拉曼文章

Stress, Strain, and Raman Spectroscopy

Stress and strain are terms that are often used interchangeably when discussing the characteristics of materials. Nevertheless, their meanings are different. Stress is a force per unit area applied to an object, and strain is the effect on the object from the stress. Specifically, strain is the change in the positions of the atoms or the lengths of the chemical bonds within the object that are induced by the application of stress. Here, we discuss the distinction of these terms, and their mathematical forms as applied to crystals. Strain is manifest in Raman spectra through changes in peak position and bandwidth. We present examples of the identification of strain in crystals of several technologically important materials.

Published in September 2019 issue

Click here to read this article.

Molecular Spectroscopy Workbench

The Effect of Microscope Objectives on the Raman Spectra of Crystals

The Raman spectra of a particular face of a single crystal can be significantly different if acquired with different microscope objectives. The purpose of this installment of “Molecular Spectroscopy Workbench” is to inform and educate users of micro-Raman instrumentation of the effect of the microscope objective on the Raman spectra of crystals. Furthermore, we explain the underlying physics of changes in relative intensity and even peak position of certain Raman bands depending on the microscope objective used to acquire the spectrum. Changes in peak position are attributed to phonon directional dispersion sampled through wide-angle microscope objectives with different numerical apertures.

Published in  September 2017  issue

Click here to read this article.


Workbench - Carotenoids

Carotenoids—Their Resonance Raman Spectra and How They Can Be Helpful in haracterizing a Number of Biological Systems

Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidants. Because the resonance Raman spectrum varies with subtle chemical changes on the functional side groups, the spectra of carotenoids have been used for identification and characterization. This installment of “Molecular Spectroscopy Workbench” summarizes the spectroscopy of these materials and why it can be useful when studying them.

Published in  June 2017  issue

Click here to read this article.


workbench 2017

Why Are the Raman Spectra of Crystalline and Amorphous Solids Different?

The Raman spectra of crystalline and amorphous solids of the same chemical composition can be significantly different primarily because of the presence or absence of spatial order and longrange translational symmetry, respectively.

Published in  March 2017  issue

Click here to read this article.


workbench articles 2017

Raman Polarization Measurements: Keeping Track of the Instrumental Components’ Behavior

Controlling the orientation of the laser and Raman polarization relative to the sample orientation can provide a wealth of information in the Raman spectrum that would be difficult to achieve by other methods. Presentation of the spectra makes these effects appear straightforward, but because of multiple instrumental factors, and experimental design, it is easy to produce erroneous results. This column is going to explain what instrumental components affect the polarization effects that are observed, and how the sample setup itself affects the Raman signal.

Published in February 2017 issue

Click here to read this article.

Workbench articles 2016

Raman Thermometry

Raman spectroscopy can be used to determine the temperature of a material when other more direct means are either impractical or not possible.

Published in December 2016 issue

Click here to read this article.


Characterizing Modified Celluloses Using Raman Spectroscopy

Characterizing Modified Celluloses Using Raman Spectroscopy

Raman spectra of celluloses modified for use in the pharmaceutical, food, and materials industries are compared and analyzed, with the goal of determining spectroscopic features that can be of use in aiding in the determination of physical and chemical properties.

Published in November 2016 issue

Click here to read this article.


Tip-enhanced Raman spectroscopy, or TERS

TERS—Ready or Not?

Tip-enhanced Raman spectroscopy, or TERS, integrates scanning probe microscopy (SPM) for nano-scale imaging with confocal Raman spectroscopy for chemical characterization. Challenges with tip quality, optical alignment, consistency and speed, however, have made the technique difficult and complex. New instrumentation is addressing these challenges, allowing TERS to migrate from pure research to routine laboratory analysis. These systems provide correlated nano-scale Raman imaging, enabling scientists to visualize, chemically characterize and implement change, even at the single-molecule level. 

Published in September 2016 issue

Click here to read this article.


