Silver Nanoparticle Gradient Arrays: Fluorescence Enhancement of Organic Dyes.

Noble metal nanoparticles show pronounced extinction peaks in the visible wavelength range due to their localized surface plasmon resonances. The excitation of these resonances leads to strong confinement of electromagnetic energy at nanometer scales, which is critical for ultrasensitive, fluorescence-based detection of analytes. The strength and spatial distribution of this near-field zone depend on particle size, shape, and composition. To determine how these near-field effects depend on the particle size, we have prepared nanoparticle gradients on centimeter-scale substrates using a colloid-based approach. This plasmonic gradient is used to study the steady-state emission and fluorescence lifetime of a common organic dye that was embedded into the monolayer.