Development of technological advances is important in the continually growing nanotechnology market, which is set to exceed $125 billion within the next five years. 1-dimensional (1D) nanostructures, possessing one dimension outside the nanoscale (<100 nm) range, are typically nanowires, nanofibers and nanotubes, and occupy a significant portion of this fast-growing market due to their application in sectors ranging from batteries to biomedicine. Magnetic 1D materials have become particularly popular in recent years, as their large aspect ratio and 1D structure gives rise to anisotropy, which can produce orientated electronic and ionic transport and unusual anisotropic optical and magnetic properties. As a result of these properties, magnetic 1D materials have found application in magnetic recording, lithium ion batteries, sensors, catalysis and medicine. Such 1D materials can outperform their nanoparticle (or 0-dimensional, 0D) counterparts in many applications, for example in medicine, where anisotropy leads to increased magnetisation and local magnetic field strengths. This provides improved performance in medical imaging techniques such as magnetic resonance imaging (MRI), where 1D materials boost signal enhancement compared to their 0D analogues thanks to the increased anisotropy of their 1D structures. A number of new fabrication techniques for 1D materials have hence been pioneered and developed, including templating, bottom-up growth, lithography, electrospinning, and particle assembly, though these often suffer from poor tuneability of the resulting structures, and hence properties, as well as challenges with scalability - issues which are critical for their long-term use and industrial uptake. Magnetic interactions have long been used to generate colloidal structures which respond readily to a magnetic field, with ferrofluids being the most well-known example. The preparation of permanent 1D materials using magnetic assembly approaches has been explored recently, with clusters of magnetic nanoparticles being assembled into permanent arrays of nanowires or nanotubes either during synthesis, or through magnetically stimulated nanoparticle assembly. Although successfully forming 1D nanostructures, these approaches suffer from difficulties in controlling the resulting materials' size, aspect ratio and surface chemistry. There is, therefore, a clear need for a technique capable of reproducibly fabricating magnetic 1D nanostructures with controlled and tuneable aspect ratios, sizes and surfaces, at high scales. In this proposal, we aim to achieve this through the exploitation of continuous flow technology combined with magnetic assembly to produce core-shell 1D nanostructured materials with various coatings, which can be modified with ease for numerous different applications. This work will systematically explore the effect of flow rate, magnetic field strength and duration, magnetic nanoparticle building blocks and various coating agents in order to form a library of 1D materials whose properties are tuneable and reproducible. In this way, we will develop a novel, high throughput approach to magnetic 1D nanomaterials which will have precision control over structure, aspect ratio, surfaces and hence resulting properties of the 1D materials, in addition to the benefits of scalability that come with fluid flow systems. As a case study, the produced materials will be tested for their performance as contrast agents in magnetic resonance imaging (MRI). Using state-of-the-art magnetic resonance imaging tools, quantitative assessment of performance will demonstrate the benefits of tuneable 1D materials in this important medical application.

Development of technological advances is important in the continually growing nanotechnology market, which is set to exceed $125 billion within the next five years. 1-dimensional (1D) nanostructures, possessing one dimension outside the nanoscale (<100 nm) range, are typically nanowires, nanofibers and nanotubes, and occupy a significant portion of this fast-growing market due to their application in sectors ranging from batteries to biomedicine. Magnetic 1D materials have become particularly popular in recent years, as their large aspect ratio and 1D structure gives rise to anisotropy, which can produce orientated electronic and ionic transport and unusual anisotropic optical and magnetic properties. As a result of these properties, magnetic 1D materials have found application in magnetic recording, lithium ion batteries, sensors, catalysis and medicine. Such 1D materials can outperform their nanoparticle (or 0-dimensional, 0D) counterparts in many applications, for example in medicine, where anisotropy leads to increased magnetisation and local magnetic field strengths. This provides improved performance in medical imaging techniques such as magnetic resonance imaging (MRI), where 1D materials boost signal enhancement compared to their 0D analogues thanks to the increased anisotropy of their 1D structures. A number of new fabrication techniques for 1D materials have hence been pioneered and developed, including templating, bottom-up growth, lithography, electrospinning, and particle assembly, though these often suffer from poor tuneability of the resulting structures, and hence properties, as well as challenges with scalability - issues which are critical for their long-term use and industrial uptake. Magnetic interactions have long been used to generate colloidal structures which respond readily to a magnetic field, with ferrofluids being the most well-known example. The preparation of permanent 1D materials using magnetic