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1
Sethi, Manish. "INTERACTIONS AND EFFECTS OF BIOMOLECULES ON AU NANOMATERIAL SURFACES." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/822.
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Au nanoparticles are increasingly being used in biological applications. Their use is of interest based upon their unique properties that are achieved at the nanoscale, which includes strong optical absorbances that are size and aggregation state dependent. Such absorbances can be used in sensitive chemical/biological detection schemes where bioligands can be directly attached to the nanoparticle surface using facile methods. Unfortunately, a number of complications persist that prevent their wide-scale use. These limitations include minimal nanoparticle stability in biological-based media of high ionic strength, unknown surface functionalization effects using simple biomolecules, and determining the binding motifs of the ligands to the nanoparticle surface. This situation can be further complicated when employing shaped materials where crystallographic facets can alter the binding potential of the bioligands. We have attempted to address these issues using traditional nanoparticle functionalization techniques that are able to be characterized using readily available analytical methods. By exploiting the optical properties of Au nanomaterials, we have been able to determine the solution stability of Au nanorods in a buffered medium and site-specifically functionalized Au nanomaterials of two different shapes: spheres and rods. Such abilities are hypothesized to be intrinsic to the bioligand once bound to the surface of the materials. Our studies have focused mainly on simple amino acids that have demonstrated unique assembly abilities for the materials in solution, resulting in the formation of specific patterns. The applications for such capabilities can range from the use of the materials as sensitive biochemical sensors to their directed assembly for use as device components.
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della, Sala Flavio. "Hydrazone exchange in nanoparticle monolayers : a dynamic covalent approach for controlling nanomaterial properties." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6766.
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This Thesis reports the synthesis, purification and characterisation of gold nanoparticles (NPs) functionalised with a monolayer of hydrazone ligands in order to perform post-synthetic manipulations of the NP-bound monolayer exploiting dynamic covalent chemistry. NP post-synthetic manipulation based on reversible non-covalent interactions between oligonucleotides represents a promising approach to achieve functionalisation and self-assembly for potential applications in biology and medicine. However, the stability of these nanosystems is ensured only in a narrow window of environmental conditions. On the other hand, irreversible covalent strategies potentially allow the full range of synthetic chemistry to be exploited but they provide poor control over the manipulation of the NP-bound monolayer and can only produce kinetically controlled amorphous NP aggregates. Dynamic covalent chemistry represents an interesting and an attractive alternative approach because it would combine the reversibility of non-covalent interactions with the stability of covalent bonds. By this way, ligand-functionalised NPs could be manipulated in order to introduce a large variety of molecular functionalities on the NP surface not only to subtly tune the NP physicochemical properties but also to access an entire range of novel nanomaterials.
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Owens, Cherie. "INVESTIGATIONS INTO POLYMER AND CARBON NANOMATERIAL SEPARATIONS." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345485388.
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Hurst, Angela L. "The Design and Synthesis of Corannulene-Based Nanomaterial." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1271706999.
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Shumlas, Samantha Lyn. "Characterization of Carbon Nanomaterial Formation and Manganese Oxide Reactivity." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/419544.
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ChemistryPh.D.
