Rozprawy doktorskie na temat „Experimental Nanoscience and Nanotechnology”

Electrospinning is a process by which polymer fibers can be produced using an electrostatically driven fluid jet. Electrospun fibers can be produced at the micro- or nano-scale and are, therefore, very promising for air filtration applications. However, because electrospun fibers are electrically charged, it is difficult to control the morphology of filtration media. Fiber size, alignment and uniformity are very important factors that affect filter performance. The focus of this project is to understand the relationship between filter morphology and performance and to develop new methods to create filtration media with optimum morphology. This study is divided into three focus areas: unimodal and bimodal microscale fibrous media with aligned, orthogonal and random fiber orientations; unimodal and bimodal nanoscale fibers in random orientations; bimodal micrometer and nanometer fiber media with orthogonally aligned orientations. The results indicate that the most efficient filters, which are those with the highest ratio of particle collection efficiency divided by pressure drop, can be obtained through fabricating filters in orthogonal layers of aligned fibers with two different fiber diameters. Moreover, our results show that increasing the number of layers increases the performance of orthogonally layered fibers. Also, controlling fiber spacing in orthogonally layered micrometer fiber media can be an alternative way to study the filtration performance. Finally, such coatings presented throughout this research study can be designed and placed up-stream, down-stream, and/or in between conventional filters.

Using experimental techniques along with computational fluid dynamics and electrodynamic simulations the performance of the first of three focusing elements in an electrospray macromolecular patterning system was assessed. The performance of this element, the ion funnel, was analyzed by varying the parameters and electric field applied to the system including electrospray emitter to atmosphere-vacuum interface capillary distance, temperature of the desolvating heater, injection rate of solution and the voltage applied to the jet disruption element. Results indicated that processes involved in injecting larger droplets into the chamber resulted in a less effective transmission of the ions through the funnel. Droplet diameter was increased by increasing flow rate and was decreased by increasing the desolvation heater. Varying the voltage applied to the jet disrupting element indicated a peak transmission voltage, when using a 20 mil interface capillary,of 175 V and when using the 30 mil capillary of 180 V. Numerical simulations were in agreement with these values although the widths of these transmission curves were much narrower than the experimental curves.

Transferring nanotechnology into marketable products and services is still considered a major challenge. In Europe, this issue has been identified as a weakness, not only for nanotechnology, but also for the other five Key Enabling Technologies (KETs), strategic for the economic growth of the region. In this regard, the current European Funding Programme Horizon 2020 is making great efforts with their action lines in order to prioritize the industrial implementation of KETs, and in this manner, address major economic and societal needs. This initiative is also fostering the cross-fertilization of KETs, since it has been determined that the sum of individual technologies increases the potential for innovation, optimizes technological development, and allows the creation of new markets. This thesis has been developed on the basis of this scenario. The aim is to analyse innovation and technology transfer challenges for the successful commercialization of nanotechnologies by emphasizing the process of cross-fertilization of KETs. The research is focused on healthcare due to the great impact that nano-scale is having on this field. For this reason, the present work has considered two approaches: from a technological perspective and from a management perspective. The analysis is comprised of a state-of-the-art and theoretical framework review, followed by a multiple case-study approach where several nano-enabled sensor-based devices are analysed at diverse levels of technological maturity. In addition, an empirical study of European nano-related innovation projects was undertaken in order to determine which projects’ characteristics are influencing the creation of technological diversity; a critical element for the long-term success of an emergent technology. Finally, project leaders were interviewed in order to gain insights about the managerial strategies that are boosting the process of cross-fertilization of KETs. Findings have shown that a multi-disciplinary, collaborative and integrated community of innovators is necessary for the effective transference and commercialization of multi-KET nanotechnologies. Additionally, the degree of multi-disciplinary projects was identified as significantly contributing to the creation of technological diversity. Furthermore, higher levels of cross-fertilization were found in market and customer-oriented projects, with actors strongly motivated to search for ideas from broad informal networks, and where technological knowledge is moderately heterogeneous. Lastly, it has been found that the cross-fertilization of KETs is boosted by actors with a high involvement of nanotechnologies in their industries. With these outcomes, this thesis has sought to contribute to the analysis of the successful transference and commercialization of multi-KET nanotechnologies in the field of healthcare by understanding the processes and ecosystems of innovation. The outcomes of this thesis have sought to contribute to the analysis of the successful transference and commercialization of multi-KET in the field of nanotechnologies applied to healthcare by understanding the processes and ecosystems of innovation. Accordingly, it is aimed to contribute to the reduction of the gap between research and the marketplace and to expand the knowledge of current interest regarding innovation ecosystems of emergent technologies, regional systems of innovation and strategic innovation management.
La transferència de productes i serveis basats en la nanotecnologia representa un gran repte. A Europa, aquest fet ha estat identificat com a punt dèbil, no només per a les nanotecnologies si no també per a les altres cinc tecnologies facilitadores transversales (KETs per les seves sigles en anglès), considerades estratègiques pel creixement econòmic de la regió. En aquest sentit, l’actual programa marc Europeu Horitzó 2020 està redirigint les seves línies d’acció per a prioritzar la implementació de les KETs i, d’aquesta manera, poder fer front a les necessitats econòmiques i socials més imperatives d’Europa. Aquesta iniciativa també pretén fomentar la fertilització creuada de les KETs, ja que s’ha establert que la suma de tecnologies individuals incrementa el potencial d’innovació, optimitza el desenvolupament de tecnologies i permet la creació de nous mercats. Sobre aquesta base es desenvolupa aquest treball d’investigació, el qual té la finalitat d’analitzar els reptes relacionats amb la innovació i la transferència tecnològica per a assolir amb èxit la comercialització de les nanotecnologies, posant de relleu el procés de fertilització creuada de les KETs en el camp de la salut. Amb aquesta finalitat, s’han considerat dues aproximacions: d’una banda una perspectiva tecnològica i, de l’altra, una perspectiva de gestió de la innovació. Els resultats obtinguts fan aportacions per l’anàlisi i identificació dels reptes que cal afrontar per a una favorable transferència i comercialització de les nanotecnologies multi-KET en el camp de la salut mitjançant la comprensió dels processos i ecosistemes d’innovació i, d’aquesta manera, contribuir a la reducció de la separació entre el laboratori i el mercat. Finalment també es pretén ampliar el coneixement sobre temàtiques d’interès actual respecte els ecosistemes d’innovació de les tecnologies emergents, els sistemes regionals d’innovació i la gestió estratègica de la innovació tecnològica.