assembly approaches has been explored recently, with clusters of magnetic nanoparticles being assembled into permanent arrays of nanowires or nanotubes either during synthesis, or through magnetically stimulated nanoparticle assembly. Although successfully forming 1D nanostructures, these approaches suffer from difficulties in controlling the resulting materials' size, aspect ratio and surface chemistry. There is, therefore, a clear need for a technique capable of reproducibly fabricating magnetic 1D nanostructures with controlled and tuneable aspect ratios, sizes and surfaces, at high scales. In this proposal, we aim to achieve this through the exploitation of continuous flow technology combined with magnetic assembly to produce core-shell 1D nanostructured materials with various coatings, which can be modified with ease for numerous different applications. This work will systematically explore the effect of flow rate, magnetic field strength and duration, magnetic nanoparticle building blocks and various coating agents in order to form a library of 1D materials whose properties are tuneable and reproducible. In this way, we will develop a novel, high throughput approach to magnetic 1D nanomaterials which will have precision control over structure, aspect ratio, surfaces and hence resulting properties of the 1D materials, in addition to the benefits of scalability that come with fluid flow systems. As a case study, the produced materials will be tested for their performance as contrast agents in magnetic resonance imaging (MRI). Using state-of-the-art magnetic resonance imaging tools, quantitative assessment of performance will demonstrate the benefits of tuneable 1D materials in this important medical application.

The smallest scale on which it is possible to design functional devices, including electronics, is the molecule scale (about 100,000 times smaller than the width of a human hair). This is the ultimate limit for miniaturisation and motivates research to manipulate and study the properties of individual molecules for applications in, e.g., information technologies and sensors. It is also the scale at which quantum phenomena dominate properties, so single-molecule structures offer a domain for investigations ranging from fundamental tests of quantum theory to developing components for future quantum technologies. To realise such experiments and technologies, it is necessary to incorporate individual molecules into electrical circuits. This is challenging because the typical size of a useful functional molecule is much smaller than the smallest wires that it is possible to fabricate, even with the most sophisticated lithography systems available today. Most researchers use one of two approaches. The first uses an electrical current or mechanical strain to make a tiny gap, a few nanometres across, in a thin wire, and then deposit the molecules of interest randomly, hoping that one and only one bridges the gap. This method relies on chance, and so it very rarely yields a working device: typically, only a very small proportion of devices fabricated show behaviour consistent with a single molecule in the gap and, because the shape of the gap and the orientation of the molecule are uncontrolled, it is rare for even such "working" devices to exhibit reproducible properties. The second method uses a scanning tunnelling microscope to locate and investigate molecules that are deposited on a conducting surface. This process is much more reliable and reproducible than the break junction method but it involves bulky experimental apparatus and it tightly limits the experimental geometry, ruling out the development of more complicated experiments or practical devices. These limitations in the existing methods have hamstrung the development of molecule-scale devices and technologies. Further progress in this field now requires the development of controlled and reliable methods that can be scaled to high volume production. This project will provide this methodology and demonstrate a range of prototype molecular devices. Our approach is based on DNA nanotechnology, which has, over the last decade, proved itself to be a powerful tool for controlled self-assembly of structures at the molecular scale. We will use these methods to direct the assembly of "packages" about 100 nanometres across. Constructed mainly from DNA with a precisely programmed structure, these packages will position gold nanoparticle contacts and the "target" molecular components, whose electrical transport properties we would like to exploit, with sub-nanometre accuracy. Our method produces trillions of packages at a time in a test-tube and ensures that each one has exactly the correct molecules incorporated in the correct positions and orientations between contacts. These gold nanoparticle contacts are large enough that we can connect them to laboratory equipment using standard nanolithography techniques. The technology has the potential for future development to connect multiple molecules in three-dimensional device architectures, and for the assembly of large-scale integrated molecular circuits. We propose to create several families of devices, designed to develop and prove this radically new molecular device fabrication methodology. These devices will give us an unprecedented experimental tool for probing electrical and magnetic properties of molecules, but they will also establish the potential for the industrial deployment of our technology. Central to the project are close interactions with industrial partners and knowledge transfer activities designed to accelerate commercial applications.

