AbstractMesoporous (Ga1−xZnx)(N1−xOx) hexagonal nanoplates were prepared by nitridation of layered double hydroxides (LDHs) containing Zn2+ and Ga3+ ions with different [Zn]/[Ga] ratios. Their specific surface areas ranged from 21.25 to 50.95 m2/g were much higher than those previously reported. The (Ga1−xZnx)(N1−xOx) showed broad visible light absorption and reduced band gaps with increasing Zn content. When [Zn]/[Ga] = 2, the (Ga1−xZnx)(N1−xOx) absorbed strongly the light of wavelength less than 525 nm and showed the highest visible light driven H2 production efficiency. After totally repeated runs for 30 h, the H2-production activity of (Ga1−xZnx)(N1−xOx) did not fall off, indicating its good photochemical stability and photocatalytic activity for long time. Herein, the results provide new insights into (Ga1−xZnx)(N1−xOx) as high performance photocatalyst and their potential application in visible-light driven water splitting H2 production.

•The efficient rare-earth modification of ZnO could obviously enhance the CH4 and CH3OH yields due to significant increase of CO2 adsorption.•The introduction of CeO2 species to ZnO can significantly promote the selectivity and yield of CH4, while the La and Ce co-modified ZnO effectively increases the catalytic process of CO2 to CH3OH.•The observably increased b-CO3 2− intermediates after Ce modified, which are possible intermediates for the production of CH4.•La and Ce co-modified ZnO catalyst contributed to the formation of CH3OH, which was probably due to that electron separated rapidly transferred to HCO3 - intermediates (directly related to the product of CH3OH).•CO2 molecular react with two active sites, forming b-CO32−, HCO3− intermediates and produce to CH4 and CH3OH after the process of C-O bond breaking and C-H bond formation, respectivelyIn the tide of investigating catalysis process and developing efficient catalysts, the surface properties of catalysts is vitally important, which is lack of due attention in CO2 photoreduction. Herein, a series of Ce modified and La-Ce co-modified ZnO nanorod with varied compositions were synthesized via a simple impregnation route. The efficient rare-earth modification could obviously decrease the light absorption and increased the specific surface. In situ DRIFTS CO2-FTIR results indicated that introduction of appropriate CeO2 can effectively promote CO2 adsorption and the formation of b-CO32− intermediate, which resulted in the 4.2 times increase of the CH4 yields. While, La and Ce co-modified ZnO catalyst contributed to the formation of CH3OH from the mixture of CO2 and H2O. It was probably due to that electron separated rapidly transfered to the surface OH groups, which was directly related to the product of CH3OH. The combined characterizations and photoactivity studies reported in this paper have provided new insights to the role of surface property (surface sites/groups, reaction intermediates) in CO2 photoreduction on semiconductor catalyts, which is of significance but rarely reported.Me+-O− centers or oxygen vacancies are the active sites of CH4 formation, and surface OH groups are closely linked with CH3OH synthesis from CO2 photoreduction. CO2 molecular react with two active sites, forming b-CO32−, HCO3- intermediates and produce to CH4 and CH3OH after the process of CO bond breaking and CH bond formation, respectively.Download full-size image

•Well-defined and structurally stable TiO2 nanofibers segregated by GO were prepared by using electrospinning technique.•The GO sheets were uniformly embedded in the TiO2 nanofibers.•The TiO2/GO composite nanofibers showed enhanced photocatalytic activity under visible light irradiation.•GO sheets in the TiO2 nanofibers facilitated the mobility of charge carriers and enhanced visible light response range.The present study reports the electrospun one-dimensional TiO2/graphene oxide (GO) composite nanofibers photocatalysts using polyvinylpyrrolidone (PVP) as a fiberizing carrier. Continuous TiO2 nanofibers segregated by the well-dispersed GO with the content even high as 5 wt% were obtained after the carrier PVP was burnt away at 500 °C. The observed lower excitonic intensity from photoluminescent study in the TiO2/GO samples than that in bare TiO2 nanofibers indicated that the recombination of photoinduced electrons and holes in TiO2 could be effectively inhibited in the composite nanofibers. Photocatalytic studies suggested that the TiO2/GO composite nanofibers showed higher mobility of charge carriers and enhanced photocatalytic activity than bare TiO2 nanofibers under visible light irradiation. In addition, photocatalytic performance of the TiO2/GO composites nanofibers was enhanced with increasing the GO concentration in the composite nanofibers. The results presented herein provide new insights into TiO2/GO composites materials as high performance photocatalysts with potential uses in environmental remediation.Download high-res image (157KB)Download full-size image

•Develop a facile simple preparation method for perovskite films under the ambient condition.•The surface of the perovskite films exhibits compact uniform morphology.•The PSCs have good photovoltaic performance with compact perovskite as the active layer.The photovoltaic performance of perovskite solar cells is extremely dependent on the crystallization and morphology of the perovskite film, which are affected by the deposition method. Here, we demonstrate a simple approach to form a microporous PbI2 film, with subsequent conversion to a compact, highly crystalline perovskite film. The PbI2 and corresponding perovskite films were further probed by two-dimensional X-ray diffraction. The resultant perovskite exhibited improved photovoltaic performance under ambient conditions with about 50% humidity. The PbI2 microporous structure was formed by exchanging residual DMSO with DMF vapor in the PbI2 film, which facilitated contact with the methylammonium iodide (MAI) solution. The process resulted in the formation of compact, smooth, pinhole-free perovskite films having no residual PbI2. Solar cells fabricated using this methodology exhibited power conversion efficiencies over 16% with negligible photocurrent hysteresis.

