A portable smartphone-integrated microcavity sensor based on rhodamine 6G-functionalized carbon dots for ratiometric determination of Cu2+ and glyphosate

The increasing persistence of harmful ions and pesticide residues has been a matter of concern due to their pernicious and ubiquitous impact on environmental processes. Herein, we design a ratiometric fluorescent platform for the cascade identification of Cu²⁺ and glyphosate, which is devised by grafting rhodamine 6G onto F, N-doped carbon dots (F, N-CDs@Rh6G). The formation of F, N-CDs@Rh6G/Cu²⁺ chelation complex induces fluorescence quenching at 438 nm, attributed to static complex formation and photoinduced energy transfer. Subsequently, the introduction of glyphosate reverses the binding priority of the chelated complex and results in the recovery of fluorescence signal at 438 nm, while the reference peak (558 nm) remains relatively stable. Under optimal conditions, the fluorescent probe exhibits the low detection limits (LODs) for Cu²⁺ (61 nM) and glyphosate (53 nM). Additionally, a portable microcavity sensing platform combining with smartphone is devised for visual and on-site quantification of Cu²⁺ and glyphosate with the exceptional LODs. Therefore, this newly microcavity with F, N-CDs@Rh6G provides a reliable cascade sensing platform for Cu²⁺ and glyphosate determination, showcasing potential applications.