In this interview, AZoMaterials speaks with Sudhir Dahal, Product Manager for Research Raman Products at Thermo Fisher Scientific, about the fundamentals of Raman spectroscopy and its growing role in solving real-world analytical challenges across materials science, pharmaceuticals, polymers, and process monitoring applications.
Can you please describe your role at Thermo Fisher Scientific?
My role focuses on bringing advanced Raman spectroscopy and microscopy solutions to market for demanding pharmaceutical and industrial applications. I work closely with customers and researchers to help them apply Raman technologies to solve complex analytical problems, whether that involves material identification, process monitoring, quality control, or advanced materials research.
What makes Raman spectroscopy such a powerful analytical technique?
Raman spectroscopy is powerful because it provides highly specific molecular and structural information through the interaction of light with matter. Like many analytical techniques, it helps answer three essential questions: what the material is, how much of it is present, and where it is located.
What really differentiates Raman is that it delivers this information through molecular-level vibrational analysis. It is especially sensitive to molecular backbones and symmetric bonds, making it highly effective for distinguishing between very similar compounds and even polymorphs.
Another major advantage is that Raman is non-contact and non-destructive. Furthermore, measurements are often completed within seconds, and sample preparation is minimal. In many cases, samples can even be analyzed directly through transparent packaging such as glass or plastic.
Image Credit: Thermo Fisher Scientific - Vibrational Spectroscopy
How does Raman spectroscopy compare with FTIR?
Raman and FTIR are highly complementary techniques. FTIR is particularly strong at highlighting functional groups, while Raman excels at identifying molecular backbones and symmetric bonds.
When used together, they provide a much more complete understanding of a material. Raman is also especially useful in environments where FTIR may face limitations - such as aqueous systems - because water produces relatively weak Raman interference.
Additionally, Raman microscopy offers very high spatial resolution, allowing users to analyze areas as small as one micron and even perform depth profiling without physically sectioning samples.
Could you explain the basic working principle behind Raman spectroscopy?
At its core, Raman spectroscopy is a light scattering technique. A laser excites the sample, and the scattered light carries information about molecular vibrations.
The optical system includes several important components. The laser provides excitation; filters remove unwanted signals such as Rayleigh scattering; and a diffraction grating separates the scattered light into spectral components. Finally, a CCD detector captures the signal.
The resulting spectrum contains multiple layers of information: peak position relates to molecular structure; peak intensity correlates with concentration; peak width provides insight into crystallinity; and peak shifts can indicate stress or strain within a material.
Together, these parameters allow researchers to gain a comprehensive understanding of their samples.
Why is Raman spectroscopy particularly valuable for pharmaceutical applications?
Raman spectroscopy is extremely valuable in pharmaceutical manufacturing because it enables rapid, non-destructive quality control directly through sealed packaging.
For example, Raman measurements can be performed through glass vials during fill-finish processes with little or no sample preparation. A single measurement can provide both identification and quantification, which significantly reduces turnaround times compared to conventional analytical workflows.
This allows manufacturers to release batches within hours, rather than waiting days or weeks as with traditional testing methods.
Raman imaging is also valuable for analyzing pharmaceutical tablets. A tablet may visually appear completely uniform, but Raman imaging can reveal the spatial distribution of active ingredients and excipients such as caffeine, acetaminophen, or aspirin. This helps assess content uniformity, detect impurities, and better understand material structures.
How is Raman spectroscopy used in polymer and packaging analysis?
Raman is highly effective for analyzing multilayer packaging materials through depth profiling.
In one example, individual polymer layers such as nylon, EVOH, and PET can be identified without destroying the sample. This capability is extremely useful for reverse engineering, quality assurance, and material development.
Food packaging is a good example because multiple layers may be used to provide moisture barriers, strength, airtight sealing, or visual appeal. Raman allows all of these layers to be characterized without extensive sample preparation.
Why is Raman spectroscopy important in graphene research?
Graphene research is one of the most exciting areas for Raman spectroscopy because Raman is extremely sensitive to the structural properties of graphene and graphite.
Although the spectra of graphene and graphite appear very similar at first, important differences emerge in the G- and 2D-band regions. Raman can detect subtle changes in these peaks to determine the number of graphene layers, structural quality, strain, and doping effects.
For example, as the thickness of the graphene layers increases, the G-band position shifts slightly due to changes in bond characteristics. Raman can therefore provide detailed structural insights using what appears to be a relatively simple spectrum, making it an essential tool for graphene characterization and development.
How does Raman spectroscopy support process monitoring and industrial manufacturing?
Raman is widely used for real-time process monitoring because it delivers results almost instantaneously.
One example is lithium carbonate production, where Raman continuously analyzes brines during processing. By monitoring dissolved carbonate and lithium carbonate peaks in real time, operators can quickly determine whether the process is functioning correctly and make immediate adjustments if necessary.
This enables faster decision-making, improved efficiency, and substantial savings in costs, time, and resources.
What are some common misconceptions people have about Raman spectroscopy?
One of the biggest misconceptions is that Raman is an intimidating or highly complex technique. In the past, many students and scientists were not exposed to Raman during their education, so it developed a reputation for being difficult.
In reality, modern Raman systems are very user-friendly. Users simply place the sample into the instrument, start the measurement, and receive results almost immediately.
Another misconception is that data interpretation is extremely difficult. While this may have been true years ago, modern software, spectral libraries, and data analysis tools now make identification and interpretation much easier and more accessible.
What are the biggest advantages of Raman compared with other analytical techniques?
One major advantage is speed: Raman measurements are often completed within seconds.
Another important advantage is the ability to analyze samples directly through glass or plastic packaging while preserving sample integrity. This is particularly useful in pharmaceutical and hazardous material applications.
Raman also works very well in aqueous environments because water produces only weak interference. Combined with its non-destructive nature and minimal sample preparation requirements, Raman becomes an extremely versatile analytical tool.
What advice would you give to someone who is new to Raman spectroscopy?
The most important thing is to avoid focusing too heavily on a single peak or isolated spectral feature. Raman interpretation works best when considering the entire spectrum and the broader context of the sample.
It is also important to maintain consistent measurement conditions and build familiarity with how different materials behave spectrally. Modern spectral libraries and software tools are extremely helpful, but users should still review multiple possible matches rather than relying entirely on a single automated identification result.
With experience, Raman becomes a very intuitive and powerful technique.
About Sudhir Dahal 
Sudhir Dahal is the Product Manager for Research Raman Products at Thermo Fisher Scientific, where he specializes in Raman microscopes and Raman spectroscopy solutions for pharmaceutical and industrial applications. He has extensive experience with advanced spectroscopy techniques and helping researchers apply vibrational spectroscopy to solve analytical challenges across materials science, polymers, semiconductors, and life sciences.
Sudhir earned his PhD from the University of Maryland, Baltimore County, where his research focused on developing novel spectroscopy-based techniques for brain tumor cell detection. Throughout his career, he has worked extensively with Raman spectroscopy, microscopy, chemometrics, and process analytical technologies.
At Thermo Fisher Scientific, he focuses on advancing Raman technologies for research, QA/QC, process monitoring, and emerging materials applications such as graphene and lithium battery development. He is also actively involved in science education and regularly presents webinars and technical sessions aimed at making Raman spectroscopy more accessible to researchers across a broad range of industries.
This information has been sourced, reviewed, and adapted from materials provided by Thermo Fisher Scientific - Vibrational Spectroscopy.
For more information on this source, please visit Thermo Fisher Scientific - Vibrational Spectroscopy.
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