Le nanotecnologie sono ormai parte dell’esperienza quotidiana e rappresentano un pilastro fondamentale dello sviluppo tecnologico, economico e sociale futuro. In particolare, l’Unione Europea le considera fra le tecnologie chiave per lo sviluppo tecnologico e ha messo in evidenza l’importanza di introdurne i principi base già nelle scuole superiori[1],. L’introduzione delle nanoscienze nei curricula delle scuole superiori permette di collegare le diverse materie in un’ottica interdisciplinare e si presta ad attività “hands-on” di provata efficacia[2]. Le nanoscienze mirano a progettare e realizzare materiali con nuove proprietà, i cosiddetti materiali funzionali, controllandone struttura, composizione chimica e morfologia alla micro- e nanoscala. Le loro caratteristiche microscopiche si riflettono infatti sulle loro proprietà macroscopiche in modo spesso eclatante. Diversi esempi di materiali funzionali sono facilmente reperibili sul mercato e le loro proprietà possono efficacemente essere illustrate nei laboratori scolastici. Solitamente queste dimostrazioni d’aula sono pensate per accendere la curiosità degli studenti, utilizzando il cosiddetto “wow-effect”. Il progetto Nanolab, di Unimore[3], mira ad andare oltre questo approccio, proponendo protocolli sperimentali quantitativi, riproducibili e facilmente realizzabili per introdurre alcune idee-chiave delle nanoscienze. In questo lavoro di tesi, che si inquadra nel progetto Nanolab, sono stati progettati alcuni nuovi protocolli e teaching-learning sequence (TLS), sviluppando un approccio didattico originale all’attività sperimentale, che trova fondamento in letteratura nel modello ISLE (Investigative Science Learning Environment)[4] e nell’ Instructional Model “5E”[5]. La tribologia, cioè lo studio dei fenomeni di attrito, è un settore delle scienze dei materiali di enorme rilevanza tecnologica. La comprensione delle origini microscopiche di questi fenomeni è a tutt’oggi oggetto di ricerca. Sebbene tradizionalmente i fenomeni di attrito siano piuttosto trascurati dai curricula scolastici, essi rappresentano invece l’occasione per introdurre concetti interdisciplinari estremamente importanti, quali le caratteristiche delle interazioni molecolari e il loro ruolo nel determinare le proprietà di superfici in contatto[6,7]. Un contributo in questa direzione è fornito dalla prima TLS sviluppata in questa tesi. Essa si basa sullo studio del Gecko Tape ®, un adesivo microstrutturato, bio-ispirato alle zampe del Gecko, e collega fisica e chimica, introducendo l’idea-chiave “struttura è funzione”. Il percorso proposto mima il mestiere dello scienziato nelle sue fasi di ricerca e di condivisione dei risultati con modalità simili a quelle di un congresso scientifico. La TLS è stata validata su alcuni gruppi di studenti, eterogenei per interesse e formazione, e testata anche in modalità peer education, ottenendo sempre risultati molto positivi. Una seconda TLS è legata all’idea-chiave “Metodi e strumentazione” e sfrutta il Gecko Tape® come reticolo di diffrazione, flessibile e deformabile, per l’apprendimento attivo dell’ottica. Viene proposta anche in flipped-classroom con materiali didattici appositamente preparati. I materiali prodotti, tra cui filmati e videotutorial, sono disponibili sul sito, completamente rinnovato, www.nanolab.unimore.it, e sono la base per corsi di aggiornamento per insegnanti, di cui uno tenuto nel 2018, ed uno prossimo venturo. 1. I. Malsch; Nanotech. Rev 3, 211 (2014) 2. M. Prince; J. Engr.Ed Rev 93, 223 (2004) 3. http://www.nanolab.unimore.it 4. E. Etkinaa, Physics World 27, 48 (2014) 5. R.W. Bybee; Science& children 51,10 (2014) 6. U. Besson et al. Am. J. Phys. 75, 1106 (2007) 7. V. Montalbano Proceedings of the GIREP-MPTL, 863 (2014)
