In the shadow of the world's tallest church, more than 100 scientists met in Ulm at the end of September for the 14th Confocal Raman Imaging Symposium. The lectures thoroughly documented how modern Raman microscopy contributes to gaining new insights into widely varied scientific questions.
In 11 invited lectures three short presentations, the speakers presented new and interesting applications of Raman microscopy to answer questions from life sciences, materials science, geoscience and environmental science.
WITec’s solution for correlative Raman-SEM imaging is now available for ZEISS Sigma 300, a field emission scanning electron microscope (FE-SEM). With this jointly-developed system, WITec and ZEISS have furthered their collaboration to provide a fully-integrated instrument available as an OEM product through ZEISS that features a standard, unmodified vacuum chamber and SEM column along with a complete confocal Raman microscope and spectrometer. It expands the range of choices available to the researcher and incorporates generations of experience in Raman spectroscopic imaging and advanced structural analysis.
RISE stands for Raman Imaging and Scanning Electron microscopy. The seamless combination of the two techniques offers a distinct advantage when investigating samples, improves ease-of-use and accelerates experimental workflow. The research-grade optical microscope capability integral to every WITec microscope also helps researchers survey their sample and quickly locate areas of interest. Both the objective and sample stage required for Raman microscopy are placed within the SEM’s vacuum chamber and can therefore remain under vacuum for all measurements; the sample is simply transferred between the Raman and SEM measuring positions using the stage of ZEISS Sigma 300. The configuration allows the Raman microscope to be attached through a standard port of the SEM. The correlation of data and control of Raman measurements are carried out through WITec’s Suite FIVE software, which features a new operating concept with an intuitive interface, automated components and sophisticated software and data analysis routines.
According to Dr. Olaf Hollricher, Co-founder and Director of R&D at WITec, "Our Raman technology can visualize the distribution of chemical species within a sample, and do it quickly. Combine that with the structural resolution of SEM and you get a properly comprehensive understanding of a sample. It’s a powerful instrument that’s intuitive as well."
ZEISS Sigma 300 provides exceptional resolution, contrast and brightness at a price point accessible to most laboratories and working groups. With its Gemini electron optics, including an Inlens secondary electron detector tailored for high-resolution surface-sensitive imaging, the instrument is inherently flexible and precise. FE-SEMs enable structural characterization of particles, surfaces and nanostructures and the ZEISS Sigma series 4-step automated workflow allows for increased productivity.
WITec’s modular Raman technology allows 3D chemical characterization by combining a high-resolution confocal microscope with a high-throughput Raman spectrometer. Raman imaging, pioneered by WITec, is a label-free and non-destructive technique capable of identifying and imaging the molecular composition of a sample, making it an ideal complement to scanning electron microscopy.
"Comprehensive characterization is essential throughout many scientific fields such as battery research, geology and life sciences. The integration of RISE microscopy in our correlative portfolio aims at delivering cutting edge technology to these and many other areas of research. We are very happy that with WITec we have a partner that shares our ambition to drive scientific advancement," says Dr. Michael Rauscher, Head of Business Sector Materials Sciences at ZEISS Microscopy.
"RISE really fulfills the promise of correlative microscopy," says Dr. Philippe Ayasse, Project Manager for RISE microscopy at WITec. “It gives the user the strengths of Raman and SEM without compromise, all consolidated in one easy to use instrument.”
All the functions of the respective stand-alone SEM and Raman systems are preserved when combined. Switching between measurement modes is accomplished quickly and easily through the software, which also facilitates the transformation of Raman spectroscopic data into an image which can then be overlaid onto the SEM image to produce a RISE image. This correlative approach can greatly benefit researchers in nanotechnology, life sciences, geosciences, pharmaceutics, materials research and many other fields of application.
