Steady State and Time Resolved Spectroscopic Study of CdSe and CdSe/ZnS QDs:FRET Approach

This article highlights some physical studies on the relaxation dynamics and Förster resonance energy transfer (FRET) of semiconductor quantum dots (QDs) to proximal dye molecule and the way these phenomena change with core to core-shell QD is discussed. Efforts to understand the optical and carrier relaxation dynamics of CdSe and CdSe/ZnS QDs are made by using absorption, steady-state fluorescence and time-resolved fluorescence (TCSPC) techniques. Steady-state as well as time-resolved fluorescence measurements were employed to evaluate the QD PL quenching induced by the proximal Rhodamine 101 dye molecule and to examine the influence of deep trap states on energy transfer efficiency. The FRET parameters such as spectral overlap, Förster distance, intermolecular distance for each donor-acceptor pair are determined and variation of these parameters from core to core-shell QD is discussed.     

用稳态和时间分辨荧光光谱研究乙醇-水分子团簇的可能类型

研究了紫外光照射乙醇－水混合溶液的稳态和时间分辨荧光光谱.通过检测其荧光光谱和激发光谱,得到了稳态发射光谱的三个荧光峰,峰值分别位于290 nm、305 nm、330 nm,相应的最佳激励光分别为265 nm, 280 nm 和236 nm.在荧光光谱峰值波长处分别监测其荧光强度随时间的衰变过程,将获得的荧光衰减动力学曲线采用指数拟合并进行解卷积处理获得不同荧光光子的寿命值.乙醇－水溶液稳态光谱的特点和三个不同的荧光寿命都表明了溶液中含有三个不同的生色团,分析认为乙醇和水分子间通过氢键作用形成了不同结构的团簇分子.     

Steady state and time-resolved spectroscopic investigations on the photoreactions involved within the electronically excited electron acceptor 9-cyanoanthracene in presence of benzotriazole and benzimidazole donors

The electrochemical, “steady-state” and “time-resolved” spectroscopic investigations were made on the well-known electron acceptor 9-cyanoanthracene (CNA) when interacted with the electron donors benzotriazole (BZT) and benzimidazole (BMI) molecules. Though electrochemical measurements indicate the thermodynamical possibility of occurrences of photoinduced electron transfer reactions within these reacting systems in the lowest excited singlet state (S₁) of the acceptor CNA but the steady-state and time-resolved measurements clearly demonstrate only the triplet-initiated charge separation reactions. It was reported earlier that in the cases of disubstituted indole molecules the occurrences of photoinduced electron transfer reactions were apparent both in the excited singlet and triplet states of the acceptor 9-cyanoanthracene, but the similarly structured present donor molecules benzotriazole (and benzimidazole) behave differently from indoles. The weak ground state complex formations within the presently studied reacting systems appear to be responsible for the observed static quenching phenomena as evidenced from the time-resolved fluorescence studies. Time-resolved spectroscopic investigations demonstrate the formation of the ground state of the reacting components (donor and acceptor) through recombination of triplet ion-pairs via formations of contact neutral radical produced by H-abstraction mechanism.     

稳态平板法测导热系数精度的研究

从稳态平板法测导热系数的原理出发,通过对推导过程的近似处理进行有效的修正,得到更为准确的导热系数表达式,并且对数据处理进行了讨论,显示了利用origin软件的数值拟合功能,能够有效的提高散热速率的测量,从而提高了导热系数结果的精度。     

环丙沙星、氧氟沙星同时与牛血清白蛋白分子作用的荧光光谱

在pH=7.40的水溶液中,环丙沙星(CPFX)、氧氟沙星(OFLX)能够猝灭牛血清白蛋白(BSA)的荧光。当两种药物共存时BSA荧光被进一步猝灭。据此建立了利用荧光发光光谱法进行喹诺酮类药物CPFX与OFLX间相互作用的研究。结果表明:药物间存在相互作用,使药物与蛋白间的结合常数减小、结合稳定性下降,游离型药物含量增加,造成药效增强;药物对蛋白荧光的猝灭属于静态猝灭,药物与蛋白结合位点数约为1。根据Frster非辐射能量转移理论,确定了药物与蛋白之间的结合距离r7nm,属于非辐射能量转移。药物间的相互作用使r值增加,结合距离增大。同步荧光光谱研究表明药物间的相互作用对蛋白构象产生影响,使蛋白质分子伸展,疏水性降低。     

