Au nanorods-semiconductor nanowire hybrid nanostructures : nanofabrication techniques and optoelectronic properties

The objective of this thesis is the exploration and characterization of novel Au nanorod-semiconductor nanowire hybrid nanostructures. I provide a comprehensive bottom-up approach in which, starting from the synthesis and theoretical investigation of the optical properties of Au nanorods, I design, nanofabricate and characterize Au nanorods-semiconductor nanowire hybrid nanodevices with novel optoelectronic capabilities compared to the non-hybrid counterpart. In this regards, I first discuss the seed-mediated protocols to synthesize Au nanorods with different sizes and the influence of nanorod geometries and non-homogeneous surrounding medium on the optical properties investigated by theoretical simulation. Novel methodologies for assembling Au nanorods on (i) a Si/SiO2 substrate with highly-ordered architecture and (ii) on semiconductor nanowires with spatial precision are developed and optimized. By exploiting these approaches, I demonstrate that Raman active modes of an individual ZnO nanowire can be detected in non-resonant conditions by exploring the longitudinal plasmonic resonance mediation of chemical-synthesized Au nanorods deposited on the nanowire surface otherwise not observable on bare ZnO nanowire. Finally, nanofabrication and detailed electrical characterization of ZnO nanowire field-effect transistor (FET) and optoelectronic properties of Au nanorods - ZnO nanowire FET tunable near-infrared photodetector are investigated. In particular we demonstrated orders of magnitude enhancement in the photocurrent intensity in the explored range of wavelengths and 40 times faster time response compared to the bare ZnO FET detector. The improved performance, attributed to the plasmonicmediated hot-electron generation and injection mechanism underlying the photoresponse is investigated both experimentally and theoretically. The miniaturized, tunable and integrated capabilities offered by metal nanorodssemicondictor nanowire device architectures presented in this thesis work could have an important impact in many application fields such as opto-electronic sensors, photodetectors and photovoltaic devices and open new avenues for designing of novel nanoscale optoelectronic devices.

New phosphorescence based probes and techniques for the analysis of cellular oxygen and respiration

Real time monitoring of oxygenation and respiration is on the cutting edge of bioanalysis, including studies of cell metabolism, bioenergetics, mitochondrial function and drug toxicity. This thesis presents the development and evaluation of new luminescent probes and techniques for intracellular O2 sensing and imaging. A new oxygen consumption rate (OCR) platform based on the commercial microfluidic perfusion channel μ-slides compatible with extra- and intracellular O2 sensitive probes, different cell lines and measurement conditions was developed. The design of semi-closed channels allowed cell treatments, multiplexing with other assays and two-fold higher sensitivity to compare with microtiter plate. We compared three common OCR platforms: hermetically sealed quartz cuvettes for absolute OCRs, partially sealed with mineral oil 96-WPs for relative OCRs, and open 96-WPs for local cell oxygenation. Both 96-WP platforms were calibrated against absolute OCR platform with MEF cell line, phosphorescent O2 probe MitoXpress-Intra and time-resolved fluorescence reader. Found correlations allow tracing of cell respiration over time in a high throughput format with the possibility of cell stimulation and of changing measurement conditions. A new multimodal intracellular O2 probe, based on the phosphorescent reporter dye PtTFPP, fluorescent FRET donor and two-photon antennae PFO and cationic nanoparticles RL-100 was described. This probe, called MM2, possesses high brightness, photo- and chemical stability, low toxicity, efficient cell staining and high-resolution intracellular O2 imaging with 2D and 3D cell cultures in intensity, ratiometric and lifetime-based modalities with luminescence readers and FLIM microscopes. Extended range of O2 sensitive probes was designed and studied in order to optimize their spectral characteristics and intracellular targeting, using different NPs materials, delivery vectors, ratiometric pairs and IR dyes. The presented improvements provide useful tool for high sensitive monitoring and imaging of intracellular O2 in different measurement formats with wide range of physiological applications.

Perceptions, expectations, and informal supports influence exercise activity in frail older adults

This study aims to explore frail older adults’ perceptions of what influences their exercise behaviors. A qualitative descriptive design was used. Semi-structured, open-ended interviews were conducted with 29 frail older adults. Thematic content analysis established the findings. Frail older adults perceive exercise as a by-product of other purposeful activities such as manual work or social activities. Progression into frailty appears to be associated with a decline in non-family support, changing traditional roles within family support networks, and lower baseline activity levels. Frail older adults perceive exercise as incidental to more purposeful activities rather than an endpoint in itself. Therefore, exercise programs concentrating on functional outcomes may be more relevant for this population. Strategies that educate and promote social support networks may also benefit frail older adults.

Personal learning artefacts: persistence, ownership and privacy

Traditional classrooms have been often regarded as closed spaces within which experimentation, discussion and exploration of ideas occur. Professors have been used to being able to express ideas frankly, and occasionally rashly while discussions are ephemeral and conventional student work is submitted, graded and often shredded. However, digital tools have transformed the nature of privacy. As we move towards the creation of life-long archives of our personal learning, we collect material created in various 'classrooms'. Some of these are public, and open, but others were created within 'circles of trust' with expectations of privacy and anonymity by learners. Taking the Creative Commons license as a starting point, this paper looks at what rights and expectations of privacy exist in learning environments? What methods might we use to define a 'privacy license' for learning? How should the privacy rights of learners be balanced with the need to encourage open learning and with the creation of eportfolios as evidence of learning? How might we define different learning spaces and the privacy rights associated with them? Which class activities are 'private' and closed to the class, which are open and what lies between? A limited set of set of metrics or zones is proposed, along the axes of private-public, anonymous-attributable and non-commercial-commercial to define learning spaces and the digital footprints created within them. The application of these not only to the artefacts which reflect learning, but to the learning spaces, and indeed to digital media more broadly are explored. The possibility that these might inform not only teaching practice but also grading rubrics in disciplines where public engagement is required will also be explored, along with the need for consideration by educational institutions of the data rights of students.