•A stretchable sheath-core structural triboelectric fiber (SSCTEF) is developed.•The SSCTEF exhibits high strain/stress sensitivity.•The self-powered sensing mechanism based on a built-in wavy is investigated.•The wearable sensor can detect and discriminate various kinds of motions.While the emerging stretchable electronic sensors have been demonstrated as promising wearable functional devices, challenges in achieving highly stretchable and self-powered fiber-like sensors still exist. Here, a stretchable sheath-core structural triboelectric fiber (SSCTEF) is developed to serve as a self-powered multifunctional kinematic sensor. Owing to the advanced built-in wavy structure design, the fiber-like sensor exhibits an ultrahigh working strain (100%) and demonstrates high sensitivity in response to not only stretching but also to bending and compressing. The working principle of the SSCTEF is verified by the coupling of numerical calculations and experimental measurements. A comprehensive study is carried out to investigate the factors that influence the output performance of the SSCTEF. By wearing, it is capable of detecting and discriminating the joint movements of human bodies. By further weaving and construction, it also shows potential for detecting the deformation in two-dimensional region. This work provides new opportunities for wearable and self-powered sensing fibers with full potential in human motion monitoring.A kinematic sensing fiber that is highly stretchable and self-powered is developed based on a triboelectric sheath-core structure. In which a unique built-in wavy is built in the core fiber and provides controllable electric contact to the intrinsically stretchable sheath fiber tube. The new design offers opportunities for stretchable and active sensing fibers with full potential in human motion monitoring.Download high-res image (152KB)Download full-size image

Lead halide perovskite solar cells with high efficiency have recently attracted tremendous attention. However, the poor stability of perovskite materials has hindered their practical applications. Here, we presented a hydrophobic agent, fluoroalkyl silane, to modify both the light absorbing layer and the hole transport layer. In the presence of a hydrophobic coating, we obtained a stable perovskite solar cell with less hysteresis between the forward sweep and the reverse sweep in air. The effect of fluoroalkyl silane concentration on the stability was investigated; with an optimized 2.0 wt% fluoroalkyl silane solution treatment, the efficiency of perovskite solar cells has reached over 12.0 ± 0.4%. Moreover, for those perovskite solar cells that are exposed to air with about 50% relative humidity, the efficiency was maintained at around 12% for a duration of more than 500 h, while the efficiency of those without hydrophobic coating sharply decreased from about 12% to 1% in a duration of 250 h.

The rapid development of wearable electronics in recent years has brought increasing energy consumption, making it an urgent need to focus on personal energy harvesting, storage and management. Herein, a textile-based personal energy management device with multilayer-coating structure was fabricated by encapsulating commercial nylon cloth coated with silver nanowires into polydimethylsiloxane using continuous and facile dip-coating method. This multilayer-coating structure can not only harvest mechanical energy from human body motion to power wearable electronics but also save energy by keeping people warm without losing heat to surroundings and wasting energy to heat empty space and inanimate objects. Fluoroalkylsilanes (FAS) were grafted onto the surface of the film through one single dip-coating process to improve its energy harvesting performance, which has hardly adverse effect to heat insulation and Joule heating property. In the presence of FAS modification, the prepared film harvested mechanical energy to reach a maximum output power density of 2.8 W/m2, charged commercial capacitors and lighted LEDs, showing its potential in powering wearable electronics. Furthermore, the film provided 8% more thermal insulation than normal cloth at 37 °C and efficiently heated to 40 °C within 4 min when applied the voltage of only 1.5 V due to Joule heating effect. The high flexibility and stability of the film ensures its wide and promising application in the wearable field.Keywords: FAS; heat insulation; personal energy management; triboelectric nanogenetator; wearable heater

•TiO2 submicrospheres (200 nm) with a high surface area were prepared by the hydrothermal method from Ti(SO4)2 and (NH4)2SO4 solution.•By using TiO2 submicrosphere scattering particles on top of semitransparent layer, the power conversion efficiency of DSSCs improved to 9.07%.•Relationship between the efficiency with EIS interfacial resistance of DSSC under 0.1 to 1.0 sun irradiation was analyzed.Hierarchical anatase TiO2 submicrospheres were synthesized by direct hydrothermal method at 120 °C using Ti(SO4)2 and (NH4)2SO4 mixed solution as precursor. The calcined spheres in particle size of 150–200 nm, which consisted of closely connected nanocrystals in a crystallite size of about 24.2 nm and had a relatively high specific surface area of 43.2 m2 g−1 compared to microspheres. In presence of TiO2 submicrospheres as the scattering layer on top of semitransparent layer, the power conversion efficiency of dye-sensitized solar cells (DSSCs) was increased to as high as of 9.07% from 7.24%. This remarkable improvement compared to commercial scattering particles (efficiency of 8.33%) is mainly attributed to their higher surface area for increasing the loading of dye molecule as well as a lower resistance under 1 sun irradiation. The relationship between the conversion efficiency of DSSCs with interfacial resistance under 0.1 to 1.0 sun illumination was further investigated, the decrease of the light power density led to the increase of interfacial resistance. Moreover, even under 0.1 sun irradiation, DSSC still had an efficiency of 7.18% but a slightly lower Voc of 0.597 V.Anatase TiO2 submicrospheres with high surface area were prepared and used for the scattering layer of DSSCs, leading to an efficiency from 7.24% to 9.07%.

