The objective of this study is to examine core-shell type plasmonic metamaterials aimed at the development of materials with unique electromagnetic properties. The building blocks of metamaterials under study consist of gold as a metal component, and silica and precipitated calcium carbonate (PCC) as the dielectric media. The results of this study demonstrate important applications of the core-shells including scattering suppression, airborne obscurants made of fractal gold shells, photomodification of the fractal structure providing windows of transparency, and plasmonics core-shell with a gain shell as an active device. Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction. Significant extinction from the visible to mid-infrared makes fractal shells very attractive as bandpass filters and aerosolized obscurants. In contrast to the planar fractal films, where the absorption and reflection equally contribute to the extinction, the shells' extinction is caused mainly by the absorption. This work shows that the Mie scattering resonance of a silica core with 780 nm diameter at 560 nm is suppressed by 75% and only partially substituted by the absorption in the shell so that the total transmission is noticeably increased. Effective medium theory supports our experiments and indicates that light goes mostly through the epsilon-near-zero shell with approximately wavelength independent absorption rate. Broadband extinction in fractal shells allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. Au fractal nanostructures grown on PCC flakes provide the highest mass normalized extinction, up to 3 m^2/g, which has been demonstrated in the broad spectral range. In the nanoplasmonic field active devices consist of a Au nanoparticle that acts as a cavity and the dye molecules attached to it via thin silica shell as the active medium. Such kind of devices is considered as a nano-laser or nano-amplifier. The fabricated nanolasers were studied for their photoluminescence kinetic properties. It is shown that the cooperative effects due to the coupling of dye molecules via Au nanoparticle plasmons result in bi-exponential emission decay characteristics in accord with theory predictions. These bi-exponential decays involve a fast superradiant decay, which is followed by a slow subradiant decay. To summarize, this work shows new attractive properties of core-shell nanoparticles. Fractal Au shells on silica cores prove to be a good scattering suppressor and a band pass filter in a broadband spectral range. They can also be used as an obscurant when PCC is used as the core material. Finally, gold nanoparticles coated with silica with dye results in bi-exponential decays.

Emerging electronic system architectures follow increasingly 3D integration concepts driven by further miniaturization, increase of performance, decrease of energy consumption, and implementation of further functionality. Following this More than Moore path, trendsetting on-top-of-complementary metal-oxide semiconductor (CMOS) technologies for nanodevices find increasing attention in semiconductor development roadmaps. Nanodevices implemented through nanomaterials such as semiconducting single-walled carbon nanotubes (CNTs) with their proceeded technology readiness level, give additional degree of freedom to upgrade such systems as substrate-independent and post-CMOS compatible technologies are already available. Although, they inherently feature extraordinary properties several technological obstacles are not yet addressed. Pronounced obstacles like inadequate CNT assembly structure, interfering parasitic effects related to CNT/substrate interfaces, as well as insufficient pre-stress state of the CNTs are tackled within this thesis aiming on CNT-based piezoresistive sensors. Following a holistic approach, the activities range from the implementation of chromatography-based length separation of CNTs over wafer-level micro- and nanotechnological process-, module-, and equipment developments towards comprehensive and statistical data analysis. It could be shown, that short CNTs adversely affect integrability and reproducibility, underlined by a 25% decline of the fabrication yield of CNT based field-effect transistors (CNT-FETs) with respect to long CNTs. It furthermore turns out, that performance of CNT-FETs built from long CNTs show significant benefits in terms of subthreshold swing (up to 163%) and hole mobility (up to 300%), which could be explained by suppressed CNT chain formation within the transistor channel. Furthermore, short-channel piezoresistive CNT sensors in FET configuration show a significant drain-induced barrier thinning characterized by a degradation of the subthreshold swing and a threshold voltage roll-off of (−1370± 130) mV · V−1 upon applied drain-source voltage. This device-specific effect enhances the intrinsic strain-sensitivity of the sensor of up to 150% with a maximum measured gauge factor of 800. In this regard, supporting transport simulations underline the importance of the Schottky barrier at the source/CNT junction as the dominating junction for tunneling currents responsible for the gained enhancement. Finally, a technology module was developed, which further reduce parasitic effects such as stick-slip and slack behavior of device-integrated CNTs upon mechanical load by incorporation of layout-determined pre-strain. Utilizing a post-CMOS compatible sacrificial layer approach combined with residual stressed membranes, the integrated CNTs were strained by almost 1% in axial direction. This consequences in an reduced sensor offset determined by a reduction of the detection limit to 30 MPa. In addition this modul was successfully implemented by heterogeneous on-top-of application-specific integrated circuit technologies where CNT-FETs were characterized over an embedded complementary metal-oxide semiconductor multiplexer circuit. Hence, this work displays novelty and provides significant contributions on heterointegrated system-on-chip applications of upcoming nanomaterial-based devices for environmental sensing, condition monitoring, photonic integrated circuits, up to promising architectures for neuromorphic computing and the quantum technology science and application.

