Dimensionally stable anode (DSA) of antimony-doped tin dioxide electrode based on TiO2-nanotube arrays (NTs) has been successfully fabricated through thermal decomposition. The surface morphology and composition of the electrodes were characterized by using scanning electron microscopy and X-ray diffraction. Methyl orange (MO) was used as a model pollutant to investigate the electrochemical properties of these two electrodes. The optimized anodic oxidation voltage and time for TiO2-nanotubes array based DSA electrode is 60 V and 10 min, respectively. The results show that Ti/TiO2–NTs/Sb–SnO2 electrode has an increase of 100 mV in oxygen evolution overpotential and the service life is 56% longer than that of the traditional DSA electrode. Under the optimum conditions, MO solution decolorization rate and TOC removal rate reached approximately 100 and 80%, respectively. Study suggested that the as-prepared Ti/TiO2–NTs/Sb–SnO2 DSA electrode exhibits high activity for degradation of organic pollutant with high concentration.

TiO2@CdSe/CdS core–shell hollow nanospheres solar paint was successfully prepared via hard template and ion exchange method considering the match of their band gap. The outer layer of TiO2 shell protects CdSe and CdS from decomposition and increases their stability. The diameters of the TiO2@CdSe/CdS hollow nanospheres were uniformly around 600 nm with a shell thickness of 70 nm. The visible light absorption onset of TiO2@CdSe/CdS hollow nanospheres is around 650 nm corresponding to a bandgap of 1.8 eV, showing a red-shift when compared with TiO2/CdS. TiO2@CdSe/CdS hollow nanospheres can be directly used as solar paint. The photoanode decorated by the solar paint performs a reliable photoelectric conversion efficiency of ∼0.79% and current density of 6.6 mA cm−2.

•Pt/TiO2-NTs/Ti mesh electrode was fabricated on Ti mesh via thermal reduction.•The Pt/TiO2-NTs/Ti mesh electrode exhibited excellent photovoltaic performance.•A flexible DSSC assembled with this mesh electrode achieved a PCE value of 5.60%.A platinum (Pt) nanoparticle-covered titania (TiO2) nanotube arrays titanium (Ti) mesh electrode (Pt/TiO2-NTs/Ti) has been successfully fabricated on Ti mesh via a thermal reduction technique by spraying H2PtCl6·6H2O isopropanol solution onto vertically oriented TiO2 nanotube arrays. Electrochemical impedance spectroscopy (EIS) and cyclic voltammerty (CV) investigations showed that the Pt/TiO2-NTs/Ti mesh electrode has superior electrocatalytic activity, good stability, and low ohmic series resistance (3.41 Ω cm2). With the diamond-shaped holes, the actual area of the Ti mesh electrode was less than that of the Pt/FTO glass electrode, but the catalytic activities were essentially equal. A flexible dye-sensitized solar cell was assembled from the Pt/TiO2-NTs/Ti mesh electrode and a sensitized TiO2 photoanode on Ti foil substrate, and it reached a power conversion efficiency (PCE) of 5.6% using a backside illumination simulated solar light (AM 1.5G, 100 mW cm−2).We fabricate Pt/TiO2-NTs/Ti mesh electrode via a thermal reduction technique of H2PtCl6·6H2O isopropanol solution in a vertically oriented TiO2 nanotube arrays. The power conversion efficiency (PCE) reaches 5.6% under a backside illumination simulated solar light (AM 1.5G, 100 mW cm-2) by using this special Pt/TiO2-NTs/Ti mesh as counter electrode