Steady State and Time Resolved Fluorescence Quenching and Chemical Modification Studies of a Lectin from Endophytic Fungus <Emphasis Type="Italic">Fusarium solani</Emphasis>

The solute quenching studies of a lectin from endophytic fungus Fusarium solani were carried out using different quenchers such as acrylamide, succinimide, potassium iodide and cesium chloride. The lectin showed emission maximum at 348 nm indicating relative exposure of tryptophan. The quenchable fraction of the fluorophore was 100% with acrylamide, whereas it was only 50% with succinimide. The ionic quenchers iodide and cesium showed opposite effects at different pH. In the case of cesium, raising the pH resulted in increased quenching and accessibility of typtophan residue, while the iodide showed just opposite effect. These studies showed that the single tryptophan residue of the lectin (per monomer) is relatively exposed, and might be in the vicinity of positively charged amino acid residues. Various amino acids of the F. solani lectin were modified using different reagents to obtain information about the hemagglutinating site. The chemical modification studies suggested tyrosine residues can be modified using N-acetylimidazole, which results in complete loss of hemagglutination activity of the lectin. Kinetics of chemical modification suggested involvement of only 2 tyrosine residues. Modification of arginine, cysteine, histidine, lysine, aspartate, glutamate and tryptophan did not result in loss of hemagglutinating activity of the lectin.     

FTIR光谱方法对比分析少年和老年软骨成分含量

利用傅里叶变换红外(FTIR)光谱方法测量了少年和老年人软骨的红外光谱。由OMNIC 5.2软件计算了软骨中主要有机成分(胶原)和无机成分相关光谱带的积分面积。对代表有机物和无机物的某些谱带面积大小进行了比较。结果表明：软骨中有机成分(酰氨Ⅰ)含量与无机成分(PO3-₄)含量之比少年是老年人的5～7倍;然而脂类含量却有很大的不同, 对脂类(1 747 cm-1)与无机物(PO3-₄)的谱带积分面积进行比较,老年人软骨中脂类含量明显高于少年。作者认为人体随着年龄的增加,全身性的退化在软骨中的总体表现为有机成分(胶原)的减少(而脂类含量却增加)和无机成分(磷酸盐、碳酸盐等)相对的增加,使得软骨骨质变脆,失去过多弹性,耐磨性减低,是进一步容易导致骨病和骨伤的原因。     

Lack of Habituation in Migraine Patients Based on High-Density EEG Analysis Using the Steady State of Visual Evoked Potential

Migraine is a periodic disorder in which a patient experiences changes in the morphological and functional brain, leading to the abnormal processing of repeated external stimuli in the inter-ictal phase, known as the habituation deficit. This is a significant feature clinically of migraine in both two types with aura or without aura and plays an essential role in studying pathophysiological differences between these two groups. Several studies indicated that the reason for migraine aura is cortical spreading depression (CSD) but did not clarify its impact on migraine without aura and lack of habituation. In this study, 22 migraine patients (MWA, N = 13), (MWoA, N = 9), and healthy controls (HC, N = 19) were the participants. Participants were exposed to the steady state of visual evoked potentials also known as (SSVEP), which are the signals for a natural response to the visual motivation at four Hz or six Hz for 2 s followed by the inter-stimulus interval that varies between 1 and 1.5 s. The order of the temporal frequencies was randomized, and each temporal frequency was shown 100 times. We recorded from 128 customized electrode locations using high-density electroencephalography (HD-EEG) and measured amplitude and habituation for the N1–P1 and P1–N2 from the first to the sixth blocks of 100 sweep features in patients and healthy controls. Using the entropy, a decrease in amplitude and SSVEP N1-P1 habituation between the first and the sixth block appeared in both MWA and MWoA (p = 0.0001, Slope = −0.4643), (p = 0.065, Slope = 0.1483), respectively, compared to HC. For SSVEP P1–N2 between the first and sixth block, it is varied in both MWA (p = 0.0029, Slope = −0.3597) and MWoA (p = 0.027, Slope = 0.2010) compared to HC. Therefore, migraine patients appear amplitude decrease and habituation deficit but with different rates between MWA, and MWoA compared to HCs. Our findings suggest this disparity between MWoA and MWA in the lack of habituation and amplitude decrease in the inter-ictal phase has a close relationship with CSD. In light of the fact that CSD manifests during the inter-ictal phase of migraine with aura, which is when migraine seizures are most likely to occur, multiple researchers have lately reached this conclusion. This investigation led us to the conclusion that CSD during the inter-ictal phase and migraine without aura are associated. In other words, even if previous research has not demonstrated it, CSD is the main contributor to both types of migraine (those with and without aura).     

