Colloidal quantum structures

这项研究计划有两个广泛的总体目标。首先是开发用于高空间分辨率的深层组织光学成像的新型量子点和量子棒。预计在700- 1300纳米范围内的近红外光的透光率会更高，因为这种光的吸收和散射比UV-Vis光要少。为此，将合成具有高光致发光量子产率和高（光）稳定性的初始水分散近红外发射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成像进行测试，目标是在不失去光学分辨率的情况下，深入到标准的600微米以下。量子棒受偏振光激发后发出偏振光。这种各向异性将用于研究缓慢的（生物）过程，目前的光学探针由于其激发寿命太短（纳秒）而翻滚时间太快（皮秒）而无法发挥作用。量子棒的激发态寿命为1-2µs，室温下在胶体溶液中的翻滚时间为~20 ns，因此原则上具有5-10µs的时间窗。也提出了基于丰富且相对无毒的元素的替代方案，例如CuFeS2。目前还没有报道这些胶体合成具有所需的尺寸（5-10 nm）和尺寸分散控制（<5%）和水分散性。第二个总体目标是开发半金属的胶体合成路线，这是高风险的，因为在文献中没有先例。半金属具有能带结构，因此只有自旋向上（或自旋向下）的电子才能导电，这对于自旋电子学来说非常有趣，因为它们可能具有100%的自旋极化电流。人们提出了几种不同种类的半金属，其中（半-）赫斯勒化合物是一类重要的半金属。这些（半）赫斯勒化合物是很难制造的三元合金，因为它们的相图很复杂，而且尚未完全了解。除了该项目将产生的新型纳米材料外，毫无疑问，它还将产生新的物理化学，因为量子尺寸效应与组成、尺寸和形状有关。

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.