Direct In Situ Nitridation of Nanostructured Metal Oxide Deposited Semiconductor Interfaces: Tuning the Response of Reversibly Interacting Sensor Sites

Metal‐oxide nanostructure‐decorated extrinsic semiconductor interfaces modified through in situ nitridation greatly expand the range of sensor interface response. Select metal‐oxide sites, deposited to an n‐type nanopore‐coated microporous interface, direct a dominant electron‐transduction process for reversible chemical sensing, which minimizes chemical‐bond formation. The oxides are modified to decrease their Lewis acidity through a weak interaction to form metal oxynitride sites. Conductometric and X‐ray photoelectron spectroscopy measurements demonstrate that in situ treatment changes the reversible interaction with the analytes NH₃ and NO. The sensor range is extended, which creates a distinct new family of responses determined by the Lewis acidity/basicity of a given analyte relative to that of the nanostructures chosen to decorate the interface. The analyte response, broadened in a substantial and predictable way by nitridation, is explained by the recently developing inverse hard/soft acid/base model (IHSAB) of reversible electron transduction.     

A Factorial Design Approach for Hydrothermal Synthesis of Phase‐Pure AgInO2: A Parametric Optimization Study

Owing to a wide range of industrial applications and fundamental importance, delafossite compounds have gathered tremendous interest in research community. In this study, the formation of hexagonal nanoplates of AgInO₂ mainly dominated by (00l) facets with no metallic Ag impurity, reported using a facile hydrothermal route at 180 °C using KOH as mineralizer by adopting a factorial design approach. Rietveld analysis of the powder XRD pattern and SAED confirms the rhombohedral system of AgInO₂. FE‐SEM image shows a uniform hexagonal plate‐like morphology with an average width of about 300 nm and thickness of 70 nm. XPS and EDX analysis confirm potassium ion free AgInO₂. A specific surface area of about 48.5 m² g^?1 is arrived from N₂ adsorption studies. Temperature‐dependent AC impedance measurements revealed an activation energy of 0.24 eV/f.u. Further, TG‐DTA studies found that the compound is stable in air up to 595 °C.     

Thin film photocatalysis for environmental remediation: A status review

This review accounts, various metal oxide and metal sulfide thin films available for photodegradation of several organic compounds. Due to difficulties in recycling and to avoid rigorous recollection of powder catalysts, the thin film catalyst are gaining rapid attention for photocatalytic applications. The semiconducting thin films are growing as promising photocatalyst for water treatment. This review focuses mainly on the photocatalytic activity of metal oxide thin films in terms of its stability, charge transport and absorption properties. Thin film photocatalyst provides the increased efficiency and cost reduction of device. Furthermore, this review summarizes some key factors regarding the enhancement in photocatalytic performance of thin films.     

Microstructure evolution of room-temperature-sputtered ITO films suitable for silicon heterojunction solar cells

Thickness influence on structural, optical and electrical properties of sputtered indium tin oxide (ITO) with thickness ranging from 60 up to 430 nm films has been studied. At the increase of the film thickness crystallinity degree and grain size increased, whereas tensile structural distortion as well as resistivity decreased. It was observed that a microstructure evolution takes place: the initial amorphous layer evolved in polycrystalline phase, with a grain–subgrain surface morphology. Carrier concentration increased at the increase of the film thickness and a general relationship between electrical characteristics and structural distortion has been found. In thinner films larger tensile distortion allowed to include larger amount of interstitial O and/or Sn atoms in the lattice. An appreciable impact of the thickness was also observed on electro-optical properties in terms of changes in energy gap, resistivity and optical absorption. Silicon heterojunction solar cells have been produced and J_sc as high as 33.0 mA/cm² has been obtained.     

Characterization and catalytic behavior of La2 - x (Sr, Th)xCuO4 ± λ in reaction NO+CO

Two mixed oxide systems La₂-_xSr_xCuO_{4± λ} (0.0⩽x⩽1. 0) and La_2-xTh_xCuO_{4± λ} (O. O⩽x⩽ 0.4) with K₂NiF₄ structure were prepared by varyingx values. Their crystal structures were studied by means of XRD and IR spectra. The average valence of Cu ion at B site, nonstoichiometric oxygen (λ) and the chemical composition in the bulk and on the surface of the catalysts were measured by means of chemical analysis and XPS. The catalytic behavior in reaction CO+NO was investigated under the regular change of average valence of Cu ion at B site and nonstoichiometric oxygen (λ). Meanwhile, the adsorption and activation of the small molecules NO and the mixture of NO+CO over the mixed oxide catalysts were studied by means of MS-TPD. The catalytic mechanism of reaction NO+CO over these oxide catalysts were proposed; and it has been found that, at lower temperatures the activation of NO is the rate determining step and the catalytic activity is related to the lower valent metallic ion and its concentration, while at higher temperatures the adsorption of NO is the rate determining step and the catalytic activity is related to the oxygen vacancy and its concentration. Project supported by the National Natural Science Foundation of China.     

