脉冲激光光声量热装置的研制及用之对香豆素激光染料无辐射跃迁过程的研究

本文报道了一套适用于液相体系的高灵敏度脉冲激光光声量热装置的建立。用此仪器对香豆素激光染料C428,C47和C120的无辐射过程进行了研究,测得它们在无水乙醇中的无辐射跃迁量子产额分别为0.50,0.47和0.38。     

F114双通道激光解离的动力学研究

本文用TEA CO_2激光器研究了F_(114)(氟利昂-114)激光解离的通道竞争动力学过程。实验发现, F_(114)的激光解离是C—C链和C—Cl键断裂的双通道竞争过程; 其解离过程可以用Arrhenius公式来描述, 并且激光解离的表观活化能与热解离活化能相近, 因而该解离反应具有明显的热解离行为。理论计算还表明, F_(114)的双通道解离过程基本上符合RRKM理论。     

激光诱导荧光法测量PbS~* A(0~ )态的振动弛豫速率

一、引言分子中电子激发态的猝灭和振动弛豫的研究对于寻找新的可见激光体系,了解电子态间瓦相作用具有相当重要的意义。我们曾经利用化学发光方法测量了C_2~*d~3Π_g和BaO~*A~1Σ态的电子猝灭和振动弛豫,获得了重要的结果。但此法有一定的局限,需要对电子态间无辐射跃迁有清楚的了解,才有可能进行测量和分析。激光诱导荧光方法是近年来研究分子传能的重要手段之一,只要用激光将分子激励到所研究的能级,然后跟踪它的辐射强度随时间的变化(在脉冲激励情况下)或相邻能级布居随压力的变化(在连续激励时),就可获得有关     

F_(114)双通道激光解离的动力学研究

本文用TEA CO_2激光器研究了F_(114)(氟利昂-114)激光解离的通道竞争动力学过程。实验发现,F_(114)的激光解离是C—C链和C—Cl键断裂的双通道竞争过程;其解离过程可以用Arrhenius公式来描述,并且激光解离的表观活化能与热解离活化能相近,因而该解离反应具有明显的热解离行为。理论计算还表明,F_(114)的双通道解离过程基本上符合RRKM理论。     

激光促进乙烯在硫酸镍上表面反应

制备了硫酸镍固体材料.采用红外光谱(IR)、程序升温脱附(TPD)和激光促进表面反应(LSSR)技术,研究了乙烯在NiSO4表面上的化学吸附态和激光促进C2H4表面反应性能.实验结果表明,C2H4以H原子与固体材料表面Lewis碱位(S=O键中的端氧)作用,形成分子吸附态.在常压和100 ℃条件下,用1079 cm－1激光激发吸附有C2H4分子中H的S=O键100次, C2H4转化率可达15％,生成丁二烯的选择性为100％.根据表征和反应结果,讨论了C2H4在NiSO4上的LSSR机理和影响LSSR性能的因素.     

分子动力学模拟飞秒激光对C60光裂解反应机理的影响

基于半经典分子动力学方法模拟超快激光诱导的C60光裂解反应.选择能量为2.0eV,半峰全宽(FWHM)分别为40和500fs的激光作用于C60分子,调节脉冲强度使其发生裂解反应,比较长短脉宽飞秒激光对C60裂解反应机理的影响.通过分析产物分布、原子平衡指数、温度以及吸收能量(包括动能、势能和电子能量),证实飞秒激光脉冲下C60的光裂解主要由电子激发态控制,非热力学效应在该反应中起重要作用.激光场的作用时间和强度均影响光裂解反应过程,而电子吸收能量饱和后光场强度的作用则变得不明显.     

