新型甲醛多孔硅复合传感器的制备

构建了一种简便、快速检测甲醛的新型钯-多孔硅(Pd-PS)复合传感器.采用水热腐蚀法制备多孔硅,通过扫描电镜表征其表面微结构.对多孔硅腐蚀条件进行了优化,得出多孔硅的最佳制备条件.多孔硅经化学浸渍法在其表面掺杂金属钯,进而制成了钯-多孔硅复合传感器.当此传感器被置于含甲醛的混合气体中时,可高选择性结合甲醛气体分子,并产生电信号,其强度与甲醛浓度相关,通过万用表检测其电信号,进而分析其气敏性能.检测结果表明,此传感器对甲醛气体敏感,且表现出良好的选择性,对乙醇、氨气、甲醇和丙酮不敏感.此传感器对甲醛浓度的检测范围在0.1～ 6.0 mg/m3之间,检出限为0.1 mg/m3,检测时间为3 min.     

乙醇水蒸气重整Co/CeO2催化剂

 采用共沉淀法制备了Co/CeO2催化剂并将其应用于乙醇水蒸气重整制氢反应,考察了活性组分含量和焙烧温度对催化剂性能的影响. 结果表明,在原料气水∶乙醇∶N2摩尔比为3∶1∶16, 空速为40 L/(g·h)和反应温度为350～600 ℃的条件下, 经650 ℃焙烧的10%Co/CeO2催化剂对乙醇水蒸气重整制氢反应具有高活性和高选择性. 在500 ℃下进行的40 h稳定性测试中,该催化剂上的乙醇转化率始终接近100%, 反应后气体中的H2含量保持在65%左右. X射线衍射表征结果显示,焙烧后催化剂的主要物相组成为Co3O4和CeO2, 二者之间存在相互作用. Co/CeO2催化剂中钴的主要存在形式包括小晶粒的钴氧化物、大晶粒Co3O4和进入CeO2晶格的钴,Co3O4含量和焙烧温度的改变可影响催化剂中钴的存在形式. 由催化剂中高分散小晶粒的钴氧化物还原所得的金属钴是关键的活性组分.     

用于气体传感器的多孔硅的制备方法研究

分别采用化学刻蚀法、电化学腐蚀法和铂助腐蚀法在室温下制备了应用于气体传感器的纳米级多孔硅,并且对其表面形貌及厚度进行了表征。结果表明,3种方法制备的多孔硅孔径从5～100nm不等,并且3种制备方法各具优缺点,可根据实际需要来选择合适的制备方法。     

多孔硅/TiO2纳米线光阳极的制备及其光电催化性能

使用金属辅助化学刻蚀(MACE)法与水热法,改变贵金属粒子的刻蚀时间,制备不同n型多孔硅/TiO_2纳米线光阳极。通过扫描电镜(SEM)和X射线衍射仪(XRD)对光阳极样品进行表征,结果显示多孔硅宏孔的尺寸会随着刻蚀时间延长而增大,由0.1μm变化到0.4μm,多孔硅表面长有TiO_2纳米线为金红石相及少量锐钛矿相。测试结果显示刻蚀35 min的多孔硅/TiO_2样品具有最高的减反射率,在模拟太阳光下具有较高的光电流(光电流密度)活性,且在1.5 V外加偏压下具有最高的光电催化活性。这是由于刻蚀35 min的多孔硅基底具有优异的减反射性能,同时多孔硅与Ti O_2纳米线复合形成光阳极之后具有异质结效应和窗口效应,使得多孔硅/TiO_2纳米线光阳极具有优异光电化学性能。     

脉冲阳极氧化条件对多孔硅法布里-珀罗干涉特性影响

采用电化学脉冲阳极氧化法制备具有干涉效应的多孔硅. 研究电流密度、有效阳极氧化时间、电解液组成对多孔硅法布里-珀罗(F-P)干涉特性的影响, 利用光纤光谱仪测量多孔硅反射光谱并计算其光学厚度. 结果表明, 当阳极氧化电流密度78 mA•cm－2、有效阳极氧化时间5 min、氢氟酸与乙醇体积比VHF∶VEtOH＝2∶1时, 制备的多孔硅法布里-珀罗干涉条纹均匀, 膜层性质稳定; 当与饱和乙醇气体接触时, 多孔硅反射光谱吸收峰位由612红移到637 nm, 光学厚度由5864增加到6296 nm, 表明利用多孔硅法布里-珀罗干涉效应检测乙醇气体思路是可行的.     