•TiO2 was doped with different ratios of graphene and applied in quantum dot-sensitized solar cells (QDSSCs).•The efficiency of QDSSCs was changed with the ratios of graphene composition.•The QDSSCs incorporating 0.1 wt% graphene demonstrated a best power conversion efficiency of 2.8%.To optimize the performance efficiency of quantum dot-sensitized solar cells (QDSSCs), TiO2 doped with different ratios of graphene were prepared and applied in quantum dot-sensitized solar cells. The graphene–TiO2 nanocomposites were prepared by using hydrothermal synthesis of the alcohol–water system between graphene and TiO2 nanoparticles. It was found that the efficiency of quantum dot-sensitized solar cells was changed with the ratios of graphene composition. The CdS/CdSe quantum dot-sensitized solar cells incorporating 0.1 wt% graphene in the TiO2 photoanode demonstrated the most improvement in power conversion with an efficiency of 2.8%, which was 37% higher than that of pure TiO2.TiO2 doped with different ratios of graphene were prepared and applied in quantum dot-sensitized solar cells. It was found that the efficiency of quantum dot-sensitized solar cells was changed with the ratios of graphene composition. The CdS/CdSe quantum dot-sensitized solar cells incorporating 0.1 wt% graphene in the TiO2 photoanode demonstrated the most improvement in power conversion with an efficiency of 2.8%, which was 37% higher than that of pure TiO2.

We report an anisotropic etching route to prepare rutile TiO2 microspheres with a tube-in-tube nanostructure from their rod-like precursor. The crystalline structures and morphologies of both the precursor and the final product were examined by X-ray powder diffraction (XRD), field emission-scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). We also examined the photovoltaic performances of our samples by assembling them in photoanodes in dye-sensitized solar cells (DSSCs). The TiO2 microspheres sample with the tube-in-tube nanostructure shows a 213% and 269% increase in short current and conversion efficiency compared to that of TiO2 nanorods microspheres. The most interesting result in this study is that, even under the conditions with less dye adsorption (ca. 20% less), an optimized photoanode containing our TiO2 sample showed an energy-conversion efficiency of 7.57%, higher than the value (6.50%) of the photoanode containing solely anatase TiO2 nanoparticles. We concluded that the unique micro and nanostructure helps to increase the light harvesting and, thus, improve the photovoltaic performance of DSSCs.

Here, mixed-phase TiO2 nanorods assembled microspheres were fabricated via a facile one-step hydrothermal process. The synthesized samples were investigated employing X-ray powder diffraction (XRD), Raman spectrometry, field emission-scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The study shows the interesting symbiotic phenomenon occurred in the mixed anatase and rutile phase TiO2. The mixed crystalline phase of anatase–rutile ratios were accurately tuned by adjusting the concentration of disodium edetate (EDTA). The crystalline phase has a great influence on their photovoltaic performance. The photoelectric conversion efficiency increases by 162% when the anatase weight ratio increases from 6% to 51%. While a 263% increase in the photoelectric conversion efficiency of the optimized mixed-phase TiO2 nanorods is achieved when compared to the pure rutile phase TiO2. Accordingly, the DSSCs based on the optimized mixed-phase TiO2 nanorods assembled microspheres show a high open circuit voltage of 0.85 V and a conversion efficiency of 8.85% with a relative low dye adsorption of 0.99 × 10−7 mol cm−2.

Dye-sensitized solar cells (DSSCs) are currently under intense academic and industrial investigations, because of their environmentally-friendly, efficient, and low-cost features. The photosensitizer plays a key role in determining DSSCs' performance. The 4,4′-di(2-thienyl)triphenylamine moiety, included in dye TTC102, has been demonstrated before as a novel and efficient electron donor fragment. In this paper, the oversimple π-conjugated bridge of TTC102 was replaced by a 9-ethyl-3,6-di(2-thiophenyl)carbazole moiety. Two new D-D-π-A sensitizers, named TTC104 and TTC105, were synthesized and fully characterized. After anchoring on TiO2 nanoparticle film, the absorption band of TTC104 is broader by 30 nm than that of TTC102. Under AM 1.5G irradiation, the energy conversion efficiency (η) of a DSSC based on TTC104 reaches 6.36%, which is 21.6% higher than that of TTC102 (5.24%). The results above demonstrate that the photovoltaic performance can be improved after introducing the 9-ethyl-3,6-di(2-thiophenyl)carbazole moiety to TTC102 when employed in DSSCs. Dye TTC105, containing a pyridyl group as the electron acceptor, showed only 1.88% conversion efficiency (η) when used in DSSCs. The huge different performances of TTC104 and TTC105 are proved to be partly due to the smaller dye loading amount, higher dark current and charge recombination rate of TTC105.