Nanotechnologies are already part of everyday life and are indicated in HO2020 as fundamental key-enabling technologies for the scientific, economic and social development of EU. EU has indeed recommend the introduction of nanoscience and nanotechnology in high school curricula [1] since the beginning of the new millennium, due to their highly interdisciplinary character and also because they are particularly well-suited for effective hands-on activities [2]. One of the most relevant goal of nanoscience is to design and realize novel materials with peculiar properties, the so-called functional materials, by fine tuning their structure, chemical composition and morphology at the micro and nanoscale. Indeed, the microscopic characteristics of such materials strongly affect their macroscopic properties, often in highly surprising ways. Several functional materials are nowadays easily purchased and are used in the school labs to trigger pupils’ curiosity and interest, exploiting the so-called wow-effect. The Unimore Nanolab project [3] goes beyond this approach, designing fully quantitative experiments based on functional materials, which are aimed at introducing selected key-concepts (“big-ideas”) in nanoscience. In this PhD thesis work, as a part of the Nanolab project, I designed and test a few new teaching learning sequences (TLS), developing a novel educational approach to experimental activities, inspired by ISLE (Investigative Science Learning Environment)[4] and Instructional 5E models[5]. Tribology, i.e. the study of friction, wear and adhesion phenomena, is an extremely active field of research of paramount technological relevance. Achieving a comprehensive understanding of these phenomena at the nano- and meso-scale is currently an open issue. As far as education is concerned, friction has been considered a trivial topic which deserved little attention in traditional high-school curricula. In fact, it actually provides an appealing way to introduce fundamental interdisciplinary concepts, such as atomic and molecular interactions and their key role in determining the behaviour and properties of two surfaces in intimate contact [6-7]. In this work, I designed a TLS on friction and wetting, which inquires the properties of the Gecko Tape ®, a micro-structured adhesive, bio-inspired by the gecko feet. The TLS aims to convey one of nanoscience Big Ideas, i.e. Structure is function and underlying the strict connections between physics and chemistry. The teaching sequence is intended to mimic the different steps of a true scientific research, including results dissemination and discussion.This TLS has been validated with a few groups of students, with different backgrounds and levels of involvement, and also tested in a peer education set with very good results. A second TLS, addressing the big ideas "Tools and Instrumentation" was also designed, exploiting Gecko Tape® as a flexible and deformable diffraction grating. This activity is part of a sequence regarding optics and is also proposed in a flipped-classroom approach. All the designed educational materials, including films and video tutorials, are available on-line and have been also used in in-service teachers training activities. 1. I. Malsch; Nanotech. Rev 3, 211 (2014) 2. M. Prince; J. Engr.Ed Rev 93, 223 (2004) 3. http://www.nanolab.unimore.it 4. E. Etkinaa, Physics World 27, 48 (2014) 5. R.W. Bybee; Science& children 51,10 (2014) 6. U. Besson et al. Am. J. Phys. 75, 1106 (2007) 7. V. Montalbano Proceedings of the GIREP-MPTL conference, 863 (2014)

