The electro-structural behaviour of yarn-like carbon nanotube fibres immersed in organic liquids

Yarn-like carbon nanotube (CNT) fibres are a hierarchically-structured material with a variety of promising applications such as high performance composites, sensors and actuators, smart textiles, and energy storage and transmission. However, in order to fully realize these possibilities, a more detailed understanding of their interactions with the environment is required. In this work, we describe a simplified representation of the hierarchical structure of the fibres from which several mathematical models are constructed to explain electro-structural interactions of fibres with organic liquids. A balance between the elastic and surface energies of the CNT bundle network in different media allows the determination of the maximum lengths that open junctions can sustain before collapsing to minimize the surface energy. This characteristic length correlates well with the increase of fibre resistance upon immersion in organic liquids. We also study the effect of charge accumulation in open interbundle junctions and derive expressions to describe experimental data on the non-ohmic electrical behaviour of fibres immersed in polar liquids. Our analyses suggest that the non-ohmic behaviour is caused by progressively shorter junctions collapsing as the voltage is increased. Since our models are not based on any property unique to carbon nanotubes, they should also be useful to describe other hierarchical structures.     

Degradation kinetics of total phenolic compounds,capsaicinoids and antioxidant activity in red pepper during hot air and infrared drying process

Degradation kinetics of total phenolic compounds, capsaicinoids and antioxidant activity in red pepper during both hot air drying and infrared drying were investigated, as well as the correlation between antioxidant compounds and antioxidant capacity was discussed in current study. The fractional conversion kinetic and first order kinetic models were proved to describe the changes of total phenolic compounds vs. drying time and moisture content, respectively. Degradation of capsaicinoids and antioxidant capacity vs. drying time and moisture content both followed fractional conversion kinetic model. Infrared drying accelerated the degradation rate of total phenolic compounds and capsaicinoids vs. drying time as compared with hot air drying at the same temperature; however, a contrary result was found that infrared drying decreased the degradation rate of both total phenolic compounds and capsaicinoids vs. moisture content. Total phenolic compounds exhibited a stronger relationship with antioxidant capacity of red pepper analysed by multiple linear regression analysis.     

Partitioning of PCBs from air to clothing materials in a Danish apartment

Polychlorinated biphenyl (PCB) contamination of buildings continues to pose an exposure threat, even decades after their application in the form of calks and other building materials. In this research, we investigate the ability of clothing to sorb PCBs from contaminated air and thereby influence exposure. The equilibrium concentration of PCB‐28 and PCB‐52 was quantified for nine used clothing fabrics exposed for 56 days to air in a Danish apartment contaminated with PCBs. Fabric materials included pure materials such as cotton and polyester, or blends of polyester, cotton, viscose/rayon, and/or elastane. Air concentrations were fairly stable over the experimental period, with PCB‐28 ranging from 350 to 430 ng/m³ and PCB‐52 ranging from 460 to 550 ng/m³. Mass accumulated in fabric ranged from below detection limits to 4.5 mg/g of fabric. Cotton or materials containing elastane sorbed more than polyester materials on a mass basis. Mass‐normalized partition coefficients above detection limits ranged from 10^5.7 to 10^7.0 L/kg. Clothing acts as a reservoir for PCBs that extends dermal exposure, even when outside or in uncontaminated buildings.     

Characterization of EfOM Fraction Responsible for Short-Term Fouling in Ultrafiltration

Based on our earlier diagnosis that hydrophobic and hydrophilic (HPO/HPI) acids are the primary cause of short-term fouling in the ultrafiltration of secondary effluent, the HPO/HPI acids were extracted and subsequently characterized in comparison with commercial organic materials. HPO/HPI acids isolated from secondary effluent contained significantly fewer complex mixtures than humic substances that have been implicated as the dominant foulants in the filtration of surface water using porous membranes. The physicochemical and spectroscopic characterization demonstrated that the aromaticity and apparent molecular weight of HPO/HPI acids were lower than that observed for other humic materials, while the oxygenated functional groups were relatively higher.     

Inhalation risk of indoor aerosol spray products commercially available in Bangladesh

Today, urbanised people spend most of their time in indoor environments, and the risk of exposure to toxic materials in an indoor environment is of great concern. This paper considers sources for the inhalation risk of aerosol sprays by measuring the particle size distributions of some of the most popular products that are commercially available in Bangladesh, and examines the degree of toxicity and the health risk via the respirability of the products. Results show that thoracic and respirable fractions of the suspended particulate matter are present in the tested samples and hence the spray products may pose a significant health risk.     

Realizing improved performance of down-conversion white organic light-emitting diodes by localized surface plasmon resonance effect of Ag nanoparticles

Down-conversion structure white organic light-emitting diodes (WOLEDs), in which white light is generated by a blue emission organic light-emitting diodes (OLEDs) in combination with a color conversion layer (CCL) outside the substrate, has attracted extensive interest due to its significant advantages in low cost and stabilized white-light emissions. However, low color-conversion efficiency of CCL is still a bottleneck for the performance improvement of down-conversion WOLEDs. Here, we demonstrate an approach to enhance the color-conversion efficiency of CCL-WOLEDs by localized surface plasmon resonance (LSPR) effect. In this approach, a blend of Ag nanoparticles and polyvinyl alcohol (PVA) is solution-deposited between the blue organic light emitting diodes and color-conversion layer. Based on the LSPR effect of this modified structure, the color conversion efficiency has improved 32%, from 45.4% to 60%, resulting a 14.4% enhancement of the current efficiency, from 9.73 cd/A to 11.14 cd/A. Our work provides a simple and low-cost way to enhance the performance of down-conversion WOLEDs, which highlights its potential in illumination applications.     

Two different donor subunits substituted unsymmetrical squaraines for solution-processed small molecule organic solar cells

Two unsymmetrical squaraines (USQs) with different donor (D) subunits as photovoltaic materials, namely USQ-11 and USQ-12, were designed and synthesized to investigate the effect of different D subunits on the optoelectronic properties of USQs for the first time. The two USQs compounds were characterized for optical, electrochemical, quantum chemical and optoelectronic properties. By changing the two different D subunits attached to the squaric acid core from 2,3,3-trimethylindolenine to 2-methylbenzothiazole, the HOMO energy levels could be tuned with a stepping of 0.07 eV, and quite different solid state aggregations (H- or J-aggregation) were observed in the thin film by UV-Vis absorption spectra, which were attributed to their distinct steric effects and dipole moments. Solution-processed bulk-heterojunction small molecule organic solar cells fabricated with the USQ-11/PC₇₁BM (1:5, wt%) exhibited extremely higher PCE (4.27%) than that of the USQ-12/PC₇₁BM (2.78%). The much enhanced PCE should be attributed to the simultaneously improved V_oc, J_sc and FF.     

综述与展望 丙烷直接氨氧化制丙烯腈生产工艺及催化剂研究进展

概述丙烯腈的生产方法及特点,分析丙烷直接氨氧化生产丙烯腈的工艺特点和优势,对丙烷直接制备丙烯腈的催化剂体系Sb-V-O催化剂、Mo-V-Te-Nb-O催化剂、钒-铝氮氧化物及分子筛类催化剂等进行介绍,并建议我国尽快实现以丙烷为原料生产丙烯腈。