Electrons flowing through semiconductor devices are of immense importance in modern life. When devices are made sufficiently small, such that one of the dimensions is in the nanometre regime, the quantum nature of the electron comes to the fore and must be considered in detail. Working at very low temperatures reduces the mutual electron-electron scattering and results in the wave nature of electron transport becoming observable over distances which can exceed the size of the device. Experiments using devices which are smaller than the coherence length of the wavefunction, or the distance between impurity scattering events, have allowed observation of a range of quantum effects. In recent years theories have proposed that a "quantum computer" has certain advantages over conventional computers as they allow a massively parallel mode of operation. This is based on quantum principles, thus if two electrons are in a quantum state then their total spin wavefunction reflects the range of possible states that can be present. It is this superposition of states which is the basis of a quantum computer. It is a purely quantum phenomenon and has given rise to concepts such as "Schrodinger's Cat" which exemplify the non-intuitive nature of quantum mechanics. Another property which could give rise to new technological applications is the remarkable entanglement. This purely quantum effect results in two electrons being in the same quantum state and "knowing" about each other's existence, consequently if the spin of one is rotated then the spin of the other is affected despite there being a considerable distance between them. In this work we propose to utilise semiconductor nanostructures to find new quantum effects and combine them to create integrated quantum circuits for practical exploitation. The project integrates theory, semiconductor growth/fabrication and measurements in three different centres, it has as initial targets the design and fabrication of key quantum components forsubsequent integration. A principal component is the Quantum Pump which can transmit controlled numbers of electrons at high frequencies with very high accuracy. This device can be used for the generation of entangled electrons which can then be investigated and put to use. Another component which is of importance is the electronic analogy of the polarising beam splitter in optics, here by using localised electron spins an incoming electron is either transmitted or reflected depending on its spin direction. We also propose to exploit the spin-orbit coupling which allows a spin polarised current to be established in a nanostructure which can then be utilised in a quantum device. It is further proposed to build on the use of an indirect electron interaction mechanism to transmit spin information between different devices. A system which may have novel properties in this regard is the incipient Wigner lattice which can form when a line of electrons is weakly confined and minimisation of the electron-electron repulsion forces the electrons to form two separate rows. Here they can be entangled and constitute a continuous supply of entangled electrons in a manner which is complementary to the pump. New types of quantum components will be developed. They will then be integrated to form an early type of circuit in which quantum effects dominate the properties. It is intended to develop basic quantum processors in particular a CNOT gate in which the spin of an electron is rotated depending on the direction of the spin of another. In addition to these objectives a number of spin-off achievements will have an impact on other fields. For example it will be necessary to develop techniques of measurement of electronic properties at ultra low temperatures, 1 milliKelvin, and the spin polarised currents to be developed will have applications in the important field of spintronics.

The terahertz (THz) frequency region within the electromagnetic spectrum, covers a frequency range of about one hundred times that currently occupied by all radio, television, cellular radio, Wi-Fi, radar and other users and has proven and potential applications ranging from molecular spectroscopy through to communications, high resolution imaging (e.g. in the medical and pharmaceutical sectors) and security screening. Yet, the underpinning technology for the generation and detection of radiation in this spectral range remains severely limited, being based principally on Ti:sapphire (femtosecond) pulsed laser and photoconductive detector technology, the THz equivalent of the spark transmitter and coherer receiver for radio signals. The THz frequency range therefore does not benefit from the coherent techniques routinely used at microwave/optical frequencies. Our programme grant will address this. We have recently demonstrated optical communications technology-based techniques for the generation of high spectral purity continuous wave THz signals at UCL, together with state-of-the-art THz quantum cascade laser (QCL) technology at Cambridge/Leeds. We will bring together these internationally-leading researchers to create coherent systems across the entire THz spectrum. These will be exploited both for fundamental science (e.g. the study of nanostructured and mesoscopic electron systems) and for applications including short-range high-data-rate wireless communications, information processing, materials detection and high resolution imaging in three dimensions.