Examination of Au/SnO2 core-shell architecture nanoparticle for low temperature gas sensing applications

Au/SnO₂ core-shell structure nanoparticles (NPs) were synthesized using two methods, microwave and conventional precipitation. In both cases, the size of the Au core was 12-18 nm and the thickness of the SnO₂ shell was 8-12 nm. The particle size of SnO₂ synthesized using the microwave and precipitation method was 3-5 nm and 1-2 nm, respectively. Upon heating to 400-600 °C, both particles maintained their core-shell morphology but the smaller SnO₂ particles prepared using the precipitation method were more sintered. The resistance changes in films of these particles were measured as a function of CO concentration. The Au/SnO₂ particles prepared using the microwave method showed higher sensor response than those prepared using the precipitation method, even providing a significant signal at testing temperatures approaching ambient conditions, thereby affording a new class of material for gas sensing. Both sets of core-shell particles showed higher sensor response than the SnO₂ nanoparticles. The role of the Au core as a catalyst in improving the adsorption and oxidation of CO gas is important for improving the low temperature response. In addition, the maintenance of the size of SnO₂ in the microwave method during sintering contributed to the higher response towards CO sensing.     

中国微米纳米 花状Au-SnO2复合材料的制备及其对甲醛气敏性能的研究

利用水热法合成了花状SnO2微米材料,并以它作为基体,对其进行Au纳米颗粒修饰,得到了花状Au-SnO2复合材料.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)分析等表征手段对所制备的Au-SnO2复合材料进行了表征分析,结果表明,这种花状结构的材料是由厚度为30 nm～60 nm的SnO2纳米片自组装而成,其尺寸为1 μm～2 μm.同时,我们用花状SnO2和Au修饰的花状SnO2复合材料对1×10-6～500×10-6的甲醛进行了气敏性能测试.结果表明,通过Au修饰,花状SnO2对甲醛的气敏性能有了极大的提高.当甲醛浓度为200×10-6时,其灵敏度(Ra/Rg)约为120,是花状SnO2敏感材料的8倍,表现出很高的响应.另外,由Au修饰的花状SnO2复合材料制成的敏感元件对甲醛表现出良好的选择性.这可能归因于Au纳米颗粒高效的催化活性促进了甲醛气体的扩散和O2的吸附,从而使其表现出更加优异的气敏性能.     

新型Au/TiO_2纳米管的制备及其在化学需氧量测定中的应用研究

该文首次用光电催化的方法,在TiO2纳米管中嵌入金纳米粒子,新材料可以促进界面间电子的传递,有助于电子和空穴对的分离,进而提高光催化效率.对Au/TiO2纳米管进行扫描电子显微镜(SEM),色散型X射线能谱(EDX)和X射线衍射(XRD)表征,结果表明金纳米粒子被成功嵌入TiO2纳米管中,形成蜂窝状结构.将该材料首次用于光电催化法化学需氧量(COD)的测定,发现该传感器的光电流值在1～800mg/L范围内与COD值有良好的线性响应,检测限为0.3 mg/L.利用该传感器测定实际水样的COD值,结果与传统的K2Cr2O7标准方法有较好的一致性.     

金属酞菁负载分子筛对孔雀石绿的降解

采用浸渍法制备了4种负载型金属酞菁催化剂：MCM-41-a-（GH11O）4PeCo（Ⅱ）[Ni（Ⅱ）、Cu（Ⅱ）、Zn（Ⅱ）]。并在室温（25±1℃）中性以及可见光条件下,考察了上述催化剂中心金属、催化剂用量、H2O2浓度以及重复利用方面对孔雀石绿降解速率的影响。研究结果表明：4种催化剂均具有良好的催化性能,在相同条件下,MCM-41-a-（C3H11O）4PcCo的催化效果最好,并且其浓度在0．7g／L（质量为20mg）,H2O2浓度为10mmol／L条件下,孔雀石绿在10min内降解率可达92％。对重复性的研究表明该种负载催化剂具有良好的重复利用性。     

氨基官能化的硅基介孔材料的合成与表征

分别以十六烷基三甲基溴化铵(CTAB)和三嵌段共聚物(P123)为模板剂,正硅酸乙酯(TEOS)为硅源,合成两种硅基介孔材料MCM-41和SBA-15.通过有机硅烷偶连法将3-氨丙基三乙氧基硅烷(APTES)嫁接到已合成的两种介孔材料上,得到氨基官能化的硅基介孔材料.利用XRD、FT-IR、N2吸附-脱附和ICP含量测定对合成的材料进行表征.     

