A rapid and operator-safe powder approach for latent fingerprint detection using hydrophilic Fe3O4@SiO2-CdTe nanoparticles

A new kind of bifunctional magnetic-fluorescent nanoparticles (NPs) with abundant carboxyls on the surface has been prepared by covalently combining glutathiose (GSH)-modified CdTe quantum dots (QDs) with Fe 3 O 4 @SiO 2 NPs. The silica-coated Fe 3 O 4 NPs were functionalized with amino groups by (3-aminopropyl)triethoxysilane to provide Fe 3 O 4 @SiO 2 -NH 2 NPs, which was then chemically conjugated with GSH-modified CdTe QDs to form bifunctional magnetic-fluorescent NPs, Fe 3 O 4 @SiO 2 -NH-CO-CdTe-QDs NPs. The properties and morphologies of Fe 3 O 4 @SiO 2 -NH-CO-CdTe-QDs NPs were investigated by FTIR, Xray diffraction, transmission electron microscopy (TEM), absorption and fluorescence spectroscopy and vibrating sample magnetometry. TEM images display that Fe 3 O 4 @SiO 2 -NH-CO-CdTe-QDs NPs possess spherical core-shell structure with a uniform size about 50 nm. The bifunctional NPs were found to exhibit good magnetic and strong fluorescent properties favorable for their application in the detection of latent fingerprints. Furthermore, the carboxyls on the surface of NPs have good absorptions with water in air and the residues of fingerprints so as to not only avoid dust flying to protect the health of operators, but also improve the efficiency of detection.