Fig. 5: Study on the sensing performance.

A, B Under 365 nm excitation, emission spectra of R-Eu-Et-1/2. C, D Luminescence intensity comparison of R-Eu-Et-1/2 solutions after adding different metal ions (insets in C, D: photos of R-Eu-Et-1/2 photoresponses to different metal ions under 365 nm UV-light). Concentration-dependent spectra and fitting curves of R-Eu-Et-1/2 on Cu^II ions under excitation at 365 nm (E and G for R-Eu-Et-1, F, and G for R-Eu-Et-2). H Performance comparison of R-Eu-Et-1/2 and different types of materials reported for Cu^II ion sensing. I Molecular ion peaks and analytical results of the HRESI-MS of R-Eu-Et-1 before and after adding Cu^II ions. J Schematic diagram of the photoresponses of R-Eu-Et-1 or R-Eu-Et-2 to heavy metal ion Cu^II. Note: The yellow ball represents the series of hydrogen bonds/metal-organic framework; the pink ball represents the series of quantum dots; the purple ball represents the series of nanoparticles; the red star represents this work; The shade of red represents the glow color of R-Eu-Et-1 or R-Eu-Et-2.