The luminescent gold(I)–alkanethiolates containing two types of alkyl groups, Au(I)–(SR) x (SR′) y s, were synthesized by mixing HAuCl 4 with two n-alkanethiols in tetrahydrofuran. Au(I)–(SR) x (SR′) y s have highly ordered bilayer structures and the dominant conformations of the alkyl groups were found to be all-trans from X-ray diffraction and FT-IR spectroscopy studies. The gold nanoparticles stabilized by two types of alkanethiolates could be prepared by reducing the Au(I)–(SR) x (SR′) y s using tetrabutylammonium borohydride (TBABH) as a reducing agent. Elemental analysis results of Au(I)–(SR) x (SR′) y s and gold nanoparticles prepared from Au(I)–(SR) x (SR′) y s indicated that the longer alkanethiols are more reactive for the formation of Au(I)–(SR) x (SR′) y s and also the longer alkylthiolates are preferentially absorbed on the gold particles compared with the shorter ones.