Ln3+ doped nanoparticles: new optical and magnetic properties

镧系元素La-Lu因其光学和磁性而令人着迷，它们的实际应用渗透到我们的社会中(例如，强磁铁、磁共振造影剂)。我的跨学科和多学科研究计划将探索新的方向，所有这些都基于胶体稳定(掺杂)纳米粒子(NPs)：*1)单掺杂NPs：在电信窗口运行的稳定的单光子源在光学量子计算和密码学中非常受欢迎。将开发一种方法，在NP中掺杂一种Er3+，其发射波长为1.55微米。这种单掺杂NPs还可以确定一个Er3+离子的光物理；*2)掺杂NPs的双光子激发光致发光：初步数据表明，Eu3+、Tb3+、Dy3+和Sm3+都可以做到这一点。这是一个很难探索的领域，并有望带来一些新的令人兴奋的光物理学，例如，有理论工作得出结论，Ln3+离子的4f内双光子跃迁是允许的，不同于单光子过程。它可能为非重叠发射的光学相关光谱铺平道路；*3)上转换(核壳)纳米粒子将两个或更多低能光子转换为较高能量的光子之一(通常是近红外辐射到红、绿、蓝光)得到了大量研究。然而，量子产率仍然远远低于它们的大宗同行，原因仍然难以捉摸。我推测，NPs的低温合成，即大约300摄氏度，会导致内部缺陷，这些缺陷是主要的淬火位置。将使用UVic的扫描透射式电子全息显微镜(STEHM)。*4)MRI相关性：MRI中的对比度通常通过添加T1或T2造影剂来增强。如果能开发出“仅限T1”和“仅限T2”的造影剂，似乎就有可能进行磁共振相关成像。我们有一些数据支持这一假设；*5)磁性纳米粒子是“单分子磁体”：单分子磁体(SMM)领域在过去20年中取得了巨大进展，但在高于液氮的温度下获得稳定的SMM仍然是一个可怕的悬而未决的问题。我建议制造SmCo2、NdFeB和类似的NPs。应该有可能使这些NPs足够大，并且仍然是一个单一的磁区，以便阻止温度高于液氮；*6)体内研究(例如癌症诊断和治疗)期间的X射线辐射剂量量化是一个悬而未决的问题。我建议使NPs具有T2对比度，该对比度不受X射线诱导的过程(例如Dy3+)的氧化状态的影响，以及具有T1对比度(例如，作为对比剂无效的Eu3+与作为有效的T1对比剂的Eu2+)。然后，T2对比度作为内部标准。一个内部标准是必要的，因为人们永远不知道有多少NPs由于异质性而定位在肿瘤中。

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.