ films were determined by profilometry. The film obtained from the hydrothermal method showed minor photoluminescence, i.e., the sample showed low recombination of electron–hole pairs. The highest photocatalytic activity in the degradation of tetracycline (TC) was presented for the BiVO₄ films obtained from hydrothermal powders under simulated sunlight irradiation; attributed mainly to the surface area value, smaller particle size and lower recombination of electron–hole pairs. Mineralization degree of TC by BiVO₄ films was determined by the total organic carbon analysis, reaching 50% after 24 h of irradiation. The main oxidizing species that was most influenced in the degradation of TC was the hydroxyl radical (OH^·).

     

Biosynthesis of zinc oxide nanoparticles using Euphorbia milii leaf constituents: Characterization and improved photocatalytic degradation of methylene blue dye under natural sunlight

A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m²/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm³/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm^?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.     

Effect of the cadmium ion source on the structural and optical properties of chemical bath deposited CdS thin films

The chemical bath deposition (CBD) technique has been successfully used to deposit cadmium sulphide from cadmium chloride and cadmium acetate as the cadmium ion source and thiourea as the sulphur source on both glass microscope slide and indium tin oxide coated glass substrates. Various properties of the films such as surface morphology, crystallinity, optical properties and resistivitiy have been investigated. XRD patterns reveal that the CdS films deposited from cadmium chloride have an hexagonal structure. Their preferential orientation changes from (002) to (100) with the thermal annealing. Films deposited from cadmium acetate are amorphous but improve their crystallinity with annealing. SEM analysis shows that the grains of the as deposited films are randomly shaped and appear to be bigger in the case of the CdS prepared from cadmium chloride. The optical transmission of the layers are in the 70–80 % range for wavelength above the band gap absorption which makes them more appropriate as window material in heterojunction solar cells.     

Microwave-assisted preparation and enhanced photocatalytic activity of Bi2WO6/BiOI heterojunction for organic pollutants degradation under visible-light irradiation

In this research, we adopted morphology control and constructing p-n heterojunction to boost the photocatalytic performance of BiOI. BiOI with three morphologies (nanoplate, micro-flower, microsphere) was fabricated via a wet-chemical method at room temperature using different solvents. And Bi₂WO₆/BiOI microspheres were successfully prepared by a microwave-assisted synthetic method. The as-synthesized samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS) and High-resolution Transmission Electron Microscopy (HRTEM). The results of photo-degradation experiment demonstrated that BiOI-3 and BWOI-3 show high photocatalytic performance towards methyl orange (MO) and bisphenol A (BPA) degradation due to the high specific surface area, synergistic effect between p-type BiOI and n-type Bi₂WO₆ and high separation efficiency of electron-hole pairs, which is verified by Brunauer-Emmett-Teller (BET), Photocurrent (PC) and Electrochemical Impedance Spectroscopy (EIS) analysis. Moreover, the repeated photocatalytic experiment was carried out by using MO as the representative organic pollutant, manifesting the good durability of the sample.     

Architectural control syntheses of CdS and CdSe nanoflowers, branched nanowires, and nanotrees via a solvothermal approach in a mixed solution and their photocatalytic property

Wurtzite CdS and CdSe nanostructures with complex morphologies such as urchin-like CdS nanoflowers, branched nanowires, and fractal nanotrees can be produced via a facile solvothermal approach in a mixed solution made of diethylenetriamine (DETA) and deionized water (DIW). The morphologies of CdS and CdSe nanocrystals can be easily controlled via tuning the volume ratio of DETA and DIW. Urchin-like CdS nanoflowers made of CdS nanorods are in a form of highly ordered hierarchical structures, while the nanowires are branched nanowires, and the fractal CdS nanotrees are a buildup of branched nanopines. The results demonstrated that solvothermal reaction in a mixed amine/water can access a variety of complex morphologies of semiconductor materials. The photocatalytic activity of CdS particles with different morphologies has been tested by the degradation of acid fuchsine under both UV and visible light, showing that the as-prepared branched CdS nanowires exhibit high photocatalytic activity for degradation of acid fuchsine.     

A simple solvothermal route towards the morphological control of ZnO and tuning of its optical and photocatalytic properties

ZnO nanoparticles with different morphologies were solvothermally synthesized by controlling the alkali (sodium hydroxide) concentration in an isopropanol solution. The products were characterized by means of powder X-ray diffraction, UV-visible absorption spectra, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The morphologies of the formed ZnO nanocrystals were dependent on the concentration of the alkali, and with increases of sodium hydroxide concentration, the ZnO nanocrystals evolved from rod to hexagonal bipyramid, and then to a flower-like nanostructure. The flower-like nanostructure resulted from the etching of the hexagonal bipyramid by the excess alkali. The photoluminescence and photocatalytic properties of the prepared ZnO were investigated. The difference of green emission among the ZnO nanocrystals indicated that a higher sodium hydroxide concentration led to a higher level of defects. The size, the surface structure and defects in the ZnO nanocrystals affected its photo-degradation characteristics.     

