Sol–gel derived red fluorescent nanocomposites of copper nanoclusters conjugated silica for visualizing latent fingerprints

Abstract

Phosphors with red emission have attracted increasing interests due to their high contrast and low interferences of fluorescence background which play a vital role in visualizing latent fingerprints (LFPs) in forensic science. In this work, red-emissive fluorescent nanocomposites of copper nanoclusters conjugated silica (CuNCs/silica) are prepared simply by sol-gel method in one pot for visualizing the LFPs through powder-dusting method. The CuNCs/silica exhibits the red fluorescence with an emission wavelength of 628 nm under the excitation of 292 nm and can have sufficient affinity with the LFPs ridges. The CuNCs/silica with the photoluminescence properties can precisely visualize and capture the clear patterns and the well-defined details of the LFPs ridges on the non-porous and semi-porous surfaces of different substrates (including copper foil, compact disc, tiles, stainless steel, aluminum foil, glass slide, Hong Kong currency, colored plastic packing, colored paper and leather) even with fluorescent background. The ridge details of the aged LFPs can also be clearly identified. These suggest the great potential of the CuNCs/silica as phosphors for visualizing the LFPs in criminal investigations.