应用于FAGE技术测量OH自由基的激光器波长修正方法研究

研究了一种应用于气体扩张激光诱导荧光(FAGE)技术测量OH自由基的染料激光器波长修正方法。该方法采用镍铝丝热解水汽产生稳定的高浓度OH自由基,利用重复频率为8500 Hz的染料激光器输出波长约282 nm激光作为光源.激发低压腔内热解产生的高浓度高稳定性OH自由基产生荧光,由普通光电倍增管和光电二极管分别探测激发荧光和出腔激光强度。通过延时信号发生器统一触发激光器和高速数据采集卡并结合LabVIEW软件处理得到单位激光强度的荧光积分强度数据。连续两次扫描激光波长,当第二次扫描的荧光积分强度达到第一次最大值的0.95倍时,停止波长扫描,此时的激光器波长位置即为激发线位置。本文首先扫描激光波长,研究了282 nm激发机制下的OH自由基激发谱;然后在Q_1 2激发线位置探究了气体湿度、氧气含量、进气量以及抽速对荧光积分强度和寿命的影响;并分析了镍铝丝热解水的反应机理,初步认为热解中OH自由基主要来源于氧原子与水的反应。在以上荧光积分强度和寿命影响因素的研究基础上,优化了系统参数,使荧光积分强度波动小于±1.9%。连续多次进行波长修正,修正偏差为0.1pm。该方法能够满足气体扩张激光诱导荧光(FAGE)技术定量精确测量大气OH自由基对波长的要求。     

互变异构激光染料奇通红发光特性研究

本文报道应用微微秒脉冲技术测量奇通红染料荧光寿命,发现该体系荧光衰减呈现双指数衰减形式,证实了奇通红染料分子的互变异构特性.     

355 nm纳秒激光作用下荧蒽的时间分辨荧光光谱特征

多环芳烃由于具有三致(致癌、致畸、致突变)特性,其在环境中的检测受到人们广泛关注。利用时间分辨光谱技术,研究了荧蒽乙醇溶液的荧光光谱随延时时间和门宽改变的特性。研究了不同浓度荧蒽的时间分辨荧光光谱特性,以原始浓度的荧蒽为初始溶液,通过逐级稀释的方式,最终将原始溶液稀释16倍,拟合了不同稀释倍数下的荧蒽荧光强度衰减随延时时间变化的动力学曲线,得到了不同浓度荧蒽的拟合荧光寿命。研究结果表明,荧蒽的荧光光谱特性与光谱仪探测器延时时间和门宽宽度密切相关。固定延时时间,随着光谱仪门宽宽度的变化,荧蒽的荧光强度随着门宽的增大而逐渐增强。固定门宽,改变延时时间的过程中,荧蒽的荧光强度随延时时间呈现先增大,后减小的趋势。荧蒽的荧光强度随延时时间的衰减过程符合指数衰减过程,将荧蒽乙醇溶液进行逐级稀释,荧蒽荧光强度与延时时间的衰减进行指数拟合后,得到不同稀释倍数的荧蒽乙醇溶液的衰减动力学参数,随着稀释倍数的增大,拟合得到的荧蒽荧光寿命增大。多环芳烃时间分辨光谱特征的研究,可以为环境中多环芳烃的检测提供技术基础,由于不同荧光物质具有特征的荧光寿命,因此,可以利用多环芳烃与环境中其他荧光物质的不同荧光寿命特性,准确识别环境中的多环芳烃污染物。     

利用分子梳方法研究单个DNA-YOYO-1复合体的光漂白性质

利用分子梳方法结合荧光显微术对单个DNA-YOYO-1复合体的光漂白过程进行了研究,发现单个DNA-YOYO-1复合体的光漂白是一个随光照时间指数衰减的过程,并给出了DNA拓扑结构以及光照强度对光漂白过程的影响.     

