A series of alkanethiols, n-decanethiol (C10SH), n-dodecanethiol (C12SH), n-tetradecanethiol (C14SH), n-hexadecanethiol (C16SH), and n-octadecanethiol (C18SH), were introduced to study the reactivity of the laser-prepared Cu nanoparticles. The colloidal solutions containing alkanethiols resulted in the disulfide (RSSR) formation. In particular, the colorless and the lathy crystals were generated from the C14SH, C16SH, and C18SH. The psuedo-one-dimensional lathlike structures were resolved by the X-ray crystallographic analysis. UV-vis, TEM, high-resolution XRD, and proton NMR were carried out to characterize the Cu nanoparticles and the disulfide products. XPS and XANES measurements were employed to identify the Cu identity, as well. The laser-prepared Cu particles were mainly +0 charge with the possible formation of a thin Cu2O layer on the copper surfaces. It was interpreted that the disulfides resulted from the Cu and/or Cu (core)/ Cu2O (thin shell) particles.