Direct observation of p,p′‐dimercaptoazobenzene produced from p‐aminothiophenol and p‐nitrothiophenol on Cu2O nanoparticles by surface‐enhanced Raman spectroscopy

Surface‐enhanced Raman scattering of p‐aminothiophenol and p‐nitrothiophenol were obtained on the surface of Cu₂O nanoparticles, showing novel spectral changes with morphology‐dependent and time‐dependent characteristics. The measured Raman signals were believed to partly originate from the newly produced surface species p,p′‐dimercaptoazobenzene. The nature of surface chemisorption status during Raman measurement was investigated experimentally and theoretically via combined surface‐enhanced Raman scattering and density functional theory study, indicating that surface catalytic reaction of p‐aminothiophenol and p‐nitrothiophenol could take place on the surface of oxide nanostructures as well as coinage metal material. Copyright © 2013 John Wiley & Sons, Ltd.     

ROMP based photoinitiator‐coinitiator systems with improved migration stability

Nowadays, migration stability is one of the key features for photoinitiators used in radiation curable formulations, especially when the material is in contact with food or the human body. Herein, the synthesis and characterization of statistical copolymers with covalently bound eosin and/or ethyl dimethylamino benzoate units by ring opening metathesis polymerization is presented. The prepared compounds were tested as macroinitiators for the photopolymerization of acrylates aiming at an initiator/coinitiator system which combines good polymerization activity with improved migration stability. An acrylate modified eosin derivative which is incorporated into the polymer network during the photopolymerization reaction and, therefore, less likely to leak from the polymer compound was used as reference. Photoinitiating activities of low and high molecular weight initiators and coinitiators were investigated by photo‐DSC. Moreover, leakage studies and viability tests with osteoblast‐like cells were performed to proof the suitability of this concept. The use of polymeric eosin in combination with a low molecular weight coinitiator was found to be a good compromise when aiming at a photoinitiating system with sound performance and improved migration stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3648–3661, 2008     

Microwave-Mediated Modification of Selected Limonoids with DMAB Reagent and Antibacterial Studies

N,N-Dimethylaniline.borane (DMAB) is a stable, multifaceted electrophilic boron agent that displays hydroboration of C = C as well as selective reduction of functional groups under reflux, microwave, and ultrasound conditions. Natural products contain a plethora of functional groups that govern the specific bioactivity. It will be interesting to correlate the change in a functional group with the concern for change in bioactivity. Current research emphasizes the influence of microwave irradiation on moderately reactive DMAB reagent towards the functional group modification of selected limonoid-phytochemicals of Meliaceae family viz. cedrelone, azadirone, nimbin, and azadiradione. DMAB conveniently reduces the ketone, epoxide group into alcohol, and does a hydroboration reaction on the C = C bond. It does not show interest to reduce the ester group irrespective of 30 min of MW irradiation. Except for these reducing properties, the reagent DMAB unveils chemo-selective nature in respect of different functional groups and utilizes in an asymmetric synthesis. The coalescence of amine.borane with microwave irradiation brings forth a commodious and prompt method for the selective reduction of functional groups. The bioactive efficacy of modified phytochemicals is further taken for the antimicrobial studies.     

Liquid chromatography coupled to on-line post column derivatization for the determination of organic compounds: A review on instrumentation and chemistries

Analytical derivatization either in pre or post column modes is one of the most widely used sample pretreatment techniques coupled to liquid chromatography. In the present review article we selected to discuss the post column derivatization mode for the analysis of organic compounds. The first part of the review focuses to the instrumentation of post-column setups including not only fundamental components such as pumps and reactors but also less common parts such as static mixers and back-pressure regulators; the second part of the article discusses the most popular “chemistries” that are involved in post column applications, including reagent-less approaches and new sensing platforms such as the popular gold nanoparticles. Some representative recent applications are also presented as tables.     

基于石墨烯基底的光催化特性

金属纳米结构中传导电子的集体振荡所产生的表面等离子体不仅可以使电磁场在时间和空间上重新分布,还可以使被激发的载流子重新分布.采用机械剥离法制备了石墨烯材料,借助拉曼光谱扫描技术(M apping)研究了石墨的层数在二维区域内的分布情况.研究了2-萘硫醇(2-N T)作为探针分子在石墨烯衬底上的SERS增强特性.结果表明...