Near-Field-Enhanced Supersurface Structures for UCNPs Fluorescence Enhancement and Ultrasensitive Gas Sensing

Lanthanide-based upconversion nanomaterials (UCNPs) have been widely used in micro-nano sensors and high-precision bioimaging due to their excellent optical properties. However, their performance is severely limited by drawbacks such as low quantum yield. In this work, we present the enhancement of upconversion nanomaterial emissions through surface plasmon near-field modulation. PS sphere array @Au film @UCNPs composite structure was prepared through self-assembly, allowing for highly localized and amplified excitation on the upper surface of the PS sphere array, thereby promoting the upconversion process. Based on this composite structure, we discuss its sensing performance for ammonia gas. The detection limit for ammonia gas at room temperature is 6.6 ppm, and the upconversion luminescence intensity shows a good linear relationship with ammonia gas concentration. This composite structure, which simultaneously enhances the fluorescence intensity of UCNPs and the sensing performance, can be used in biosensors.