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1.
Au core Ag shell composite structure nanoparticles were prepared using a sol method. The Au core Ag shell composite nanoparticles were loaded on TiO 2 nanoparticles as support using a modified powder–sol method, enabling the generation of Au @ Ag/TiO 2 photocatalysts for photocatalytic decomposition and elimination of ozone. The sols were characterized by means of ultraviolet–visible light (UV–Vis) reflection spectrometry, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The activity of the Au @ Ag/TiO 2 photocatalysts for photocatalytic decomposition and elimination of ozone was evaluated and the effect of Cl ? anions on the photocatalytic activity of the catalysts was highlighted. Results showed that Au @ Ag/TiO 2 prepared via the modified powder–sol route in the presence of an appropriate amount of NaCl solid as demulsifier had better activity in the photocatalytic decomposition and elimination of ozone. At the same time, Au @ Ag/TiO 2 catalysts had better ability to resist poisonous Cl ? anions than conventional Au/TiO 2 catalyst. The reasons could be, first, that NaCl was capable of reducing the concentration of free Ag + by adsorption on the surface of Ag particles forming AgCl and enhancing the formation of Au core Ag shell particles, leading to a better resistance to Cl ? anions of the catalysts, and, second, AgCl took part in the photocatalytic decomposition of ozone together with Au @ Ag/TiO 2 catalysts and had a synergistic effect on the latter, resulting in better photocatalytic activity of Au @ Ag/TiO 2 catalysts. 相似文献
2.
Novel multielement Au/La‐SrTiO 3 microspheres were synthesized by a solvothermal method using monodisperse gold and La‐SrTiO 3 nanocrystals as building blocks. The porous Au/La‐SrTiO 3 microspheres had a large surface area of 94.6 m 2 g ?1. The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare‐earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La‐SrTiO 3 microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La‐SrTiO 3 microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine B. The photocatalytic activities are in the order of the following: Au/La‐SrTiO 3 microspheres>Au/SrTiO 3 microspheres>La‐SrTiO 3 microspheres>SrTiO 3 microspheres. 相似文献
3.
Constructing hollow multi‐shelled structures (HoMSs) has a significant effect on promoting light absorption property of catalysts and enhancing their performance in solar energy conversion applications. A facile hydrothermal method is used to design the SrTiO 3?TiO 2 heterogeneous HoMSs by hydrothermal crystallization of SrTiO 3 on the surface of the TiO 2 HoMSs, which will realize a full coverage of SrTiO 3 on the TiO 2 surface and construct the SrTiO 3/TiO 2 junctions. The broccoli‐like SrTiO 3?TiO 2 heterogeneous HoMSs exhibited a fourfold higher overall water splitting performance of 10.6 μmol h ?1 for H 2 production and 5.1 μmol h ?1 for O 2 evolution than that of SrTiO 3 nanoparticles and the apparent quantum efficiency (AQE) of 8.6 % at 365 nm, which can be mainly attributed to 1) HoMS increased the light absorption ability of the constructed photocatalysts and 2) the SrTiO 3?TiO 2 junctions boosted the separation efficiency of the photogenerated charge carriers. 相似文献
4.
In this study, the photocatalytic efficiency of anatase‐type TiO 2 nanoparticles synthesized using the sol–gel low‐temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV–light‐assisted photo and NaBH 4‐assisted chemical reduction methods were used for deposition of copper onto TiO 2. The surface hydroxyl groups of TiO 2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed‐bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH‐modified Cu/TiO 2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO 2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO 2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH 4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH‐modified Cu/TiO 2 nanoparticles. 相似文献
5.