Photoluminescence SpectroscopyUsing a Raman Spectrometer

Photoluminescence Spectroscopy Using a Raman Spectrometer

Photoluminescence can provide information about the composition and solid-state structure of a material. The high spectral resolution of a Raman spectrometer can be useful in performing photoluminescence spectroscopy of solid-state materials, particularly when the emission spectra consist of narrow bands or even lines. Having the capability to perform photoluminescence and Raman spectroscopies simultaneously with the same instrument is advantageous, especially when studying two-dimensional (2D) crystals. When used to perform photoluminescence spectroscopy, the Raman spectrometer becomes two instruments in one.

Published in September 2016 issue

Click here to read this article.


Selecting an Excitation Wavelength for Raman Spectroscopy

Selecting an Excitation Wavelength for Raman Spectroscopy

Were it not for the problem of photoluminescence, only one laser excitation wavelength would be necessary to perform Raman spectroscopy. Here, we examine the problem of photoluminescence from the material being analyzed and the substrate on which it is supported. We describe how to select an excitation wavelength that does not generate photoluminescence, reduces the noise level, and yields a Raman spectrum with a superior signal-to-noise ratio. Furthermore, we discuss the phenomenon of resonance Raman spectroscopy and the effect that laser excitation wavelength has on the Raman spectrum.

Published in March 2016 issue

Click here to read this article.


Raman Mapping of Spectrally Non-Well-Behaved Species

Raman Mapping of Spectrally Non-Well-Behaved Species

The use of Raman spectroscopy to produce material images whose contrast is derived from chemical or crystallographic species has been quite useful since the introduction of the Raman microscope in 1976, but particularly with the more recent development of more-sensitive and easier-to-use instruments. When the various species in the field of view have spectra with nonoverlapping analytical bands, simple univariate analysis can provide good images. When overlapping bands are present, multivariate techniques, especially multivariate curve resolution (MCR), have been successfully applied. However, there are cases where even MCR results may be problematic. In this installment, we look at some maps of a ceramic composite containing silicon carbide, silicon, boron carbide, and carbon, where each of these species has nonunique spectra to see what type of results flexible software can produce. What is the goal in this type of exercise? For some of us, creating images is like a teenager’s computer game. But really what we are trying to do is to extract information about a sample from its Raman image. A beautiful rendition is nice, but it must yield information. The following installment shows how Raman maps can provide useful information about a sample.

Published in February 2016 issue

Click here to read this article.

The Correlation Method for the Determination of Spectroscopically Active Vibrational Modes in Crystals

The Correlation Method for the Determination of Spectroscopically Active Vibrational Modes in Crystals

The application of vibrational selection rules is usually taught with respect to the vibrational motions of individual molecules. However, many of the materials studied by infrared or Raman spectroscopy are solids and even single crystals. Furthermore, some materials such as covalent or ionic solids have no molecular species associated with them. Consequently, there is a need to understand the application of group theory for the determination of spectro- scopically active vibrational modes of crystals. The correlation method is ideal for that purpose.

Published in December 2015 issue

Click here to read this article.


SERS: An Update of Progress Made

SERS: An Update of Progress Made

This column is a mini survey of progress that has been made in the area of surface enhancement over the last few years since my previous column on surface-enhanced Raman scattering (SERS) in 2008. The potential of SERS to provide signals of analytes at very low concentrations continues to beckon the analytical chemist. What the last few years has produced is a body of work describing the role of the plasmonic properties of metals, based on their geometrical and electronic properties, in enhancing the signals. As this field matures, we foresee production of surface-enhancing films and particles, engineered to provide large enhancements at selected wavelengths that will provide reproducible Raman signals for applications in areas such as environmental and biomedical studies.

Published in November 2015 issue

Click here to read this article.


Raman Spectroscopy and Imaging of Low-Energy Phonons

Raman Spectroscopy and Imaging of Low-Energy Phonons

Raman bands in the low-energy region of the spectrum of crystals are attributed to so-called external lattice vibrational modes. The Raman bands from these external vibrational modes (low-energy phonons) are very sensitive to crystal structure and orientation with respect to the incident laser polarization and to molecular interactions within the crystal. The low-energy vibrational modes of many organic molecular crystals have very high Raman scattering cross-sections. Raman spectra and images of low-energy phonons in two-dimensional (2D) crystals such as few-layer MoS2 reveal spatial variations in the solid-state structure that are not evident in the higher-energy bands. 

