A synergistic combination of local tight binding theory and second harmonic generation elucidating surface properties of ZnO nanoparticles.

Zinc oxide (ZnO) in the form of nanoparticles (NPs) is an important nanomaterial due to its catalytic and optoelectronic properties. An interesting aspect of ZnO is that its crystal structure is anisotropic, which leads to a strong 2nd order nonlinear response, such as frequency doubling or second harmonic generation (SHG). In this article we show that not only the bulk but the surface of ZnO NPs in contact with a liquid medium can contribute to the overall SHG. We have developed and applied a synergistic combination of tight binding (TB) theory and optical SHG spectroscopy to determine the surface second order susceptibilities of nearly spherical 33 ± 13 nm crystalline ZnO NPs dispersed in acetonitrile. The corresponding χ and χ were determined to be 0.86 × 10