溶剂对BiOBr结构和光催化降解RhB的影响

以水热法合成了不同形貌的BiOBr样品.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附脱附曲线和紫外可见漫反射光谱(UV-Vis DRS)研究溶剂对BiOBr样品的晶形、形貌、孔径分布和比表面积、光学性质的影响;以罗丹明B(RhB)为目标降解物,研究溶剂对BiOBr的可见光催化性能的影响.实验结果表明,采用EG为溶剂的BiOBr在可见光降解RhB中表现出最佳的降解效果,因其较采用HNO_3、GL和PVP为溶剂的样品具有更高I_((001))/I_((102)),更小的禁带宽度和更均一的纳米片形貌.此外,阐述了溶剂对光催化降解RhB的影响机理.     

太阳光下高光催化活性Pr-N-P三元掺杂锐钛矿TiO2纳米片

利用溶胶-凝胶和溶剂热联合技术制备了Pr-N-P三元掺杂锐钛矿TiO₂（PrNPTO）纳米片,并采用X射线衍射、透射电镜、N₂吸附、X射线光电子能谱、UV-vis吸收谱和光致荧光光谱分析技术对其进行了表征.当Pr掺杂量为1.75wt%,焙烧温度为550℃时,制得的PrNPTO在可见和紫外光下光催化降解亚甲基蓝（MB）活性最佳.在模拟太阳光照射下,PrNPTO也表现出优越的光催化降解4-氯酚性能（k_app=3.90×10^-2min^-1）,优于未掺杂、单掺杂和双掺杂TiO₂样品,其光活性是P25TiO₂的3.33倍（k_app=1.17×10^-2min^-1）.PrNPTO光活性的提高归因于Pr-N-P三元掺杂增强了紫外和可见光吸收,降低了光生载流子复合,增加了表面羟基以及改善了表面织构特性.在模拟太阳光照射下,PrNPTO光催化效率高且光催化性能稳定,适合于环境净化领域的实际应用.     

Solvothermal synthesis of uniform and high aspect ratio of CdS nanowires and their optical properties

Uniform and high aspect ratio CdS nanowires (NWs) were successfully synthesized by the solvothermal reaction of the solution containing Cd(NO₃)₂, (NH₄)₂S and ethylenediamine (NH₂(CH₂)₂NH₂). In this research, the effects of molar contents of the stating materials, reaction temperatures and lengths of time on phase, vibration modes, morphologies, and optical properties of the as-synthesized products were studied using XRD, Raman spectroscopy, SEM, TEM, SAED, HRTEM, UV–vis spectroscopy and PL spectroscopy. They were found to be controlled by the contents of the stating materials, reaction temperatures and lengths of time. Mixed nanoparticles and short nanorods of CdS were synthesized by the 200 °C and 24 h solvothermal reaction of the solutions containing 0.0001–0.0050 mol of the starting materials. Upon increasing the content of the starting materials to 0.0100 mol, the completely uniform CdS NWs with aspect ratio of >250 were synthesized.     

Photophysical properties and photocatalytic activities of bismuth molybdates under visible light irradiation

Aurivillius structure Bi(2)MoO(6) (BG: 2.70 eV) that is a low-temperature phase showed an intense absorption band in the visible light region and photocatalytic activity for O(2) evolution from an aqueous silver nitrate solution under visible light irradiation, among various bismuth molybdates (Bi(2)MoO(6), Bi(2)Mo(2)O(9), and Bi(2)Mo(3)O(12)) synthesized by solid-state and reflux reactions. Bi(2)Mo(3)O(12) (BG: 2.88 eV) also showed photocatalytic activity for O(2) evolution under full-arc irradiation of a Xe lamp (lambda > 300 nm). The photocatalytic activity of the Aurivillius structure Bi(2)MoO(6) prepared by the reflux method was dependent on the annealing temperature after the preparation. The crystallinity was the important factor for the activity. Calculation by the density functional method indicated that the conduction band of Aurivillius structure Bi(2)MoO(6) was made up of Mo 4d orbitals. It turned out that the visible-light absorption of this photocatalyst was due to the transition from the valence band consisting of O 2p orbitals to the conduction band. The corner-sharing structure of the MoO(6) octahedra contributed to the visible light response and the photocatalytic performance because excitation energy and/or photogenerated electron and hole pairs began to migrate easily in the Aurivillius structure.     

Enhancement of photocatalytic H2 evolution on CdS by loading MoS2 as Cocatalyst under visible light irradiation

This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.