Highly efficient modulation of upconversion luminescence at a millisecond timescale

Abstract

The highly efficient modulation of the luminescence from upconversion nanoparticles combined with graphene oxide in a thin film was achieved at a millisecond timescale through the photochemical reduction of graphene oxide under UV irradiation. The experimental design comprised the integration of the upconversion nanoparticles with graphene oxide to form a reproducible and scalable thin film. This design enabled convenient testing of the sample with a home‐built optical system setup comprising an UV CW laser at 375 nm for the photochemical reduction of graphene oxide and a near-infrared CW laser at 980 nm for the excitation of the upconversion nanoparticles. The recovery of the graphene‐like structure through the photochemical reduction of graphene oxide was accompanied by a variation in the absorption coefficient of the thin film, which enabled super‐quenching of the luminescence from the upconversion nanoparticles under near‐infrared excitation with values of up to ~90%. Further, the instantaneous reduction in the intensity upon UV irradiation offered decreased modulation time of upconversion luminescence down to milliseconds at microwatt‐level power. Optical patterning was successfully produced in the thin film: representations of a leaf, the Sydney Opera House and a kangaroo were fabricated in the thin film and recovered by raster scanning the sample. The resulting patterns had high spatial resolution for upconversion luminescence modulation down to the diffraction limit for the considered wavelengths. These findings pave the way toward prompt use of this novel thin film for display technologies, photoswitching in optoelectronic devices, and optical data storage applications.