Colloidal quantum structures

该研究计划有两个广泛的总体目标。第一个是开发新的量子点和棒，用于具有高空间分辨率的深层组织光学成像。对于在700- 1，300 nm范围内的近红外光，预期更深的光穿透，因为这种光比UV-Vis光更少被吸收和散射。为此，最初将合成具有光致发光的高量子产率和高（光）稳定性的水分散性近红外发射PbS（e）-CdS（e）核-壳量子点和棒。他们将通过对镇静小鼠大脑中的毛细血管进行成像来进行测试，目的是在不损失光学分辨率的情况下，使其比标准的600 µm更深。量子棒在被偏振光激发后发出偏振的光致发光。这种各向异性将用于研究缓慢的（生物）过程，目前的光学探针无法执行，因为它们的激发寿命太短（纳秒），翻滚时间太快（皮秒）。在室温下，量子棒在胶体溶液中的激发态寿命为1-2 µs，翻滚时间约为20 ns，因此原则上有5-10 µs的时间窗口。还提出了基于丰富且相对无毒的元素的替代品，例如CuFeS 2。没有报道具有所需尺寸（5-10 nm）和尺寸分散控制（<5%）以及水分散性的这些的胶体合成。第二个总体目标是发展半金属的胶体合成路线，这一目标风险很大，因为文献中没有先例。半金属具有能带结构，使得只有自旋向上（或自旋向下）的电子可以传导，这使得它们对于自旋电子学非常有趣，因为它们具有潜在的100%自旋极化电流。几种不同类型的半金属被提出，（半）赫斯勒化合物是一个重要的类别。这些（半）赫斯勒化合物是三元合金，很难制造，因为它们的相图很复杂，尚未完全理解。除了该计划将产生的新纳米材料外，它无疑还将产生新的物理化学，因为量子尺寸效应取决于成分，尺寸和形状。

This research programme has two broad overall goals in mind. The first is to develop new quantum dots and rods for deep-tissue optical imaging with high spatial resolution. Deeper light penetration is expected for near-infrared light in the range of 700-1,300 nm, because this light is absorbed and scattered less than UV-Vis light. To this end, initially water-dispersible near-infrared emitting PbS(e)-CdS(e) core-shell quantum dots and rods will be synthesized with high quantum yield of photoluminescence and high (photo-)stability. They will be tested by imaging the blood capillaries in brains of sedated mice, with the aim to go deeper that the standard 600 µm without losing the optical resolution. Quantum rods send out polarised photoluminescence after excitation with polarised light. This anisotropy will be used to study slow (biological) processes, where current optical probes do not perform because their excited lifetimes are too short (nanoseconds) and their tumbling times too fast (picoseconds). The quantum rods have excited state lifetimes of 1-2 µs and tumbling times of ~20 ns at room temperature in colloidal solution, so in principle one has a 5-10 µs time window. Alternatives are also proposed based on abundant and relatively non-toxic elements, e.g. CuFeS2. There are no colloidal syntheses of these reported that have the required size (5-10 nm) and size dispersion control (<5%), and water dispersibility. The second overall goal, and highly risky because there are no precedents in the literature, is the development of colloidal synthesis routes of half-metals. Half-metals have a band structure such that only electrons with a spin up (or spin down) can be conducted, which makes them very interesting for spintronics because they have potentially 100% spin-polarised current. Several different classes of half-metals are being proposed, with the (half-)Heusler compounds being an important class. These (half-)Heusler compounds are ternary alloys that are difficult to make, because their phase diagrams are complicated and not yet fully understood. Besides the new nanomaterials that this programme will generate, it will no doubt have new physical chemistry because quantum size effects are composition, size, and shape dependent.