Study on 172‐nm vacuum ultraviolet light surface modifications of polydimethylsiloxane for micro/nanofluidic applications

In this study, we developed a technique for modifying the surface of the silicone elastomer Poly(dimethylsiloxane) (PDMS) by 172‐nm wavelength vacuum ultraviolet (VUV) light exposure. Such materials have high potential for application to micro/nanofluidic devices if their surface properties can be adequately controlled. The hydrophilicity, zeta potential and bonding strength of the VUV‐exposed surfaces were investigated and compared to surfaces exposed to conventional vacuum oxygen plasma. It was found that the proposed technique was effective at modifying the surface conditions from hydrophobic to hydrophilic, increasing the zeta potential, and allowing good bonding to glass. The time required to produce the maximum bonding strength was found to be similar to that for vacuum oxygen plasma exposure. However, since VUV exposure does not require the creation of a vacuum, it offers a faster turnaround, making it suitable for mass production. Copyright © 2010 John Wiley & Sons, Ltd.     

Use of ionic liquid aggregates of 1-hexadecyl-3-butyl imidazolium bromide in a focused-microwave assisted extraction method followed by high-performance liquid chromatography with ultraviolet and fluorescence detection to determine the 15+1 EU priority PAHs in toasted cereals ("gofios")

A focused-microwave assisted extraction method using aggregates of the ionic liquid (IL) 1-hexadecyl-3-butylimidazolium bromide (HDBIm-Br) followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection and single-channel fluorescence detection (FLD) has been developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in toasted cereals (“gofios”) of different nature (wheat, barley, rye, and maize corn) from the Canary Islands, Spain. The optimized HPLC-UV-vis/single-channel FLD method takes 40 min for the chromatographic run with limits of detection varying between 0.02 and 4.01 ng mL⁻¹ for the fluorescent PAHs from the European Union (EU) priority list in foods, and 20.5 ng mL⁻¹ for the non-fluorescent PAH cyclopenta[c,d]pyrene (CPP). The optimized microwave step presented extractions recoveries ranging from 70.1 to 109% and precision values lower than 12.6% (as relative standard deviation), using an extraction time of 14 min. The extraction method also utilizes low amounts of sample (0.1 g), and low amounts of IL (77 mg), avoiding completely the use of organic solvents.     

无定形TiO2可见光敏化降解染料污染物

采用一步水解法制备了无定形TiO2(Am-TiO2),并运用X射线衍射、X射线光电子能谱、N2吸附-脱附和紫外-可见漫反射光谱等手段对其进行了表征.结果表明,Am-TiO2具有大的比表面积(216m2/g)和丰富的表面羟基/化学吸附的水.与晶态TiO2相比,Am-TiO2的吸收带边明显蓝移(411nm→378nm),禁...     

Spontaneous transmission of chirality through multiple length scales

The hierarchical transfer of chirality in nature, from the nano‐, to meso‐, to macroscopic length scales, is very complex, and as of yet, not well understood. The advent of scanning probes has allowed chirality to be monitored at the single molecule or monolayer level and has opened up the possibility to track enantiospecific interactions and chiral self‐assembly with molecular‐scale detail. This paper describes the self‐assembly of a simple, model molecule (naphtho[2,3‐a]pyrene) that is achiral in the gas phase, but becomes chiral when adsorbed on a surface. This polyaromatic hydrocarbon forms a stable and reversibly ordered system on Cu(111) in which the transmission of chirality from single surface‐bound molecules to complex 2D chiral architectures can be monitored as a function of molecular packing density and surface temperature. In addition to the point chirality of the surface‐bound molecule, the unit cell of the molecular domains was also found to be chiral due to the incommensurate alignment of the molecular rows with respect to the underlying metal lattice. These molecular domains always aggregated in groups of three, all of the same chirality, but with different rotational orientations, forming homochiral “tri‐lobe” ensembles. At a larger length scale, these tri‐lobe ensembles associated with nearest‐neighbor tri‐lobe units of opposite chirality at lower packing densities before forming an extended array of homochiral tri‐lobe ensembles at higher converges. This system displayed chirality at a variety of size scales from the molecular (≈1 nm) and domain (≈5 nm) to the tri‐lobe ensemble (≈10 nm) and extended array (>25 nm) levels. The chirality of the tri‐lobe ensembles dictated how the overall surface packing occurred and both homo‐ and heterochiral arrays could be reproducibly and reversibly formed and interchanged as a function of surface coverage. Finally, these chirally templated surfaces displayed remarkable enantiospecificity for naphtho[2,3‐a]pyrene molecules adsorbed in the second layer. Given its simplicity, reversibility, and rich degree of order, this system represents an ideal test bed for the investigation of symmetry breaking and the hierarchical transmission of chirality through multiple length scales.     

CdS/石墨烯复合材料的制备及其可见光催化分解水产氢性能

以氧化石墨烯和CdS为原料, 在乙醇水溶液中采用CdS光催化还原法制备了CdS/石墨烯复合光催化材料, 并用透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)和瞬态光电流等技术对复合材料的结构和光电性能进行了表征. 可见光照射下(λ≥420 nm), 研究了该复合材料光催化分解水产氢的性能. 结果表明, 可见光照射下CdS的光生电子可有效地还原氧化石墨烯, 得到CdS与石墨烯之间具有强相互作用力的CdS/石墨烯复合材料. 与CdS相比, 复合材料中石墨烯作为良好的电子受体和传递介质, 可明显加快CdS光生电子的迁移速率, 提高光生载流子的分离效率, 从而增强复合材料的光电性能和光催化分解水产氢的活性.     

不同形态铈改性的TiO2纳米管阵列的制备及其可见光光电响应性质

采用电化学阴极还原和阳极氧化法,制备了还原态铈和氧化态铈改性的TiO2纳米管阵列,通过扫描电子显微镜(SEM)和X射线衍射(XRD)表征样品形貌和晶相,得出还原态铈以单质铈纳米纤维形式存在于TiO2纳米管内及表面,单质铈改性的TiO2纳米管经阳极氧化后,以CeO2和单质Ce形式共存.测定样品的光电流响应并计算样品的能带宽度.结果表明:单质铈改性的TiO2纳米管阵列在可见光区光电流响应较TiO2纳米管增强,单质铈添加存在最佳值,在10 mmol·L-1溶液中制备的单质铈改性的TiO2纳米管阵列光电流响应最强,能带宽度E9减少到2.88 eV,并且随着单质铈含量的增加,载流子浓度增大,且平带电位向负向移动.单质铈改性的样品经阳极氧化后,样品在紫外光区和可见光区光电流响应都增强,但其在可见光区的响应强度要小于单质铈改性的TiO2纳米管在可见光区的响应强度.     

气相色谱-质谱法测定热塑性弹性体中的多环芳烃

建立了一种简单、准确的测定热塑性弹性体中16种多环芳烃(PAHs)的气相色谱-质谱(GC-MS)方法。考察了样品制备、萃取溶剂、萃取方法、时间以及温度对厂家制备的阳性热塑性弹性体样品中PAHs提取效率的影响,确定了萃取条件和方法。样品经甲苯超声萃取、浓缩后用环己烷溶解、二甲亚砜液液萃取净化后采用GC-MS进行分析,内标法定量。通过对不同材质阳性热塑性弹性体样品的加标回收、精密度试验等对建立的方法进行评价,16种PAHs的平均回收率为70%～117%,精密度为0.2%～10.8%。该方法适合于热塑性弹性体中PAHs的测定。