纳米MCM-49分子筛催化二异丙苯烷基转移反应催化性能研究

采用动态水热合成方法制备了纳米MCM-49分子筛,采用XRD、N2吸附-脱附、SEM和FTIR等手段对其结构和酸性进行了表征,考察了纳米MCM-49分子筛催化二异丙苯与苯烷基转移反应的催化性能.研究结果表明,所合成的分子筛为高结晶度的纳米MCM-49分子筛.在二异丙苯与苯的烷基转移反应中,适当提高反应温度、降低空速、降低分子筛硅铝比有利于提高二异丙苯转化率和异丙苯收率.在烷基转移反应温度为200℃,二异丙苯空速为2 h-1条件下,二异丙苯转化率达到86.51%,异丙苯收率接近95%.     

Au催化水煤气变换反应的密度泛函理论研究

应用密度泛函理论(DFT)对Au催化水煤气变换反应的3种可能机理(氧化还原机理、羧基机理、甲酸根机理)进行比较。通过对各个基元反应的反应物、反应中间体、过渡态和产物的研究表明:水煤气变换反应在Au(111)面有3种可能机理,并且每种机理各有2种反应途径.对氧化还原机理来说,反应易按照2个OH的歧化反应进行:对羧基机理来说,反应易按照COOH和OH发生歧化反应进行;对甲酸根机理来说,反应易按照HCOO和OH反应进行。纵观整个反应历程,从活化能比较可知,按甲酸根机理进行的可能性最小,按照羧基机理反应的可能性最大。     

Effect of annealing on the characteristics of Au layers grown on the high-temperature deposited Ni50Fe50 layers

80 nm-thick Ni₅₀Fe₅₀ layers were sputter-deposited on glass substrates at 400 °C and then Au layers were sputter-deposited on the Ni₅₀Fe₅₀ layers. The Au/Ni₅₀Fe₅₀ bilayer films were annealed in a vacuum of 5×10⁻⁴ Pa from 250 to 450 °C for 30 min or 90 min. The characteristics of the Au layers were studied by Auger electron spectroscopy, field emission scanning electron microscopy, X-ray diffraction and a four-point probe technique. When the annealing temperature reaches 450 °C, Fe and Ni atoms diffuse markedly into the Au layer and the Fe content is more than the Ni content. When the annealing temperature is lower than 450 °C, the grain size of the Au layers does not change markedly with annealing temperature. However, as the annealing temperature reaches 450 °C, the annealing promotes the grain growth of the Au layer. As the annealing temperature exceeds 300 °C, the resistivity of the bilayer films increases with increasing annealing temperature. The diffusion of Fe and Ni atoms into the Au layer results in an increase in the resistivity of the annealed bilayer film. Large numbers of Fe and Ni atoms diffusing into the Au layer of the annealed Au/Ni₅₀Fe₅₀ bilayer film lead to a significant decrease in the lattice constant of the Au layer.     

Preparation and CO gas-sensing behavior of Au-doped SnO2 sensors

A study on the low-temperature CO gas sensors based on Au/SnO₂ thick film was reported. Au/SnO₂ powders, with different Au loading from 0.36 to 3.57 wt%, were prepared by a deposition-precipitation method. Thick films were fabricated from Au/SnO₂ powders. The Au/SnO₂ thick-film sensors exhibited high sensitivity to CO gas at relatively low operating temperature (83-210 °C). We also reported the effect of the Au loading in Au/SnO₂ on the CO gas sensing behavior. The optimal Au loading in as-prepared Au/SnO₂ was 2.86 wt%.     

磁控溅射法镀制氮化铝薄膜特性研究

氮化铝薄膜具有高折射率,良好的化学稳定性,耐磨摩、高电阻等特性在微电子器件和光学薄膜中有着广泛地应用.本文研究了反应式磁控溅射方法利用Ar/N2混合气体镀制氮化铝薄膜的工艺过程,实验表明在高真空和高泵浦速率条件下,放电电压直接依赖于反应气体珠浓度.薄膜的折射率,消光系数和薄膜硬度都依赖于氮气浓度的比例.通过工艺研究,找到了氮气在不同浓度下对氮化铝薄膜的折射率,消光系数以及薄膜硬度的影响,找出了镀制氮化镀制氮化铝薄膜的最佳工艺参数.在Ar/N2工作气体中氮气含量保持在40%条件下,用反应式磁控溅射方法,可以精确镀制出良好的氮化铝薄膜,其中折射率范围在2.25~2.4之间,消光系数为10-3,薄膜显微硬度大于20GPa.该薄膜可以广泛应用于微电子器件和光电器件上.