Multicomponent Cu? Cu 2O? TiO 2 nanojunction systems were successfully synthesized by a mild chemical process, and their structure and composition were thoroughly analyzed by X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy, and X‐ray photoelectron spectroscopy. The as‐prepared Cu? Cu 2O? TiO 2 (3 and 9 h) nanojunctions demonstrated higher photocatalytic activities under UV/Vis light irradiation in the process of the degradation of organic compounds than those of the Cu? Cu 2O, Cu? TiO 2, and Cu 2O? TiO 2 starting materials. Moreover, time‐resolved photoluminescence spectra demonstrated that the quenching times of electrons and holes in Cu? Cu 2O? TiO 2 (3 h) is higher than that of Cu? Cu 2O? TiO 2 (9 h); this leads to a better photocatalytic performance of Cu? Cu 2O? TiO 2 (3 h). The improvement in photodegradation activity and electron–hole separation of Cu? Cu 2O? TiO 2 (3 h) can be ascribed to the rational coupling of components and dimensional control. Meanwhile, an unusual electron–hole transmission pathway for photocatalytic reactions over Cu? Cu 2O? TiO 2 nanojunctions was also identified. 相似文献
6.
The activation of Au–Ag plasmonic bimetallic nanocatalyst can make the nanocatalyst exhibit superior visible-light (VL) photocatalytic activity. An efficient activation of Au–Ag nanocatalyst by cold plasma requires the restructuring of Au and Ag species over catalyst surface to form Au–Ag alloy nanoparticles while suppressing agglomeration of the nanoparticles. We here report that the loading sequence of Au and Ag components on titanium dioxide (TiO2) support during catalyst preparation and discharge atmosphere play important roles in the plasma activation. Preparation of AuAg/TiO2 nanocatalyst by depositing Ag and Au in sequence could avoid the undesired loss of Ag component, and ensure an effective restructuring of Au and Ag species in O2 plasma activation. Compared with the reductive (H2) and inert (Ar and N2) plasmas, discharge in oxidative O2 establishes Coulomb field with the negatively charged species over catalyst surface and enable the restructuring and intimate interaction of Au and Ag species. The catalyst characterization and density functional theory calculations suggest that O2 plasma endows AuAg/TiO2 nanocatalyst with large numbers of Au–Ag alloy nanoparticles, small size of plasmonic nanoparticles, high density of coordinatively unsaturated sites, and high content of surface oxygen species in the activation, which facilitates the adsorption and activation of O2, and thus CO oxidation reaction under VL irradiation. 相似文献
7.
In the context of gaining understanding on the origin of the visible‐light photoresponse of TiO 2 containing gold nanoparticles, the photocurrent spectra and photocatalytic H 2 evolution of titania (P25) and Au–P25 were compared. Whereas no photocurrent was detected upon visible‐light irradiation for either of the two photocatalysts, Au–P25 exhibited photocatalytic H 2 evolution for wavelengths between 400 and 575 nm. This contradictory behavior under visible‐light irradiation of Au–P25 was rationalized by transient absorption spectroscopy. It was suggested that photocatalytic H 2 generation results from methanol quenching of the charge‐separation state in each semiconductor nanoparticle, but the lack of photocurrent is due to the short lifetime of the charge separation, which makes interparticle charge migration for micrometric distances unlikely. 相似文献
8.
提出了通过TiO 2表面修饰纳米Au的方法来提高纳米TiO 2光催化杀伤癌细胞的效率. 采用化学还原法合成了Au改性的TiO 2 (Au/TiO 2)纳米复合物, 并研究了不同掺杂量(1 wt%, 2 wt%, 4 wt%)的Au/TiO 2对人结肠癌LoVo细胞的光催化杀伤效应. 结果显示, Au的掺杂大大地提高了TiO 2纳米粒子光催化杀伤结肠癌LoVo细胞的效率, 而且Au掺杂量的高低影响Au/TiO 2光催化杀伤癌细胞的效率, 掺金量为2%的Au/TiO 2对结肠癌LoVo细胞具有最高的光催化杀伤效率. 在光强为1.8 mW/cm 2的紫外灯( λmax=365 nm)下光照110 min, 50 μg/mL掺金量为2%的Au/TiO 2能够杀死所有的癌细胞, 而同样浓度的TiO 2只能杀死70%的癌细胞. 相似文献
9.