Im Rahmen dieser Arbeit wurde die Möglichkeit untersucht, eine bestimmte Klasse von Pestiziden mit einem Lateral-Flow-Test als Plattform und einem Smartphone-Setup für die Signalerkennung nachzuweisen. Konkret handelt es sich bei Typ-I-Pyrethroiden um Insektizide, die zur Bekämpfung von Stechmücken eingesetzt werden, die z.B. Überträger von Viruserkrankungen sein können. Permethrin und Phenothrin, die bekanntesten Pyrethroid-Verbindungen, werden seit einiger Zeit zur Desinfektion von Flugzeugen auf Flügen aus und in tropischen Gebieten verwendet, um die Ausbreitung gefährlicher Krankheiten wie Malaria, Zika oder Dengue zu verhindern. Da es immer noch keine Kontrolle über die Menge der an Bord versprühten Insektizide gibt, wird eine neue effektive und schnelle Methode zur Analyse von Pyrethroiden direkt im Flugzeug benötigt. Zu diesem Zweck wurde ein tragbarer Test im Lateral-Flow-Assay- (LFA-) Format realisiert, bei dem gegatterte Antikörper-Indikator-Freisetzungssysteme zum Nachweis eingesetzt werden. In der ersten Phase der Arbeit wurden verschiedene Träger aus mesoporösem Siliziumdioxid (von Nano- und Mikropartikeln in Form von Plättchen und kurzen Fasern), unterschiedliche Funktionalisierungswege sowie Beladungssequenzen untersucht und bewertet. Da sich diese Materialien gut für LFAs eignen, wurde die Leistungsfähigkeit nicht nur mit herkömmlichen Assays in Suspension, sondern auch im Teststreifenformat untersucht. Die Kombination von Farbstoffen als Indikatoren und Smartphones zum Auslesen konnten einfache analytische Tests entwickelt werden, die in Zukunft von ungeschultem Personal direkt am Ort des Geschehens, z. B. in einer Flugzeugkabine, eingesetzt werden können und Ergebnisse in weniger als 5 Minuten erforderlichen Selektivität liefern. / Across this work, it was investigated the possibility of detecting a specific class of pesticides with a lateral flow test as a platform and a smartphone set-up for signal detection. Specifically, type-I pyrethroids are insecticides employed eventually to kill mosquitos that can be vectors for e.g., viral diseases. Permethrin and phenothrin, the most well-known pyrethroid compounds, are recently used for disinfection purposes on airplanes from and to tropical areas to avoid the spread of dangerous illnesses as malaria, zika or dengue. As there is still no control on the amount of insecticide sprayed onboard, a new effective and rapid method for pyrethroids analysis directly in the plane is needed. For this purpose, a portable test in lateral flow assay format was realized involving gated antibody indicator delivery systems for sensing. In the first stage of the work, different mesoporous silica supports (from nano and microparticles to platelets and short fibers), different functionalisation routes, and different loading sequences were assessed. Then, the materials’ performances were evaluated by studying their temporal response behaviour and detection sensitivity, including the tightness of pore closure (through the amount of blank release in the absence of an analyte) and the release kinetics. Finally, because such materials are well-suited for LFAs, performance assessment included a test-strip format besides conventional assays in suspension. The combination of dyes as indicators and smartphones for read-out, simple analytical tests for use by untrained personnel directly at a point-of-need such as an airplane cabin, can be devised, allowing for results in less than 5 min with the-required selectivity.

<p>This dissertation describes how the surface chemistries of 2D nanomaterials can be modified to alter overall material properties. Specifically, through a focus of the ligand-surface atom bonding in addition to the overall ligand structure we highlight the ability to direct morphological outcomes in lead free halide perovskites, maximize optoelectronic responses in substoichiometric tungsten oxide, and alter physicochemical properties titanium carbide MXenes.   </p>

