An update on our project inSPECtor
Rare earth elements (REE) are essential components for many modern high-tech products, ranging from wind turbines to catalysts and electrical vehicle batteries. Due to the steadily increasing need for REEs, the search for new REE deposits and the development of new characterization techniques is highly demanded. Within the KIC EIT RawMaterials, we participate in the project "inSPECtor" – integrated spectroscopy sensor system for laser-induced fluorescence and hyperspectral imaging, which aims at integrating both reflectance and photoluminescence spectroscopy sensors to improve REE exploration and mapping technique. In mid of June, the IAP together with our partner HIF ("Helmholtz Institute Freiberg for Resource Technology"), hosted a full-day project meeting attended by all project partners. A prototype of the project’s sensor system could be successfully demonstrat-ed and the roadmap for the upcoming months of project work was set up.
Besides several conference contributions, the project already published a number of full journal articles. In a first study, we combined reflectance imaging spectroscopy with extremely sensitive photoluminescence (PL) spectroscopy (sometimes also the term laser-induced fluorescence, LIF, is used), which is not yet commonly used for mineral analysis in geosciences, and applied both to natural REE-enriched mineral samples from main deposits around the world. The successful cross-validation of the results proved that our method is an innovative approach for non-invasive REE identification with increased reliability and a widened range of detectable REE.
Furthermore, we showed that laser-induced fluorescence imaging can detect and distinguish various REEs in larger and more complex geologically relevant samples such as rock pieces. With the 2D-LIF scanning we obtained an REE luminescence distribution map, which could be correlated to mineral phases (mainly apatite) by complementary SEM-EDS analysis. This work sets the basis for ongoing development of a LIF sensor for REE detection.
Some of the REE-doped materials show an interesting feature – namely long-lasting (persistent) luminescence. In a recent work, we explored the optical and persistent luminescence properties of calcium metaborate phosphor for a possible application in phototherapy. The overall luminescence properties in the host are expected to be determined by the presence/absence of defects after the introduction of dopant ions into the lattice. Upon excitation with a 254 nm UV lamp, a superlong persistent luminescence in the UVA1 region (340–400 nm, blacklight) was observed, lasting for at least 15 h, with an excellent reproducibility. The work is carried out using different approaches, combined theoretical and experimental, to understand the mechanism of such long luminescence.