We have developed a high density lipoprotein (HDL)-based platform for transport and delivery of hydrophobic gold nanoparticles (AuNP). The ability of apolipoprotein E3 (apoE3) to act as a ligand for the low-density lipoprotein receptor (LDLr) was exploited to gain entry of HDL with AuNP into glioblastoma cells. AuNP of 3, 10 and 17 nm diameter, the latter two synthesized by phase transfer process, were solubilized by integration into reconstituted HDL (rHDL). Absorption spectroscopy indicated the presence of stable particles with signature surface plasmon bands, while electron microscopy revealed AuNP embedded in rHDL core. The rHDL-AuNP complexes displayed robust binding to the LDLr, were internalized by the glioblastoma cells, and appeared as aggregated AuNP in the endosomal-lysosomal compartments. The rHDL-AuNP generated little cytotoxicity and were able to cross the blood brain barrier. The findings bear significance since they offer an effective means of delivering AuNP across tumor cell membrane.

We present a versatile biosensing strategy that uses nucleic acids programmed to undergo an isothermal toehold mediated strand displacement in the presence of analyte. This rearrangement results in a double biotinylated duplex formation that induces the rapid aggregation of streptavidin decorated quantum dots (QDs). As biosensor reporters, QDs are advantageous to organic fluorophores and fluorescent proteins due to their enhanced spectral and fluorescence properties. Moreover, the nanoscale regime aids in an enhanced surface area that increase the number of binding of macromolecules, thus making cross-linking possible. The biosensing transduction response, in the current approach, is dictated by the analysis of the natural single particle phenomenon known as fluorescence intermittency, or blinking is the stochastic switching of fluorescence intensity ON (bright) and OFF (dark) states observed in single QD or other fluorophores. In contrast to binary blinking that is typical for single QDs, aggregated QDs exhibit quasi-continuous emission. This change is used as an output for the novel biosensing techniques developed by us. Analysis of blinking traces that can be measured by laser scanning confocal microscopy revealed improved detection of analytes in the picomolar ranges. Additionally, this unique biosensing approach does not require the analyte to cause any fluorescence intensity or color changes. Lastly, this biosensing method can be coupled with therapeutics, such as RNA interference inducers, that can be conditionally released and thus used as a theranostic probes.

Nanofabrication through multiphoton absorption has generated considerable interest because of its unique ability to generate 2D and 3D structures in a single laser-direct-write step as well as its ability to generate feature sizes well below the diffraction limited laser spot size. The majority of multiphoton fabrication has been used to create 3D structures of photopolymers which have applications in a wide variety of fields, but require additional post-processing steps to fabricate conductive structures. It has been shown that metal ions can also undergo multiphoton absorption, which reduces the metal ions to stable atoms/nanoparticles which are formed at the laser focal point. When the focus is located at the substrate surface, the reduced metal is deposited on the surface, which allows arbitrary 2D patterning as well as building up 3D structures from this first layer. Samples containing the metal ions can be prepared either in a liquid solution, or in a polymer film. The polymer film approach has the benefit of added support for the 3D metallic structures; however it is difficult to remove the polymer after fabrication to leave a free standing metallic structure. With the ion solution method, free standing metallic structures can be fabricated but need to be able to withstand surface tension forces when the remaining unexposed solution is washed away.

So far, silver nanowires with resistivity on the order of bulk silver have been fabricated, as well as a few small 3D structures. This research focuses on the surfactant assisted multiphoton reduction of silver ions in a liquid solution. The experimental setup consists of a Coherent Micra 10 Ultrafast laser with 30fs pulse length, 80MHz repetition rate, and a wavelength centered at 800nm. This beam is focused into the sample using a 100x objective with a N.A. of 1.49. Silver structures such as nanowires and grid patterns have been produced with minimum linewidth of 180nm. Silver nanowires with resistivity down to 6x bulk silver have been fabricated. Three-dimensional structures have also been fabricated with up to a 10µm height at a thickness of 500nm. This method can fabricate structures with the possible applications in plasmonic metamaterials, photonic crystals, MEMS/NEMS and micro/nanocircuitry.

III-V optoelectronic device integration in a CMOS post-process compatible manner is important for the intimate integration of silicon-based electronic and photonic integrated circuits. The low temperature, self-catalyzed growth of high crystalline quality Wurtzite-phase InP nanopillars directly on silicon presents a viable approach to integrate high performance nano-optoelectronic devices.

For the optical transmitter side of the photonic link, InGaAs quantum wells have been grown in a core-shell manner within InP nanopillars. Position-controlled growth with varying pitch is used to systematically control emission wavelength across the same growth substrate. These nanopillars have been fabricated into electrically-injected quantum well in nanopillar LEDs operating within the silicon transparent 1400–1550 nm spectral window and efficiently emitting micro-watts of power. A high quality factor (Q ~ 1000) undercut cavity quantum well nanolaser is demonstrated, operating in the silicon-transparent wavelength range up to room temperature under optical excitation.

We also demonstrate an InP nanopillar phototransistor as a sensitive, low-capacitance photoreceiver for the energy-efficient operation of a complete optical link. Efficient absorption in a compact single nanopillar InP photo-BJT leads to a simultaneously high responsivity of 9.5 A/W and high 3dB-bandwidth of 7 GHz.

For photovoltaic energy harvesting, a sparsely packed InP nanopillar array can absorb ~90% of the incident light because of the large absorption cross section of these near-wavelength nanopillars. Experimental data based on wavelength and angle resolved integrating sphere measurements will be presented to discuss the nearly omnidirectional absorption properties of these nanopillar arrays.

At present modulators in communications industry utilize non-linear materials like indium tin oxide (ITO) and DLD-164 as a dielectric, which makes the fabrication process cumbersome and expensive. This thesis discusses the possibility of using only gold and air as conductor and dielectric to characterize a signal modulating device. Both electro-absorption modulation (EAM) and phase change driven modulation is possible with the design. For the change in phase a length of 2.992 µm for the modulating arm of a Mach-Zehnder modulator (MZM) was achieved for operation at 525 nm. High absorptions of electromagnetic (EM) waves was seen at the 480 nm mark allowing a length of just 4.95 µm for EAM. The results suggest that an all plasmonic noble metal modulator utilizing air as a dielectric is possible for operation in the visible 400 nm to 700 nm range. The concept is supported by proof-of-principle based simulations.

