激发态质子转移分子2-（2′-羟基苯基）苯并噻唑在不同溶剂中的光谱特性

观测了2-（2′-羟基苯基）苯并噻唑（HBT）在不同极性溶剂中的吸收光谱和荧光光谱,详细研究了溶剂极性对HBT发生激发态分子内质子转移（ESWT）影响的机制。吸收光谱表明在常态条件下,HBT在各种溶剂中都以烯醇式构型和酮式构型共同存在,但以烯醇式构型占绝大多数。荧光光谱表明在纯环己烷溶剂中,HBT被紫外光激发时,绝大多数烯醇式构型发生ESIPPT转变为酮式构型,分子的ESIPT效率最大。在含有乙醇的极性溶剂中,HBT烯醇式会形成溶剂化的烯醇式构型,阻碍分子发生ESIPT反应。溶剂中乙醇含量愈多极性愈强,溶剂化烯醇式的成份就愈多,HBT的ESIPT效率就愈低。以400nm光激发HBT溶液时,在510nm处发现酮式构型荧光,从而确认了400nm处的弱吸收是酮式构型的吸收;且在436和456nm处还有新的荧光峰,分析其可能来源于酮式构型去质子化阴离子的发射。     

激发态质子转移分子2-(2'-羟基苯基)苯并噻唑在不同溶剂中的光谱特性

观测了2-(2’-羟基苯基)苯并噻唑(HBT)在不同极性溶剂中的吸收光谱和荧光光谱,详细研究了溶剂极性对HBT发生激发态分子内质子转移(ESIPT)影响的机制。吸收光谱表明在常态条件下,HBT在各种溶剂中都以烯醇式构型和酮式构型共同存在,但以烯醇式构型占绝大多数。荧光光谱表明在纯环己烷溶剂中,HBT被紫外光激发时,绝大多数烯醇式构型发生ESIPT转变为酮式构型,分子的ESIPT效率最大。在含有乙醇的极性溶剂中,HBT烯醇式会形成溶剂化的烯醇式构型,阻碍分子发生ESIPT反应。溶剂中乙醇含量愈多极性愈强,溶剂化烯醇式的成份就愈多,HBT的ESIPT效率就愈低。以400 nm光激发HBT溶液时,在510 nm处发现酮式构型荧光,从而确认了400 nm处的弱吸收是酮式构型的吸收;且在436和456nm处还有新的荧光峰,分析其可能来源于酮式构型去质子化阴离子的发射。     

7-羟基喹啉在二甲基亚砜中的荧光光谱

7-羟基喹啉(7-HQ)是一种具有激发态质子转移(ESPT)效应的有机分子。它溶于乙醇溶剂中,在紫外光的激励下,将发生ESPT反应,荧光光谱出现2个荧光带。7-HQ溶于二甲基亚砜(DMS)溶剂中,则不能发生ESPT反应,其荧光光谱只出现单一荧光带。但样品被强紫外光照射后,其荧光光谱也出现2个荧光带。文章首次报道了这一现象,并通过对7-HQ的乙醇、二甲基亚砜和二甲基甲酰胺溶液的吸收光谱和荧光光谱的研究,探讨产生这一现象的机理。认为7-HQ溶于DMS中被强紫外光照射后荧光光谱的变化是由于DMS被光解并生成水而使7-HQ发生ESPT反应的结果。     

非晶态As2S8半导体薄膜的光致结构变化效应研究

实验研究了非晶态As2S8半导体薄膜在光照、退火-光照和退火-光照-退火-光照关连作用下的光折变效应及淀积态与退火态两种膜系光致体积变化现象.采用棱镜耦合技术、Raman光谱和X线衍射测试技术,确认了As2S8薄膜经紫外光辐照后薄膜密度增高、折射率增大的现象.实验表明,淀积态As2S8薄膜经紫外光照后,折射率变化的最大增量可达到0.06,而退火态As2S8薄膜经紫外光照射后,其折射率最大变化比前者要小一个数量级,约为0.005 7.淀积态和退火态两种膜系紫外光照后,体积缩小,这与As2S3非晶态薄膜的情况不同,体积变化率分别为－3.5%和－2.1%.实验还显示,退火态的As2S8薄膜存在折射率完全可逆现象.     

