南极冰藻Chlamydomonas sp. L4的UV-B辐射效应研究

实验研究了从南极采集的冰藻Chlamydomonas sp. L4经强UV-B辐射胁迫后的生物学效应及逆境适应性.研究显示,经过强UV-B胁迫,冰藻L4细胞内迅速产生大量的活性氧,丙二醛含量升高;同时,SOD活性快速提高,使活性氧和丙二醛含量维持在细胞容许范围之内.膜脂肪酸成分分析发现不饱和指数增加了近4倍,膜流动性增加 ,从而维持膜的正常功能.光学显微镜、扫描和透射电镜观察表明,UV-B辐射使细胞体积显著增大,黏性多糖分泌增多,细胞壁增厚,未知黑色颗粒密度增加,L4可能通过上述结构变化把 UV-B屏蔽在胞外.脂肪颗粒的增加是细胞在逆境生存的能量保障.此外,细胞中类囊体片层、线粒体和细胞核等结构基本没有变化,维持细胞基本的代谢和能量供应.     

注硅对SIMOX材料性能影响的研究

首先采用注硅的方法改进sIMOx（注氧隔离）SOI（绝缘体上硅）材料，对硅注入在SIMOX材料的绝缘埋层中形成的纳米硅团簇的条件和纳米团簇的结构进行了论述。并对埋层结构与抗辐射性能的机理进行了分析。最后，对利用注硅改进的SIMOX材料制备的MOSFET的辐射特性进行了报道。     

关于保护臭氧层的基本知识

臭氧层（ozonelayer）距离地面15－50公里的大气平流层中，集中了地球上90％的臭氧所构成的气体层。臭氧层能吸收对生物生长有害的波长小于295urn的太阳紫外线（UV－C），和大部分波长为295～320urn的紫外线（UV－B），才能使地球上的人类与生物得以正常生长和世代繁衍。臭氧消耗（ozonedepletion）平流层中的臭氧，因某些自然和人类来源的化学物质的化学作用而遭受的破坏。这种破坏由于大气中上述这类物质的增多而日益加剧，在南极上空已形成近千万平方公里的臭氧空洞。臭氧层破坏（消耗）已成为当今全球环境问题之一。消耗臭氧物质（oz…     

气氛对γ射线辐照氟橡胶降解产物的影响

氟橡胶F2311[偏氟乙烯和三氟氯乙烯（1：1）共聚物]在真空、氮气、空气三种气氛条件下经50－1000kGy剂量γ射线辐照发生降解反应,辐射降解产物用GC－MS、离子选择性有、原子吸收光谱、红外光谱等方法分析测试。产生和H2（在空气气氛中除外）、HF、HCl、CO2等气体的量随剂量的增加而增大;在空气气氛中剂量达到500kGy时产生的H2的量为最大,剂量再增加时逐渐减小;氮气的存在对F2311的幅射降解反应具有一定的抑制作用。F2311辐照后产生－CF＝CH－、－CF＝CF－、＞C＝O等基团。     

交流等离子体显示屏放电的瞬态辐射特性研究

为深入理解彩色交流等离子体显示屏的气体放电机制及提高器件性能，对三元混合气体He-Ne（26％）．Xe（3．7％）放电的辐射光谱组成和光谱线的瞬态过程进行了实验研究。通过采用高速增强型CCD（ICCD）和光电倍增管（PMT）测量混合气体不同压强时，在一个维持电压脉冲期间，放电所产生的真空紫外和红外各主要谱线的强度随时间的变化，研究了充气压强对谱线强度、辐射延迟、辐射持续时间的影响，并分析了放电产生的真空紫外辐射总强度和可见光光谱线强度随充气压强的变化关系。实验结果表明，随着充气压强的提高，真空紫外和红外光谱辐射延迟缩短，辐射持续时间减小，并且真空紫外辐射总强度增大，可见光强度减小。     

胸腺素α1基因在钝顶螺旋藻中的表达

将钝顶螺旋藻（Spirulina platensis）在24℃培养，并经2mmol/L EDTA预处理16－24h，以本实验室构建的基因整合平台系统供体质粒pEUTISI进行超声波转化螺旋藻，经筛选获得了具G418抗性的转化藻株。通过PCR扩增和Southern杂交证实，pEUTISI中目的的基因UB－Tα1和nptII基因已整合到钝顶螺旋藻染色体上。转化藻株经45℃热诱导40min后，进行蛋白质SDS－PAGE电泳和Western blot，杂交结果证实，外源胸腺素α1基因在螺旋藻中得到有效表达。     

