Dual-emitting film with cellulose nanocrystal-assisted carbon dots grafted SrAl2O4, Eu2+, Dy3+ phosphors for temperature sensing.

In this study, we synthesized a novel dual-emitting fluorescent phosphor from cellulose nanocrystal (CNC)-assisted carbon dots (CDs)-grafted SrAl2O4, Eu2+, Dy3+ (SAO) through a facile core-shell process. The CNC-CDs-coated SAO presents excellent scattered dual-emission and improved water resistance without destruction of the SrAl2O4 crystals. The phosphors were then reacted with coupling amino-silane and assembled with nanofibrillated cellulose skeletons to create flexible isotropic films. The obtained phosphors and hybrid films were characterized via electron microscopy, photoluminescence analysis, and X-ray photoelectron spectroscopy. The results demonstrate that the optical signals of phosphors can be controlled by CDs content. The assembled cellulose films exhibit strong temperature responses, high light-induced scattering, and good flexibility. The luminescent emission of films is highly sensitive to surrounding temperature variation (243-383 K) and good linearity behavior was obtained for such a sensitive sensor. Such flexible nanofibrillated cellulose films are excellent candidates for temperature sensor devices in industrial applications.