Surface lanthanide activator doping for constructing highly efficient energy transfer-based nanoprobes for the on-site monitoring of atmospheric sulfur dioxide

The sensitive and on-site detection of sulfur dioxide (SO 2 ) is in great demand in the fields of food safety and environmental protection. Here, we developed a novel upconversion nanoprobe based on the luminescence energy transfer mechanism for monitoring the atmospheric SO 2 concentrations. The lanthanide emitters, Tm 3+ ions, were optimized to be doped on the surface layer of the upconversion nanoparticles to improve their energy transfer efficiency by minimizing the distance between the emitters and the surface quencher, a cyanine dye. As a proof-of-concept, the optimal nanoprobe was utilized to detect SO 2 water derivatives, bisulfite ions, exhibiting a linear luminescence increase in the range of 1 nM to 10 nM. Furthermore, we assembled the cyanine-modified upconversion nanoparticles onto a test paper, and used a smartphone-based detection platform to achieve portable and visual detection of SO 2 . The test paper showed a strong luminescence stability, homogeneity and good anti-interference. The limit of detection for SO 2 gas was found to be 1 ng L −1 . This novel upconversion test paper was also demonstrated to directly monitor the concentration of SO 2 gas in atmosphere. A highly efficient, energy transfer-based upconversion nanoprobe was developed, which allowed a portable and visually intuitive detection of gaseous SO 2 by use of a smartphone-based detection platform.