Application of TiO2 nano-particles on the electrode of dye-sensitized solar cells

In this study, nano-TiO₂ thin film electrode and solar cell have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible absorption spectra, contact angle, X-ray photoelectron spectroscopy (XPS), and current-voltage characteristics analyses. X-ray diffraction patterns show that the best sintering temperature of a nano-TiO₂ film is 600 °C, at which TiO₂ anatase phase forms best and the particle size of 8-10 nm can be obtained. The SEM images of a nano-TiO₂ thin film show that the surface of the film is smooth and porous, and the thickness of the nano-TiO₂ film is 4 μm. The measurements of contact angle between nano-TiO₂ film and deionized water (DI water) reveal that the nano-TiO₂ film is super-hydrophilic when solarized under ultraviolet. The electrode of dye-sensitized solar cell is used as a free-base porphyrin with carboxyl group, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) as the sensitizer to adsorb onto the TiO₂ thin film. From the results of ultraviolet-visible absorption spectra and XPS analyses of the electrode, the effects of nano-TiO₂ particles’ addition to the electrode of dye-sensitized solar cell can improve the absorption of visible light (400-700 nm) and increase electrons transferred from TCPP to the conduction band of TiO₂, resulting in the enhancement of efficiency for dye-sensitized solar cells.     

Improving the visible light photocatalytic activity of mesoporous TiO2 via the synergetic effects of B doping and Ag loading

B-doped together with Ag-loaded mesoporous TiO₂ (Ag/B–TiO₂) was prepared by a two-step hydrothermal method in the presence of boric acid, triblock copolymer surfactant, and silver nitrate, followed by heat treatment. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. It was revealed that all samples consist of highly crystalline anatase with mesoporous structure. For Ag/B–TiO₂, B was doped into TiO₂ matrix in the form of both interstitial B and substitutional B while Ag was deposited on the surface of B–TiO₂ in the form of metallic silver. Compared with the single B-doped or Ag-loaded TiO₂ one, mesoporous Ag/B–TiO₂ exhibits much higher visible light photocatalytic activity for the degradation of Rhodamine 6G, which can be ascribed to the synergistic effects of B doping and Ag loading by narrowing the band gap of the photocatalyst and preventing the fast recombination of the photogenerated charge carriers, respectively.     

N, S-doped TiO2 anode effect on performance of dye-sensitized solar cells

The modification of non-metallic elements N and S to nanocrystalline TiO₂ anode results in the energy gap is reduced to 2.63 eV and a strong redshift to the visible region occurred in the UV–visible spectrum. Poly (3-decylthiophene) (P3DT) is synthesized. Ultraviolet–visible spectra (UV–vis) shows that the light absorption of P3DT (Poly (3-decylthiophene)) and N719 (RuL2(NCS)2:2TBA (L=2,2′-bipyridyl-4, 4′-dicarboxylic acid)) are complementary to cover the entire visible region. Solar cell based on N–S/TiO₂ is co-sensitized by P3DT and N719. The photoelectric conversion efficiency of co-sensitized solar cell increases 56.8% comparing with the single dye-sensitized solar cell.     

Double-stranded helical lanthanide(III) supramolecular networks with rigid diimine ligands: Synthesis, structure, and physical properties

Two lanthanide coordination complexes [Nd(NO₃)₃(CH₃OH)₂(4,4′-bipy)₂] (1) (4,4′-bipy=4,4′-bipyridine) and [4,4′-Hbipy][La(NO₃)₄(H₂O)₂(4,4′-bipy)] (2), with a salt of cationic diprotonated 4,4′-bipy, [2(4,4′-H₂bipy)][4(NO₃)] (3), have been identified and isolated from a methanol solution of Ln(NO₃)₃·6H₂O, 4,4′-bipyridine and pyrazine in 1:2:1 ratio. Their structures have been determined by single-crystal X-ray diffraction analyses, which reveal that 1 has an interesting three-dimensional supramolecular architecture containing 2₁ double-stranded helical chains through hydrogen bonding and π–π interactions, while 2 and 3 have well defined infinite chiral 3D open networks that undergo self-interpenetration. The electrospray ionization mass spectra (ESI-MS) indicate that the covalent complex has higher stability than the electrostatic bonding one. ESI-MS/MS of these ions reveal that the Ln–O bond forms a stronger coordinated bonding than that of Ln–N system and the nitrate anion remains bound to the lanthanide centers after complete dissociation in methanol solution.     

