A water-soluble gold nanoparticle was prepared with trisodium citrate and hydrogen tetrachloroaurate by reduction method. Using mercaptoundecanol as a self-assembled molecule, self-assembled monolayer-protected gold nanoparticle was obtained. Various techniques, such as UV-Vis spectrophotometry, transmission electron microscopy, laser scattering size analysis, synchronous light-scattering spectrum, emission spectrum, were used to characterize nanoparticles. The diameter of monolayer-protected gold nanoparticle was about 20.2 nm, bigger than that of gold nanoparticle of 14.6 nm. There were about 9.65×10⁴ gold atoms in a gold nanoparticle and 7.52×10³ mercaptoundecanol molecules binding to it. The monolayer-protected gold nanoparticle was global and compact. Compared with gold nanoparticle (518 nm), its UV-Vis absorption peak has been red-shifted to 535 nm. Both gold nanoparticles and monolayer- protected gold nanoparticles had a nonlinear light-scattering characteristic.

Key words: preparation, gold nanoparticle, self-assembled monolayer, synchronous light-scattering spectrum, mercaptoundecanol