SrTiO 3 nanofibers were successfully prepared by a facile electrospinning method with subsequent calcination in air. These one dimensional nanostructures were characterized for the morphological, structural and optical properties by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. The photocatalytic investigations showed that the SrTiO 3 nanofibers possessed enhanced photocatalytic efficiency in photodegradation of rhodamine B and photocatalytic H 2 evolution from water splitting under ultraviolet light irradiation, compared with the SrTiO 3 nanoparticles and P25. The enhanced photocatalytic performance can be ascribed to the beneficial microstructure and more negative conduction band edge compared with P25. 相似文献
10.
5‐Mono‐(2‐thienyl)‐10,15,20‐triphenyl porphyrin (H 2MTP) and its Co(II), Cu(II), Zn(II) metalloporphyrins (CoMTP, CuMTP, ZnMTP) were synthesized and characterized spectroscopically. The corresponding Co(II), Cu(II), Zn(II) metalloporphyrins‐TiO 2 photocatalysts were then prepared and characterized by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), UV‐vis spectra and FT‐IR. The photocatalytic activities of these photocatalysts were investigated by testing the photodegradation of 4‐nitrophenol (4‐NP) in aqueous solution under irradiation with high‐pressure mercury lamp and metal halide lamp respectively. The results indicated that these metalloporphyrins greatly enhanced the photocatalytic efficiency of bare TiO 2 in degradating the 4‐NP, and CuMTP‐TiO 2 exhibited the highest photocatalytic activity of all photocatalysts. In addition, the first order rate constants of these photocatalytic reactions were calculated. 相似文献
11.
The increasing incidence of cancer all over the world demands new, effective and secure materials for treatment. In this paper, we propose Pt/TiO 2 nanocomposite for cancer-cell treatment because noble metal nanoparticles are supposed to enhance the photocatalytic activity of TiO 2 nanoparticles. To evaluate the cancer-cell killing effect of our Pt/TiO 2 nanocomposite, TiO 2 and Au/TiO 2 nanoparticles are also introduced. The prepared Pt/TiO 2 nanocomposite are characterized with transmission electron microscopy (TEM) and UV–vis adsorption spectra. Results of cell treatment indicate that Pt/TiO 2 nanocomposite, as extremely stable metal–semiconductor nanomaterial, can exhibit a very high photodynamic efficiency under a mild ultraviolet radiation. And our Pt/TiO 2 nanocomposite shows to be more effective in cancer-cell treatment than TiO 2 and Au/TiO 2 nanoparticles. As a result, Pt/TiO 2 nanocomposite may be supposed to have a promising application for cancer-cell treatment. 相似文献
12.
Gold (Au) plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride (g-C 3N 4) nanosheets via a facile oil-bath method. The photocatalytic activity of the Au/monolayer g-C 3N 4 composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment. All of the Au/monolayer g-C 3N 4 composites showed better photocatalytic performance than that of monolayer g-C 3N 4 and the 1% Au/monolayer g-C 3N 4 composite displayed the highest photocatalytic hydrogen evolution rate of the samples. The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles, which led to the surface plasmon resonance (SPR) effect. The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process. The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g-C 3N 4. Thus, the Au/monolayer g-C 3N 4 composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron-hole pairs than those of monolayer g-C 3N 4. A photocatalytic mechanism for the composites was also proposed. 相似文献
13.
使用L-半胱氨酸作为连接剂, 利用硼氢化钠原位还原预先吸附在介孔氧化亚铜表面的氯金酸根离子,得到了Au/Cu 2O异质结构. 应用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱和N 2物理吸附等手段对催化剂进行表征, 并以λ>400 nm的可见光作为光源, 评价了该催化剂光催化降解亚甲基蓝(MB)的活性. 实验结果表明, 直径为4 nm的金颗粒完好地负载在介孔氧化亚铜的表面, 并且介孔氧化亚铜的细微结构与孔径均未发生变化. 研究表明, 以乙醇作为反应溶剂有效抑制了AuCl 4-与Cu 2O之间的氧化还原反应, 从而有利于氧化亚铜介孔结构的保持及金颗粒的原位还原. 光催化降解亚甲基蓝的结果表明, Au/Cu 2O异质结构的光催化活性比纯氧化亚铜光催化活性有明显提高. 推测其光催化性能提高的主要原因如下: 一方面, 金颗粒良好的导电性有利于氧化亚铜表面电子的快速转移, 实现电子-空穴分离; 另一方面, 金颗粒可能存在的表面等离子共振现象加速了光生电子的产生. 相似文献
14.
