Infrared Energy Conversion in Plasmonic Fields at Two-Dimensional Semiconductors

Conversion of infrared energy within plasmonic fields at two-dimensional, semiconductive transition metal dichalcogenides (TMD) through plasmonic hot electron transport and nonlinear frequency mixing has important implications in next-generation optoelectronics. Drude-Lorentz theory and approximate discrete dipole (DDA) solutions to Maxwell’s equations guided metal nanoantenna design towards strong infrared localized surface plasmon resonance (LSPR). Excitation and damping dynamics of LSPR in heterostructures of noble metal nanoantennas and molybdenum- or tungsten-disulfide (MoS2; WS2) monolayers were examined by parallel synthesis of (i) DDA electrodynamic simulations and (ii) near-field electron energy loss (EELS) and far-field optical transmission UV-vis spectroscopic measurements. Susceptibility to second-order nonlinear frequency conversion processes, X(2), for monolayer MoS2 and WS2 were measured to be 660±130 pm V-1 and 280±18 pm V-1, respectively, by Hyper Rayleigh Scattering. Femtosecond conversion of resonant irradiation to injection of plasmonic hot electrons into the TMD were measured in EELS at a maximum of 11±5% quantum efficiency for an optimized physicochemical Au-WS2 junction. Measured nonlinear second harmonic generation (SHG) from a ca. 1 μm MoS2 monolayer was enhanced 17-84% by local electric field augmentation from a single 150 nm Au nanoshell to a conversion efficiency of up to 0.023% W-1. Capacitive coupling between nanoshells arranged into dimers further augmented SHG activity from MoS2. New theoretical and experimental insights into energy conversion interactions between coupled plasmonic and excitonic materials spanning the linear and nonlinear optical regimes were established towards their implementation as an optoelectronic platform

Femtosecond laser microfabricated devices for biophotonic applications

Femtosecond Laser DirectWriting has emerged as a key enabling technology for realising miniaturised biophotonic applications offering clear advantages over competing soft-lithography, ion-exchange and sol-gel based fabrication techniques. Waveguide writing and selective etching with three-dimensional design flexibility allows the development of innovative and unprecedented optofluidic architectures using this technology. The work embodied in this thesis focuses on utilising the advantages offered by direct laser writing in fabricating integrated miniaturised devices tailored for biological analysis. The first application presented customised the selective etching phenomenon in fused silica by tailoring the femtosecond pulse properties during the writing process. A device with an embedded network of microchannels with a significant difference in aspect-ratio was fabricated, which was subsequently applied in achieving the high-throughput label-free sorting of mammalian cells based on cytoskeletal deformability. Analysis on the device output cell population revealed minimal effect of the device on cell viability. The second application incorporated an embedded microchannel in fused silica with a monolithically integrated near-infrared optical waveguide. This optofluidic device implemented the thermally sensitive emission spectrum of semiconductor nanocrystals in undertaking remote thermometry of the localised microchannel environment illuminated by the waveguide. Aspects relating to changing the wavelength of illumination from the waveguide were analysed. The effect of incorporating carbon nanotubes as efficient heaters within the microchannel was investigated. Spatio-thermal imaging of the microchannel illuminated by the waveguide revealed the thermal effects to extend over distances appreciably longer than the waveguide cross-section. On the material side of direct laser writing, ultra-high selective etching is demonstrated in the well-known laser crystal Nd:YAG. This work presents Nd:YAG as a material with the potential to develop next-generation optofluidic devices

Multimodal Spectroscopy and Imaging of Chabazite Zeolite

Zeolites are a type of crystalline aluminosilicate material that when produced synthetically find use in a variety of contexts, many of which are directly beneficial to society at large. One such application, which is of interest not only from the perspective of commercial profitability but perhaps more pertinently in today’s climate from an environmental point of view, is catalysis. Two important examples of commercialised catalytic reactions are selective catalytic reduction (SCR) and the methanol-to-olefins (MTO) reaction, which, respectively, involve the catalytic conversion of noxious NOx gases to nitrogen & water, and waste methanol to higher value petrochemicals. A central challenge in catalysis is the development of characterisation techniques capable of navigating the structurally and compositionally complex internal landscapes of zeolitic catalysts. While the bulk scale information gleaned through techniques like mass spectroscopy, XRD, and NMR provide an established benchmark against which zeolite behaviour is currently assessed, gaining spatially resolved insight into catalytic activity on a nanometric, single-catalyst length scale is highly desirable in current research efforts focused on optimising and improving existing catalytic systems. Laser-based characterisation, being non-destructive and capable of molecular excitation, is identified here as a viable but underexplored option for studying zeolites in a catalytic chemistry context. Time-resolved photoluminescence spectroscopy (TRPS) and confocal-lifetime microscopy are applied to zeolite systems, providing fresh insight into aspects of the zeolite’s synthesis process. TRPS is further combined with in situ setups to provide new information on zeolite behaviour during an active catalytic reaction as a function of time and temperature. Finally, combined IR spectroscopy and X-ray microscopy studies were conducted on Cu-containing forms of the high silica form (SSZ-13) of the zeolite chabazite (CHA)

Making microscopy count: quantitative light microscopy of dynamic processes in living plants