•An earth-abundant Ti-doped α-Fe2O3/NiFeOx photoanode was fabricated by spin-coating.•The highest photocurrent 1.13 mA/cm2 at 1.23 V with 55 mV cathode shift was achieved.•EIS indicated the enhanced charge transfer rate comes from improvement of water oxidation.In this article, a novel and facile strategy to load low-cost and earth-abundant oxygen evolution catalyst NiFeOx by spin-coating on Ti-doped α-Fe2O3 films was reported. The NiFeOx modified hematite photoanode was prepared by a two-step process, which consisted of a hydrothermal method and a subsequent NiFeOx loading step. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) were used to characterize the resulting photoanode. The highest photocurrent increment and lowest onset potential were observed with 30 mM NiFe precursor treatment. Increasing the loading content in a range from 10 to 90 mM, the photocurrent density increases from 0.998 for the pristine α-Fe2O3 to 1.126 mA/cm2 at 1.23 V vs RHE (i.e., 12.7% increment) with 30 mM NiFe precursor treatment. Concomitant with this improvement was a cathode shift in the onset potential by nearly 55 mV and higher incident-photon-to-current efficiencies. Hematite photoanodes after NiFeOx deposition showed better performance than pristine samples, because of a lower overpotential for water oxidation resulted from NiFeOx modifying.The α-Fe2O3/NiFeOx composite photoanode was prepared by spin-coating, which achieved photocurrent density as high as 1.126 mA/cm2 at 1.23 V vs RHE.

Graphene nanosheet devices have attracted significant interest in transistor and photodetector applications owing to photothermoelectric effects of graphene. However, their solar energy conversion ability has not been fully explored due to disadvantages of their transparency and zero gap semiconductor in this special field. Here, we propose the potential of graphene-carbon nanotube papers for energy conversion and storage under sunlight and heat. We show that macroscopic 3-dimensional structure of graphene-carbon nanotube papers provides advantages over graphene nanomaterials in converting large area power sources, namely solar and thermal energy into considerable current and voltage. We also report a graphene-carbon nanotube paper stack with p-n interfaces that incorporates a solar/thermal energy cell and a p–n junction capacitor, which can be simultaneously used for energy conversion and storage with a charge-storage capacity of 70.5 μC cm−2 at one sun intensity.

•An alternative way to fabricate DSSC photoanode via liquid phase deposition was presented.•DSSC with TiO2 films first deposited at a higher temperature (80 °C) and subsequently at a lower temperature (60 °C) with an efficiency of 6.51%.•EIS indicated the two-temperature deposited TiO2 film had a lower resistance as well as a longer electronic lifetime.Anatase TiO2 films were directly grown on the conductive glass by liquid phase deposition (LPD) and used as the photoanodes of dye-sensitized solar cells (DSSCs). TiO2 films deposited at a higher temperature had a wider pore size distribution and a perfectly interfacial binding with the conductive FTO layer, while the ones deposited at a lower temperature presented a higher specific surface area to adsorb more dye so that the DSSCs with such two-temperature deposited gradient TiO2 films had the enhanced performance significantly. Moreover, deposition at 80 °C showed a higher deposition rate and TiO2 in the derived films was in a large crystallite size as well as a larger particle size, but a longer duration resulted in some single-crystal particles through the dissolving-precipitation mechanism, which were not suitable to the photoanodes. Thus, gradient TiO2 films were firstly deposited at 80 °C and subsequently at 60 °C for a varying duration to efficiently tune their thickness. The DSSCs with the gradient TiO2 film photoanodes presented a short-circuit current density of 14.9 mA cm−2 and an energy conversion efficiency of 6.51%. For a comparison, LPD TiO2 film without gradient structure was prepared at a fixed temperature (60 °C), which presented a short-circuit current density and photo-to-electric conversion efficiency of 8.78 mA cm−2 and 4.39%, respectively. The electrochemical impedance spectroscopy (EIS) analysis indicated the DSSCs with TiO2 films via two-stage deposition had a lower charge transfer resistance at TiO2/dye/electrolyte interface and a longer electronic lifetime.Gradient TiO2 photoanodes prepared by liquid phase deposition, which gained an efficiency as high as 6.51%.