辐射合成DMMC/AM/AA三元共聚两性高吸水性树脂

采用辐射法合成了DMMC／AM／AA新型三元共聚高吸水性树脂，其中2－甲基丙烯酰氧乙基三甲基氯化铵（DMMC）作为阳离子单体，丙烯酸（AA）作为阴离子单体，丙烯酰胺（AM）作为非离子型单体被使用。得到的树脂具有优异的吸水能力，最大吸水率达3200g/g。研究了辐照总剂量与剂量率、AA中和度、单体浓度、单体组成与比例对树脂吸水性能的影响。DMMC／AM／AA新型三元共聚两性高吸水性树脂辐射合成的适宜条件为：总剂量3kGy,AA中和度80％，总单体浓度2．5mol/L-3.0mol/L，n(AM):n(DMMC):n(AA)=0.8:1:3.8。     

第三代半导体或将引发又一次照明革命

事件：继硅（si）引导的第一代半导体和砷化镓（GaAs）引导的第二代半导体后，以碳化硅（SiC）、氮化镓（GaN）、氧化锌（ZnO）、金刚石、氮化铝（AlN）为代表的第三代半导体材料闪亮登场并已逐步发展壮大。与第一、二代半导体材料相比，第三代半导体材料具有更宽的禁带宽度，高的击穿电场、高的热导率、高的电子饱和速率和更高的抗辐射能力，因而更适合制作高温、高频、抗辐射及大功率器件。此外，第三代半导体材料由于具有发光效率高、频率高等特点，因而在一些蓝、绿、紫光的发光二极管、半导体激光器等方面有着广泛的应用。从目前第三代半导体材料和器件的研究来看，较为成熟的是碳化硅SiC和GaN半导体材料，而Zn0、金刚石和A1N等宽禁带半导体材料的研究尚属起步阶段。     

注硅工艺对UNIBOND SOI材料抗辐照性能的影响

SOI材料天然具有抗瞬时辐射的能力，而通过特定的改性处理后，SOI的抗总剂量能力也可以得到大幅度的提高。SOI材料主流的制备方法包括SIMOX（注氧隔离方法）和UNIBOND SOI（智能剥离方法制备）。在SIMOX SOI的抗辐射加固领域，采用氮离子注入、氮氧共注入以及硅离子注入的方法都曾取得过很有效的结果。采用硅离子注入的方法对UNIBOND SOI进行了抗总剂量加固。采用P-MOS的表征方法对加固前后的样品进行了比较和分析，在HP-4155B半导体测试仪上得到的I-V曲线和提取的参数表明，注入的离子有效地减少了埋层中积累的正电荷得，圆片抗总剂量能力得到了大幅度提高。初步的理论分析表明是注入的硅离子形成的纳米团簇起到了俘获正电荷的作用。     

纳米硅/单晶硅异质结二极管的电学特性

利用高真空PECVD系统在p型单晶硅上沉积掺磷n型纳米硅薄层（nc-Si:H),形成纳米硅／单晶硅Np异质结二极管,通过C－V和J－V测试研究了二极管的电学性质。C－V特性指出该异质结为突变型。J－V特性表明二极管具有很好的温度稳定性和整流特性。正偏压时二极管存在两种输运机制：小偏压时（＜0．8V）二极管电流由耗尽层纳米硅薄层一侧的载流子复合过程决定,纳米硅薄层由于能带弯曲而减小了禁带宽度,这是该二极管温度稳定性好的根本原因;大偏压（＞1．0V）时电输运符合电荷限制电流（SCLC）模型。负偏压时电流主要来自空间电荷区中的产生电流。     

Radical generation on hydroxyapatite by UV irradiation

The radical species generated on hydroxyapatite (HAp) samples by UV irradiation were investigated and compared by electron spin resonance (ESR) with spin trapping reagent. It was recognized that ^·OH and O₂^·− species were produced on HAp after heat treatment at 200 °C (HAp200) by UV irradiation. It was assumed that ^·OH radical was generated from H₂O on HAp200 by photo-induced excitation with UV irradiation as well as O₂^·− from O₂ in air. These radicals were very active. On the other hand, few radical species were produced on HAp after heat treatment at 1150 °C by UV irradiation. The difference of generation of active radical species on HAp by UV irradiation must influence the activity for the photocatalytic decomposition of organic compounds.     

