金属／洋葱状富勒烯的HRTEM与光学性能研究

利用金属/洋葱状富勒烯奇异的分子结构和独特的光电性能，引发世人研究采用多种方法制备富勒烯复合材料，将金属纳米微粒加入到洋葱状富勒烯的笼状中空内，用以制成具有特殊性能的纳米材料，并逐渐成为研究热点。本实验采用催化化学气相沉积法制备出了金属/洋葱状富勤烯，采用SEM和HRTEM进行结构表征，并对其荧光性能进行了分析。     

Pt／洋葱状富勒烯复合纳米微粒的制备

洋葱状富勒烯（OLFs）是继C60、碳纳米管之后人们发现的又一种崭新的全碳物质，自1992年Ugarte发现洋葱状富勒烯（onion-like fullerenes，OLFs）以来，其研究成为物理、化学和纳米材料科学等领域的热点。OLFs独特的中空笼状及同心壳层结构，可以容纳原子团簇、纳米微粒和金属碳化物等，具有许多特殊性能，有望在能源材料、高性能高温耐磨材料、超导材料和生物医用材料等领域被广泛应用。     

煤制备洋葱状富勒烯的HREM分析

采用直流电弧放电法以煤为原料制备富勒烯。实验采用工作气体为Ar，催化剂选用纳米Cu颗粒。所得到的阴极产物的HREM观察表明：在适当的工艺条件和催化剂作用下，可宏量制备出碳纳米颗粒—洋葱状富勒烯(nano-structured onion-like-fullerenes；NSOFs)，直径为25～40nm；同时生成一些特殊形状的碳纳米管，其形状为探讨高温条件下碳纳米管向洋葱状富勒烯转变提供了有力的证据；煤的独特结构使其在制备过程中沿两条路径形成富勒烯：非晶态碳原子的石墨化和芳香结构的重排。X射线能谱分析表明煤中舍有Mg、Si、S等微量矿物元素，这些元素的存在意味着可能对洋葱状富勒烯的生成有催化作用，     

纳米结构洋葱状富勒烯的CCVD法制备

纳米结构洋葱状富勒烯(NSOFs)是准球体同心壳层形状的碳笼构成的富勒烯分子，由于其独特的结构及性能，具有极富潜力的应用前景。现有的制备洋葱状富勒烯的方法有高能电子束辐照含碳物质、水中电弧放电法、纳米金刚石粉热处理和射频等离子CVD等。但由于上述种种方法的制备条件苛刻，不适合工     

氧化物催化电弧法制备洋葱状富勒烯的研究

纳水洋葱状富勒烯作为富勒烯家族中的新成员，自1992年被发现以来，已在全世界范围内引起了各国学者的广泛关注和极大兴趣。然而，由于缺乏有效宏量制备纳米洋葱状富勒烯的方法，目前的研究仍处于实验室阶段。我们课题组在自制的直流电弧放电设备中，不断改进放电工艺，用多种催化剂(Ti、Fe、Ni、     

真空热处理条件下纳米洋葱状富勒烯的结构

纳米洋葱状富勒烯（NanoOnion-like Fullerenes,NOLFs）作为富勒烯家族的一个新成员自1992年被发现以来由于其独特的中空笼状结构和潜在的应用前景引起研究者广泛的关注。目前，制备NOLFs的主要方法有电弧放电法、等离子体法，化学气相沉积法和真空热处理法。本文以金属Ni为催化剂，石墨粉为碳源探讨了真空热处理条件下温度对NOLFs结构形态的影响。     

CVD法制备纳米洋葱状富勒烯的研究

纳米洋葱状富勒烯（NOLFs）的常用制备方法有：直流电弧法、高能电子束辐照法、化学气相沉积法、真空热处理法、机械球磨法和射频等离子法等。由于这些方法目前制备出的NOLFs形状不一，颗粒不均匀，有的不完全是球形，所以我们采用的是将二茂铁溶于环已烷中的CVD法制备NOLFs，     

Y-型纳米碳管的HRTEM研究

本文对Y-型纳米碳管的形貌和微观结构进行了HRTElVl表征,并探讨了其形成机理。结果表明：形成的Y-型纳米碳管内包裹Fe纳米微粒,管径分布在50—60nm之间;在反应中由于催化剂Fe纳米微粒粒径、形状和表面曲率不同,使纳米碳管在生长过程中产生分支,形成Y-型纳米碳管。     

