Fluorescent silicon nanoparticles as dually emissive probes for copper(II) and for visualization of latent fingerprints.

The work describes dually-emissive silicon nanoparticles (Si NPs) in aqueous dispersion with two emissions. The Si NPs respond to different solvents independently with various wavelength fluorescence emissions (red to green). The fluorescence emission wavelengths and emissive color of Si NPs can be regulated by adjustment of the solvents. Based on the effect of the solvent, a series different emission color Si NPs is obtained (Si NPs A, B, C and D), which exhibit different fluorescence emission in various solvents. Notably, the Si NP-A (dispersed in water) exhibited excellent analytical performance in sensing Cu2+ ions with amazing fluorescent response from green to brilliant blue light. The much more enhancement at 436 nm than at 500 nm was due to the changing surface chemistry of Si NPs by Cu2+, which was dependent to the concentration of Cu2+ tightly. The excellent sensitivity of Si NP-A towards Cu2+ has been testified with the detection limit as low as 0.91 μM by good linear relationship between ratio of fluorescence intensity (I436/I500) and concentration of Cu2+ (2-30 μM). The Si NP-A can be exploited as a dual-fluorescence visualization agent for latent fingerprints imaging due to the feature of dual emission. The images exhibited green emission under excited at 254 nm, and emerged green light under 365 nm, which allowed the Si NP-A applying in development of latent finger prints at complex background. These acquired fingerprints revealed the particular second-level characteristics. Graphical abstractIllustration of the method for preparation of safranine-dyes silica nanoparticle (Si NPs), the evolution of Si NP-A (VSi NPs/Vwate = 1:2). Si NP-B (VSi NPs/Vdichloromethane = 1:1), Si NP-C (VSi NPs/Vethyl acetate = 1:1) and Si NP-D (VSi NPs/Vacetone = 1:1), and the application of water-dispersed silica nanoparticles (Si NP-A) to the detection and visualization of latent fingerprints (LFPs).