Published in September 2015 issue

Click here to read this article.


Current Uses of Raman Microscopy in Biomedical Studies

Current Uses of Raman Microscopy in Biomedical Studies

There is growing interest in using Raman as a spectroscopic probe of biological systems based on its high information content, its compatibility with an aqueous environment, and the spatial resolution that is consistent with physical optics (as good as ~0.5 μm). Sampling hardware innovations in recent

Published in June 2015 issue

Click here to read this article.


Resonance Raman and Photoluminescence Spectroscopy and Imaging of Few-Layer MoS2

Resonance Raman and Photoluminescence Spectroscopy and Imaging of Few-Layer MoS2

Resonance and off-resonance Raman spectroscopy and imaging are used to examine the spatial variation of the solid-state structure and electronic character of few-layer MoS2 flakes. Simultaneous acquisition of photoluminescence spectra with the Raman scattering provides complementary ways of rendering Raman and photoluminescence spectral images of thin-film MoS2.

Published in March 2015 issue

Click here to read this article.


Multiparticle Analysis by Raman Microscopy

Multiparticle Analysis by Raman Microscopy

There are multiple circumstances where characterization of a collection of particles has value to analysts. In some environments, materials are plagued by particulate contamination that impacts product quality. In the case of small-molecule pharmaceuticals, the solid form of the active pharmaceutical ingredient has to be controlled because of its impact on stability, bioavailability, and intellectual property protection. Raman analysis of relatively large areas with sparsely dispersed particles is now integrated with particle statistics. Results of some simple studies are shown in this column.

Published in February 2015 issue

Click here to read this article.


Raman Spectroscopy and Microscopy Enable Life Science Discoveries

Raman Spectroscopy and Microscopy Enable Life Science Discoveries

The first article in this two-part series looked at Raman spectroscopy applications in tumor surgery, endoscopy and bacterial identification. This second part examines applications in cell sorting, laser trapping, biology probing and more.

Published in BioPhotonics, February/March 2015 issue

Click here to read this article.


Raman Spectroscopy and Microscopy: Solving Outstanding Problems in the Life Sciences

Raman Spectroscopy and Microscopy: Solving Outstanding Problems in the Life Sciences

This first article in a two-part series will examine Raman spectroscopy applications in tumor surgery, endoscopy, bacterial identification and more. The second part will cover applications in cell sorting, laser trapping and probing biology.

Published in BioPhotonics, January 2015 issue

Click here to read this article.

Three-Dimensional Raman Imaging of Ion-Exchanged Waveguides

Three-Dimensional Raman Imaging of Ion-Exchanged Waveguides

Segmented channel waveguides have been fabricated in single-crystal KTiOPO4 through a topotactic process of partial cation exchange. The ion-exchanged waveguides maintain the high nonlinear susceptibility of KTiOPO4 to function as frequency doubling laser light sources. We applied three-dimensional Raman imaging to understand and characterize the changes to the chemical bonding and crystalline structure as well as measure the volumetric structure of waveguide segments.

Published in Spectroscopy, December 2014

Click here to read this article.


Raman Spectra of Metal Oxides

Raman Spectra of Metal Oxides

Metal oxides often occur in crystals where there are no molecular units. In contrast to Raman analysis of organic compounds in which there are molecular vibrating units with functional subunits, many of whose vibrations are isolated from the remainder of the molecule, the analysis of spectra of oxides requires understanding how atoms move in crystal lattices. These oxides occur in diverse materials such as paint and ceramic pigments, corrosion films, catalysts, and minerals. This column installment attempts to introduce analysts who often work with organic materials to the concepts that need to be understood in analyzing these materials.

Published in Spectroscopy, October 2014

Click here to read this article.


