Photoelectrochemical properties of sol–gel synthesized titanium dioxide nano-particles using different acids: X-ray photoelectron spectroscopy reveals the induced effect of hydrolysis precursor

Properties such as crystalline structure (X-ray diffraction – XRD), surface chemistry–electronic states (X-ray photoelectron spectroscopy – XPS), morphology and particle size-distribution (Transmission Electron Microscopy – TEM), electronic structure-band-gap (UV–vis spectroscopy) and surface area (BET-nitrogen physisorption) were analyzed for titanium dioxide (TiO₂)-semiconductor-surfaces synthesized by sol–gel route using nitric, acetic and phosphoric acids as hydrolysis precursors. According to XRD analysis, it was established that anatase phase has been obtained with a particle size linked to the acid of hydrolysis employed (i.e. dissociation constant), as also demonstrated by TEM and area BET. On the other hand, using XPS, a shift toward lower binding energies was observed from TiO₂ obtained using HNO₃ promoting some structural modification and the reduction in the band-gap, inducing a better faradic current-performance by decreasing charge-transfer resistance during polarization and at induced-generated photocurrent using UV-light.     

Studies on the physicochemical characteristics of volatile oil from pepper (Piper nigrum) extracted by supercritical carbon dioxide

Pepper (Piper nigrum L) volatile oil was extracted with supercritical fluid carbon dioxide at pressures of 8 and 10 MPa and at two different temperatures, 40°C and 60°C. The mass transfer rates are presented at different supercritical conditions of extraction, together with the fractionation effect that was observed. The volatile oil obtained was analysed for its physical constants: specific gravity, refractive index and optical rotation. The samples were fractionated by column chromatography, and both the samples and fractions were subjected to TLC, gas chromatography and sensory analysis. It was observed that pepper oil obtained with supercritical fluid carbon dioxide at 10 MPa and 60°C was superior to steam-distilled oil.     

高温热氧化中SiO2层厚度的控制研究

本文介绍了Si热氧化的工艺过程和温度曲线,对热氧化生成的SiO2层厚度进行了理论计算和实际测定;并列出了７个ＳiO2样品的干,湿氧时间,理论计算值,实测值及产生的误差值,多数样件可控制在１５％左右（最优达７０％）;介绍了控制干,湿氧不相互干扰的管路系统,稳定水浴湿度９５℃的方法,分析了影响ＳiO2层厚度的石英管口径及氧气流量等因素。     

Molybdenum Dioxide Nanoparticles Anchored on Nitrogen-Doped Carbon Nanotubes as Oxidative Desulfurization Catalysts: Role of Electron Transfer in Activity and Reusability

Electron transfer between metal-oxides and supports considerably affects the oxidative desulfurization (ODS) performance of catalysts, while this is far from being well understood. Herein, molybdenum dioxide with oxygen vacancies (V_O-MoO₂) catalysts derived from Mo-based metal-organic frameworks are anchored on electron-rich nitrogen-doped carbon nanotubes (NC) to obtain excellent ODS activity and reusability. Results show that either dibenzothiophene (DBT) or 4,6-dimethyldibenzothiophene (4,6-DMDBT) is removed 100% on the composite catalyst (V_O-MoO₂@NC) within 40 min of reaction when cumene hydroperoxide is chosen as an oxidant. After five cycles of reaction, DBT and 4,6-DMDBT removal still exceeded 99.5 and 95.0%, respectively. Results from density functional theory calculations and characterizations confirm that the strong electron-donating effect of NC on V_O-MoO₂ can promote the dispersion of V_O-MoO₂ and reduce the bond energy of the Mo O bond, leading to exposure of active sites and enrichment of oxygen vacancies (V_O). Furthermore, the strong interfacial electrostatic interaction caused by the electron transfer from NC to V_O-MoO₂ can reduce the leaching of active sites of the catalyst. This study provides a versatile strategy of constructing strong electronic interaction between metal-oxide and support via anchoring on NC for the design of high-performance ODS catalysts.     

Caffeine in Coffee: Its Removal. Why and How?

The popularity of coffee as a beverage is ever increasing despite the fact that there are reports antagonized to its consumption. Of the several factors cited, the alkaloid caffeine present in coffee can cause addiction and stimulate the central nervous system. It has an effect on the cardiovascular system with a slight increase in blood pressure and heart output. It undergoes biotransformation in the human body to form methylated derivatives of uric acid. In recent times, much effort has gone into the research on the removal of caffeine in coffee, resulting in a specialty product called decaffeinated coffee. Decaffeination methods mainly employ organic solvents or water or supercritical carbon dioxide. These methods with their attendant advantages and disadvantages are reviewed in this article.     