This thesis proposes a novel idea of an all plasmonic modulator driven by changes in free carrier concentration in gold and surface plasmon polariton (SPP) excitations under an applied potential. The prototype model is simulated using a commercial finite difference time domain solver. The simulation enviro nment allows Maxwell’s equations to be solved in the time domain to investigate light propagation and absorption characteristics under an externally applied electric potential. The free carrier concentration dependent permittivity of gold is exploited to investigate possible applications in nano-photonics and optical communications.

Vertically oriented graphene nanosheets (VOGN) synthesized by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) have been fabricated as electrical double layer capacitors (EDLCs). The relatively open morphology of the films provided good frequency response, but had limited capacitance compared to present day activated carbon EDLCs. The objective of this research was to improve the capacitance of these films to a commercially viable level while maintaining sufficient frequency response for AC filtering. The growth of VOGN on Ni and Al substrates has been studied in this work. The native oxide on Ni was thinned at temperatures above ~600ºC with the oxygen from the surface oxide dissolving into the bulk, thus creating a low resistance ohmic contact that reduced the overall equivalent series resistance (ESR). Aluminum was studied because it is the primary substrate material used in electrolytic capacitors. However, it was much more difficult to work with because of its tenacious surface oxide. The maximum capacitance for a 10-minute VOGN/Ni growth observed was ~260µF/cm2, at temperature 850ºC, at 120 Hz, but the morphology was not very ordered. The best combination of capacitance (~160 µF/cm2) and frequency response (phase angle near -85º up to ~3000 Hz) was grown at 750ºC. The capacitance of VOGN/NI was further improved by using coatings of carbon black by an aerosol spray method. A capacitance of 2.3 mF/cm2 and frequency response phase angle near -90º at 120 Hz was achieved. It is the highest specific capacitance for an EDLC, reported in the literature, to date, suitable for AC filtering. Employing Al as a substrate required a novel method of plasma sputter cleaning of the oxide near the Al melting point (660ºC) and superimposing VOGN growth to prevent further oxidation. Initial results were ~80 µF/cm2 at a temperature of 620ºC with frequency response phase angle near -90º. Modeling of a uniform coating of carbon black (100 nm thick) on this underlying VOGN/Al architecture suggests that a capacitance of near 50 mF/cm2 can be achieved thus making this a potentially viable replacement for electrolytic capacitors. Another approach to commercialization of VOGN/Ni EDLCs has been studied by using a single substrate sheet interdigitated pattern design to create a low volume capacitor. A YAG laser was used to ablate resistance lines in the film resulting in a sinuous, square pattern on a VOGN/Ni coated alumina substrate and utilizing a gel electrolyte to create the EDLC.

The research presented herein exploits the terminal phosphate group on single stranded DNA molecules for direct immobilization to surfaces utilized in semiconductor device fabrication with the end goal of transistor based DNA sensors. As a demonstration of the feasibility of this immobilization strategy DNA immobilization to a variety of surfaces was evaluated for usefulness in biosensor applications. It was determined that DNA can be directly immobilized to a variety of semiconductor surfaces through the terminal phosphate group. Further, this immobilization allows for the hybridization of the immobilized DNA to complementary target in solution. The immobilization of DNA to hafnium dioxide was particularly of interest due to its use in modern nanoelectronics manufacturing. The interactions between DNA and various forms of hafnium dioxide were thoroughly studied in order to understand and optimize the immobilization of DNA to hafnium dioxide for field effect transistor (FET) based DNA sensors. A secondary immobilization route of DNA to a subset of hafnium dioxide surfaces was identified and we have shown that this mechanism is through the nitrogenous bases of the probe molecule. Finally, a novel FET sensor was designed and developed which incorporated III-V materials and hafnium dioxide. The development of the sensor was carried out with the long term goal of determining if FET DNA sensors would have increased sensitivity if fabricated with: 1) the direct immobilization of probe DNA; 2) hafnium dioxide gate dielectric; and/or 3) III-V FET structure. Here, we demonstrate a proof-of-concept device that incorporates these three features and is capable of detecting DNA in solution, DNA immobilized to the surface, and DNA hybridization events.

Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert gas dynamics play a critical role on the catalyst morphology during CNT growth. A novel method for CNT catalyst activation by substrate manipulation is presented. Results of this study build upon prior knowledge of the role of the chemistry of the substrate supporting CNT catalysts. By bombarding sapphire, a substrate known to not support CNT growth, with an argon ion beam, the substrate is transformed into an active CNT growth support by modifying both the structure and chemistry of the sapphire surface. Finally, catalyst formation is studied with transmission electron microscopy by depositing an iron gradient film in order to identify a potential critical catalyst size and morphology for CNT growth. A relationship between catalyst size and morphology has been identified that adds evidence to the hypothesis that a catalysts activity is determined by its size and ability to properly reduce.

