Forensic Paint Analysis with Simultaneous Optical Photothermal Infrared (O-PTIR) and Raman Microspectroscopy
Wednesday, March 10, 2021: 10:45 AM - 11:05 AM
Paint evidence can provide valuable associative information for crimes involving vehicular accidents and home invasions. The complex chemistry of paint is thoroughly interrogated with vibrational microspectroscopy, with results that are used for its classification and comparison. Traditional IR microscopy is frequently used to identify binders, some pigments and additives, while Raman microspectroscopy affords the additional ability to identify colored pigments thus providing complimentary information. However both traditional IR and Raman microspectroscopy have limitations which prohibit a complete chemical characterization of multi-layered paint samples, especially those with layers thinner than 10 µm. The mIRage+R microscope is a new technology that combines O-PTIR with Raman microspectroscopy to enable the complementary and confirmatory analysis of a sample in a single measurement. O-PTIR uses a visible light probe to measure the photothermal response of the absorption of radiation from a pulsed IR laser focused on the sample. The use of visible light allows for non-contact, reflection mode analysis with submicron spatial resolution that is independent of the IR wavelength. Further, analysis is fast (~1s) and requires little to no sample preparation. The spectra are free of specular and diffuse scatter artifacts and can be directly compared to transmission IR databases. When combined with a Raman spectrometer, the visible light probe doubles as the Raman excitation laser, thus allowing for IR and Raman spectra to be simultaneously and non-destructively collected from a submicron-sized spot in seconds. IR+Raman data collection can create a line array in under a minute, and map an area of a sample to create a hyperspectral image within a few minutes to a few hours (depending on the sampling area and desired spatial resolution). This presentation will detail the benefits of O-PTIR combined with Raman microspectroscopy for the analysis of automotive paint.
Keywords: Please select up to 4 keywords ONLY:
Materials Characterization,Paint/Coatings,Infrared Spectroscopy,Raman/Surface Enhanced Raman Spectroscopy