Owing to the excellent physical and chemical properties for potential application in multiple fields, design and synthesis of semiconductor titanium dioxide with tailor-made crystal facets and V-shaped porous sturcuctures have attracted great research interest. In this work, we prepared hollow anatase TiO2 microspheres (HTS) with exposed (101) facets and V-shaped channels via a novel anisotropic etching method. The obtained HTS microspheres are constructed by two layers, the inner layer is TiO2 nanoparticles, while the outer layer is composed of single-crystal TiO2 nanosheets with highly exposed (101) facets and V-shaped channels. The cooperative effect of hydrogen peroxide with ammonium fluoride and an anisotropic corrosion process are proposed to understand the formation mechanism. Hydrogen peroxide decomposed to form O2 bubbles, which acted as templates for the formation of TiO2 microspheres with cavities. Fluorine ions were able to promote the formation of anatase (001) facets at the beginning of the reaction and then etch the (001) facets with the reaction progress, leaving highly exposed (101) facets and V-shaped channels along the [001] direction. Due to the unique structure of anatase TiO2 (101) single crystal nanosheets and the strong light scattering effects from the V-shaped channels, the dye-sensitized solar cells (DSSCs) based on our HTS sample have a high open voltage of 0.9 V. The optimized DSSC based on our HTS sample showed an overall light-electron conversion efficiency of 7.05% with a lower dye absorption.

Mesoporous and hollow structure have been attracting increasing attention for their special properties and potential applications. Here we show a facile fabrication of hollow and mesoporous ZnO microsphere via a one-step wet chemical process using polyethylene glycol (PEG, MW 200) as the solvent and soft template. The morphology and structure of the products were characterized by using scanning electron microscopy and X-ray powder diffraction techniques. Thermal analysis and Fourier transform infrared spectroscopy techniques were also performed to show the properties of the precursor and annealed product. A possible growth mechanism of hollow and mesoporous ZnO microsphere was also proposed. The Brunauer–Emmett–Teller surface area of ZnO microsphere is 28.5 m2g–1 and the size of mesopores is about 10 nm. The Photoluminescence spectra of the as-synthesized ZnO hollow microspheres were also presented. The mesoporous and hollow structure enhance the gas sensitivity of ZnO microsphere, and the obtained ZnO microspheres based sensor has an excellent performance for precision detection of ethanol and acetone with low concentration.Keywords: gas sensing; hollow microspheres; mesoporous; PEG 200; ZnO;

We report for the first time the combustion synthesis of flower-like ZnO–SnO2 composite microspheres by decomposition at temperatures of 873 K in the presence of polyethylene glycol as the surfactant. A plausible mechanism for the formation of the core-shell structured microspheres is also proposed. The as-obtained sample exhibits good sensing properties against ethanol vapour at an operating temperature of 673 K, including a rapid response and recovery and high sensitivity, which makes the product a good candidate for fabricating ethanol sensors.

Dye-sensitized solar cells are currently under intense academic and industrial investigation, owing to their great potential to serve as a low-cost alternative to existing photovoltaic technologies. This paper puts forward a method, which adopts heterocyclic substituted triarylamine units as electronic donor moieties, to design triarylamine dyes for efficient dye-sensitized solar cells. Three novel triarylamine dyes named TTC101, TTC102 and TTC103, were synthesized economically through modification of the structure of a simple triarylamine dye (TC105) using three kinds of heterocyclic groups (4-pyridyl, 2-thienyl and 1-pyrazolyl). The crystal structure of TTC103 indicates that the heterocyclic groups would partly delocalize the positive charge after photooxidation. The overall solar-to-electrical energy conversion efficiencies (η) of TTC102 and TTC103 are 4.92% and 5.21% respectively under AM1.5G irradiation, reaching ∼82.3% and ∼77.7% of a N719-based reference cell under the same conditions. Besides, the energy conversion efficiencies (η) of TTC102 and TTC103 are 1.29 and 1.37 times the efficiency of TC105 respectively. All of the results above demonstrate that photovoltaic performance can be improved by introducing suitable heterocyclic groups to triarylamine dyes. A series of properties were investigated to explain the results, with a special emphasis on the geometric structures, energetics, and charge transfer processes at the dye/titania/electrolyte interface.

