基于拉曼光谱和光学二次谐波的二硒化锡结构研究

二维层状半导体材料,尤其是少数原子层时,其光电性质与晶格结构密切相关,采用合适的表征方法是关键。本文通过使用机械剥离的方法,得到了不同层数的二硒化锡,并利用光学二次谐波和拉曼光谱的表征研究了其晶体结构的性质。通过二次谐波准确确定了二硒化锡的晶轴,分析了厚度对二次谐波的影响,为确定材料的晶格结构提供了一种纯光学的手段,同时为发现二硒化锡其他非线性光学性质提供了可能性。通过拉曼光谱,发现二硒化锡层间振动模式对厚度和温度变化均较为敏感,表明二硒化锡可应用于大范围内温度的原位监测。     

Measurements of leucocyte membrane elasticity based on the optical tweezers

A 1-μm in diameter polystyrene bead coated with lectin is trapped by optical tweezers whics is formed by a focused laser beam (740nm).A leucocyte adhered to the bottom of sample cell is chosen to close to the trapped bead.When their stable combination is confirmed,the leucocyte is displaced by moving the sample stage.A“tether”is then formed between the trapped bead and the membrane.The force acting on the tether is measured by a detector equipped on the optical tweezers system.The deformation of the membrane is diverse in different contact conditions.When the contact area is small,the tether is very thin and the force on it is 7.4pN(10^-12N),while the tether is much thicker under a larger contact area and its corresponding force is about 14pN.It is presumed that the latter is related to the deformation of cytoskeleton.     

光镊拉曼光谱技术检测结肠癌细胞的研究

使用激光光镊拉曼光谱分析系统,测量了结肠癌病人的3种不同细胞的拉曼光谱。实验结果显示结肠癌细胞和正常细胞的拉曼光谱有明显的差异,这种差异可以由1002cm^-1和1300cm^-1处的峰值参数来标示。与正常细胞比,结肠癌细胞在1350cm^-1,1458cm^-1,1576cm^-1,1662cm^-1处的强度增加,表明在结肠癌组织细胞中核酸含量增加。在1300cm^-1,1442cm^-1,1647cm^-1,1739cm^-1处的强度减小,表明在结肠癌组织中脂类的含量减少。     

基于FDTD对尖端为轴锥体的光纤光镊的模拟分析

基于动量守恒,采用时域有限差分法(FDTD),仿真模拟了光纤光镊轴锥角和工作距离关系及捕获力大小和轴锥角的关系.结果表明工作距离和捕获力的大小和轴锥角度的大小有着密切的关系.模拟结果与其它相关文件报道的实验结果基本相符合.     

单光刀与单光镊激光微束系统

提出了构建一种用于细胞非接触操作的激光微束系统。该系统由 Nd:YAG激光束经声压、热膨胀、汽化等综合效应实现的光刀和 He- Ne激光束经光学动力学效应实现的光镊组成。将两激光束耦合到显微镜中 ,实现了生物细胞的捕获、移动、翻转、打孔等一系列操作。在此基础上 ,分析了形成光镊所必需产生梯度力场的条件和形成光刀对能量的要求 ,进行了系统的总体设计、关键部件设计和选择 ,构建了一套激光微束操作实验系统 ,得到了预期的试验结果。在该系统上成功地实现了非接触细胞操作 ,并对染色体进行了切割。     

Making light work with optical tweezers.

Microscopic objects, including biological material, can be remotely manipulated with tightly focused beams of infrared laser light. The use of optical traps, or 'optical tweezers', holds great promise for noninvasive micromanipulation and mechanical measurement in cell biology. Optical tweezers are the 'tractor beams' of today's technology.     

基于反应体系的表面增强拉曼光谱快速检测乙基麦芽酚

以铁离子(Fe~(3+))为媒介,鞣酸还原氯金酸制备的金纳米粒子(Au NPs)作为表面增强拉曼散射(SERS)基底,实现比色-散射光谱双响应,快速鉴别食品中的乙基麦芽酚.其中比色法中,对乙基麦芽酚的检测限为0.50 mg·mL~(-1).SERS检测中,利用Fe~(3+)和乙基麦芽酚的络合作用,乙基麦芽酚的最低检测限降低到0.01 mg·mL~(-1),线性范围为0.05～1.00 mg·mL~(-1).该方法使用的仪器简单,操作方便,可对样品中的乙基麦芽酚进行现场直接测定.     

