Latent fingermarks (LFMs) are served as crucial evidence in screening of identification. There are only a limited number of phosphors with red emission. In this work, the copper nanoclusters (CuNCs) are prepared by chemical reduction of Cu(II) ions using 2-mercaptopyrimidine (MPY) derivatives (such as 4-methyl-2-mercaptopyrimidine (MMPY) and 4,6-dimethyl-2-mercaptopyrimidine (DMPY)), as named MMPY-CuNCs and DMPY-CuNCs, respectively. Although the MMPY and DMPY have the similar skeleton structure in molecular with MPY, the introduction of methyl groups into the skeleton of molecular plays key role in the enhancement of photoluminescence, and leads to the change in the emission wavelengths with an obvious blueshift for the as prepared CuNCs. The DMPY-CuNCs display a higher fluorescence intensity, a larger luminescence quantum yield of 60.19 % and a longer excited state lifetime of 10.14 μs compared with that of the MMPY-CuNCs. The DMPY-CuNCs with a bright red-emissive fluorescence at 700 nm under 372 nm excitation were used for the detection of LFMs left on various objects with different residual times. The DMPY-CuNCs can effectively display and accurately identify the intricate details of LFMs ridges with the features of level 1, level 2, and level 3. Non-permeable and semi-permeable surfaces of various substrates with multicolored and complicated patterns have no notable background interferences on the detection of LFMs. There is a slight drop in the image quality of the aging LFMs compared to the fresh one after the aging time of 21 days. Thus, this work opens a new avenue for the fabrication of CuNCs as a potential red-emissive phosphor that holds promise in identification and detection of the LFMs.
Keywords: Imaging; Latent fingermarks; Metal nanoclusters; Nanocomposites.
Copyright © 2025 Elsevier B.V. All rights reserved.