聚乙二醇放电介质中洋葱状富勒烯的制备与表面修饰

以分子量为600、400和200的聚乙二醇（PEG）为介质电弧放电法制备了洋葱状富勒烯（OLFs）;利用空气氧化法于450℃条件下对产物进行了提纯,并用含氧射频等离子体对纯化后的OLFs进行了表面氧化修饰;用场发射扫描电镜、高分辨透射电镜、X射线衍射和傅立叶变换红外光谱对所得产物进行了表征和分析。结果表明：在PEG200中放电制得的OLFs粒径均匀,石墨化程度较高;空气氧化法能提高OLFs产物的纯度;当氧气含量为20%时,表面氧化修饰效果明显。     

聚乙二醇放电介质中洋葱状富勒烯的制备与表面修饰

以分子量为600、400和200的聚乙二醇（PEG）为介质电弧放电法制备了洋葱状富勒烯（OLFs）;利用空气氧化法于450℃条件下对产物进行了提纯,并用含氧射频等离子体对纯化后的OLFs进行了表面氧化修饰;用场发射扫描电镜、高分辨透射电镜、X射线衍射和傅立叶变换红外光谱对所得产物进行了表征和分析。结果表明：在PEG200中放电制得的OLFs粒径均匀,石墨化程度较高;空气氧化法能提高OLFs产物的纯度;当氧气含量为20％时,表面氧化修饰效果明显。     

太赫兹波段金属光子晶体光纤增强拉曼散射现象的研究

深入探究了金属光子晶体光纤的表面增强拉曼散射现象,建立了时域有限差分法的平板结构的模型,利用观察到的超强透射现象得到了发生拉曼散射的理论依据。金属光子晶体在太赫兹波照射下的表面电磁场增强效果的实验中得到:入射波能量越大,更易激发产生金属光子晶体的表面等离子体共振,可以使金属表面的增强效果得到较大增强;拉曼散射效果在太赫兹波段内十分明显,吸收光谱效果和荧光效应也相对较小,能够显著提高灵敏度和分辨率。     

A novel technique for suppression of parasitic superfluorescence in backward Raman amplifiers

The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.     

Exploring How to Increase the Brightness of Surface‐Enhanced Raman Spectroscopy Nanolabels: The Effect of the Raman‐Active Molecules and of the Label Size

Due to the surface‐enhanced Raman scattering (SERS) effect, SERS labels based on noble‐metal nanoparticles loaded with Raman‐active molecules are good candidates for ultrasensitive multiplexed assays and in vitro/in vivo imaging. However, understanding how to maximize the brightness of such labels is of paramount importance for their widespread application. The effective differential Raman scattering cross‐section (dσ_R/dΩ) of SERS labels made of pegylated gold nanoparticles loaded with various Raman active molecules (Raman reporters) is studied. It is found that proper choice of the Raman reporter and of nanoparticle size can enhance the dσ_R/dΩ by several orders of magnitude. The experimental results are understood by considering the molecular cross‐section for resonant Raman scattering and the local electromagnetic enhancement factor (G_SERS) in the nearby of gold nanoparticles. These results are useful to guide the design of SERS labels with improved performances and to provide a reference for the comparison of the absolute value of the dσ_R/dΩ of SERS labels based on metal nanoparticles.     

金属尖端角度对表面增强拉曼散射的影响

金属尖端对于表面拉曼散射有增强的效果,但尖端的尖锐程度对于表面增强拉曼散射(Surface-Enhanced Raman Scattering, SERS)的影响很少有定量的报道。为了研究角度大小与SERS的关系,需要制备具有不同角度的结构。利用数字微镜设备（Digital Micro mirror Device, DMD）进行光学投影光刻制备了四组样品,分别具有30°60°90°120°角金属微结构,测量了这些结构对应的SERS谱,研究金属尖端角度大小对于SERS的影响。研究发现,锐角具有更好的表面增强拉曼散射效果,而且增强效果对角度依赖强烈,角度越小增强效果越明显;钝角情况下,SERS对于角度大小依赖的敏感度下降。     

Determination of the spectral width of Raman gain regions for different far infrared laser gases using a metal mesh Fabry Pérot interferometer

In this paper we report on the determination of the spectral width of Raman gain regions for different far infrared laser gases using a metal mesh Fabry Pérot interferometer. By use of broadband pump radiation emitted from a high pressure CO₂ laser we generated far infrared radiation within the Raman gain regions via stimulated Raman scattering. The spectral width of the far infrared radiation was determined using a Fabry Pérot interferometer in high interference order. We applied the method to study stimulated Raman scattering in D₂O and methylfluoride at different gas pressures.     

