Raman晶体的研究进展

概述了应用于激光变频技术的Raman介质的研究现状,总结了几种常用的Raman晶体的受激Raman特性.重点介绍了双钨酸盐体系中Raman晶体的性能,最后展望了Raman晶体的发展.     

不同激光波长和功率下的Bi2Se3单晶Raman光谱

采用改良Bridgman法制备出优质Bi_2Se_3单晶。X射线衍射仪和扫描电子显微镜测试结果显示,晶体沿[001]方向生长,结晶性能好。采用两种波长(532和785 nm)及不同功率的激光光源,对Bi_2Se_3单晶体(003)面进行了Raman光谱研究。结果表明:在功率较高时,随着激光功率的增加,Raman特征峰系统性红移和半高宽增大,此时峰位红移是由激光功率的增加,测试区域温度升高,晶格膨胀和声子间的非简谐振动耦合共同导致;在功率较低时,热膨胀可能是造成Raman峰位红移的主要原因。     

Nd:NaY(WO4)2晶体的生长及其性能

NdNaY(WO4)2(简称NdNYW)是一种性能优良的激光晶体.采用提拉法生长出了四方晶系白钨矿结构的NdNYW晶体.通过热重-差热分析得到晶体的熔点为1 209.07℃,测试了NdNYW晶体的红外光谱和Raman光谱,并分析了晶体的吸收光谱.结果表明该晶体在804,752,586 nm附近有较强、较宽的吸收峰,适合于半导体激光器泵浦.讨论了晶体的红外和Raman光谱中各峰的振动归属.     

热退火条件对磷锗锌晶体性质的影响

以高纯度的Zn,Ge和P粉末作为原料,采用垂直Bridgman法生长了磷锗锌（ZnGeP2,ZGP）晶体;分别在真空、磷蒸汽和ZGP晶体粉末中对生长的ZGP晶体进行了退火。测量了不同的退火条件下ZGP晶体中各元素的含量、激光损伤阈值、透过光谱和Rarllarl光谱。研究表明：在ZGP晶体粉末中退火后的晶体激光损伤阈值为96．43MW／cm^2,比在真空、磷蒸汽中退火的高：在近红外区域的吸收有所减少。Raman光谱测量结果表明,晶体的Ranqan振动模的数量发生了变化,表明退火环境对ZGP晶体的结果有一定影响。在ZGP晶体粉末中退火的ZGP晶体的性能有明显改善。     

硅酸锆分子振动模及其高温原位Raman光谱

用密度泛函理论对硅酸锆常温下的振动模进行模拟计算,并与实测的Raman和红外光谱进行了对比,解释了各振动模的归属.对硅酸锆晶体在升温过程中的Raman光谱的变化进行了研究.结果表明:随着温度上升,内振动模的红移明显,υ3(SiO4)伸缩振动模(B1g)红移最大,波数从常温时的1 006 cm-1红移至1 823 K时的937 cm-1.各振动模不断展宽且相对强度减弱,表明硅酸锆在升温过程中逐渐无序化,但[SiO4]四面体并没有聚合.升温过程中硅酸锆分解成ZrO2和SiO2.     

理化所亚硒酸盐非线性光学材料探索取得新进展

正非线性光学晶体是一类重要的光电功能晶体。它通过倍频、和频、差频、光参量放大和多光子吸收等非线性过程,可以对激光进行调制和操纵。这类晶体被广泛应用于激光频率转换、四波混频、光束转向、图像放大、光信息处理、光存储、光纤通讯、水下通讯等研究领域。亚硒酸盐化合物因含有活性孤对电子Se4+,在外光电场作用下容易诱导出强的极化,从而产生大的非线性光学效应,因而在二阶非线     

AbxAnxDiy硅酸盐熔体结构及其结晶相的高温Raman光谱研究

运用高温Raman光谱测试技术 ,对共结线附近一系列的AbxAnxDiy 样品进行了升温过程的研究。系统地对比分析了这一系列样品的玻璃 -晶体 -熔体的Raman光谱特征。低温玻璃与高温熔体在结构上虽然很相似 ,但确实存在差别。晶体与玻璃和熔体的特征峰有相似性 ,反映了晶体结构对熔体结构的继承性。晶体Raman峰的强度变化规律与温度和成分关系 ,反映了相图中不同首晶区的结晶过程特点和晶体含量的变化关系。同时 ,通过对高频区的解谱研究了体系中各结构单元的种类及含量与温度的关系     

