Porous Silicon Nanoparticles with Rare Earth as Potential Contrast Agents for MRI and Luminescent Probes for Bioimaging

Nanoparticles of porous silicon with incorporated europium and gadolinium ions were prepared by using mechanical grinding of electrochemically grown mesoporous silicon films followed with impregnation with rare earth ions from aqueous solutions. The photoluminescence spectroscopy of europium doped porous silicon nanoparticles allowed us to reveal narrow lines associated with the 5D0→7F4 transitions in Eu3+ ions. Measurements of the proton relaxation in aqueous suspensions of nanoparticles with embedded Gd3+ ions showed an effect of the shortening of both the longitudinal and transverse relaxation times. Potential applications of rare earth doped porous silicon nanoparticles as contrast agents in MRI and fluorescent labels in bioimaging are discussed.