Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography

Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work, we used this method to construct nanostructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was investigated. The Pt-Cu-Cu _x O-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The I–V curves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices. Supported by the National Natural Science Foundation of China (Grant No. 90306010), the Program for New Century Excellent Talents in University of China (Grant No. NCET-04-0653), the National Basic Research Program of China (Grant No. 2007CB616911), and the Science and Technology Department of Henan Province (Grant No. 072300420100)     

Growth kinetics of metastable (3 3 1) nanofacet on Au and Pt(1 1 0) surfaces

A theoretical epitaxial growth model with realistic barriers for surface diffusion is investigated by means of kinetic Monte Carlo simulations to study the growth modes of metastable (3 3 1) nanofacets on Au and Pt(1 1 0) surfaces. The results show that under experimental atomic fluxes, the (3 3 1) nanofacets grow by 2D nucleation at low temperature in the submonolayer regime. A metastable growth phase diagram that can be useful to experimentalists is presented and looks similar to the one found for the stationary growth of the bcc(0 0 1) surface in the kinetic 6-vertex model.     

Fabrication of electrode Pt nanotubes for semiconductor capacitors

Template-wetting process was used to fabricate Pt electrode nanotubes for the further application in 3D nanotube capacitors. Anodic alumina oxide (AAO) was used as a template, which can be fabricated by means of two-step anodization process. After the wetting process, released Pt nanotubes have been obtained by selective etching of the template using KOH solution. Pt nanotubes formation and tube walls morphology were investigated by FE-SEM technique. Furnace annealing (FA) effects at temperatures ranging from 200 to 600 °C with 100^oC step on nucleation and crystal growth condition of Pt nanotubes have been examined. Crystallization of the Pt nanotube inside the template has been examined by step-by-step annealing at different temperatures, and confirmed by XRD.     

Structural Characterization of Cis– and Trans–Pt(NH3)2Cl2 Conjugations with Chitosan Nanoparticles

The conjugation of chitosan 15 and 100 KD with anticancer drugs cis– and trans–Pt (NH₃)₂Cl₂ (abbreviated cis–Pt and trans–Pt) were studied at pH 5–6. Using multiple spectroscopic methods and thermodynamic analysis to characterize the nature of drug–chitosan interactions and the potential application of chitosan nanoparticles in drug delivery. Analysis showed that both hydrophobic and hydrophilic contacts are involved in drug–polymer interactions, while chitosan size and charge play a major role in the stability of drug–polymer complexes. The overall binding constants are K_{ch–15–cis–Pt} = 1.44 (±0.6) × 10⁵ M⁻¹, K_{ch–100–cis–Pt} = 1.89 (±0.9) × 10⁵ M⁻¹ and K_{ch–15–trans–Pt} = 9.84 (±0.5) × 10⁴ M⁻¹, and K_{ch–100–trans–Pt} = 1.15 (±0.6) × 10⁵ M⁻¹. More stable complexes were formed with cis–Pt than with trans–Pt–chitosan adducts, while stronger binding was observed for chitosan 100 in comparison to chitosan 15 KD. This study indicates that polymer chitosan 100 is a stronger drug carrier than chitosan 15 KD in vitro.     

无机胶体法制备Pt/C催化剂及其性能表征

采用无机胶体法制备用于质子交换膜燃料电池(PEMFC)的Pt/C催化剂。研究了影响PtO₂胶体生成和稳定性的因素(溶液的pH值、浓度和温度条件等)以及不同还原剂浓度对Pt/C催化剂性能的影响。透射电子显微镜测试结果表明，采用经优化的工艺条件所制备的Pt/C催化剂平均粒径为3 nm，且分散性好、粒度均匀。X-射线衍射分析表明，催化剂中Pt(111)晶面的相对含量较高，有利于加速氧还原反应。单体PEMFC的电压/电流密度曲线测试表明，所制备的Pt/C催化剂具有良好的电化学性能。     

金属间化合物电催化剂Pt1Te1/XC-72的制备及其电催化氧化甲醇性能

以氯铂酸和亚碲酸钠为前驱体,采用两步法在醇水体系下得到负载型Pt1Te1金属间化合物前驱体,通过热处理得到负载型金属间化合物电催化剂Pt1Te1/XC-72.采用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）、电子能谱（EDS）和循环伏安方法（CV）对催化剂进行表征.结果表明：所得产物呈有序金属间化合物Pt1Te1结构,平均粒径4.5nm,在碳载体上具有很好的分散性;负载型金属间化合物电催化剂Pt1Te1/XC-72具有较高的电催化氧化甲醇活性,其优秀的催化氧化甲醇活性与Pt形成金属间化合物后所带来的几何及电子结构改变密切相关.     

