基于金属氧化物的乙醇检测气敏材料的研究进展

金属氧化物型半导体气体传感器是目前常用的乙醇检测手段,深入研究和改进金属氧化物型半导体材料是提升传感器性能的重要方式。本文首先论述了气敏检测的机理和影响因素,并综述了近年来发展的主要金属氧化物型半导体气敏材料,重点介绍了不同微观结构的Co₃O₄、ZnO、SnO₂及掺杂金属氧化物材料、氧化物异质结等的研究和发展情况,对它们的合成方法、结构特点以及结构与乙醇气敏性能之间的关系进行了探讨。分析表明,减小材料颗粒尺寸、构建大比表面积多孔结构、掺杂和复合改性,是提升金属氧化物材料气敏性能的有效措施。此外,基于传感器微小化的趋势,以微机电系统（MEMS）工艺为基础的微型传感器成为气体传感器的发展趋势。然而,目前针对金属氧化物气敏材料的制备依然缺乏一定的理论指导,气体检测缺乏相应的机理研究,亟需物理、化学、材料等多学科的相互结合,促进乙醇等半导体气体传感器的进一步发展。     

Synthesis and metal coordination of thioether containing cyclo‐ and poly(organophosphazenes)

Several small molecule cyclotriphosphazenes and high polymeric poly(organophosphazenes) with methylthio groups (CH₃SR) have been synthesized: [NP(OCH₂CH₂SCH₃)₂]_n (n = 3, 1; n = 15,000, 5); [NP(OCH₂CH₂CH₂CH₂SCH₃)₂]_n (n = 3, 2; n = 15,000, 6); [NP(OCH₂CH₂CH(SCH₃)CH₂CH₂CH₃)₂]_n (n = 3, 3; n = 15,000, 7); and [NP(OCH₂C₆H₄SCH₃)₂]_n (n = 3, 4; n = 15,000, 8). Both series of compounds possess multiple thioether coordination sites for potential binding to metals. The methylthioethoxide substituent readily oxidizes to the sulfoxide derivatives in the presence of peroxides. All the phosphazenes were characterized by ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy and elemental analysis, and the small molecule cyclotriphosphazenes were examined by mass spectrometry. Gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were also employed to characterize the polymers. Metal complexation and extraction capabilities of both the small molecule and polymeric systems are described. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 650–661, 2000     

导电聚合物复合材料作为超级电容器电极材料

本文综述了基于导电聚合物的复合材料(导电聚合物/碳材料、导电聚合物/金属氧化物材料、导电聚合物/碳材料l金属氧化物材料)作为电极材料在超级电容器中的应用进展,指出将导电聚合物与碳材料或金属氧化物复合,双电层电容与法拉第准电容结合,有机材料与无机材料结合,是超级电容器电极材料研究的重要发展方向.     

The study on the application of solid-state method for synthesizing the polyaniline/noble metal (Au or Pt) hybrid materials

The solid-state method was applied for synthesizing polyaniline (PANI)/noble metal hybrid materials with the presence of HAuCl₄·4H₂O or H₂PtCl₆·6H₂O in the reaction medium. The structure, morphology, and electrochemical activity of the composites were characterized by Fourier transform infrared (FTIR) spectra, UV-visible (vis) absorption spectra, energy dispersive spectrum (EDS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry. The results from FTIR and UV-vis spectra showed that the oxidation degree and doping level of the PANI in composites can be influenced by HAuCl₄·4H₂O and H₂PtCl₆·6H₂O. The EDS data demonstrated that the composites contain a certain amount of Au (or Pt) element. XRD analysis indicated the presence of crystalline-state Au particles in PANI matrix prepared from the presence of HAuCl₄·4H₂O and revealed that the H₂PtCl₆·6H₂O cannot be converted into metal Pt. The TEM and SEM images implied that the Au particles did exist in the polymer matrix with the size of about 20 nm. The enzymeless H₂O₂ sensor constructed with PANI/Au composite from the presence of HAuCl₄·4H₂O showed a short response time (within 5 s) and displayed an excellent performance in wide linear range.     