Charge separation plays a key role in the conversion of solar energy into chemical energy for use in the redox reaction and as well as in the photocatalytic activity. In this study, SrTiO 3 particles with different morphologies including irregular, tetrahexahedron, and cube were synthesized by an in situ solvothermal method. The photocatalytic activity of the synthesized nanoparticles was investigated in the photocatalytic decomposition of methylene blue under UV light irradiation. Tetrahexahedron SrTiO 3 particles exhibited high decomposition activity (70 %), which is about two times higher than those of the irregular and cubic SrTiO 3 particles. The high decomposition activity of tetrahexahedron SrTiO 3 particles could be attributed to the improvement of charge separation achieved on different crystal facets. To reach a good charge separation, tetrahexahedron SrTiO 3/TiO 2 coupled nanoparticles were fabricated by impregnation method. Results showed that coupling tetrahexahedron SrTiO 3 with TiO 2 could produce efficient charge separation between tetrahexahedron SrTiO 3 and TiO 2 due to their matched band edges. In order to achieve better charge separation, the tetrahexahedron SrTiO 3/90 %TiO 2 sample was calcined at different temperatures in the 450–750 °C range. Tetrahexahedron SrTiO 3/90 %TiO 2 coupled nanoparticles calcined at 650 °C show high photocatalytic activity compared with other samples. The prepared samples were characterized by using various techniques such as X-ray diffraction, scanning electron microscopy, photoluminescence emission spectra, and UV–Vis diffuse reflectance spectroscopy. 相似文献
15.
The synthesis of Zn‐doped TiO 2 nanoparticles by solgel method was investigated in this study, as well as its modification by H 2O 2. The catalyst was characterized by transmission electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller, UV–visible reflectance spectra and X‐ray photoelectron spectroscopy (XPS). The results indicated that doping Zn into TiO 2 nanoparticles could inhibit the transformation from anatase phase to rutile phase. Zn existed as the second valence oxidation state in the Zn‐doped TiO 2. Zn‐doped TiO 2 that was synthesized by 5% Zn doping at 450°C exhibited the best photocatalytic activity. Then, the H 2O 2 modification further enhanced the photocatalytic activity. Zn doping and H 2O 2 modifying narrowed the band gap and efficiently increased the optical absorption in visible region. The optimal degradation rate of tetracycline by Zn‐doped TiO 2 and H 2O 2 modified Zn‐doped TiO 2 was 85.27% and 88.14%. Peroxide groups were detected in XPS analysis of H 2O 2 modified Zn‐doped TiO 2, favoring the adsorption of visible light. Furthermore, Zn‐doped TiO 2 modified by H 2O 2 had relatively good reusability, exhibiting a potential practical application for tetracycline's photocatalytic degradation. 相似文献
16.
Great strides have been made in enhancing solar energy conversion by utilizing plasmonic nanostructures in semiconductors. However, current generation with plasmonic nanostructures is still somewhat inefficient owing to the ultrafast decay of plasmon‐induced hot electrons. It is now shown that the ultrafast decay of hot electrons across Au nanoparticles can be significantly reduced by strong coupling with CdS quantum dots and by a Schottky junction with perovskite SrTiO 3 nanoparticles. The designed plasmonic nanostructure with three distinct components enables a hot‐electron‐assisted energy cascade for electron transfer, CdS→Au→SrTiO 3, as demonstrated by steady‐state and time‐resolved photoluminescence spectroscopy. Consequently, hot‐electron transfer enabled the efficient production of H 2 from water as well as significant electron harvesting under irradiation with visible light of various wavelengths. These findings provide a new approach for overcoming the low efficiency that is typically associated with plasmonic nanostructures. 相似文献
17.
