Gold nanoparticle I and nanoparticle II protected by 10-(1-pyrenyl)-6-oxo-decanethioI and 17-(1-pyrenyl)-13-oxo-heptadecanethiol, respectively, were prepared and characterized by H-1 NMR, FT-IR, XPS, UV-vis and fluorescence spectroscopies and TEM and elemental analysis. Their compositions were determined to be (C25H27OS)(225).Au-1601 and (C32H41OS)(120)-Au-1052, respectively. Unusual fluorescence enhancement was observed for the aged solutions of nanoparticle I and nanoparticle II, and a possible explanation for this phenomenon was also discussed. This experimental finding provides further evidence for the chain density gradient and the motion of termini groups of alkanethiolates adsorbed onto the surface of gold nanoparticle.