Surface enhanced Raman scattering for robust, sensitive detection and confirmatory identification of dried bloodstains

An optimized procedure is described for the acquisition of 785 nm excited 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 mu L of 50% acetic acid, a robust, highly reproducible SERS spectrum is observed from dried bloodstains resulting from a hematin-like heme moiety (ferric, high spin). As anticipated, this blood signature can be classified with 100% 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 10(5). 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.