In situ growth of CuInS2 nanocrystals on nanoporous TiO2 film for constructing inorganic/organic heterojunction solar cells

Inorganic/organic heterojunction solar cells (HSCs) have attracted increasing attention as a cost-effective alternative to conventional solar cells. This work presents an HSC by in situ growth of CuInS₂(CIS) layer as the photoabsorption material on nanoporous TiO₂ film with the use of poly(3-hexylthiophene) (P3HT) as hole-transport material. The in situ growth of CIS nanocrystals has been realized by solvothermally treating nanoporous TiO₂ film in ethanol solution containing InCl₃ · 4H₂O, CuSO₄ · 5H₂O, and thioacetamide with a constant concentration ratio of 1:1:2. InCl₃ concentration plays a significant role in controlling the surface morphology of CIS layer. When InCl₃ concentration is 0.1 M, there is a layer of CIS flower-shaped superstructures on TiO₂ film, and CIS superstructures are in fact composed of ultrathin nanoplates as ‘petals’ with plenty of nanopores. In addition, the nanopores of TiO₂ film are filled by CIS nanocrystals, as confirmed using scanning electron microscopy image and by energy dispersive spectroscopy line scan analysis. Subsequently, HSC with a structure of FTO/TiO₂/CIS/P3HT/PEDOT:PSS/Au has been fabricated, and it yields a power conversion efficiency of 1.4%. Further improvement of the efficiency can be expected by the optimization of the morphology and thickness of CIS layer and the device structure.     

Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method

The morphology and electrical properties of orthorhombic β-WO₃ nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO₃ nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO₃ nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO₃ synthesized at alternative temperatures.     

Efficient decomposition of organic compounds with FeTiO3/TiO2 heterojunction under visible light irradiation

FeTiO₃/TiO₂, a new heterojunction-type photocatalyst working at visible light, was prepared by a simple sol–gel method. Not only did FeTiO₃/TiO₂ exhibit greatly enhanced photocatalytic activity in decomposing 2-propanol in gas phase and 4-chlorophenol in aqueous solution, but also it induced efficient mineralization of 2-propanol under visible light irradiation (λ ≥ 420 nm). Furthermore, it showed a good photochemical stability in repeated photocatalytic applications. FeTiO₃ showed a profound absorption over the entire visible range, and its valence band (VB) position is close to that of TiO₂. The unusually high photocatalytic efficiency of the FeTiO₃/TiO₂ composite was therefore deduced to be caused by hole transfer between the VB of FeTiO₃ and TiO₂.     

Construction of Highly Active Zn3In2S6 (110)/g-C3N4 System by Low Temperature Solvothermal for Efficient Degradation of Tetracycline under Visible Light

Herein, Zn₃In₂S₆ photocatalyst with (110) exposed facet was prepared by low temperature solvothermal method. On this basis, a highly efficient binary Zn₃In₂S₆/g-C₃N₄ was obtained by low temperature solvothermal method and applied to the degradation of tetracycline (TC). The samples of the preparation were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV–vis diffuse reflection spectroscopy, and photoluminescence spectroscopy. Furthermore, the degradation performance of photocatalysts on TC was investigated under different experimental conditions. Finally, the mechanism of Zn₃In₂S₆/g-C₃N₄ composite material degrading TC is discussed. The results show that Zn₃In₂S₆ and Zn₃In₂S₆/g-C₃N₄ photocatalysts with excellent performance could be successfully prepared at lower temperature. The Zn₃In₂S₆/g-C₃N₄ heterojunction photocatalyst could significantly improve the photocatalytic activity compared with g-C₃N₄. After 150 min of illumination, the efficiency of 80%Zn₃In₂S₆/g-C₃N₄ to degrade TC was 1.35 times that of g-C₃N₄. The improvement of photocatalytic activity was due to the formation of Zn₃In₂S₆/g-C₃N₄ heterojunction, which promoted the transfer of photogenerated electron–holes. The cycle experiment test confirmed that Zn₃In₂S₆/g-C₃N₄ composite material had excellent stability. The free radical capture experiment showed that ·O₂⁻ was the primary active material. This study provides a new strategy for the preparation of photocatalysts with excellent performance at low temperature.     

Annealing effect on Sb2S3-TiO2 nanostructures for solar cell applications

Nanostructures composited of vertical rutile TiO₂ nanorod arrays and Sb₂S₃ nanoparticles were prepared on an F:SnO₂ conductive glass by hydrothermal method and successive ionic layer adsorption and reaction method at low temperature. Sb₂S₃-sensitized TiO₂ nanorod solar cells were assembled using the Sb₂S₃-TiO₂ nanostructure as the photoanode and a polysulfide solution as an electrolyte. Annealing effects on the optical and photovoltaic properties of Sb₂S₃-TiO₂ nanostructure were studied systematically. As the annealing temperatures increased, a regular red shift of the bandgap of Sb₂S₃ nanoparticles was observed, where the bandgap decreased from 2.25 to 1.73 eV. At the same time, the photovoltaic conversion efficiency for the nanostructured solar cells increased from 0.46% up to 1.47% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by the annealing treatment.     