用时延估计法提高光纤光栅中心波长检测精度

提出将雷达、声呐领域中的时延估计算法用于均匀应变场或温度场中任意形状的光栅反射谱中心波长的检测.分析了信噪比(SNR)对不同形状反射谱进行峰值提取的影响.分析结果表明,对均匀周期的单模光纤布拉格光栅,其长度越长,折射率变化越大,峰值检测受信噪比影响也越严重;实验结果表明,与常规算法相比,采用时延估计中的相位谱法进行中心波长偏移量的提取,估计精度不受波长扫描精度的限制,对噪声造成的中心波长随机漂移有很好的抑制作用,而且无需对反射谱的形状进行假设与曲线拟合,计算量小,检测精度可达到皮米量级.     

Advances in the Investigations of Wear and Lubrication by the Aid of Radioactive Tracer Techniques

For investigations in the field of friction, lubrications, and wear radioactive tracer technique is a very important aid. Some examples of wear tests on the system electrobrush-rotor show the possibilities for the detection of the present principal mechanisms: abrasive, adhesive, corrosive, or fatigue wear. In the experiments the rotors and/or the brushes are radioactive labelled by neutron irradiation. The experiments are performed in an apparatus for collection of the wear debris by sucking it into filter cartridges or in an equipment of the pin-disk type supplied for evacuation.     

Some Electric and Spectroscopic Properties of the Radiofrequency Plasma in a Steady Magnetic Field

In the experiences carried out on the capacitively excited high-frequency helium discharges at pressures of 10^?3?10^?2 Torr, a spectral line intensities redistribution in helium spectrum in function of applied steady magnetic field magnitude has been observed. The magnetic field application modifies also the plasma dispersive properties, which are reflected in the variable relative weight of the h.f. field harmonics. The experiences evidenced an electron temperature dependence on the relative h.f. harmonics intensities, confirming the previous researche conclusion concerning the electron temperature increase with the electric field frequency.     

采用光谱技术研究[C4mim][BF4]的传压和测压性能

金刚石压腔是一种在实验室被频繁使用的高压产生装置,它在高压领域占据着重要地位。当金刚石压腔内传压介质只能提供非静水压环境时,利用传统的红宝石荧光光谱测压方法将很难准确测量样品压强,这也是目前超高压实验面临的普遍困难。若有一种兼具“传压”和“测压”双重功能的物质,根据“相邻位置、相近压强”原则,将能够解决在非静水压环境中测不准样品压强问题。显然,探寻兼具“传压”和“测压”双重功能的物质是一项非常重要的工作。本文将红宝石微粒与离子液体[C₄mim][BF₄]装入金刚石压腔,然后利用金刚石压腔压缩[C₄mim][BF₄]使其提供高压环境,同时采集红宝石的荧光光谱及其附近[C₄mim][BF₄]的拉曼光谱。通过分析红宝石特征荧光峰R₁的峰位,得到了[C₄mim][BF₄]在加压过程中提供的一系列高压环境的压强值。通过分析红宝石特征荧光峰R₁的峰宽,发现[C₄mim][BF₄]在0~6.26和6.26~21.43 GPa两个压强范围内可分别提供静水压环境和准静水压环境,表明[C₄mim][BF₄]在0~21.43 GPa范围内可以作为传压介质使用。此外,还发现[C₄mim][BF₄]在0~2.28,2.28~6.26,6.26~14.39和14.39~21.43 GPa四个压强范围内分别为“液相Ⅰ”、“液相Ⅱ”、“非晶相Ⅰ”和“非晶相Ⅱ”。通过分析[C₄mim][BF₄]中特征拉曼峰ν_(B-F)和ν_(ring)的峰位,发现在[C₄mim][BF₄]四个相态内ν_(B-F)和ν_(ring)的峰位随压强增加均满足线性变化关系,并给出了相应的压强与峰位关系函数,这些函数是[C₄mim][BF₄]用作压标物质的重要依据。综上所述,[C₄mim][BF₄]不仅具有“传压”功能,同时还具有“测压”功能,可同时用作“传压介质”和“压标物质”。研究结果为在非静水压环境中准确测量样品压强提供了重要依据,也为超高压条件下样品压强测量不准确问题提供了新的解决思路。     