银纳米粒子的SERS效应和SEF效应在微流控芯片光学检测中的应用

银纳米离子的SERS技术和SEF技术的信号检测灵敏度非常高,可以用在微流控芯片的定量分析中。为了提高微流控芯片光学检测技术的检测精度,提出一种在微通道中添加银纳米粒子来增强SYBR GreenⅠ拉曼和荧光信号的方法,并对该方法的原理和增强效果进行了研究。首先,利用准分子激光器在PMMA基板上直写刻蚀出宽200 μm、深68 μm的微通道,接着将制备的银前体溶液加入微通道,通过加热制备出表面增强拉曼（SERS）和表面增强荧光（SEF）基板,接下来对添加银纳米粒子前后的拉曼和荧光信号分别进行对比,进一步研究了微通道中不同浓度银纳米粒子对SYBR GREEN I的拉曼和荧光信号增强效果。添加银纳米粒子后,表面增强拉曼（SERS）实验的增强因子为3.5×10³,添加银纳米粒子的样品的荧光信号强度与不含银纳米粒子样品的荧光信号强度相比,约增加了1倍。结果表明,在微通道中检测SYBR Green I时通过增加银纳米粒子显著地增强了拉曼和荧光信号,这种方法可以用在以SYBR GreenⅠ做染料的微流控芯片检测技术中。     

厦门湾有色溶解有机物光漂白的三维荧光光谱研究

利用荧光激发-发射矩阵光谱(excitation-emission matrix spectroscopy,EEMs)研究了厦门湾九龙江河口中、低盐度区表层水样中有色溶解有机物在秋季天然太阳辐照下的光化学漂白。结果表明,光漂白未引起水样中类腐殖质(C, A, M)和类蛋白质(T,B)荧光峰位置的移动。5个峰的荧光强度均随辐照时间的增加而减少,其中低盐度水样的降低幅度更大,并以指示陆源河流输入的特征荧光峰C的光漂白程度最大。根据漂白速率可将各荧光团区分出易漂白和难漂白两类组分。光漂白导致T、C峰及A、C峰之间的荧光强度比值增加,说明光漂白可引起海水中溶解有机物性质的明显改变,并且也是近海类蛋白质荧光相对类腐殖质荧光占优势的一个重要控制因素。研究结果对于探究陆源有机物在近海的转化及去除过程以及海洋光学有一定的参考价值。     

用染料荧光增益增强弱增益拉曼模式的受激拉曼散射的经典理论

建立了用染料荧光增益增强弱拉曼模式的受激拉曼散射(SRS)的经典理论,详细给出了拉曼增益gR,染料荧光增益gD和总损耗α的表达式,并在其推导过程中对经典理论作了修正,最后得到了荧光增益和受激拉曼增益可以共同使SRS强度的指数部分快速增长的结果,可以很好地解释观察到的实验现象,并为其提供理论依据。     

先进的微生物芯片检测系统及其应用

发展了一种先进的微生物芯片检测方法,并研制用于芯片检测的新型数字化成像扫描检测系统。采用激光诱导荧光的检测原理设计一种新颖的CCD数字化成像扫描检测系统结构,荧光信号采集端的数值孔径NA=0．72,工作距离3．22 mm,系统检测灵敏度小于每平方微米1个荧光分子。以微生物大肠杆菌和黄单胞菌检测为例,设计基因芯片,并应用所研制的芯片检测系统实现了微生物的正确鉴定,提供了一种高效的食品安全检测整体解决方法。实验结果表明两种微生物的芯片检测实验结果稳定可靠,与国外共焦扫描仪检测的结果完全一致。     

单壁碳纳米管吸附联苯类有机物的荧光光谱分析

利用芳香族化合物对单壁碳纳米管进行了化学修饰,并利用荧光光谱以及时间分辨光谱对修饰后的单壁碳纳米管进行了表征分析.实验发现吸附对三联苯后有1个荧光峰位置发生了蓝移,这说明吸附过程使对三联苯的一些能级分布发生了变化.测量吸附前后对三联苯和蒽甲醇的荧光寿命,发现吸附后的荧光衰减曲线下降趋势更加明显,对曲线进行多指数拟合得出的荧光寿命及其数目发生了变化,分析了可能导致该现象的原因.     

