The effect of cationic disorder on the optical and electrochemical behavior of nanocrystalline ZnO preparedfrom peroxide precursors

The relation between particle size and the optical and electrochemical behavior of nanocrystalline ZnO was studied on materials prepared by the thermal decomposition of zinc peroxide. The formation of zinc oxide starts at 180°C and yields particles of characteristic size bigger than 10 nm. Smaller particles (r∼2–5 nm) may be prepared at reduced pressure and at a temperature of 150°C. The particle radius of synthesized nanocrystals increases proportionally to synthesis temperature. Regardless of actual particle size, synthesized ZnO samples show cationic disorder, with Zn distributed between 2b and 2a sites. The fraction of “octahedrally” coordinated Zn in 2a position decreases with increasing synthesis temperature. Zn disorder causes a narrowing of band gap, which results in the “red shift” of the absorption edge in the UV–Vis spectra of prepared samples with respect to bulk ZnO. The effect of the disorder on the band gap width is partially compensated by quantum size effects when the characteristic particle size drops below 5 nm. A decrease in particle size results in an asymmetric shift of valence and conduction band edges, which can be assigned to uneven effective masses of electrons and holes in nanocrystalline ZnO. Prepared nanocrystalline samples were (photo)electrochemically active; their activity, however, decreases with particle size.

Photo‐polymerized lauryl methacrylate monolithic columns for CEC using lauroyl peroxide as initiator

Lauryl methacrylate (LMA)‐ester based monolithic columns photo‐polymerized using lauroyl peroxide (LPO) as initiator were prepared, and their morphological and CEC properties were studied. The composition of the polymerization mixture (i.e. ratios of monomers/porogenic solvents, 1,4‐butanediol/1‐propanol and LMA/crosslinker) was optimized. The morphological and chromatographic properties of LMA columns were evaluated by means of SEM pictures and van Deemter plots of PAHs, respectively. The polymerization mixture selected as optimal provided a fast separation of a mixture of PAHs with excellent efficiencies (minimum plate heights of 8.9–11.1 μm). Satisfactory column‐to‐column (RSD<4.5%) and batch‐to‐batch reproducibilities (RSD<6.3%) were achieved. The LMA columns photo‐polymerized with LPO were compared with those prepared with AIBN. Using PAHs, alkylbenzenes and basic compounds for testing, the columns obtained with LPO gave the best compromise between efficiency, resolution and analysis time.     

降解水中有机毒物的新型反应体系研究

利用空气中的氧电化学合成H₂O₂,制备具有较高电流效率的空气电极.将空气电极用于构成降解有机毒物的新型反应体系电化学氧化体系、光激发氧化剂氧化体系和光电-Fenton氧化体系.实验测量了H₂O₂在不同体系不同条件下的分解速率,并与相应的传统式体系作了比较.实验测量了苯胺在新型体系中的矿化反应速率,发现H₂O₂的分解速率与苯胺的矿化速率有良好的平行关系,其中H₂O₂分解速率最快的光电-Fenton体系是氧化降解有机分子的最佳体系.通过光电-Fenton体系和光-Fenton体系的比较,揭示了空气电极/溶液界面在光电-Fenton体系中所起的重要作用.初步讨论了苯胺分子在光电-Fenton体系中矿化反应的机制.     

Preparation and Evaluation of Melamine Molecularly Imprinted Polymers by Thermal‐ and Photo‐initiation Methods

Melamine imprinted polymers (MIPs) have been prepared using identical polymer formulation by both thermal‐ and photo‐initiation method, respectively. Physical characterization of the polymers revealed that the different polymerization methods led to the slight differences in both polymer structures and performance by scanning electron microscope (SEM), infrared absorption (IR), and mercury analyzer (MA). Both MIPs were used as selective sorbents for the solid phase extraction (SPE) of melamine in milk powders, followed by the determination coupled to HPLC. The recoveries of melamine in spiked milk powders were obtained in the range of 92.4‐97.7% and 94.6‐99.7%, for both MIP_thermal and MIP_photo, respectively.     