Study on the Interaction of an Anthracycline Disaccharide with DNA by Spectroscopic Techniques and Molecular Modeling

This study was designed to examine the interaction of 4'-O-(a-L-Cladinosyl) daunorubicin (DNR-D5), a disaccharide anthracycline with calf thymus deoxyribonucleic acid (ctDNA) by UV/Vis in combination with fluorescence spectroscopy and molecular modeling techniques under physiological conditions (Britton-Robinson buffer solutions, pH?=?7.4). By the analysis of UV/Vis spectrum, it was observed that upon binding to ctDNA the anthraquinone chromophore of DNR-D5 could slide into the base pairs. Moreover, the large binding constant indicated DNR-D5 had a high affinity with ctDNA. At the same time, fluorescence spectra suggested that the quenching mechanism of the interaction of DNR-D5 to ctDNA was a static quenching type. The binding constants between DNR-D5 and ctDNA were calculated based on fluorescence quenching data at different temperatures. The negative ?G implied that the binding process was spontaneous, and negative ?H and negative ΔS suggested that hydrogen bonding force most likely played a major role in the binding of DNR-D5 to ctDNA. Moreover, the results obtained from molecular docking corroborate the experimental results obtained from spectroscopic investigations.     

基于LIBS及时间分辨特征峰的激光除漆机理研究

激光除漆是一种高效、清洁的新型清洗技术,对激光除漆物理过程和机理的研究是该技术发展的关键。基于LIBS技术,测量得到油漆去除过程中等离子体的发光光谱,计算出油漆样品去除前后等离子体的电子密度和温度,研究了油漆中特征元素对应的光谱特征峰强度随时间的变化情况。结果表明,随着激光作用脉冲数量的增加,油漆去除深度逐渐增加,等离子体电子密度和温度在将漆去除干净的最后几个脉冲作用时呈下降趋势。油漆中Ti元素的所对应的特征峰信号持续时间为2个μs,油漆去除前后信号强度呈现跳跃减少,该现象可用于快速、准确、实时的判断油漆去除情况。     

光谱法研究Cu2+诱导的不同时间的LDL体外氧化

氧化低密度脂蛋白(oxidized low density lipoprotein,oxLDI)被认为是动脉硬化的关键致病因素.文章综合运用紫外吸收光谱、荧光光谱、同步荧光光谱及圆二色(circular diclaro‘lsm.CD)光谱研究了(好'诱导不同时间的U)IJ体外氧化过程.随着氧化时间的增加.生成的丙二醛(malonaldehyde,MDA)的量逐渐增加,其相对应的430 nm 处的荧光强度也随之加强,氧化过程中生成了新的氧化产物.氧化低密度脂蛋白紫外吸收增强;表征氨基酸残基信息的特征荧光强度和同步荧光强度降低;载脂蛋白B-100(apolipoproteinB-100,apoB-100)α-螺旋含量减少.实验结果表明,LDL氧化过程中Cu2+不仅诱导了氧化产物的生成,而且改变了apoB-100的构象进而导致了生色基团的微环境的变化.     

