SiO2@CdTe@Au复合纳米粒子的制备与非线性吸收特性

应用SiO₂纳米粒子、CdTe量子点和Au纳米粒子,采用逐层吸附法制备SiO₂@CdTe@Au纳米复合材料。同时对样品进行了测试和表征,从多个方面证明纳米复合材料成功制备。利用Z扫描技术测量了SiO₂@CdTe和SiO₂@CdTe@Au纳米复合材料在纳秒激光脉冲作用下的非线性吸收光学特性。实验结果表明：SiO₂@CdTe和SiO₂@CdTe@Au纳米复合材料均表现出饱和吸收特性。SiO₂@CdTe@Au较SiO₂@CdTe纳米复合材料具有更强的非线性光学特性,并对其机理进行了分析。     

The release of TiO2 and SiO2 nanoparticles from nanocomposites

There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO₂ or amorphous SiO₂ nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO₂ and TiO₂ nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.     

Properties of PWA/ZrO2-doped phosphosilicate glass composite membranes for low-temperature H2/O2 fuel cell applications

Phosphosilicate doped with a mixture of phosphotungstic acid and zirconium oxide (PWA/ZrO₂–P₂O₂–SiO₂) was investigated as potential glass composite membranes for use as H₂/O₂ fuel cell electrolytes. The glass membranes were studied with respect to their structural and thermal properties, proton conductivity, pore characteristics, hydrogen permeability, and performance in fuel cell tests. Thermal analysis including TG and DTA confirmed that the glass was thermally stable up to 400 °C. The dependence of the conductivity on the humidity was discussed based on the PWA content in the glass composite membranes. The proton transfer in the nanopores of the PWA/ZrO₂–P₂O₅–SiO₂ glasses was investigated and it was found that a glass with a pore size of ∼3 nm diameters was more appropriate for fast proton conduction. The hydrogen permeability rate was calculated at various temperatures, and was found to be comparatively higher than for membranes based on Nafion^®. The performance of a membrane electrolyte assembly (MEA) was influenced by its PWA content; a power density of 43 mW/cm² was obtained at 27 °C and 30% relative humidity for a PWA/ZrO₂–P₂O₅–SiO₂ glass membrane with a composition of 6–2–5–87 mol% and 0.2 mg/cm² of Pt/C loaded on the electrode.     

Surface redox polymerized SPEEK–MO2–PANI (M = Si, Zr and Ti) composite polyelectrolyte membranes impervious to methanol

We reported sulfonated poly(ether ether ketone) (SPEEK, 61% degree of sulfonation)–metal oxides (MO₂:SiO₂, TiO₂ and ZrO₂)–polyaniline composite membranes. Metal oxides were incorporated into the swelled SPEEK membrane by sol–gel method and cured by thermal treatment. SPEEK–metal oxide membranes surfaces were modified with polyaniline (PANI) by a redox polymerization process. It was observed that water retention capacity of membrane was increased and methanol permeability was reduced due to synergetic effect of metal oxides and surface modification with polyaniline. These composite membranes showed extremely low methanol permeability (1.9–1.3 × 10⁻⁷ cm² s⁻¹), which was lower than till reported values either for SPEEK–metal oxide or SPEEK/PANI membranes. Relatively high selectivity parameter (SP) values at 343 K of these membranes, especially S–SiO₂–PANI and S–TiO₂–PANI, indicated their great advantages over Nafion117 (N117) membrane for targeting on moderate temperature applications due to the synergetic effect of MO₂ and PANI in SPEEK matrix. S–TiO₂–PANI and N117 showed comparable cell performance in direct methanol fuel cell (DMFC).     

In situ prepared PBSu/SiO2 nanocomposites. Study of thermal degradation mechanism

A series of nanocomposites consisted of poly(butylene succinate) (PBSu) and fumed silica nanoparticles (SiO₂) were prepared using the in situ polymerization technique. The amount of SiO₂ used directly affected the final molecular weight of the prepared polyesters. At a low SiO₂ content (0.5 wt.%) the molecular weight obtained was higher compared to neat PBSu, however at higher concentrations this was gradually reduced. The melting point of the matrix remained unaffected by the addition of the nanoparticles, in contrast to the crystallinity, which was dramatically reduced at higher SiO₂ contents. This was mainly due to the extended branching and cross-linking reactions that took place between the carboxylic end groups of PBSu and the surface silanols of the nanoparticles. Thermal degradation of the PBSu/SiO₂ nanocomposites was studied by determining theirs mass loss during heating. From the variations of the activation energies, calculated from the thermogravimetric curves, it was clear that nanocomposites containing 1 wt.% SiO₂ content had a higher activation energy compared to pure PBSu, indicating that the addition of the nanoparticles could slightly increase the thermal stability of the matrix. However, in PBSu/SiO₂ nanocomposite containing 5 wt.% SiO₂ the activation energy was smaller. This phenomenon should be attributed to the existence of extended branched and cross-linked macromolecules, which reduce the thermal stability of PBSu, rather than to the addition of fumed silica nanoparticles.     