加热和光照条件下Ru/TiO2催化二氧化碳甲烷化研究

本研究利用浸渍法制备了Ru/TiO₂催化剂, 并在光照和加热两种条件下考察了其催化二氧化碳与氢的反应, 发现催化剂在两种条件下均可引发显著的甲烷化反应(CO₂ + 4H₂ → CH₄ + 2H₂O)。结果显示, 在光照和加热(150~350℃)条件下, CH₄为唯一含C产物。而在更高温度的加热条件下(>400℃)除了生成CH₄外, 还产生少量CO副产物, 表明反应温度对产物选择性有显著影响。随着反应温度由150℃升高到550℃, 对于不同负载量的担载Ru催化剂, CO₂转化率均先增加后降低, 其中在Ru担载量为1.5wt%Ru/TiO₂催化剂上CO₂转化率在350℃时达到最高, 为77.58%。而在温度>400℃条件下, CO的选择性也随反应温度的升高而逐渐增加。综合反应结果和XRD、XPS和N₂吸附-脱附等表征结果, 发现二氧化碳与氢在光照和加热条件下(150~550℃)反应机制不同。在光照条件下, 光激发电子首先被金属Ru捕获, 进而将吸附在金属Ru上的二氧化碳还原, 活性物种经由RuC中间体形成CH₄。而加热条件下(150~550℃), H₂先被Ru活化成氢原子, 氢原子还原吸附在催化剂表面的CO₂形成RuC中间体, 最后RuC中间体进一步加氢生成CH₄。虽然在两种反应条件下经历相同的中间体, 但是中间体的形成路径不同, 即反应物CO₂被活化的方式不同, 因而产物选择性不同。     

Laser-induced removal of a dye C.I. Acid Red 87 using n-type WO3 semiconductor catalyst

Water contamination by organic substances such as dyes is of great concern worldwide due to their utilization in many industrial processes and environmental concerns. To cater the needs for waste water treatment polluted with organic dyes, laser-induced photocatalytic process was investigated for removal of a dye derivative namely Acid Red 87 using n-type WO₃ semiconductor catalyst. The degradation was investigated in aqueous suspensions of tungsten oxide under different experimental conditions using laser instead of conventional UV lamp as an irradiation source. The degradation process was monitored by measuring the change in dye concentration as a function of laser irradiation time by employing UV spectroscopic analysis. The degradation of dye was studied by varying different parameters such as laser energy, reaction pH, substrate concentration, catalyst concentration, and in the presence of electron acceptors such as hydrogen peroxide (H₂O₂), and potassium bromate (KBrO₃). The degradation rates were found to be strongly dependent on all the above-mentioned parameters. Our experimental results revealed that the dye degradation process was very fast (within few minutes) under laser irradiation as compared to conventional setups using broad spectral lamps (hours or days) and this laser-induced photocatalytic degradation method could be an effective means to eliminate the pollutants present in liquid phase. The experience gained through this study could be beneficial for treatment of waste water contaminated with organic dyes and other organic pollutants.     

Photodegradation of organic light-emitting devices observed in nitrogen-filled environment

Degradation of organic light-emitting devices (OLEDs) upon ultraviolet (UV) irradiation has been studied by measuring luminance-voltage (L-V) and current-voltage (I-V) characteristics of the devices in a nitrogen-filled glove-box. Photo-oxidation or reaction is no longer the main origin of the degradation for the devices protected by nitrogen. Conventional double-layer OLEDs with tris(8-hydroxyquinoline) aluminum (Alq₃) as the electron transport material and single-layer devices containing Alq₃ as the only organic material exhibit different degradation behaviors: both L-V and I-V characteristics degrade severely for the irradiated double-layer devices, whereas whether I-V degrades or not in a single-layer device is closely related to the species of the charge carriers flowing in the device. By comparing electroluminescent and photoluminescent degradation behaviors of the single-Alq₃-layer devices, we conclude that lowered fluorescent quantum efficiency and hole current after UV irradiation are two origins of the degraded characteristics of the devices isolated from the moist environment.     

