Effect of surface adsorbed proteins on the photoluminescence of nanodiamond

Nanodiamond has recently attracted great attention for its intrinsic luminescence in the visible range which can be used as a tracking marker in many biological applications. In this work, photoluminescence (PL) of nanodiamonds interacting with biological macromolecules, such as proteins lysozyme and albumin, is studied. Proteins were physically adsorbed on carboxylated nanodiamonds surfaces. The PL spectra of the protein-nanodiamond complex were measured. It is shown that the surface passivation can modify the nanodiamond luminescence properties. Changes in shape and spectral positions of the nanodiamond PL band were observed and found to depend on excitation wavelength. We attribute the effects to the surface energy traps and transfer between protein and surface nanostructures, particular the graphitelike nanoclusters. This study is important for the bio and medical applications of nanodiamonds used as a biocompatible label. (C) 2011 American Institute of Physics. [doi:10.1063/1.3544312]