Low‐Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow Spheres

This report presents a facile approach for the low‐temperature synthesis of crystalline inorganic‐oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic‐oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high‐κ‐gate dielectrics, and photocatalysis.     

热化学循环分解水制氢研究进展

热化学循环分解水制氢是利用核能或太阳能进行大规模、无污染制氢的有前景的方法 ,已经提出了多种流程.本文对热化学制氢流程及其评价标准进行了综述,重点介绍了碘硫循环、UT-3循环和Westinghouse循环等先进流程的研究进展.     

Sol–gel coating of poly(ethylene glycol)‐grafted multiwalled carbon nanotubes for stir bar sorptive extraction and its application to the analysis of polycyclic aromatic hydrocarbons in water

Poly(ethylene glycol) grafted onto carboxyl‐terminated multi‐walled carbon nanotubes were prepared by the sol–gel technique as a stationary phase for stir bars. The analytical methodology included stir bar sorptive extraction with micellar desorption followed by liquid chromatography. Polycyclic aromatic hydrocarbons were used as the model compounds to evaluate the extraction performance. The extraction efficiency, for the determination of polycyclic aromatic hydrocarbons from water samples, was optimized based on a chemometrics approach. The effect of the experimental parameters on the extraction response was investigated and the optimum extraction conditions were selected. Under the optimum conditions, the proposed method showed a good linearity within the different ranges for different analytes (e.g. 0.05–500 ng/mL for phenanthrene), a square of the correlation coefficient was higher than 0.999, and an appropriate limit of detection in the range of 0.013–0.072 ng/mL. The recoveries in all cases were above 94%, with relative standard deviations below 2.4%.     

Studies of the facetting of the polished (100) face of CaF2

The present paper deals with studies of the facetting of the polished (1 0 0) surface of CaF₂ during annealing and growth in UHV using low energy electron diffraction (LEED), atomic force microscopy (AFM), and transmission electron microscopy (TEM). First morphological modifications of the polished surfaces become visible at temperatures of T=874 K. Surfaces annealed at T=974 K exhibit a micro-roughening with pyramidal protrusions and corresponding depressions. LEED studies indicate the evolution of {1 1 1} facets. Reflexes from the (1 0 0) surface are not seen. After growth of about 660 monolayers of CaF₂ at T=1093 K and a saturation ratio S=33 from the vapor phase, larger pyramid-like or hip roof-like crystallites are developed. The results of AFM height profiles as well as of the LEED investigations indicate again the formation of {1 1 1} facets as proved by their angles of 54.7 ^o with the base (1 0 0) surface. This shows that the crystallites are homoepitaxially grown on the underlying CaF₂ substrate.     

红外飞秒激光诱导Ce3+掺杂闪烁晶体的上转换发光研究

本文研究了红外飞秒激光照射下Ce3+ 掺杂的YAP和LSO两种闪烁晶体的上转换发光现象.实验发现在飞秒激光泵浦下,这两种晶体的荧光均来自于Ce3+离子的5d-4f跃迁.荧光强度与泵浦光功率之间的依赖关系揭示了Ce3+:YAP和Ce3+:LSO晶体的上转换过程皆由三光子吸收过程所主导.分析表明,Ce3+:YAP和Ce3+:LSO晶体中的三光子吸收是三光子同时吸收.     

In Situ Electrodeposition of an Asymmetric Sol–Gel Membrane Based on an Octadecyltrimethoxysilane Langmuir Film

The unique properties of Langmuir film formation were utilized in assembling a thin skin of an asymmetric membrane. An octadecyltrimethoxysilane (ODTMS) Langmuir monolayer was formed at the air–water interface and served as the substrate for growing a bulky sol–gel polymer in situ. The latter was based on the electrochemical deposition of tetramethoxysilane dissolved in the water subphase by means of horizontal touch electrochemistry. The resultant asymmetric layer that consisted of a thin hydrophobic ODTMS Langmuir film connected to a bulk hydrophilic sol–gel network was studied in situ and ex situ by using various techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, transmission electron microscopy (TEM), and goniometry. We found that a porous hydrophilic film grew on top of a hydrophobic layer as was evident from TEM, contact angle, and EIS analyses. The film thickness and film permeability could be controlled by changing the deposition conditions such as the potential window applied and its duration. Hence, this method offers an alternative approach for assembling asymmetric films for various applications     