光漂白聚合物波导折射率轮廓的确定

通过实验发现了光漂白聚合物薄膜厚度随光照时间按指数衰减的规律收缩,在此基础上,利用ｍ线法和精确的转移矩阵理论,由数值拟合得到的聚合物波导的折射率轮廓为费米函数。     

异丙醇-水配合液的荧光偏振和时间分辨特性

研究了紫外光照射下异丙醇-水配合液的偏振荧光光谱,以及不同荧光峰处光子强度随时间的衰变过程,计算了偏振度并讨论了其偏振特性,测试了不同峰位对应的荧光寿命并分析了其荧光发射特性.结果表明,异丙醇-水配合液在紫外光激励下发射的荧光为具有确定分子取向的部分偏振光,偏振度和各向异性度分别为0.542和0.441.在波长为220...     

Photostability comparison of CdTe and CdSe/CdS/ZnS quantum dots in living cells under single and two-photon excitations

The photostability is an outstanding feature of quantum dots (QDs) used as fluorescence probes in biological staining and cell imaging. To find out the related factors in the QD photostability, the photobleaching of naked CdTe QDs and BSA coated CdSe/CdS/ZnS QDs in human hepatocellular carcinoma (QGY) cells and human nasopharynx carcinoma (KB) cells were studied under single photon excitation (SPE) and two-photon excitation (TPE). In these two cell lines the cellular QDs were irradiated by a 405 nm continuous wave laser for SPE or an 800 nm femto-second (fs) laser for TPE. The QD photobleaching with the irradiation time was found to fit a biexponential decay. The fast decay plays a dominant role in the bleaching course and thus can be used as the parameter to quantitatively evaluate the QD photostability. The TPE decreased the QD photobleaching as compared to SPE. The BSA coated core/shell QDs had improved the photostability up to 4-5 times than the naked QDs due to the shielding effect of the QD shell. Therefore, it is better to use core/shell structured QDs as the fluorescence probe combining with a TPE manner for those long-term monitoring studies.     

四苯基卟吩激发—重态衰变的“外部重原子效应”的研究

考查了在有芳烃卤代物RX(如氯苯、溴苯和碘苯)存在时,四苯基卟吩TPP的荧光衰变现象。基于荧光衰变动力学分析,发现:在RX和TPP之间生成复合物是引起重原子效应的一个基本步骤。荧光衰变的动力学参数则进一步表明:可观察的外部重原子效应主要是由于发生分子间电荷转移相互作用而引起的。     

Measurement of the Rb D2 transition linewidth at ultralow temperature

The Rb D2 linewidth was studied using atoms cooled to a temperature of 50 μK that were contained in a magneto-optical trap. The transmission of a probe laser through the atom cloud was monitored using a CCD detector. The frequency of the probe laser was scanned across the resonance using an acousto-optic modulator. The observed lineshape was very well fitted by a Lorentzian function. The full width half maximum linewidth was examined as a function of the optical depth and the probe laser intensity. The extrapolated value at zero optical depth 6.062 ± 0.017 MHz corresponds to a 5P_3/2 lifetime of 26.25 ± 0.07 ns. This result agrees with lifetimes found in experiments that measured the temporal decay of fluorescence or photoassociation spectroscopy and is somewhat below the result of a relativistic many body perturbation calculation.     

YPO4：Pr^3＋发光的浓度和温度特性

选择激发YPO4：Pr^3 中^Pr^3离子的^3Po级级,测量了系列浓度样品不同温度下的发射光谱及^3Po与^1D2能级的发光衰减曲线,讨论了613．2nm发射光谱线的来源问题,确认是Pr^3 离子的^1D2Г3）→^3H4(Г5）的发射。研究了Pr^3 离子^3P0与^D2能级不同的浓度猝灭关系,并用静态模型对^D2衰减曲线进行了拟合,结果显示^1D2能级发光发生浓度猝来的原因主要是相邻中心的偶极－四极相互作用引起的交叉弛豫。     

Fluorescence spectroscopic study to characterize and monitor TEOS based sol–gel process for development of optical biosensors

