POROUS ALUMINIUM METAMATERIALS (POAMS): A VERSATILE, SELF-ASSEMBLED PLASMONIC PLATFORM

一个不断扩大的社会所面临的挑战必须通过技术进步来解决。保健和医药等具有长期重要性的问题目前需要在治疗和诊断方面取得进展，这些进展价格低廉，因此可以广泛传播。为了对环境产生较小的影响，技术进步必须从能源效率、可持续性和成本两方面考虑其影响。为了应对这些挑战，成功适应并满足当前和未来的需求，必须制造、研究和实施具有独特功能特性的新型材料。在最近的过去，由于重要的研究，在越来越小的尺寸上控制材料的结构和组成的能力已经发生了一场革命。这一点在光学超材料的制造中最引人注目，自下而上的材料设计产生了在自然存在的材料中找不到的光学特性。光学隐形和完美透镜等引人注目的现象，但这些演示掩盖了可能应用的巨大范围。在微小的尺度上，光与材料的相互作用提供了丰富有趣的现象，尽管全世界都在研究，但我们才刚刚开始意识到它的全部潜力。已经向市场提供医疗诊断的一个领域是等离子体，涉及光与金属表面和粒子的相互作用，允许它在不断减少的长度尺度上被集中和操纵。本项目旨在探索最近发现的一种基于金属纳米孔的光学超材料。制造开始使用薄铝层，将其转化为氧化铝，同时通过简单的电化学过程穿孔。这些孔的大小只有几十纳米；这些孔隙的大小和分离程度可能在过程中发生变化。通过使用简单的技术，可以在多孔层下面留下一层薄铝。然后，使用多孔模板作为掩膜并将系统暴露在氩气离子束中是一个简单的步骤。这就在下面的铝中形成了一排比光的波长小得多的孔。该工艺允许通过阳极氧化步骤对孔尺寸和分离进行广泛的控制，从而使一种新型超材料能够在深紫外到可见光谱范围内使用。这种方法是一种自组装工艺，可以很容易地产生大面积的精度，而且价格低廉。目前的研究主要使用金或银作为超材料，因为它们具有吸引力的特性，尽管它们的成本很高。该项目以铝为基础，铝是最丰富的金属，适用于许多应用。在信息技术中，克服传统电子电路面临的密度和速度限制需要使用使用光信号的光学电路。在紫外线下具有优异性能的铝可以帮助实现这一目标，因为波长更小，因此产生的设备也将更小，可能有助于实现与电子产品竞争的新型光学电路。最重要的是，这个项目的一个关键目标是确定用于检测化学和生物制剂的新型、负担得起的材料的适用性。这可以通过协助诊断和预后对医学研究产生巨大影响，这些材料具有高精度监测生物化学和化学反应的潜力，这可能会通过生物和有机分子中存在的紫外线效应得到增强。这些例子突出了光学超材料的多功能性，这些材料在尺寸和组成上可能只有微小的差异。

The challenges faced by an ever expanding society must be addressed by technological progress. Issues of longstanding importance, such as health and medicine, currently require advances in both treatment and diagnostics that are inexpensive and therefore widely distributable. In order to have minor environmental impact, technological advancements must consider their impact in terms of both energy efficiency, sustainability and cost. To meet these challenges, adapt successfully and fulfil current and future requirements, novel materials designed to have unique and functional properties must be manufactured, investigated and implemented. In the recent past, due to significant research, there has been a revolution in the ability to control the structure and composition of materials at smaller and smaller dimensions. Nowhere has this been as striking as the fabrication of optical metamaterials, where bottom-up material design produces optical properties that are not found in naturally occuring materials. Attention grabbing phenomena such as optical cloaking and perfect lensing, but these demonstrations belie the huge range of possible applications.At tiny scales, light's interaction with materials provides a wealth of interesting phenomena and despite worldwide research we are only beginning to realise the full potential. One area already delivering healthcare diagnostics to the market is plasmonics, involving the interaction of light with metal surfaces and particles, allowing it to be concentrated and manipulated at ever decreasing length scales. This project aims to explore a recently discovered type of optical metamaterial based on metallic nanoholes. The fabrication begins using thin aluminium layers which are converted into aluminium oxide and simultaneously perforated with holes by a simple electrochemical process. The holes are only a few tens of nanometres in size; the size and separation of these pores may be varied in process. By using simple techniques, a layer of thin aluminium may be left underneath the porous layer. Afterwards, it is a simple step to use the porous template as a mask and expose the system to an argon ion beam. This creates an array of holes, much smaller in size than the wavelength of light, in the underlying aluminium. The process allows broad control over the hole size and separation via the anodisation step, enabling both a new kind of metamaterial to be fabriacted for use from the deep-UV to visible spectral range. A self-assembled process, this method can easily produce large areas of incredible precision and is inexpensive.Current research primarily uses gold or silver for metamaterials due to their attractive properties despite their expense. This project is instead based on aluminium, the most abundant metal and is suitable for many applications. In IT, overcoming the density and speed limitations facing conventional electronic circuitry requires the use of optical circuitry using optical signals. Aluminium, with excellent properties in the UV can help achieve this, as the wavelength is smaller, so will be the resulting devices, potentially helping to realise new optical circuitry to compete with electronics. Most importantly, and a key objective of this project, is determining the suitability of novel, affordable materials for the detection of chemical and biological agents. This can have huge implications for medical research by assisting diagnosis and prognosis and these materials have the potential to monitor bio-chemical and chemical reactions with high precision, which may be enhanced by UV effects present in biological and organic molecules. These examples highlight the versatility of optical metamaterials that may only minute differences in dimensions and composition.