两类以芴为中心的有机分子双光子吸收特性

在密度泛函理论水平上, 利用响应函数方法研究了实验新合成的两类以芴为π中心的分子(SK-G1和NT-G1)的双光子吸收特性. 计算结果表明, 这两类有机分子都具有较大的单光子和双光子光吸收强度. 在低能量范围内, NT-G1分子的最大单光子吸收峰相对于SK-G1分子来说发生了红移, 且其最大单光子吸收强度是SK-G1分子的两倍. SK-G1和NT-G1分子的最大双光子吸收均发生在第二激发态. NT-G1分子的最大双光子吸收截面约是SK-G1分子的五倍, 并且NT-G1分子存在一个较宽的双光子吸收带. NT-G1分子的较强光学性质与分子内较大的电荷转移过程有关. 采用Onsager模型计算了溶剂分子对溶质分子单光子吸收性质的影响, 理论计算结果和实验测量结果符合得较好.     

Absorption and emission spectroscopic characterisation of combined wildtype LOV1-LOV2 domain of phot from Chlamydomonas reinhardtii

An absorption and emission spectroscopic characterisation of the combined wild-type LOV1-LOV2 domain string (abbreviated LOV1/2) of phot from the green alga Chlamydomonas reinhardtii is carried out at pH 8. A LOV1/2-MBP fusion protein (MBP=maltose binding protein) and LOV1/2 with a His-tag at the C-terminus (LOV1/2-His) expressed in an Escherichia coli strain are investigated. Blue-light photo-excitation generates a non-fluorescent intermediate photoproduct (flavin-C(4a)-cysteinyl adduct with absorption peak at 390 nm). The photo-cycle dynamics is studied by dark-state absorption and fluorescence measurement, by following the temporal absorption and emission changes under blue and violet light exposure, and by measuring the temporal absorption and fluorescence recovery after light exposure. The fluorescence quantum yield, phi(F), of the dark adapted samples is phi(F)(LOV1/2-His) approximately 0.15 and phi(F)(LOV1/2-MBP) approximately 0.17. A bi-exponential absorption recovery after light exposure with a fast (in the several 10-s range) and a slow component (in the near 10-min range) are resolved. The quantum yield of photo-adduct formation, phi(Ad), is extracted from excitation intensity dependent absorption measurements. It decreases somewhat with rising excitation intensity. The behaviour of the combined wildtype LOV1-LOV2 double domains is compared with the behaviour of the separate LOV1 and LOV2 domains.     

Electron and hole injection in PbSe quantum dot films

Electrochemical methods are used to inject charge into films of colloidal semiconductor nanocrystals of PbSe. The injection of electrons and holes into quantum confined states is confirmed by monitoring changes in the IR absorption spectrum. Holes are injected into the 1Sh state, causing a bleach of the 1Sh-1Se and 1Sh-1Pe interband transitions and inducing a 1Sh-1Ph intraband absorption. Electrons can be sequentially injected into the 1Se and 1Pe states, first bleaching the 1Sh-1Se and 1Ph-1Se interband transitions and inducing a 1Se-1Pe intraband absorption, and then bleaching the 1Sh-1Pe transition and inducing a 1Pe-1De intraband absorption.     

Further observations in atomic absorption spectroscopy

Three observations have been made pertinent to atomic absorption spectroscopy. With a flame atomizer, it is shown that (1) the absorption profile is controlled by metal oxide formation, (2) organo-metallic compounds give rise to greater absorption than metal salts, and (3) absorption by hydroxyl bands affects the apparent metal absorption in certain spectral regions.     

Surface plasmon enhancement of two- and three-photon absorption of Hoechst 33 258 dye in activated gold colloid solution

Herein we present experimental evidence of the strong surface plasmon enhancement of two- and three-photon absorption of Hoechst 33 258 (2'-(4-hydrophenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bis(1H-benzimidazole)) pentahydrate in an aqueous solution containing activated gold colloid. The 480-fold enhancement in two-photon absorption and 30-fold in three-photon absorption are predominantly attributed to the electric-field enhancement via surface plasmon resonance. The greater enhancement observed in two-photon absorption is due to the characteristic two- and three-photon absorption cross-sections of the dye.     

炸药爆轰合成纳米石墨的红外光谱研究

石墨是碳材料中最常见的结晶状态,它具有耐高温、抗腐蚀、自润滑、无毒及价格低廉等特点,广泛应用于润滑剂和添加剂等方面^[1].由于高纯纳米石墨粉在某些高新技术领域中有较好的应用前景,近些年来得到开发和应用,如制成复合导电材料、吸波材料及储氢材料等^[2].以前有学者用纳米金刚石粉加热相转变^[3]和高能球磨^[4,5]的方法制备了纳米石墨,在制备碳纳米管时也有石墨的纳米粒子生成^[6].但用这几种方法制备纳米石墨,既费时又消耗较大能量,成本非常高.     