Techniques for engineering quantum states

In this thesis I theoretically study quantum states of ultracold atoms. The majority of the Chapters focus on engineering specific quantum states of single atoms with high fidelity in experimentally realistic systems. In the sixth Chapter, I investigate the stability and dynamics of new multidimensional solitonic states that can be created in inhomogeneous atomic Bose-Einstein condensates. In Chapter three I present two papers in which I demonstrate how the coherent tunnelling by adiabatic passage (CTAP) process can be implemented in an experimentally realistic atom chip system, to coherently transfer the centre-of-mass of a single atom between two spatially distinct magnetic waveguides. In these works I also utilise GPU (Graphics Processing Unit) computing which offers a significant performance increase in the numerical simulation of the Schrödinger equation. In Chapter four I investigate the CTAP process for a linear arrangement of radio frequency traps where the centre-of-mass of both, single atoms and clouds of interacting atoms, can be coherently controlled. In Chapter five I present a theoretical study of adiabatic radio frequency potentials where I use Floquet theory to more accurately model situations where frequencies are close and/or field amplitudes are large. I also show how one can create highly versatile 2D adiabatic radio frequency potentials using multiple radio frequency fields with arbitrary field orientation and demonstrate their utility by simulating the creation of ring vortex solitons. In the sixth Chapter I discuss the stability and dynamics of a family of multidimensional solitonic states created in harmonically confined Bose-Einstein condensates. I demonstrate that these solitonic states have interesting dynamical instabilities, where a continuous collapse and revival of the initial state occurs. Through Bogoliubov analysis, I determine the modes responsible for the observed instabilities of each solitonic state and also extract information related to the time at which instability can be observed.

Inquiring into perspective transformation in university education

My Portfolio of Exploration tackles the difficult question as to whether adult mental development can be accelerated and if so how. Rooted in constructive-developmental ideas, adult mental development is explained as an evolutionary unfolding of human capability. Going beyond this I look at the possibility of advancing development as transformational growth in adulthood in the belief that a broader perspective leads to increased effectiveness in professional life. Initially I explored my own meaning making, to make sense of my experiences, knowledge, relationships and my own motivations. This exploration has provided me with a ‘developmental bridge’ between my current way of knowing and a new more enlightened way. I have come to view my way of making meaning in the world as an evolving and progressive sequence of emotional and cognitive development. Through the formation of new stretching experiences, increased self - awareness and reflection my previous perspective has been overtaken by a more complex form of being aware of myself, others and the world. I refer to this process of growth as transformation. As part of my own transformational work I have conducted an inquiry into transformational growth and learning in the early academic life of university undergraduates. The result shows how accelerated adult mental development can be achieved in an academic environment ably preparing students for the workplace. This new model of education is part of a truly unique and exciting model signalling ground-breaking change for the undergraduate experience. The overhaul of a traditional BA degree in Economics into a world-class transformational programme is discussed through-out my Portfolio. Central to my broadening awareness is the challenge and nurturing required to awaken the student’s ‘internal authority’ . This involves stimulating students to take ownership for their own thinking, steering them away from the passivity and complacency of thinking through the minds of others. In doing so, the ultimate aim of renewing the BA is to narrow the developmental ‘mismatch’ which exists for m any college students between them and the world of work, by encouraging and inviting them to take on the challenge of thinking independently. Mindfulness, awareness, and personal authority are treated with reverence throughout the exploration as I consider them core parts of the students engaging with development. Engagement is construed as an active and open-minded process of awareness involving planning and reviewing one’s own goals and performance, engaging in constructive feedback, reflection and new action. I conclude with a view that the journey of adult mental development is relentless and that undergraduate education represents a crucial beginning. The value and relevance of transformational education rooted in developmental principles provides a significant opportunity in advancing development and perspectives at the start of adult life.

Career choice in medicine

Background: Career Choice in Medicine is an important and problematic topic. Medical education has been framed as professional identity development, yet career choice has not been viewed as a matter of identity. My primary aim was to offer new insights by exploring career choice using Figured Worlds theory, a socio-cultural theory of identity. Graduate retention is a challenge for many countries, including Ireland. My secondary aim was to address a gap in the data on postgraduate trainees in Ireland and to use the Irish case to illustrate points transferable to other contexts. Methodology & Methods: This was a predominantly qualitative Mixed Methods programme of research. My qualitative studies were oriented towards social constructionism. I collated existing data from the Royal College of Physicians of Ireland (RCPI) and HSE-MET to describe trainees and their career paths. I surveyed Basic Specialist Training trainees (n=333) about their career plans. I surveyed new trainees (n=527) about their expectations of training and all RCPI trainees about their experiences of training (n=1246). I conducted semi-structured interviews with 18 medical students and doctors. A subgroup (n=6) provided longitudinal data. Figured Worlds theory and Gee’s discourse tools were used for analysis. Results: I have used the case of medical training and career choice in Ireland to explain how social, political and cultural context, and day to day experiences in the cultural world of medicine, shaped doctors’ career choices. My qualitative findings described a unifying model of career choice, consisting of priming, exposure, positioning and open-endedness, which can guide the design of interventions to shape and support career choice. Conclusion: My original contribution has been to demonstrate the fruitfulness of framing career choice in terms of identity development. This represents a turn in the conversation about career choice, which brings new starting points and moves the dialogue forward.