Preparation of KHSO4/SiO2 Nanocomposites and Their Physical Properties

A series of SiO₂/KHSO₄ nanocomposites with various SiO₂/salt ratios was prepared where the active compound was added before gelation. The sol was prepared by mixing of these hydrogen salts, TEOS (tetraethyl orthosilicate) and water. After gelation and heat treatment (heating slowly to 200–220°C under vacuum), the samples were characterized by X-ray diffraction, Differential Scanning Calorimetry (DSC), IR spectroscopy, Scanning Electron Microscopy (SEM), and High Resolution Transition Electron Microscopy (HR TEM). DSC measurements showed phase transition temperature shifts that depended on the SiO₂/salt ratio. The properties of the nanocomposite samples were compared with the bulk materials. The shift in the phase transitions to lower temperatures was attributed to the particle size effect.     

Synthesis and characterization of Fe2O3/SiO2 nanocomposites

Fe₂O₃/SiO₂ nanocomposites based on fumed silica A-300 (S_BET = 337 m²/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)₃) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)₃ then oxidized in air at 400–900 °C. Samples with Fe(acac)₃ adsorbed onto nanosilica and samples with Fe₂O₃/SiO₂ including 6–17 wt% of Fe₂O₃ were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe₂O₃ deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)₃ solution in isopropanol) treated at 500–600 °C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)₃ solution in carbon tetrachloride only α-Fe₂O₃ phase is formed in addition to amorphous Fe₂O₃. The Fe₂O₃/SiO₂ materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15 g/cm³ and S_BET = 265–310 m²/g.     

Novel proton-conductive nanochannel membranes with modified SiO2 nanospheres for direct methanol fuel cells

A novel approach is proposed to prepare a proton-conductive nanochannel membrane based on polyvinylidene difluoride (PVDF) porous membrane with modified SiO₂ nanospheres. The hydrophilic PVDF porous membrane with a 450-nm inner pore size was chosen as the supporting structure. Pristine SiO₂ with a uniform particle size of 95–110 nm was synthesized and functionalized with –NH₂ and –COOH, respectively. Through-plane channels of porous membrane and arranged functional nanoparticles in pores could contribute to constituting efficient proton transfer channels. The characteristics such as morphology, thermal stability, water uptake, dimensional swelling, proton conductivity and methanol permeability as proton exchange membranes, of the SiO₂ nanospheres, and the composite membrane were investigated. The formation of ionic channels in membrane enhanced the water uptakes and proton conduction abilities of the composite membranes. PVDF/Nafion/SiO₂–NH₂ exhibited superior proton conductivities (0.21 S cm^?1) over other samples due to several proton sites and the acid–base pairs formed between –NH₂ and –SO₃H. Furthermore, all the composite membranes exhibited improved methanol resistance compared with Nafion. Therefore, such a design based on porous membrane provided feasibility for high-performance proton exchange membrane in fuel cell applications.     

掺杂纳米SiO2的PVDF-g-PSSA质子交换膜

以聚偏氟乙烯(PVDF)为骨架, 采用溶液接枝苯乙烯磺酸, 合成了掺杂纳米SiO₂颗粒的复合质子交换膜(PVDF/xSiO₂-g-PSSA). 利用红外光谱、热失重分析方法、扫描电镜, 对膜的结构、热稳定性、表面及断面形态进行了表征. 考察了膜的吸水率、电导率、甲醇渗透性等性质. 结果表明, 纳米SiO₂颗粒能提高膜的阻醇性能, 掺杂质量分数10%的适量SiO₂颗粒所得的复合膜的甲醇渗透系数达1.0×10^－7 cm²/s, 低于聚偏氟乙烯接枝苯乙烯磺酸(PVDF-g-PSSA)膜的1.7×10^－7 cm²/s, 仅为Nafion-117的渗透系数的二十分之一. PVDF/10% SiO₂-g-PSSA复合膜具有较高的选择性, 在直接甲醇燃料电池中具有良好的应用前景.     

