Chandrasekhara Venkata Raman (1888-1970), a resourceful physicist, prolific writer, and generous mentor, is best known for the discovery of the light-scattering effect that bears his name. He was the sole recipient of the 1930 Nobel Prize in Physics, an honor bestowed upon him less than two years after the phenomenon was first observed. Interest in Raman spectroscopy grew exponentially within years and, by 1937, close to 1800 papers had been published on the subject.
Since its inception, Raman spectroscopy has been used to probe the vibrational states of the chemical bonds present in an incredible variety of molecular compounds and solid-state materials and is therefore a versatile method for chemical analysis and characterization. Not surprisingly, applications of this spectroscopic technique range from the identification of gemstones and minerals and the remote sensing of explosives to the study of complex biomolecules and drug polymorphs in the pharmaceutical industry.
The Indian stamp illustrated here, issued only a year after Raman’s death, features a portrait of the renowned scientist, his signature, a diamond (a crystalline substance he studied extensively), and the Raman spectrum of carbon tetrachloride (i.e., tetrachloromethane in IUPAC parlance).
As a very sensitive and non-destructive method that requires minimal sample preparation, Raman spectroscopy is a widespread technique used to investigate the composition of works of art and objects of cultural heritage, including paintings, ceramics, glasses, manuscripts, textiles, metals, and even biomaterials such as hair, skin, teeth, and bones. For example, the unequivocal identification of the original pigments used in a painting provides useful information regarding the artist’s working method and facilitates its present-day preservation and authentication.
Interestingly, a recent article in a Royal Society of Chemistry journal (E. Imperio, G. Giancane and L. Valli, Analyst 2015, 140:1702-1710) describes the use of Raman spectroscopy to analyze the printing inks of Italian stamps produced since 1862. This could potentially help in the detection of forgeries of rare or valuable stamps, which I personally think is a beautiful example of analytical chemistry in the service of philately!
©2016 by Walter de Gruyter Berlin/Boston