•An alternative way to fabricate TiO2 nanocrystals for DSSC photoanode via solid state reaction was presented.•The DSSC with an efficiency of 8.16 % was archived by TiO2 well-connected nanocrystals resulted from the decomposition of (NH4)2TiO(SO4)2.•EIS indicated the well connected TiO2 nanocrystals in DSSCs had a lower resistance.TiO2 nanocrystals derived from hydrothermal method were widely used as the photoanodes of dye-sensitized solar cells (DSSCs). Developing some alternative routes combining low-cost with high performance is eagerly expected. Well connected anatase TiO2 nanocrystals were synthesized by one-step thermal decomposition of the double salt (NH4)2TiO(SO4)2 (ammonium titanyl sulfate, ATS) at 700 °C for 2 h, and the fine tuning on aggregate sizes was achieved by adjusting the heating rate. The TiO2 nanocrystals inside the aggregates were densely packed where each nanocrystal contacted well to neighbouring grains. The connected structure between the crystallites decreases the negative effects of electron grain boundary crossing and reduces recombination within the aggregate when used as photoelectrodes of dye-sensitized solar cells. Moreover, TiO2 aggregates from ATS calcined at a faster heating rate (5 °C/min) had a wider pore size distribution and exhibited a higher light scattering abilities, while the ones from those calcined at a slower heating rate (3 °C/min) had a narrow pore size distribution but possessed a higher specific surface area (72.8 m2 g−1) for adsorbing more dye. The DSSC based on two kind of TiO2 nanoparticles as the photoelectrode all exhibited an excellent short-circuit current density (15.21 mA cm−2 and 15.94 mA cm−2) and a highly efficient power conversion efficiency (7.78% and 8.16%). The improvements of power conversion efficiency for two kinds of TiO2 nanoparticles compared to commercial Aerosil process P25 nanoparticles are mainly attributed to a higher light scattering ability and superior dye adsorption property, respectively. The electrochemical impedance spectroscopy (EIS) analysis indicated the DSSCs with TiO2 nanocrystals derived from solid state reaction had a lower charge transfer resistance than all P25 photoanodes at TiO2/dye/electrolyte interface due to the well connected structure provided multiple contacts to neighboring grains.Well connected anatase TiO2 nanocrystals were synthesized by solid state reaction, which had a lower resistance and their DSSCs gained an efficiency as high as 8.16 %.

•Nanofiber with secondary nanostructures improved the TENG performance.•The piezoelectric effect of PVDF nanofibers has been systematically investigated.•Breathable nanofiber meets the user requirements of flexibility and wearability.•Conductive wearable fabrics further enhanced the output power of the TENG.A simple-to-fabricate, high-performance, wearable all-fiber triboelectric nanogenerator (TENG)-based insole composed of electrospun piezoelectric polyvinylidene fluoride (PVDF) nanofibers sandwiched between a pair of conducting fabric electrodes that effectively harvests energy during human walking is reported. The surface of the nanofibers is roughened with secondary nanostructure to enhance insole performance. The maximum output voltage, instantaneous power and output current from the insole reach 210 V, 2.1 mW and 45 μA, respectively. The role of the piezoelectric effect in the electrospun PVDF nanofibers in this TENG-based insole is then systematically investigated. This device is shown to be a reliable power source that can be used to light up 214 serially connected light-emitting diodes directly. The soft fiber-based electric power generator demonstrated in this paper is capable of meeting the requirements of wearable devices because of its efficient energy-conversion performance, high durability, user comfort, and low cost.

The multilaminated ZnO/TiO2 heterojunction films were successfully deposited on conductive substrates including fluorine-doped tin oxide (FTO) glass and flexible indium tin oxide coated poly(ethylene terephthalate) via the layer-by-layer (LBL) self assembly method from the oxide colloids without using any polyelectrolytes. The positively charged ZnO nanoparticles and the negatively charged TiO2 nanoparticles were directly used as the components in the consecutive deposition process to prepare the heterojunction thin films by varying the thicknesses. Moreover, the crystal growth of both oxides could be efficiently inhibited by the good connection between ZnO and TiO2 nanoparticles even after calcination at 500 °C, especially for ZnO which was able to keep the crystallite size under 25 nm. The as-prepared films were used as the working electrodes in the three-electrode photoelectrochemical cells. Because the well-contacted nanoscale heterojunctions were formed during the LBL self-assembling process, the ZnO/TiO2 all-nanoparticle films deposited on both substrates showed remarkably enhanced photoelectrochemical properties compared to that of the well-established TiO2 LBL thin films with similar thicknesses. The photocurrent response collected from the ZnO/TiO2 electrode on the FTO glass substrate was about five times higher than that collected from the TiO2 electrode. Owing to the absence of the insulating layer of dried polyelectrolytes, the ZnO/TiO2 all-nanoparticle heterojunction films were expected to be used in the photoelectrochemical device before calcination.Keywords: all-nanoparticle; heterojunction; layer-by-layer self-assembly; photoelectrochemical; titania; zinc oxide;

•The anatase TiO2 sol with a crystallite size of 3.0 nm was prepared.•Both TiO2 sol and titanium (IV) bis (ammonium lactato) dihydroxide were successfully used towards size-tunable anatase TiO2 nanocrystals.•The DSSC with an efficiency of 9.3% was archived by combining of TiO2 nanocrystals and sol treatment.•Improved interfacial contact was responsible to the performance enhancement of DSSCs.Titanium (IV) bis (ammonium lactato) dihydroxide (TALH) was employed to prepare anatase TiO2 sol where titania in a crystallite size of 3 nm. Both the sol and TALH solution were further subjected to be hydrothermal treated at 200 °C to grow the crystallite size be most appropriate for the photoanodes of dye-sensitized solar cells (DSSCs). The DSSCs with photoanodes derived from the sol-hydrothermal TiO2 exhibited the overall energy conversion efficiency (η) of 7.8%, while the DSSCs with photoanodes derived from the TALH direct hydrothermal (DH) showed a higher η of 8.9%. Moreover, the as-prepared anatase TiO2 sol prior to the hydrothermal treatment was used as substitute for TiCl4 solution to modify the porous DH TiO2 photoanodes, and the DSSCs achieved overall energy conversion efficiency as high as of 9.3%, due to the extremely fine anatase nanocrystals in the TiO2 sol improved the connection between the TiO2 nanocrystals more significantly compared to the TiCl4 treatment.TiO2 nanocrystals derived from aqueous TALH were fabricated as the photoanodes of DSSCs, which gained efficiency as high as 9.3%.

