Raman Spectroscopy

In this paper, we examine the relative performance of 532 and 785 nm portable Raman systems, as well as demonstrate an automated analytical methodology applicable for carbon nanotube (CNT) characterization and quality control applications. Both 532 and 785 nm Raman spectra were used to directly analyze and compare important CNT structural parameters and properties including CNT diameters, diameter distributions, CNT structural quality (% of defects), CNT types, and other properties. The data indicate advantages in a number of areas for using 532 versus 785 nm excitation for CNT Raman measurements.

This article verified the Brill transition in nylon 6,6 by Raman spectroscopy through heating and cooling processes of the sample. When nylon is heated at around 160 C a crystalline phase transition occurs from a triclinic structure at room temperature to a pseudohexagonal structure above that temperature. This phase transition is known as the Brill Transition. With temperature-dependent Raman scattering measurements, it was possible to determine the vibrational behavior of nylon 6,6 during the Brill transition, and consequently to identify the main Raman bands associated with the Brill transition.

Raman spectroscopy is particularly useful for identification of contaminant materials in pharmaceuticals because it can very clearly and nondestructively identify materials. Raman spectroscopy can be used to identify foreign matter on tablets as well as the individual tablet materials to confirm the material’s legitimacy. For injectable drug vials, Raman spectroscopy can be used with microscopy to count, size, and identify particulate contamination found in such vials. Spectral interpretation is key to the value of Raman spectroscopy, and it is important for accuracy of identification not to simply rely on library match values.

Cosmetic preparations are common consumer products that consist of various organic and inorganic materials. In this paper, a method for the identification and spatial discrimination of the components in eye shadow samples using laser Raman microspectroscopy is described. The use of a multivariate curve resolution (MCR) is utilized during the analysis of the cosmetic preparation mapping data to develop the spatial discrimination information presented within this note.

Analytical quality control (AQC) is an established application of Raman spectroscopy in many industrial fields. The extension of Raman spectroscopy as an AQC method in hospital environments imparts the benefits of a noninvasive and nondestructive analysis. The literature in using Raman spectroscopy as an AQC method for chemotherapy preparation and anesthesia gas monitoring is reviewed. Future applications in tissue engineering and incorporating new Raman techniques into AQC are also discussed.

Recent advances in Raman instrumentation have resulted in the development of easy-to-use and efficient handheld Raman analyzers. Most of the commercially available handheld Raman devices utilize 785 or 1064 nm excitation. This paper directly demonstrates the performance of 532 nm handheld Raman (versus 785 and 1064 nm) for the analysis of biopharmaceuticals for structure and counterfeit testing as well as explosive detection (TSA screening and CSI applications). The results presented here will contribute to recognition of 532 nm Raman excitation as a highly attractive option for a rapid “in-place” analysis in the field.

Aligned semiconducting single-walled carbon nanotubes (s-SWCNTs) are expected to outperform silicon as the next generation of integrated circuits. Greater utilization of polarized Raman spectroscopy is proving beneficial for efficient characterization of alignment in CNT films. Here, we present the results of how polarized Raman imaging can be used to effectively characterize alignment in large regions of aligned s-SWCNT films.

Colin Campbell discusses his work applying SERS to biomedical applications.

Our annual review of products introduced at Pittcon or during the previous year, broken down by the following categories: accessories, atomic spectroscopy, components, imaging, mass spectrometry, mid-IR, NIR, NMR, Raman, software, UV-vis, and X-ray.

In recent years, Raman spectroscopy has been applied to process monitoring and control applications in a wide range of application fields, including bioprocessing, pharmaceuticals, food, oil and gas, and oceanography. Brian Marquardt, cofounder and CEO of MarqMetrix, Inc., and director and senior principal engineer with the Center for Process Analysis and Control in the Applied Physics Laboratory at the University of Washington, has more than 15 years of experience with such applications and recently spoke with us about his research.

Matthew Baker, a senior lecturer in chemistry at the University of Strathclyde, in Glasgow, has won the inaugural Emerging Leader in Molecular Spectroscopy Award, which is sponsored by Spectroscopy magazine. This new annual award recognizes the achievements and aspirations of a talented young molecular spectroscopist, selected by an independent scientific committee. The award will be presented to Baker at the SciX 2016 conference in September, where he will give a plenary lecture and be honored in an award symposium.

