In Situ Characterisation of Semiconducting Nanoparticles in Zeolites with XRD, XAFS and SAXS

Abstract

In situ X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS) spectroscopy and Small Angle X-ray Scattering (SAXS) have been used in conjunction with Diffuse Optical Spectroscopy (DOS) to characterise cadmium oxide particles nucleated within cadmium exchanged sodium zeolite Y treated with sodium hydroxide. The zeolite structure is maintained up to 750°C at which point it collapses to an amorphous intermediate. At lower temperatures the synthesis of cadmium oxide can be followed from cadmium XAFS and SAXS. XAFS identifies the nanocrystalline nature of the product and uv-vis spectroscopy the associated effects of quantum confinement. Microstructural changes evident from SAXS are similar to those occurring when cadmium oxide is synthesised from a hydroxyl gel but nanocrystals are smaller with no increase below 200°C, pointing to incarceration in the zeolite network. Subsequent growth of cadmium oxide may be responsible for the eventual collapse of the zeolite structure at 750°C.