光谱及等温滴定量热法探究盐酸阿霉素与DNA作用机理

利用荧光光谱法,紫外可见光谱法,红外光谱法,圆二色谱法和等温滴定量热法等手段,对抗癌药物盐酸阿霉素 (DOX) 与DNA的作用过程进行研究,测得了它们的结合常数K_a、结合位点数n、反应焓变ΔH、熵变ΔS及ΔG,且在结合过程中,B型DNA的螺旋结构在一定程度发生改变。荧光光谱的数据显示出显著的猝灭效应, 表明DNA是一个DOX荧光的很好的猝灭剂。红外光谱表明阳离子DOX+通过静电吸引与 DNA 的磷酸基团相互作用,且DOX的碳氢链通过疏水缔合与DNA作用。ITC测定了DOX和DNA相互作用的焓变和熵变,表明DOX的烃链和DNA的碱基之间的疏水性相互作用提供了结合的驱动力。     

基于平行因子分析的激光诱导纳秒时间分辨荧光猝灭法原位研究芘和菲与腐植酸相互作用

基于平行因子(PARAFAC)分析的激光诱导纳秒时间分辨荧光(LITRF)猝灭法原位研究典型多环芳烃(PAHs)芘(Pyr)和菲(Phe)单独及混合状态下与Aldrich腐植酸(HA)相互作用。实验表明,在266 nm激发波长下,Pyr,Phe及HA三者的LITRF光谱相互重叠,无法直接同时测定混合组分中游离Pyr和Phe荧光强度。利用PARAFAC分析可快速有效消除HA荧光干扰,获取混合溶液LITRF光谱中Pyr和Phe荧光强度及各自荧光衰减曲线,并以Freundlich吸附等温模型描述PAHs与HA结合特性。结果验证了Pyr和Phe与HA以非线性形式结合(n<1);Pyr和Phe共存时,两者与HA结合存在竞争关系。加入竞争吸附质后,Pyr和Phe与HA的吸附等温线非线性程度减弱(n趋近于1),单点结合系数下降,且竞争强度随竞争吸附质浓度增加而增强。此外,LITFR-PARAFAC猝灭法与传统荧光猝灭法所得单组分Pyr和Phe与HA结合特性无显著差异。猝灭速率常数及荧光寿命分析反映出Pyr和Phe与HA间荧光以静态猝灭形式为主。LITFR-PARAFAC猝灭法可快速原位研究混合PAHs与HA相互作用,有利于原位预测和评估PAHs的环境行为及其生态风险。     

Time- and Spatially Resolved Spectroscopy of the Plasma State Prior to and during Anode-Spot Formation in High-Current Vacuum Arcs

The emission of numerous lines was measured from a vacuum arc between an Al cathode and Cu anode in which the diffuse, anode-spot, and intense arc modes are observed during a single pulse. An increase in Cu emission and a decrease in Al emission are observed at the transition to the anode-spot mode, and increases in both Al and Cu emission are observed at the transition to the intense-arc mode. Spatial profiles of the excited-state density and Boltzmann-distribution temperatures could be obtained at several positions in the gap. The results show not only a clear correspondence between arc voltage and the arc appearance during different arc modes, but also distinctly different spectral emission properties and droplet behavior.     

利用Far-IR和THz-TDS光谱法测定大米中西维因

利用太赫兹时域光谱（THz-TDS）和傅里叶变换远红外光谱（FT-Far-IR）技术研究了大米中西维因在太赫兹频段的吸收光谱特征,并结合化学计量学方法对大米中西维因进行了测定。样品的制备采取待测农药西维因与大米粉末混合压片的方法模拟真实检测情景,无需样品的分离富集。分别将样品在1.8～6.3 THz特征波段内的Far-IR吸收光谱数据和在0.5～1.5 THz特征波段内的THz-TDS吸收光谱数据随机划分为训练集和验证集。采用偏最小二乘回归（PLSR）方法建立定量分析模型,将校正均方根误差（RMSECV）、预测均方根误差（RMSEP）、预测相关系数（R_v）作为模型性能评判的依据,RMSECV,RMSEP越小,R_v越大,则所建立的模型越好。两种检测技术均得到较好的结果。其中,运用Far-IR技术所得数据建立的定量分析模型预测相关系数(R_v)为0.99,校正均方根误差（RMSECV）为0.007 7, 预测均方根误差（RMSEP）为0.008 6; 运用THz-TDS技术所得数据建立的定量分析模型预测相关系数为0.98,校正均方根误差（RMSECV）为0.002 5、预测均方根误差（RMSEP）为0.004 4。该研究为定量检测粮食中的农残提供了一种新方法。