Plasmon-controlled fluorescence and single DNA strand sequenching.

During the past several years we have studied the effects of metallic surfaces and nanostructures with fluorophores. We have demonstrated the metal-enhanced fluorescence (MEF) and the significant changes in the photophysical properties of fluorophores in the presence of metallic nanostructures and nanoparticles using ensemble spectroscopic studies. These studies have shown dramatic increases in brightness and photostability, especially for low quantum yield fluorophores. Much of this work was performed using visible or NIR fluorophores. In the present study, we have extended our studies to UV wavelengths and have shown that aluminum and platinum particles can enhance the emission of UV fluorophores including intrinsic protein fluorescence from 300 to 420 nm. We used the finite-difference timedomain (FDTD) method to calculate the effects of aluminum nanoparticles on nearby fluorophores that emit in the UV. And also we performed experiments to investigate the effect of metallic nanoparticles on fluorescence intensity of DNA bases and DNA G-quadruplex. We observed increase in fluorescence intensities of DNA bases varied range changing from 20 to 3-fold in steady-state fluorescence emission measurements. We obtained ~5-fold increase in fluorescence intensity of DNA G-quadruplex on both Al and Pt metallic substrates when compared with control quartz substrates.