Gold nanoclusters are grown by 1.8 MeV Au2+ implantation on c-Al2O2(0 0 0 1) substrate and subsequent air annealing at temperatures greater than or equal to 1273 K. Post-annealed samples show plasmon resonance in the optical (579-561 nm) region for average cluster radius similar to0.86-1.2 nm. A redshift of the plasmon peak with decreasing cluster size in the post-annealed samples is assigned to the 'spillout' effect (reduction of electron density) for clusters with similar to157-427 number of Au atoms fully embedded in crystalline dielectric matrix with increased polarizability in the embedded system. (C) 2004 Elsevier B.V. All rights reserved.