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Non-toxic Au nanoclusters@montmorillonite (AuNCs@MMT) nanocomposites with strong red fluorescence are prepared by a microwave (MW)-assisted synthesis method and immobilize Au NCs into sodium MMT clay matrix via electrostatic interaction. Due to the immobilization of Au NCs in the layered structure of the MMT clay matrix, the formative AuNCs@MMT nanocomposites show high emission, stable chemical features and less toxicity. The obtained Au NCs and AuNCs@MMT nanopowders were characterized by using UV-visible absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, TEM/HRTEM, SEM and XRD etc. to depict their sizes, microstructures and optical features.Due to their environmentally friendly preparation, time-saving procedure, user-friendly operation, low cost, efficient UV-visible radiation-dependent photoluminescence and good affinity with finger residues, the as-synthesized AuNCs@MMT nanopowders are employed as a alternative florescent developing reagent for enhancing latent fingerprints deposited on various object surfaces (such as glass, porcelain enamel, stainless steel, painted metal, plastic products, weighing papers etc.) for individual identification. As results, the enhanced fingerprints with clear patterns and satisfactory ridge details were obtained by using as-prepared AuNCs@MMT nanopowders. At the same time, intensively red fluorescence as well as good contrast without background staining of developed prints demonstrated great advantages for surfaces with multicolour. Because of their good sensitivity, non-toxicity and strong resistance to background interference, the as-prepared fluorescent nanocomposites are an actual alternative to conventional powdering reagents, which may find potential application in forensic detection.

Novel fluorescent nanocomposites prepared by microwave irradiation and electrostatic adsorption have been formulated for developing latent fingermarks on various object surfaces. As-synthesized carbon dots@montmorillonite (C-dots@PGV) nanocomposites were characterized using UV–visible absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, TEM/HRTEM, SEM and XRD. Due to its photoluminescence and stable chemical properties, C-dots@PGV nanocomposites powders with intense fluorescence produce sharp and clear development of latent fingermarks with good contrast and satisfactory ridge details. It is widely used for painted metal, glass, plastic and stainless steel surfaces, and the small, fine fluorescent nanocomposites demonstrate great advantages. Especially for multicolor surfaces, the fluorescent probe can help us to observe and photograph using UV light as excitation light source to eliminate background effects. After developing by facile powder technique, the prints emit strong violet-blue fluorescence under UV light (365 nm), at the same time, this nontoxic powder without any organic solvent and dyes can reduce harm to the operators.