<p>bold</p> / Dissertation

abstract: A major goal of synthetic biology is to recapitulate emergent properties of life. Despite a significant body of work, a longstanding question that remains to be answered is how such a complex system arose? In this dissertation, synthetic nucleic acid molecules with alternative sugar-phosphate backbones were investigated as potential ancestors of DNA and RNA. Threose nucleic acid (TNA) is capable of forming stable helical structures with complementary strands of itself and RNA. This provides a plausible mechanism for genetic information transfer between TNA and RNA. Therefore TNA has been proposed as a potential RNA progenitor. Using molecular evolution, functional sequences were isolated from a pool of random TNA molecules. This implicates a possible chemical framework capable of crosstalk between TNA and RNA. Further, this shows that heredity and evolution are not limited to the natural genetic system based on ribofuranosyl nucleic acids. Another alternative genetic system, glycerol nucleic acid (GNA) undergoes intrasystem pairing with superior thermalstability compared to that of DNA. Inspired by this property, I demonstrated a minimal nanostructure composed of both left- and right-handed mirro image GNA. This work suggested that GNA could be useful as promising orthogonal material in structural DNA nanotechnology. / Dissertation/Thesis / Ph.D. Chemistry 2011

abstract: ABSTRACT An Ensemble Monte Carlo (EMC) computer code has been developed to simulate, semi-classically, spin-dependent electron transport in quasi two-dimensional (2D) III-V semiconductors. The code accounts for both three-dimensional (3D) and quasi-2D transport, utilizing either 3D or 2D scattering mechanisms, as appropriate. Phonon, alloy, interface roughness, and impurity scattering mechanisms are included, accounting for the Pauli Exclusion Principle via a rejection algorithm. The 2D carrier states are calculated via a self-consistent 1D Schrödinger-3D-Poisson solution in which the charge distribution of the 2D carriers in the quantization direction is taken as the spatial distribution of the squared envelope functions within the Hartree approximation. The wavefunctions, subband energies, and 2D scattering rates are updated periodically by solving a series of 1D Schrödinger wave equations (SWE) over the real-space domain of the device at fixed time intervals. The electrostatic potential is updated by periodically solving the 3D Poisson equation. Spin-polarized transport is modeled via a spin density-matrix formalism that accounts for D'yakanov-Perel (DP) scattering. Also, the code allows for the easy inclusion of additional scattering mechanisms and structural modifications to devices. As an application of the simulator, the current voltage characteristics of an InGaAs/InAlAs HEMT are simulated, corresponding to nanoscale III-V HEMTs currently being fabricated by Intel Corporation. The comparative effects of various scattering parameters, material properties and structural attributes are investigated and compared with experiments where reasonable agreement is obtained. The spatial evolution of spin-polarized carriers in prototypical Spin Field Effect Transistor (SpinFET) devices is then simulated. Studies of the spin coherence times in quasi-2D structures is first investigated and compared to experimental results. It is found that the simulated spin coherence times for GaAs structures are in reasonable agreement with experiment. The SpinFET structure studied is a scaled-down version of the InGaAs/InAlAs HEMT discussed in this work, in which spin-polarized carriers are injected at the source, and the coherence length is studied as a function of gate voltage via the Rashba effect. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

abstract: Biogenic silica nanostructures, derived from diatoms, possess highly ordered porous hierarchical nanostructures and afford flexibility in design in large part due to the availability of a great variety of shapes, sizes, and symmetries. These advantages have been exploited for study of transport phenomena of ions and molecules towards the goal of developing ultrasensitive and selective filters and biosensors. Diatom frustules give researchers many inspiration and ideas for the design and production of novel nanostructured materials. In this doctoral research will focus on the following three aspects of biogenic silica: 1) Using diatom frustule as protein sensor. 2) Using diatom nanostructures as template to fabricate nano metal materials. 3) Using diatom nanostructures to fabricate hybrid platform. Nanoscale confinement biogenetic silica template-based electrical biosensor assay offers the user the ability to detect and quantify the biomolecules. Diatoms have been demonstrated as part of a sensor. The sensor works on the principle of electrochemical impedance spectroscopy. When specific protein biomarkers from a test sample bind to corresponding antibodies conjugated to the surface of the gold surface at the base of each nanowell, a perturbation of electrical double layer occurs resulting in a change in the impedance. Diatoms are also a new source of inspiration for the design and fabrication of nanostructured materials. Template-directed deposition within cylindrical nanopores of a porous membrane represents an attractive and reproducible approach for preparing metal nanopatterns or nanorods of a variety of aspect ratios. The nanopatterns fabricated from diatom have the potential of the metal-enhanced fluorescence to detect dye-conjugated molecules. Another approach presents a platform integrating biogenic silica nanostructures with micromachined silicon substrates in a micro/nano hybrid device. In this study, one can take advantages of the unique properties of a marine diatom that exhibits nanopores on the order of 40 nm in diameter and a hierarchical structure. This device can be used to several applications, such as nano particles separation and detection. This platform is also a good substrate to study cell growth that one can observe the reaction of cell growing on the nanostructure of frustule. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2014

