We report on a simple, fluorescence-based method for the investigation of the binding kinetics of polystyrene ligands, dispersed in an organic solvent, to substrate supported gold nanoparticles. For this purpose, we develop a protocol for the immobilization of gold nanoparticles on glass substrates, that yields sub-monolayers of randomly distributed particles with excellent homogeneity and reproducibility. Using fluorescently labeled polystyrene, we monitor the ligand concentration in bulk dispersion in real time and follow the binding to the particle-decorated substrates. The influence of the ligand molecular weight on the binding kinetics is investigated. We correlate the reaction rates with the diffusion coefficients of the different ligands and are able to describe the molecular weight dependency with a simple kinetic model. Both the diffusion and the activation step appear to contribute to the effective reaction rates.