First hyperpolarizabilities of unprotected and polymer protected copper nanoparticles prepared by laser ablation

In this Letter, we report the first hyperpolarizability of Cu nanoparticles in organic media with and without any stabilizer. Copper nanoparticles of ∼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 β values are (414 ± 19) × 10−30 esu/atom1/2 for the unprotected and (808 ± 12) × 10−30 esu/atom1/2 for the PVP protected Cu-nanoparticles.