Novel sepiolite reinforced emerging composite polymer electrolyte membranes for high-performance direct methanol fuel cells

Methanol permeation is the main issue of Nafion membranes when they are used as a polymer electrolyte membrane (PEM) in direct methanol fuel cells (DMFCs). In the current study, novel nanocomposite polymer membranes are prepared by the integration of surface-modified sepiolite (MS) in polyvinylidene fluoride grafted polystyrene (PVDF-g-PS) copolymer as PEM in DMFCs. Sepiolite (SP) surface is chemically modified using vinyltriethoxysilane and analyzed by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Nanocomposite PVDF-g-PS/MS membranes are prepared by phase inversion technique and subsequently treated with chlorosulfonic acid to induce sulfonic acid (SO₃H) active sites at the membrane surface. The prepared nanocomposite membranes (S-PPMS) are analyzed for their physicochemical characteristics in terms of water uptake percentage, cation exchange capacity, proton conductivity (σ), and methanol permeability. MS dispersion in the copolymer matrix is proved through morphological SEM examination. The S-PPMS membranes exhibit increased proton conductivity due to the presence of well-dispersed MS and surface functional –SO₃H groups. A peak power density of 210 mWcm^?2 is recorded for S-PPMS10 at 110 °C, which is higher than the output obtained from Nafion-117. These promising results indicate the potential utilization of prepared nanocomposite PEMs for DMFC application.     

Deposition behaviors and patterning of TiO2 thin films on different SAMs surfaces from titanium sulfate aqueous solution

Patterning of TiO₂ thin films was successfully obtained on different self-assembled monolayers (SAMs) in aqueous solution by micro-contact printing (μCP) method. The substrates were immersed in an aqueous solution containing titanium sulfate (Ti(SO₄)₂) and hydrogen peroxide for deposition at 80 °C. The growth rates on various surfaces were as follows: sulfonic (–SO₃H) > amino (–NH₂) > methyl (–CH₃) > hydroxyl (–OH). According to the XPS results, SAMs with the terminal groups of –SO₃H and –NH₂ were favorable for the deposition. The TiO₂ film deposited on the SAM with the terminal group of –CH₃ could be easily peeled off. Clearly, TiO₂ patterns were obtained on the prepatterned surfaces of –SO₃H/–CH₃ and –NH₂/–CH₃ SAMs. The deposition mechanism might be relevant to electrostatic interaction, Stern layer, lone pair electrons and Van der Vaals forces. The TiO₂ film was anatase after annealing at 500 °C and comprised particles with an average diameter of ca. 10 nm.     

Synthesis and characterization of PAni–SiO2 and PTh–SiO2 nanocomposites' thin films by plasma polymerization

In the present work, we explore the possibility to deposit polyaniline–silicon dioxide (PAni–SiO₂) and polythiophene–silicon dioxide (PTh–SiO₂) nanocomposites through a plasma polymerization route. The films were generated by spraying of mixtures of nano-sized silica particles dispersed in the liquid monomer into a plasma stream of the DC-plasma discharge reactor. The silica in the resulted polymer matrix changes the conduction mechanisms varying from ohmic to ballistic and traps inducing the space charged limited currents (SCLC). The silica modifies the morphology and composition of the deposited films.     

A novel anode supported BaCe0.4Zr0.3Sn0.1Y0.2O3−δ electrolyte membrane for proton conducting solid oxide fuel cells

A novel BaCe_0.4Zr_0.3 Sn_0.1Y_0.2O_3−δ (BSY) electrolyte membrane with thickness of 20 μm was fabricated on NiO-based anode substrate via a one-step all-solid-state method followed by a co-sintering at 1450 °C for 5 h. Chemical stability test demonstrated that BSY electrolyte showed adequate chemical stability against CO₂ and H₂O at intermediate temperature. Besides, the doping of Sn also enhanced the conductivity in humidified hydrogen. With Nd_0.7Sr_0.3MnO_3−σ cathode and hydrogen fuel, the fuel cell generated maximum output of 320, 185 and 105 mW cm⁻² at 700, 650 and 600 °C, respectively. The interfacial resistance of the fuel cell was studied under open circuit conditions and the short-term cell performance also confirmed the stability of BSY electrolyte membrane.     