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From nearly 60 submissions for the 2017 WITec Paper Award, our jury selected the three best publications. They were written by scientists from Ireland, Portugal and Germany who used WITec correlative confocal Raman microscopes to study transition metal dichalcogenides, textile fibers and cement. These papers show in remarkable detail how information on the chemical and structural composition of a material, obtained through this non-destructive technique, can lead to a more comprehensive understanding of a wide range of materials.
The Gold Paper Award is conferred upon Maria O’Brien from Trinity College in Dublin (Ireland) for mapping low-frequency Raman modes of four transition metal dichalcogenides (TMDCs): MoS2, MoSe2, WS2 and WSe2. Together with Niall McEvoy, Damien Hanlon, Toby Hallam, Jonathan Coleman and Georg Duesberg, she used the Raman modes for in-plane and out-of-plane vibrations whose intensities depend on the thickness and the stacking order of the molecules’ layers. The study has shown that the low-frequency Raman modes of these materials reveal additional information compared to conventional Raman modes. The scientists are convinced: “This study presents a major stepping stone in the fundamental understanding of layered materials as mapping the low-frequency modes allows the quality, symmetry, stacking configuration and layer number of 2D materials to be probed over large areas.” They suggest using low-frequency Raman mapping for the analysis of TMDCs that show no significant changes correlated to layer numbers in the high-frequency regions of their Raman spectra.
The Silver Paper Award is given to Helena Nogueira from the University of Aveiro (Portugal). She and her co-authors Sara Fateixa, Manon Wilhelm and Tito Trindade used three-dimensional Raman imaging and surface enhanced Raman scattering (SERS) to monitor the dyeing process of linen textile fibers with methylene blue. This dye is most commonly used for blue coloring and was applied by various procedures. The scientists also visualized how the silver nanoparticles that give textiles antimicrobial properties are distributed along and within the linen fibers. The authors conclude that regarding textile production “… Raman imaging and SERS are valuable assets that complement or eventually provide unique characterization data.”
The Bronze Paper Award goes to Jonas Higl from the University of Ulm (Germany) for a Raman study on hydrating of cementitious materials. With his colleagues Marcus Köhler and Mika Lindén, he used confocal Raman microscopy to document which structures and molecules are formed during the complex process of hydrating C3S clinker. To the knowledge of the authors this study was the first one published using Raman imaging to study hydrating of cement.
The annual awards recognize outstanding scientific work published the preceding year that employed a WITec device as part of its experimental setup. The evaluation criteria include the significance of the results for the scientific community and the originality of the techniques used.
Winning Publications of the 2017 WITec Paper Award
GOLD: Mapping of low-frequency Raman modes in CVD-grown transition metal dichalcogenides: layer number, stacking orientation and resonant effects. Scientific Reports 2016, 6, 19476.
SILVER: SERS and Raman imaging as a new tool to monitor dyeing on textile fibres. Journal of Raman Spectroscopy 2016, 47, 1239. DOI 10.1002/jrs.4947
BRONZE: Confocal Raman microscopy as a non-destructive tool to study microstructure of hydrating cementitious materials. Cement and Concrete Research 2016, 88, 136.
Paper Award 2018
WITec recently announced the 2018 WITec Paper Award competition for research articles published in 2017. Scientists from all fields of application in both academia and industry are invited to submit their publications featuring results acquired with a WITec instrument to firstname.lastname@example.org. The deadline for submissions is January 31st, 2018.
The Raman imaging company WITec celebrates its 20th Anniversary. It was founded in 1997 as a 3-person spin-off from the Physics Department of the University of Ulm and has grown into a company of 60 employees including the Ulm headquarters and its branch offices in Spain, China, Japan, Singapore and the USA. As reflected in the company’s maxim "Focus Innovations" WITec’s success is based on introducing new technologies and a commitment to maintaining customer satisfaction with high-quality, flexible and empowering products.