氮掺杂纳米管包覆金属钴催化苯甲醇和苯胺一步N-烷基化反应

通过直接热解三聚氰胺、硝酸钴和葡萄糖混合物制备氮掺杂碳纳米管包覆金属钴催化剂(Co@NCNT).Co@NCNT具有较大的比表面积、均匀的氮分布以及包覆结构.在苯甲醇和苯胺一步法N-烷基化反应中Co@N CNT具有较高的催化活性,且循环4次反应活性没有明显的变化.控制实验和中毒实验表明金属Co和N对催化活性起着重要的作用,同时金属Co是中间产物N-苄叉苯胺加氢的主要活性位.     

柴油机氮氧化物的特征时间模型

本文综合考虑湍流混合、分子扩散的作用,提出了一个新的NO生成计算模型.该模型采用化学动力学时间尺度和湍流时间尺度来考虑化学动力学和湍流混合对NO生成的影响.文中模拟了一台浅盆形燃烧室柴油机,对计算结果和实测结果进行了对比分析.研究表明,新模型计算的NO生成速率与实测结果有较好的一致性.     

FS and FS(OH) defect centers at the MgO(1 0 0) surface: cluster and periodic calculations

We present a model of a new paramagnetic defect center which results from the interaction of atomic hydrogen with the MgO(1 0 0) surface. DFT calculations have been performed using periodic supercells and embedded cluster models where long-range polarization effects are included explicitly. The H atom promotes the creation of an oxygen vacancy (F center) by formation of the F_S⁺(OH⁻) defect where an hydroxyl group is adsorbed near an electron trapped in an oxygen vacancy. This new center has some characteristics similar to those of the classical F_S⁺ centers but a smaller formation energy; furthermore, being globally neutral, it can be treated also with supercell methods.     

低维铁电材料研究进展

铁电材料是一类重要的功能材料,铁电元件的小型化、集成化是当今铁电材料发展的一大趋势.但是尺寸效应、表面效应等的存在制约了传统块体铁电材料在纳米尺度下的应用,因而低维度纳米材料中的铁电性能研究成为当前材料科学领域的研究热点之一.本文综述了近年来理论和实验上关于低维铁电材料的探索,包括二维范德瓦耳斯层状铁电材料、共价功能化低维铁电材料、低维钙钛矿材料、外界调控以及二维"铁电金属"等材料的理论预言与实验铁电性的观测;也提出一些物理新机制来解释低维下的铁电性;最后对该领域今后的发展进行了展望.     

不均匀性:非晶合金的灵魂

非晶合金,即金属玻璃,是一类特殊的由基本化学元素组成的非晶态物质,由于其独特的微观组织结构,展现出了不同于传统晶态合金材料的特殊物性,而成为高性能材料应用领域的重要一员.由于非晶合金的结构无序性,且当前精确表征其微观结构的实验手段缺乏,相应的理论模型也不完善,人们对非晶合金中一些基础物理问题的认识尚且不足,无法形成基本的理论框架来精确地描述其物性产生的微观机理.因而,当前非晶合金研究的核心问题可以概括为:如何建立以微观特征或结构为基础的基本理论框架,准确地概括非晶合金物性的微观机理.在过去几十年里,针对非晶合金的大量研究表明,在非晶合金长程无序的特征中,隐藏着本征的不均匀性和有序,且这些不均匀性的特征与材料物性有着密切的关联,使得建立以不均匀性特征为基础的理论框架成为可能.本文从非晶合金微观特征的不均匀性包括静态不均匀性和动态不均匀性的视角出发,概括性地总结了非晶合金材料与物理研究中取得的丰硕成果,及当前需要关注的重要科学问题,并针对未来可能的研究模式进行了展望.