Compliance of bacterial flagella measured with optical tweezers

The development of the gradient force optical particle trap ('optical tweezers') has made it possible to manipulate biological materials using a single beam of laser light. Optical traps can produce forces in the microdyne range on intact cells without causing overt damage: such forces are sufficient to arrest actively swimming bacteria and can overcome torque generated by the flagellar motor of a bacterium tethered to a glass surface by a flagellar filament. By calibrating the trapping force against Stokes' drag and measuring the twist that is sustained by this force, we determined the torsional compliance of flagella in tethered Escherichia coli and a motile Streptococcus. Flagella behaved as linear torsion springs for roughly half a revolution, but became much more rigid when turned beyond this point in either direction.     

Tying a molecular knot with optical tweezers.

Filamentous structures are abundant in cells. Relatively rigid filaments, such as microtubules and actin, serve as intracellular scaffolds that support movement and force, and their mechanical properties are crucial to their function in the cell. Some aspects of the behaviour of DNA, meanwhile, depend critically on its flexibility-for example, DNA-binding proteins can induce sharp bends in the helix. The mechanical characterization of such filaments has generally been conducted without controlling the filament shape, by the observation of thermal motions or of the response to external forces or flows. Controlled buckling of a microtubule has been reported, but the analysis of the buckled shape was complicated. Here we report the continuous control of the radius of curvature of a molecular strand by tying a knot in it, using optical tweezers to manipulate the strand's ends. We find that actin filaments break at the knot when the knot diameter falls below 0.4 microm. The pulling force at breakage is around 1 pN, two orders of magnitude smaller than the tensile stress of a straight filament. The flexural rigidity of the filament remained unchanged down to this diameter. We have also knotted a single DNA molecule, opening up the possibility of studying curvature-dependent interactions with associated proteins. We find that the knotted DNA is stronger than actin.     

基于调制光谱研究GaN的光学特性

利用调制光谱技术研究了以分子束磊晶法成长于GaAs基板上的GaN薄膜的光学特性。结果表明,在PR、CER及PzR谱线中均可观察到激子跃迁信号E0与旋轨道分裂信号(E0+Δ0),且分裂量Δ0约为22 meV。在15³00 K的温度范围内均可观测到激子跃迁信号E0、自旋轨道分裂信号(E0+Δ0)及DA-Pair信号;但温度在400 K和500 K时谱线中只存在激子跃迁信号E0与DA-Pair信号,而观察不到信号(E0+Δ0)。随着温度的升高,样品的跃迁信号E0与自旋轨道分裂信号(E0+Δ0)逐渐向低能量反方向移动。     

基于拉曼镊子的发酵过程单细胞分析：应用与展望

微生物发酵是个复杂的过程,而细胞间的异质性对微生物发酵性能有重要的影响。通过单细胞分析了解微生物细胞的异质性,利于发酵环境的优化,从而减少细胞间的异质性,提高发酵性能。整合显微拉曼光谱和光学微操控的拉曼镊子是实时、无损、无须标记且快速灵敏的单细胞分析方法。本文重点回顾拉曼镊子在聚酯、类胡萝卜素、脂肪酸、生物乙醇以及重组蛋白等发酵生产过程中的应用,并分析其在应用上存在的不足。在克服自身不足、融合新的分析技术与数据处理方法后,拉曼镊子将是了解细胞异质性、认知复杂生物过程的有力手段。     

基于液芯光纤的水中甲烷拉曼检测技术

根据经典电磁理论和量子理论分析了拉曼光谱技术,探讨了共振拉曼效应对提高散射光强所起的作用．采用LRS—III型激光拉曼光谱仪对甲烷水溶液进行了拉曼检测实验,实验结果验证了水中甲烷拉曼检测的可行性．根据液芯光纤传光原理分析了输出拉曼光功率与损耗系数和光纤长度的关系,利用LabVIEW软件对液芯光纤的拉曼增益作用进行了仿真,仿真结果表明液芯光纤可提高拉曼光强达10^3倍．针对水中甲烷含量比较低的特点,提出基于液芯光纤并共振拉曼效应的方法,可提高拉曼光强接近10^9倍．     

Bead movement by single kinesin molecules studied with optical tweezers

Kinesin, a mechanoenzyme that couples ATP hydrolysis to movement along microtubules, is thought to power vesicle transport and other forms of microtubule-based motility. Here, microscopic silica beads were precoated with carrier protein, exposed to low concentrations of kinesin, and individually manipulated with a single-beam gradient-force optical particle trap ('optical tweezers') directly onto microtubules. Optical tweezers greatly improved the efficiency of the bead assay, particularly at the lowest kinesin concentrations (corresponding to approximately 1 molecule per bead). Beads incubated with excess kinesin moved smoothly along a microtubule for many micrometres, but beads carrying from 0.17-3 kinesin molecules per bead, moved, on average, only about 1.4 microns and then spontaneously released from the microtubule. Application of the optical trap directly behind such moving beads often pulled them off the microtubule and back into the centre of the trap. This did not occur when a bead was bound by an AMP.PNP-induced rigor linkage, or when beads were propelled by several kinesin molecules. Our results are consistent with a model in which kinesin detaches briefly from the microtubule during a part of each mechanochemical cycle, rather than a model in which kinesin remains bound at all times.     