V_2O_5/C催化乙二醛氧化为乙醛酸的研究

选用V2O5作为催化剂,活性炭为载体,偏钒酸铵的草酸溶液为浸渍前驱体,采用等体积浸渍法制备了V2O5/C催化剂,将其应用于乙二醛的液相氧化.并对反应液用液相色谱进行了定性,在确定了催化体系中氧化产物的基础上,考察了V2O5含量和焙烧温度对催化剂催化性能的影响,利用XRD和TEM等手段对催化剂进行了表征.结果显示,V2O5含量较低时(w(V2O5)<3%),催化剂的活性组分分散度较高,乙二醛转化率和乙醛酸的选择性都随着V2O5的含量提高而逐渐增加;当负载量为3%时,催化效果最佳,乙二醛转化率和乙醛酸的选择性分别达到16.16%和76.75%;当V2O5的质量分数大于3%时,V2O5颗粒在活性炭表面发生明显聚集,V2O5开始出现多层吸附,导致乙二醛转化率和乙醛酸得率略有下降.而焙烧温度是制备负载型催化剂的一个重要影响因素.焙烧温度的作用不仅在于使活性组分的前驱体充分分解,同时也影响着活性组分的分散状态.我们考察了经不同温度焙烧后的催化剂的活性,从表征结果来看,在473K以下焙烧时,可能活性组分的前驱体未能充分分解,活性中心数目较少,反应效果较差;当V2O5负载量为3%、焙烧温度为573K时,催化剂具有较高的催化活...     

以稀土氧化物为助剂的乙醇水蒸气重整制氢催化剂研究

采用浸渍法,以γ-Al2O3为载体,稀土(Ce,Nd)氧化物为助剂,金属Ni为活性物,制备了用于乙醇水蒸气重整制氢的复合催化剂.该类催化剂在400～550 ℃的较低温度范围内具有较高的氢气产率.不管助剂为何种稀土(Ce,Nd)氧化物,当其含量一定时,活性组分Ni的含量为15%的催化剂均具有最佳活性;当活性组分Ni一定,助剂的含量为10%时,催化剂的产氢率最大.采用10%CeO2/15%Ni/γ-Al2O3催化剂时,乙醇重整制氢的产氢率可达5.2以上.     

微孔多酸CsxH5-xPW10V2O40/SiO2的制备及氧化催化作用

Keggin结构杂多酸在固相体系中的催化作用引起了人们的极大兴趣[1～3].性能稳定的杂多酸铯盐催化剂在非均相催化体系中已有广泛的应用,然而由于其在液固体系中通常呈现牛奶状,难以分离和重新使用,尽管化学家们以各种材料作为这些催化剂的载体进行了许多固载化尝试[4～6],但至今尚未从根本上解决这一难题.因此,开发高比表面的耐水微孔固体杂多酸催化剂是多酸催化化学领域中具有理论和实际意义的课题.本文采用Sol-Gel技术,以正硅酸乙酯(TEOS)为硅源,水解产生的具有网络结构的SiO2凝胶为载体,在钒取代型Keggin结构杂多酸CsxH5-xPW10V2O40存在下,制得通式为CsxH5-xPW10V2O40/SiO2的固体双功能微孔杂多酸; 以30%H2O2为氧化剂,以苯甲醇氧化为模型反应,研究其液-固体系中的催化作用.     

