Synthesis, nonlinear optical properties and cellular imaging of hybrid ZnS nanoparticles capped with conjugated terpyridine derivatives

A novel organic/inorganic nanohybrids which consisted of ligand L (L = 2-[(2-hydroxy-ethyl)-(4-[2,2′;6′,2″] terpyridin-4′-yl-phenyl)-amino]-ethanol), an optical terpyridine derivative and ZnS nanoparticles (NPs), had been prepared through a solution-phase synthesis technique. The intermolecular interactions at the interface between ZnS and the ligand components were analyzed by FT-IR, far-IR, UV–Vis absorption spectroscopy, XRD and TEM. Particular properties had been shown by fluorescence spectra, fluorescence lifetime, Raman spectrum, aggregation emission and non-linear optical response. The results indicated that the nano-composite L–ZnS NPs had an obvious aggregation-induced emission in ethanol/n-hexane mixtures, and had larger two-photon absorption (TPA) when compared to the free ligand L. The data for the TPA cross-section value (σ = 16,247.8 GM), nonlinear refractive index (γ = 4.46 × 10−13 cm2 W−1) and the third order nonlinear polarizability [Imχ(3) (esu) = 1.13 × 10−14] were measured and discussed. Meanwhile, due to the laser irradiation induced charge transfer from the ligand to ZnS NPs, the composite could be potentially applied in vitro and in vivo cellular imaging.