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In this work, CdS nanoparticles embedded in alumina matrix were successfully synthesized using layered double hydroxides (LDHs) as precursor and template, denoted as CdSLDH. The as prepared CdSLDH were characterized by XRD, UV-Vis DRS, TEM, HRTEM, XPS, PL and time resolved fluorescence spectra. The photocatalytic hydrogen evolution rate over CdSLDH is much higher than its counterpart without alumina matrix, i.e. almost two times higher under the same conditions. The enhanced hydrogen generation performance can be attributed to the segregation and growth-inhibiting effects of the alumina matrix. In addition, CdSLDH also displays strong fluorescence properties and a long lifetime of photogenerated charge carriers.

The main limitations of photocatalytic efficiency are photo-generated electrons and holes' recombination and narrow light response. In this review, we focused on internal polar electric filed, which is one of the most efficient strategies to promote the separation of photo-generated electrons and holes, leads to high photocatalytic efficiency. This paper covers the fundamental principle of polar electric field build in photocatalysts, mechanism for polar electric field enhanced charge separation, and reviews the research works on the following photocatalystic system using internal polar electric field to separate photo-generated electrons and holes, such as layer-structure polar photocatalysts, silver silicates and single crystal ZnO photocatalyst. The internal polar electric field enhanced charge separation provides the basis for designing high efficient photocatalysts.

The aluminum-based metal–organic framework (MOF) made from 2-aminoterephthalate is a photocatalyst for oxygen evolution. This MOF can be modified by incorporating Ni2+ cations into the pores through coordination to the amino groups, and the resulting MOF is an efficient photocatalyst for overall water splitting.

Boron-doped monoclinic and tetragonal phases of BiVO4 were prepared by using the urea precipitation method, and the visible-light photocatalytic activities of pristine and boron-doped BiVO4 for oxygen generation from water were compared. Boron doping enhances the photocatalytic activities of BiVO4 . The reasons for this enhancement were probed by performing X-ray photoelectron, Raman, and electrochemical impedance spectroscopy measurements, and also by performing density functional calculations for model boron-doped BiVO4 structures. The photocatalytic activities of BiVO4 is enhanced by boron doping because the resulting BO4 tetrahedra, which are smaller than the VO4 tetrahedra, create an occupied defect level per boron lying approximately 0.17 eV above the valence-band maximum of pristine BiVO4 , and this defect level is localized because it is made up of the O 2 p levels of the BO4 tetrahedron. Thus, the BO4 tetrahedra that result from boron doping act as hole traps, thereby slowing down the recombination of photogenerated electrons and holes.

As eries of amorphous silver silicates with differ- ent compositions were synthesized for the first time by one-step co-precipitation. Silicate ions were found to have important role on determining visible light absorption and photocatalytic activities of amorphous silver silicates ,a nd the sample with Ag/Si ratio of 3.20 exhibits optimal pho- tocatalytic activity.

A visible-light-responsive bismuth-based metal-organic framework (Bi-mna) is demonstrated to show good photoelectric and photocatalytic properties. Combining experimental and theoretical results, a ligand-to-ligand charge transfer (LLCT) process is found to be responsible for the high performance, which gives rise to a longer lifetime of photogenerated charge carriers. Our results suggest that bismuth-based MOFs could be promising candidates for the development of efficient visible-light photocatalysts.

Well-faceted nanocrystals of anatase TiO(2) with specific reactive facets have attracted extraordinary research interest due to their many intrinsic shape-dependent properties. In this work, hierarchical TiO(2) microspheres consisting of anatase nanosheets or decahedrons were synthesized by means of a facile hydrothermal technique; meanwhile, the percentage of {001} facets can be tuned from 82 to 45%. Importantly, by investigating the photo-oxidation reactions for ˙OH radical generation and photoreduction reactions for hydrogen evolution, the TiO(2) microspheres consisting of nano-decahedrons with 45% {001} facets show superior photoreactivity (more than 4.8-times) compared to the nanosheets with 82% {001} facets. By analyzing the results of scanning electron microscopy (SEM), photoluminescence (PL) and first-principles density functional theory (DFT) calculations, a model of charge separation between the well-formed {001} and {101} facets is proposed, and the enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges among the crystal facets co-exposed.