介孔过渡金属氧化物的合成研究进展

介孔过渡金属氧化物作为一种非硅基介孔材料,在光、电、磁、传感、催化等领域有着潜在的应用价值,是近年来研究的热点。本文主要从合成角度对几种典型的介孔过渡金属氧化物的最新研究进展作了总结,其中包括Ti、W、Nb、Mn、Mo、Ni、Co等。详细阐述了其合成方法、合成过程,也涉及了少量的应用研究,并根据目前合成该类材料所面临的难题,提出了介孔过渡金属氧化物以后的研究方向,即合成具有高热稳定性、孔壁高度结晶以及长程有序的介孔材料。     

活性炭担载金属氧化物用于热煤气脱硫

以热煤气脱硫并回收单质硫为目的,考察了活性炭担载金属氧化物(M/AC)在中温范围150—250℃内,催化氧化硫化氢生成单质硫的研究。担载量1%(质量分数)的M/AC通过等体积浸渍法制得,在固定床上评价了其脱硫活性,并考察了温度、反应气氛等工艺条件对脱硫效果的影响。M/AC脱硫的活性顺序为:Mn/ACCu/ACCe/ACFe/ACCo/ACV/AC。通过DTG分析,硫化氢选择性氧化的主要产物是单质硫。M/AC上金属氧化物起主要的催化作用,催化硫化氢和氧气反应生成单质硫,生成的单质硫被吸附在活性炭的孔道中。     

硬模板法合成晶态介孔金属氧化物研究进展

晶态介孔金属氧化物材料因具有窄的孔径分布、大的比表面积、有序的孔道结构以及高度晶化的孔壁而在工业催化、光电等领域有着广泛的应用.在各种制备方法中,硬模板法因制备方法简单、条件温和、产物孔道结晶度高而受到了广泛关注.对硬模板法中介孔硅模板和介孔碳模板进行了介绍;总结了近年来硬模板法合成氧化铬、氧化铁、氧化铈、氧化镁和氧化钴等晶态介孔材料的研究进展;概述了该材料的发展趋势和应用前景.     

Advances on transition metal oxides catalysts for formaldehyde oxidation: A review

This article highlights recent advances in the development of transition metal-based catalysts for formaldehyde oxidation, particularly the enhancement of their catalytic activity for low-temperature oxidation. Various factors that enhance low-temperature activity are reviewed, such as morphology and tunnel structures, synthesis methods, specific surface area, amount and type of active surface oxygen species, oxidation state, and density of active sites are discussed. In addition, catalyst immobilization for practical air purification, reaction mechanism of formaldehyde oxidation, and the reaction parameters affecting the overall efficiency of the reaction are also reviewed.     

Fluoride ions adsorption from water by CaCO3 enhanced Mn–Fe mixed metal oxides

Novel CaCO₃-enhanced Mn–Fe mixed metal oxides (CMFC) were successfully prepared for the first time by a simple-green hydrothermal strategy without any surfactant or template combined with calcination process. These oxides were then employed as an adsorbent for adsorptive removal of excess fluoride ions. The adsorbent was characterized by SEM, XPS, XRD, FTIR, and BET analysis techniques. The adsorption property of CMFC toward fluoride ion was analyzed by batch experiments. In fact, CMFC exhibited adsorption capacity of 227.3 mg∙g^‒1 toward fluoride ion. Results showed that ion exchange, electrostatic attraction and chemical adsorption were the main mechanism for the adhesion of large amount of fluoride ion on the CMFC surface, and the high adsorption capacity responded to the low pH of the adsorption system. When the fluoride ion concentration was increased from 20 to 200 mg∙L^‒1, Langmuir model was more in line with experimental results. The change of fluoride ion adsorption with respect to time was accurately described by pseudo-second-order kinetics. After five cycles of use, the adsorbent still maintains a performance of 70.6% of efficiency, compared to the fresh adsorbent. Therefore, this material may act as a potential candidate for adsorbent with broad range of application prospects.     

Selective oxidation of ammonia to nitrogen on transition metal containing mixed metal oxides

The selective catalytic oxidation of ammonia to nitrogen (NH₃-SCO) has been studied over hydrotalcite derived mixed metal oxides containing Cu, Co, Fe or Ni. XRD, BET, NH₃-TPD and TPR techniques were used for catalysts characterization. Results of NH₃-SCO were compared with those of selective catalytic reduction of NO with NH₃ (NO-SCR). Reaction mechanism was studied by temperature-programmed surface reaction (TPSR) and activity tests with a various contact time. Catalytic performance of the studied samples depends on both kind and loading of transition metals in the mixed metal oxide system. The Cu-containing samples have been found to be the most active catalysts of the NH₃-SCO process. Transition metal loading strongly influences distribution of ammonia oxidation products. The highest selectivity to N₂ was measured for the catalysts with the lowest transition metal content.     