二甲醚电氧化及其阳极催化剂研究

Anode electro-catalysts for direct dimethyl-ether fuel cell (DDFC), Pt/C, PtRu/C (1∶1) and PtSn/C (3∶2), were prepared by chemical impregnation-reduction method with formaldehyde as the reductant. DME electro-oxidation and adsorption at Pt electrode and Pt electro-catalysts were investigated by Cyclic Voltammetry(CV), Quasi-steady state polarization and Gas Chromatography(GC). CV showed that there were two current peaks of DME electro-oxidation at Pt electrode around 0.8V (vs RHE); DME was adsorbed at Pt electrode more weakly and slowly than oxygen, methanol, even hydrogen; the onset potential of DME oxidation was 50mV less than that of methanol, and DME peak potential 110 mV lower, thus more advantageous for using in fuel cells than methanol. GC showed that small amount of HCHO was generated during DME electro-oxidation. The mechanism of DME electro-oxidation was proposed. Among the three electro-catalysts (Pt/C, PtRu/C and PtSn/C), Pt alloy catalysts, especially PtRu/C, showed a higher performance toward DME electro-oxidation, as in the case of methanol. Temperature experiments showed that both DME electro-oxidation and adsorption on Pt and Pt alloy catalysts were favored with increased temperature.     

Performance of Pt/SnO2 catalyst in the gas phase hydrogenation of crotonaldehyde

Selective hydrogenation of crotonaldehyde was performed on 5% Pt/SnO₂ catalysts, in gaseous phase, at atmospheric pressure, at 353 K. Two types of catalyst were prepared using H₂PtCl₆ and Pt(NH₃)₄(NO₃)₂ as metallic precursors. Their performances were compared as a function of the reduction temperature and both catalysts were characterised by X-ray diffraction after different reduction treatments. Using the ex-chloride catalyst, the selectivity values to the unsaturated alcohol (UOL) resulted into a maximum of 45% while a selectivity as high as 70–77%, in 0–25% conversion range, was achieved by using ex-nitrate catalyst reduced at 443 K. The formation of Pt–Sn alloy on the metal particles of platinum was thought to be necessary to improve the activity and the selectivity on these catalysts. In the contrast, a presence of PtSn₂ formed at a reduction temperature higher than 473 K led to a decrease of activity and selectivity.     

含贵金属的BaZrO3 储存NOx 催化剂结构及性能研究

A series of perovskite-type BaZrO3 catalysts are prepared by the sol-gel method. Their NOx storage capacity（NSC）and the resistance of SO2 poison are measured. XRD,XPS and FT-IR techniques are also used to characterize their structures and the influence of the structures on performance. The results indicate that,after calcinations at 750 and 900 ℃,the Ba and Zr species mainly exist in the form of perovskite BaZrO3 phase,and the BaCO3 and ZrO2 phases also exist. The presence of bulk nitrate is shown by XRD and FT-IR after BaZrO3 absorbing NOx . The Rh/BaZrO3 is prepared by doping 0.5%Rh on the BaZrO3 with the impregnation method. It is found that the Rh mainly deposits on the surface of catalyst. However,the noble metals 0.5% Rh or Pt well disperse on the surface of the sample after the BaZrO3 is mixed with γ-Al2O3 in equal weight proportion. The structure of perovskite BaZrO3 may be partly broken after doping Rh or Pt,because of the reduction by hydrogen in the process of preparing samples,and then some ZrO2 is enriched on the surface. The BaZrO3 catalysts possess high NSC and high resistance ability of SO2 poison. The NSC of Rh/BaZrO3 decreases compared to that of BaZrO3 . However,the NSC of the samples Pt/BaZrO3/γ-Al2O3 and Rh/BaZrO3/γ-Al2O3 increases by 78% and 15% respectively. It is noticed that the NSC enhances for all the samples containing noble metal Pt or Rh duing the 0.01%SO2 mixed with the NO and O2 . It implies that the NO oxidation is improved by SO2 .     

Tetranuclear Pt<Subscript>2</Subscript>Cu<Subscript>2</Subscript> Complex with a Staircase-Shaped Chain Aggregate in the Solid State

The reaction of the tetranuclear cyanide aquo complex [{Pt(CN)₄Cu(bipy)(H₂O)}₂]· 2H₂O with aqueous ammonia produces the new tetranuclear ammino-containing product [{Pt(CN)₄Cu(bipy)(NH₃)}₂] (1), with terminal cyanide groups and with NH₃ coordinated to the Cu atom. The distorted trigonal bipyramidal coordination about copper in 1 differs from the square-pyramidal coordination present in the starting material. The bipyridine ligand in 1 is nearly perpendicular to the tetranuclear core of the molecule, as opposed to its coplanar disposition in the aquo complex. The two platinum atoms of the tetranuclear core in 1 form Pt···Pt interactions of 3. 2390(8) Å with platinum atoms of neighboring molecules, producing an echelon-shaped supramolecular chain held together by staggered (CN)₄Pt···Pt(CN)₄ linkages, an aggregate structure which does not have a precedent in chemistry derived from the Pt(CN)₄ building block.