The combination of X-ray imaging and diffraction techniques provides a unique tool for structural and mechanical analysis of engineering components. A variety of modes can be employed in terms of the spatial resolution (length-scale), time resolution (frequency), and the nature of the physical quantity being interrogated. This thesis describes my contributions towards the development of novel X-ray “rich” imaging experimental techniques and data interpretation. The experimental findings have been validated via comparison with other experimental methods and numerical modelling. The combination of fast acquisition rate and high penetration properties of X-ray beams allows the collection of high-resolution 3-D tomographic data sets at submicron resolution during in situ deformation experiments. Digital Volume Correlation analysis tools developed in this study help understand crack propagation mechanisms in quasi-brittle materials and elasto-plastic deformation in co-sprayed composites. For the cases of crystalline specimens where the knowledge of “live” or residual elastic strain distributions is required, diffraction techniques have been advanced. Diffraction Strain Tomography (DST) allows non-destructive reconstruction of the 2-D (in-plane) variation of the out-of-plane strain component. Another diffraction modality dubbed Laue Orientation Tomography (LOT), a grain mapping approach has been proposed and developed based on the translate-rotate tomographic acquisition strategy. It allows the reconstruction of grain shape and orientation within polycrystalline samples, and provides information about intragranular lattice strain and distortion. The implications of this method have been thoroughly investigated. State-of-the-art engineering characterisation techniques evolve towards scrutinising submicron scale structural features and strain variation using the complementarity of X-ray imaging and diffraction. The first successful feasibility study is reported of in operando stress analysis in an internal combustion engine. Finally, further advancement of ‘rich’ imaging techniques is illustrated via the first successful application of Time-of-Flight Neutron Diffraction Strain (TOF-NDST) tomography for non-destructive reconstruction of the complete strain tensor using an inverse eigenstrain formulation.

A study of three novel solar cells is presented, all of which incorporate a low-dimensional quantum confined component in a bid to enhance device performance. Firstly, intermediate band solar cells (IBSCs) based on InAs quantum dots (QDs) in a GaAs p-i-n structure are studied. The aim is to isolate the InAs QDs from the GaAs conduction band by surrounding them with wider band gap aluminium arsenide. An increase in open circuit voltage (V_OC) and decrease in short circuit current (J_sc) is observed, causing no overall change in power conversion efficiency. Dark current - voltage measurements show that the increase in V_OC is due to reduced recombination. Electroreflectance and external quantum efficiency measurements attribute the decrease in J_sc primarily to a reduction in InGaAs states between the InAs QD and GaAs which act as an extraction pathway for charges in the control device. A colloidal quantum dot (CQD) bulk heterojunction (BHJ) solar cell composed of a blend of PbS CQDs and ZnO nanoparticles is examined next. The aim of the BHJ is to increase charge separation by increasing the heterojunction interface. Different concentration ratios of each phase are tested and show no change in J_sc, due primarily to poor overall charge transport in the blend. V_OC increases for a 30 wt% ZnO blend, and this is attributed largely to a reduction in shunt resistance in the BHJ devices. Finally, graphene is compared to indium tin oxide (ITO) as an alternative transparent electrode in squaraine/ C₇₀ solar cells. Due to graphene’s high transparency, graphene devices have enhanced J_sc, however, its poor sheet resistance increases the series resistance through the device, leading to a poorer fill factor. V_OC is raised by using MoO₃ as a hole blocking layer. Absorption in the squaraine layer is found to be more conducive to current extraction than in the C₇₀ layer. This is due to better matching of exciton diffusion length and layer thickness in the squaraine and to the minority carrier blocking layer adjacent to the squaraine being more effective than the one adjacent to the C₇₀.

Conventional computing faces a huge technical challenge as traditional transistors will soon reach their size limitations. This will halt progress in reaching faster processing speeds and to overcome this problem, require an entirely new approach. Quantum computing (QC) is a natural solution offering a route to miniaturisation by, for example, storing information in electron or nuclear spin states, whilst harnessing the power of quantum physics to perform certain calculations exponentially faster than its classical counterpart. However, QCs face many difficulties, such as, protecting the quantum-bit (qubit) from the environment and its irreversible loss through the process of decoherence. Hybrid systems provide a route to harnessing the benefits of multiple degrees of freedom through the coherent transfer of quantum information between them. In this thesis I show coherent qubit transfer between electron and nuclear spin states in a ¹⁵N@C₆₀ molecular system (comprising a nitrogen atom encapsulated in a carbon cage) and a solid state system, using phosphorous donors in silicon (Si:P). The propagation uses a series of resonant mi- crowave and radiofrequency pulses and is shown with a two-way fidelity of around 90% for an arbitrary qubit state. The transfer allows quantum information to be held in the nuclear spin for up to 3 orders of magnitude longer than in the electron spin, producing a ¹⁵N@C₆₀ and Si:P ‘quantum memory’ of up to 130 ms and 1.75 s, respectively. I show electron and nuclear spin relaxation (T₁), in both systems, is dominated by a two-phonon process resonant with an excited state, with a constant electron/nuclear T₁ ratio. The thesis further investigates the decoherence and relaxation properties of metal atoms encapsulated in a carbon cage, termed metallofullerenes, discovering that exceptionally long electron spin decoherence times are possible, such that these can be considered a viable QC candidate.

