Raman-based point and proximal detection and imaging

Abstract

Despite massive international search efforts, the detection and identification of hazardous materials is still a persisting challenge. Here, a modular, compact Raman spectrometer for short distance detection and imaging of traces of explosives and related compounds was developed. It utilized green excitation sources (a laser pointer, or a hand-held laser) and the resultant beam was focused as point or line on particular samples. The ensuing signals were detected and employed for sensitive and selective detection of different liquids and individual particles, placed on a variety of substrates. Synchronization of sample movement with detector readout, allowed obtaining not only characteristic Raman signals but also Raman images of traces of different compounds. Imaging was carried out by point-mapping, photo-guided sampling/point-mapping and line-mapping, where the latter two approaches allowed detection and mapping of individual particles at considerably reduced sampling times. It is anticipated that realization of these operation modes can lead to improved performance and be applied for examination and identification of objects contaminated with harmful compounds. This suggests the possibility for future use of the setup as a fast, compact, and relatively low-cost system for detecting and mapping a variety of samples under lab conditions and, following additional improvements, for field measurements.