Effect of ZnO:Cs2CO3 on the performance of organic photovoltaics

We demonstrate a new solution-processed electron transport layer (ETL), zinc oxide doped with cesium carbonate (ZnO:Cs₂CO₃), for achieving organic photovoltaics (OPVs) with good operational stability at ambient air. An OPV employing the ZnO:Cs₂CO₃ ETL exhibits a fill factor of 62%, an open circuit voltage of 0.90 V, and a short circuit current density of −6.14 mA/cm² along with 3.43% power conversion efficiency. The device demonstrated air stability for a period over 4 weeks. In addition, we also studied the device structure dependence on the performance of organic photovoltaics. Thus, we conclude that ZnO:Cs₂CO₃ ETL could be employed in a suitable architecture to achieve high-performance OPV.     

Femtosecond Carrier Dynamics in In2O3 Nanocrystals

We have studied carrier dynamics in In₂O₃ nanocrystals grown on a quartz substrate using chemical vapor deposition. Transient differential absorption measurements have been employed to investigate the relaxation dynamics of photo-generated carriers in In₂O₃ nanocrystals. Intensity measurements reveal that Auger recombination plays a crucial role in the carrier dynamics for the carrier densities investigated in this study. A simple differential equation model has been utilized to simulate the photo-generated carrier dynamics in the nanocrystals and to fit the fluence-dependent differential absorption measurements. The average value of the Auger coefficient obtained from fitting to the measurements was γ = 5.9 ± 0.4 × 10⁻³¹ cm⁶ s⁻¹. Similarly the average relaxation rate of the carriers was determined to be approximately τ = 110 ± 10 ps. Time-resolved measurements also revealed ~25 ps delay for the carriers to reach deep traps states which have a subsequent relaxation time of approximately 300 ps.     

Side-by-Side In(OH)<Subscript>3</Subscript> and In<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanotubes: Synthesis and Optical Properties

A simple and mild wet-chemical approach was developed for the synthesis of one-dimensional (1D) In(OH)₃ nanostructures. By calcining the 1D In(OH)₃ nanocrystals in air at 250 °C, 1D In₂O₃ nanocrystals with the same morphology were obtained. TEM results show that both 1D In(OH)₃ and 1D In₂O₃ are composed of uniform nanotube bundles. SAED and XRD patterns indicate that 1D In(OH)₃ and 1D In₂O₃ nanostructures are single crystalline and possess the same bcc crystalline structure as the bulk In(OH)₃ and In₂O₃, respectively. TGA/DTA analyses of the precursor In(OH)₃ and the final product In₂O₃ confirm the existence of CTAB molecules, and its content is about 6%. The optical absorption band edge of 1D In₂O₃ exhibits an evident blueshift with respect to that of the commercial In₂O₃ powders, which is caused by the increasing energy gap resulted from decreasing the grain size. A relatively strong and broad purple-blue emission band centered at 440 nm was observed in the room temperature PL spectrum of 1D In₂O₃ nanotube bundles, which was mainly attributed to the existence of the oxygen vacancies.     

A Flower-like In2O3 Catalyst Derived via Metal–Organic Frameworks for Photocatalytic Applications

The most pressing concerns in environmental remediation are the design and development of catalysts with benign, low-cost, and efficient photocatalytic activity. The present study effectively generated a flower-like indium oxide (In₂O₃-MF) catalyst employing a convenient MOF-based solvothermal self-assembly technique. The In₂O₃-MF photocatalyst exhibits a flower-like structure, according to morphology and structural analysis. The enhanced photocatalytic activity of the In₂O₃-MF catalyst for 4-nitrophenol (4-NP) and methylene blue (MB) is likely due to its unique 3D structure, which includes a large surface area (486.95 m² g⁻¹), a wide spectrum response, and the prevention of electron–hole recombination compared to In₂O₃-MR (indium oxide-micro rod) and In₂O₃-MD (indium oxide-micro disc). In the presence of NaBH₄ and visible light, the catalytic performances of the In₂O₃-MF, In₂O₃-MR, and In₂O₃-MD catalysts for the reduction of 4-NP and MB degradation were investigated. Using In₂O₃-MF as a catalyst, we were able to achieve a 99.32 percent reduction of 4-NP in 20 min and 99.2 percent degradation of MB in 3 min. Interestingly, the conversion rates of catalytic 4-NP and MB were still larger than 95 and 96 percent after five consecutive cycles of catalytic tests, suggesting that the In₂O₃-MF catalyst has outstanding catalytic performance and a high reutilization rate.     