矿物药金礞石的红外光谱分析

采用傅立叶红外光谱法分析了金礞石试样,对所得图谱进行解析,发现试样的红外光谱具备层状硅酸盐矿物的吸收特征.其吸收带主要分为4个区域:3 700～3 000 cm-1区间的OH伸缩振动吸收,1 620 cm-1左右处的H2O弯曲振动吸收,1 000 cm-1左右处的Si-O伸缩振动吸收和550～400 cm-1区间的Si...     

双功能离子液体的合成及二氧化碳捕集性能

采用两步法合成了新型功能化离子液体1-甲氧基乙基-3-甲基咪唑甘氨酸([C_3O_1mim][Gly]),并研究了其对CO_2的吸收性能.利用核磁共振、红外光谱及热重分析等手段进行表征,验证了该离子液体的结构,且发现其具有较高的热稳定性.对比单乙醇胺(MEA),考察了[C_3O_1mim][Gly]在不同温度下对CO_2的捕集能力,结果表明,[C_3O_1mim][Gly]在40℃下的吸收容量可达1.26 mol CO_2/mol IL,远高于MEA,这表明[C_3O_1mim][Gly]对CO_2具有良好的吸收能力,吸收容量随着温度升高而降低.该离子液体同时具有良好的循环稳定性,进行5次吸收解吸操作后仍可保持较高的CO_2吸收量.对该离子液体吸收CO_2进行了动力学研究,结果表明,Pseudo-second-order模型能够较好地描述该吸收过程.     

Ab initio potential energy surfaces, total absorption cross sections, and product quantum state distributions for the low-lying electronic states of N(2)O

Adiabatic potential energy surfaces for the six lowest singlet electronic states of N(2)O (X (1)A('), 2 (1)A('), 3 (1)A('), 1 (1)A("), 2 (1)A(") and 3 (1)A(")) have been computed using an ab initio multireference configuration interaction (MRCI) method and a large orbital basis set (aug-cc-pVQZ). The potential energy surfaces display several symmetry related and some nonsymmetry related conical intersections. Total photodissociation cross sections and product rotational state distributions have been calculated for the first ultraviolet absorption band of the system using the adiabatic ab initio potential energy and transition dipole moment surfaces corresponding to the lowest three excited electronic states. In the Franck-Condon region the potential energy curves corresponding to these three states lie very close in energy and they all contribute to the absorption cross section in the first ultraviolet band. The total angular momentum is treated correctly in both the initial and final states. The total photodissociation spectra and product rotational distributions are determined for N(2)O initially in its ground vibrational state (0,0,0) and in the vibrationally excited (0,1,0) (bending) state. The resulting total absorption spectra are in good quantitative agreement with the experimental results over the region of the first ultraviolet absorption band, from 150 to 220 nm. All of the lowest three electronically excited states [(1)Sigma(-)(1 (1)A(")), (1)Delta(2 (1)A(')), and (1)Delta(2 (1)A("))] have zero transition dipole moments from the ground state [(1)Sigma(+)(1 (1)A('))] in its equilibrium linear configuration. The absorption becomes possible only through the bending motion of the molecule. The (1)Delta(2 (1)A('))<--X (1)Sigma(+)((1)A(')) absorption dominates the absorption cross section with absorption to the other two electronic states contributing to the shape and diffuse structure of the band. It is suggested that absorption to the bound (1)Delta(2 (1)A(")) state makes an important contribution to the experimentally observed diffuse structure in the first ultraviolet absorption band. The predicted product rotational quantum state distribution at 203 nm agrees well with experimental observations.     

利血平与玫瑰精B的高灵敏显色反应及分析应用

研究了利血平与玫瑰精B的显色反应,建立了测定利血平的高灵敏分光光度法。在酸性条件下,利血平的水解产物和玫瑰精B形成具有正、负吸收峰的红色离子缔合物,最大正吸收波长位于490 nm,最大负吸收波长位于520 nm,表观摩尔吸光系数(ε)分别为1.20×105L.mol-1.cm-1(正吸收)和1.83×105L.mol-1.cm-1(负吸收),利血平在0～5.0μg/mL范围内遵从比尔定律。若采用正、负峰叠加测定,灵敏度可达3.00×105L.mol-1.cm-1。探讨了适宜的反应条件、主要分析特性及方法的精密度和可靠性。该法可用于市售利血平注射液中利血平含量的测定。     

Formation and reactivity of free radicals in 5-hydroxymethyl-2-furaldehyde--the effect on isoprenaline photostability