The self-assembly of structured particles into monodisperse clusters is a challenge on the nano-, micro- and even macro-scale. While biological systems are able to self-assemble with comparative ease, many aspects of this self-assembly are not fully understood. In this thesis, we look at the strategies and rules that can be applied to encourage the formation of monodisperse clusters. Though much of the inspiration is biological in nature, the simulations use a simple minimal patchy particle model and are thus applicable to a wide range of systems. The topics that this thesis addresses include: Encapsulation: We show how clusters can be used to encapsulate objects and demonstrate that such `templates' can be used to control the assembly mechanisms and enhance the formation of more complex objects. Hierarchical self-assembly: We investigate the use of hierarchical mechanisms in enhancing the formation of clusters. We find that, while we are able to extend the ranges where we see successful assembly by using a hierarchical assembly pathway, it does not straightforwardly provide a route to enhance the complexity of structures that can be formed. Pore formation: We use our simple model to investigate a particular biological example, namely the self-assembly and formation of heptameric alpha-haemolysin pores, and show that pore insertion is key to rationalising experimental results on this system. Phase re-entrance: We look at the computation of equilibrium phase diagrams for self-assembling systems, particularly focusing on the possible presence of an unusual liquid-vapour phase re-entrance that has been suggested by dynamical simulations, using a variety of techniques.

This thesis is concerned with the influence of nanoscale boundaries and interfaces upon the electronic processes that occur within the inorganic semiconductors. Inorganic semiconductor nanowires and their blends with semiconducting polymers have been investigated using state-of-the-art ultrafast optical techniques to provide information on the sub-picosecond to nanosecond photoexcitation dynamics in these systems. Chapters 1 and 2 introduce the theory and background behind the work and present a literature review of previous work utilising nanowires in hybrid organic photovoltaic devices, revealing the performances to date. The experimental methods used during the thesis are detailed in Chapter 3. Chapter 4 describes the crucial roles of surface passivation on the ultrafast dynamics of exciton formation in gallium arsenide (GaAs) nanowires. By passivating the surface states of nanowires, exciton formation via the bimolecular conversion of electron-hole plasma can observed over few hundred picoseconds, in-contrast to the fast carrier trapping in 10 ps observed in the uncoated nanowires. Chapter 5 presents a novel method to passivate the surface-states of GaAs nanowires using semiconducting polymer. The carrier lifetime in the nanowires can be strongly enhanced when the ionization potential of the overcoated semiconducting polymer is smaller than the work function of the nanowires and the surface native oxide layers of nanowires are removed. Finally, Chapter 6 shows that the carrier cooling in the type-II wurtzite-zincblend InP nanowires is reduced by order-of magnitude during the spatial charge-transfer across the type-II heterojunction. The works decribed in this thesis reveals the crucial role of surface-states and bulk defects on the carrier dynamics of semiconductor nanowires. In-addition, a novel approach to passivate the surface defect states of nanowires using semiconducting polymers was developed.

Existing methods for pathogen/pollutant detection or wound infection monitoring employ high-cost instruments that could only be operated by trained personnel, and costly device-based detection requires a time-consuming field-to-lab process. This expensive process with multiple prerequisites prolongs the time that patients must wait for a diagnosis. Therefore, improved methods for point-of-care biosensing are necessary. In this study, we aimed to develop a direct, easy-to-use, portable, low cost, highly sensitive and selective sensor platform with the goal of pollutant detection and wound infection/cancer migration monitoring. This study has two main parts, including microfluidic, electrical, and optical sensing platforms. The first part, including chapters 2, 3, and 4, focuses on Bisphenol A (BPA) lateral flow assay (LFA) detection; the second part, including chapter 5 focuses on the electrical sensing platform fabrication for one of the markers of inflammation, matrix metalloproteinases-9 (MMP-9), monitoring/detection. In chapters 2, 3, and 4, we found that the few lateral flow assays (LFAs) established for detecting the endocrine-disrupting chemical BPA have employed citrate-stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, in chapter 2, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. In chapter 3, we describe the development of a new range-extended bisphenol A (BPA) detection method that uses a surface enhanced Raman scattering lateral flow assay (SERS-LFA) binary system. In chapter 4, we examine advanced bisphenol A (BPA) lateral flow assays (LFAs) that use multiple nanosystems. The assays include three nanosystems, namely, gold nanostars, gold nanocubes, and gold nanorods, which are rarely applied in LFAs, compared with general gold nanoparticles. The developed LFAs show different performances in the detection of BPA. In chapter 5, a stable electrical sensing platform is developed for MMP-9 detection.