This article describes an optimized procedure for the acquisition of 785 nm excited surface enhanced Raman scattering (SERS) spectra of dried bloodstains and shown to offer great potential for rapid, portable, highly sensitive and specific confirmatory identification for forensic applications.
Following extraction in 1 μL of 50-percent acetic acid, a robust, highly reproducible SERS spectrum was observed from dried bloodstains resulting from a hematin-like heme moiety (ferric, high spin). As anticipated, this blood signature can be classified with 100 percent specificity and sensitivity with respect to the SERS spectra of other body fluids. High quality SERS spectra can be observed from stains of blood diluted by as much as 105. Dried blood spectra acquired on Au and Ag SERS active substrates exhibit very different relative intensities at this electronically, non-resonant excitation wavelength (785 nm), indicating that a strong chemical effect contributes to the SERS enhancement of this body fluid. DFT calculations further confirm the vibrational band assignments of the features seen in these SERS spectra of dried blood. (publisher abstract modified)