Synthesis of hollow microcapsules using SBA-15 sol and their evaluation as a photocatalyst in the decomposition of methyleneblue

A simple and useful route to synthesize mesoporous TiO₂ microcapsules with a hollow macro-core structure was studied. The deposition of hydrophilic precursor sol containing surfactants in the hydrophobic solvents onto the monodispersed polymer surfaces has been applied to produce the mesoporous shells after calcination. Photocatalytic activity of mesoporous TiO₂ was evaluated in aqueous phase degradation of methyleneblue as a test reaction.     

铁和镧共掺杂纳米二氧化钛光催化剂的制备、表征及其光催化活性

以葡聚糖为模板,钛酸四正丁酯、硝酸铁和硝酸镧为前驱体采用模板法制备了一系列铁、镧单掺杂及共掺杂纳米TiO₂光催化剂. 利用SEM、XRD、BET比表面积测定和UV-Vis等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂的样品在紫外和可见光下的光催化性能. TiO₂材料具有较大的比表面积(约150 m²/g),铁和镧共掺杂纳米TiO₂在可见光区域有较强的吸收,在紫外和可见光条件下较纯TiO₂和单掺杂TiO₂对甲基橙溶液具有更好的光催化降解效果,且铁和镧的掺杂量显著影响该材料的催化性能. 当铁掺杂量为0.5mol%、镧掺杂量为0.3mol%,在500 ℃焙烧2 h所得光催化材料的催化性能最佳,焙烧4 h即可使甲基橙的降解率达98.8%,且该复合材料有较高的循环回收利用率,重复使用4次仍可使甲基橙的降解率保持在88%以上.     

Controlled synthesis of cuprous oxide nanospheres and copper sulfide hollow nanospheres

Uniform Cu₂O nanospheres have been successfully synthesized by reducing CuSO₄ with ascorbic acid in sucrose solution at room temperature. The diameter of the Cu₂O nanospheres can be tuned from 90 to 280 nm by adding different amounts of sucrose in the solution. Furthermore, CuS hollow nanospheres with different diameters have been obtained based on the Kirkendall effect using the as-prepared Cu₂O nanospheres as sacrificial templates. Cu₂O/Cu_7.2S₄ core/shell nanospheres and Cu_7.2S₄ hollow nanospheres are obtained as the intermediate products at different stages of the conversion process. Through the post-treatment of sodium citrate solution, Cu_7.2S₄ hollow nanospheres can be changed into CuS hollow nanospheres. The products are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM). Optical properties of the products have also been studied.     

XAS and XPS examination of the Au–S nanostructures produced via the reduction of aqueous gold(III) by sulfide ions

The S L- and Au L₃-edge X-ray absorption fine structure and X-ray photoelectron spectra of nanoscale Au–S products formed via the reduction of aqueous HAuCl₄ by sulfide ions and immobilized onto graphite have been acquired. The TEY XANES and XPS spectra implied the formation of predominant polysulfide species and metallic gold, while the transmission spectra showed Au–S bonding, the share of which increased with increasing molar Na₂S/HAuCl₄ ratio in the reaction solution. The Au–S distances derived from EXAFS analysis changes from 2.31 Å to 2.325 Å with the concentration of sodium sulfide in solution, being longer than that for cuprite-type crystalline Au₂S (2.174 Å). It has been concluded from all the evidence that the surface of gold sulfide decomposes in air and in ultra-high vacuum even before X-ray irradiation.     

Pillaring and photocatalytic properties of mesoporous α-Fe2O3/titanate nanocomposites via an exfoliation and restacking route

Mesoporous α-Fe₂O₃-pillared titanate nanocomposites have been successfully synthesized through an exfoliation−restacking route. Powder X-ray diffraction and N₂ adsorption-desorption isotherms revealed that the α-Fe₂O₃ pillared titanate has an interlayer distance of 3.27 nm, a specific surface area of 66 m²/g and an average pore size of 7.6 nm, suggesting the formation of a mesoporous pillared structure. UV-vis diffuse reflectance spectra show a red shift, indicative of a narrow band gap energy of ∼2.1 eV compared to the host layered titanate, which is essential in creating a visible light photocatalytic activity. The results of degradation of rhodamine B reveal that the present pillared mesoporous composites exhibit better photocatalytic activities than those of the pristine materials under visible irradiation, based on the band gap excitement and the dye-sensitized path, originated from their high surface area, mesoporosity and the electronic coupling between the host and the guest components.     