Direct syntheses,characterization and optical analysis of PbX2 (X = I,Br and Cl) nanoparticles without any additives

Lead iodide, bromide and chloride nanoparticles (NP-PbX₂, X = I, Br and Cl) with various morphologies were successfully prepared through a simple hydrothermal method without any additives or stabilizers. By treating the PbX₂ in EtOH/CH₂Cl₂ solution at 170 °C for 12 h, the corresponding PbX₂ nanoparticles were synthesized. The average sizes of PbX₂ nanoparticles were between 30 and 80 nm. The structure, morphology, surface and size of PbX₂ nanoparticles were determined by X-ray diffraction powder, Scanning Electron Microscopy, solid state Photo Luminescent, BET surface area and solid state UV.     

气相硝酸及过氧亚硝酸的结构和光电子能谱

采用了B3LYP方法和6-311G(d) 基组，并辅以MP2方法详细地计算了硝酸(HONO2)和过氧亚硝酸(HOONO)及相应正离子的各种可能构象、能量、振动频率等，分析了它们的相对稳定性、电离势、光电子能谱，探讨了用光电子能谱去探测HOONO的可能性.结构优化结果表明， HOONO和HOONO＋均有三种稳定的构象， HOONO有三个一阶鞍点的结构.作出了HOONO和HOONO＋的能量随O－O键旋转的变化曲线图，定性地讨论了可能存在的物种以及各构象之间几何结构的变化.     

Photoredox mediated CN cross coupling of sulfoximines with aryl iodides

A new photoredox-catalyzed CN coupling reaction of sulfoximines with aryl halides has been developed for a general N-arylation of sulfoximines. The reactions proceed in the presence of visible light with high levels of chemoselectivity and a wide range of functionality is tolerated. There is a rapidly increasing interest in sulfoximines as pharmacophores in drug discovery and this new method offers potential in terms of high functional group tolerance and late-stage functionalization of compounds.     

Photo cross-linked biodegradable hydrogels for enhanced vancomycin loading and sustained release

A series of biodegradable hydrogels based on dextran and poly（L-glutamic acid） were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly（L-glutamic acid）-g-hydroxyethyl methacrylate （PGH） in the presence of photoinitiator 12959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly（L-glutamic acid） content in the hydrogels. The higher content of poly（L-glutamic acid） in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin （VCM） loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus （MRSA） inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering.     

Automation of the Photodegradation Spectrophotometric Method for the Determination of Diethylstilbestrol by Flow Injection

ABSTRACT

An spectrophotometric determination of diethylstilbestrol is proposed on the basis of on-line photo-degradation and measurement at 330 nm. The procedure is accomplished by means of flow-injection assembly including a photo-reactor formed by a PTFE 168 cm long coil around a low-pressure mercury lamp 6 w; this photo-reactor was nested between the injection valve and the spectrophotometric flow-cell. The sample solution was injected into a carrier stream of aqueous di-potassium hydrogen ortophosphate flowing at 5.0 ml min^?1. Influence of the physic-chemical and hydrodynamic parameters was studied and optimised. The calibration graph was linear up to 65 mg l^?1, and the procedure presented a reproducibility (rsd of the calibration slope) 1.4%, and a sample throughput of 52 h^?1. The influence of foreign compounds was tested.     

新型水溶性荧光标示剂吲哚方酸菁染料的合成及光谱性能

用方酸与不同的N烷基取代吲哚啉季铵盐缩合制备了一系列对称的水溶性方酸菁染料. 通过核磁共振氢谱和质谱对合成的染料结构进行了表征, 研究了它们在不同溶剂中的吸收和发射光谱. 结果表明, 随着溶剂极性的增大, 染料的吸收光谱发生蓝移, 表现为负向溶剂化效应, 在极性溶剂中的荧光量子产率比在水中的大. 考察了N位取代基对染料水溶液光稳定性的影响, 结果表明在吲哚环N原子上引入较大的苄基有助于提高光稳定性, 且随着苄基上取代基吸电子能力的增强, 染料的光稳定性增强.