Titanium dioxide mesoporous microspheres with high surface area was successfully prepared by a facile one-step hydrothermal approach using polyethylene glycol (PEG, MW 200) as the soft template. Study shows that ∼15 nm TiO2 nanoparticles was assembled into ∼1.1 μm mesoporous microspheres. The Brunauer-Emmett-Teller surface area of TiO2 microsphere is up to 137 m2/g. TiO2 mesoporous microspheres were fabricated onto the surface of fluorine-doped tin oxide glass and used as the photoanode of dye-sensitized solar cells, which exhibits an open circuit photovoltage of 0.80 V and an overall conversion efficiency of 6.6%. Owing to the enhanced dye loading and light-harvesting efficiency, a 26% improvement in the overall conversion efficiency was achieved when compared with the commercial Degussa P25 nanoparticles.Highlights► TiO2 mesoporous spheres (TMS) was prepared and used as photoanodes in DSSC. ► TMS can provide a notably high surface area for dye loading. ► The suitable size of TMS enhance the light-scattering capability. ► A 26% improvement in the overall conversion efficiency was achieved when compared with Degussa P25.

Flower-like ZnO microspheres constructed by multilayered porous nanosheets were obtained through a hydrothermal preparation and a thermal decomposition. The products before and after thermal decomposition have been characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and room-temperature photoluminescence. The growth mechanism of Zn4(CO3)(OH)6·H2O curling nanopetals to ZnO stretching porous nanosheets was also proposed in this paper. The existence of a large number of oxygen vacancies improved by the adsorption of oxygen in these porous nanosheets enhanced the gas sensing property which was demonstrated by the photoluminescence spectra. The gas sensing experiments were carried out under different concentrations of ethanol and acetone at 623 K. Results showed that the porous ZnO had high response value and short response time to our testing gases. We also suggested that the sensors based on the flower-like porous ZnO microspheres are more suitable for the detection of acetone in low concentration.Highlights► Facile preparation of ZnO microspheres was constructed by layered porous nanosheets. ► Mechanism of Zn4(CO3)(OH)6*H2O nanopetals turning into ZnO nanosheets is explained. ► Gas sensing was enhanced by large density of oxygen vacancies in the porous nanosheets. ► Porous ZnO has high response value and short response time to our testing gases.

Novel microsphere assembly of multi-sized TiO2 branched nanorods were successfully fabricated via a hydrothermal method. We demonstrate the direct formation of CdS QDs on TiO2 microspheres films by sequential chemical bath deposition. The as-prepared film was characterized by X-ray diffractmeter (XRD), scanning electron microscopy (SEM), Field-emission scanning electron microscopy (FE-SEM) and UV–vis absorption spectroscopy. Study show CdS sensitized branched TiO2 multisized nanorods film electrode have a better solar cell performance with a high open-circuit photovoltage of 0.68 V, a short-circuit current of 2.53 mA/cm2 and a conversion efficiency of 0.71%.

Preparation of micro-lotus constructed by hierarchically porous Fe-doped ZnO nanosheets via a facile hydrothermal method is reported here. The products have been analyzed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high resolution transmission electron microscope (HRTEM). Results showed that the morphology of the sample did not change with the Fe doping amount. The photoluminescence (PL) spectra revealed the existence of oxygen vacancies in the Fe-doped ZnO porous nanosheets, which is beneficial to the adsorption of oxygen and gas response, resulting in the improved performances in the later gas sensing experiments towards several reductive gases. The effect of Fe doping percentage on the gas response has also been investigated. We found that ZnO sample with Fe doping atomic percentage of 1% showed the highest gas sensing performance, while excessive Fe doping in ZnO suppressed the gas sensing response. A possible mechanism of how Fe-doped ZnO-based sensor responses to the target gas is also proposed.Micro-lotus constructed by porous Fe-doped ZnO nanosheets were successfully prepared by a one-step hydrothermal route. The Fe-doped ZnO with micro-nanostructures shows significantly improved gas response to several reductive gases compared with the undoped ZnO, however, excessive Fe doping suppresses the gas sensing response.

We demonstrate here for the first time the fabrication of a novel morphology of rutileTiO2 tapered nanotubes with rectangular cross-sections via a facile hydrothermal method using TiO2nanorod as the precursor. A plausible anisotropic corrosion mechanism for the formation of TiO2 nanotubes is also proposed.