Spectroscopic and photoluminescence characteristics of Dy ions in lead containing sodium fluoroborate glasses for laser materials

Lead containing calcium zinc sodium fluoroborate (LCZSFB) glasses doped with different concentrations of trivalent dysprosium ions were prepared and investigated by the XRD, FTIR, optical absorption, photoluminescence and decay curve analysis. The experimentally determined oscillator strengths have been determined by measuring the areas under the absorption peaks and the Judd–Ofelt (J–O) intensity parameters were calculated using the least squares fit method. From the evaluated J–O parameters the radiative transition probability rates, radiative lifetimes and branching ratios were calculated for ⁴F_9/2 excited level. Room temperature photoluminescence spectra for different concentrations of Dy³⁺-doped LCZSFB glasses were obtained by exciting the glass samples at 386 nm. The intensity of Dy³⁺ emission spectra increases with increasing concentration of 0.1, 0.25, 0.5 and 1.0 mol% and beyond 1.0 mol% the concentration quenching is observed. The measuring branching ratios are reasonably high for transitions ⁴F_9/2→⁶H_15/2 and ⁶H_13/2, suggesting that the emission at 484 and 576 nm, respectively, can give rise to lasing action in the visible region. From the visible emission spectra, yellow–blue (Y/B) intensity ratios and chromaticity color coordinates were also estimated. The lifetimes of ⁴F_9/2 metastable state for the samples with different concentrations were also measured and discussed.     

Preparation and optical properties of Cu2O hollow microsphere film and hollow nanosphere powder via a simple liquid reduction approach

In this work, we report a simple liquid reduction approach to prepare Cu₂O hollow microsphere film and hollow nanosphere powder with Cu(OH)₂ nanorods as precursor and ascorbic acid as the reductant at 60 °C. When Cu(OH)₂ nanorod array film grown on a copper foil is used as the precursor, Cu₂O thin film made up of hollow microspheres with average diameter of 1.2 μm is successfully prepared. When the Cu(OH)₂ nanorods are scraped from the copper foil and then used as the precursor, Cu₂O hollow nanosphere powder with the average diameter of 270 nm is obtained. The samples are characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and ultraviolet-vis light (UV-vis) absorption spectra. A possible formation mechanism of Cu₂O hollow spheres is discussed.     

Local structure of Mn in (Ga,Mn)As probed by X-ray absorption spectroscopy

Local structure of Mn atoms in Ga_1−xMn_xAs epilayers was studied using the X-ray absorption fine structure (XAFS) at Mn K-edge. X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) techniques were used. XAFS spectra for different Mn sites has been calculated and compared with the experimental data. Multi-parameter fitting of the EXAFS data indicates that 15-25% of Mn atoms are in interstitial sites in the as grown films. The Mn-As bond length has been found longer than Ga-As bond length in GaAs for both substitutional (Mn_Ga) and interstitial (Mn_I) sites.     

Structure and properties of DLC–MoS2 thin films synthesized by BTIBD method

Diamond-like carbon (DLC)–MoS₂ composite thin films were synthesized using a biased target ion beam deposition (BTIBD) technique in which MoS₂ was produced by sputtering a MoS₂ target using Ar ion beams while DLC was deposited by ion beam deposition with CH₄ gas as carbon source. The structure and properties of the synthesized films were characterized by X-ray diffraction, X-ray absorption near edge structure (XANES), Raman spectroscopy, nanoindentation, ball-on-disk testing, and corrosion testing. The effect of MoS₂ target bias voltage, ranging from −200 to −800 V, on the structure and properties of the DLC–MoS₂ films was further investigated. The results showed that the hardness decreases from 9.1 GPa to 7 GPa, the Young?s modulus decreases from 100 GPa to 78 GPa, the coefficient of friction (COF) increases from 0.02 to 0.17, and the specific wear rate coefficient (k) increases from 5×10⁻⁷ to 5×10⁻⁶ mm³ N⁻¹ m⁻¹, with increasing the biasing voltage from 200 V to 800 V. Also, the corrosion resistance of the DLC–MoS₂ films decreased with the raise of biasing voltage. Comparing with the pure DLC and pure MoS₂ films, the DLC–MoS₂ films deposited at low biasing voltages showed better tribological properties including lower COF and k in ambient air environment.     

Preparation and visible light photocatalytic activity of mesoporous N, S-codoped TiO2(B) nanobelts

The mesoporous N, S-codoped TiO₂(B) nanobelts are synthesized via hydrothermal synthesis and post-treatment, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption measurements (BET), X-ray photoelectron spectra (XPS), and UV-vis diffuse reflectance spectra (DRS). The results show that the prepared samples are mesoporous structured and exhibit stronger absorption in the visible light region with red shift in the absorption edge. The photocatalytic activity of N, S-codoped mesoporous TiO₂(B) nanobelts is evaluated by the photocatalytic photodegradation of potassium ethyl xanthate (KEX) under visible light irradiation. It is found that the photocatalytic activity of the prepared samples increases with increasing the molar ratio of thiourea to Ti (R). At R = 3, the photocatalytic activity of the N, S-codoped TiO₂(B) sample TBLTS-3 reaches a maximum value. With further increasing R, the photocatalytic activity of the sample decreases. The high photocatalytic activity of N, S-codoped TiO₂(B) nanobelts can be attributed to the balance between strong absorption in visible light region and low recombination rate of electron/hole pairs.     