Nous examinons une question que l'avènement des nanotechnologies rend de plus en plus pressante pour la philosophie des sciences. Elle prend les allures d'une critique de cette dernière en se fondant sur quelques théories philosophiques, représentatives et suffisamment originales sur la science, développées par Thomas Kuhn, Imre Lakatos, Ian Hacking et Serge Robert. Les différents discours sur les nanos et plus précisément le concept de nanotechnologie se sont révélés, à tout le moins, polysémiques et décrivent parfois prématurément une activité qui n'existe pas encore. Ainsi, nous avons requalifié le concept de nanotechnologie en « nanotechnoscience ». Puis nous avons confronté les philosophies des sciences que nous avons retenues aux fins de les mettre à l'épreuve de ce qui apparaît comme un impensé de leurs philosophies, notamment la dimension technologique de la science souvent connue et reconnue, mais « sous-traitée » et reléguée au mieux au second plan. Nos recherches ont donc porté sur chacune des philosophies que nous avons annoncées, sur les nanotechnosciences elles-mêmes, la philosophie de la technologie, mais aussi sur celle naissante des technosciences et des nanotechnosciences sans oublier notre ouverture à des fins heuristiques sur la philosophie du langage d'Austin et la praxéologie de Denis Vernant. Dans cette étude, nous avons traité d'étymologie, d'histoire du préfixe nano et de définition. Puis, nous avons examiné attentivement les différentes philosophies des sciences par lesquelles il nous a paru pertinent d'examiner les nanotechnosciences émergentes afin de voir ce qui dans ces doctrines permettrait d'envisager une réflexion philosophique sur les nanos. Sachant que ces pensées privilégient la représentation sur l'intervention, nous nous sommes posés la question de la place de la technologie dans ces systèmes philosophiques avec l'idée que la technologie est une condition nécessaire quoique non suffisante de toute philosophie à prétention technoscientifique ou nanotechnoscientifique. C'est dans cette optique que nous avons sollicité la théorie des paradigmes, puis celle du falsificationnisme sophistiqué revu et corrigé par le correctionnisme de Robert avant de tenter l'interventionnisme de Hacking. Nous avons pu constater l'omniprésence de la technologie tout comme l'hétérogénéité de la place qui lui est accordée dans ces théories philosophiques. Ainsi de Kuhn à Hacking, la reconnaissance du rôle et de la place de la technologie va crescendo, au point de nous inviter à penser les nanotechnosciences en termes d'« actes de discours ». L'enchevêtrement ou l'entrelacement entre science et technologie nous a inspiré deux analogies : la première avec l'idée de « contexte de performance oral » de Mamoussé Diagne analogue elle-même à la seconde, la performativité introduite et initiée par les réflexions d'Austin sur le discours ordinaire. Notre investigation prend les allures d'une mise à l'épreuve de toutes ces philosophies à l'aune de la place qu'occupe la technologie dans leurs systèmes respectifs. Nous avons eu recours à l'analyse comparative des discours philosophiques sur la science ainsi que ce que nous avons appris sur les pratiques scientifiques, le tout complété par une approche lexicométrique basée sur le corpus des principaux ouvrages de Kuhn, Lakatos, Robert et Hacking. Notre démarche nous a amené à mettre en cause l'étymologie du préfixe nano trop hâtivement attribuée au grec alors qu'il serait plus à propos de la considérer comme latine, puis nous avons tenté d'établir l'idée que les « nanotechnologies » n'existent pas et que ce que l'on appelle bien souvent ainsi relève d'un abus de langage et d'une sorte d'anachronisme inversée. De cette critique nous avons tenté de tirer des leçons qui ont inspiré la requalification conceptuelle de l'activité qu'est censé désigner ce morphème en « nanotechnoscience » que nous avons redéfini en tenant compte de plusieurs facteurs déterminants. / This thesis focuses on the consideration of a question that the advent of what is called nanotechnology makes it increasingly urgent to philosophy in general and the philosophy of science in particular because of the inexistence of the “nanotechnology” stricto sensu, the lack of good definition and the default of something like a “nanophilosophy”. We critique the latter based on some philosophical, representative and sufficiently original theories of science, developed by Thomas Kuhn, Imre Lakatos, Ian Hacking and Serge Robert. Different discourses on nanos and more specifically the concept of nanotechnology proved, at least, polysemous and sometimes describe an activity which in the strict sense does not exist prematurely. Thus, we have reclassified the concept of nanotechnology "nanotechnoscience" and proposed a more rigorous definition emphasizing the hybrid nature of this activity, both theoretical and practical, scientific and technological. Then we compared the philosophies of science that we have selected to make them confront what appears to be an unthought of their philosophies, including the technological dimension of science often known and recognized, but "outsourced" and relegated to better secondary. Our research has therefore focused on each of the philosophies that we announced on the nanotechnosciences themselves, philosophy of technology, but also on emerging technosciences and nanotechnoscience not forgetting our opening for heuristic purposes on the philosophy of language of Austin and praxeology of Denis Vernant. Then, we carefully examined the different philosophies of science which seemed appropriate to consider the emerging nanotechnosciences so as to see what in these doctrines would help envisaging a philosophical reflection on the Nano. Knowing that these thoughts favor representing rather than intervening, we questioned the role of technology in these philosophical systems with the idea that technology is a necessary though not sufficient condition for any claim of technoscientific or nanotechnoscientific philosophy. It is in this context that we solicited the paradigms theory, then the sophisticated falsificationism reviewed and corrected by Robert's correctionism before attempting interventionism Hacking's interventionism. During this exercise we have seen the pervasiveness of technology as well as the heterogeneity of the place it is granted in these philosophical theories. The entanglement or intertwining between science and technology inspired us two analogies: the first with the idea of "context of oral performance" by Mamoussé Diagne, analogous itself to the second, performativity introduced and initiated by Austin's reflections on ordinary language. Our investigation takes on the appearance of a testing of all these philosophies in terms of the place of technology in their respective systems. To achieve this, we resorted to the comparative analysis of philosophical discourse on science and what we have learned about scientific practices, complemented by a lexicometric approach based on the corpus of the principal works published from Kuhn, Lakatos, Robert and Hacking. From our critique we have tried to draw lessons that inspired the conceptual requalification of the activity that this morpheme is intended to mean into "nanotechnoscience" which we have redefined. This established at the end of this analysis, we could say that neither the philosophy of Kuhn or Lakatos, nor that of Robert leave enough space for technology to position itself as philosophies of technosciences. The one which seems the most appropriate is the interventionism defended by Hacking, but which Gilbert Hottois criticized for not having taken the step that would have led to a philosophy of authentic technosciences. It was then that tracks to Bacon and Peirce are suggested respectively by Hacking and Schmidt and Nordmann.

