Preparation, Structure and Luminescence Properties of “Microcrystalline Cellulose—K3Tb(PO4)2” Composites

The paper deals with preparation and optical properties of the oxide-polymer composite consisting of the luminescent K3Tb(PO4)2 polycrystals embedded into microcrystalline cellulose (MCC) matrix. The band gap of the materials under study has been estimated to be 3.76 eV for MCC and 3.15 eV for K3Tb(PO4)2@MCC, respectively. The photoluminescence spectra of the composite depend on excitation wavelengths: cellulose-related emission dominates under excitation at 405 nm while simultaneous emission from cellulose matrix and Tb3+ ions observed for case of λex = 300 nm. At the same time, the composite sample reveals quite intensive green photoluminescence regardless on λex. The main band of luminescence excitation undergoes red-shift when moving from MCC to K3Tb(PO4)2@MCC. These results point out an energy transfer from cellulose to oxide particles. In general, observed peculiarities of the diffuse reflectance and photoluminescence properties reveal interaction between matrix and filler in the composites under study. The specific emission spectra of the composite suggest its possible application at document protection branch.