Rapid microwave-assisted hydrothermal synthesis of Bi12TiO20 hierarchical architecture with enhanced visible-light photocatalytic activities

Flower-like Bi₁₂TiO₂₀ hierarchical nanostructures composed of numerous nanobelts were synthesized at 180 °C within 1 h by a microwave-assisted hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB) for the first time. The as-prepared products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) absorption spectroscopy. Furthermore, the hierarchical Bi₁₂TiO₂₀ nanostructures exhibited higher photocatalytic activities in the degradation of Rhodamine B under visible-light irradiation than that of the samples prepared without CTAB. In addition, the role of CTAB cationic surfactant has been investigated thoroughly and a possible mechanism is proposed.     

Preparation and photocatalytic property of α-Fe2O3 hollow core/shell hierarchical nanostructures

We report the preparation of a novel kind of α-Fe₂O₃ hollow core/shell hierarchical nanostructures self-assembled by nanosheets. A green precursor powder is first prepared using nontoxic and inexpensive FeCl₃ and urea in ethylene glycol by a surfactant-free solvothermal method at 160 °C for 15 h. The α-Fe₂O₃ hollow core/shell hierarchical nanostructures are obtained by the thermal treatment of the green precursor powder. The as-prepared α-Fe₂O₃ hollow core/shell hierarchical nanostructures are porous, and exhibit a good photocatalytic activity for the degradation of phenol. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).     

Investigation of vanadium–sodium silicate glasses using XANES spectroscopy

X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of (V₂O₅)_x(Na₂O)_0.30(SiO₂)_0.70−x (x < 0.1) glasses obtained by melt-quench technique. The results show no sign of metallic clustering of V atoms, but mixed oxidation states (+4 and +5) of V and strong V3d–O2p hybridization in the glasses. Detailed analysis has revealed that the glass samples contain about 15% V⁴⁺ and 85% V⁵⁺ and the ligand-field splitting is about 1.6 eV.     

The Cu and Te coordination environments in Cu-doped Ge–Te glasses

The structure of Ge₂₀Te₈₀, Ge₁₅Cu₈Te₇₇ and Ge₁₅Cu₅Te₈₀ glasses was investigated by diffraction techniques and extended X-ray absorption fine structure measurements. Large structural models were generated by fitting experimental data by the reverse Monte Carlo simulation technique. In Ge₂₀Te₈₀ glass, both Ge and Te obey the 8−N rule, and the structure is built up of GeTe₄ tetrahedra connected via Te–Te bonding or shared Te atoms connected to two Ge atoms. The coordination number of Te is significantly higher than 2 in Ge₁₅Cu₈Te₇₇. The average coordination number of Cu is 3.41±1 in this alloy. In Ge₁₅Cu₅Te₈₀ glass, Cu binds mostly to Te, while Cu–Cu bonding is significant in Ge₁₅Cu₈Te₇₇.     

Pressure tuned crystal structure in NdBa2Cu3O6+δ superconductor

The high-pressure angle-dispersive X-ray diffraction experiments on the NdBa₂Cu₃O_6+δ superconductor were performed from ambient to above 30 GPa at room temperature. The structure analysis based on the Rietveld refinement methods shows the different pressure dependence for the bond length between the basal-plane copper of the pyramids to the apical oxygen (denoted Cu(2)–O(1)) and bond length between basal-plane copper to plane oxygen (denoted Cu(2)–O(2,3)). The ambient bulk modulus B₀ is derived as 127 GPa. A possible correlation between Cu(2)–O(1) and T_c was discussed.     

Strongly enhanced pinning force density in YBCO–BaTiO3 nanocomposite superconductor

YBa₂Cu₃O_7−δ–BaTiO₃ (4 wt.%) (YBCO–BTO (4%)) composite bulk polycrystalline sample has been synthesized by solid state reaction method. The structure of composite sample has been investigated by X-ray diffraction and magnetization measurements were carried out using MPMS SQUID VSM. The superconducting transition temperature of the YBCO–BTO (4%) sample was similar to that of pure YBCO. The critical current density (J_c) for YBCO–BTO (4%) sample increases significantly as compared to pure YBCO sample. The enhancement of the critical current density in the YBCO–BTO (4%) sample has been attributed to the presence of BaTiO₃ nanoparticles acting as artificial pinning centres. The introduction of BaTiO₃ particles in YBCO increases pinning force density from 0.71 GN/m² to 1.41 GN/m² at 4 K and 0.33 MN/m² to 0.97 MN/m² at 77 K.