Preparation of Novel Magnetic Nanomaterials Based on “Facile Coprecipitation” for Developing Latent Fingerprints (LFP) in Crime Scenes

[Image: see text] Recently, the application of novel nanomaterials, especially magnetic nanomaterials in the development of latent fingerprints (LFP), has become the hot focus for forensic scientists and criminal investigators. As a type of recyclable, environment-friendly material, Fe(3)O(4) nanoparticles achieve a wonderful effect in visualization of LFP. We first report the synthesis and encapsulation of nano-Fe(3)O(4) through “facile coprecipitation”, (3-mercaptopropyl)triethoxysilane was covalently embedded into Fe(3)O(4) nanoparticles, and the Fe(3)O(4) core was encapsulated by the nanosilver to prepare novel magnetic nanomaterials (P-MNP@Ag) with the core–shell configuration. For comparison, the magnetic nanomaterials (S-MNP@Ag) were prepared by surface modification. Their composition, structure, and properties were characterized by SEM, TEM, XRD, IR, XPS, and VSM. Compared with commercially available gold powder, silver powder, bare magnetic powder, and prepared S-MNP@Ag, the development effect of LFP on different objects by using P-MNP@Ag had better performance, which presented the advantages of low background interference, high sensitivity, and clear secondary details in LFP. In the crime scenes of some influential cases, P-MNP@Ag had been applied to the visualization of LFP. The biometric identification of criminal suspects was confirmed through fingerprint comparison, which was highly affirmed by the public security department.