Method Development for the Application of Vibrational Spectroscopy to Complex Organic-Inorganic Materials in Astrobiology. A Systematic Development of Raman Spectroscopy and Related Analytical Methods to the Structural Chemistry at Organic (Biological) and Inorganic (Mineralogical) Interfaces of Material Assemblies Relevant to Astrobiology and Inter-Planetary Science.

摘要

In the search for the conformation of extant or extinct life in anudextraterrestrial setting the detection of organic molecular speciesudwhich may be considered diagnostic of life is a key objective. Theseudmolecular targets comprise a range of distinct chemical species,udwith recognisable spectroscopic features. This project aims to useudthese features to develop an in-situ molecular specific Raman spectroscopicudmethodology which can provide structural information aboutudthe organic–inorganic interface.udThe development of this methodology identified a surface enhancedudRaman spectroscopic technique, that required minimal sample preparation,udallowed for the detection of selected organic species immobilisedudon an inorganic matrix and was effective for quantities belowudthose which conventional dispersive Raman spectroscopy would detect.udFor the first time spectral information was gained which allowedudanalysis of the organic–inorganic interface to be carried out, thisudgave an insight into the orientation with which molecules arrange onudthe surfaces of the matrices. Additionally a method for the detectionudof organic residues intercalated into the interlamellar space of smectiteudtype clays was developed. An evaluation of the effectiveness ofuduni and multivariate methods for the analysis of large datasets containinguda small number of organic features was also carried out, with a view to develop an unsupervised methodology capable of performingudwith minimal user interaction. It has been shown that a noveluduse of the Hotellings T2 test when applied to the principal componentudanalysis of the datasets combined with SERS allows identificationudof a small number of organic features in an otherwise inorganicuddominated dataset.udBoth the SERS and PCA methods hold relevance for the detectionudof organic residues within interplanetary exploration but may also beudapplied to terrestrial environmental chemistry.