Ln3+ doped nanoparticles: new optical and magnetic properties

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The lanthanides, elements La-Lu, are fascinating because of their optical and magnetic properties and their practical use permeates our society (e.g. strong magnets, MRI contrast agents). My inter- and multidisciplinary research programme will explore new directions, all based on colloidally stable (doped) nanoparticles (NPs):***1) singly doped NPs: stable single-photon sources that operate in the telecommunication window are much sought after for optical quantum computing and cryptography. Methods will be developed to dope a NP with one Er3+, which emits at 1.55 micron. Such singly doped NPs also allow to determine the photophysics of one Er3+ ion;***2) photoluminescence through two-photon excitation of doped NPs: preliminary data show that this is possible with Eu3+, Tb3+, Dy3+, and Sm3+. This is a hardly explored field and promises some new and exciting photophysics, e.g. there is theoretical work that concludes that the two-photon intra-4f transition of the Ln3+ ions is allowed, unlike the one-photon process. It may pave the way for optical correlation spectroscopy with non-overlapping emissions;***3) upconversion (core-shell) NPs that convert two or more low-energy photons into one of higher energy (usually near-infrared irradiation to red, green, and blue light) are much studied. However, the quantum yields are still much lower than their bulk counterparts, for which the reasons remain elusive. I hypothesize that the low-temperature synthesis, i.e. around 300 degrees C, of the NPs leads to internal defects that are main quenching sites. UVic's scanning transmission electron holography microscope (STEHM) will be used.***4) MRI correlation: contrast in MRI is often enhanced by adding a T1 or T2 contrast agent. It seems possible to perform magnetic resonance correlation imaging if “T1-only” and “T2-only” contrast agents can be developed. We have some data to support this hypothesis;***5) magnetic NPs as “single molecule magnets”: the field of single molecule magnets, SMMs, has made huge progress over the last two decades, but getting stable SMMs at temperatures above liquid nitrogen remains a formidable unresolved issue. I propose to make SmCo2, NdFeB, and the-like NPs. It should be possible to make these NPs large enough and still a single magnetic domain such that the blocking temperature is above liquid nitrogen;***6) the X-ray radiation dose quantification during in-vivo studies (e.g. cancer diagnosis and treatment) is an unresolved issue. I propose to make NPs that have a T2 contrast that is not susceptible to a change in its oxidation state by X-ray induced processes, e.g. Dy3+, and a T1 contrast that is and turns on by X-ray induced photo-electrons (e.g. Eu3+, which is impotent as contrast agent, to Eu2+ which is a potent T1 contrast agent). The T2 contrast then serves as an internal standard. An internal standard is necessary for one never knows how much NPs localize in a tumour because of heterogeneity.