Nanotechnology has captured the attention of governments and corporations around the globe. It has become the subject and context for numerous conferences, media articles, websites and scientific research papers. Nano enthusiasts and government officials claim that it is an area that promises new understandings of nature, and use of that understanding to build technologies that might change our lives. Despite the growing hype surrounding this new science, what appears to be lacking is scholarly literature that examines its growth and expansion from a social science perspective. This study addressed this limitation through a sociological analysis of the network of actors, events, rhetorical strategies, practices and instrumentation that went into the construction and growth of nanotechnology. Relying heavily on actor-network theory (ANT), this study focused on a small part of the total network referred to as the knowledge education production process, which involved the enrolment of high school teachers into the nanotechnology network through a series of collaborative workshops -- the Nanotechnology Curriculum Development Project (NCDP) -- with Virginia Polytechnic and State University (Virginia Tech) scientists over a period of two years. By investigating how the nanotechnology network was constructed and maintained, this case study examined the relevance of ANT as nanotechnology moved beyond the laboratory into the public domain of high school education. It looked at the intermediary role of high school science and math teachers and revealed the function of conflict, power, authority, hierarchy, interests, motivations, gender and race in the construction and expansion of scientific networks.
Ph. D.

Given a rapidly developing world, the need exists for inexpensive renewable energy alternatives to help avoid drastic climate change. Photovoltaics have the potential to fill the energy needs of the future, but significant cost decreases are necessary for widespread adoption. Semiconductor nanocrystals, also known as quantum dots, are a nascent technology with long term potential to enable inexpensive and high efficiency photovoltaics. When deposited as a film, quantum dots form unique nanocomposites whose electronic and optical properties can be broadly tuned through manipulation of their individual constituents.

The contents of this thesis explore methods to understand and optimize the optoelectronic properties of PbSe quantum dot films for use in photovoltaic applications. Systematic optimization of photovoltaic performance is demonstrated as a function of nanocrystal size, establishing the potential for utilizing extreme quantum confinement to improve device energetics and alignment. Detailed investigations of the mechanisms of electrical transport are performed, revealing that electronic coupling in quantum dot films is significantly less than often assumed based on optical shifts. A method is proposed to employ extended regions of built-in electrical field, through controlled doping, to sidestep issues of poor transport. To this end, treatments with chemical redox agents are found to effect profound and reversible doping within nanocrystal films, sufficient to enable their use as chemical sensors, but lacking the precision required for optoelectronic applications. Finally, a novel doping method employing "redox buffers" is presented to enact precise, stable, and reversible charge-transfer doping in porous semiconductor films. An example of oxidatively doping PbSe quantum dot thin films is presented, and the future potential for redox buffers in photovoltaic applications is examined.

Про наноповерхні дізналися ще в 70-ті роки минулого століття. Першим таким нововведенням був «Ефект лотоса», який був відкритий німецькими ботаніками В.Бартлоттом та Г.Найнцісом. Дослідження наноповерхонь є дуже перспективним, тому у наш час наноповерхні вивчаються багатьма країнами світу і запроваджуються у життя.

The desire for smaller, faster, stronger, more efficient, more selective and more sensitive devices provides the impetus for research into materials at the nanoscale. Atomically thin carbon, arranged in a flat honeycomb lattice, where each carbon is bonded to 3 others by sp2 carbon bonds forms graphene. This material is of particular interest to researchers as it has the potential to enable new functionalities as well as improve existing devices in a number of the desired ways. Graphene is a material particularly relevant to electronics, energy, sensing and bio-medical applications however limitations in synthesising and incorporating it into devices present a major hurdle in its use. These two key issues need to be resolved to allow a new generation of graphene-enabled devices to be produced. Techniques to synthesise graphene are varied. They are predominantly made up of wet chemistry, mechanical cleaving and chemical vapour deposition (CVD) techniques. These techniques, however, have yet to resolve the problems related to making graphene in a device compatible manner nor allowing its transfer onto a device. One of the most promising techniques is CVD on a copper catalyst at elevated temperatures. This technique though, requires high temperatures of ~900°C, lacks appreciable control and requires the etching or chemical treatment of the catalyst to separate it from the graphene grown. It does however allow scalability and produces high quality and large crystal grain graphene. The work outlined in this thesis targets graphene growth on copper, however, instead of using elevated temperatures a plasma is implemented to allow growth. Plasma-based approaches to graphene growth have been limited. This work utilises a custom built system featuring an inductively coupled plasma generated using a radio frequency power supply operating at 13.56 MHz. The set-up allows the generation of a dense, low temperature plasma which has beneficial properties which can be harnessed for graphene growth. Through plasma heating, selective etching, ionisation, and plasma enhancement of surface processes, single layer graphene can be grown without the need for an additional heating source. Graphene can be grown at temperatures as low as 220 °C. This process features many of the same beneficial features of the copper CVD process however trades crystal size and quality for significantly reduced temperatures. Furthermore, this process has provided a new method for transferring graphene from the catalyst to a device. The transfer method presented here uses no etchants or chemicals at all, just deionised water. This process therefore offers solutions to two of the major problems for incorporating graphene into new devices: reduced growth temperature and non-destructive, simple graphene transfer. This novel growth process was investigated further to elucidate some of the interesting phenomena occurring allowing graphene growth. Control over the plasma process was demonstrated, with different graphene films produced. These films differ by quality and morphology, both horizontal and vertically aligned graphene materials can be grown. It was discovered that by controlling the carbon concentration in the plasma growth of vertical or horizontal structures can be controlled. Considerable changes are also made to the catalyst during plasma exposure. Crystallography and surface energy can be tuned and modified through plasma exposure. There are real benefits to modifying the crystallography of the catalyst for graphene growth. Modification of the catalyst and the graphene film was also found to be crucial for allowing the film to be removed from the catalyst. By modifying the plasma before and after graphene growth we are able to determine whether or not the film can decouple from the catalyst. The properties of the films were found to be dependent on both the growth conditions and the transfer of the films. Whilst control exists in the plasma environment in modifying crystal properties it was found that the films electronic properties was more influenced by the transfer. The plasma based process developed in this thesis offers benefits of catalyst reuse, energy efficiency, control, versatility and simplicity and is presented as a viable alternative to other approaches to synthesise graphene for new generation graphene-enabled devices.

