Fluorescent CdTe-QD-encoded nanocellulose microspheres by green spraying method

Abstract With water-soluble CdTe quantum Dots (QDs) as fluorescent labels and TEMPO-oxidized cellulose nanofibrils (CNF) as matrix, dual-color QD-encoded microspheres were prepared by mechanical spraying, freeze-molding and subsequent electrostatic cross-linking by calcium ion. The entire preparation process was accomplished in aqueous phase without any chemical treatment. The nanocellulose microspheres possessed porous structure and were able to be dispersed stably in water in the form of hydrogels. CdTe QDs were efficiently fixed in the network of intertwined nanofibrils via hydrogen bonding with CNF, making the microspheres to obtain high photoluminescence (PL) intensity and identifiable encoding signals consisting of seven kinds of microsphere arrays. The crystalline structure and chemical composition of both CdTe QDs and CNF were not affected during the preparation process. The comparision of PL behaviors of CdTe QDs and QD-encoded microspheres in different media indicate that CNF matrix provided good protection of QDs and improved the PL intensity and photostability. Graphical Abstract Dual-color CdTe-encoded nanocellulose microspheres were prepared via pure physical process in aqueous phase. The fluorescent microspheres possessed high photoluminescence intensity and identifiable seven kinds of encoding signals. The nanocellulose matrix provided good protection of CdTe QDs and improved the photoluminescence intensity and photostability.