Fluorine can negatively interfere with leach and smelting processes during mineral processing1,2. Real-time knowledge of the concentration and mineral hosts of fluorine in a mineral processing ore stream is important to protect process line equipment and product. Currently only offline methods of detection are available. Online sensors that determine specific fluorine-bearing mineral concentration in real-time would enable improved efficiency in processing decisions during mine production. Common excitation wavelengths used for fluorescence studies in minerals frequently provide signals that are not clearly host-specific, and hence of limited utility for mineral identification. We show that upconversion fluorescence (UF), a process in which two or more photons are absorbed and one higher-energy photon is emitted, provides a more host-specific fluorescence output, minimising spurious signals in complex environments and therefore greatly improving detection thresholds. Natural samples of fluorite (CaF2), a major fluorine host at many mine sites, have been analysed by near-infrared excitation and have revealed UF from rare earth inclusions. UF was detected in samples with rare earth concentrations as low as 1 part per million, and is therefore considered a potential new sensing modality for real-time fluorite monitoring.
Room-temperature facile synthesis of hexagonal NaYF4 and NaYF4: Yb, Er powder without any organic additives and its upconversion fluorescence properties
