Electron Microscopy Characterization of Silicon Dioxide Nanotubes

Well‐developed crystals of [Pt(NH₃)₄](HCO₃)₂ are employed as template for the synthesis of silicon dioxide nanotubes (SiO₂‐NTs). Silicon dioxide, which is produced by a sol‐gel reaction, coats the surface of these crystals and builds up the nanotube walls. In the final step, the Pt‐salt fibers are thermally decomposed and auto‐reduced to metallic Pt nanoparticles. Scanning and transmission electron microscopy (SEM and TEM) investigations of the product confirm the formation of silicon dioxide nanotubes in high yield. The tube walls consist of amorphous silicon dioxide. The tube length generally is 0.5 — 3 μm, while the thickness varies in two distinct ranges: thick tubes have a diameter of 100 — 500 nm and thin ones of approximately 50 nm. Most of the NTs are filled with Pt particles, but others, typically the larger ones with open tube ends, obviously are empty. Presumably, open ends cause the observed Pt loss. In closed SiO₂‐NTs, Pt forms as ca. 10 nm large particles in the tube core and as 1 — 2 nm large particles inside the tube walls.     

Preparation of Manganese Oxide Hollow Spheres Using pH-responsive Microgels as Templates

以pH响应型微凝胶为模板制备出了二氧化锰空心球材料,并利用XRD、TGA、SEM、FT-IR和TEM等手段对其进行了表征. 结果表明,通过调节KMnO₄的用量可以有效控制二氧化锰空心球的球壳厚度. 对洗脱后上层清夜中的pH响应型微凝胶进一步研究发现,部分微凝胶呈现出非可逆的膨胀-收缩转变,这一现象主要是由于其内部的交联程度不高造成的. 在对表征结果进行分析后提出了空心球结构的形成机理.     

Nanometer‐Sized Copper Sulfide Hollow Spheres with Strong Optical‐Limiting Properties

CuS semiconductor nanometer‐sized hollow spheres are successfully synthesized by using a soft‐template method. A possible growth mechanism is proposed. The linear optical property of the CuS hollow spheres is examined by means of photoluminescence spectroscopy at room temperature. The optical‐limiting (OL) property of these nanostructures is characterized by using a nanosecond Q‐switched YAG laser and an optical parametric oscillator pumped with Surelite‐III. A strong OL response is detected for the CuS hollow spheres in both visible and near infrared (NIR) spectral ranges, which makes these promising materials for applications such as the protection of human eyes or as optical sensors for high‐power laser irradiation. The OL mechanism of the CuS hollow‐sphere nanostructure may be the combination of free‐carrier absorption (FCA) and nonlinear scattering.     

A Novel Mesoporous CaO‐Loaded In2O3 Material for CO2 Sensing

A mesoporous CaO‐loaded In₂O₃ material (with Ca/In₂O₃ ratios ranging from 2.5 to 8.5 at %) has been synthesized and used as resistive gas sensor for the detection of CO₂. A nanostructured In₂O₃ matrix has been obtained by hard template route from the SBA‐15 silica template. Additive presence does not distort the lattice of In₂O₃, which crystallizes in the Ia3 cubic space group. It has been proved by XRD, HRTEM, Raman and XPS measurements that samples contain not only CaO but also CaCO₃ in calcite phase as a consequence of CaO carbonation. Pure In₂O₃ based sensors are low sensitive to CO₂, whereas those containing the additive show an important response in the 300–5000 ppm range of gas concentrations. As seen by DRIFTS, the electrical response arises from the interaction between CO₃^2– and CO₂, yielding bicarbonates products. The reaction is water‐assisted, so that hydration of the sensing material ensures sensor reliability whilst its dehydration would inhibit sensor response. The use of CaCO₃ instead of CaO does not cause significant differences in electrical and DRIFTS data, which corroborates the important role played by carbonate species in the sensing mechanism.     

热处理温度对蛋白石晶体的影响

 采用等体积快速混合法制备了不同粒径的单分散SiO₂微球,通过重力垂直沉降自组装形成了蛋白石模板,研究了热处理温度对蛋白石晶体模板形貌、结构与光学性能的影响。SEM,TG-DSC,UV-Vis等分析表明：热处理可提高组装微球的粘合性与模板的机械强度;SiO₂胶体模板煅烧温度在700～800 ℃较为合适;热处理能够改变蛋白石晶体光子带隙的位置,随着煅烧温度的升高,带隙发生蓝移并且带隙逐渐变窄。