abstract: III-Nitride nanostructures have been an active area of research recently due to their ability to tune their optoelectronic properties. Thus far work has been done on InGaN quantum dots, nanowires, nanopillars, amongst other structures, but this research reports the creation of a new type of InGaN nanostructure, nanorings. Hexagonal InGaN nanorings were formed using Metal Organic Chemical Vapor Deposition through droplet epitaxy. The nanorings were thoroughly analyzed using x-ray diffraction, photoluminescence, electron microscopy, electron diffraction, and atomic force microscopy. Nanorings with high indium incorporation were achieved with indium content up to 50% that was then controlled using the growth time, temperature, In/Ga ratio and III/N ratio. The analysis showed that the nanoring shape is able to incorporate more indium than other nanostructures, due to the relaxing mechanism involved in the formation of the nanoring. The ideal conditions were determined to be growth of 30 second droplets with a growth time of 1 minute 30 seconds at 770 C to achieve the most well developed rings with the highest indium concentration. / Dissertation/Thesis / M.S. Materials Science and Engineering 2012

The objective of this thesis was to investigate whether the addition of carbon nanofibers had an effect on the splitting tensile strength of Hydro-Stone gypsum concrete. The carbon nanofibers used were single-walled carbon nanotubes (SWNT), buckminsterfullerene (C60), and graphene oxide (GO). Evidence of the nanofibers interacting with gypsum crystals in a connective manner was identified in both 1 mm thick concrete discs and concrete columns possessing a height of 2 in and a diameter of 1 in. Before imaging, the columns were subjected to a splitting tensile strength test. The results illustrate that while there is a general decrease in strength with an increase in nanofibers for the nanotubes and graphene oxide, the addition of C60 did not noticeably effect the strength. This trend is consistent with trends determined by previous studies.

