Self-assembled gold nanoparticle chains for nanoplasmonics

制造具有小尺度结构和多组分的新材料预计在传感，数据存储，电子和催化等广泛的应用中具有重要意义。小规模结构可能取得重大突破的一个新领域是围绕光学电路的光通道。沿着玻璃纤维沿着引导光是一种快速有效的信息传输方式，但受限于所用电缆的尺寸，因为光的波长约为半微米，因此一旦在纤维中达到这一尺度，就会发生衍射。为了让光通过更小的导线，需要在材料中诱导电子效应，目前的方法是使用与光相互作用的小电介质或金属图案，以便它们能够沿着特定方向限制和引导光。这些光学电路通过金属表面电子中的光诱导局部激发（所谓的等离子体激元）来工作，并且可以通过图案化工艺（光刻）来产生。尽管这些等离子体激元器件已经被示出为有效地限制和引导光学信息，但是由于通过光刻技术制备非常小（纳米级）和复杂的图案的困难，它们在尺寸上仍然受到限制。此外，它们在沿结构沿着传播期间往往会耗散大量的光。拟议的研究计划旨在探索纳米等离子体的新方法。我们将使用自下而上的自组装方法，而不是通过自上而下的光刻来制备小的金属结构，该方法涉及将非常小的金纳米颗粒自发排列成线性链。通过这种方式，我们解决了所需的小尺寸问题，因为我们可以预先使用化学合成来制造金纳米颗粒，从而使我们能够微调尺寸。例如，它是相对容易制备的金纳米粒子的大小为5，10，20纳米等什么是特别新颖的关于我们的工作是，我们已经发现了一种方法，诱导纳米粒子排队像珠串，当他们这样做，他们的光学性质发生了巨大的变化，因为光可以传播的纳米粒子链。我们现在想探索如何控制这种组装，以产生直链或支链，具有不同长度，或包括其他类型的纳米颗粒，如荧光或磁性纳米颗粒。我们还想把这些链嵌入到液晶阵列中，这样我们就可以通过液晶矩阵的电开关来改变光沿着链传播的方向。最后，我们有一些非常先进的技术（光子扫描隧道显微镜和近场扫描光学显微镜）和数学方法，使我们能够理解我们的新方法的基础物理。总之，所有这些实验应该使我们能够在非常小的尺度结构中开拓光学制导的新思想和方法。一旦我们了解了这些系统的工作原理，那么就有可能利用这些结果来开发新型的纳米级设备，这些设备可以用作低成本，超紧凑和灵敏的分析设备，用于医疗保健，食品控制和药物跟踪，以及由光学处理驱动的超高速计算机。

Making new materials that have small scale structures and multiple components is expected to be of great importance in a wide range of applications such as sensing, data storage, electronics and catalysis. One new area where small-scale structures could make a significant breakthrough is in the channelling of light around optical circuits . Guiding light along a glass fibre is a fast and efficient means of sending information but is limited by the size of the cables used because light has a wavelength of around half a micrometer, so once this scale is reached in the fibre then diffraction occurs. To get light to travel through smaller wires one needs to induce electronic effects in the material, and the current way of doing this is to use small dielectric or metallic patterns that interact with the light such that they are able to confine and guide the light along particular directions. These optical circuits work by light-induced localized excitation in the surface electrons of the metal (so-called plasmons), and can be produced by patterning processes (lithography). Although these plasmonic devices have been shown to efficiently confine and channel optical information, they remain restricted in size because of the difficulty of preparing very small ( nanoscale ) and complex patterns by lithographic techniques. Moreover, they tend to dissipate a lot of the light during propagation along the structures. The proposed research programme intends to explore a new approach to nanoplasmonics . Instead of preparing the small metallic structures by top-down lithography, we will use a bottom-up self-assembly approach involving the spontaneous alignment of very small gold nanoparticles into linear chains. In this way, we get round the problem of the small size required because we can make the gold nanoparticles beforehand using chemical synthesis that allows us to fine-tune the size. For example, it is relatively easy to prepare gold nanoparticles with sizes of 5, 10, 20 nm etc. What is particularly novel about our work is that we have discovered a method for inducing the nanoparticles to line up like beads on a string, and when they do this, their optical properties change dramatically because light can propagate down the nanoparticle chains. We now want to explore how we can control this assembly to produce chains that are straight or branched, have different lengths, or include other types of nanoparticles in them such as fluorescent or magnetic nanoparticles. We also want to embed the chains in a liquid crystalline array so that we can change the direction of light propagation along the chains by electrical switching of the liquid crystal matrix. Finally, we have some very advanced techniques (photon scanning tunnelling microscopy and near-field scanning optical microscopy), and mathematical methods that will allow us to understand the underlying physics of our new approach. Together, all these experiments should allow us to pioneer new ideas and methods in optical guidance in very small scale structures. And once we understand how these systems work, then it should be possible to use the results to develop new types of nanoscale devices that could be used as low cost, ultra-compact and sensitive analytical devices for use in health care, food control and drug tracking, as well as in super-fast computers driven by optical processing.