Luminescence spectra of chabazite-Ca, a zeolite mineral

Abstract

Chabazite-Ca deposited on dacite laccolith from Osódi Hill, Dunabogdány, Hungary, exhibited bluishwhite luminescence under ultraviolet (UV) light. The photoluminescence (PL) and optical excitation spectra of chabazite-Ca were obtained at 300 K. The PL spectrum under 300-nm excitation consists of (1) a Ce 3? band with a peak at 340 nm, (2) a broad main band with a peak at 453 nm and (3) five narrow bands at 592, 616, 650, 700 and 734 nm due to Eu 3? . The main band is spread over the entire visible-wavelength region. The excitation spectrum obtained by monitoring green luminescence at 520 nm consists of a band at wavelengths shorter than 200 nm and an extremely broad band with a peak at 385 nm. The extremely broad band is spread over not only the UV region but also the blue region. The features of PL and excitation spectra suggest that the origin of bluish-white luminescence is luminescent organic matter incorporated into chabazite-Ca crystals during growth.

Understanding the Dynamics of Fluorescence Emission during Zeolite Detemplation Using Time Resolved Photoluminescence Spectroscopy

“…It is known that zeolite samples have complex photoluminescence mechanisms that have variably been attributed to composition, 48 metal loading 14 or metals stabilized inside a matrix, 49 and product formation 25 in previous studies. It has been assumed here that, in the case of uncalcined chabazite, a significant proportion of the emission is arising as a result of the photoemissive excitation of TMAda.…”

“…It is postulated that confinement reduces permutations for steric conformation and by extension self-quenching of the TMAda leading to an extended triplet state lifetime and greater intersystem crossing efficiency. Room temperature phosphorescence (RTP) of TMAda has been previously reported by propiophenone at room temperature in silicalite, attributing an increased stability of the triplet state to steric confinement within the channels.It is known that zeolite samples have complex photoluminescence mechanisms that have variably been attributed to composition48 , metal loading14 or metals stabilised inside a matrix49 , and product formation25 in previous studies. It has been assumed here that in the case of uncalcined chabazite, a significant proportion of the emission is arising as a result of the photoemissive excitation of TMAda.…”