First published: April 2016This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Cell theory has officially reached 350 years of age as the first use of the word ‘cell’ in a biological context can be traced to a description of plant material by Robert Hooke in his historic publication “Micrographia: or some physiological definitions of minute bodies”. The 2015 Royal Microscopical Society Botanical Microscopy meeting was a celebration of the streams of investigation initiated by Hooke to understand at the sub-cellular scale how plant cell function and form arises. Much of the work presented, and Honorary Fellowships awarded, reflected the advanced application of bioimaging informatics to extract quantitative data from micrographs that reveal dynamic molecular processes driving cell growth and physiology. The field has progressed from collecting many pixels in multiple modes to associating these measurements with objects or features that are meaningful biologically. The additional complexity involves object identification that draws on a different type of expertise from computer science and statistics that is often impenetrable to biologists. There are many useful tools and approaches being developed, but we now need more inter-disciplinary exchange to use them effectively. In this review we show how this quiet revolution has provided tools available to any personal computer user. We also discuss the oft-neglected issue of quantifying algorithm robustness and the exciting possibilities offered through the integration of physiological information generated by biosensors with object detection and tracking

Supercontinuum radiation in fluorescence microscopy and biomedical imaging applications

Compact, high brightness supercontinuum sources have already made a big impact in the fields of fluorescence microscopy and other biomedical imaging techniques, such as optical coherence tomography and coherent anti-Stokes Raman scattering. In this review, we provide a brief overview on the generation and properties of supercontinuum radiation for imaging applications. We review specific uses of supercontinuum sources and their potential for imaging, but also their limitations and caveats. We conclude with a review of recent advances in UV supercontinuum generation, near-IR microscopy, exciting new potentials for the use of hollow-core PCFs, on-chip supercontinuum generation, and technologies to improve supercontinuum stability for certain applications.H2020 Marie Skłodowska-Curie Actions (MSCA) (722380); MedImmune; Infinitus (China) Ltd.; Engineering and Physical Sciences Research Council (EPSRC) (EP/H018301/1, EP/L015889/1); Wellcome Trust (089703/Z/09/Z, 3-3249/Z/16/Z); Medical Research Council (MRC) (MR/K015850/1, MR/K02292X/1)

Micro-Opto-Electro-Mechanical Device Based on Flexible ß-Ga2O3 Micro-Lamellas

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Dispositivos fotónicos con base sol-gel y de silicio

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, leída el 01/07/2013Depto. de ÓpticaFac. de Ciencias FísicasTRUEunpu

Design and Characterization of Lubricants Based on Functionalized Nanoparticles

The main objective of this PhD thesis is to design and characterize efficient nanolubricants based on three polyalphaolefins (PAOs) and nanoparticles (NPs) of metal oxides or ceramics coated with organic acids for wind turbine gearboxes and electric transmissions of electric vehicles. First, preliminary tests and an in-depth literature survey on the time stability and tribological behavior of nanodispersions containing chemically modified nanoadditives were performed. Then, the thermophysical and tribological properties of PAO nanolubricants containing coated NPs (ZnO-OA, TiO2-OA, or SiO2-SA) were evaluated; in addition, possible tribological mechanisms were analyzed by confocal Raman microscopy. All the coated NPs studied improve the tribological behavior of their base oil, being the best the SiO2-SA NPs

APPLICATION OF DIFFRACTIVE OPTICAL ELEMENT ON SPECTROSCOPY AND IMAGING

Zhenkun Guo: Application of Diffractive Optical Element on Spectroscopy and Imaging (Under the direction of Andrew Moran) Diffractive optical elements (DOE) are optical components that manipulate light by diffraction, interference, and other phase control methods. The application of DOE in multi-dimensional spectroscopy could significantly reduce the efforts required for conducting experiments and enhance the signal-to-noise ratio with high efficiency. In this dissertation, DOE-based two-dimensional resonance Raman spectroscopy was developed and implemented in two model systems, triiodide and myoglobin. This new technique uncovers new dimensions of information, which were not available with previous one-dimensional spectroscopy techniques. The DOE was also applied to the wide-field transient absorption microscopy. Conducting a large number of experiments simultaneously is possible in this configuration. Analysis of parallel measurements provides statistical information essential to comprehensively study heterogeneous samples. After absorbing an ultraviolet photon, triiodide undergoes photodissociation to produce diiodide and radical iodine on a time scale comparable to the period of triiodide’s nuclear motion, which could impulsively activate a vibrational coherence in the diiodide. In this dissertation, the ability of 2DRR to capture coherent reaction mechanisms is demonstrated by directly establishing a correlation, for the first time, between the nonequilibrium geometry of triiodide at photodissociation and the stretching frequency of diiodide. Ligand binding and dissociation processes are crucial to the functions of heme proteins. The recovery of the protein matrix involves fast energy dissipation from the heme group to solvent, facilitated by the propionic acid side chains as an effective “gateway”. In this dissertation, we found that the propionic chains possess significant structural heterogeneity, which could be induced by the thermal fluctuation in geometries. It is interesting to consider whether the variation in conformation could relate to the vibrational cooling rate distributions. Carrier diffusion is imaged in a perovskite film and crystal using a newly developed DOE-based wide-field transient absorption microscopy technique. The function of the instrument is illustrated with 41 parallel measurements conducted on methylammonium lead iodide perovskite films and single crystals in a single experiment. Obvious carrier diffusion is observed in the crystal. However, results indicate that the carrier dynamics in the film are dominated by many-body interactions instead. The grain boundaries in the film contribute to this difference in behavior.Doctor of Philosoph