Laser induced fluorescence studies of single-strand (ss) DNA hybridization based on fluorescence quenching by gold nanoparticle through a distant dependent process has been carried out. Distance- and size-dependent optical absorption properties have been described using extended Mie calculations and compared with the experimental findings. The fluorescence of ss-DNA increases by a factor of 100 when it binds to a complimentary DNA while the addition of single-base mismatch DNA had no effect on the fluorescence efficiency. The mechanism of distant dependence fluorescence quenching has been discussed and our experimental results match reasonably well with the theoretical findings using fluorescence quenching model by Gersten and Nitzan. (c) 2005 Elsevier B.V. All rights reserved.