Cu/V2O5-TiO2/SiO2上光催化CO2和丙烷合成异丁烯醛反应性能的研究

采用表面改性法和等体积浸渍法制备了金属修饰的负载型复合半导体材料Cu/V2O5-TiO2/SiO2，用X射线衍射、比表面测定、红外光谱、拉曼光谱、紫外可见漫反射等技术对固体材料的结构、吸光性能和化学吸附性能进行了表征；研究了该材料对CO2和丙烷合成异丁烯醛的光促表面催化规律。结果表明，半导体活性组分V2O5和TiO2在所制备的催化剂Cu/V2O5-TiO2/SiO2表面形成化学键联，并存在多种活性吸附位；金属Cu的修饰拓展了固体材料对光源的响应范围，提高了反应体系的吸光能力；固体材料对CO2和丙烷的有效吸附使得其在较低温度下能促进异丁烯醛的紫外光化学合成。根据实验结果，对光促CO2和丙烷表面催化合成异丁烯醛的机理进行了讨论。     

湿化学法制备硅纳米线阵列及其光电化学产氢性能分析

为了探究不同方法条件下制备的硅纳米线阵列电极产氢性能异同,文中分别采用了两步金属辅助催化无电刻蚀法、一步金属辅助催化无电刻蚀法以及阳极氧化法来制备硅纳米线阵列用作为光电分解水电池光阴极材料.通过FESEM、XRD和UV-Vis-IRDRS等手段对实验样品的形貌、晶型、减反性表征,发现相比于其他2种方法所得硅纳米线样品,两步金属辅助催化无电刻蚀法制备的硅纳米线结构晶型保持更好,表面缺陷更少.光电化学测试表明两步金属辅助催化无电刻蚀法制备的硅纳米线光电化学性能表现最优,其光电流密度值是一步法的4倍,阳极氧化法的40倍;转移电荷电阻仅是一步法制备的硅纳米线阵列阻值的1/3,阳极氧化法制备的1/1000.     

Fabrication of highly antireflective silicon surfaces with superhydrophobicity

Highly antireflective porous silicon surfaces with superhydrophobicity were obtained by means of chemical etching and fluoroalkylsilane self-assembly. The results show that wettability and reflectivity of these surfaces strongly depend on the etching method and the resultant surface morphology. All of the four resultant porous silicon surfaces by alkaline etching, acidic etching, thick Pt-assisted acidic etching, and thin Pt-assisted acidic etching can reduce reflectance, but the efficiency differs greatly. Except for the alkaline etching, the porous silicon surfaces produced by the other three etching methods can reach superhydrophobicity after fluoroalkylsilane modification. These differences are due to the different surface morphology and roughness. Moreover, the porous silicon surface produced by thin Pt-assisted acidic etching presents abundant holes and particles with diameters ranging from nanometers to submicrometers. This morphology enables the porous silicon surface to own a very low reflectance value that is averaged to be about 3% over the whole experimental photon wavelength spanning 300-800 nm.     

A model of the mechanism of the chemical interaction of the etchant ion (HF<Subscript>2</Subscript>)<Superscript>–</Superscript> with silicon during its electrochemical etching in hydrofluoric acid solutions

A model was proposed for the mechanism of the chemical interaction of the etchant ion (HF₂)^– with silicon during its electrochemical etching, which explains the possibility of porous silicon etching in the dark and the formation of hydride and hydroxyl groups on the silicon surface.     

Bismuth spheres grown in self-nested cavities in a silicon wafer

We have developed a one-step, hydrofluoric acid-free hydrothermal etching method that not only produces bismuth nano/micrometer-sized spheres but also prepares porous silicon with vertical holes. By controlling the heating temperature and time, nanoscale vertical-channeled porous silicon can be received. Our result indicated that the Bi clusters were formed first on the wafer surface. Then the etching of the Bi to the wafer creates the holes. Later, the Bi spheres went into the holes and expedited the etching process. A formation mechanism and chemical process have been proposed on the basis of experimental data. This simple chemistry approach may be of great scientific and technological importance for preparing porous silicon wafer.     

