Effect of the surfactant CTAB on the high pressure behavior of CdS nano particles

Angle dispersive x-ray diffraction studies on CTAB capped cadmium sulphide (CdS) nano particles of sizes 70 nm, 44 nm and 10 nm have been carried out up to ∼39, ∼30 and ∼28 GPa respectively. All the three types of nano particles transform to the rocksalt phase at pressures higher than that of bulk CdS. Our analysis of the x-ray diffraction data indicates that the phase transition pressure as well as the bulk modulus of the rocksalt phase of CdS exhibits a non monotonous behaviour as a function of the size of the nano particles. Our high pressure Raman scattering studies on the 10 nm CdS nano particles are in agreement with the x-ray diffraction studies. The presence of the Raman mode in the high pressure rocksalt phase may be attributed to a disorder activated scattering in this phase or to the formation of a core shell structure beyond the transformation pressure.