Headspace Raman Spectroscopy

Headspace Raman Spectroscopy

We examine vapor-phase Raman spectroscopy through the acquisition of spectra from gas molecules confined to the headspace of sealed containers. Studying the Raman spectra of the liquid and vapor phases of compounds with different functional groups, degrees of hydrogen bonding, and polarity provides insight into the energetics of molecular interactions.

Published in Spectroscopy, September 2014

Click here to read this article.


Raman Microscopy for Detecting Counterfeit Drugs — A Study of the Tablets Versus the Packaging

Raman Microscopy for Detecting Counterfeit Drugs — A Study of the Tablets Versus the Packaging

With the increasing proliferation of counterfeit drug products, there is an incentive to screen drugs for legitimacy. One method is to examine the tablet itself, which is usually a destructive operation. Another method that has been explored is to characterize the packaging, which enables nondestructive screening of the product. Raman microscopy has been found to be a useful tool, and it is often the tool of choice for these measurements.

Published in Spectroscopy, June 2014

Click here to read this article.


High-Speed TERS Imaging: The Latest Achievements in nano-Raman Spectroscopy

High-Speed TERS Imaging: The Latest Achievements in nano-Raman Spectroscopy

This article presents developments in tip-enhanced Raman spectroscopy (TERS) that make possible nanoscale imaging of chemical and physical properties of graphene and other carbon species: Advances in near-field optical probes now provide reliable nanoscale spectroscopy solutions for academic and industrial researchers.

Published in Spectroscopy, June 2014

Click here to read this article.


Practical Group Theory and Raman Spectroscopy, Part II: Application of Polarization

Practical Group Theory and Raman Spectroscopy, Part II: Application of Polarization

In this second installment of a two-part series we present polarized Raman spectra and discuss the association of the symmetry species of the normal vibrational mode and the depolarization ratio of Raman scattering. We discuss those aspects of molecular symmetry and Raman polarization rules that can be applied with normal Raman instrumentation. Materials include liquids, single crystals, and polycrystalline compounds.

Published in Spectroscopy, March 2014

Click here to read this article.


Practical Group Theory and Raman Spectroscopy, Part I: Normal Vibrational Modes

Practical Group Theory and Raman Spectroscopy, Part I: Normal Vibrational Modes

Group theory is an important component for understanding the fundamentals of vibrational spectroscopy. The molecular or solid state symmetry of a material in conjunction with group theory form the basis of the selection rules for infrared absorption and Raman scattering. Here we investigate, in a two-part series, the application of group theory for practical use in laboratory vibrational spectroscopy.

Published in Spectroscopy, February 2014

Click here to read this article.

如何为拉曼光谱仪选择合适的光栅

对于特定的应用领域来说,拉曼光谱仪的性能主要取决于灵敏度和光谱分辨率。其中,灵敏度将决定获得特定信噪比的光谱所需时间。

 

刊登于201310月的《Spectroscopy》期刊

点击这里 阅读原文


硅结构的拉曼成像

本文中我们将讨论什么是拉曼成像以及如何得到拉曼成像。拉曼成像实际上是对高光谱数据的处理和转换得到的结果。

刊登于20139月的《Spectroscopy》期刊

点击这里 阅读原文


共振拉曼光谱:是敌是友?

激光光子能量与某电子跃迁能量相等或相近时,能够极大地增强拉曼信号。有时候,信号能够增强6个数量级。当然,前提是这个跃迁不以发光的形式释放。

刊登于20136月的《Spectroscopy》期刊

点击这里 阅读原文


Classical or Transmission Raman, SERS or TERS: Which Raman Spectroscopy Technique Is Right for You?

Classical or Transmission Raman, SERS or TERS: Which Raman Spectroscopy Technique Is Right for You?

This article explains different Raman techniques are compared with respect to their main field of applications, possibilities, advantages, difficulties, and limits.

Published in Spectroscopy, June 2013

Click here to read this article.


