Fluorescent paper-based analytical devices

Fluorescent paper-based analytical devices (FL PADs) are receiving increasing attention in recent years, owing to the development of new technologies for the fabrication of brighter fluorophores and phosphors, especially nanomaterials. This chapter covers recent advances in the construction of FL PADs for qualitative and quantitative assays. It commences by introducing the most often used fluorescent probes, including organic dyes, quantum dots, carbon dots, upconversion nanoparticles, and their use as reporters. The second part presents the fluorescence response produced by the PADs, which can be either brightness-based (“turn-on” and “turn-off”) or color-based (ratiometric fluorescence). We approach the different signal responses by presenting recent examples of developed FL PADs, exploring their advantages and limitations, and describing their fabrication technologies and sensing mechanisms.