A novel method to fabricate composition- and topology-controlled ZnO/TiO2 inverse opals (IO) films using a positive sacrificial ZnO IO template has been developed. This method includes a two-step process, preparation of ZnO IO by a simple electrochemical deposition using a self-assembly polystyrene colloidal crystal template and preparation of ZnO/TiO2 IO by a liquid phase deposition (LPD) process at room temperature. The composition and topology of ZnO/TiO2 IO can be easily controlled by changing the duration of the LPD. After 20 min LPD process, a ZnO/TiO2 composite IO with non-close-packed face-centered cubic air sphere array was obtained. Prolonging the duration to 60 min, a pure TiO2 IO (TIO-LPD60) with obviously thickened walls was formed. The formation mechanism for the compositional and topological variation was discussed. A preliminary study on UV photocatalytic property of the samples for degradation of methylene blue reveals that the composition and topology significantly influenced the photocatalytic activity of the IO film. The ZnO/TiO2 composite IO demonstrates a higher degree of activity than both pure ZnO and pure TiO2 IO, although they have a similar IO wall thickness. Moreover, with increasing IO wall thickness from ∼52 nm to ∼90 nm, TIO-LPD60 exhibits the highest level of photocatalytic performance.

TiO2 inverse opal films loaded with silver nanoparticles (ATIO) were synthesized on glass substrates. TiO2 inverse opal (TIO) films were prepared via a sol–gel process using self-assembly of SiO2 colloidal crystal template and a facile wet chemical route featuring an AgNO3 precursor solution to fabricate silver nanoparticles on the TIO films. The inverse opal structure and Ag deposition physically and chemically modify titania, respectively. The catalysts were characterized by Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), UV–vis absorption spectra, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. The HRTEM results show that Ag nanoparticles measuring 5–10nm were evenly distributed on TIO. Both the UV- and visible-light photocatalytic activities of the samples were evaluated by analyzing the degradation of methylene blue (MB) in aqueous solution. The results reveal that the apparent reaction rate constant (kapp) of MB degradation of the sample ATIO under UV-light irradiation is approximately 1.5 times that of the conventional Ag-loaded TiO2 film (ATF) without an ordered porous structure at an AgNO3 concentration of 5mM in the precursor solution. At an AgNO3 concentration of 10mM, the sample exhibits a kapp value approximately 4.2 times that of ATF under visible-light irradiation. This enhanced visible-light photocatalytic performance can be attributed to the synergistic effect of optimized Ag nanoparticle deposition and an ordered macroporous TIO structure. Repeated cycling tests revealed that the samples showed stable photocatalytic activity, even after six repeated cycles.

An efficient method for the preparation of N–F-codoped visible light active TiO2 nanorod arrays is reported. In the process, simultaneous nitrogen and fluorine doped TiO2 nanorod arrays on the glass substrates were achieved by liquid phase deposition method using ZnO nanorod arrays as templates with different calcination temperature. The as-prepared samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectra measurements. It was found that calcination temperature is an important factor influencing the microstructure and the amount of N and F in TiO2 nanorod arrays samples. The visible light photocatalytic properties were investigated using methylene blue (MB) dye as a model system. The results showed that N–F-codoped TiO2 nanorod arrays sample calcined at 450°C demonstrated the best visible light activity in all samples, much higher than that of TiO2 nanoparticles and P25 particles films.

TiO2 ordered porous films(TIO) were fabricated via TiCl4 sol-gel dip-coating process using self-assembly SiO2 colloidal crystal as templates and Ag nanoparticles were achieved on the TIO by a liquid infiltration route,and Ag/TiO2 ordered porous composite films(ATIO) were obtained.The characteristics of the composite films were measured by Raman,FESEM,TEM,XPS and UV-vis.The results reveal that the average size of Ag nanoparticles is about 10 nm,and strong interaction exists between Ag nanoparticles and TiO2 nanocrystals.Visible light photocatalytic activities of samples with different Ag/Ti relative atomic concentration ratios and cycling tests were evaluated by analyzing the degradation of methylene blue(MB) in aqueous solution,and were compared with Ag/TiO2 disordered composite films(ATF).It is found that the TIO with AgNO3 concentration value 10 mmol/L in the precursor solution exhibits 3.19 times visible light degradation rate compared with conventional Ag deposited TiO2 disordered film without the ordered porous structure.This obvious enhanced visible-light photocatalytic activity for the Ag deposited TIO sample can be attributed to the synergetic effect of Ag nanoparticles and TIO ordered porous structures.The repeated cycling tests suggest that samples show stable photocatalytic activity.

Silver-modified ZnO nanorods array has been prepared and the effect of silver modification has been studied. ZnO nanorods array were fabricated through a wet chemical route and a photo deposition method was taken to fabricate silver nano particulate on the ZnO nanorods. The structural and optical properties were characterized by field emission scanning electron microscope, high resolution transmission electron microscope, X-ray photoelectron spectroscopy, Raman, UV–vis and photoluminescence (PL) spectra. The UV photocatalytic activity of these materials was studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The photocatalytic performance indicated that Ag deposit acted as not only electron sinks to enhance the separation of photoexcited electrons from holes, but also charge carrier recombination centers, so the optimized amount of Ag deposit was investigated.

