Synthesis of highly fluorescent RhDCP as an ideal inner filter effect pair for the NaYF4:Yb,Er upconversion fluorescent nanoparticles to detect trace amount of Hg(II) in water and food samples

[Display omitted] •Based on IFE a novel fluorescent RhDCP-UCNPs mixed system was developed to detect Hg(II).•An effective mixed sensor towards Hg(II) exhibited excellent selectivity, high sensitivity.•The detection limit of Hg(II) was calculated as low as 13.5 nM.•In real samples, developed mixed nanosensor is applied for the detection of Hg(II). In the present work, a new approach is established for the selective and sensitive detection of trace amount of Hg(II) using spirolactam appended rhodamine-B based organic complex-RhDCP and upconversion-luminescent nanoparticles mixed system. Highly stable and water dispersable upconversion-luminescent nanoparticles and organic complex RhDCP was synthesized, characterized and confirmed. The developed RhDCP- upconversion-luminescent nanoparticles (NaYF4: Yb, Er) sensing probe exhibited pronounced selective enhancement in the absorption intensity and fluorescence quenching in the presence of Hg(II) ions. Based on the quantitative reaction between the (RhDCP and Hg(II)), a significant spectral overlap between the emission and absorption bands of upconversion-luminescent nanoparticles and RhDCP- Hg(II) occurred thereby resulting in inner filter effect induced emission quenching. At different optimal conditions, the RhDCP-upconversion fluorescence quenching efficiency was proportional to the concentration of Hg(II) owing to the inner filter effect. The proposed sensing strategy could sensitively detect Hg(II) as low as 13.5 nM. The practical applicability of the developed sensing method is established by carrying out sensing experiments in real sample analysis.