Control of Chiral Nanostructures by Self‐Assembly of Designed Amphiphilic Peptides and Silica Biomineralization

Peptides, the fundamental building units of biological systems, are chiral in molecular scale as well as in spatial conformation. Shells are exquisite examples of well‐defined chiral structures produced by natural biomineralization. However, the fundamental mechanism of chirality expressed in biological organisms remains unclear. Here, we present a system that mimics natural biomineralization and produces enantiopure chiral inorganic materials with controllable helicity. By tuning the hydrophilicity of the amphiphilic peptides, the chiral morphologies and mesostructures can be changed. With decreasing hydrophilicity of the amphiphilic peptides, we observed that the nanostructures changed from twisted nanofibers with a hexagonal mesostructure to twisted nanoribbons with a lamellar mesostructure, and the extent of the helicity decreased. Defining the mechanism of chiral inorganic materials formed from peptides by noncovalent interactions can improve strategies toward the bottom‐up synthesis of nanomaterials as well as in the field of bioengineering.     

“CLASSIC NMR”: An In‐Situ NMR Strategy for Mapping the Time‐Evolution of Crystallization Processes by Combined Liquid‐State and Solid‐State Measurements

A new in‐situ NMR strategy (termed CLASSIC NMR) for mapping the evolution of crystallization processes is reported, involving simultaneous measurement of both liquid‐state and solid‐state NMR spectra as a function of time. This combined strategy allows complementary information to be obtained on the evolution of both the solid and liquid phases during the crystallization process. In particular, as crystallization proceeds (monitored by solid‐state NMR), the solution state becomes more dilute, leading to changes in solution‐state speciation and the modes of molecular aggregation in solution, which are monitored by liquid‐state NMR. The CLASSIC NMR experiment is applied here to yield new insights into the crystallization of m‐aminobenzoic acid.     

大气复合污染及灰霾形成中非均相化学过程的作用

城市和区域大气复合污染的特征为污染源排放的一次污染物通过大气中的化学反应生成高浓度的氧化剂(臭氧等)及细颗粒物等二次污染物,它们在静稳天气下积累,导致低能见度的灰霾现象并严重影响人体健康和气候.大气复合污染中同时存在高浓度的一次排放和二次转化的气态及颗粒污染物,这为细颗粒表面非均相反应提供了充足的反应物;而气态污染物在细颗粒表面的非均相反应可改变大气氧化性及颗粒物的化学组分、物化性质和光学性质,从而可能对大气复合污染和灰霾的形成起到促进的作用.利用漫反射红外傅里叶变换光谱和单颗粒显微拉曼原位在线技术,我们对大气气态污染物NO2、SO2、O3、甲醛在CaCO3、高岭石、蒙脱石、NaCl、海盐、Al2O3和TiO2等大气主要颗粒物表面的反应进行了系统的反应动力学和机制研究,我们发现反应主要产物为硫酸盐、硝酸盐或甲酸盐,它们可极大改变颗粒物吸湿性和消光性质.通过分析这些非均相反应的动力学过程,我们识别出NO2-颗粒物-H2O、SO2-颗粒物-O3、有机物/SO2-颗粒物-光照等三元反应体系的协同作用机制,这些协同机制对于阐明大气复合污染及灰霾形成的反馈机制和非线性过程提供了实验证据和理论依据.     

Vacuum-UV-photolysis of aqueous solutions of citric and gallic acids

The vacuum-UV- (VUV-) photolysis of water is one of the advanced oxidation processes (AOP) based on the production of hydroxyl radicals (HO) that can be applied to the degradation of organic pollutants in aqueous systems. The kinetics of the VUV-photolyses of aqueous solutions of citric acid (1) or gallic acid (2) were investigated in the presence or absence of dissolved molecular oxygen (O₂) and under different pH conditions. In the case of 1, the rate of consumption of the substrate was faster at pH 3.4 than in alkaline solution (pH 11), whereas, in the case of 2, the variation of pH (2.5–7.5) did not affect the course of the reaction. Unexpectedly, the rates of depletion of both 1 and 2 decreased in the absence of O₂, this effect being much more pronounced in the case of 2. In order to explain these results, possible reaction pathways for the degradation of 1 and 2 are proposed, and the roles of the oxidizing (HO) and reducing (H and e_aq⁻) species produced by the VUV-photolysis of water are discussed.