We proposed here a temperature-induced solid-phase oriented rearrangement route to the fabrication of NaNbO3 nanowires by using sandia octahedral molecular sieves (SOMS) Na2Nb2O6·H2O as a precursor. The SOMS precursor was prepared by using metal Nb powder as a raw material through the hydrothermal approach.

Spongy-like NaTaO3 mesoporous microspheres are assembled from nanoparticles via imperfect oriented attachment. Study shows that the NaTaO3 spongy microspheres with the diameters of ∼1 μm are composed of the fundamental building blocks of ∼50 nm NaTaO3 nanospheres. The high-resolution transmission electron microscopy further reveals that these fundamental building blocks are assembled from primary building blocks of ∼10 nm NaTaO3 nanocrystals. The pore diameters of these spongy microspheres are ca. 30 nm and the Brunauer–Emmett–Teller (BET) surface area is calculated to be 57.8 m2 g−1. This interesting ternary alkali metal composite oxide of NaTaO3 spongy microspheres with high specific surface area and strong stability will be favorable for their practical application in photocatalysis. This synthesis route may throw light on the fabrication of the binary or ternary porous metal oxides by geometrical stacking of the nanobuilding blocks via imperfect oriented attachment.

We report in this paper a facile hydrothermal route for the preparation of Sb2O3 nanoribbons assembly with different aspect ratio and Sb2O3 polyhedral nanoparticles. Study indicates that the ratio of water and ethanol affects the morphology, size and crystal phase of Sb2O3 assembly building blocks. In a mixed alcohol and water solution, the orthorhombic Sb2O3 nanoribbons with a length of ∼4 μm and a width of 400 nm were assembled into rod-like structures, while a length of ∼3 μm and a width of 300 nm Sb2O3 nanoribbons were assembled into quadrangle structures with the increase of the water ratio. In the absolute alcohol solution, the cubic Sb2O3 particles with polyhedral morphology were formed. PL spectra indicate that the morphology strongly affects the luminescence property. The possible formation mechanisms involving the surfactant-assisted self-assembly and the confined growth were also proposed for the formation of the bundled nanoribbons and polyhedral granules, respectively.We report here a facile hydrothermal route for the preparation of Sb2O3 nanoribbons assembly and Sb2O3 polyhedral nanoparticles. Study show the morphology strongly affects the luminescence property.

Mesoporous core−shell structured titanium dioxide (TiO2) microspheres were successfully prepared by a facile one-step hydrothermal method using polyethylene glycol (PEG, MW 2000) as the soft template. The products were characterized in light of the morphology and chemical composition using scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction (XRD) techniques. The XRD patterns show that the direct hydrothermal synthesized product is anatase titanium dioxide. The Brunauer−Emmett−Teller surface area is 113.8 m2/g, and the average pore size is 5.78 nm. In addition, the morphology evolution of core−shell structured titanium dioxide with the different hydrothermal times was also studied. Research shows that the shell morphology and the core size of the core−shell TiO2 spheres can be easily tuned by controlling the hydrothermal time through the Ostwald ripening process. A possible growth mechanism of the mesoporous core−shell structured TiO2 hollow microspheres was also proposed in this paper.

Growth and assembly of ZnO nanosheets into hollow microsphere are performed using PEG 200 as directing agent. FESEM images show that the average width of these assemblied ZnO nanosheets is around ∼250 nm, the length is about 500–800 nm and the thickness is about 25 nm, the diameter of ZnO-assembled microsphere is about 2–4 μm. Study shows that microsphere of ZnO nanosheets have a centre cavity, these microsphere assemblied ZnO nanosheets have a wide visible yellow emission at 567 cm−1, confocal laser microscopy of an individual ZnO nanosheets assemblied microsphere also show the intense yellow light emission. The oriented attachment of ∼5 nm ZnO nanoparticle building blocks eventually form the ZnO nanosheets. The most plausible dissociation–deposition mechanism that directs the formation of microspheric assembly of ZnO nanosheets is also proposed.

