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1.
Under UV irradiation the photoreaction of pyrimidine bases in aqueous solution hasdisclosed three mpes of reactions, namely: (a) nucleophilic addition ofwateT, ethanol, orhydrogen cyanide at the 5,6-double bond; (b) dimerization by addition at the samedouble bond; (c) ring cleavage. It has been reported' that the presence of phosphatesaltered the course of the photolysis process of pyrimidine bases and derivatives under theirradiation of low pressure mercury lamp (LPML, 254 "m), but the role… 相似文献
2.
Theph0tolysis0f2-meth0xycytosineinph0sphate-buffersoluti0nunderl0wpressuremercurylamp(LPML,254nm)wasrep0rtedasearlyasl963byMoor"wh0foundthatthepresence0fin0rganic0rthoph0sphatealteredthec0urse0ftheph0toIysispr0cess0f2-methoxycytosineandpr0ducedannewc0mp0undI(Schemel).Pith2andShawjconfirmedtheresultofM00r.butthereactionmechanismhadnotbeenelucidated.Inparticular,theroleofph0sphateinthemechanismwasn0tclear.Inaprevi0uspaper'wefoundthatthephot0lysisyieldofnucteobases'nucle0sidesandnucleotides(N… 相似文献
3.
Feng LIN Shao Yong BAI 《中国化学快报》2005,16(9):1158-1160
1, 3-Dimethyluracil (DMU) in phosphate buffered-saline (PBS, pH=8) was irradiated by a medium pressure mercury lamp (MPML) and produced a novel compound C6H9N2O6P. The composition and structure of the compound has been identified by elemental analysis, EIMS, UV, IR, ^1H and ^31P-NMR. 相似文献
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在中压汞灯光照下,无机磷酸盐能促进尿嘧啶水溶液(pH=8)的光解作用(磷酸盐效应),发生嘧啶碱基的光解取代反应,主要光解产物为6-磷酸基尿嘧啶(C4H5N2O6P).通过元素分析,UV,IR,EIMS,1HNMR,13CNMR,31PNMR等测试手段和方法,确定了光解产物的组成和结构.实验表明,在中压汞灯的发射光谱(连续光谱)中,对磷酸盐效应起作用的波长为190~220nm. 相似文献
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Summary: We developed a novel method of producing polymer gels in aqueous solution using UV irradiation. Persulfates were effective photosensitive initiators of polymerization and/or gelation of acryloyl‐type monomers/polymers. The gelation was confirmed by an abrupt increase in light scattering intensity, 〈I(q)〉T, at the gelation point. The gelation method entails significant advantages: it does not need any cross‐linkers, temperature control (heating), and additives except the persulfate.
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Membrane-bound sialic acid may be quantitated by colorimetric determination of formaldehyde released upon mild periodate oxidation. In the presence of washed erythrocyte membranes at 20% suspension the colorimetry based on 3-methyl-2-benzothiazolinone hydrazone has an extinction coefficient of 68.5 mM?1 cm?1. With intact erythrocytes large losses in color yield are experienced with suspensions in excess of 2% (2 × 108 cells/ ml). 相似文献
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Elizabeth Christophy Kari Myli Terrance R. Viegut Jeffrey A. Rzepiela Jeanne M. Hossenlopp 《Journal of photochemistry and photobiology. A, Chemistry》1997,110(3):131-234