Characterization of a material’s surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. With regard to the synthesis of novel carbonaceous materials, the irradiation of gaseous methane with ultrashort pulse laser irradiation showed the production of carbon nanospheres. Products were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet (UV) Raman spectroscopy, and infrared spectroscopy. Increasing the pressure of methane from 6.7 to 133.3 kPa showed an increase in the median diameter of the spheres from ~500 nm to 85 nm. Particles with non-spherical morphologies were observed by TEM at pressures of 101.3 kPa and higher. UV Raman spectroscopy revealed that the nanospheres were composed of sp2 and sp3 hybridized carbon atoms, based on the presence of the carbon D and T peaks. A 30% hydrogen content was determined from the red shift of the G peak and the presence of a high fluorescence background. Upon extending this work to mixtures of methane, argon, and hydrogen it was found that carbon nanomaterials with varying composition and morphology could be obtained. Upon mixing methane with other gases, the yield significantly dropped, causing flow conditions to be investigated as a method to increase product yield. Raman spectra of the product resulting from the irradiation of methane and argon indicated that increasing the argon content above 97% produced nanomaterial composed of hydrogenated amorphous carbon. In a second research effort, the effect of simulated solar radiation on the oxidation of arsenite [As(III)] to arsenate [As(V)] on the layered manganese oxide, birnessite, was investigated. Experiments were conducted where birnessite suspensions, under both anoxic and oxic conditions, were irradiated with simulated solar radiation in the presence of As(III) at pH 5, 7, and 9. The oxidation of As(III) in the presence of birnessite under simulated solar light irradiation occurred at a rate that was faster than in the absence of light at pH 5. At pH 7 and 9, As(V) production was significantly less than at pH 5 and the amount of As(V) production for a given reaction time was the same under dark and light conditions. The first order rate constant (kobs) for As(III) oxidation in the presence of light and in the dark at pH 5 were determined to be 0.07 and 0.04 h−1 , respectively. The As(V) product was released into solution along with Mn(II), with the latter product resulting from the reduction of Mn(IV) and/or Mn(III) during the As(III) oxidation process. Experimental results also showed no evidence that reactive oxygen species played a role in the As(III) oxidation process. Further research on the triclinic form of birnessite focused on its activation for water oxidation. Experiments were performed by converting triclinic birnessite to hexagonal birnessite in pH 3, 5, and 7 DI water with stirring for 18 hrs. Once the conversion was complete, the solid samples were characterized with TEM and x-ray photoelectron spectroscopy (XPS). The resulting hexagonal birnessites from experiment at pH 3, 5, and 7 possessed the same particle morphology and average surface oxidation states within 1% of each other. This observation supported the claim that upon transformation, Mn(III) within the sheet of triclinic birnessite migrated into the interlayer region of the resulting hexagonal birnessite. Furthermore, the migration of Mn(III) into the interlayer and formation of the hexagonal birnessite led to an increased chemical reactivity for water oxidation compared to the bulk. Electrochemical studies showed that the overpotential for water oxidation associated with the pH 3, 5, and 7 samples was 490, 510, and 570 mV, respectively. In another set of experiments, ceric ammonium nitrate was used to test birnessite for water oxidation reactivity. These experiments showed that the pH 3 birnessite produced the most O2 of all the samples, 8.5 mmol O2/mol Mn, which was ~6 times more than hexagonal birnessite which did not undergo post-synthesis exposure to low pH conditions.
Temple University--Theses
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Lehman, Sean E. "Spectroscopic studies of silica nanoparticles: magnetic resonance and nanomaterial-biological interactions." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2109.
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Primarily concerned with manipulation and study of matter at the nanoscale, the concept of nanoscience encompasses ideas such as nanomaterial synthesis, characterization, and applications to modern scientific and societal problems. These problems encompass a broad range of issues such as energy storage and conversion, medical diagnostics and treatment, environmental remediation and detection, carbon economy and as well as many others. Silica nanoparticles of porous morphology have broad application to many of these issues. In particular, the utility of silica nanoparticles is facilitated by their large intrinsic surface area, tunable surface chemistry, and synthetic variability in both their size and morphology. This facilitates applications to these problems. However, extensive characterization and deeper understanding is needed before full implementation in key applications can be realized.
The work described in this thesis aims to explore fundamental and applied characterization of silica nanoparticles that might be used in biomedical and environmental applications. Fundamental studies of functionalized nanomaterials using NMR spectroscopy reveal complex, dynamic phenomena related to-and ultimately deriving from-the intrinsic and/or modified surface chemistry. Applied studies of nanomaterial-biological interfaces demonstrate free radical chemistry as dominating the toxic response of the materials when exposed to biological systems of interest. Characterization of protein adsorbed on the interface reinforces the ubiquitous nature of protein adsorption on nanomaterial surface in biological and environmental media. Overall, this work illuminates and highlights complex changes that take place in aqueous solution for silica nanoparticles of varied morphology and surface chemistry.
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Wang, Junwei. "Chemical doping of metal oxide nanomaterials and characterization of their physical-chemical properties." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333829935.