xvii, 183 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
In recent years, nanoscience has evolved from a multidisciplinary research concept to a primary scientific frontier. Rapid technological advancements have led to the development of nanoscale device components, advanced sensors, and novel biomimetic materials. However, potential negative impacts of nanomaterials are sometimes overlooked during the discovery phase of research. The implementation of green chemistry principles can enhance nanoscience by maximizing safety and efficiency while minimizing the environmental and societal impacts of nanomaterials. This dissertation introduces the concept of green nanosynthesis, demonstrating the application of green chemistry to the synthesis of nanornaterials. A comprehensive review of the synthesis of metal nanomaterials is presented, demonstrating how individual green chemistry principles can improve traditional synthetic routes as well as guide the design of new materials. Detailed examples of greener syntheses of functionalized gold nanoparticles with core diameters of 2-10 nm are described in subsequent chapters, beginning with a method for functionalizing citrate-stabilized gold nanoparticles that are desirable for advanced applications. Although citrate-stabilized gold nanoparticles can be easily produced from a classic procedure using mild reagents and benign methods, functionalization via ligand exchange is often unsuccessful. It was discovered that an ill-defined layer comprised of citrate and other ligands interferes with functionalization processes. By removing excess citrate in a manner where overall structure and stability is maintained, gold cores produced by this route are readily functionalized by incoming thiols, affording unprecedented control over surface composition and functionality. A direct route to functional nanomaterials using Bunte salt precursors is discussed next, describing the use of easily synthesized shelf-stable alternatives to thiols in the preparation of water-soluble gold nanoparticles. Control of core size and surface chemistry is demonstrated through simple manipulation of reagent ratios, yielding products similar to those produced by traditional direct syntheses which rely on the use of thiols. The use of functionalized nanoparticles as "building blocks" for more complex structures was demonstrated in self-assembly processes. Cationic gold particles were deposited upon DNA scaffolds to create linear arrays. A discussion of the future outlook of green nanosynthesis concludes this work, identifying immediate challenges and long-term goals. This dissertation contains previously published and co-authored materials.
Adviser: James E. Hutchison

Frequency multiplication is an effect that arises in electronic components that exhibit a non-linear response to electromagnetic stimuli. Barriers to achieving very high frequency response from electronic devices are the device capacitance and other parasitic effects such as resistances that arise from the device geometry and are in general a function of the size of the device. In general, smaller device geometries and features lead to a faster response to electromagnetic stimuli. It was posited that the small size of the silicon nanowires (SiNWs) would lead to small device capacitance and spreading resistance, thus making the silicon nanowires useful in generating microwave and terahertz radiation by frequency multiplication. To verify this hypothesis, silicon nanowires based devices were fabricated and investigated using two experimental setups. The setups were designed to allow the investigation of the nanowire based devices at low frequencies and at high frequencies. Both setups consisted of an RF/microwave source, filters, waveguide, and a spectrum analyzer. They also allowed the characterization of the samples with a semiconductor parameter analyzer. The first step in the investigation of the SiNW devices was to install them in the waveguides and perform Current-Voltage (I-V) sweeps using the semiconductor parameter analyzer. The devices that exhibited the non-linear I-V characteristics typical of diodes were further investigated by first exposing them to 70MHz and 500MHz frequencies in the low frequency setup and then to 50GHz microwaves in the high frequency setup. The response of the devices was captured with a spectrum analyzer. The results demonstrate that the non-linear effect of frequency multiplication is present in nanowire devices from DC to 100GHz. The HF setup provides a platform that with an appropriate detector can be used to detect harmonics of the SiNWs in sub-millimeter/THz region of the electromagnetic spectrum.