This dissertation describes the development of a label-free, electrochemical immunosensing platform integrated into a low-cost microfluidic system for the sensitive, selective and accurate detection of cortisol, a steroid hormone co-related with many physiological disorders. Abnormal levels of cortisol is indicative of conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiencies and more recently post-traumatic stress disorder (PTSD). Electrochemical detection of immuno-complex formation is utilized for the sensitive detection of Cortisol using Anti-Cortisol antibodies immobilized on sensing electrodes. Electrochemical detection techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been utilized for the characterization and sensing of the label-free detection of Cortisol. The utilization of nanomaterial’s as the immobilizing matrix for Anti-cortisol antibodies that leads to improved sensor response has been explored. A hybrid nano-composite of Polyanaline-Ag/AgO film has been fabricated onto Au substrate using electrophoretic deposition for the preparation of electrochemical immunosening of cortisol. Using a conventional 3-electrode electrochemical cell, a linear sensing range of 1pM to 1µM at a sensitivity of 66µA/M and detection limit of 0.64pg/mL has been demonstrated for detection of cortisol. Alternately, a self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) has been fabricated for the modification of sensing electrode to immobilize with Anti-Cortisol antibodies. To increase the sensitivity at lower detection limit and to develop a point-of-care sensing platform, the DTSP-SAM has been fabricated on micromachined interdigitated microelectrodes (µIDE). Detection of cortisol is demonstrated at a sensitivity of 20.7µA/M and detection limit of 10pg/mL for a linear sensing range of 10pM to 200nM using the µIDE’s. A simple, low-cost microfluidic system is designed using low-temperature co-fired ceramics (LTCC) technology for the integration of the electrochemical cortisol immunosensor and automation of the immunoassay. For the first time, the non-specific adsorption of analyte on LTCC has been characterized for microfluidic applications. The design, fabrication technique and fluidic characterization of the immunoassay are presented. The DTSP-SAM based electrochemical immunosensor on µIDE is integrated into the LTCC microfluidic system and cortisol detection is achieved in the microfluidic system in a fully automated assay. The fully automated microfluidic immunosensor hold great promise for accurate, sensitive detection of cortisol in point-of-care applications.

A novel biocompatible and biodegradable polymer, termed poly(Glycerol malate co-dodecanedioate) (PGMD), was prepared by thermal condensation method and used for fabrication of nanoparticles (NPs). PGMD NPs were prepared using the single oil emulsion technique and loaded with an imaging/hyperthermia agent (IR820) and a chemotherapeutic agent (doxorubicin, DOX). The size of the void PGMD NPs, IR820-PGMD NPs and DOX-IR820-PGMD NPs were approximately 90 nm, 110 nm, and 125 nm respectively. An acidic environment (pH=5.0) induced higher DOX and IR820 release compared to pH=7.4. DOX release was also enhanced by exposure to laser, which increased the temperature to 42°C. Cytotoxicity of DOX-IR820-PGMD NPs was comparable in MES-SA but was higher in Dx5 cells compared to free DOX plus IR820 (pIn vivomouse studies showed that NP formulation significantly improved the plasma half-life of IR820 after tail vein injection. Significant lower IR820 content was observed in kidney in DOX-IR820-PGMD NP treatment as compared to free IR820 treatment in our biodistribution studies (p

In this research the integration of nanostructures and micro-scale devices was investigated using silica nanowires to develop a simple yet robust nanomanufacturing technique for improving the detection parameters of chemical and biological sensors. This has been achieved with the use of a dielectric barrier layer, to restrict nanowire growth to site-specific locations which has removed the need for post growth processing, by making it possible to place nanostructures on pre-pattern substrates. Nanowires were synthesized using the Vapor-Liquid-Solid growth method. Process parameters (temperature and time) and manufacturing aspects (structural integrity and biocompatibility) were investigated. Silica nanowires were observed experimentally to determine how their physical and chemical properties could be tuned for integration into existing sensing structures. Growth kinetic experiments performed using gold and palladium catalysts at 1050 ˚C for 60 minutes in an open-tube furnace yielded dense and consistent silica nanowire growth. This consistent growth led to the development of growth model fitting, through use of the Maximum Likelihood Estimation (MLE) and Bayesian hierarchical modeling. Transmission electron microscopy studies revealed the nanowires to be amorphous and X-ray diffraction confirmed the composition to be SiO2 . Silica nanowires were monitored in epithelial breast cancer media using Impedance spectroscopy, to test biocompatibility, due to potential in vivo use as a diagnostic aid. It was found that palladium catalyzed silica nanowires were toxic to breast cancer cells, however, nanowires were inert at 1µg/mL concentrations. Additionally a method for direct nanowire integration was developed that allowed for silica nanowires to be grown directly into interdigitated sensing structures. This technique eliminates the need for physical nanowire transfer thus preserving nanowire structure and performance integrity and further reduces fabrication cost. Successful nanowire integration was physically verified using Scanning electron microscopy and confirmed electrically using Electrochemical Impedance Spectroscopy of immobilized Prostate Specific Antigens (PSA). The experiments performed above serve as a guideline to addressing the metallurgic challenges in nanoscale integration of materials with varying composition and to understanding the effects of nanomaterials on biological structures that come in contact with the human body.