Fluorescence Spectroscopy with Correlated Atomic Force Microscopy of Gold Nanoparticles and Meso-scale Ribbons

Studies on the optical properties of gold nanoparticles are of great interest due to the size and shape control and easy adaptability through functionalization to most any application, everything from nanomedicine to nanosensing. Gold nanoparticle optical properties change with size, morphology, and environment. Gold nanospheres were explored to determine the effect of environmental change, from many particles in solution to a single particle immobilized and in air, on fluorescence peak position. A statistical distribution of single gold nanorod fluorescence spectra demonstrate the spectral changes associated with slight variations in size. In solution, gold nanorods self-absorb and only exhibit bulk gold fluorescence while immobilized gold nanorods maintain surface plasmon resonance fluorescence peaks. A single gold nanoctahedron and a dimer of two, interacting gold nanoctahedra exhibit the increase in number of peaks when two gold nanoparticles are in close proximity. Observed fluorescence blueshifting occurs due to a lack of a solvent environment as our gold nanoparticles are immobilized and in air. A linear correlation between gold nanoparticle fluorescence and an attached fluorescent dye is observed. These dye components also act as the binding agent, creating self-assembled meso scale ribbons of conjugated gold nanospheres. Correlated atomic force measurements of particle morphology and single particle emission spectra will be presented for a variety of structures. Atomic force microscope images with the associated high resolution fluorescence microscope images and single-particle total-internal reflection fluorescence spectra are recorded using a single instrument. These measurements enable correlation of the optical properties with particle size and its characteristics.