C60-地塞米松的激光激发

利用激光光解装置检测了C60-地塞米松(C60-DE)的苯溶液在355 nm激光照射下产生的激发三重态, 3C60-DE*出现四个吸收峰, 分别位于700、440、350 和310 nm. 在330 nm处观察到了它的漂白吸收最大值, 这与其基态吸收最大值相对应. 3C60-DE*能够将能量转移给O2分子而淬灭. 与3C60*相比, 3C60-DE*的三重态鄄三重态(T-T)淬灭速率常数减小(3C60*为(5.03±1.31)×109 L·mol-1·s-1, 3C60-DE*为(3.53±0.87)×109 L·mol-1·s-1), 而寿命增加了(3C60*为(12.0±2.6) μs, 3C60-DE*为(18.0±3.3) μs), 这可能是C60分子上连接了地塞米松分子后减小了C60球之间碰撞的几率所致.     

腺嘌呤激发态失活通道的动力学模拟

采用半经典动力学方法模拟了1nπ*态9H-腺嘌呤的无辐射失活过程,模拟发现了一条新的失活通道,即N7-C8断键,释放的键能转化为分子动能.C8-H的强烈振动会导致无辐射跃迁,从而使分子返回基态.     

C60富勒醇、C70富勒醇的激光光解研究

在248 nm激光作用下,与通常富勒烯衍生物(如C60(C4H6O),C60(C3H7N),C60[C(COOEt)2]x)在溶液中光解常产生激发三重态不同,富勒烯水溶性衍生物C60(C70)富勒醇[C60(OH)n,C70(OH)m],能被248 nm激光单光子电离.以KI溶液为参照,在室温下(大约15℃)测出其水合电子的量子产额(Φe-)分别为0.08,0.11.通过激光光解与SO4ˉ的氧化,确定了C60富勒醇阳离子自由基或中性自由基的存在并且观察到C70富勒醇阳离子自由基的瞬态吸收峰.     

火焰结构的平面激光诱导荧光技术观测

用平面激光诱导荧光（PLIF）技术测量了烧煤油的酒精喷灯单脉冲激光诱导荧光，由平面荧光图可清晰地看到氢氧基与C2、C3在火焰中的位置，同时，也看到了煤油火焰由发生、发展到熄灭过程中火焰结构的变化；PLIF技术是研究火焰结构的有力工具。     

IMMUNOMODULATING EFFECTS OF THE FUCOIDAN-GALACTOSAN SULFATE (F12) ON MACROPHAGES IN MICE

The immunomodulating effects of F12 on mouse peritoneal macrophages was intended to be studied with different doses of 20, 40, 80 and 120mg/Kg. F12 increased peroxidase activity in dexc dependent mammer from 0.02±0.001 to 0.175±0.038, 0.211±0.041, 0.137±0.045 and 0.078 ±0.036, respectively, increased cytotoxicity from 127.33±22.96 to 162.74±19.53, 237.30±25.15,178. 62±36. 22 and 158. 66 ± 42. 75dpm, respectively, promoted phagocytic activity from 0. 03±0.01 to0.21 ±0.016, 0.43±0.041, 0.40 ±0.032 and 0.30±0.160b. Furthermore, F12 in a concentration of 15, 30,60,120 μ g/ml enhanced IL-1 production from 0.15±0.02 to 0.20 ±0.005b 0.21±0.02,0.22± 0.005,0.24 ±0.002 and 0.22 ±0.02,respectively. Thus F12 can be considered as an effective stimulator of macrophages.     

Electronic states of tetrahydrofuran molecules studied by electron collisions

Electronic states of tetrahydrofuran molecules were studied in the excitation energy range 5.5-10 eV using the technique of electron energy loss spectroscopy in the gas phase. Excitation from the two conformations, C(2) and C(s), of the ground state of the molecule are observed in the measured energy loss spectra. The vertical excitation energies of the (3)(n(o)3s) triplet state from the C(2) and C(s) conformations of the ground state of the molecule are determined to be 6.03 ± 0.02 and 6.25 ± 0.02 eV, respectively. The singlet-triplet energy splitting for the n(o)3s configuration is determined to be 0.31 eV. It is also found that excitation from the C(s) conformation of the ground state has a higher cross section than that from the C(2) conformation.     

