Methods of characterizing nanoparticles, nanoparticle complexes, and their biomolecular interactions are provided. Concurrent excitation and emission wavelength scans are performed and the optimal fluorescence intensity for the intersect of these wavelengths is determined. The intersect is dependent upon the physical characteristics of the particle and can be used to verify, for example, attachment of biomolecules, amount of biomolecules present, and structure of the attached biomolecule.
Two-dimensional fluorescence difference spectroscopy characterization of nanoparticles and their interactions