Submicrometer@nano bimodal TiO2 particles consisting of a submicrometer core and a mesoporous structured shell were synthesized by a chemical deposited method. The submicrometer TiO2 particles were first dispersed in the titanium(IV) bis(ammonium lactato) dihydroxide solution in the presence of polyethyleneimine and urea; after reflowing hydrolysis, the suspension was transferred to a Teflon autoclave and subjected to hydrothermal treatment at 150 °C for 24 h. The as-prepared nanocrystal-coated submicrometer TiO2 (NCS-TiO2) showed a core/shell structure where the outer TiO2 nanocrystals with the size of 5 to 7 nm and in anatase phase uniformly coated on the submicrometer TiO2. When the NCS-TiO2 was fabricated as the scattering layer in dye-sensitized solar cells (DSSCs), it adsorbed more dye molecules while still keeping a high light-harvesting efficiency. Moreover, the presence of TiO2 nanocrystals in NCS-TiO2 reduced the sintering stress between the transparent porous layer and the scattering layer, leading to a crack-free and high-quality photoanode film, which also reduced the serial resistance, as verified by electrochemical impedance spectroscopy. Finally, DSSCs with the NCS-TiO2 scattering layer reached an efficiency of 8.36%, which showed a 20% improvement compared with the one without it.

TiO2 microspheres assembled by single crystalline rutile TiO2 nanorods were synthesized by one-pot solvothermal treatment at 180 °C based on an aqueous–organic mixture solution containing n-hexane, distilled water, titanium n-butoxide and hydrochloric acid. The spheres had a radiative structure from the center, and their diameters were controlled in the range from 1 to 5 μm by adjusting the volume of the reactant water. Nitrogen adsorption–desorption isotherms showed that all the as-prepared microspheres had relatively high specific surface areas of about 50 m2 g−1. The 1 μm sized TiO2 nanorod microspheres were fabricated as a scattering overlayer in DSSCs, leading to a remarkable improvement in the power conversion efficiency: 8.22% of the bi-layer DSSCs versus 7.00% for the reference cell made of a single-layer film prepared from nanocrystalline TiO2. Such improvement was mainly attributed to the enhanced light harvesting and dye loading brought by the effective scattering centers.

An anatase TiO2 sol containing ultrafine TiO2 crystallites (ca. 5 nm) was used to fabricate the dye-sensitized solar cells (DSSCs) with a compact layer, which was prepared by the peptization–hydrothermal method using the CF3COOH as peptizing agent. The dried sol was calcined at 300 °C for 1 h to eliminate the organics over the surface of TiO2 and increase the crystallite size of the TiO2 nanocrystals (the special surface area of the calcined TiO2 decreased from 224.7 to 94.9 m2/g); and then it was used to prepare the paste for the porous layer of DSSCs. The compact layer was prepared by the diluted sol through the layer-by-layer (LBL) self assembly technique to control its thickness. The compact films derived from LBL self assembly method not only prevented the charge recombination at the conductor substrate/electrolyte interface but also improved the adhesion between the porous layer and the conductive layer on the substrate, which increased the number of the effective electron pathways with the short distance of the porous layer and consequently resulted in a better electrical contact. The photoelectron conversion efficiency of the DSSCs with the LBL films had increased apparently. In particular, a 12-layer TiO2/PSS LBL film of the DSSC led to a 24.5% increase in the photoelectron conversion efficiency from 5.93 to 7.38%.Graphical abstractHighlights► The nanoparticles in anatase TiO2 sol were ultrafine, uniform sized and highly dispersed. ► The compact layer was prepared by LBL self assembly method, which was dense and comparable to that from physical route. ► The 12-layer LBL film of the DSSC led to a 24.5% increment in the conversion efficiency. ► Both porous layer and the compact layer of the DSSCs were derived from the anatase sol.

Herein we report the direct fabrication of TiO2 subwavelength structures with 1-dimensional TiO2 nanorods on glass substrate through solvothermal process to form self-cleaning antireflection coatings. TiO2 precursor solutions with different solvent constituents create TiO2 nanorods with much different morphologies grown on glass substrates. Apiculate TiO2 nanorods with vertical orientation are grown on the glass substrate which is solvothermally treated in the precursor solution containing ethylene glycol. This glass substrate exhibit the highest transmittance of 70–85% in the range of 520–800 nm and negligible absorption in visible light region (400–800 nm). Furthermore, the TiO2 nanorod arrays show high hydrophobicity and photocatalytic degradation ability which offer the glass substrate self-cleaning properties for both hydrophilic and oily contaminants.Graphical abstractTiO2 nanorod arrays with different morphologies and structures were successfully synthesized on glass substrate by a facile solvothermal process.Highlights► A sample method was used to fabricate TiO2 nanorod arrays on glass substrate. ► Nanorod arrays with different morphology and structure were obtained. ► Hydrophobic and photocatalytic properties resulted in self-cleaning performance.