An efficient method for the preparation of visible light response N-F-codoped TiO2nanorod arrays(TNRAs)is reported.In the process,simultaneous nitrogen and fluorine doped TNRAs on the glass substrates were achieved by liquid phase deposition(LPD)method using ZnO nanorod arrays as templates.The as-prepared samples were characterized by SEM,TEM,Raman,XPS and UV-vis.The visible light photocatalytic activity of all samples was evaluated by photodegradation of methylene blue (MB)in aqueous solution.It was found that N-F codoping exhibits significant improvement of visible light absorption and the N-F-codoped TNRAs samples calcined at 450℃for 2hdemonstrate the best visible light activity in all samples.The excellent photocatalytic activity can be ascribed to the synergetic effect of the unique 1Dnanorod arrays structure and some beneficial effects induced by the appropriate amount of N and F doping in TNRAs.

We reported a new simple route to fabricate N-F-codoped titania inverse opal (IO) films with a hierarchical meso-/macroporous structure, in which the IO structure and the N-F codoping play a role as physical and chemical modifications for titania, respectively. Both modifications are simultaneously achieved via a liquid phase deposition process using a silica colloidal crystal as a template for the first time. The average size of a mesopore in the TiO2 frameworks is 3.2 nm, and that of an interpenetrating aligned macropore is adjusted in the range of 201-315 nm. The N-F-codoped TiO2 IO films exhibit 6.6-7.4 times the methylene blue visible-light photodegradation rate comparing with N-F-codoped TiO2 films without the IO structure. This high visible-light activity was mainly ascribed to a synergetic effect of the hierarchical meso-/macroporous structure and N-F codoping. Furthermore, it was found that the multiple scattering effect of the macroporous structure is more pronounced than the slow photon effect of IOs for facilitating visible-light photocatalysis in our system from the comparison with nonperiodic macroporous N-F-codoped TiO2. The repeated cycling tests revealed that samples showed stable photocatalytic activity.

The simultaneous Ag loaded and N-doped TiO2 hollow nanorod arrays with various contents of silver (Ag/N–THNAs) were successfully synthesized on glass substrates by one-pot liquid phase deposition (LPD) method using ZnO nanorod arrays as template. The catalysts were characterized by Raman spectrum, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscope (HRTEM), ultraviolet–vis (UV–vis) absorption spectrum and X-ray photoelectron spectroscopy (XPS). The results suggest that AgNO3 additive in the precursor solutions not only can promote the anatase-to-rutile phase transition, but also influence the amount of N doping in the samples. The photocatalytic activity of all the samples was evaluated by photodegradation of methylene blue (MB) in aqueous solution. The sample exhibited the highest photocatalytic activity under UV light illumination when the AgNO3 concentration in the precursor solution was 0.03M, due to Ag nanoparticles acting as electron sinks; When the AgNO3 concentration was 0.07M, the sample performed best under visible light illumination, attributed to the synergetic effects of Ag loading, N doping, and the multiphase structure (anatase/rutile).

Cu2O and ZnO inverse opal composite materials were fabricated using polystyrene(PS) colloidal crystal as templates by two-step electrodeposition method.UV-Vis spectrum shows an obvious photonic stop band of the composite materials.The position of the photonic stop band can be changed by changing the photonic stop band of the ZnO inverse opal.The effects of temperature and pH value on the preparation of the Cu2O and ZnO inverse opal composite materials was also studied.

Cu2O–ZnO composite opal was fabricated by electrodeposition using ZnO inverse opal as template. The photonic stop band of the composite opal can be observed from the UV–Vis spectrum, which indicates that the Cu2O filled into ZnO inverse opal did not destroy its three-dimensional (3D) ordered structure. Due to the multiple scattering in the 3D ordered structure, the absorption and photoluminescence (PL) are stronger in Cu2O–ZnO composite opal than those in a Cu2O/ZnO bilayer film and a Cu2O/ITO film without 3D ordered structure. The remaining ZnO inverse opal in Cu2O–ZnO composite opal enhances the photoluminescence measured in back geometry while it suppresses that in front geometry.

The Z-scheme type CdS–Au–TiO2 hollow nanorod arrays have been constructed on glass substrates by following these simple steps: firstly, highly ordered TiO2 hollow nanorod arrays (THNAs) were synthesized by liquid phase deposition (LPD) using ZnO nanorod arrays as templates; then both Au core and CdS shell nanoparticles were achieved on the THNAs by in situ photodeposition. The prepared three-component films were characterized by field-emission scanning electron microscopy (FSEM), high-resolution transmission electron microscope (HRTEM), Raman scattering and ultraviolet–visible absorption spectrum. The results showed that Au–CdS core–shell nanoparticles were well dispersed on wall of anatase THNAs from top to bottom. The three-component nanojunction system was evaluated for their photocatalytic activity through the degradation of methylene blue (MB) in aqueous solution. It was found that the CdS–Au–TiO2 three-component hollow nanorod arrays exhibited significantly enhanced photocatalytic activity compared with single (THNAs) and two components (Au-THNAs or CdS-THNAs) systems. Reasons for this enhanced photocatalytic activity were revealed by photoluminescence (PL) results of our samples.

