The purpose of this project is the development of novel strategies to manufacture devices that render the unauthorised duplication or falsification more difficult. With the rapidly increasing quality of publicly available replication technology (e.g. colour printers and photo-copying machines), the counterfeit of bank notes and identity documents is becoming and increasing problem. To counteract this field of organised crime, new approaches to manufacture security documents are necessary.In a collaboration with the world's largest security printer and paper maker, De La Rue, the objective of this project is to develop novel devices for security documents. Based on techniques that are available in Prof. Steiner's laboratories, surface patterns will be developed that show a brilliant coloured effect that change when the angle of illumination or observation is changed. This effect arises from the interference of white light on a surface with a micrometre-sized dielectric pattern. To achieve this a combination of strategies are planned, including the use of fluorescent nanoparticles, multilayer structures, lateral gratings, etc., all deposited by spin-coating, or soft lithographic methods.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

The ancient art of casting but at the nano-metre scale is being used by our team at the University of Southampton to develop ultra sensitive detectors which are being tested for health screening, and programmable coloured fabrics. Our team of nano-scientists have developed the technique of nano-casting to make nano scale gold structures that enable detection by light of tiny numbers of molecules. The Mesopotamian civilization made moulds from sand to cast molten copper. We use nano-scale plastic spheres for moulds and electroplating techniques to build up our structures. The spheres are suspended in water, a drop of which is evaporated on gold-coated glass leaving a single layer of spheres. The gold is then grown up around the ball 'mould' using electroplating techniques. Finally the balls are dissolved leaving a gold metal structure with 'nano-dishes' and cavities.It is the optical properties of the structure that are key. The tiny cavities are on the scale of the wavelength of light, so they trap the light and concentrate its energy with extraordinary efficiency. The concentrated energy enhances a phenomenonknown as Raman scattering more than a million-fold enabling the reliable detection of molecules at very low concentrations. But the exact way that light is trapped inside these cavities (in a form called a 'plasmon') is still somewhat mysterious, as it is extremely hard to predict. Our project here is to understand and develop the plasmons which can be colour-tuned over the entire spectrum. To do this we can play tricks with a large variety of metals, cavity shapes, and over-coatings.Several applications are in prospect:Raman scattering produces a kind of molecular fingerprint when light in the form of a laser is focused on a sample. The vibrating bonds of the molecules in the sample absorb some of the light and 'scatter' it so that the light emitted from the sample changes colour in a characteristic way depending on the molecules present. A Raman spectrometer is used to measure this effect with the output being a spectrum of the scattered Raman light. The problem however is that Raman scattering is very weak, hard to detect, and on its own is of little practical use in diagnostics. Our gold nano materials amplify Raman scattering so that the molecular fingerprints can easily be detected even when only tiny traces ofsubstances are present. Repeating measurements on the same sample gives the same results within a few per cent, whereas previously huge variations are observed. Such accuracy is obviously vital when screening patients. There are many applications for seeing molecules sensitively. Understanding how molecules bind to surfaces is key for unraveling the mysteries of catalysis (a multi-billion industry). And environmental monitoring of pollutants or bio-hazard detection rely on such possibilities. Diagnosing conjunctivitis using this technique on tears from patients could save the NHS an estimated 471m over 10 years through savings in drugs, laboratory time and the number of patient visits. And there are many other possible diseases including hepatitis, HIV, diabetes and chlamydia that it might be possible to spot in your tears.Another prospective application is in producing low cost solar cells, which can be extremely thin and coated onto plastics. Using the organically-coated gold nano-cavities, light can potentially be very efficiently absorbed and the energy extracted, but we have to ascertain how effective this process can be made.A final intriguing possibility is in making thin films which are strongly coloured, but don't use toxic and carcinogenic dyes. By stretching the films, or connecting them to a battery, their colour can potentially be changed. Hence we plan to test thelimits to this new tuneable colour from our structures.

For the past 5 years our team has been developing plastic films incorporating polymer nanoparticles that when correctly processed show structural colour. Most coloured materials depend on pigments that selectively absorb particular colours, and these are frequently toxic and fade over time. Creating colours that can change on demand is currently impractical for most markets. The materials that we create produce colours based exclusively on the nanoscale spacing of transparent components, and actively change colour if stretched or swelled. The prospect is thus for a materials-based company selling suitably-tailored coloured films into a variety of markets.Our aim is thus to formulate and develop the business case for a spin-out company based on elastomeric polymer opals which use our novel manufacturable nanotechnology.

Visible light can be made to interact with new solids in unusual and profoundly different ways to normal if the solids are built from tiny components assembled together in intricately ordered structures. This hugely expanding research area is motivated by many potential benefits (which are part of our research programme) including enhanced solar cells which are thin, flexible and cheap, or surfaces which help to identify in detail any molecules travelling over them. This combination of light and nanoscale matter is termed NanoPhotonics.Until now, most research on NanoPhotonics has concentrated on the extremely difficult challenge of carving up metals and insulators into small chunks which are arranged in patterns on the nanometre scale. Much of the effort uses traditional fabrication methods, most of which borrow techniques from those used in building the mass-market electronics we all use, which is based on perfectly flat slabs of silicon. Such fabrication is not well suited to three-dimensional architectures of the sizes and materials needed for NanoPhotonics applications, and particularly not if large-scale mass-production of materials is required.Our aim in this programme is to bring together a number of specialists who have unique expertise in manipulating and constructing nanostructures out of soft materials, often organic or plastic, to make Soft NanoPhotonics devices which can be cheap, and flexible. In the natural world, many intricate architectures are designed for optical effects and we are learning from them some of their tricks, such as irridescent petal colours for bee attraction, or scattering particular colours of light from butterfly wings to scare predators. Here we need to put together metal and organics into sophisticated structures which give novel and unusual optical properties for a whole variety of applications.There are a number of significant advantages from our approach. Harnessing self-assembly of components is possible where the structures just make themselves , sometimes with a little prodding by setting up the right environment. We can also make large scale manufacturing possible using our approach (and have considerable experience of this), which leads to low costs for production. Also this approach allows us to make structures which are completely impossible using normal techniques, with smaller nanoscale features and highly-interconnected 3D architectures. Our structures can be made flexible, and we can also exploit the plastics to create devices whose properties can be tuned, for instance by changing the colour of a fibre when an electrical voltage is applied, or they are stretched or exposed to a chemical. More novel ideas such as electromagnetic cloaking (stretching light to pass around an object which thus remains invisible) are also only realistic using the sort of 3D materials we propose.The aim of this grant is bring together a set of leading researchers with the clear challenge to combine our expertise to create a world-leading centre in Soft NanoPhotonics. This area is only just emerging, and we retain an internationally-competitive edge which will allow us to open up a wide range of both science and application. The flexibility inherent in this progamme grant would allow us to continue the rapid pace of our research, responding to the new opportunities emerging in this rapidly progressing field.