Cationic dye-diatomite composites: Novel dusting powders for developing latent fingerprints

Most fingerprints left at crime scenes are latent and require treatment to render them visible. Powder method, the most widely used procedure for developing latent fingerprints, is based on the visual contrast between background surface and powder-covered fingerprint region, thus dusting powders with excellent performance are urgently needed. Four cationic dye-diatomite composite powders with different colors have been prepared relying on the adsorption between cationic dye molecule and diatomite. Compared with synthetic silica matrix, the employment of natural diatomite greatly reduces the amount of dye usage, which is simple, green and low-cost. The cationic dye-diatomite composite powders are successfully used as novel dusting powders for developing latent fingerprints on various substrates including glass slides, notebook paper, PVC sheets, ceramic tile, water bottle label, stainless steel coin, tea caddy, compact disc and packing box. High-quality patterns of fingerprints with second level features can be obtained within a short period of time. This work shows that the cationic dye-diatomite composite powders have high sensitivity, high selectivity and good contrast and are promising for practical use in forensic science.