Hierarchical Bi(2)O(2)CO(3) flowerlike microstructures have been synthesized for the first time using a facile, template-free, and low-temperature solution method. With an average diameter of about 3 microm, the as-prepared Bi(2)O(2)CO(3) microflowers are composed of numerous two-dimensional nanosheets with oriented terminal engagement. On the basis of electron microscopy observations, a plausible growth mechanism is proposed as a spatial self-assembly process accompanied by Ostwald ripening. The molar ratio of the initial reagents plays an important role in determining the morphologies of the Bi(2)O(2)CO(3) microstructures. UV/Vis spectroscopy is employed to analyze the band gaps of the products. Both mesopores and macropores are revealed in the Bi(2)O(2)CO(3) microflowers by means of nitrogen sorption and pore-size distribution. Moreover, evaluated by the degradation of methyl orange under UV illumination, the photocatalytic performance of the Bi(2)O(2)CO(3) hierarchical microflowers is almost six times higher than that of commercial Bi(2)O(2)CO(3). The higher specific surface area, the meso/macropores, and the intra-electric field formed between the (Bi(2)O(2))(2+) layer and the slabs comprising CO(3) (2-) in the Bi(2)O(2)CO(3) crystal structure, are believed to facilitate the separation of the photoinduced electrons and holes and thus improve the corresponding photocatalytic activity.

By means of a simple ion-exchange process (using different precursors) and a light-induced chemical reduction reaction, highly efficient Ag@AgCl plasmonic photocatalysts with various self-assembled structures-including microrods, irregular balls, and hollow spheres-have been fabricated. All the obtained Ag@AgCl catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV-visible diffuse reflectance spectroscopy. The effect of the different morphologies on the properties of the photocatalysts was studied. The average content of elemental Ag in Ag@AgCl was found to be about 3.2 mol %. All the catalysts show strong absorption in the visible-light region. The obtained Ag@AgCl samples exhibit enhanced photocatalytic activity for the degradation of organic contaminants under visible-light irradiation. The stability of the plasmonic photocatalysts was also investigated in detail.

Visible improvements: Owing to the plasmon resonance of silver nanoparticles deposited on the surface of AgBr, the newly-prepared plasmonic photocatalyst Ag section signAgBr has a strong absorption in the visible region (see picture) and shows high efficiency in the photodegradation of organic pollutants under visible light.

The title compound is prepared by addition of an aqueous Na2SiO3 solution to an AgNO3 solution and characterized by powder XRD, XPS, UV/VIS diffuse reflectance spectroscopy, and DFT calculations.

Ln(IO3)3 (Ln = Ce, Nd, Eu, Gd, Er, Yb) polycrystals are hydrothermally prepared using aqueous solutions of Ln(NO3)3 or Ln2O3 and HI as precursors (autoclave, 230 °C, 24 h).

