Capturing the formation of sub-nanometer sized CdS clusters in LTL zeolite
Résumé
The radiolytic preparation of sub-nanometer sized CdS clusters in LTL-type zeolite crystals in suspension is reported. The growing process of CdS in the zeolite crystals using a γ-ray irradiator (low dose rate) and a pulse electron accelerator (high dose rate) is followed by UV-vis spectroscopy. The pulse electron accelerator equipped with a transient absorption setup allowed the real-time capturing of CdS formed in the zeolite suspension. Two distinct stages during the formation of sub-nanometer sized CdS clusters in the LTL-type zeolite are identified: (i) fast formation of dispersed small oligomers exhibiting a well-defined sharp absorption peak, which is shifted from 292 to 350 nm in the course of the growth process, and (ii) formation of interconnected CdS clusters along the zeolite channels by diffusion-assisted process. Additionally, the presence of sub-nanometer sized CdS clusters in the zeolite channels is confirmed by transmission electron microscopy (TEM). The sub-nanometer sized CdS clusters formed in the LTL-type zeolite suspension exhibit good stability under hydrous conditions, and no coalesce in the presence of water is observed.