Characterization of core/shell (Ag/CdSe) nanostructure using photoacoustic spectroscopy

Abstract

Photoacoustic (PA) technique has been used to study the optical and thermal properties of core/shell (Ag/CdSe) nanostructure. Core shell Ag/CdSe nanostructure particles were prepared using organometalic method, having a core of (12 -14 nm) and CdSe shell thickness ranging from (2.59 nm to 5 nm) as determined by TEM. The PA spectra were compared with regular UV-Vis absorption which gave comparable results, though the UV-Vis is for colloidal form and the PA spectra is for powder form. The obtained spectra are combination of the surface plasmon (SP) absorption bands of the Ag core and the band gap of CdSe shell. Second derivative fitting method and Gaussian peak fitting were used to determine precise absorption peaks and band of the PA spectra. The SP bands of the Ag core show a decrease in amplitude, broadening of the width and red shift as the CdSe shell thickness increases. The CdSe absorption band edge also shows an increasing red shift from (517 nm to 604) nm with the increases in the thickness. The thermal diffusivity of the Ag/CdSe core shell samples increase by an order of magnitude larger than the CdSe bulk value which is caused by Ag core.