Aqueous complexation of thorium(IV), uranium(IV), neptunium(IV), plutonium(III/IV), and cerium(III/IV) with DTPA

Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal.     

Photophysical and redox properties of perylene bis- and tris-dicarboximide fluorophores with triplet state formation: transient absorption and singlet oxygen sensitization

A detailed photophysical characterization of a couple of new perylene imide derivatives, a carboxylic trisimide PIx, and an asymmetrically substituted carboxylic bisimide PIa is presented. PIx and PIa have the lowest singlet excited state just below 2.6 eV. The dyes are remarkably fluorescent (?(f) = 0.37 ± 0.03 for PIa and ?(f) = 0.58 ± 0.04 for PIx in toluene), but they also display an efficient intersystem crossing. This leads to typical excited triplet photophysics/photochemistry, with intense triplet state absorption spectra and efficient singlet oxygen ((1)Δ(g)) photosensitization (?(Δ) = 0.68 ± 0.02 for PIa and 0.44 ± 0.02 for PIx in toluene). On the basis of the measured ?(Δ), a ?(isc) of 0.65 ± 0.02 for PIa and 0.43 ± 0.02 for PIx in toluene is derived. PIx reduces at -0.58 eV vs SCE, almost similarly to the corresponding symmetrically substituted perylene bisimide PI0, but unlike the latter, it has the first oxidation potential above +1.9 V. PIa is more electron rich and displays a more difficult first reduction at -0.95 V with a more facile oxidation at +1.75 V, similar to that of the parent PI0. The absorption spectra of the excited singlet and triplet states and that of electrochemically generated monoanions are reported.     

The photoionisation of propargylene and diazopropyne

The photoionisation of the C(3)H(2) isomer propargylene was studied using synchrotron radiation and coincidence techniques. An adiabatic ionisation energy (IE(ad)) of 8.99 ± 0.02 eV was determined. The precursor diazopropyne was investigated as well. Ionisation and appearance energies were measured.     

Vacuum-deposited small-molecule organic solar cells with high power conversion efficiencies by judicious molecular design and device optimization

Three new tailor-made molecules (DPDCTB, DPDCPB, and DTDCPB) were strategically designed and convergently synthesized as donor materials for small-molecule organic solar cells. These compounds possess a donor-acceptor-acceptor molecular architecture, in which various electron-donating moieties are connected to an electron-withdrawing dicyanovinylene moiety through another electron-accepting 2,1,3-benzothiadiazole block. The molecular structures and crystal packings of DTDCPB and the previously reported DTDCTB were characterized by single-crystal X-ray crystallography. Photophysical and electrochemical properties as well as energy levels of this series of donor molecules were thoroughly investigated, affording clear structure-property relationships. By delicate manipulation of the trade-off between the photovoltage and the photocurrent via molecular structure engineering together with device optimizations, which included fine-tuning the layer thicknesses and the donor:acceptor blended ratio in the bulk heterojunction layer, vacuum-deposited hybrid planar-mixed heterojunction devices utilizing DTDCPB as the donor and C(70) as the acceptor showed the best performance with a power conversion efficiency (PCE) of 6.6 ± 0.2% (the highest PCE of 6.8%), along with an open-circuit voltage (V(oc)) of 0.93 ± 0.02 V, a short-circuit current density (J(sc)) of 13.48 ± 0.27 mA/cm(2), and a fill factor (FF) of 0.53 ± 0.02, under 1 sun (100 mW/cm(2)) AM 1.5G simulated solar illumination.     