Novel superstructures of multilayered ZnO nanosheets with hierarchically porous structures are successfully synthesized from a hydrothermal preparation and thermal decomposition of a layered precursor of zinc hydroxide carbonate (denoted as ZnHC). Nanosheet-based ZnHC microspheres are self-assembled by the hydrothermal process by using zinc nitrate hexahydrate and urea as the starting materials. The corresponding microspheric organizations of multilayered ZnO nanosheets with hierarchically porous structures are obtained by the thermal decomposition ZnHC precursor at 573 K. SEM images show that the average diameter of ZnO assembled microspheres is about 15 μm, and the length of a ZnO nanosheet building block which is made up of thin mutilayered sheets is around ∼7 μm. Studies also show well-crystallized pores with hierarchically distributed pore sizes are embedded in the multilayered ZnO nanosheets building blocks. A plausible dissociation-deposition mechanism using in situ formed Zn(OH)2 nuclei as the “sacrificial” templates for the microsphere assembly is also proposed.

Dye-sensitized solar cells are currently under intense academic and industrial investigation, owing to their great potential to serve as a low-cost alternative to existing photovoltaic technologies. This paper puts forward a method, which adopts heterocyclic substituted triarylamine units as electronic donor moieties, to design triarylamine dyes for efficient dye-sensitized solar cells. Three novel triarylamine dyes named TTC101, TTC102 and TTC103, were synthesized economically through modification of the structure of a simple triarylamine dye (TC105) using three kinds of heterocyclic groups (4-pyridyl, 2-thienyl and 1-pyrazolyl). The crystal structure of TTC103 indicates that the heterocyclic groups would partly delocalize the positive charge after photooxidation. The overall solar-to-electrical energy conversion efficiencies (η) of TTC102 and TTC103 are 4.92% and 5.21% respectively under AM1.5G irradiation, reaching ∼82.3% and ∼77.7% of a N719-based reference cell under the same conditions. Besides, the energy conversion efficiencies (η) of TTC102 and TTC103 are 1.29 and 1.37 times the efficiency of TC105 respectively. All of the results above demonstrate that photovoltaic performance can be improved by introducing suitable heterocyclic groups to triarylamine dyes. A series of properties were investigated to explain the results, with a special emphasis on the geometric structures, energetics, and charge transfer processes at the dye/titania/electrolyte interface.

Dye-sensitized solar cells (DSSCs) are currently under intense academic and industrial investigations, because of their environmentally-friendly, efficient, and low-cost features. The photosensitizer plays a key role in determining DSSCs' performance. The 4,4′-di(2-thienyl)triphenylamine moiety, included in dye TTC102, has been demonstrated before as a novel and efficient electron donor fragment. In this paper, the oversimple π-conjugated bridge of TTC102 was replaced by a 9-ethyl-3,6-di(2-thiophenyl)carbazole moiety. Two new D-D-π-A sensitizers, named TTC104 and TTC105, were synthesized and fully characterized. After anchoring on TiO2 nanoparticle film, the absorption band of TTC104 is broader by 30 nm than that of TTC102. Under AM 1.5G irradiation, the energy conversion efficiency (η) of a DSSC based on TTC104 reaches 6.36%, which is 21.6% higher than that of TTC102 (5.24%). The results above demonstrate that the photovoltaic performance can be improved after introducing the 9-ethyl-3,6-di(2-thiophenyl)carbazole moiety to TTC102 when employed in DSSCs. Dye TTC105, containing a pyridyl group as the electron acceptor, showed only 1.88% conversion efficiency (η) when used in DSSCs. The huge different performances of TTC104 and TTC105 are proved to be partly due to the smaller dye loading amount, higher dark current and charge recombination rate of TTC105.

We demonstrate here for the first time the fabrication of a novel morphology of rutileTiO2 tapered nanotubes with rectangular cross-sections via a facile hydrothermal method using TiO2nanorod as the precursor. A plausible anisotropic corrosion mechanism for the formation of TiO2 nanotubes is also proposed.

We proposed here a temperature-induced solid-phase oriented rearrangement route to the fabrication of NaNbO3 nanowires by using sandia octahedral molecular sieves (SOMS) Na2Nb2O6·H2O as a precursor. The SOMS precursor was prepared by using metal Nb powder as a raw material through the hydrothermal approach.