Porous ceramics based on hybrid inorganic tetrapodal networks for efficient photocatalysis and water purification

The present work demonstrates a very simple and unique strategy for efficient photocatalysis using ZnO ceramic nano- and microtetrapods synthesized by a flame transport synthesis approach. Due to their three-dimensional (3D) morphology, highly porous interconnected networks as flexible ceramics with sufficient mechanical strength can be easily fabricated and efficiently utilized in applications like e.g., photocatalysis, liquid filtering, and membranes. The photocatalytic response can be further enhanced by hybridization of the ZnO tetrapods with different metal oxides which has been explored in detail here. The Cu- and Bi- hybridized ZnO tetrapodal ceramic networks showed the least and highest photocatalytic activities against methylene blue, respectively, whereas, the others exhibited intermediate responses. The observed photocatalytic behaviors of pure and hybrid ZnO tetrapods based flexible ceramic 3D networks are briefly presented and discussed.     

Bioartificial materials based on blends of collagen and poly(acrylic acid)

The interactions between soluble collagen (C) from calf skin and poly(acrylic acid) (PAA) were studied. Mixing aqueous solutions of collagen and PAA, at various pH values (2.5–4), leads to the formation of complexes that precipitate in the form of insoluble aggregates. The effects of mixture composition, pH, and ionic strength on C/PAA complex formation were investigated by gravimetric, turbidimetric, and conductometric analysis. The experimental results indicate that the complexes form through electrostatic interactions. Homogeneous solid films with variable C/PAA ratios were obtained by casting from solutions in which the pH was adjusted just over the isoelectric point of collagen, thus avoiding the attractive ionic interactions responsible for the complexation of collagen and PAA molecules. A relevant result obtained is related to the possibility of restoring the ionic interactions between the two polymers inside the solid films. Mixture composition and pH appear to influence the thermal properties of both complexes and films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 971–976, 1999     

Novel photoinduced phase transitions in transition metal oxides and diluted magnetic semiconductors

Some transition metal oxides have frustrated electronic states under multiphase competition due to strongly correlated d electrons with spin, charge, and orbital degrees of freedom and exhibit drastic responses to external stimuli such as optical excitation. Here, we present photoemission studies on Pr_0.55(Ca_1 − ySr_y)_0.45MnO₃ (y = 0.25), SrTiO₃, and Ti_1 − xCo_xO₂ (x = 0.05, 0.10) under laser illumination and discuss electronic structural changes induced by optical excitation in these strongly correlated oxides. We discuss the novel photoinduced phase transitions in these transition metal oxides and diluted magnetic semiconductors on the basis of polaronic pictures such as orbital, ferromagnetic, and ferroelectric polarons.     

Hybrid materials derived from modified styrene-butadiene-styrene copolymer (SBS) and silica through the sol-gel process

Non-bonded and covalently bonded organic-inorganic hybrids materials, SBS-NO₂/SiO₂, SBS-NH₂/SiO₂ and SBS-Si(OCH₃)₃/SiO₂, were prepared by the sol-gel process using tetraethoxysilane (TEOS) in presence of modified SBS, SBS-NO₂, SBS-NH₂ and SBS-Si(OCH₃)₃, respectively, with HCl as a catalyst. The modified SBS was prepared without damage its molecular weight and chemical structure, which was identified by the means of FTIR spectroscopy, elementary analysis, and Wijs titration. The interfacial force and the properties such as hemical resistance, elongation, thermal stability, and dynamic mechanical properties of the hybrids were investigated in detail.     

Friction and wear characteristics of PTFE composites filled with metal oxides under lubrication by oil

Four kinds of polytetrafluoroethylene(PTFE)-based composites, such as pure PTFE, PTFE+30%(v)PbO, PTFE+30%(v)Pb₃O₄, and PTFE+30%(v)Cu₂O composite, were prepared. The friction and wear properties of these metal oxides filled PTFE composites sliding against GCr15 bearing steel in both dry and lubricated conditions were studied by using an MHK-500 ring-block wear tester. Then the worn surfaces of these PTFE composites and the transfer films of these PTFE composites formed on the surface of GCr15 bearing steel were examined by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of these metal oxide-filled PTFE composites can be greatly improved by liquid paraffin lubrication, and the friction coefficients can be decreased by one order of magnitude. Meanwhile, the interactions between liquid paraffin and metal oxide-filled PTFE composites, especially the absorption of liquid paraffin into the surface layers of these PTFE composites, reduce the mechanical strength and the load-carrying capacity of these metal oxide-filled PTFE composites. This leads to the deterioration of the friction and wear properties of these PTFE composites. Investigations of the frictional surfaces show that Pb₃O₄, Cu₂O, and PbO enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, and thus promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel. Therefore, they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 85–93, 1997     