室温生长ZnO薄膜晶体管的紫外响应特性

在室温下采用射频磁控溅射法制备了以ZnO薄膜为沟道层的薄膜晶体管(TFTs).研究表明ZnO薄膜在紫外区具有较高的吸收率,并且ZnO-TFTs对紫外光照射较为敏感.因此,进一步深入研究了ZnO-TFTs紫外光照下的输出和转移特性,结果表明,紫外光照将引起较为明显的光响应电流,且经过光照的器件在光源移除7天后,ZnO沟道层中仍能观察到残余电导现象,其原因可以归结为紫外光辐射在ZnO沟道层中引入了一定数量的氧空位施主态缺陷.     

表面修饰ZnO纳米线紫外光响应的增强效应

制备了基于单根ZnO纳米线的紫外光探测原型器件,并研究了聚苯乙烯硫酸钠表面修饰对器件紫外响应特性的影响.研究发现,在相同的紫外光照射条件下,表面修饰后的器件对紫外光的探测灵敏度比修饰前提高了3个数量级.I-V特性研究表明,修饰前后器件在光照时的电导没有明显变化,但修饰后器件的暗电导却下降了3个数量级.这说明通过表面修饰降低探测器的暗电导是提高紫外光探测器灵敏度的一条重要途径. 关键词： 紫外光探测器 纳米结构 ZnO 表面修饰     

紫外光下纳米TiO2薄膜亲水性机理的电化学研究

利用溶胶 凝胶方法在透明导电玻璃ITO (SnO2 ∶In)表面制备纳米TiO2 薄膜 ,XRD谱图表明TiO2 是锐钛矿晶型 ,AFM (Atomic Force Microscope)测得薄膜表面粒子约为 10 0nm .研究了ITO表面纳米TiO2 薄膜的光致亲水性变化 .通过循环伏安技术测定TiO2 薄膜电极在 2 5 3.7nm的紫外光照射后的电化学行为推测光致亲水性机理 .发现在紫外光照射一定时间后 ,TiO2 薄膜电极的循环伏安图在 +0 .0 35V处出现新的氧化峰 ;且随光照时间的增加 ,氧化峰的峰电流增大 ,溶液中的溶解氧对峰电流的大小有明显影响 .实验表明 ,在紫外光照下电极表面有Ti3 + 产生 ,证实了TiO2 薄膜的光致亲水性转变过程与Ti3 + 的生成导致的表面结构变化有关     

光诱导辣根过氧化物酶催化活性变化及机理研究

辣根过氧化物酶(HRP)是广泛应用的一种生物催化剂,其光照后HRP酶活性变化的机理还未见报道。利用紫外-可见(UV-Vis)、同步荧光、圆二色(CD)光谱研究了光对HRP催化活性及酶活变化机制。实验结果表明：光照射HRP可促使其发生还原反应,同时其催化活性会发生变化。UV-Vis吸收光谱数据显示,光照射后HRP的Soret带403 nm最大吸收峰红移、Q带498 nm处氧化峰强度下降,说明经光照射HRPFe(Ⅲ)被还原为HRPFe(Ⅱ)。不同波长对光照还原影响程度为280 nm>254 nm>498 nm>403 nm;酶活为403 nm>498 nm>254 nm>280 nm;280 nm波长光照射下,Phe,Trp,Tyr和Cys四种游离氨基酸以及谷胱甘肽的加入均对光照还原有促进作用。酶活性与光照还原程度紧密相关,因Fe(Ⅱ)无法提供空轨道与H₂O₂配位,所以光诱导Fe(Ⅲ)还原导致酶活下降。同步荧光和圆二色光谱揭示了光照还原后HRP血红素的构象发生了变化,构象的变化也是光诱导酶活变化的原因之一。紫外光影响酶活性下降的因素为光照引发活性中心Fe(III)还原,蛋白质构象变化的贡献。研究结果对进一步了解光对含血红素蛋白(酶)结构和功能的影响有重要的理论和实际意义。     

