Second harmonic scattering of redox exfoliated two-dimensional transition metal dichalcogenides

We report the second harmonic scattering experiments from acetonitrile liquid suspensions of two-dimensional metal dichalcogenide nanoflakes,: semiconducting MoS2 and WS2, metallic NbS2, semi-metallic ZrTe2. Because study is directly performed in phase, no symmetry breaking can be attributed to a supporting substrate as it often case investigation generation efficiency for these materials. A comparative look origin nonlinear response using polarization analysis hyper Rayleigh intensity performed. Retardation clearly exhibited by all nanoflakes considering their average dimensions but remains weak. This non-negligible role played nanoflake edges or presence surface absorbed polyoxometalates (POMs), cases.