Bright red-orange photoluminescence observed from porous silicon nanoparticles with human HeLa cells, magnified 1000 times and viewed in the reflection from a silicon wafer. Prepared from high-purity silicon wafers, these nanoparticles provide a nontoxic and biodegradable alternative to conventional quantum dots for in-vitro and in-vivo fluorescence imaging. The cell nuclei are stained blue.
Credit: Luo Gu, Ji-Ho Park, UCSD
Related info: "Safer Nano Cancer detector" (http://www.nsf.gov/discoveries/disc_images.jsp?cntn_id=114720&org=NSF)