Solutions of glucose are used as diluents for drugs in various drug infusions. When sterilized by heat small amounts of the substance 5-hydroxymethyl-2-furaldehyde (5-HMF) is produced from glucose. At a hospital ward such infusions may be exposed to irradiation; including UV-light. The photoreactivity of the furaldehyde is investigated. It is shown to photodestabilize the catecholamine isoprenaline. It is shown to be a producer, but also a consumer, of singlet oxygen. The excited triplet, cation and anion radical have been produced by pulse radiolysis and flash photolysis and their absorbance characteristics have been determined. The triplet absorption spectrum showed absorption bands at 320 and 430 nm with molar absorption coefficients of 4700 and 2600 M-1 cm-1, respectively. The anion radical showed absorption bands at 330 and 420 nm with molar absorption coefficients of 2000 and 300 M-1 cm-1, respectively. The cation radical had an absorption band at 320 nm with a molar absorption coefficient of 5000 M-1 cm-1. The quantum yield for the production of singlet oxygen, sensitized by the 5-HMF triplet, was determined to be 0.6, whilst the quantum yield for the triplet formation was 1.0. Aqueous solutions of 5-HMF were found to photoionize to yield the hydrated electron and the cation radical of 5-HMF in a biphotonic process. The influences of pH, buffer and glucose on the formation of transients were evaluated. The reactions between 5-HMF and the solvated electron, the hydroxyl radical and the superoxide were also studied.     

中空纤维致密膜基吸收CO2传质过程

研究了硅橡胶/聚砜中空纤维致密膜基吸收CO2的传质机理,考察了吸收剂种类(NaOH,MEA,DEA和TEA)、NaOH浓度、吸收剂流速、吸收剂压力和气相压力对CO2传质通量及传质速率的影响.其中,用2×103mol/m3NaOH作吸收剂时,聚合物膜传质为控制步骤,其传质效率与膜自然渗透相近.     

Theoretical study of the absorption and nonradiative deactivation of 1-nitronaphthalene in the low-lying singlet and triplet excited states including methanol and ethanol solvent effects

The photophysics of the 1-nitronaphthalene molecular system, after the absorption transition to the first singlet excited state, is theoretically studied for investigating the ultrafast multiplicity change to the triplet manifold. The consecutive transient absorption spectra experimentally observed in this molecular system are also studied. To identify the electronic states involved in the nonradiative decay, the minimum energy path of the first singlet excited state is obtained using the complete active space self-consistent field∕∕configurational second-order perturbation approach. A near degeneracy region was found between the first singlet and the second triplet excited states with large spin-orbit coupling between them. The intersystem crossing rate was also evaluated. To support the proposed deactivation model the transient absorption spectra observed in the experiments were also considered. For this, computer simulations using sequential quantum mechanic-molecular mechanic methodology was used to consider the solvent effect in the ground and excited states for proper comparison with the experimental results. The absorption transitions from the second triplet excited state in the relaxed geometry permit to describe the transient absorption band experimentally observed around 200 fs after the absorption transition. This indicates that the T(2) electronic state is populated through the intersystem crossing presented here. The two transient absorption bands experimentally observed between 2 and 45 ps after the absorption transition are described here as the T(1)→T(3) and T(1)→T(5) transitions, supporting that the intermediate triplet state (T(2)) decays by internal conversion to T(1).     

萘基衍生物的光敏化瞬态吸收光谱

本文利用激光闪光光解技术对二苯甲酮光敏化一系列萘基烷烃衍生物的三重态—三重态吸光光谱及他们之间的三重态能量传递进行了研究. 计算了三重态能量传递速度常数和传递效率, 二苯甲酮在不同体系中的三重态寿命, 探讨了分子结构对光敏化能量传递的影响.     

射流冷却的OCS分子高分辨VUV吸收光谱研究

The absorption spectrum of OCS molecules under jet-cooled conditions has been measured between 64150 and 65840 cm-1 with a highly resolved tunable vacuum ultraviolet (VUV) laser (about 0.2 cm-1), generated by two-photon resonant four wave mixing process. During the experiment, the VUV intensities prior and posterior to the OCS absorption were monitored simultaneously in order to increase the sensitivity of absorption measurement, and the absorption sensitivity △I/I was determined to be 1%. The measured spectrum is essentially similar to the S(1S) photofragment excitation spectrum under similar conditions, indicating that the dissociation to produce S(1S) fragment is the main pathway. The difference between these kinds of spectra, however, implies the existence of other dissociation channels in addition to the S(1S) pathway.     