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Chapman, James Vincent III. "Design and Synthesis of Organic Small Molecules for Industrial and Biomedical Technology Nanomaterial Augmentation." Thesis, University of Colorado at Denver, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10272651.
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Organic chemistry used to augment nanoparticles and nanotubes, as well as more traditional materials, is a subject of great interest across multiple fields of applied chemistry. Herein we present an example of both nanoparticle and nanotube augmentation with organic small molecules to achieve an enhanced or otherwise infeasible application. The first chapter discusses the modification of two different types of Microbial Fuel Cell (MFC) anode brush bristle fibers with positive surface charge increasing moieties to increase quantitative bacterial adhesion to these bristle fibers, and therefore overall MFC electrogenicity. Type-1 brush bristles, comprised of polyacrylonitrile, were modified via the electrostatic attachment of 1-pyrenemethylamine hydrochloride. Type-2 brush bristles, comprised of nylon, were modified via the covalent attachment of ethylenediamine. Both modified brush types were immersed in an E. Coli broth for 1 hour, stained with SYTO® 9 Green Fluorescent Nucleic Acid Stain from ThermoFisher Scientific (SYTO-9), and examined under a Biotek Citation 3 fluorescent microscope to visually assess differences in bacterial adherence. In both trials, a clear increase in amount of bacterial adhesion to the modified bristles was observed over that of the control. The second chapter demonstrates a potential biomedical technology application wherein a polymerizable carbocyanine-type dye was synthesized and bound to a chitosan backbone to produce a water-soluble photothermal nanoparticle. Laser stimulation of both free and NP-conjugated aqueous solutions of the carbocyanine dye with Near-Infrared (NIR) Spectrum Radiation showed an increase in temperature directly correlated with the concentration of the dye which was more pronounced in the free particle solutions.
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Cheng, Xiang. "Gold-Nanoparticle Cored Carbazole Functionalized Star-like Copolymer Hybrid Nanomaterial with Tunable Properties." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522803372777943.
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Guntupalli, Bhargav. "Nanomaterial-Based Electrochemical and Colorimetric Sensors for On-Site Detection of Small-Molecule Targets." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3488.
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An ideal biosensor is a compact and in-expensive device that is able to readily and rapidly detects different types of analytes with high sensitivity and specificity. The affectability of a biosensing methodology is subject to the limit of nanomaterials to transduce the target binding process to an improved perceptible signal, while the selectivity is accomplished by considering the binding and specificity of certain moieties to their targets. Keeping these requirements in mind we have chosen nanomaterials such as carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) that has catalytic properties combined with their size, shape and configuration dependent chemical and physical properties as essential precursors and signaling components for creation of biosensors with tremendous sensitivity. The primary goal of the research work described in this dissertation is to develop and evaluate novel methods to detect various analytes using nanomaterials, at the same time making an affordable architecture for point-of-care (POC) applications. We report here in chapter 3 a simple and new strategy for preparing disposable, paper-based, porous AuNP/M-SWCNT hybrid thin gold films with high conductivity, rapid electron transfer rates, and excellent electrocatalytic properties to achieve multiple analyte electrochemical detection with a resolution that greatly exceeds that of purchased flat gold slides. We further explored the use of nanomaterial-based paper films in more complex matrices to detect analytes such as NADH, which can act as a biomarker for certain cellular redox imbalances and disease conditions. Carbon nanotubes with their large activated surfaces and edge-plane sites (defects) that are ideal for performing NADH oxidation at low potentials without any help of redox mediators minimizing surface fouling in complex matrices is described in chapter 4. With an instrument-free approach in mind we further focused on a colorimetric platform using split cocaine aptamers and gold nanoparticles (AuNPs) to detect cocaine for on-site applications as described in chapter 5. In chapter 5, the split aptamer sequences were evaluated mainly on three basic criteria, the hybridization efficiency, specificity towards the analyte (cocaine), and the reaction time to observe a distinguishable color change from red to blue. The assay is an enzyme-assisted target recycling (EATR) strategy following the principle that nuclease enzyme recognizes probe–target complexes, cleaving only the probe strand releasing the target for recycling. We have also studied the effect of the number of binding domains with variable chain lengths on either side of the apurinic (AP) site. On the basis of our results, we finally shortlisted the sequence combination with maximum signal enhancement fold which is instrumental in development of colorimetric platform with faster, and specific reaction to observe a distinctive color change in the presence of cocaine.
