Colloidal quantum structures

这项研究计划有两个总体目标。一是开发用于高空间分辨率深部组织光学成像的新型量子点和量子棒。对于700-1300纳米范围内的近红外光，预计会有更深的光穿透，因为这种光被吸收和散射的程度低于UV-VIS光。为此，首次合成了具有高光致发光量子产率和高(光)稳定性的可水分散近红外发射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，目的是在不损失光学分辨率的情况下，深入到标准600微米的深度。量子棒在偏振光的激发下发出偏振光致发光。这种各向异性将被用于研究缓慢的(生物)过程，目前的光学探测器无法执行，因为它们的激发寿命太短(纳秒)，翻滚时间太快(皮秒)。量子棒在室温胶体溶液中的激发态寿命为1-2微米S，翻滚时间约为20毫微秒，因此原则上有一个5-10微米S时间窗。还根据丰富和相对无毒的元素，如CuFeS2，提出了替代品。目前还没有报道的胶体合成物具有所需的尺寸(5-10 nm)和尺寸分散性控制(&lt；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，这一目标风险很高，因为在文献中没有先例。半金属的能带结构使得只有自旋向上(或自旋向下)的电子才能被传导，这使得它们对自旋电子学非常感兴趣，因为它们可能具有100%的自旋极化电流。几种不同类型的半金属化合物被提出，其中(半)Heusler化合物是一类重要的化合物。这些(半)Heusler化合物是很难制造的三元合金，因为它们的相图很复杂，而且还没有完全被理解。除了这个计划将产生的新的纳米材料外，它无疑还将有新的物理化学，因为量子尺寸效应是由组成、尺寸和形状决定的。

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.