如何将拉曼光谱如何应用于油页岩探测

本文将会介绍显微拉曼光谱在油页岩探测方面的应用实例及相关内容。

 

 

刊登于20133月的《Spectroscopy》期刊

点击这里 阅读原文


有机纤维中分子取向的显微拉曼分析

无论是人造或是天然的有机高分子,在形成纤维的过程中,其分子都会进行一定排序,因而取向性在纤维中普遍存在。通过对纤维进行的大量研究证明,拉曼光谱非常适用于取向研究,并可对其进行量化。

 

刊登于20132月的《Spectroscopy》期刊

点击这里 阅读原文 


从微观到宏观-拉曼光谱在太阳能硅片研究方面的应用

文章中解释了如何利用拉曼光谱对太阳能硅板材料进行应力分析。

 

发表于2012Intech《Advanced Aspects of Spectroscopy 》一书

点击这里 阅读原文


光谱图像的多变量数据处理:丑的、坏的和真实的

本文介绍了“漂亮的”与“真实的”拉曼化学图像之间的区别,告诉我们如何获得真实而又漂亮的拉曼化学图像。

 

刊登于2007年八月的《Spectroscopy》期刊。

 

本文介绍了“漂亮的”与“真实的”拉曼化学图像之间的区别,告诉我们如何获得真实而又漂亮的拉曼化学图像。

 

刊登于2007年八月的《Spectroscopy》期刊。

 

点击这里  阅读原文


拉曼成像:卓越空间分辨率

本文评述了滴在硅表面的聚苯乙烯使用拉曼成像和图像处理得到的化学图像,讨论了物镜对最终图像的质量的影响,特别是其放大倍数和数值孔径的作用,以及mapping时的步长。.

2006年刊登于《Spectroscopy》 supplement Raman

 点击此处 阅读全文.


光谱成像在生命科学的应用 - -不仅仅是一副好图片

理解活体组织内发生的复杂过程一直是科学家追求的主要目标,小到微观组织如细菌病毒,大到人类。这篇文章表明显微成像是生物科学研究的一个关键技术。

2005年刊登于 《Spectroscopy Europe Life Science 》August/September

点击此处 阅读全文.


材料分析中的光谱应用

 

拉曼和EDXRF化学成像在配方工艺研发和质量控制中的应用,镁和钙化合物是常见的药物配方中的组分.

光谱成像可以为配方工艺提供全面的信息。这篇文章比较了2种成像技术的对比--EDXRF(能量色散X射线荧光)和拉曼。

2005年6月刊登于 Spectroscopy

点击此处 点击此处.


生物医药成像和分析

朝精细的化学图像迈进

有很多测量生物医药样品的分析和成像技术,样品本身覆盖范围很宽,且形式各异,如单细胞,组织,晶体,或混合配方。为研究这类样品,使用了很多技术,如荧光光谱,近红外成像,AFM和SEM等。.

2005年刊登于 《 European Biopharmaceutical Review》春季刊

点击此处 阅读全文.


超凡的拉曼光谱

开拓工艺过程的新视野

光纤探针和易用性使得拉曼光谱在从制药到石化的众多工业的监测工艺控制过程很有吸引力。作者讲述了拉曼效应,讨论了系统和检测基本知识。

Published in Optics & Photonics News, June 05

点击此处 阅读全文.


细胞成像的新方法

化学信息和空间信息的结合

有很多种方法用于研究细胞结构,如光学显微镜,共焦激光扫描显微镜,扫描电镜和原子力显微镜等。这些技术提供了细胞单详细图像,但是缺乏化学和组成特征。幸运的是,光谱技术可以弥补这个缺憾,特别是显微拉曼光谱很快实现了从微米级探究细胞生物化学的愿望。

Published in BIOforum Europe, April 2005

点击此处 阅读全文.


显微光谱-在岩石形成过程的研究中大放异彩

虽然科学家有很多种成像方法,但是得到的往往是虚拟或地形学上的信息。他们没有提供材料的真实的组成。显微光谱技术,如拉曼和X射线荧光可以填补这个空白,可以建立在材料组分上的精细图像。

 Published in Spectroscopy Europe, June 2005

点击此处 阅读全文