A facile approach has been developed for the preparation of various morphologies of Au–Ag 2Te nanomaterials (NMs) that exhibit strong photocatalytic activity. Te NMs (nanowires, nanopencils, and nanorice) were prepared from TeO 2 in the presence of various concentrations (16, 8, and 4 M ) of a reducing agent (N 2H 4) at different temperatures (25 and 60 °C). These three Te NMs were then used to prepare Au–Ag 2Te NMs by spontaneous redox reactions with Au 3+ and Ag + ions sequentially. The Au–Ag 2Te nanopencils exhibit the highest activity toward degradation of methylene blue and formation of active hydroxyl radicals on solar irradiation, mainly because they absorb light in the visible region most strongly. All three differently shaped Au–Ag 2Te NMs (10 μg mL ?1) provide a death rate of Escherichia coli greater than 80 % within 60 min, which is higher than that of 51 % for commercial TiO 2 nanoparticles (100 μg mL ?1). Under light irradiation, the Au NPs in Au–Ag 2Te NMs enhance the overall photo‐oxidation ability of Ag 2Te NMs through faster charge separation because of good contact between Ag 2Te and Au segments. With high antibacterial activity and low toxicity toward normal cells, the Au–Ag 2Te NMs hold great potential for use as efficient antibacterial agents. 相似文献
18.
SnO 2–TiO 2/fly ash cenospheres (FAC) were prepared via hydrothermal method and used as an active photocatalyst in a photocatalytic system. Scanning electron microscopy, X‐ray diffraction analysis, UV–Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and N 2 adsorption–desorption measurements were used to determine the structure and optical property of SnO 2–TiO 2/FAC. Phenol was selected as the model substance for photocatalytic reactions to evaluate catalytic ability. Results showed that the degradation efficiency of phenol by SnO 2–TiO 2/FAC was 90.7% higher than that decomposed by TiO 2/FAC. Increased efficiency could be due to the enhanced synergistic effect of semiconductors and FAC could provide more adsorption sites for the pollutant in the photocatalytic reaction. Furthermore, SnO 2–TiO 2/FAC composites exhibited excellent photocatalytic stability in four reuse cycles. Radical‐trapping experiments further revealed the dominating functions of holes in the photocatalytic reaction. 相似文献
19.
A simple and practical technique to synthesize nanosized platinum particles loaded on TiO 2 (Pt–TiO 2) by using a microwave (Mw)‐assisted deposition method has been exploited in the development of a highly efficient photocatalyst for the formation of H 2 and N 2 gases from harmful nitrogen‐containing chemical wastes, for example, aqueous ammonia (NH 3). Upon Mw irradiation, a platinum precursor can be deposited quickly on the TiO 2 surface from an aqueous solution of platinum and subsequent reduction with H 2 affords the nanosized platinum metal particles with a narrow size distribution (Mw‐Pt–TiO 2). Characterization by CO adsorption, platinum L III‐edge X‐ray absorption fine structure analysis, and TEM analysis revealed that the size of the metal nanoparticles strongly depended on the preparation methods. Smaller platinum nanoparticles were obtained by the Mw heating method than those obtained by conventional preparation techniques, such as photoassisted deposition (PAD), impregnation (Imp), and equilibrium adsorption (EA) deposition by conventional convective heating. The H 2 and N 2 formation rates increased with increasing dispersity of platinum. Pt–TiO 2 prepared by the Mw heating method exhibited a specifically high H 2 formation activity in the photocatalytic decomposition of aqueous NH 3 in a nearly stoichiometric 3:1 (H 2/N 2) molar ratio under inert conditions. The present Mw heating method is applicable to a variety of anatase‐type TiO 2 species possessing different specific surface areas to provide small and highly dispersed platinum nanoparticles with a narrow size distribution. 相似文献
20.
Au/TiO 2/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO 2 and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e ?/ h + pairs. Under UV irradiation, photogenerated electrons of TiO 2 are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO 2 and then transfer further to graphene sheets. As a result, compared with pure TiO 2, Au/TiO 2/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO 2, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules. 相似文献
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