Viscoelastic Properties of Nanocrystalline Films of SemiconductingChalcogenides at Liquid/Liquid Interface

摘要

The interfacial shear rheological properties of a continuous single-crystalline film of CuS and a 3D particulate gelof CdS nanoparticles (3-5 nm in diameter) formed at toluene-water interfaces have been studied. The ultrathin films(50 nm in thickness) are formed in situ in the shear cell through a reaction at the toluene-water interface between ametal-organic compound in the organic layer and an appropriate reagent for sulfidation in the aqueous layer. Linearviscoelastic spectra of the nanofilms reveal solid-like rheological behavior with the storage modulus higher than the lossmodulus over the range of angular frequencies probed. Large strain amplitude sweep measurements on the CdSnanofilms formed at different reactant concentrations suggest that they form a weakly flocculated gel. Under steadyshear, the films exhibit a yield stress, followed by a steady shear thinning at high shear rates. The viscoelastic and flowbehavior of these films that are in common with those of many 3D “soft” materials like gels, foams, and concentratedcolloidal suspensions can be described by the “soft” glassy rheology model.