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ROSSO, CRISTIAN. "Development of Novel Catalytic Transformations Towards Valuable Organic Intermediates." Doctoral thesis, Università degli Studi di Trieste, 2021. http://hdl.handle.net/11368/2988355.
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The main scientific objective of this doctoral research was to develop powerful metal-free organic (photo)catalytic systems to efficiently realize new carbon-carbon and carbon-heteroatom bond forming transformations of practical importance. These approaches had to meet the sustainability requirements for green chemical productions by using effective, non-toxic, safe, readily available from economic precursors and potentially recyclable catalysts. In doing so, the preparation of synthetically relevant organic intermediates could be promptly achieved in mild conditions, thus envisaging the potential application of the studied methodologies at preparative scale.
Chapter I introduces the general concepts of organic catalysis, including both polar and radical chemistry. Moreover, it aims to illustrate the physicochemical principles underlying the operative mechanisms of the abovementioned catalytic systems.
Chapter II focuses on the development of a photochemical strategy for the iodoperfluoroalkylation of alkenes triggered by a simple perylene diimide photocatalyst. Successively, this Chapter describes the translation of the established procedure into continuous flow with the aim of up-scaling the preparation of the relevant perfluorinated compounds.
Chapter III discusses the use of photoactive nitrogen-doped carbon dots as catalysts for the light-driven perfluoroalkylation of electron-rich organic substrates. This approach allows the extension of the reactivity to more inert arenes and heteroarenes.
Chapter IV describes the development of green polar organocatalytic methodologies in aqueous media by exploiting the surface amino functionalities of the very same nitrogen-doped carbon nanoparticles. Remarkably, this original approach has been made possible by a fine characterization of the nanomaterial at unprecedent level of detail.
Chapter V shows how another carbon-based nanomaterial, namely carbon nitride, can trigger photochemical aryl amination reactions of high synthetic importance. Interestingly, this transformation is carried out under flow conditions by means of an innovative oscillatory microstructured reactor to overcome the challenges associated with handling solids in flow.
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ĐORĐEVIĆ, LUKA. "Tailoring Organic Matter: from Molecular Design to Functional Supramolecular Species." Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2908098.
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Chemistry beyond the molecule, supramolecular chemistry, has become an essential tool in developing complex chemical systems by mastering intermolecular noncovalent forces. Supramolecular chemistry is considered a key step in the evolution of chemistry to an information science. By appropriate manipulation of noncovalent interactions, the information stored at the molecular level can operate through retrieval, transfer and processing at the supramolecular level. The work presented in this thesis aims at the design of programs, or molecular recognition patterns (hydrogen bonding, donor-acceptors and metal-ion coordination), that operate by spontaneous self-assembly into well-defined and complex supramolecular architectures. Appropriate encoding of the single subunits and processing give access to a variety of systems. Specifically, by integrating active components, functional supramolecular devices are easily accessible. Combination of components that operate with photons or electrons yields photoactive or electroactive devices capable of electron or energy exchange/transfer processes that paved the way to supramolecular photonics and electronics. Additionally, being intrinsically dynamic, supramolecular chemistry provides potential properties such as self-healing, error correction and sensitivity to external stimulus. Self-organization has offered a striking new and chemical approach to the bottom-up nanofabrication and top-down miniaturization approaches in nanoscience and technology, avoiding laborious implementation of physical procedures.
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Sun, Ying. "A Multi-Method Approach for the Quantification of Surface Amine Groups on Silica Nanoparticles." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39480.
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As nanomaterials continue to garner interest in a wide range of industries and
scientific fields, commercial suppliers have met growing consumer demand by readily
offering custom particles with size, shape and surface functionality made-to-order. By
circumventing the challenging and complex synthesis of functionalized nanoparticles,
these businesses seek to provide greater access for the experimentation and
application of these nanoscale platforms.