LaNi5合金的吸氢动力学

研究了LaNi_5-H体系的吸氢反应动力学。在吸放氢可逆反应同时考虑的情况下, 求得了速度方程的解析解。在α相区20—50 ℃的温度范围内, 吸氢速度常数k_α为0.08—0.41 s~(-1); 脱氢速度常数k_d为4.8—25 MPa·s~(-1)。吸氢反应的表观活化能E_α为35 kJ(mol H_2)~(-1)。在α+β相区的吸氢较α相区慢得多。起始阶段吸氢速度对氢压为一级, 反应受氢化物表面上氢分子解离控制。随着吸氢反应深度的增大, 吸氢速度变为固相中的界面反应控制。速度常数受温度的影响很小。α+β相区的压力平台前半段和后半段有着不同的吸氢速度。     

Synthesis, structural characterization, photophysics, and broadband nonlinear absorption of a platinum(II) complex with the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9 H-fluoren-2-yl)-2,2'-bipyridinyl ligand

A platinum complex with the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridinyl ligand (1) was synthesized and the crystal structure was determined. UV/Vis absorption, emission, and transient difference absorption of 1 were systematically investigated. DFT calculations were carried out on 1 to characterize the electronic ground state and aid in the understanding of the nature of low-lying excited electronic states. Complex 1 exhibits intense structured (1)π-π* absorption at λ(abs)<440?nm, and a broad, moderate (1)MLCT/(1)LLCT transition at 440-520?nm in CH(2)Cl(2) solution. A structured (3)π-π*/(3)MLCT emission at about 590?nm was observed at room temperature and at 77?K. Complex 1 exhibits both singlet and triplet excited-state absorption from 450?nm to 750?nm, which are tentatively attributed to the (1)π-π* and (3)π-π* excited states of the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridine ligand, respectively. Z-scan experiments were conducted by using ns and ps pulses at 532?nm, and ps pulses at a variety of visible and near-IR wavelengths. The experimental data were fitted by a five-level model by using the excited-state parameters obtained from the photophysical study to deduce the effective singlet and triplet excited-state absorption cross sections in the visible spectral region and the effective two-photon absorption cross sections in the near-IR region. Our results demonstrate that 1 possesses large ratios of excited-state absorption cross sections relative to that of the ground-state in the visible spectral region; this results in a remarkable degree of reverse saturable absorption from 1 in CH(2)Cl(2) solution illuminated by ns laser pulses at 532?nm. The two-photon absorption cross sections in the near-IR region for 1 are among the largest values reported for platinum complexes. Therefore, 1 is an excellent, broadband, nonlinear absorbing material that exhibits strong reverse saturable absorption in the visible spectral region and large two-photon-assisted excited-state absorption in the near-IR region.     

Neocuproine-extended porphyrin coordination complexes. 2. Spectroscopic properties of the metalloporphyrin derivatives and investigations into the HOMO ordering

The synthesis of a porphyrin compound, 1, containing a 2,9-dimethyl-1,10-phenanthroline moiety that is fused at the beta-pyrrole positions is reported. The absorption spectra of the free-base, copper(II), and zinc(II) derivatives have been studied. On the basis of absorption band intensities, the HOMO of the free base (H21) and its copper and zinc complexes (Cu1 and Zn1) was determined to be of a1u symmetry. Relative to H21, compounds Cul and Znl show enhanced spectral changes upon external metal ion binding. Although the HOMO is the same in all three compounds, the energy gap between the two highest occupied orbitals is greater for Cu1 and Zn1 than it is for the free-base compound. Several metal ions (Ni2+, Cu+, Cu2+, Zn2+, Li+) were examined in their binding to the phenanthrolinic group by measuring the resulting changes in the absorption spectra. It is shown that the observed changes in the absorption spectra are insensitive to the nature of the metal ion coordinated by the phenanthroline moiety. Significant differences in the absorption and emission spectra between Zn1 and [Zn(Zn1)2]2+ clearly demonstrate that the porphyrin pi-system is strongly affected by the binding of metal ions at the fused phenanthrolinic moiety.     

Optical absorption and fluorescence studies on imidazolium ionic liquids comprising the bis (trifluoromethanesulphonyl)imide anion

Optical absorption and fluorescence behaviour of two rigorously purified imidazolium ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide are studied in the neat condition and in solution. Non-negligible absorption in the UV region with a long tail extending into the visible region is the main feature of the absorption. Excitation wavelength-dependent two-component fluorescence characterizes the emission behaviour of these liquids. That ion association gives rise to the long absorption tail and shifting fluorescence maximum, which appears to be common to most of the imidazolium ionic liquids, is evident from the effect of the conventional solvents     

Measurement of absorption cross sections in the long-wavelength region of the S0S1 absorption band of dyes

In the long-wavelength region of the S₀S₁ absorption band of dyes only a fraction of molecules takes part in the absorption process. The absorption cross section of the molecules involved is deduced from non-linear transmission measurements with picosecond light pulses. The absorption cross sections σ_A(ν_L) (ν_L is the ruby-laser frequency) of 1,1′-diethyl-2,4′-carbocyanine iodide in methanol and oxazine 1 perchlorate in ethanol are determined.