光镊技术在生命科学研究中的发展与应用

介绍了光镊技术的原理和系统结构,追踪了光镊操作和探测技术从微米到纳米的进展,最后给出了纳米光镊在生物技术领域的应用.     

鹅去氧胆酸分子钳对中性分子的识别性能研究

利用差紫外光谱滴定法考察了鹅去氧胆酸分子钳1～5对苯胺、对硝基苯胺、对甲氧基苯胺等中性分子的识别性能,测定了主客体间的结合常数(ka)和自由能变化(ΔG°).结果表明,主体对所考察的客体分子显示良好的识别作用,主客体间形成1∶1型超分子配合物,最大结合常数可达1292.51 L.mol-1,识别作用的主要推动力为氢键,范德华力等的协同作用.讨论了主客体间形状、大小匹配和几何互补等因素,对形成超分子配合物的影响,并利用计算机分子模拟作为辅助手段对实验结果与现象进行了解释.     

钛酸铋纳米晶的喇曼光谱和红外光谱研究

利用MOD方法制备了钛酸铋（Bi4Ti3O12（BTO））纳米晶．采用空间群结合晶格动力学分析了BTO晶体中的晶格振动模,理论预测了最多可能产生24个喇曼散射峰和28个红外吸收峰．喇曼散射和红外吸收实验结果与理论预测相比,峰数有大量减少．将此归因于谱带的叠合,某些谱线强度太弱,以及BTO晶体阴离子基团中TiO6八面体的存在等原因．对主要的喇曼峰和红外吸收峰采用TiO6八面体的内振动模进行指认,发现八面体的畸变程度很大,导致某些谱线产生了频移和劈裂．     

Raman spectroscopy of single quantum well wires

We used the micro-Raman spectroscopy to investigate the V-grooved quantum well wires (QWWs), and first observed and assigned the Raman spectra of single QWW. They were the disorder induced modes at 223 and 243 cm⁻¹, confined LO mode of GaAs QWW at 267 cm⁻¹, and higher order peaks of disorder induced modes at 488 and 707 cm⁻¹.     

NiSi薄膜的拉曼研究

在Si(100)衬底上通过电子束蒸发法外延生长晶体取向单一的NiSi薄膜材料. 利用极化拉曼实验分析技术并结合群论以及晶格振动理论对NiSi薄膜拉曼峰的对称性进行指认. 在此基础上计算了各类声子峰对应的晶格振动模式. 我们还讨论了两种不同的激光退火方法对晶体质量的影响.     

具有多手性中心的新型脱氧胆酸分子钳的微波合成

在微波辐射条件下,以脱氧胆酸甲酯为spacer,3位通过三光气桥连对三氟甲基苯胺为非手性臂,12位通过三光气桥连L-氨基酸甲酯为手性手臂,合成了4个新型多手性中心分子钳人工受体．其结构经IR,1HNMR,MS及元素分析确证．与常规加热的一般合成方法相比,该法具有溶剂用量少,操作简单,安全,反应速度快和产率高等优点．     

聚对苯二甲酸乙二酯分子振动模式的特性研究

采用拉曼光谱法对聚对苯二甲酸乙二酯纤维的拉曼光谱特性进行研究,对聚对苯二甲酸乙二酯纤维分别进行酸、碱、盐处理,获得酸、碱、盐处理前后纤维的拉曼光谱,并对拉曼光谱的特性进行了分析与比较.结果表明,与未经处理的聚对苯二甲酸乙二酯相比,Na OH处理的PET在波数大于1 750cm-1时强度低于未经处理的PET,酸性染料对聚酯纤维的亲和力比较高,H2SO4处理的PET拉曼光谱和不经任何处理的PET的拉曼光谱相比,发生明显变化,强度显著减弱.而Cu SO4处理的PET拉曼光谱峰值强度明显高于未经处理PET纤维的拉曼光谱峰值强度.表明酸处理能够抑制聚对苯二甲酸乙二酯分子的振动模式,盐处理能够激发聚对苯二甲酸乙二酯分子的振动模式.