Global ultraviolet spectra derived directly from observations with multichannel radiometers

Some general features of multichannel filter radiometers operating in the UV region of the solar spectrum are reviewed with emphasis on calibration problems that are due to incomplete knowledge of responsivity in the UV-B region. An alternative calibration procedure that is able to generate a full UV spectrum obtained by a constrained inversion method is presented. Accuracy of such spectra is assessed with simulated and with real data. A comparison between customary calibration and an alternative procedure is made in terms of monochromatic UV-B irradiance and CIE dose rate (CIE is the Commission Internationale de l'Eclairage) and indicates that irradiances are estimated within 8% accuracy with solar zenith angles as great as 60 degrees and that dose rates are within 6% for any solar zenith angle. The advantage of having an additional channel in the UV-B region is considered.     

Surface morphology control of zirconia thin films prepared using novel photochromic molecules

A new photochromic ZrO₂ precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The density functional theory (DFT) calculation has identified that the structure of the synthesized precursor molecule changed by UV irradiation. Four types of thin films were prepared using the ZrO₂ precursor solution with and without UV irradiation and applying an electric field. It was found that the surface morphology of thin films changed by applying UV irradiation to the precursor solution and an electric field.     

Photoswitching of electron transfer property of diarylethene–viologen linked molecular layer constructed on a hydrogen-terminated Si(111) Surface

An organic monolayer with diarylethene and viologen moieties as a photochromic and an electroactive group, respectively, was constructed on a hydrogen-terminated Si(111) surface by sequential surface reactions. Photoswitching behaviour of electron transfer from the Si electrode to viologen moiety, larger and smaller current after UV and visible irradiation, respectively, was observed. This photoswitching behaviour can be explained by a change in molecular conductivity of diarylethene moiety, which separates Si surface and viologen moiety, as a result of ring closing and opening induced by UV and visible irradiation, respectively.     

UV photooxidation induced structural and photoluminescence behaviors in vapor-etching based porous silicon

In this paper, we investigate the effect of UV irradiation on Vapor-Etching (VE) based Porous Silicon (PS) structure and luminescence under controlled atmosphere (N₂, air, O₂). The oxidation evolution is monitored by Fourier transform infrared (FTIR) spectroscopy. FTIR measurements show that the SiH_x bond, initially present in the freshly prepared PS layers, decreased progressively with UV irradiation time until they completely disappear. We found that this treatment accelerates the oxidation process. SiO_x structures appear and gradually become dominant as regard to the SiH_x species, while UV irradiation is in progress. Generally, the photoluminescence (PL) intensity of the PS layer decreases instantaneously at the starting by the UV excitation and stabilizes after a period depending on the ambient gas and the specific surface area of the porous structure. Further UV exposure leads to a linear decrease of the PL intensity due to change of surface passivation from SiH_x to O_ySiH_x. After less than 100 min of UV irradiation, the PL intensity exhibits an exponential decay. UV exposure in air and O₂ leads approximately to the same PL behavior, although faster PL intensity decrease was observed under O₂-rich ambient. This was explained as being due to intense hydrogen desorption in presence of oxygen. Correlations of PL results with FTIR measurements show that surface passivation determine the electronic states of silicon nano-crystallites and influence the photoluminescence efficiency.     

Photocatalytic activity of nanosized TiO2 thin film prepared by magnetron sputtering method

Nanosized TiO2 thin film on the substrate such as stainless steel plate and slide glass film were prepared by magnetron sputtering method, and these TiO2 thin films were characterized by field emission-scanning electron microscopy (FE-SEM). Photocatalytic activity for Methyl-ethyl-ketone (MEK) and acetaldehyde were measured using a closed circulating reaction system through the various ultra violet (UV) sources. From the results of SEM images, nanosized TiO2 thin film was uniformly coated on slide glass, ranging from 360 nm to 370 nm. Photocatalytic activity of MEK over TiO2 thin film on stainless steel plate did not occur by UV-A irradiation, but was efficiently decomposed by UV-B and UV-C. Also, acetaldehyde could be decomposed than MEK. The effect of sputtering conditions on their structure and photocatalytic activities were investigated in detail.     

Delayed onset of photochromism in molybdenum oxide films caused by photoinduced defect formation

We report the photochromic properties of amorphous MoO₃ films deposited by dc sputtering with different O₂ flow rates. The kinetics of film coloration under UV light irradiation is determined using optical transmission spectroscopy. Changes in the absorbance and refractive index were derived from the analysis of transmittance spectra. The absorbance spectra exhibited a growing broad peak centered around 830 nm, which was induced by the UV irradiation. In the early stages of irradiation, the absorbance of the films did not change but their refractive indices did change. This induction time was correlated with the O₂ partial pressure during the film deposition, which was controlled by the O₂ flow rate. The origins of this observation are discussed.