One-step Fabrication of Nanoporous Black Silicon Surfaces for Solar Cells using Modified Etching Solution

Currently, a conventional two-step method has been used to generate black silicon (BS) surfaces on silicon substrates for solar cell manufacturing. However, the performances of the solar cell made with such surface generation method are poor, because of the high surface recombination caused by deep etching in the conventional surface generation method for BS. In this work, a modified wet chemical etching solution with additives was developed. A homogeneous BS layer with random porous structure was obtained from the modified solution in only one step at room temperature. The BS layer had low reflectivity and shallow etching depth. The additive in the etch solution performs the function of pH-modulation. After 16-min etching, the etching depth in the samples was approximately 200 nm, and the spectrum-weighted-reflectivity in the range from 300 nm to 1200 nm was below 5%. BS solar cells were fabricated in the production line. The decreased etching depth can improve the electrical performance of solar cells because of the decrease in surface recombination. An efficiency of 15.63% for the modified etching BS solar cells was achieved on a large area, p-type single crystalline silicon substrate with a 624.32-mV open circuit voltage and a 77.88% fill factor.     

Chemical etching of silicon: Smooth, rough, and glowing surfaces

Scanning Force Microscope images of silicon surface morphology are presented for samples exposed to various oxidizing environments followed by oxide removal. These are contrasted with samples exposed to HNO₃/HF solutions. The former samples consistently produced surface roughness on the order of a few nanometers, while the latter solution exhibited surface roughness of several hundred to over a thousand nanometers. This rough surface is photoluminescent and is known as porous silicon. Careful observation of the onset of the reaction (which is proceeded by a concentration dependent induction period) suggests that the reaction mechanism is autocatalytic; some etchant product species catalyzes the further attack of the surface. Surface features of co-existing fluorescing and non-fluorescing regions emphasize the heavy etching present in the porous silicon region. Local control of the porous silicon formation by a photoinduced etching process is reported for the first time suggesting the possibility of a non-resist lithographic procedure.     

The enhancement of photoluminescence of n-type porous silicon by Hall-effect assistance during electrochemical anodization

In this study, n-type porous silicon (n-PS) films with high-aspect-ratio Si-tips are formed with the assistance of Hall-effect during the electrochemical anodization. Lorentz force sweeps down the majority carriers (electrons) in n-type Si to enhance the anodization etching. Surface layers are inverted from n-type to p-type, so sufficient holes can continuously appear on the surface to participate in chemical reaction during the etching process. Illumination is not necessary in this process, so the problem of illumination-depth limitation is solved. The etching current, morphology, and photoluminescence of the n-PS prepared in this way are investigated. Strong visible photoluminescence emissions at room temperature are demonstrated on n-PS.     

AFM investigation of silicon substrates for chemical vapour deposition of diamond films

AFM has been used to study surface modifications on silicon (100) substrates for CVD diamond deposition during bias pretreatment in a hot-filament reactor under various conditions. Both topographical images, force-distance measurements and chemical etching with HF have been implemented to obtain information on the processes involved. The results show, that the observed roughening, which strongly depends on the gas phase composition, is caused by chemical etching of the surface dominated by removal of elemental silicon via formation of silicon hydride.     

高多孔度多孔硅自支撑膜的制备与表征

发光多孔硅由于在光电子学方面的应用前景而引起人们极大的关注[1]．最近多孔硅发光二极管的研究方面取得了重大进展[2]。但是，有关多孔硅的发光机制仍然存在着争论[1，3，4]，利由于消除了单晶硅衬底的影响，对脱离了硅衬底的多孔硅自支撑膜能够进行普通多孔硅所不能进行的一     

微米级SiO合成多孔氧化硅/硅/碳储锂复合材料

以微米级SiO为原料,通过简单的高温煅烧、碳包覆和酸刻蚀制备多孔氧化硅/硅/碳复合材料,复合材料比表面积和平均孔径分别为32.9 m~2/g和3 nm。纳米硅分散在缓冲介质氧化硅多孔体系中,表面包覆一层薄而均匀的碳层。所得的复合材料具有较好的循环稳定性,在0.3 m A/g下,50次循环后可逆容量保持在645.1 m A·h/g。多孔结构、氧化硅缓解了硅在脱嵌锂过程的体积膨胀,碳层提高了复合材料的导电性和结构稳定性。     

发光多孔硅表面的STM研究

自从Canham首次报道了室温下多孔硅的光致发光现象以来^[1],多孔硅已成为半导体光电化学及材料领域内最为热门的研究课题^[2].