The role of mobile instrumentation in novel applications of Raman spectroscopy: archaeometry, geosciences, and forensics
The applications of analytical Raman spectroscopy in the characterisation of materials associated with archaeologically excavated artefacts, forensic investigations of drugs of abuse, security and crime scenes, minerals and rocks and future astrobiological space missions are now well established; however, these applications have emphasised the need for new developments in the area of miniaturised instrumentation which extends the concept and breadth of the analytical requirement to facilitate the provision of data from ‘in field’ studies. In this respect, the apparently unrelated themes of art and archaeology, forensic science, geological science and astrobiology as covered by this review are unified broadly by the ability to record data nondestructively and without resorting to sampling and the subsequent transfer of samples to the analytical laboratory. In studies of works of art there has long been a requirement for on-site analysis, especially for valuable paintings held under strict museum security and for wall paintings which cannot physically be removed from their setting; similarly, the use of portable Raman spectroscopy in archaeological and geological field work as a first-pass screening device which obviates the necessity of multiple and wasteful specimen collection is high on the wish-list of practicing spectroscopists. As a first-pass screening probe for forensic crime scenes, Raman spectroscopy has proved to be of inestimable value for the early detection of dangerous and prohibited materials such as drugs of abuse, explosives and their chemical precursors, and banned contraband biomaterials such as ivories and animal products; in these applications the advantage of the Raman spectroscopic technique for the recognition of spectral signatures from mixtures of inorganic and organic compounds is paramount and not afforded by other less portable instrumental techniques. Finally, in astrobiological work, these requirements also apply but with the additional prerequisite for system operation remotely – often over distances of several hundred million kilometres – as part of instrumental suites on robotic spacecraft and planetary landers; this necessitates robust and reliable instrumentation for the observation of unique and characteristic spectral features from the planetary geological surface and subsurface which are dependent on the assignment of both biological and geological band signatures.