Nanoparticle-mediated nonfluorescent bonding of microspheres to atomic force microscope cantilevers and imaging...

A technique to attach silica and glass microspheres onto silicon or silicon nitride cantilevers using silica nanoparticle sol-gel chemistry is presented and a method to image the fluorescence background from the bonded cantilevers with single molecule sensitivity is described. The silica nanoparticles polymerize to form a highly branched network that covalently link the microsphere and cantilever together. The bonding is carried out at room temperature which preserves the integrity of the cantilevers and their reflective coating. Comparison of cantilever and single dye molecule fluorescence demonstrates that the cantilevers are nonfluorescent at the single molecule level.