Development of optical biosensors is an active area of research in the field of medical technology. Sol–gel matrices made from alkoxide silicates, tetraethyl orthosilicate (TEOS) appear to be suitable glassy host matrix for the sensing system. However, the major problem in the TEOS based sol–gel matrices is stability. So it is important to study dopant–matrix interaction as a function of time. In the present study, we report fluorescence emission and excited state lifetime measurements on fluorescent probes entrapped in TEOS sol–gel for monitoring the physico-chemical processes for characterization and monitoring of local environment (pores) of dopant molecule (fluorescent probes) for construction of sensing layer for optical transducer. Different types of fluorescent probes viz., Hoechst 33258 (H258) and pyranine (PY) were used. Sol–gels containing these probes were prepared at pH=6.0 and the physical and spectroscopic parameters were monitored as a function of storage time (days). The emission intensity from entrapped H258 has shown relatively higher extent of decrease during aging. The excited state fluorescence lifetime measurements on these probes depicted single exponential decay component at 5.4 ns (PY) and 3.6 ns (H258) in fresh sol–gels. After a few days of storage the sol–gel containing H258 revealed an additional short decay component whereas no such alteration could be observed with the probe molecule PY. Further confirmation of multicomponents decay was obtained by distribution analysis of lifetime of H258 where an increase in width of mean lifetime was observed with storage whereas no such change was indicated from PY. Thus it appears that H258 is a better probe molecule for characterizing and monitoring local environment of pores in sol–gel.     

Relation Between Fluorescence Decays and Temporal Evolution of Excited States

A differential equation system describing the temporal evolution of excited substates and fluorescence emission were tested using a DOPRI algorithm. The numerical solutions show that there is significant difference in the measurable parameters according to the type of connectivity among the excited substates. In the globally connected case, the fluorescence emission exhibits a double exponential behavior, and the first moment of the emitted spectrum decays with stretched exponential characterized by β < 1. In the diffusive case the fluorescence emission cannot be always fitted with double exponential, and the first moment of the emitted spectrum may decay with stretched exponential characterized by β > 1. Details of modeling and the possibilities of drawing conclusions are also presented.     

Photobleaching-Based Quantitative Analysis of Fluorescence Resonance Energy Transfer inside Single Living Cell

The current advances of fluorescence microscopy and new fluorescent probes make fluorescence resonance energy transfer (FRET) a powerful technique for studying protein-protein interactions inside living cells. It is very hard to quantitatively analyze FRET efficiency using intensity-based FRET imaging microscopy due to the presence of autofluorescence and spectral crosstalks. In this study, we for the first time developed a novel photobleaching-based method to quantitatively detect FRET efficiency (Pb-FRET) by selectively photobleaching acceptor. The Pb-FRET method requires two fluorescence detection channels: a donor channel (CH ₁ ) to selectively detect the fluorescence from donor, and a FRET channel (CH ₂ ) which normally includes the fluorescence from both acceptor and donor due to emission spectral crosstalk. We used the Pb-FRET method to quantitatively measure the FRET efficiency of SCAT3, a caspase-3 indicator based on FRET, inside single living cells stably expressing SCAT3 during STS-induced apoptosis. At 0, 6 and 12 h after STS treatment, the FRET efficiency of SCAT3 obtained by Pb-FRET inside living cells was verified by two-photon excitation (TPE) fluorescence lifetime imaging microscopy (FLIM). The temporal resolution of Pb-FRET method is in second time-scale for ROI photobleaching, even in microsecond time-scale for spot photobleaching. Our results demonstrate that the Pb-FRET method is independent of photobleaching degree, and is very useful for quantitatively monitoring protein-protein interactions inside single living cell.     

Selective Dequenching by Photobleaching Increases Fluorescence Probe Visibility

Self-quenching properties of fluorescent dyes have been developed to improve the sensitivity of fluorescent measurement. Photobleaching of Calcein at a concentration greater than the critical, self-quenching concentration actually increased fluorescence, whereas at lower concentrations photobleaching decreased fluorescence, enhancing signal to noise by almost 4000. The photobleaching-dequenching principle has been demonstrated in giant liposomes encapsulating Calcein at higher quenched concentrations. Upon photobleaching background fluorescence was reduced and the liposome fluorescence increased. Liposomes invisible in the presence of background fluorescence became visible upon photobleaching. Fluorescent lifetime was unaffected by photobleaching, whereas the lifetime decreased significantly upon dilution, allowing distinction between photobleached fluorescence particularly upon dequenching. The principle may be suited to improving fluorescence imaging and resolving fluorescent probes in particle-based assays.