ZrO2?SiO2 mixed oxides as supports for platinum catalysts

Mixed ZrO₂–SiO₂ oxides were prepared by the sol-gel method and used as supports for platinum catalysts. Activity tests show that Pt/ZrO₂–SiO₂ catalysts can be used in the aromatization of n-heptane.     

High catalytic activity of V2O5-ZrO2 modified with H2SO4 for propene partial oxidation

For V₂O₅–ZrO₂ catalysts, up to 10 mol% the crystalline structure of V₂O₅ was not observed, indicating a good dispersity the surface of ZrO₂. V₂O₅–ZrO₂ catalyst modified with H₂SO₄ exhibited much on higher catalytic activity for propene partial oxidation than unmodified catalysts due to the increased acidity and acid strength of modified catalyst.     

Nonenzymatic electrochemical glucose sensor based on MnO2/MWNTs nanocomposite

In this communication, an amperometric glucose biosensor based on MnO₂/MWNTs electrode was reported. MnO₂ was homogeneously coated on vertically aligned MWNTs by electrodeposition. The MnO₂/MWNTs electrode displayed high electrocatalytic activity towards the oxidation of glucose in alkaline solution, showing about 0.30 V negative shift in peak potential with oxidation starting at ca. −0.20 V (vs. 3 M KCl–Ag/AgCl) as compared with bare MWNTs electrode. At an applied potential of +0.30 V, the MnO₂/MWNTs electrode gives a linear dependence (R = 0.995) in the glucose concentration up to 28 mM with a sensitivity of 33.19 μA mM⁻¹. Meanwhile, the MnO₂/MWNTs electrode is also highly resistant toward poisoning by chloride ions. In addition, interference from the oxidation of common interfering species such as ascorbic acid, dopamine, and uric acid is effectively avoided. The MnO₂/MWNTs electrode allows highly sensitive, low-potential, stable, and fast amperometric sensing of glucose, which is promising for the development of nonenzymatic glucose sensor.     

Influence of Adding SiO2 into ZrO2 on SO2-4/ZrO2 Solid Superacid

用共沉淀法和负载法制备了一系列SO     

Anti-fungal activity of SiO2/Ag2S nanocomposites against Aspergillus niger

Submicron particles of amorphous SiO₂ have been used to grow Ag₂S nanophases at their surfaces. SEM and TEM analysis showed morphological well-defined nanocomposite particles consisting of Ag₂S nanocrystals dispersed over the silica surfaces. These SiO₂/Ag₂S nanocomposites were investigated as anti-fungal agents against Aspergillus niger in different experimental conditions, including as nanofillers in cellulosic fibres. The anti-fungal activity in these composite systems is suggested to result from a synergistic effect due to Ag₂S anti-fungal centres and the SiO₂ surfaces in promoting the adsorption of the fungus.     

The influence of H2SO4 electrolyte concentration on proton transfer resistance of membrane/solution interface

The proton transfer resistance of membrane/solution interface is investigated in this paper by employing H₂SO₄ aqueous solution with different concentration. Two commercial cation exchange membranes, Nafion1135 and PE01 membranes with different ion exchange capacity were selected as test membranes; Proton transfer resistance measurements were made by A.C impedance techniques. The proton transfer resistance of membrane/solution interface increases quickly from 0.059 to 2.22 Ω with the decrease of H₂SO₄ concentration from 2.0 to 0.05 mol/L. The ion exchange capacity of the membrane, or more exactly, the surface charge of the membrane has obviously effect on the membrane/solution resistance due to the formation of electrical double layer (EDL). The effect of electrolyte concentration on membrane/solution interface resistance can be explained by the electrical interactions between ions and charged groups of the membrane: high concentration of ions in the medium can compress the EDL and reduce the electrical interactions between ions and charged groups of the membrane.     

Sol–Gel Chemistry for Ba2+ Sensors to Allow Oil Production Engineered Nanometrically

Work on the development of a Ba^{2 +}-sensitive sol–gel based optical fiber (OF) for use in oil wells is described. The optical fiber (OF) has on its surface a Ba^{2 +} chelating ligand (L) immobilized at a 2–16 wt% loading immobilized in a porous SiO₂ sol–gel host. The authors report sol–gel routes to these SiO₂ and L/SiO₂ nanocomposites and describe their characterization by XPS, fluorescence, NMR, UV-vis and BET methods. They also report on the sol–gel coating and its selectivity to Ba^{2 +}_(aq).