In many cases, amine functional groups are covalently attached as a surface
coating on a nanoparticle to provide a starting point for chemical derivatization and
commonly, conjugation of biomolecules in medical science applications. Successful
conjugation can improve the compatibility, interfacing and activity of therapeutic and
diagnostic nanomedicines. Amines are amongst the most popular reactive groups used
in bioconjugation pathways owing to the many high-yield alkylation and acylation
reaction are involved in.
For the design of functionalized nanomaterials with precisely tuned surface
chemical properties, it is important to develop techniques and methods which can
accurately and reproducibly characterize these materials. Quantification of surface
functional groups is crucial, as these groups not only allow for conjugation of chemical
species, but they also influence the surface charge and therefore aggregation behavior
of nanomaterials. The loss of colloidal stability of functionalized nanomaterials can often
correspond to a significant if not complete loss of functionality.
Thus, we sought to develop multiple characterization approaches for the
quantification of surface amine groups. Silica nanoparticles were selected as a model
nanomaterial as they are widely used, commercially available, and their surface
chemistry has been investigated and studied for decades. Various commercial batches
of silica nanoparticles were procured with sizes ranging from 20 – 120 nm. Two
colorimetric assays were developed and adapted for their ease-of-use, sensitivity, and
convenience. In addition, a fluorine labelling technique was developed which enabled
analysis by quantitative solid-state 19F NMR and X-ray photoelectron spectroscopy
(XPS). XPS provided data on surface chemical composition at a depth of ≈ 10 nm,
which allowed us to determine coupling efficiencies of the fluorine labelling technique
and evaluate the reactivity of the two assays.
The ensemble of surface-specific quantification techniques was used to evaluate
multiple commercial batches of aminated silica and investigate batch-to-batch variability
and the influence of particle size with degree of functionalization. In addition, resulting
measurements of surface amine content were compared and validated by an
independent method based on quantitative solution 1H NMR, which was developed for
total functional group content determination. This allowed for us to assess the role of
accessibility and reactivity of the amine groups present in our silica particles.
Overall, the objective of this study was to develop a multi-method approach for
the quantification of amine functional groups on silica nanoparticles. At the same time,
we hoped to set a precedent for the development and application of multiple
characterization techniques with an emphasis of comparing them on the basis of
reproducibility, sensitivity, and mutual validation.
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Cazelles, Rémi. "Bioconversion du CO2 en méthanol par un système polyenzymatique encapsulé dans des nanocapsules poreuses de silice." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2013. http://www.theses.fr/2013ENCM0009/document.
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Le déclin de la production de pétrole, lié avec la diminution des matières premières carbonées pour la synthèse chimique ont mené les scientifiques à chercher de nouvelles sources de carbone pour l'industrie chimique. L'utilisation du dioxyde de carbone aiderait à réduire les émissions de gaz à effet de serre tout en fournissant une matière première renouvelable à base de bloc moléculaire en C1. En renversant les équilibres biologiques de trois déshydrogénases, nous avons effectué la biosynthèse multienzymatique en cascade du méthanol à partir de CO2 en utilisant la formiate déshydrogénase de Candida boidinii, la formaldéhyde déshydrogénase de Pseudomonas putida et l'alcool déshydrogénase de Saccacharomyces cerevisiae. Nous avons optimisé le système en ajustant les conditions catalytiques et la quantité relative de chaque déshydrogénase. La phosphite déshydrogénase de Pseudomonas stutzeri a été également choisi comme système de régénération du cofacteur nicotinamide adénine dinucléotide réduit (NADH) parmi 4 systèmes de régénération étudiés. L'ensemble du système a été encapsulé dans des nanocapsules poreuses de silice qui a permis d'augmenter 15 fois les productivités en méthanol. Nous avons montré que les dernières limitations rencontrées, comme la disponibilité du CO2 et l'accumulation du méthanol, peuvent être dépassées en mettant en place un système catalytique en flux continu en phase gazThe decline of oil production, linked with the decrease of carbon feedstock for chemical synthesis leads scientist to find new sources of carbon for the chemical industry. Use of carbon dioxide would help to reduce the greenhouse gas emissions while providing a renewable feedstock of C1 molecular building blocks. By reversing the biological metabolic reaction pathway of three dehydrogenase, we carried out multistep multienzyme biosynthesis of methanol from CO2 using formate dehydrogenase from Candida Boidinii, formaldehyde dehydrogenase from Pseudomonas Putida and alcohol dehydrogenase from Saccacharomyces cerevisiae. We improved the system active by adjusting the catalytic conditions and the relative quantity of each dehydrogenase. Phosphite dehydrogenase from Pseudomonas stutzeri was also chosen among 4 different studied systems to be introduced into the catalysis as a cofactor regenerating system for reduced nicotinamide adenine dinucleotide. The enzymatic system was then immobilized by encapsulation into novel phospholipid templated silica nanocapsules, allowing an increase of the methanol productivity by a factor 15. We show that the last limitation of the process as substrate availability and product accumulation can be overcome by running continuous enzymatic flow conversion in a gas phase
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Inaba, Hiroshi. "Structural design of cell-penetrating protein needles toward development of intracellular delivery systems." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/195979.