Nanoparticles (NPs) of noble metals can strongly absorb visible light because of their plasmon resonance, which is greatly influenced by their morphology and size. The phenomenon of plasmon resonance gives rise to important applications such as colorimetric sensors, photovoltaic devices, photochromic devices, and photocatalysts. Noble metal NPs exhibit characteristic optical and physical properties that are substantially different from those of the corresponding bulk materials. In particular, silver NPs show efficient plasmon resonance in the visible region, which Awazu et al. recently utilized to develop a plasmonic photocatalyst. In their study, TiO2 was deposited on NPs consisting of a silver core covered with a silica (SiO2) shell to prevent oxidation of Ag by direct contact with TiO2. Under UV illumination, this plasmonic photocatalyst exhibits enhanced catalytic activity, which increases with decreasing thickness of the SiO2 shell. To enhance the activity of a plasmonic photocatalyst, it is desirable to deposit silver NPs directly onto the surface of an active dielectric substrate without a protective shell, because the near-field effect of the NPs will be more strongly felt by the substrate. Herein we show that such a photocatalyst can be obtained from silver chloride by exploiting its photosensitivity, and the resulting plasmonic photocatalyst is highly efficient and stable under visible-light illumination. Silver halides are photosensitive materials extensively used as source materials in photographic films. On absorbing a photon, a silver halide particle generates an electron and a hole, and subsequently the photogenerated electron combines with an Ag ion to form an Ag atom. Ultimately, a cluster of silver atoms is formed within a silver halide particle upon repeated absorption of photons. Due to this instability under sunlight, which provides the very basis for chemical photography, silver halides are seldom used as photocatalysts. Nevertheless, there have been reports that under UV/Vis illumination AgCl deposited on a conducting support photocatalyzes O2 production from water in the presence of a small excess of silver ions in solution, and that under UV illumination AgBr dispersed on a silica support photocatalyzes H2 production from CH3OH/H2O solution. [21] In their study on the AgBr/SiO2 photocatalyst, Kakuta et al. [21] observed that Ag species are formed on AgBr in the early stage of the reaction, and AgBr is not destroyed under successive UV illumination. As suggested by Kakuta et al., electron–hole separation may occur smoothly in the presence of Ag species, and the latter may catalyze H2 production from alcohol radicals formed by photo-induced holes. If so, silver NPs formed on silver halide particles might be expected to be a stable photocatalyst under visible-light illumination due to their plasmon resonance. This expectation led us to prepare a new photocatalyst active and stable under visible light, namely, AgCl particles with silver NPs formed on their surface, by first treating Ag2MoO4 with HCl to form AgCl powder and then reducing some Ag ions in the surface region of the AgCl particles to Ag species (for details, see the Experimental Section). For convenience, these are referred to as Ag@AgCl particles. The X-ray diffraction (XRD) pattern of the Ag@AgCl product clearly shows that the cubic phase of Ag with lattice constant a= 4.0861 A (JCPDS file: 65-2871) coexists with the cubic phase of AgCl with lattice constant a= 5.5491 A (JCPDS file: 31-1238; see Figure 1). Scanning electron microscopy (SEM) images of the Ag@AgCl product (Figure 2) reveal that silver NPs with diameters in the range of 20–150 nm are deposited on the surface of AgCl particles with diameters in the range of 0.2–1.3 mm. The UV/Vis diffuse-reflectance spectra of Ag@AgCl, AgCl, and N-doped TiO2 (used as reference photocatalyst) are compared in Figure 3. In contrast to AgCl and N-doped TiO2, Ag@AgCl has a strong adsorption in the visible region which is almost as strong as that in the UV region. This is attributed to the plasmon resonance of silver NPs deposited on AgCl particles. To evaluate the photooxidation capability of Ag@AgCl, we examined the decomposition of methylic orange (MO) dye in solution over the Ag@AgCl sample under visible-light irradiation as a function of time (Figure 4). For comparison, we also carried out decomposition of the MO dye in solution over the N-doped TiO2 reference photocatalyst under visible[*] P. Wang, Prof. Dr. B. Huang, X. Qin, Prof. X. Zhang, Dr. J. Wei State Key Lab of Crystal Materials Shandong University, Jinan 250100 (China) E-mail: bbhuang@sdu.edu.cn Homepage: http://www.icm.sdu.edu.cn/index.php

Microcrystals of the title compound are hydrothermally prepared from aqueous solutions of stoichiometric amounts of Cu(NO3)2 and Na2HPO4 (pH 7, autoclave, 120 °C, 6 h).

Metastable Bi{sub 20}TiO{sub 32} samples were synthesized by a high-temperature quenching method using alpha-Bi{sub 2}O{sub 3} and anatase TiO{sub 2} as raw materials. The photocatalytic activity of the as-prepared samples was measured with the photodegradation of methyl orange at room temperature under visible light irradiation. The Bi{sub 20}TiO{sub 32} samples exhibited good absorption in the visible light region with a band gap of about 2.38 eV and the band structure of Bi{sub 20}TiO{sub 32} was studied. Photodegradation against methyl orange was much better than alpha-Bi{sub 2}O{sub 3} prepared by the same way. The photocatalytic activity of Bi{sub 20}TiO{sub 32} samples is supposed to be associated with the hybridized Bi 6s and O 2p orbitals. In addition, the dispersive characteristic of Bi 6s orbital in the hybridized valence band facilitates the mobility of the photogenerated carriers and hampers their recombination. - Graphical abstract: Metastable Bi{sub 20}TiO{sub 32} samples were successfully synthesized by a quenching process. Photodegradation against methyl orange showed high visible-light activity and it was supposed to be associated with its corresponding band structure.

