Two-photon absorption and laser photolysis of trans-stilbene substitutes

The measured the two-photon absorption (TPA) cross sections of ethanol solution of trans-stilbene and its two substitutes excited by nanosecond radiation of the 2nd harmonic of a Nd:YAG laser (532 nm) are presented. To determine the TPA cross section, a method based on measurements of photochemical decomposition of molecules of the examined compounds having low photostability is suggested. The measured value of the TPA cross section of trans-stilbene in ethanol is found to be 25 GM, and the TPA cross sections of the trans-stilbene substitutes are found to be 60 and 70 GM. The TPA cross section of trans-stilbene substitutes obtained in the present paper is compared with the experimental and theoretical data obtained by other authors. The results of investigations demonstrate that the photochemical decomposition method can be successfully used to determine experimentally the two-photon absorption cross section of the compounds unstable under photoexcitation, including photochromatic molecules, biological objects, and radical photoinitiators.     

光化学反应在流动注射分析中的应用研究 Ⅲ.甲基橙光化学反应体系测定亚硝酸根、硝酸根和铁(Ⅲ)

基于NO_2~-、NO_3~-和Fe(Ⅲ)对甲基橙光化学褪色反应的催化作用,利用自制流通式光化学反应器,建立了流动注射光化学反应同时测定NO_2~-和NO_3~-以及测定Fe(Ⅲ)的新方法。测定NO_2~-和NO_3~-的线性范围都是0.1～3.2mg/L,每小时可测30～40个样品,测定Fe(Ⅲ)的线性范围为0.06～1.2mg/L,进样频率为60～80次/h。应用于蔬菜中NO_2~-、NO_3~-的测定和茶叶中铁的测定,结果满意。     

α,ω-二碘全氟乙烷和丁烷的一些反应

近年来,以锌为催化剂用超声波进行氟烷基化反应已有不少报道,但反应物限于全氟烷基碘R_F I。对于I(CF_2)_2 I(Ⅰ)、I(CF_2)_4I(Ⅱ)这类α,ω-二碘全氟烷烃未见报道。作者用(Ⅰ)或(Ⅱ)在DMF或THF中,于室温下加入锌粉(锌粉经活化或未活化),立即有气体逸出,若施加超声波,气体更甚。加入碘苯亦无预期产物,这是符合β-断裂、碘极易脱离生成全氟烯烃之说的。     

Photo-induced CdS nanoparticles growth

A photochemical approach on the size control of CdS nanoparticles is presented. CdS nanoparticles were grown using the photo-induced reaction of sodium thiosulfate with Cadmium sulfate, in the absence of any surfactant. Particles of 5.5–11 nm were obtained by changing the illumination time. The dark growth of nanoparticles was negligible, however we found by optical scattering measurements that a ripening phenomenon occurs and the size of nanoparticles slightly increases with time.     

基于氨光化学响应的有机杂化溶胶-凝胶膜

研究了基于有机杂化硅氧烷的氨光化学传感器；实验通过四甲氧基硅烷（TMOS）和二甲基二甲氧基硅烷（DiMe-DMOS）的缩聚，获得以氨基荧光素（AF）为荧光指示探针，对氨有灵敏荧光响应的溶胶－凝胶敏感膜；实验考察了溶胶先驱体、各种比例杂化硅氧烷在玻璃支撑体上成膜后对体系pH、NH3浓度和响应时间的变化规律，发现DiMe-DMOS含量的变化改变杂化膜的极性，并使得敏感性对NH3有高荧光响应值，而对体系的pH不响应；实验结果表明在pH8.4，0.1mol/L磷酸盐缓冲溶液中，氨质量浓度与其相应的荧光强度在0．5－60mg/L范围内呈良好的线性关系，敏感膜对NH3的95％响应时间为4min，常见的共存物质如氨基酸、胺和金属离子对NH3测定未见有明显的干扰。     

Stability of twisted diarylnitroxides: Photochemical tests

Photochemical stability and possible routes for photodegradation of twisted diarylnitroxides were determined. It was shown that quantum yields for twisted diarylnitroxides fall in the range typical for the best representatives of alkylnitroxides providing an additional support that twisting of the phenyl ring from the N-O conjugation plane constitutes an efficient route for increasing thermo and photo stability of the nitroxides.     

Influence of shape and surface properties of microstructured reaction areas on the deposition of silica

Differently shaped reaction areas for silica deposition were created by photochemical grafting of hydrophobic poly(acrylic acid 2-ethyl-hexylester) as barrier and a hydrophilic polymer employing a mask having hexagons, pentagons, squares and stripes. Poly(ethylene glycol), poly(acrylic acid), branched and linear poly(ethylene imine) and linear poly(methylpropylene imine) have been applied as hydrophilic polymer in the reaction area. These patterned films have been used in silica mineralization experiments by dipping them into a silica precursor solution. Investigations of the polymer films and silica depositions have been done by contact angle measurements, ellipsometry and scanning electron microscopy (SEM). Silica deposition occurs only in the hydrophilically coated areas, resulting in regular arrays of lens-like silica particles. There are only minor differences due to the shape of the reaction area. The influence of the different hydrophilic polymers can be explained by their wetting behaviour.     

新光敏剂亚甲蓝的溶液状态研究

本文应用光谱法研究了亚甲蓝作为一种新的光化学治疗增敏剂在水溶液中的聚集状态。应用Ｋａｓｈａ理论探讨了光敏剂聚集状态与光谱特征间的关系，求出光敏剂亚甲蓝在水溶液中的二聚体间面间距离为ｒ＝１４．０９，面间夹角为θ＝８３°。探讨了表面活性剂、β－环糊精添加物质对亚甲蓝溶液状态的影响。并初步研究了其对亚甲蓝光化学性质的影响，结果认为：β－环糊精对亚甲蓝具有光稳定性作用，试探讨了光化学特性与光敏剂在光化学治疗有效性间的关系。