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Hardas, Sarita S. "INVESTIGATIONS OF OXIDATIVE STRESS EFFECTS AND THEIR MECHANISMS IN RAT BRAIN AFTER SYSTEMIC ADMINISTRATION OF CERIA ENGINEERED NANOMATERIALS." UKnowledge, 2012. http://uknowledge.uky.edu/chemistry_etds/7.
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Advancing applications of engineered nanomaterials (ENM) in various fields create the opportunity for intended (e.g. drug and gene delivery) or unintended (e.g. occupational and environmental) exposure to ENM. However, the knowledge of ENM-toxicity is lagging behind their application development. Understanding the ENM hazard can help us to avoid potential human health problems associated with ENM applications as well as to increase their public acceptance. Ceria (cerium [Ce] oxide) ENM have many current and potential commercial applications. Beyond the traditional use of ceria as an abrasive, the scope of ceria ENM applications now extends into fuel cell manufacturing, diesel fuel additives and for therapeutic intervention as a putative antioxidant. However, the biological effects of ceria ENM exposure have yet to be fully defined. Both pro-and anti-oxidative effects of ceria ENM exposure are repeatedly reported in literature. EPA, NIEHS and OECD organizations have nominated ceria for its toxicological evaluation. All these together gave us the impetus to examine the oxidative stress effects of ceria ENM after systemic administration.
Induction of oxidative stress is one of the primary mechanisms of ENM toxicity. Oxidative stress plays an important role in maintaining the redox homeostasis in the biological system. Increased oxidative stress, due to depletion of antioxidant enzymes or molecules and / or due to increased production of reactive oxygen (ROS) or nitrogen (RNS) species may lead to protein oxidation, lipid peroxidation and/or DNA damage. Increased protein oxidation or lipid peroxidation together with antioxidant protein levels and activity can serve as markers of oxidative stress.
To investigate the oxidative stress effects and the mechanisms of ceria-ENM toxicity, fully characterized ceria ENM of different sizes (~ 5nm, 15nm, 30nm, 55nm and nanorods) were systematically injected into rats intravenously in separate experiments. Three brain regions (hippocampus, cortex and cerebellum) were harvested from control and ceria treated rats after various exposure periods for oxidative stress assessment. The levels of oxidative stress markers viz. protein carbonyl (PC), 3-nitrotyrosine (3NT), and protein bound 4-hydroxy-2-trans-nonenal (HNE) were evaluated for each treatment in each control and treated rat organ. Further, the levels and activities of antioxidant proteins, such as catalase, glutathione peroxidase (GPx), glutathione reductase (GR), super oxide dismutase (SOD), were measured together with levels of heat shock proteins heme oxygenase -1 and 70 (HO-1 and Hsp-70). In addition, the levels of pro-inflammatory cytokines IL-1β, TNF-α, pro-caspase-3, and autophagy marker LC-3A/B were measured by Western blot technique. In agreement with the literature-proposed model of oxidative stress hierarchy mechanism of ENM-toxicity, the statistical analysis of all the results revealed that the ceria ENM-induced oxidative stress mediated biological response strongly depends on the exposure period and to some extent on the size of ceria ENM. More specifically, a single intravenous injection of ceria ENM induced tier-1 (phase-II antioxidant) response after shorter exposure periods (1 h and 20 h) in rat brain. Upon failure of tier-1 response after longer exposure periods (1 d to 30 d), escalated oxidative stress consequently induced tier-2 and tier-3 oxidative stress responses. Based on our observations made at chronic exposure period (90 d) after the single i.v. injection of ceria ENM, we could extend the model of oxidative stress hierarchy mechanisms for ceria-ENM-induced toxicity. Considering the evaluation of all the oxidative stress indices measured in 3-brain regions, oxidative stress effects were more prominent in hippocampus and the least in cerebellum, but no specific pattern or any significant difference was deduced.