自然光和紫外光照条件下膜材红外光谱变化

可降解树脂包膜控释肥是目前肥料领域的研究热点之一。研究从可降解包膜材料实际施用环境着手,采用傅里叶衰减全反射红外光谱技术(ATR-FTIR),表征包膜肥料膜材自然光和紫外光照条件的降解差异,通过对聚乙烯/疏水纳米二氧化钛、聚乙烯/亲水纳米二氧化钛和纯聚乙烯包膜的谱图来研究膜材在光照前后的结构变化特征,进而对膜材的降解行为做出判断。结果表明,在紫外光和自然光分别照射下,包膜降解过程中的官能团种类没有因光催化剂的加入而受到影响,而光催化剂的加入对官能团的变化程度有显著影响,依次为：聚乙烯/疏水纳米二氧化钛复合包膜>聚乙烯/亲水纳米二氧化钛复合包膜>纯聚乙烯包膜。另外,不同照射光源对包膜的分子结构的影响有所区别。自然光条件照射的降解过程中,包膜的聚乙烯碳链上在形成氢过氧化物的同时发生了交联反应生成含醚键的物质,接着继续氧化生成含羰基的化合物,最终羰基的存在促进包膜的进一步分解;紫外光条件照射下,光照产生的活性氧物种局部浓度大,攻击聚合物碳链的能力强,聚乙烯长链烷基断裂很快氧化生成含有羰基基团的中间产物。紫外光条件的照射实验未能全面反映包膜在自然光条件下的降解行为。     

六硝基菧的紫外光解

采用紫外-可见光谱、X-射线光电子能谱、电子自旋共振谱及质谱等实验手段研究了固态含能材料六硝基菧（HNS）在365 nm紫外光照下的光解机理。HNS的乙腈溶液被紫外光照射后,在310 nm和350 nm处出现了两个新的吸收峰。X-射线光电子能谱实验中,N元素和O元素的窄谱图分别在401 eV和528 eV处出现了新峰。质谱分析则显示在质荷比403和329处出现了两个新的特征离子峰。实验结果表明:CNO2键断裂、分子中NO2基团异构化为亚硝基,以及随后的NO消去等过程均可能发生在六硝基菧的紫外光解反应过程中。     

掺铥光纤γ射线辐照效应实验研究

面向2μm掺铥光纤激光器的空间应用,本文针对典型商用掺铥光纤(TDF)开展了γ射线辐照效应实验研究。利用~(60)Co源放射的γ射线,对由5段同批次Nufern公司SM-TDF-10P/130-HE型TDF样品搭建的2μm光纤激光器进行总剂量为9.0 krad(Si)、剂量率为0.5~3.0 rad/s的辐照效应在线测试。结果表明,TDF的出光性能在辐照过程中出现了显著衰减,衰减幅度随着剂量率的上升而增大。通过对TDF样品在辐照前和辐照后的吸收光谱进行对比测试,观察到在经过总剂量9 krad(Si)的γ射线辐照后,TDF对793 nm泵浦光的吸收峰接近消失。对前述经历γ辐照之后的TDF样品进行2 h的793 nm泵浦光漂白实验测试,未见其出现性能恢复现象。可见,面向空间应用的该典型掺铥光纤需大力提高耐空间辐射性能。     

Photoluminescence degradation mechanism of BaMgAl10O17：Eu2＋ phosphor by vacuum ultraviolet irradiation

<正>A real high power vacuum ultraviolet light source is applied to the investigation on the vacuum ultraviolet irradiation degradation of BaMgA₁₀O₁₇:Eu²⁺ phosphor.The degradations of emission intensity and color quality of the sample are clearly observed after irradiation.It reveals that the oxidation of Eu²⁺ during irradiation is partly responsible for the degradations.The excitation and absorption spectra show that some traps generated during irradiation have negative influence on the luminescence of sample and these traps have been identified as positively charged oxygen vacancies by positron annihilation.The investigations on host emission and decay curve further confirm that these oxygen vacancies are involved in the perturbation of energy transfer from the host to Eu²⁺ and finally result in the degradation.     

Effect of gamma ray irradiation on optical properties of Nd doped phosphate glass

The effect of gamma irradiation in the dose range of 5-500 kGy on the optical absorption and luminescence spectra of Nd doped phosphate glass is reported. The spectral absorption of this glass before and after gamma irradiation was measured in the spectral range 300-900 nm at room temperature using spectrophotometer and synchrotron beamline. Drastic increase in absorption was noted below 600 nm after gamma irradiation, which was dependent on the dose of irradiation. Additional absorption (AA) spectra of irradiated sample shows generation of two absorption bands below 600 nm, which finally became one very broad band peak with increased intensity at irradiation dose of 500 kGy. AA spectra also show the presence of negative peaks at the location of absorption peaks of Nd³⁺. Photoluminescence of Nd doped phosphate glass shows two strong bands which decreases to a very low intensity with a red shift after gamma irradiation. These results indicate that irradiation produces different kinds of defects in the glass material along with conversion of valence state of Nd³⁺ to Nd²⁺. This change was found irreversible at room temperature.     