C60电化学还原的稳态性质研究

自1990年9月Kratschmer等报导了C_(60)的常量制备和提纯以来,有关C_(60)及其他富勒炭分子(Fullerens)的研究报导与日俱增,成为近三年来最为活跃的研究领域之一.由于C_(60)的特殊结构,在电化学行为上也表现出十分独特的反应性质,如容易实现多电子氧化还原反应,可逆加氢及能形成离子嵌入电极材料等.本工作采用微电极方法研究了C_(60)稳态极化行为,测定了C_(60)的扩散系数和反应电子数,并通过现场紫外可见光谱电化学方     

四氯合镉酸正十一烷铵的合成、晶体结构及低温热容

合成了四氯合镉酸正十一烷铵配合物(C₁₁H₂₃NH₃)₂CdCl₄(s)[简写: C₁₁Cd(s)]. 用X 射线单晶衍射技术、化学分析和元素分析确定其晶体结构和化学组成. 利用其晶体学数据计算出晶格能为: U_POT＝908.18 kJ·mol^-1. 利用精密自动绝热热量计测定了它在78～395 K 温区的低温热容, 结果表明, 该配合物在此温区出现两次连续的固-固相转变, 计算出两次相变的峰温、摩尔焓及摩尔熵分别为: T_trs,1＝(321.88±0.07) K, Δ_trsH_m,1＝(37.59±0.17) kJ·mol^-1, Δ_trsS_m,1＝(117.24±0.12) J·K^-1·mol^-1, T_trs,2＝(323.81±0.30) K, Δ_trsH_m,2＝(12.42±0.02) kJ·mol^-1 和Δ_trsS_m,2＝(38.36±0.09) J·K^-1·mol^-1. 用最小二乘法将实验摩尔热容对温度进行拟合, 得到热容随温度变化的多项式方程. 用此方程进行数值积分,得到此温区每隔5 K 的舒平热容值和相对于298.15 K 时的热力学函数值.     

Electron affinities, well depths, and vibrational spectroscopy of cis- and trans-HOCO

We report vibrationally resolved photoelectron spectra of internally cold HOCO(-) and DOCO(-) anions at wavelengths near and well above the detachment threshold. These spectra are dominated by a strong Franck-Condon progression of three low-energy modes of the cis isomer, the first gas-phase measurement of these vibrations. Using highly resolved, near-threshold spectra we are able to reassign the electron affinities (EAs) of cis- and trans-HOCO to 1.51 ± 0.01 and 1.37 ± 0.01 eV, respectively. Using these EAs, well depths with respect to OH + CO are determined to be 1.07 ± 0.02 eV for trans-HOCO and 0.99 ± 0.02 eV for cis-HOCO. High-level ab initio calculations show excellent agreement with all experimental results. These values will be of direct use in thermochemical calculations and will help to aid in the identification of the HOCO radical in complex reactions.     

Stress degradation studies and development of stability-indicating TLC-densitometry method for determination of prednisolone acetate and chloramphenicol in their individual and combined pharmaceutical formulations

ABSTRACT: A rapid and reproducible stability indicating TLC method was developed for the determination of prednisolone acetate and chloramphenicol in presence of their degraded products. Uniform degradation conditions were maintained by refluxing sixteen reaction mixtures for two hours at 80°C using parallel synthesizer including acidic, alkaline and neutral hydrolysis, oxidation and wet heating degradation. Oxidation at room temperature, photochemical and dry heating degradation studies were also carried out. Separation was done on TLC glass plates, pre-coated with silica gel 60F-254 using chloroform: methanol (14:1 v/v). Spots at Rf 0.21 ± 0.02 and Rf 0.41 ± 0.03 were recognized as chloramphenicol and prednisolone acetate, respectively. Quantitative analysis was done through densitometric measurements at multiwavelength (243 nm, λmax of prednisolone acetate and 278 nm, λmax of chloramphenicol), simultaneously. The developed method was optimized and validated as per ICH guidelines. Method was found linear over the concentration range of 200-6000 ng/spot with the correlation coefficient (r2 ± S.D.) of 0.9976 ± 3.5 and 0.9920 ± 2.5 for prednisolone acetate and chloramphenicol, respectively. The developed TLC method can be applied for routine analysis of prednisolone acetate and chloramphenicol in presence of their degraded products in their individual and combined pharmaceutical formulations.