天然绿柱石类宝石化学成分、结构和物相的无损分析

通过便携式能量色散型X射线荧光(p XRF)、X射线衍射(XRD)、激光Raman光谱(LRS)等技术分别对天然绿柱石类宝石样品的化学成分、结构和物相进行了无损分析。同时,为弥补p XRF对轻元素测量上的不足,探索应用激光诱导击穿光谱(LIBS)对样品中的轻元素Be和Li进行了定性分析。根据XRD的分析结果,得到绿柱石单晶宝石样品的特征衍射峰晶面间距d=0.786 63、0.396 39、0.265 11 nm。对14件样品进行电子顺磁共振分析,在此基础上结合化学成分研究了Cr3+、V3+、Fe3+等离子的致色机理。同时,根据I型水、II型水的Raman光谱相对强度对样品中碱金属的存在形式进行了讨论。上述研究将为无损分析技术在珠宝市场中的应用提供参考信息。     

高温高压下利用金刚石压腔实验技术对材料Raman光谱的研究

金刚石对顶砧装置(diamond anvil cell, DAC)是静态超高压装置的一种,由于金刚石具有高的硬度和良好的透光性,因此这种装置所实现的压力和能测量物性的种类都优于其他高压装置.Raman 光谱是表征物质结构及其变化的一种重要手段,DAC 超高压实验技术与激光Raman 光谱测试方法相结合, 为高压下物质结构相变研究提供了一种有效途径.实验利用金刚石压腔实验技术在高温高压条件下对氧化镓、硫酸锶固体材料进行了Raman光谱的测量.     

中远红外及太赫兹波段非线性晶体硒化镓

中远红外及太赫兹波段激光在国防和民用领域都有非常突出和迫切的需求,硒化镓(GaSe)晶体是一综合性能优异的红外非线性光学材料,通过差频产生和光学参量振荡可实现这两个波段的可调谐激光输出。综述了GaSe晶体及掺杂晶体在合成、生长、掺杂性能及差频产生中远红外及太赫兹辐射方面的最新研究成果,重点介绍了GaSe晶体及掺杂晶体的光学、力学性能,非线性性能及它们在频率转换方面的应用性能。通过全面的分析找出综合性能最优的掺杂晶体种类。     

In Situ Ultraviolet Raman Study on the Phase Transition of Hafnia up to 2085 K

We have recently demonstrated that the Raman scattering through ultraviolet (UV) excitation is eminently well suited for in situ investigation of materials at high temperatures up to 1773 K. Here we report successful Raman measurements of HfO₂ up to 2085 K, using only a 100 mW power of UV laser line. The monoclinic-to-tetragonal transformation finished around 2080 K on heating, while the monoclinic phase appeared at 2018 K on cooling.     

Experimental methods in chemical engineering: Raman spectroscopy

When photons impinge on a substrate, most scatter with the same frequency (elastic scattering or Rayleigh dispersion) and only 10^?7 scatter with a different energy (inelastic scattering). This inelastic interaction (Raman scattering) exchanges energy in the region of molecular vibrational transitions for crystalline and amorphous materials. Raman bands in a spectra represent vibrational transitions, like infrared, however the selection rules are different. Typically, the vibrations that are intense in Raman are weak in infrared and vice versa. A remarkable feature of the Raman effect is that it is highly sensitive to nanocrystals, even below 4 nm, which are too small to generate XRD patterns. Plasmonic enhancement, like surface‐enhanced Raman spectroscopy (SERS) boost the Raman signal by 10⁴, providing single‐molecule detection capability. Glass, quartz, and sapphire are transparent to Raman effect (depending on the energy of the incident excitation radiation), which makes it ideal to examine materials under reaction conditions (in‐situ cells and operando reactors that operate over a broad range of temperature, pressures, and environments). Raman spectroscopy emerged in the 1930s; however, infrared spectrometry displaced it. With the advent of powerful lasers in the 1970s, more researchers began to apply Raman routinely. In 2019, the Web of Science indexed 20 400 articles mentioning Raman against 50 000 articles mentioning infrared. Chemical engineers apply Raman less frequently than in material science, physical chemistry, and applied physics, with 887 articles vs 6250, 3700, and 3510 for the other disciplines. A bibliometric analysis identified four research clusters centred on thin films and optics, graphene and nanocomposites, nanoparticles and SERS, and photocatalyst.     

Temperature Dependence of the Raman Spectrum in Lithium Oxide Single Crystal

Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm^-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm^-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.     

Resonance raman spectroscopy of polydiacetylene langmuir-blodgett films

Resonance Raman excitation profiles of two vibrational modes have been measured for Langmuir-Blodgett films of a polydiacetylene. The polymer films were formed by exposing multilayer samples of the Cd salt of 10,12-pentacosadiynoic acid to ultraviolet radiation. Raman spectra were measured for incident laser photon energies between 1.85 and 2.20 eV (670-564 nm), the region over which the films exhibited optical absorption associated with an electronic transition of the π-electrons on the conjugated backbone. The excitation profiles have been used to determine both the strength of the vibronic coupling and the differences in vibrational frequency between the ground and excited states. The results are in reasonable agreement with those obtained previously for polydiacetylene single crystals.     

