NMR as a Probe of the Homogeneity of Paramagnetic Doping/Substitution

NMR 作为顺磁掺杂/取代均匀性的探针

• 批准号: 517406651
• 负责人: Professor Dr. Jörn Schmedt auf der Günne
• 金额: --
• 依托单位: Arbeitskreis Anorganische Materialchemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/517406651?language=en
• 关键词: NMR; Probe; Homogeneity; Paramagnetic; Doping

Defects in crystalline structures may be used to change, adjust and control the materials properties of the host. Among the properties which can be influenced by doping is luminescence efficiency. Quenching is more efficient if the excited state is transported radiationless over a chain of doped paramagnetic atoms to so-called killer sites, which convert the excited state to the ground state and heat. Obviously the efficiency of quenching depends on the spatial distribution of dopands in the host structure. Thus a homogeneously doped sample should have better luminescence properties than a heterogeneously doped sample at a lower doping concentration. As shown in recent publications doping homogeneity can be evaluated on a scale of approx. 0.5 nm to 2 nm using the relative visibility of the NMR-active nuclei. The method is based on the decay of the contribution of the “NMR-visible” sample with rising doping concentration.The target of this project is to test the hypothesis that doping homogeneity as probed by solid-state NMR has a positive influence on luminescence properties. The planned experiments were designed, to answer the following questions.How does the “NMR-visible” sample volume relate to the electronic state of the dopant, the degree of homogeneity and temperature?How do luminescent properties depend on doping homogeneity?An important insight from prior work was the insight, that NMR probes doping homogeneity on the same length scale as the one required for radiationless transport.A requirement for this project is the phase-pure synthesis of doping series of crystalline host compounds. Lanthanides were chosen as the sole dopands deliberately, in order to reduce the influence of the chemical surrounding and to ease finding explanations for the results. For the successful application of the method the only requirement is the availability of an NMR signal of an arbitrary nucleus. Thus the method may be used for the characterization of a number of substance classes, e.g. of silicates (Si-29), halogenides (F-19, Cl-35/37, Br-79/81), nitrides (N-14/15), phosphates (P-31), borates (B-10/11) or aluminates (Al-27).

晶体结构中的缺陷可用于改变、调整和控制主体的材料性质。在这些性质中，可以受掺杂影响的是发光效率。如果激发态在掺杂的顺磁原子链上无辐射地传输到所谓的杀手位点，将激发态转换为基态和热量，则淬灭更有效。显然，猝灭的效率取决于掺杂物在主体结构中的空间分布。因此，在较低掺杂浓度下，均匀掺杂的样品应当比非均匀掺杂的样品具有更好的发光性质。如在最近的出版物中所示，掺杂均匀性可以在大约100 μ m的尺度上评估。0.5使用NMR活性核的相对可见度，将波长从2nm调整到2nm。该方法是基于“NMR可见光”样品的贡献随掺杂浓度的增加而衰减。本项目的目标是测试通过固态NMR探测的掺杂均匀性对发光特性具有积极影响的假设。设计了计划的实验，以回答以下问题：“NMR-可见”样品体积与掺杂剂的电子状态、均匀度和温度有何关系？发光特性如何取决于掺杂均匀性？从以前的工作的一个重要的见解是洞察力，NMR探针掺杂均匀性在相同的长度尺度上所需的无辐射传输。该项目的要求是相纯合成的掺杂系列的晶体主体化合物。为了减少化学环境的影响，并便于对结果进行解释，特意选择镧系元素作为唯一的掺杂剂。为了成功地应用该方法，唯一的要求是任意核的NMR信号的可用性。因此，该方法可用于表征许多物质类别，例如硅酸盐（Si-29）、卤化物（F-19、Cl-35/37、Br-79/81）、氮化物（N-14/15）、磷酸盐（P-31）、硼酸盐（B-10/11）或铝酸盐（Al-27）。