Commercial resin matrixes of dental composites generally utilize diluents such as triethylene glycol dimethacrylate (TEGDMA) to reduce viscosity. However, the diluents exhibited adverse effects such as higher volume shrinkage and diminished mechanical properties of the dental composites. To overcome these adverse effects, developing of both inorganic fillers and resin monomers is necessary to improve the properties of dental composite. In this work, monodispersed silica microspheres with a diameter of 400 nm were synthesized via the Stöber process. The as-prepared particles were silanized with 3-methacryloxypropyltrimethoxysilane (γ-MPS) and used as fillers. Additionally, ethoxylated bisphenol A dimethacrylate (EBPADMA) with lower viscosity and higher molecular mass was introduced as a base resin monomer, which could be used as resin matrixes with a low amount of diluent. Various resin mixtures of EBPADMA, bisphenol A diglycidyl dimethacrylate (Bis-GMA) and TEGDMA were prepared, which had a similar filler content (71 wt.%), and their mechanical properties, volume shrinkage, depth of cure and light transmission were examined. Among them, the resin mixture containing 70% EBPADMA and 30% TEGDMA exhibited the best compression strength (238.1 ± 5.4 MPa), depth of cure (4.02 ± 0.04 mm) and the lowest volume shrinkage (2.27%).Graphical abstractMonodispersive silica microspheres with a diameter of 400 nm were synthesized and used as fillers to develop a dental composite that has low volume shrinkage.Highlights► Monodispersed SiO2 microspheres with a diameter of 400 nm were synthesized and used as fillers. ► The resin composites using the SiO2 as fillers have a higher light transmission. ► The composite presented a volume shrinkage as low as 2.27% by tuning the resin composition.

The 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions, while the fine one was lower than 100 nm. The 3Y-TZP compact was prepared by dry-pressing under pressures ranged from 10 to 30 MPa and then presintered at 1250 °C for 2 h. The matrix dry-pressed under the pressure of 20 MPa had a porosity of 16.7% and could be easily processed by computer aided design and computer aided manufacturing (CAD/CAM), and which had been infiltrated by the La2O3–Al2O3–SiO2 glass at 1200 °C for 4 h. The flexural strength and fracture toughness of the composite were 710.7 MPa and 6.51 MPa m1/2, respectively. The low shrinkage (0.3%) of the composite can satisfy the net-shape fabrication standard. XRD results illustrated that zirconia in the La2O3–Al2O3–SiO2 glass-infiltrated 3Y-TZP all-ceramic composite was mainly in the tetragonal phase. SEM and EDS results indicated that the pores of the matrix were almost filled by the La2O3–Al2O3–SiO2 glass.

The mechanical properties of dental composites were improved by porous diatomite and nano-sized silica (OX-50) used as co-fillers. The resin composites, filled with silanized OX-50 and silanized diatomite (40:60 wt/wt), presented the best flexural strength (133.1 MPa), elastic modulus (9.5 GPa) and Vickers microhardness (104.0 HV). Besides these, TiO2 nanoparticles were introduced to tune the dental resin composites colours which were valued by the CIE-Lab system. The colour parameters (L⁎, a⁎, b⁎) showed that the colour changes of resin composites could be perceived obviously, when 300–400 nm TiO2 particles were introduced as fillers. The resin composite, filled with 0.5 wt% TiO2, exhibited both clear discolouration (ΔE⁎=3.22) and high mechanical strength. Using scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX), the titanium elemental mapping results indicated that the TiO2 particles were distributed evenly in the prepared dental composites.

The well-dispersive yttrium-stabilized cubic zirconia nanoparticles were fabricated via vapor phase hydrolysis process, and the as-synthesized cubic zirconia nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM) and N2 adsorption–desorption isotherm analysis. The results of XRD indicated that the pure cubic zirconia nanocrystals were obtained with 8 mol% yttrium atoms doping. And SEM and TEM observation showed the yttrium-stabilized cubic zirconia nanoparticles (8 mol% yttrium) were dispersive well, with an average crystallite size of 5 nm. The zirconia coatings were fabricated via the layer by layer (LbL) assembly using poly (allylamine hydrochloride) as polyelectrolyte and cubic zirconia nanoparticles as building blocks in order to illustrate its good dispersity. The quartz substrate coated on both sides with 10 layers of yttrium-stabilized cubic zirconia nanoparticles exhibited transmittance as high as 92.3%, which was decreased only one percent compared with bare quartz substrate. Moreover, the stable super-hydrophilic wetting property of the coating was obtained after a critical number of layers (10 layers) deposited onto the surface of quartz substrate, due to its porous structures.

A solvothermal method for growing 3-dimensional (3D) nanostructured TiO2 films with different morphologies is presented. Nanofibers, nanograss, nanoleaves, and nanoflowers in anatase phase have been successfully fabricated just by adjusting the ratio of solvents. The effects of the solvent on the morphologies of the TiO2 nanostructures are investigated and the formation mechanism is proposed. Photoelectrochemical measurements are used to characterize the photoelectrocatalytic properties. Organic sensing properties based on the catalytic activity are also evaluated by referring to the steady-state photocurrent resulted from photoelectrocatalysis of organic compounds.