The measurement of carbon dioxide transmission of edible films by a static method

A static method is proposed for the measurement of CO₂ transmission of edible films. It is based on the absorption of CO₂ transmitted through the film on an absorbent ascarite II. Water is evolved during absorption of CO₂ by ascarite II and that is absorbed by a desiccant, anhydrous CaCl₂. Total CO₂ transmission is determined from the increase in weight of the absorbents. The transmission parameters, CO₂ transmission rate (CO₂TR), CO₂ permeance and CO₂ permeability (CO₂P), are also calculated. The edible film used was composed of methyl cellulose and polyethylene glycol. An attempt was made to determine the optimum amounts of ascarite II and CaCl₂ to be used. Finally, the effect of CO₂ pressure on the transmission parameters was also examined. CO₂TR was found to increase with increasing pressure while CO₂ permeance and CO₂P values were found to decrease with increasing pressure. © 1999 Society of Chemical Industry     

一种新型红外影像假目标的可行性分析

探讨一种利用CO2激光器生成新型红外影像假目标的方法,阐述了新型红外影像假目标的组成和基本工作原理,分析了利用CO2激光器生成新型红外影像假目标的可行性,为研制对抗红外成像侦察和制导的假目标提供了一种新的技术途径.     

Composite Nanostructures of TiO2 and ZnO for Water Splitting Application: Atomic Layer Deposition Growth and Density Functional Theory Investigation

The commercialization of solar fuel devices requires the development of novel engineered photoelectrodes for water splitting applications which are based on redundant, cheap, and environmentally friendly materials. In the current study, a combination of titanium dioxide (TiO₂) and zinc oxide (ZnO) onto nanotextured silicon is utilized for a composite electrode with the aim to overcome the individual shortcomings of the respective materials. The properties of conformal coverage of TiO₂ and ZnO layers are designed on the atomic scale by the atomic layer deposition technique. The resulting photoanode shows not only promising stability but also nine times higher photocurrents than an equivalent photoanode with a pure TiO₂ encapsulation onto the nanostructured silicon. Density functional theory calculations indicate that segregation of TiO₂ at the ZnO surfaces is favorable and leads to the stabilization of the ZnO layers in water environments. In conclusion, the novel designed composite material constitutes a promising base for a stable and effective photoanode for the water oxidation reaction.     

Molybdenum Dioxide in Carbon Nanoreactors as a Catalytic Nanosponge for the Efficient Desulfurization of Liquid Fuels

The principle of a “catalytic nanosponge” that combines the catalysis of organosulfur oxidation and sequestration of the products from reaction mixtures is demonstrated. Group VI metal oxide nanoparticles (CrO_x, MoO_x, WO_x) are embedded within hollow graphitized carbon nanofibers (GNFs), which act as nanoscale reaction vessels for oxidation reactions used in the decontamination of fuel. When immersed in a model liquid alkane fuel contaminated with organosulfur compounds (benzothiophene, dibenzothiophene, dimethyldibenzothiophene), it is found that MoO₂@GNF nanoreactors, comprising 30 nm molybdenum dioxide nanoparticles grown within the channel of GNFs, show superior abilities toward oxidative desulfurization (ODS), affording over 98% sulfur removal at only 5.9 mol% catalyst loading. The role of the carbon nanoreactor in MoO₂@GNF is to enhance the activity and stability of catalytic centers over at least 5 cycles. Surprisingly, the nanotube cavity can selectively absorb and remove the ODS products (sulfoxides and sulfones) from several model fuel systems. This effect is related to an adsorptive desulfurization (ADS) mechanism, which in combination with ODS within the same material, yields a “catalytic nanosponge” MoO₂@GNF. This innovative ODS and ADS synergistic functionality negates the need for a solvent extraction step in fuel desulfurization and produces ultralow sulfur fuel.     

TiO2纳米粉体的烧结行为及其性能的研究

分别采用Ti(SO4)2、TiOCl2沸腾回流直接水解制得了纯锐钛矿型和混晶的纳米TiO2。用XRD、SEM对不同煅烧温度下的纳米TiO2粉末结构、粒径大小进行了表征。结果表明:混晶中的锐钛矿相转变温度(500℃)明显低于纯锐钛矿相的(600℃以上)。纳米TiO2粉末的光催化活性与煅烧温度密切相关,500℃煅烧的混晶结构的纳米TiO2粉体表现出较高的光催化活性,20 min催化氧化降解率达到92.3%。