In this Letter, we report the first hyperpolarizability of Cu nanoparticles in organic media with and without any stabilizer. Copper nanoparticles of similar to 9 nm size were prepared by laser ablation of a Cu-metal target immersed in isopropanol both in the presence and absence of polyvinyl pyrrolidone (PVP, a stabilizer and a surface modification agent). The first hyperpolarizability of the nanoparticles was measured by the hyper-Rayleigh scattering (HRS) technique. Both types of nanoparticles show large second harmonic response and the beta values are (414 +/- 19) x 10(-30) esu/atom(1/2) for the unprotected and (808 +/- 12) x 10(-30) esu/atom(1/2) for the PVP protected Cu-nanoparticles. (c) 2006 Elsevier B.V. All rights reserved.