Transparent and surfactant-free TiO2 sols containing anatase nanocrystals were prepared by the hydrothermal treatment of water-soluble peroxotitanium acid (PTA) at a temperature of 120 °C. The TiO2 nanocrystals were characterized by transmission electron microscopy (TEM). The TEM results indicated that the TiO2 nanocrystals were nanorod-like with diameters of less than 7 nm after the subsequently hydrothermal treatment. A gradient layer between the transparent fluorine doped SnO2 (FTO) layer and the porous titanium dioxide nanocrystalline film for dye-sensitized solar cells (DSSCs) photoelectrodes, was made with the as-prepared TiO2 sols. The TiO2 gradient layers were characterized by field-emission scanning electron microscopy and UV–vis absorption spectrometry. After the gradient layer deposition on the FTO coated glass, the composite multilayer film exhibited the visible light transmittance of 80% which approached to that of bare FTO glass. The photo-to-electric energy conversion efficiency of the N719 dye-sensitized solar cell had significantly improved from 4.2% to 5.6% in the presence of the compact layer between FTO and the porous TiO2 nanocrystalline film under of AM1.5 illumination (100 mW/cm2). The remarkable improvements in short-circuit current for the DSSCs was due to the effective gradient layer at the FTO–TiO2 interface which prevented direct contact of electrolytes with FTO and consequently reduced charge recombination losses.Graphical abstractDye-sensitized solar cells with TiO2 nanocrystalline porous film in absence of compact film (A) and in presence of compact film in thickness of 1.0 μm (B), 2.5 μm (C), 4.0 μm (D), respectively.Highlights► Anatase TiO2 sols were prepared by the hydrothermal treatment of peroxotitanium acid. ► TiO2 sols were used for DSSC photoelectrode as the compact film on FTO layer. ► The transmittance of the TiO2 compact film on FTO reached 80%. ► The η of DSSCs in the presence of the compact film has improved significantly from 4.2% to 5.6%.

The aim of this study was to investigate the mechanical property effects of co-filling dental resin composites with porous diatomite and nanosized silica particles (OX-50). The purification of raw diatomite by acid-leaching was conducted in a hot 5 M HCl solution at 80 °C for 12 h. Both diatomite and nanosized SiO2 were silanized with 3-methacryloxypropyltrimethoxysilane. The silanized inorganic particles were mixed into a dimethacrylate resin. Purified diatomite was characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and an N2 adsorption–desorption isotherm. Silanized inorganic particles were characterized using Fourier transform infrared spectroscopy and a thermogravimetric analysis. The mechanical properties of the composites were tested by three-point bending, compression and Vicker's microhardness. Scanning electron microscopy was used to show the cross-section morphologies of the composites. Silanization of diatomite and nanosized silica positively reinforced interactions between the resin matrix and the inorganic particles. The mechanical properties of the resin composites gradually increased with the addition of modified diatomite (m-diatomite). The fracture surfaces of the composites exhibited large fracture steps with the addition of m-diatomite. However, when the mass fraction of m-diatomite was greater than 21 wt.% with respect to modified nanosized silica (mOX-50) and constituted 70% of the resin composite by weight, the mechanical properties of the resin composites started to decline. Thus, the porous structure of diatomite appears to be a crucial factor to improve mechanical properties of resin composites.

Large arrays of one-dimensional uniform-sized TiO2 nanofibers (TNFs) were prepared through a template-free method, and used as a working electrode in a transparent microfluidic device made from poly (dimethyl siloxane) (PDMS) to perform efficient photoelectrocatalysis for rapid and undefiled determination of chemical oxygen demand (COD). Photoelectrochemical measurements were used to evaluate the response of TNFs to the intensity of exciting light and the applied potential bias. The photoelectrocatalysis of TNFs in PDMS-based microfluidic device exhibited excellent performance for determination of COD. The practical limit of determination of 0.95 mg/L COD with a working range of 0–250 mg/L was achieved. The relative standard deviation (RSD) was 1.85% for 10 repeated measurements of 0.3 mmol/L glucose with COD value of 57.6 mg/L.

Flaky layered double hydroxides (FLDH) composed of cross-linked nanoflakes were prepared by the reconstruction of their oxides in alkali solution. The effect of reconstruction temperatures on the physicochemical properties was investigated. FLDH with a specific surface area of as high as 217 m2/g was obtained at a reconstruction temperature of 6 °C, and its derived flaky mixed metal oxides (FMMO) had a specific surface area of 249 m2/g. The ZnO nanoparticles were homogeneously deposited on the surface of the FLDH by coprecipitation. After calcination at 500 °C for 2 h, the ZnO-coated FLDH was transformed into ZnO-coated flaky mixed metal oxides (FMMO). The powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, N2 adsorption−desorption isotherm, UV-vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy. In the presence of FLDH as a support, the ZnO nanoparticles were of about 10 nm in size and showed higher photocatalytic decomposition of acid red G than bare ZnO powder prepared under similar experimental conditions. It should be noted that the ZnO-coated FMMO combined excellent adsorption with photocatalytic activity. The flaky structure of mixed metal oxides appears to play important roles in the adsorption and photodecomposition process.

