Photoluminescent nanocellulose-reinforced polysiloxane nanocomposite adhesive for advanced applications

Inorganic phosphors have shown high quantum efficiency, thermal and chemical resistance, high brightness, and photostability as compared to optically active carbonaceous agents. Herein, the present research presents a simple strategy for developing a photoluminescent, waterproof adhesive. A hybrid nanocomposite was developed by embedding lanthanide-doped aluminate nanoparticles (LAN; photoluminescent agent) and cellulose nanocrystals (CNC; dispersing and reinforcing agent) into a room-temperature-vulcanized silicone rubber (VSR; host adhesive) matrix. CNC, with diameters ranging from 4 nm to 10 nm, served as a reinforcement material in the nanocomposite, improving the mechanical properties of the polysiloxane adhesives. Additionally, CNC functioned as a dispersing agent, preventing the aggregation of LAN. The small size of LAN (14–34 nm) enabled good dispersion in the polysiloxane matrix without aggregation, maintaining the adhesive's transparency. When excited at 375 nm, the photoluminescent adhesive showed two emission bands at 439 nm (blue emission) and 517 nm (green emission). Depending on the LAN content, photoluminescence analysis showed either fluorescence or afterglow emission. The afterglow adhesive emitted light for up to 90 min after removal of the excitation light source. The photoluminescent adhesive changed from transparent to greenish under UV irradiation and to yellowish green in the dark. The use of LAN nanoparticles improved the scratch resistance and hydrophobic properties of the adhesive material. Due to the high stability and anti-photobleaching properties of the LAN@VSR nanocomposite, the current study provides a potential approach toward the mass production of smart adhesive for numerous potential applications, such as smart windows, safety signs, and anti-counterfeiting stamps.