Optical rectennas, which are micro-antennas to convert optical-frequency radiation to alternating current combined with ultrahigh-speed diodes to rectify the current, can in principle provide high conversion efficiency solar cells and sensitive detectors. Currently investigated optical rectennas using metal/insulator/metal (MIM) diodes are limited in their RC response time and poor impedance matching between diodes and antennas. A new rectifier, the geometric diode, can overcome these limitations. The thesis work has been to develop geometric diode rectennas, along with improving fabrication processes for MIM diode rectennas. The geometric diode consists of a conducting thin-film, currently graphene, patterned into a geometry that leads to diode behavior. In contrast with MIM diodes that have parallel plate electrodes, the planar structure of the geometric diode provides a low RC time constant, on the order of 10^-15 s, which permits operation at optical frequencies. Fabricated geometric diodes exhibit asymmetric DC current-voltage characteristics that match well with Monte Carlo simulations based on the Drude model. The measured diode responsivity at DC and zero drain-source bias is 0.012 A/W. Since changing the gate voltage changes the graphene charge carrier concentration and can switch the majority charge type, the rectification polarity of the diode can be reversed. Furthermore, the optical rectification at 28 THz has been measured from rectennas formed by coupling geometric diodes with graphene and metal bowtie antennas. The performance of the rectenna IR detector is among the best reported uncooled IR detectors. The noise equivalent power (NEP) of the rectenna detector using geometric diode was measured to be 2.3 nW Hz^-1/2. Further improvement in the diode and antenna design is expected to increase the detector performance by at least a factor of two. Applications for geometric diodes and graphene bowtie antennas include detection of terahertz and optical waves, ultra-high speed electronics, and optical power conversion.

Photovoltaic (PV) devices based on PbS quantum dot (QD) solids demonstrate high photon-to-electron conversion yields. However, record power conversion efficiencies remain limited mainly due to bulk and interfacial defects in the light absorbing material (QD solids). Interfacial defects can be formed when a semiconductor, such as QD solid, is contacted by another material and may predetermine the semiconductor/metal or semiconductor/metal-oxide junction properties. The objective of the work described in this dissertation was set to explore whether electrochemical contacting using liquid electrolytes can provide sufficient means of contacting the QD solids to investigate their PV performance without introducing the unwanted interfacial defects. I have initially focused on optimizing processing conditions for efficient QD solids deposition and studied their photovoltaic properties in a standardized solid-state, depleted heterojunction solar cell configuration. Further, a liquid contacting method was developed to study the relationship between photovoltages of QD solids and the energetics (e.g. reduction potentials) of the liquid contacting media. This electrochemical contacting of PbS QD solids was achieved by using anhydrous liquid electrolytes containing fast, non-coordinating, outer-sphere redox couples. Depending on the energetics of a redox couple, both rectifying and non-rectifying (Ohmic) PbS QD solid/electrolyte junctions were successfully formed with both p- and n-type QD solids. Furthermore, application of the liquid solution contacting method in studies of the PbS QD solids has unprecedentedly demonstrated that an ideal behavior of the photovoltage changes with respect to the changes in the energetics of the contacting media can be achieved. This fact supports the initially proposed hypothesis that such liquid contacting method will not introduce surface defects to the studied QD materials, allowing for their intrinsic properties to be better understood. The applicability of this method to both p- and n- type QD solids was demonstrated. Finally, a better understanding of the relationships between the surface and ligand chemistries of both p- and n-type QD solids and their photovoltaic properties was possible via applications of such method in conjunction with XPS and UPS studies.

This report considers both contributions and adverse consequences, uncertainties, and unknownrelationships that are potentially involved in the advances of techno-economic and humanisticinterests towards the advances in Nanosciences and Nanotechnologies (N&N). Because of thedistinctive physical and chemical properties of materials at nanoscales, which have not beenunderstood deeply yet, besides the huge potentials to benefit many areas of research andapplication, it is recognized that application of N&N may raise new ecological, health and safety,socio-economic, and regulatory challenges that will require scientific, techno-economic, andsocietal considerations. A comprehensive literature survey of peer reviewed journals, books, andother authoritative sources indicate that there have been very few studies on these fundamentalaspects and the research investments are mainly sponsored for market purposes, rather than forpure scientific structure-function discoveries or sustainability attitudes. The overarching issue ofimportance in this study is to consider the high level of uncertainties and lack of knowledge inN&N, and the great potential threats and impacts of engineered nanoproducts that can be eitherin form of known-unknowns or even unknown-unknowns. Moreover, measures of improvementto govern N&N developments to become sustainable, including public communication, call forpure and high quality non-prescribed research on unknown characteristics of N&N, health and environmental friendliness based on a life cycle approach, and the industrial ecology approach,together with implementation of the related results in practice have been suggested.
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