Nanocomposites of magnesium aluminium layered double hydroxides with carbonate anions (Mg–Al–CO3-LDHs) and ZnO nanorods were prepared by a homogeneous precipitation process. The ZnO nanorods give the calcined Mg–Al–CO3-LDHs, strong adsorbents of anionic dyes, photocatalytic activity. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the nanocomposites was investigated by degradation of acid red G in aqueous solution, and the nanocomposite with the ZnO-to-Mg–Al–CO3-LDHs mass ratio of 1:1 had the highest photocatalytic activity in this photocatalytic reaction.

The nanocomposites of magnesium–aluminium–carbonate–layered double hydroxides (Mg–Al–CO3–LDHs) and ZnO nanorods were prepared via a homogeneous precipitation process. The presence of ZnO nanorods made the calcined Mg–Al–CO3–LDHs, the strong adsorptive adsorbents for anions, have a photocatalytic activity. Both Mg–Al–CO3–LDHs and the nanocomposites with various ZnO/Mg–Al–CO3–LDHs mass ratios from 0.5:1 to 3:1 were characterized by X-ray diffraction, transmission electron microscope and UV–vis diffuse reflectance spectra. The nanocomposites quickly adsorbed the anionic dyes such as acid red G (ARG) without the light illumination, and the adsorbed dyes on the recovered nanocomposites were then degraded in a separated photocatalytic reactor. The adsorption ability of the nanocomposites and their photocatalytic activities for the removal of ARG were evaluated by the Fourier transform infrared spectra and UV–vis extinction spectra. The sample at 3:1 ZnO/Mg–Al–CO3–LDHs mass ratio was shown to have higher photocatalytic efficiencies.

The 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions, while the fine one was lower than 100 nm. The 3Y-TZP compact was prepared by dry-pressing under pressures ranged from 10 to 30 MPa and then presintered at 1250 °C for 2 h. The matrix dry-pressed under the pressure of 20 MPa had a porosity of 16.7% and could be easily processed by computer aided design and computer aided manufacturing (CAD/CAM), and which had been infiltrated by the La2O3–Al2O3–SiO2 glass at 1200 °C for 4 h. The flexural strength and fracture toughness of the composite were 710.7 MPa and 6.51 MPa m1/2, respectively. The low shrinkage (0.3%) of the composite can satisfy the net-shape fabrication standard. XRD results illustrated that zirconia in the La2O3–Al2O3–SiO2 glass-infiltrated 3Y-TZP all-ceramic composite was mainly in the tetragonal phase. SEM and EDS results indicated that the pores of the matrix were almost filled by the La2O3–Al2O3–SiO2 glass.

•The substrate of flexible Ti foil as photo-electrode is used.•A suitable process to fabricate the FDSSCs is achieved by using the release agent.•Uniform particles, good density and high porosity are achieved.•The process is in favor of commercialized mass production.Flexible dye-sensitized solar cells (FDSSCs) are dye-sensitized thin-film solar cells constructed on flexible substrate with the advantages of eco-friendly, ease of fabrication, low cost and light weight. FDSSCs exhibit extensive application prospect. Herein, FDSSCs were constructed by the roll-to-roll method using terpineol and silicone oil as the release agent. Three-dimensional profile measurement is taken directly on nanocrystalline-TiO2 photoanodes. The phase composition and surface micro-morphology indicate that relatively large grain sizes and uniform surface of TiO2 particles are obtained. A layer of amorphous SiO2 exists on the nanocrystalline-TiO2 photoanode owing to the release agent (silicon oil), which hinders electrons to travel, thus the photoelectric conversion efficiency is low. However, nanocrystalline-TiO2 photoanodes with uniform particles, good density and high porosity are achieved by using the release agent of terpineol, and the energy conversion efficiency of 2.97% was obtained.

Large arrays of one-dimensional uniform-sized TiO2 nanofibers (TNFs) were prepared through a template-free method, and used as a working electrode in a transparent microfluidic device made from poly (dimethyl siloxane) (PDMS) to perform efficient photoelectrocatalysis for rapid and undefiled determination of chemical oxygen demand (COD). Photoelectrochemical measurements were used to evaluate the response of TNFs to the intensity of exciting light and the applied potential bias. The photoelectrocatalysis of TNFs in PDMS-based microfluidic device exhibited excellent performance for determination of COD. The practical limit of determination of 0.95 mg/L COD with a working range of 0–250 mg/L was achieved. The relative standard deviation (RSD) was 1.85% for 10 repeated measurements of 0.3 mmol/L glucose with COD value of 57.6 mg/L.

Lead halide perovskite solar cells with high efficiency have recently attracted tremendous attention. However, the poor stability of perovskite materials has hindered their practical applications. Here, we presented a hydrophobic agent, fluoroalkyl silane, to modify both the light absorbing layer and the hole transport layer. In the presence of a hydrophobic coating, we obtained a stable perovskite solar cell with less hysteresis between the forward sweep and the reverse sweep in air. The effect of fluoroalkyl silane concentration on the stability was investigated; with an optimized 2.0 wt% fluoroalkyl silane solution treatment, the efficiency of perovskite solar cells has reached over 12.0 ± 0.4%. Moreover, for those perovskite solar cells that are exposed to air with about 50% relative humidity, the efficiency was maintained at around 12% for a duration of more than 500 h, while the efficiency of those without hydrophobic coating sharply decreased from about 12% to 1% in a duration of 250 h.