Gadolinium oxide nanocrystal nonvolatile memory with HfO2/Al2O3 nanostructure tunneling layers

In this study, Gd₂O₃ nanocrystal (Gd₂O₃-NC) memories with nanostructure tunneling layers are fabricated to examine their performance. A higher programming speed for Gd₂O₃-NC memories with nanostructure tunneling layers is obtained when compared with that of memories using a single tunneling layer. A longer data retention (< 15% charge loss after 10⁴ s) is also observed. This is due to the increased physical thickness of the nanostructure tunneling layer. The activation energy of charge loss at different temperatures is estimated. The higher activation energy value (0.13 to 0.17 eV) observed at the initial charge loss stage is attributed to the thermionic emission mechanism, while the lower one (0.07 to 0.08 eV) observed at the later charge loss stage is attributed to the direct tunneling mechanism. Gd₂O₃-NC memories with nanostructure tunneling layers can be operated without degradation over several operation cycles. Such NC structures could potentially be used in future nonvolatile memory applications.     

Acid-Base Properties of Alumina-Supported M2O3 (M=B, Ga, In) Catalysts

The acid-base properties of -Al₂O₃ and alumina-supported B₂O₃, Ga₂O₃ and In₂O₃ have been determined by microcalorimetry of ammonia and sulfur dioxide adsorption. From the adsorption of NH₃, it was found that the addition of B₂O₃ on alumina leads to an increase of the number of acid sites, while Ga₂O₃ and In₂O₃ additives caused a decrease in the acidity of alumina. Using SO₂ as a probe molecule to study the basicity, the number of surface basic sites on alumina was found to be strongly decreased by the addition of boron oxide, while it was only slightly affected by the addition of gallium oxide and decreased by the addition of indium oxide. The differential heats of adsorption are discussed as a function of the coverage by the probe molecules. The electronic properties of the oxides are examined in order to explain the acid-base properties of the supported oxides.     

Effect of polyvinylpyrrolidone on morphology and structure of In2O3 nanorods by hydrothermal synthesis

Indium oxide (In₂O₃) nanorods were hydrothermally synthesized from aqueous InCl₃ solution in urea with addition of polyvinylpyrrolidone (PVP) as a steric stabilizer. Indium hydroxide, In(OH)₃, was precipitated at 60 °C and was changed into a transient InOOH phase upon calcination at 250 °C in air. X-ray diffractometry revealed that the existence of PVP delays the phase transformation of InOOH. Cubic-structured In₂O₃ phase was then formed when temperature was raised to 350 °C, regardless of the PVP concentration. The In(OH)₃ phase without the PVP showed a rod-based, flower-like morphology of polycrystalline character. Minor addition of the PVP, i.e., 0.1–2 wt.%, resulted in a pronounced evolution in morphology from the three-dimensional, flower-like form to discrete, one-dimensional nanorods aligned in planar form. Both the flower-like and discrete nanorod morphologies were preserved after heat treatments at 250 and 350 °C. This reveals that the morphological change is attributable to preferential adsorption of the PVP molecules on the In(OH)₃ crystallite surface, so that the aggregate attachment responsible for the multipod growth is inhibited.     

V-doped In2O3 nanofibers for H2S detection at low temperature

Pristine and vanadium-doped In₂O₃ nanofibers were fabricated by electrospinning and their sensing properties to H₂S gas were studied. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the inner structure and the surface morphology. The H₂S-sensing performances were characterized at different temperatures ranging from 50 to 170 °C. The sensor based on 6 mol% V-doped In₂O₃ nanofibers exhibit the highest response, i.e. 13.9–50 ppm H₂S at the relatively low temperature of 90 °C. In addition, the fast response (15 s) and recovery (18 s) time, and good selectivity were observed.     

Annealing effect and photovoltaic properties of nano-ZnS/textured p-Si heterojunction

The preparation and characterization of heterojunction solar cell with ZnS nanocrystals synthesized by chemical bath deposition method were studied in this work. The ZnS nanocrystals were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Lower reflectance spectra were found as the annealing temperature of ZnS film increased on the textured p-Si substrate. It was found that the power conversion efficiency (PCE) of the AZO/ZnS/textured p-Si heterojunction solar cell with an annealing temperature of 250°C was η = 3.66%.     