The excitation of gas-phase methyl benzoate at 240 nm leads to the observation of phosphorescence. The dispersed phosphorescence spectrum has an assigned origin of 25 270 cm−1 and a prominent C=O progression of 1720 cm−1, consistent with literature reports of gas-phase benzaldehyde spectroscopy. Weaker bands, which correspond to formaldehyde ν17 and ν25, are also evident. Time-resolved IR diode laser absorption spectroscopy has been used to probe formaldehyde. Excitation of methyl benzoate at 222 nm clearly indicates the generation of formaldehyde as a photoproduct. The temporal profile of the formaldehyde signal is consistent with significant nascent vibrational excitation in this product. The ratio of formaldehyde initially in the ground vibrational state to that in the excited vibrational states is estimated to be 0.6 ± 0.1. The proposed elimination mechanisms are analogous to those postulated for the formation of CO2 and acetaldehyde from pyruvic acid. 相似文献
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用紫外光辐照氯金酸、聚乙烯吡咯烷酮(PVP)和纳米金种子的混合溶液, 在室温下用30 min制备出尺度小于100 nm的截角三角形或六边形金纳米盘. X射线能谱和衍射分析表明粒子是以{111}面为盘状面的高纯面心立方金单晶, 红外透射光谱表明金粒子与PVP之间存在作用. 产物的可见吸收光谱表现出纳米盘的各向异性表面等离子体共振吸收峰. 不同实验条件下产物的吸收光谱分析表明: PVP起还原剂和包覆剂的作用; 高强度紫外光加速了反应进行; 种子对反应具有催化作用; 种子的加入量有最佳值, 在该值下纳米盘平均尺度最大(达80 nm), 吸收谱上的面内偶极共振峰位于950 nm处; 种子的加入量超过该值时, 纳米盘尺度变小, 面内偶极共振峰发生蓝移. 相似文献
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在pH 8.2的二乙三胺五乙酸-三羟甲基氨基甲烷(DTPA-Tris)缓冲介质中,通过紫外光照射使NO3-还原为NO2-后,与显色剂反应生成吸收峰位于540 nm波长处的化合物,据此提出了在线紫外光照还原流动注射分光光度法测定海水中硝酸盐。经试验,选择30 g·L-1氯化钠溶液作为载流,所选定的反应圈及样品环的长度依次为180 mm和130 mm。硝酸盐的质量浓度在0.009~3.0 mg·L-1范围内与相应的吸光度呈线性关系,其检出限(3s/k)为4.63μg·L-1。对同一天然海水样品按此法测定其NO3-含量10次,测得其平均值为0.538 mg·L-1,相对标准偏差为0.34%,并求得NO3-的还原率为80%。另在6个海水样品中各加0.50 mg·L-1NO3-标准溶液,按方法做回收试验,测得其回收率在97%以上。 相似文献
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The nanometer films of TiO2 were prepared by sol-gel method on ITO(Indium-tin oxide,SnO2:In) substrate. The TiO2 film was the anatase phase with a particle size of 100 nm from the measurements of X-ray diffraction and AFM(Atomic-Force-Microscope). Electrochemical characteristics of ITO/ TiO2 electrode under UV(ultraviolet)irradiation were investigated using the method of cyclic voltammetry. A new oxidative peak was observed at 0.035 V when the TiO2 electrode was irradiated by 253.7 nm UV light for a certain time. The peak current increased with the irradiation time. It was assumed that the new oxidative peak resulted from Ti3+,which was formed during the UV illumination. The changes of hydrophilicity of the TiO2 thin film on ITO under UV light were also observed. It was assumed that the changes of hydrophilicity of the films may be related with the formation of Ti3+ on the surface when the film was irradiated by UV light. 相似文献
12.
Sheng Lin Cao Ming Li Ye Wei De Lv Guang Wen Pan Ting Ting Zhang Zhong Yang Hu Li Na Liang Yan Zhu 《中国化学快报》2012,23(11):1263-1266
A new and simple method was developed to determine anions in oxalate of analytical reagent grade.After UV photolysis with optimal 1%H2O2 in 10,000 mg/L oxalate in the fabricated photoreactor,sample was directly injected into IC system.Satisfactory linearity,detections limits,good repeatability and spiked recovery were obtained.The method was successfully applied to determine anions in two commercial oxalate samples. 相似文献
13.