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. Selecting 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.

The use of Raman spectroscopy to produce material images whose contrast is derived from chemical or crystallographic species has been seen as quite useful since the introduction of the Raman microscope in 1976, but particularly, more recently, with the development of more sensitive and easier-to-use instruments. When the various species in the field of view have spectra with non-overlapping analytical bands, simple univariate analysis can provide good images. When overlapping bands are present, multivariate techniques, especially MCR (Multivariate Curve Resolution), have been successfully applied. However, there are cases where even MCR results may be problematic. We will look at some maps of a ceramic composite containing SiC, Si, B4C, and Carbon, where each of these species has non-unique 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 will show how Raman maps can provide useful information on a sample.

Crystallinity is an important factor when producing pharmaceuticals as it directly affects the bioavailability of the drug. Low frequency Raman spectroscopy offers some advantages to the detection and analysis of crystallinity in pharmaceutical samples. Here the experimental requirements for low frequency Raman measurements are described. The application to the study of crystallinity with a number of examples is discussed and the advantages and limitations of this technique are highlighted and compared with other techniques.

In this paper, we demonstrate a sensitive surface-enhanced Raman spectroscopy (SERS) substrate for trace dimethoate detection. The substrate is composed of Ag nanoparticle/probe/smooth Au film stack configuration. The nanogap formed by an Ag nanoparticle and a macroscopically flat Au film is one kind of “hot site” which will dramatically increase the total “hot spots” number.

Imaging techniques using vibrational spectroscopy, mass spectrometry (MS), and atomic force microscopy have all been advancing and gaining momentum in recent years. There is great potential power in these imaging techniques, particularly in the biomedical field. Thomas Bocklitz of at the Friedrich-Schiller-University Jena is working to better harness the power of these techniques by combining them.

Attend any conference covering vibrational spectroscopy, and you will likely hear numerous talks about developments in tip enhanced Raman scattering (TERS) and surface-enhanced Raman scattering (SERS). Both approaches hold exciting promise, but face significant challenges as well. We asked a panel of Raman experts about the current and future role of these two approaches.

The application note explains how the Raman Spectroscopy can be helpful in the analysis of cathodes and anodes in Li-ion batteries.

Statistical and morphological analysis of particles on a filter has been complemented by chemical analysis based on Raman spectroscopy using the ParticleFinder tool, allowing further insight into the particle composition and its origin within a production line.

Evaluation of the discrimination power of Raman spectroscopy in decreasing turnaround time in clinical diagnosis, when analyzing microcolonies from nine bacterial and one yeast species directly on solid culture medium after a shortened incubation time.

Recent reports of the successful use of Raman spectroscopy for important biomedical applications are quite exciting. These applications include imaging for disease diagnosis, including significant improvements for endoscopic probes, and identification of microorganisms. But is it truly practical and feasible to implement Raman technologies in a clinical environment?

Imaging techniques using vibrational spectroscopy, mass spectrometry (MS), and atomic force microscopy have all been advancing and gaining momentum in recent years. There is great potential power in these imaging techniques, particularly in the biomedical field. Thomas Bocklitz of at the Friedrich-Schiller-University Jena is working to better harness the power of these techniques by combining them.

In honor of Spectroscopy's celebration of 30 years covering the latest developments in materials analysis, we asked a panel of experts to assess the current state of the art of Raman spectroscopy and to try to predict how the technology will develop in the future.

Locate particles, generate size/shape statistics, select particles based on size/shape, and acquire Raman spectra. Easily locate and identify particulate matter, including pharmaceutical materials, trace forensic evidence, geological rock/mineral particles, and airborne contaminants trapped on filters

Demonstrates uRaman from TechnoSpex Pte. Ltd. is a promising instrument to determine the quality of the transferred single layered graphene on a 300-nm silicon dioxide (SiO2) substrate.

 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.

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.

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

Raman microscopy is a promising technique for visualizing the distribution of molecules in cells. However, along with the benefits come challenges. This interview with Katsumasa Fujita, an associate professor in the Department of Applied Physics at Osaka University in Osaka, Japan, discusses his use of this technique for the imaging of live cells.