ZnO:Ag films were grown on Si (100) substrates by ultrasonic spray pyrolysis at various substrate temperatures. The effect of deposition temperature on the structural and the room temperature photoluminescence (RT–PL) properties of ZnO:Ag films was studied. With the deposition temperature rising to 550°C, the intensity of the near-band edge (NBE) emission at 378nm decreased and a new emission peak at 399nm was observed. On the basis of the X-ray diffraction pattern (XRD), the X-ray photoelectron (XPS) spectra of ZnO:Ag films, and the effects of annealing on the PL, we suggest that the 399nm emission should be attributed to the electron transition from the conduction band to AgZn-related complexes defects radiative centers above the valence band.

Flowerlike ZnO nano/microstructures (FZNM) have been synthesized on glass substrates by a simple hydrothermal method. The as-prepared samples are composed of many radially oriented nano/submicron rods, which are single crystalline with a hexagonal structure and grow along the [001] direction. The diameter of ZnO nano/submicron rods ranges from 20 nm to 1 microm. With prolonged reaction time, the number of the nano/submicron rods of each ZnO flowerlike will decrease, while further prolonged reaction time, the amount increase actually. The reaction time is one key factor to control the sizes of the rods and the morphology of flowerlike structures. The possible growth mechanism has been discussed and proposed. A preliminary study on photocatalytic property of as-synthesized flowerlike structure reveals that morphology and size significantly influenced the photocatalytic activity for a solution of methylene blue (MB). Moreover, it is found that the annealed product exhibited higher photocatalytic performance.

Aligned ZnO nanorods and nanotubes were grown on the silicon substrates by thermal evaporation of high pure zinc powders without any other metal catalyst. The morphology evolution of ZnO nanostructures with prolonged growth time suggested that the growth of the ZnO nanorods and nanotubes follows the vapor–liquid–solid mechanism. ZnO nanoneedle and nanoparticle films were also synthesized by the same way, and their photocatalytic performances were tested for the degradation of organic dye methylene blue. The ZnO nanoneedle films exhibited very high photocatalytic activities. The decomposition kinetics of the organic pollutant was discussed. Moreover, it is found that the ZnO nanoneedle films showed very stable photocatalytic activity.

The excitation-power dependence of the near-band-edge emission in ZnO inverse opals and nanocrystal films has been studied. The dependence of the photoluminescence intensity I on the excitation power L can be described by a power law, i.e., I∼Lα, where α is an exponent that is often used to identify the origin of the near-band-edge emission from semiconductors in previous models. However, in this work, it was found that the values of α show a strong variation between ZnO inverse opals and nanocrystal films. And our results show that the change of α is mainly caused by the laser heating effects. Therefore, the value of α could not be simply employed to unequivocally evaluate the origin of the near-band-edge emission in complex nanostructures.

The tetragonal prism SnO2 nanorods with the rutile structure have been successfully synthesized by a simple solvothermal method from high concentration precursors without any surfactant. Their sizes, morphologies and structure were studied by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), select-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SnO2 nanorods obtained by the solvothermal method exhibit higher crystalline quality and better dispersion compared with the samples prepared by the hydrothermal method. Our results suggest that the solvent plays an important role to obtain high-yield SnO2 nanorods with high quality.

We systematically investigated the photoluminescence (PL) and transmittance characteristics of ZnO–SiO2 opals with varied positions of the stop-band and film thicknesses. An improved ultraviolet (UV) luminescence was observed from ZnO–SiO2 composites over pure ZnO nanocrystals under 325 nm He–Cd laser excitation at room temperature. The UV PL of ZnO nanocrystals in SiO2 opals with stop-bands center of 410 nm is sensitive to the thickness of opal films, and the UV PL intensity increases with the film thickness increasing. The PL spectra of ZnO nanocrystals in SiO2 opals with stop-bands center of 570 nm show a suppression of the weak visible band. The experimental results are discussed based on the scattering and/or absorbance in opal crystals.

ZnO sub-micrometer sized disk using ethanol/water mixed solution as solvent is synthesized by solvent-thermal process without any additive, while ZnO nanorods are obtained when water is used as solvent. This formation of disk is discussed based on the reaction of Zn-terminated ZnO (0001) plane with ethanol molecule, which results in the passivation of ZnO (0001) planes and lowering the free surface energy of ZnO (0001).

The fabrication of ordered porous titania films using polystyrene colloidal crystal templates by cathodic electrodeposition is reported. A new strategy using Ti(SO4)(2) as Ti source for the potentiostatic electrodeposition of titania has been developed. An improved post-treatment of the electrodeposited samples was executed to obtain long-range ordered porous films.