Can anyone suggest how to calculate what type of bands present in the sample if we collect Raman spectra?
Recently I take the Raman spectra of my sample it shows three intense peaks in the range of 180, 570 and 640 and one small peak around 400 so how to interpret this and what type of vibration present in the sample?
Hi
Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. A source of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range is used, sometimes X-rays can also be used.
The laser light interacts with molecular vibrations, or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system.
So when you got unknown peaks in your spetctra, depends on impacting band in the structure the shift will be observing, and not necessarily the intensity.
You can refer to comprehensive Raman handbooks which is available online easily, like:
https://www.sciencedirect.com/book/9780124511606/the-handbook-of-infrared-and-raman-characteristic-frequenci es-of-organic-molecules
and find out which chain or bands in your molecule has got impact on that specific wavelength and shift/intensity has occurred.
I hope that’s helpful.
Ashkan Nikiyan thank you for this information. Can you provide information regarding Raman peak fitting and is there any point to peak fitting in Raman spectra or not, and what information we get if we fit peaks for Raman spectra.
Thank you
The principle of operation of Raman spectroscopy is based on the measurement of the shift in frequency (or energy) of the scattered light following its incidence on a sample.
The frequency of most of the scattered light is similar to that of the incident light. But a fraction of the scattered light is at a different frequency. This shift in frequency gives rise to the effect referred to as Raman
scattering. The difference in frequency between the incident and scattered light is termed Raman shift.
In response to your question, a number of significant information can be obtained from the Raman spectra with peaks fitting techniques which are both qualitative and quantitative in nature.
In our studies, when I was examining composite materials commonly used in organic electronics, for example blends of polymers/polymers or polymers/fullerenes for light emitting diodes (LEDs) or solar cells, their identification and characterisation are important.
The qualitative analysis of Raman spectra can also be used to map composite materials. The intensities of peaks (or bands) observed in OSCs active layer thin films, for example, have been shown to correlate with the concentrations of the functional groups in active layer molecules yielding them. So it can be possible to identify a distribution of composite components in a mapped image.
Probing the nature of conformation of nanodomains of composite materials within thin films can also be achieved using Raman spectroscopy. Such knowledge is useful for understanding the impact of thin film nanodomains on the performance of OSCs.
So depends of your samples definition and type of substances used, different fitting techniques on peaks can give you a different interpretation.
Analytical software like “OriginPro” or integrated Raman apparatus softwares like WiRE3 for Renishaw inVia Raman can also be helpful to have Gaussian distribution or a mixture of other fitting techniques to find out peaks numerical parameters.
I hope that’s helpful. 🙏
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