用于纳米劈裂技术的新型芯片及增强拉曼光谱实验

为了定量研究纳米颗粒的间距对拉曼(Raman)光谱强度的影响,研制了具有高稳定性的纳米劈裂芯片及装置。利用此芯片及装置,可以获得纳米金属桥断裂后自动形成的两针状纳米电极(纳米颗粒),并且能在pm级精度上操纵两纳米电极间的距离,以观察相应拉曼光谱强度的变化。在利用两纳米电极作为增强体的基础上引入了第3纳米电极,以观察其位置对拉曼光谱信号的影响。实验结果表明,光谱信号的强度强烈依赖于3纳米电极的相对位置,第3纳米电极的引入能进一步提高增强因子,为拉曼光谱增强机制的理论研究提供了重要参考数据。     

Plasmon dispersion for a modulated two-dimensional electron gas

Raman scattering measurements of the dispersion of intrasubband plasmons in a two-dimensional electron gas under a biased linear metal grating are presented. The momentum resolution of the Raman experiment allows a large range of wavevectors to be probed, both perpendicular and parallel to the grating fingers; in both configurations, grating assisted scattering from plasmon modes is observed. The plasmon dispersion showed gaps at the boundaries of the mini-Brillouin zones defined by the grating periodicity. Semi-classical calculations of the electrodynamics of the system, based on a scattering matrix approach, demonstrate that these energy gaps are due both to the periodic screening effects of the grating and to a lateral modulation of the electron density. The form of the plasmon dispersion was analysed from calculations of the dielectric response of a modulated two-dimensional electron gas.     

脉冲激光改性金属纳米薄膜的等离子体特性

在室温环境下,实验采用Nd\:YAG光纤脉冲激光器辐照银(Ag)、铜(Cu)、铝(Al)三种光滑连续的金属薄膜,制备出了对应的三种金属纳米颗粒薄膜。通过调节激光扫描速率可以实现三种金属纳米颗粒薄膜的局域表面等离子体共振(LSPR)波长和强度的调谐。其中,Ag纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现出较宽的调谐范围,Cu纳米颗粒薄膜在可见光波段的等离子体吸收峰的波长和强度均表现较小的调谐范围,Al纳米颗粒薄膜在紫外光波段的等离子体吸收峰窄而尖锐,且LSPR波长调谐范围也较小。与激光辐照前的三种金属薄膜相比,激光辐照后生成的三种金属纳米颗粒薄膜出现了更强的表面增强拉曼散射信号。有限差分时域仿真模拟出的样品的电场强度分布与实验得到的表面增强拉曼散射结果一致。     

Micro‐Raman Scattering Imaging of Langmuir–Blodgett Surface Relief Gratings

Surface relief gratings (SRGs) recorded on Langmuir–Blodgett (LB) films of an azobenzene homopolymer were visualized using micro‐Raman imaging. Raman scattering (RS) was achieved using the 780 nm laser line while pre‐resonance Raman scattering (pre‐RRS) and resonance Raman scattering were achieved using the 633 and 514.5 nm laser lines, respectively. Pre‐surface‐enhanced resonance Raman scattering (pre‐SERRS) and surface‐enhanced resonance Raman scattering (SERRS) were collected for the LB films covered with a 6 nm thick silver island film. The SRG could be chemically identified by the spatial variation in the Raman signal scattered by the film due to a concentration gradient. The pre‐SERRS provided signals of the same intensity along and across the grooves, indicating that the molecular architecture at the SRG surface is the same at the peaks as in the valleys.     

喇曼散射的数值仿真及其应用探索

为了研究喇曼散射的全过程及其规律,首先,采用数值仿真的方法,基于对喇曼散射耦合微分方程的量纲重新匹配,演示喇曼散射光谱产生及其演化的过程,给出自发喇曼散射向受激喇曼散射过渡的结果。结果表明:阈值的意义突出,阈值前后的喇曼散射光谱截然不同;抽运光强大于阈值以后,喇曼散射光谱呈现出三个典型规律,即抽运光强和散射光强峰值出现的光纤长度呈反向关系;抽运光强越大,散射光强峰值和抽运光强的比值越大;散射光谱在同级内和不同级间都存在能量红移。然后,在已有研究的基础上,总结喇曼散射的各种实际应用,特别是应用于光纤喇曼放大器的研制。对于喇曼散射的理论和应用研究以及相应的实验工作有一定的参考价值。