Features of radiation-induced changes in the diffuse reflectance spectra of modified titanium-dioxide powders

Changes in the diffuse reflectance spectra of titanium-dioxide micropowders (initial, modified by nanoparticles, treated with oxidants such as potassium peroxoborate and sodium peroxide, or ultraviolet irradiated in an oxygen atmosphere) in the range 0.3–2.1 μm after irradiation with ultraviolet light, electrons, or protons are analyzed. The general and distinctive features of changes in the spectra in the visible and near infrared regions are revealed and an explanation of the obtained data is proposed.     

Formation and destruction of polyelectrolyte microcapsules modified by rhodamine 6G

Polyelectrolyte capsules with Rhodamine 6G molecules included into the shell are obtained in this work. The inclusion of dye molecules into the shell can provide the destruction of capsules by photosensitization. Measurements of the dye fluorescence intensity in the shell show that the energy of photoexcited molecules is effectively dissipated by the surrounding organic matrix. The capsule suspension is laser irradiated in the absorption band of Rhodamine 6G molecules. Measurements of the size distribution of capsules before and after laser irradiation reveal that the capsules are destroyed by laser illumination.     

Microstructure change in poly(ethersulfone) films by swift heavy ions

PES membrane of thickness 25 μm was irradiated by Cl⁹⁺ ions of energy 100 MeV at IUAC, New Delhi. Microstructure changes due to exposure to high-energy ions were investigated by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/vis) absorption spectroscopies, X-ray diffraction technique and by dynamic mechanical analysis (DMA). A significant loss of crystallinity is observed by the XRD data. Particle size or grain size calculated using Scherrer formula indicates measurable change in particle size of irradiated samples. The polymer chain scissions and structure degradations are expected to occur for irradiated samples. Optical properties of the films were changed due to irradiation that could be clearly seen in the absorption spectra. FTIR does not show the remarkable change in the irradiated samples, but there is some change in the surface roughness observed by AFM.     

高能Ar离子辐照PET引起的光吸收变化研究

采用紫外–可见光吸收技术分析和研究了35MeV/uAr离子辐照聚酯膜引起的光吸收改性.结果表明,Ar离子轰击聚酯膜时引起了碳键的共轭体系形成,从而导致了紫外–可见光区域中光吸收明显增加,光吸收增加的幅度依赖于离子的照射剂量、离子在样品中的平均电子能量损失以及光的波长,剂量越高,电子能损越大,光吸收增幅越大;而光的波长越长,光吸收的增加则越不明显.利用测量到的光吸收曲线,同时还定量地研究了各种辐照条件下聚酯膜的光能隙和碳原子团的尺寸.     

The colouration by 60 Co-gamma rays of NaCl and KCl crystals doped with europium ions

Pure and europium doped NaCl and KCl crystals have been irradiated with 60 Co gamma rays and with ultraviolet light. The dose was 10 v kGy and temperatures during irradiation were ambient and liquid nitrogen. The effects of irradiation are determined using optical absorption and thermoluminescence. The role of the europium dopant is compared for the two materials. Factors investigated include the temperature of irradiation, the concentration of the dopant and the state of impurity aggregation and precipitation. A link is indicated between impurity precipitates and UV stimulated thermoluminescence.     

紫外辐照对聚醚酰亚胺薄膜介电性能的影响北大核心CSCD

研究了不同紫外辐照时间对聚醚酰亚胺(PEI)薄膜介电性能的影响。采用FT-IR和SEM表征了PEI薄膜的分子结构和微观形貌。结果表明,紫外辐照后PEI薄膜在1742cm^(-1)处的吸收峰比原薄膜增大,说明PEI分子链中的C=O基团随辐照时间的增加而增加,并在薄膜表面产生了微裂纹。对PEI薄膜的介电性能进行的研究结果表明,随着紫外辐照时间的增加,PEI薄膜的介电常数和介电损耗增大,而表面电阻率下降,体积电阻率基本不变。并随紫外辐照时间的增加,直流击穿强度呈先增加后降低的趋势,一定辐照剂量可使薄膜发生交联反应,使击穿场强较原薄膜提高20%以上。