用于硅酸盐熔体微结构研究的高温Ramam光谱技术

硅酸盐熔体微结构通常在熔态下进行实验研究，而不是采用淬冷物质或玻璃样品的间接研究方法。为此比较了当前若干微结构测试方法用于高温的可能性，方法的特点，适用范围和缺陷。此处介绍一种高温Raman光谱技术，它配备了显微热台，实现了高温达1623K的共焦显微Raman；并采用了光谱信号的时间分辨检测技术，实现了可达2023K温度下的宏观Raman，拓展了Raman光谱研究高温物质结构的应用。通过对硅酸盐等熔体的Raman光谱测定和相关淬冷玻璃光谱的比较研究，表明高温Raman光谱是实时和原位研究熔体微结构的有效实验方法，同时探讨了将电荷耦合探测技术引入高温Raman光谱技术的可行性。     

铝硅酸盐矿物的Raman振动特征解析

分别测定了蓝晶石、红柱石和夕线石3种铝硅酸盐天然矿物晶体的Raman光谱,并利用Materials Studio3.0软件计算3种矿物的Raman振动频率,分析其简正振动模式,确定了三种矿物特征谱峰的归属,解析了铝对铝硅酸盐Raman光谱振动特征的影响.结果表明:随着四配位铝的增加(从蓝晶石、红柱石到夕线石),800～1 200 cm-1波数区间内谱峰频率降低,该区间的谱峰归属于Si-Onb间非桥氧对称伸缩振动;700～800 cm-1区间内出现的谱峰归属于Al-Onb间非桥氧的对称伸缩振动.当铝全部为六配位时,会引起800～1 200 cm-1区间内的谱峰向高频方向迁移.这为进一步利用Raman光谱来研究硅酸盐玻璃和熔体结构中铝的作用提供了重要依据.     

Spatially Resolved Raman Spectroscopy Study of Transformed Zones in Magnesia-Partially-Stabilized Zirconia

Raman vibrational spectroscopy provides an effective phase characterization technique in materials systems containing particle dispersions of the tetragonal and monoclinic polymorphs of zirconia, each of which yields a unique Raman spectrum. An investigation is reported to assess a novel, spatially resolved Raman spectroscopy system in the study of transformed zones surrounding cracks in partially stabilized MgO–ZrO₂ (PSZ). The experimental arrangement uses an imaging (two-dimensional) photomultiplier tube to produce a one-dimensional Raman profile of phase compositions along a slitlike laser beam without translation of either the sample or the laser beam and without scanning the spectrometer. For the present optical configuration, the spatial resolution is estimated to be equivalent to the detector resolution of 28 pm and does not appear to be reduced because of secondary scattering events in the PSZ. Results from phase characterization studies of the size, frontal morphology, and extent of transformation of transformation zones surrounding cracks produced under monotonic and cyclic loading conditions are presented. Particularly large zones are observed in the peak-toughened material, extending 1300 μm ahead of the crack tip with widths of up to 3000 μm. Good agreement is found with similar results determined using optical interference microscopy.     

Current and Future Advancements of Raman Spectroscopy Techniques in Cancer Nanomedicine

Raman scattering is one of the most used spectroscopy and imaging techniques in cancer nanomedicine due to its high spatial resolution, high chemical specificity, and multiplexity modalities. The flexibility of Raman techniques has led, in the past few years, to the rapid development of Raman spectroscopy and imaging for nanodiagnostics, nanotherapy, and nanotheranostics. This review focuses on the applications of spontaneous Raman spectroscopy and bioimaging to cancer nanotheranostics and their coupling to a variety of diagnostic/therapy methods to create nanoparticle-free theranostic systems for cancer diagnostics and therapy. Recent implementations of confocal Raman spectroscopy that led to the development of platforms for monitoring the therapeutic effects of anticancer drugs in vitro and in vivo are also reviewed. Another Raman technique that is largely employed in cancer nanomedicine, due to its ability to enhance the Raman signal, is surface-enhanced Raman spectroscopy (SERS). This review also explores the applications of the different types of SERS, such as SERRS and SORS, to cancer diagnosis through SERS nanoprobes and the detection of small-size biomarkers, such as exosomes. SERS cancer immunotherapy and immuno-SERS (iSERS) microscopy are reviewed.     

Size-dependent Fano Interaction in the Laser-etched Silicon Nanostructures

Photo-excitation and size-dependent Raman scattering studies on the silicon (Si) nanostructures (NSs) prepared by laser-induced etching are presented here. Asymmetric and red-shifted Raman line-shapes are observed due to photo-excited Fano interaction in the quantum confined nanoparticles. The Fano interaction is observed between photo-excited electronic transitions and discrete phonons in Si NSs. Photo-excited Fano studies on different Si NSs show that the Fano interaction is high for smaller size of Si NSs. Higher Fano interaction for smaller Si NSs is attributed to the enhanced interference between photo-excited electronic Raman scattering and phonon Raman scattering.