过渡金属氧化物对烟火药剂的催化作用

为了提高含高氯酸钾和硝酸钾烟火药剂的反应速率,应用混合法和结晶法将过渡金属氧化物（TMO）氧化铁添加到含高氯酸钾的烟火药剂中,将氧化铜添加到含硝酸钾的烟火药剂中。利用绝热加速量热仪（ARC）分别研究了氧化铁对含高氯酸钾烟火药剂、氧化铜对含硝酸钾烟火药剂的催化作用。结果表明,氧化铁对含高氯酸钾的烟火药剂具有催化作用,以结晶添加法催化效果最佳;此药剂的最大反应速率为8.10 min^-1,是不含催化剂药剂的4.09倍;到达最大反应速率时间为8.52 min,比不含催化剂的药剂降低了92.8%。氧化铜对含硝酸钾的烟火药剂具有催化作用,混合法添加的催化效果最佳;此药剂最大反应速率为7.38 min^-1,是不含催化剂药剂的1.30倍;到达最大反应速率时间为53.55 min,比不含催化剂的药剂降低了66.3%。     

Oil swollen surfactant gel based synthesis of metal oxides nanoparticles: An attractive alternative for the conventional sol gel synthesis

Metals (Zr, Zn and Cu) containing oil swollen surfactant gels have been utilized as precursors for the preparation of metal oxides (ZrO₂, ZnO and CuO) nanoparticles. No metal alkoxide, external gelating agent or any other intricate molecule have been utilized to reinforce gelation; gel stage has been achieved simply through judicial adjustment of water to surfactant ratio and salinity of the reaction mixture. Unlike, several previously published reports, in this approach surfactant has been added not to just increase the viscosity of solution but it has also formed rod shaped gelatinous micelles in response to the variation in water to surfactant ratio, which endowed mechanical strength to the gel. The effect of nature of metal salt on mechanical properties of gel has also been investigated. Zn and Cu containing cetyltrimethylammonium bromide (CTAB) gels have been found to be strongest and weakest, respectively. Metal containing CTAB gels were heat treated at various temperatures (600, 700 and 800 °C) in order to obtain metal oxides nanoparticles. The effect of calcination temperature on crystallinity, particle size and morphology of the metal oxides nanoparticles has also been investigated. A comparison between ZrO₂ nanoparticles prepared using conventional sol gel and oil swollen surfactant gel method has also been carried out in terms of crystallinity, particle size and optical property.     

Alkaline earth metal oxides as solid bases for ligand-free Heck reaction

Alkaline earth metal oxides (MO, M = Mg, Ca, Sr and Ba) are investigated as solid bases for ligand-free Heck reaction (Pd concentration: 0.05 mol%). SrO is efficient to promote Heck arylation of styrene with bromobenzene (BB). However, aryl amination of BB to form N,N-dimethylaniline is also observed with SrO. CaO-n particles (n: calcination temperature) are prepared by calcination of dried Ca(NO₃)₂ aqueous solution at 700 or 900 °C. The CaO-n particles outperform other alkaline earth metal oxides considering both BB conversion and selectivity to Heck products. The CaO-900 particles show better performance than the CaO-700 particles. This is attributed to their platelet morphology with sharp edges and corners and the preferential growth along the (1 1 1) crystal plane.     

Thermosensitive and hydrolysis‐sensitive poly(organophosphazenes)

The lower critical solution temperature (LCST) properties and hydrolytic behaviour of thermosensitive biodegradable polyphosphazenes with monomethoxy‐poly(ethylene glycol), glycine ethyl ester and depsipeptide ethyl esters substituents have been studied. All the polymers synthesized show LCST properties. The LCSTs of the polymers are affected by the composition of the polymers and increase with the degradation of the polymers in aqueous solution. The higher content of depsipeptide ethyl esters in the polymers accelerates the LCST change and the degradation of the polymers in aqueous solution. Most polymers synthesized have half‐lives of less than 10 days in neutral solution. © 2002 Society of Chemical Industry