Through the past 20 years WITec has established itself as a world-renowned manufacturer of confocal Raman imaging systems that embody the notion of German quality. Even WITec’s first production instrument, a Scanning Near-field Optical Microscope (SNOM/NSOM), continues to provide dependable, effective service. Dr. Julio Soares, Senior Research Scientist at the Frederick Seitz Materials Research Laboratory, University of Illinois in Urbana-Champaign, says: “We are proud to be part of the history of WITec instruments by housing the very first of the WITec NSOM to be sold and that our laboratory helped on the further development of that instrument at the time. I think the fact the serial number one instrument is still running without hardly needing any technical support is an achievement in itself.”
Dr. Olaf Hollricher, Director of Research & Development at WITec, says: “Remembering the history of Raman imaging in general and that of WITec in particular, the terms innovation and development come to my mind first. The past 20 years have brought incredible technological advances in Raman analysis. And this development has affected the analysis of many materials, ranging from semiconductors to textile fibers to cancer cells. We always pushed on development of new concepts of Raman imaging and techniques, for which we were recognized with numerous awards.”
From the beginning, WITec’s Raman microscopes have always been extremely fast, with integration times in the range of milliseconds per pixel. Back in the late 90s, integration times used to be one minute per pixel – thus WITec customers could measure far quicker than ever before. All WITec Raman imaging systems use the spectral information of a sample to produce an image that visualizes its chemical composition and structure. WITec was also the first to offer combined microscopes that allow for imaging of a sample with several microscopy techniques that are integrated into one instrument. WITec’s latest innovation in correlative Raman imaging instruments is the Raman Imaging – Scanning Electron (RISE) microscope that has now captured the attention of many in the SEM community.
Dr. Joachim Koenen, Managing Director, says: “WITec’s success over the past 20 years is certainly satisfying. We have developed many new Raman imaging systems and techniques that we’re proud of. Sharing and exchanging our know-how with scientific and industrial customers for so many years has been really exciting. Still, we have many ideas for the technical improvement of Raman imaging that have yet to be fully developed and implemented. So I’m eagerly looking forward to the future of working with our customers and the WITec family.”
Innovations in Profilometer-guided Raman Imaging
WITec, the inventor of topographic Raman imaging, has presented at Pittcon 2017 in Chicago the next generation of its patented TrueSurface optical profilometer. The combination of surface analysis and Raman spectral acquisition enables topographic Raman imaging on rough and uneven samples. One-pass simultaneous operation makes 3D Raman chemical characterization easier and faster than ever before.
We have documented the TrueSurface in a video.
“WITec established Raman topographic imaging with TrueSurface. We then continued to innovate, leveraging the inherent strengths of our systems,” says Dr. Olaf Hollricher, Managing Director of R&D at WITec. “The overwhelmingly positive feedback from our customers confirms that chemical 3D surface analysis with TrueSurface is a successful concept with an enthusiastic following in academia and industry.”
With the TrueSurface option, Raman spectra are acquired from precisely along a surface, or at a set, user-defined distance from a surface. This makes the distribution of chemical components within the sample visible in three dimensions. Rough, inclined or irregularly-shaped samples can be investigated with the same ease as standard samples. The requirements of sample preparation can therefore be drastically reduced.
As the TrueSurface sensor actively monitors and maintains a set distance between the objective and sample surface, its closed-loop operation can compensate for any variations during measurements with long integration times. This keeps the measurement area in focus at all times and produces sharp chemical Raman images with sub-micrometer resolution.
Investigations on pharmaceutical tablet coatings, geological samples, composite emulsions, complex semiconductor structures and many other applications can benefit from the ease of use, accelerated workflow and methodological advantages provided by the new TrueSurface.
“TrueSurface is for everybody who wants to just take a sample, as it is, and put it under a microscope for chemical analysis,” explains Dr. Joachim Koenen, Managing Director at WITec. "Also, the combination of confocal Raman imaging and optical profilometry provides additional information on the chemical distribution of the sample components that are of great benefit to our customers."