One-step synthesis of hollow PEI-NaBiF4:Yb3+/Er3+ upconversion nanoparticles for water-responsive luminescent probe

Novel PEI-modified NaBiF 4 :Yb 3+ /Er 3+ upconversion nanoparticles (UCNPs) with hollow structure were prepared by a surface modification free one-step solvothermal method and applied as a luminescent probe to determinate water content in organic solvents . XRD , SEM and HRTEM results demonstrate that the obtained PEI-NaBiF 4 :Yb 3+ /Er 3+ UCNPs are pure hexagonal phase with uniform size. The successful modification of PEI on the UCNPs surface was evidenced by ζ-potential test, XPS and TG analysis . These synthesized UCNPs are disintegrated into smaller nanoparticles in the presence of water and thus result in a surface quenching effect, which show the features of 0–100% wide range water response in various organic solvents. The sensing performance towards real samples was validated by the water content determination in beer, rum and white spirit. Furthermore, the luminescence intensity variation of the PEI-modified NaBiF 4 :Yb 3+ /Er 3+ enable the test visualization and ease of portability.