Nanoparticles based on uoride hosts are an emerging class of materials with promising applications in biomedical imaging and the treatment of various diseases. Trivalent europium doped into calcium uoride nanoparticle hosts have been synthesised by various methods and investigated with high resolution laser spectroscopy, dynamic light scattering (DLS), and ultravioletvisible (UV-VIS) spectroscopy.

DLS showed samples synthesised by thermal decomposition had the narrowest size distribution, with core-only nanoparticles measuring 9.2nm and core-shell nanoparticles measuring 12.6 nm. Samples produced by co-precipitation and hydrothermal methods had larger sizes and broader distributions, 42.3nm and 16.6nm respectively.

UV-VIS spectroscopy identi ed considerable Eu³⁺ Eu²⁺ reduction under various synthesis strategies. The mechanism which maximises this process is high temperature synthesis in the presence of oleylamine. Temperature and reductive environments in isolation encourage the reduction as well, but not to the same degree. UV-VIS spectroscopy was also used to characterise the e ect of annealing nanoparticles prepared by co-precipitation. Annealing at 680K yieled white phosophor-like behaviour but with only a single precursor ion.

High resolution laser spectroscopy has been used to investigate the site distribution in various calcium uoride nanoparticles. Both core-only and core-shell nanoparticles synthesised by thermal decomposition are dominated by C4v crystal site symmetry. Cluster sites have also been observed, and have been assigned to the Q cluster site seen in bulk calcium uoride crystals. The process of shelling nanoparticles in an inert calcium uoride layer quenches any low symmetry surface site uorescence. Samples prepared by hydrothermal methods are dominated by cluster sites, suppressing any C4v sites. The presence of a cubic (Oh) site was also observed. The cluster sites observed are in agreement with the two cluster sites, R and Q, in the bulk crystal. Nanoparticles prepared by co-precipitation have both C4v and Oh symmetry, with minimal cluster sites observable. All four sites observed in bulk calcium uoride crystals have been accounted for across all the nanoparticles synthesised indicating remarkable bulk-like characteristics despite being on the nanoscale.

Temporal dynamics were investigated with high resolution laser spectroscopy for hydrothermal and thermal decomposition synthesised nanoparticles. C4v centres in thermal decomposition nanoparticles showed long 5D0 ! 7F1 lifetimes of 17.8 ms for core-shell and 16.8 ms for core-only samples. Fluoresence of the Q centre had a much shorter lifetime of 3.7 ms. Samples produced by hydrothermal methods showed much longer lifetimes for the 5D0 ! 7F1 transition arising from the Q centre, with lifetimes of 14.4 ms. Radiative and non-radiative components of decay were also calculated for the 5D1 energy level in core-shell nanoparticles prepared by thermal decomposition, with rates of 380 s􀀀1 and 47 s􀀀1 respectively.