Pilot Study on the Visualization of Latent Fingerprints and Naked Eye Detection of Hg2+ and Zn2+ Ions in Aqueous Media Using Ninhydrin-Based Thiosemicarbazone

Here, we described a cheap and effective chemosensor (NHPyTSC) that can distinguish Hg2+ and Zn2+ ions from other metal ions and evaluated this phenomenon using several spectroscopy techniques. With the addition of mercury and zinc ions, the proposed chemosensor in particular showed noticeable changes in color and absorption spectra. Additionally, by including EDTA in the NHPyTSC-Hg2+ and NHPyTSC-Zn2+ solutions, colorimetry readings can be reversed. We developed a molecular-scale sequential information processing circuit and presented the “writing–reading–erasing–reading” and “multiwrite” behaviors in the form of binary logic based on the great reversibility of this process. Moreover, by sequentially adding Hg2+, Zn2+, and EDTA, NHPyTSC imitates a molecular keypad lock and molecular logic gates. Density functional theory (DFT) investigations provided more evidence of the Hg2+ and Zn2+ ions′ ability to attach to NHPyTSC. The most interesting part of this work is that a study on the latent fingerprint detection of the powder compound revealed that NHPyTSC exhibits good adherence and finger ridge features without background stains. When compared to black and white fingerprint powders, it is discovered that the NHPyTSC powder produces results that are remarkably clear on the majority of surfaces. This demonstrated their potential for real-world use, particularly in the area of criminal investigations.