Nanoparticles (NPs) of noble metals can strongly absorb visible light because of their plasmon resonance, which is greatly influenced by their morphology and size. The phenomenon of plasmon resonance gives rise to important applications such as colorimetric sensors, photovoltaic devices, photochromic devices, and photocatalysts. Noble metal NPs exhibit characteristic optical and physical properties that are substantially different from those of the corresponding bulk materials. In particular, silver NPs show efficient plasmon resonance in the visible region, which Awazu et al. recently utilized to develop a plasmonic photocatalyst. In their study, TiO2 was deposited on NPs consisting of a silver core covered with a silica (SiO2) shell to prevent oxidation of Ag by direct contact with TiO2. Under UV illumination, this plasmonic photocatalyst exhibits enhanced catalytic activity, which increases with decreasing thickness of the SiO2 shell. To enhance the activity of a plasmonic photocatalyst, it is desirable to deposit silver NPs directly onto the surface of an active dielectric substrate without a protective shell, because the near-field effect of the NPs will be more strongly felt by the substrate. Herein we show that such a photocatalyst can be obtained from silver chloride by exploiting its photosensitivity, and the resulting plasmonic photocatalyst is highly efficient and stable under visible-light illumination. Silver halides are photosensitive materials extensively used as source materials in photographic films. On absorbing a photon, a silver halide particle generates an electron and a hole, and subsequently the photogenerated electron combines with an Ag ion to form an Ag atom. Ultimately, a cluster of silver atoms is formed within a silver halide particle upon repeated absorption of photons. Due to this instability under sunlight, which provides the very basis for chemical photography, silver halides are seldom used as photocatalysts. Nevertheless, there have been reports that under UV/Vis illumination AgCl deposited on a conducting support photocatalyzes O2 production from water in the presence of a small excess of silver ions in solution, and that under UV illumination AgBr dispersed on a silica support photocatalyzes H2 production from CH3OH/H2O solution. [21] In their study on the AgBr/SiO2 photocatalyst, Kakuta et al. [21] observed that Ag species are formed on AgBr in the early stage of the reaction, and AgBr is not destroyed under successive UV illumination. As suggested by Kakuta et al., electron–hole separation may occur smoothly in the presence of Ag species, and the latter may catalyze H2 production from alcohol radicals formed by photo-induced holes. If so, silver NPs formed on silver halide particles might be expected to be a stable photocatalyst under visible-light illumination due to their plasmon resonance. This expectation led us to prepare a new photocatalyst active and stable under visible light, namely, AgCl particles with silver NPs formed on their surface, by first treating Ag2MoO4 with HCl to form AgCl powder and then reducing some Ag ions in the surface region of the AgCl particles to Ag species (for details, see the Experimental Section). For convenience, these are referred to as Ag@AgCl particles. The X-ray diffraction (XRD) pattern of the Ag@AgCl product clearly shows that the cubic phase of Ag with lattice constant a= 4.0861 A (JCPDS file: 65-2871) coexists with the cubic phase of AgCl with lattice constant a= 5.5491 A (JCPDS file: 31-1238; see Figure 1). Scanning electron microscopy (SEM) images of the Ag@AgCl product (Figure 2) reveal that silver NPs with diameters in the range of 20–150 nm are deposited on the surface of AgCl particles with diameters in the range of 0.2–1.3 mm. The UV/Vis diffuse-reflectance spectra of Ag@AgCl, AgCl, and N-doped TiO2 (used as reference photocatalyst) are compared in Figure 3. In contrast to AgCl and N-doped TiO2, Ag@AgCl has a strong adsorption in the visible region which is almost as strong as that in the UV region. This is attributed to the plasmon resonance of silver NPs deposited on AgCl particles. To evaluate the photooxidation capability of Ag@AgCl, we examined the decomposition of methylic orange (MO) dye in solution over the Ag@AgCl sample under visible-light irradiation as a function of time (Figure 4). For comparison, we also carried out decomposition of the MO dye in solution over the N-doped TiO2 reference photocatalyst under visible[*] P. Wang, Prof. Dr. B. Huang, X. Qin, Prof. X. Zhang, Dr. J. Wei State Key Lab of Crystal Materials Shandong University, Jinan 250100 (China) E-mail: bbhuang@sdu.edu.cn Homepage: http://www.icm.sdu.edu.cn/index.php