Dinghong Gu Li Huang Chunlei Shao Haojie Fang Renxi Zhang Huiqi Hou 《Frontiers of Chemistry in China》2007,2(4):436-441
The photodegradation of organic dye rhodamine B (RhB) in an aqueous solution was studied using a microwave electrodeless UV
lamp (MWUVL). The 185 nm vacuum UV (VUV) intensity of the MWUVL amounted to 12% of the total UV output, about 1.7 times as
high as that of the con ventional low-pressure mercury lamp. An acidic condition was preferred for the degradation of RhB.
Precipitate was generated during RhB degradation when the initial concentration of RhB solution was above 60 mg · L−1. For 100 mg · L−1 RhB at pH 4.0, the mass of precipitate produced was nearly half of the initial amount of RhB in the solution after irradi
ation for 75 min. The corresponding degradation ratio of RhB reached up to 99.4% and COD reduced 77.4%. The photo degradation
of RhB is mainly achieved by direct photolysis of RhB by 185 nm and OH radical oxidation.
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Translated from Journal of Fudan University (Natural Science), 2006, 45(6): 726–731 [译自: 复旦学报 (自然科学版)] 相似文献
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聚1-三甲硅基丙炔膜经紫外线辐照后其氧氮选择性提高,用XPS及水接触角法研究了膜的表面组成对透气性的影响。 相似文献
16.
The interaction of Co(Ⅱ) with BSA under UV C (253.7 nm) irradiation under physiological conditions has been studied by UV-vis spectrum, ultraviolet second-derivative spectroscopy and fluorescence spectrum. The quenching rate constant kq and the association constant Ka were calculated according to Stern-Volmer equation based on the quenching of the fluorescence of BSA by Co(Ⅱ). 相似文献
17.
Jian-yang Zhang Kai-jun Yuan Yuan Chen Steven A. Harich Xiu-yan Wang Xue-ming Yang Alec M. Wodtke 《化学物理学报(中文版)》2007,20(4):345-351
The H+N3 channel in the ultraviolet photodissociation of HN3 has been investigated from 190 nm to 248 nm using the high-n Rydberg H-atom time-of-°ight technique. Product translational energy distributions as well as product angular anisotropy parameters were determined for the H+N3 channel at di?erent photolysis wavelengths. N3 vibrational state distribution has also been derived from the product translational energy distribution at these wavelengths. Above photolysis wavelength 225 nm, HN3 predominantly dissociatethrough the repulsive state. Below 225 nm, a new slow channel starts to appear at 220 nm in addition to the existing channel. This channel is attributed to a ring closure dissociation channel to produce the cyclic N3 product. As photolysis energy increases, this new channel becomes more important. 相似文献
18.
紫外光辐照聚丙烯及其应用研究 总被引:1,自引:0,他引:1
通过红外光谱,热分析及熔体流动速率的研究了紫外光辐照对聚丙烯的化学结构和物理性能的影响。结果表明:在紫外光辐照下PP发生了快速光氧化,分子链中引入了COOH,C-OH,C=O等极性在团;紫外光强为68μW/cm^2时,辐照对PP分子量影响较小,紫外光强为130μW/cm^2时,辐照可引起PP明显的光降解。 相似文献
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高湿度下紫外光辐射对sol-gelTiO_2薄膜强度、结构和亲水性能的影响 总被引:3,自引:0,他引:3
应用sol-gel法制备了TiO_2薄膜,在321 K和高湿度下应用500 W高压汞灯对薄 膜进行辐射处理,应用划痕法测定了薄膜的强度。利用红外光谱(IR)、拉曼光谱 (Raman)和接触角仪研究了光辐射对薄膜和结构和亲水性能的影响,结果表明高 湿度下紫外光辐射可以促使刚制备TiO_2薄膜中的羟基、有机基团脱落和Ti-O-Ti结 构生成,使TiO_2薄膜的强度、晶化程度显著提高和薄膜在可见光区域吸收增加。 刚制备的sol-gel TiO_2薄膜的亲水性能随着光辐射先是下降,然后上升,且各向 亲水同性。通过此方法可以在不耐温的基材上制备致密的高强度的和具有一定光致 亲水性能的初步晶化的TiO_2薄膜。 相似文献