Luminescent composite based on NaY(MoO4)2:Yb3+/Er3+ particles and bacterial cellulose film for thermal sensors

The trend to get environmentally friendly materials has led to research into biopolymers, such as using multifunctional materials as cellulose. In this work, organic–inorganic composite self-supported films were prepared from membranes of the bacterial cellulose (BC) and NaY(MoO 4 ) 2 particles doped with Er 3+ and Yb 3+ ions stabilized into a boehmite–epoxi-siloxane hybrid. These have the advantage of combining features of both biopolymer and luminescent particles, which can be tailored to enhance upconversion (UC) emission in a flexible composite film. The synthesis of molybdate particles resulted in a tetragonal crystalline structure of Scheelite without water and organic residues, the particles showed a dandelion flower shape as corroborated by SEM and TEM images. The downshift studies confirmed a charge transfer from the molybdate matrix to lanthanide ion followed by emission on visible and near-infrared spectra. The upconversion studies were carried out and resulted in an energy transfer upconversion (ETU) mechanism associated with two photons absorption to the emission at green or red spectrum. Finally, the upconversion behavior was systematically analyzed as a function of temperature, and the spectroscopy data supported that the excited levels ( 2 H 11/2 and 4 S 3/2 ) are thermally coupled, and the integrated intensity emission from them were dependent on temperature. Then, this work presented potential material to the development of thermal sensors or photonic flexible film with at the naked eyes emission under excitation at 980 nm.