Label-free upconversion nanosensor for water safety monitoring of permanganate and dichromate ions.

Water contaminated with heavy metal ions poses serious threat to the human health and environment protection. It is imperative to develop analytical tools to detect heavy metal ions. Herein, we propose autofluorescence free SiO modified upconversion nanosensor for label-free and fast determination of MnO and CrO anions. The highly efficient and multi-colour upconversion luminescence (UCL) of UCNPs@SiO was effectively quenched by MnO and CrO anions with fast response time of 2 and 1 min, respectively. The UCNPs@SiO nanosensor exhibits linear detection ranges of 0.6-2000, 2-2000 µM with the LOD at 0.15, 0.04 µM for MnO and CrO anions, respectively. The nanosensor was successfully applied for real lake and tap water samples with satisfactory results. The UCNPs@SiO UCL nanosensor demonstrates autofluorescence free and fast determination of MnO and CrO anions with high sensitivity, good specificity, low LOD, and wide linear detection range, holding great potential for food and environmental sample sensing.