Enhanced fluorescence from fluorophores on fractal silver surfaces

Recent reports have shown enhanced fluorescence for fluorophores in close proximity to chemically deposited silver islands or colloids. To expand the usefulness of metal-enhanced fluorescence we tested fractal silver structures formed on, or near, silver electrodes by passage of electric currents. The emission intensity of fluorescein-labeled human serum albumin (FITC-HSA) was enhanced over 100-fold when adsorbed to the fractal silver structures as compared to glass. The amplitude-weighted lifetime is dramatically reduced to near 3 ps. Enhanced fluorescence was shown to result in selective observation of FITC-HSA over a fluorophore not attached to the silver surface. And finally, photostability measurements indicate 160-fold more photons are detectable from FITC-HSA on the fractal silver surface. These results suggest the use of in situ generated silver structures for metal-enhanced fluorescence.