In situ synthesis,mechanical and cyclic oxidation properties of Ti3AlC2/Al2O3 composites

ABSTRACT

Ti₃AlC₂/Al₂O₃ composite materials were successfully fabricated from TiO₂/TiC/Ti/Al powders by the in situ reactive hot pressed technique. The microstructure, mechanical and oxidation properties of the composites were investigated in the paper. Vickers hardness increased with the Al₂O₃ content. The relative density of Ti₃AlC₂/Al₂O₃ composites exhibits a declining tendency with Al₂O₃ content especially exceeds 10 vol.?%. The Ti₃AlC₂/Al₂O₃ composites show excellent electrical conductivity. The flexural strength and fracture toughness of Ti₃AlC₂/10 vol. % Al₂O₃ are 461 ± 20?MPa and 6.2?±?0.2?MPa m^1/2, respectively. The cyclic oxidation behaviour of resistance of Ti₃AlC₂/10 vol. % Al₂O₃ composites at 800–1000°C generally obeys a parabolic law. The oxide scale of sample consists of a mass of α-Al₂O₃ and TiO₂, forming a dense and adhesive protect layer. The result indicates that the Al₂O₃ can greatly improve the oxidation resistance of Ti₃AlC₂.     

ML-WO3/TiO2异质结的制备及其对罗丹明B的光催化降解

采用空间限域法制备了单层三氧化钨纳米片(ML-WO₃),然后将其与TiO₂复合得到ML-WO₃/TiO₂纳米材料,被用来在模拟太阳光下对罗丹明B进行光催化降解。ML-WO₃/TiO₂的组成和光学特性通过扫描电镜、透射电镜、高分辨透射电镜、X射线衍射、紫外-可见吸收光谱和光致发光光谱手段进行表征。结果证实,纳米ML-WO₃/TiO₂克服了纯TiO₂带隙较大的缺陷,在全波段太阳光表现出比ML-WO₃和TiO₂更强的吸收性能,ML-WO₃与TiO₂之间具有明显的协同效应。活性物种捕获实验表明.OH和.O_2^-自由基是RhB降解的主要活性物种。ML-WO₃和TiO₂之间构建的Z型异质结电荷转移路径能够保证光生载流子的高效分离和重组。在5次循环实验后ML-WO₃/TiO₂的光催化活性仍能接近80%,具有良好的光化学稳定性。通过高效液相色谱-质谱检测RhB的中间产物,推测了RhB可能的降解路径。     

The Remarkable Effect of In2O3 on the Catalytic Activity of In/HZSM-5 for the Reduction of NO with CH4

In/HZSM-5/In₂O₃ catalyst that contained two different kinds of In induced by the impregnating and the physical mixing method respectively has shown remarkable activity for the CH₄-SCR of NO _x comparing with In/HZSM-5. The addition of In₂O₃ into In/HZSM-5 improved the NO conversion through enhancing the adsorption of NO _x over In/HZSM-5.     

Synthesis, microstructure, and photocatalysis of In2O3 hollow particles

Indium oxide (In₂O₃) microspheres with hollow interiors have been prepared by a facile implantation route which enables indium ions released from indium-chloride precursors to implant into nonporous polymeric templates in C₂Cl₄ solvent. The templates are then removed upon calcination at 500 °C in air atmosphere, forming hollow In₂O₃ particles. Specific surface area (0.5-260 m² g⁻¹) and differential pore volume (7 × 10⁻⁹ to 3.8 × 10⁻⁴ m³ g⁻¹ Å⁻¹) of the hollow particles can be tailored by adjusting the precursor concentration. For the hollow In₂O₃ particles with high surface area (260 m² g⁻¹), an enhanced photocatalytic efficiency (up to ∼one-fold increase) against methylene blue (MB) dye is obtained under UV exposure for the aqueous In₂O₃ colloids with a dilute solids concentration of 0.02 wt.%.     

Phase diagram of the Al2O3-HfO2-Y2O3 system

The phase diagram of the Al₂O₃-HfO₂-Y₂O₃ system was first constructed in the temperature range 1200-2800 °C. The phase transformations in the system are completed in eutectic reactions. No ternary compounds or regions of appreciable solid solution were found in the components or binaries in this system. Four new ternary and three new quasibinary eutectics were found. The minimum melting temperature is 1755 °C and it corresponds to the ternary eutectic Al₂O₃ + HfO₂ + Y₃Al₅O₁₂. The solidus surface projection, the schematic of the alloy crystallization path and the vertical sections present the complete phase diagram of the Al₂O₃-HfO₂-Y₂O₃ system.     

Accommodation of impurities in α-Al2O3, α-Cr2O3 and α-Fe2O3

Atomic scale computer simulation was used to predict the mechanisms and energies associated with the accommodation of aliovalent and isovalent dopants in three host oxides with the corundum structure. Here we consider a much more extensive range of dopant ions than has previously been the case. This enables a rigorous comparison of calculated mechanism energetics. From this we predict that divalent ions are charge compensated by oxygen vacancies and tetravalent ions by cation vacancies over the full range of dopant radii. When defect associations are included in the model these conclusions remain valid. At equilibrium, defects resulting from extrinsic dopant solution dominate intrinsic processes, except for the largest dopant cations. Solution reaction energies increase markedly with increasing dopant radius. The behaviour of cluster binding energies is more complex.