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Yang, Xiangxin. "Sol-gel synthesized nanomaterials for environmental applications." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/884.
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Lewis, Ricky W. "TOXICITY OF ENGINEERED NANOMATERIALS TO PLANT GROWTH PROMOTING RHIZOBACTERIA." UKnowledge, 2016. http://uknowledge.uky.edu/pss_etds/77.
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Engineered nanomaterials (ENMs) have become ubiquitous in consumer products and industrial applications, and consequently the environment. Much of the environmentally released ENMs are expected to enter terrestrial ecosystems via land application of nano-enriched biosolids to agricultural fields. Among the organisms most likely to encounter nano-enriched biosolids are the key soil bacteria known as plant growth promoting rhizobacteria (PGPR). I reviewed what is known concerning the toxicological effects of ENMs to PGPR and observed the need for high-throughput methods to evaluate lethal and sublethal toxic responses of aerobic microbes. I addressed this issue by developing high-throughput microplate assays which allowed me to normalize oxygen consumption responses to viable cell estimates. Oxygen consumption is a crucial step in cellular respiration which may be examined relatively easily along with viability and may provide insight into the metabolic/physiological response of bacteria to toxic substances.
Because many of the most toxic nanomaterials (i.e. metal containing materials) exhibit some level of ionic dissolution, I first developed my methods by examining metal ion responses in the PGPR, Bacillus amyloliquefaciens GB03. I found this bacterium exhibits differential oxygen consumption responses to Ag+, Zn2+, and Ni2+. Exposure to Ag+ elicited pronounced increases in O2 consumption, particularly when few viable cells were observed. Also, while Ni2+ and Zn2+ are generally thought to induce similar toxic responses, I found O2 consumption per viable cell was much more variable during Ni2+ exposure and that Zn2+ induced increased O2 utilization to a lesser extent than Ag+. Additionally, I showed my method is useful for probing toxicity of traditional antibiotics by observing large increases in O2 utilization in response to streptomycin, which was used as a positive control due to its known effects on bacterial respiration.
After showing the utility of my method for examining metal ion responses in a single species of PGPR, I investigated the toxicity of silver ENMs (AgENMs) and ions to three PGPR, B. amyloliquefaciens GB03, Sinorhizobium meliloti 2011, and Pseudomonas putida UW4. The ENM exposures consisted of untransformed, polyvinylpyrrolidone coated silver ENMs (PVP-AgENMs) and 100% sulfidized silver ENMs (sAgENMs), which are representative of environmentally transformed AgENMs. I observed species specific O2 consumption responses to silver ions and PVP-AgENMs. Specifically, P. putida exhibited increased O2 consumption across the observed range of viable cells, while B. amyloliquefaciens exhibited responses similar to those found in my first study. Additionally, S. meliloti exhibited more complex responses to Ag+ and PVP-AgENMs, with decreased O2 consumption when cell viability was ~50-75% of no metal controls and increased O2 consumption when cell viability was <50%. I also found the abiotically dissolved fraction of the PVP-AgENMs was likely responsible for most of the toxic response, while abiotic dissolution did not explain the toxicity of sAgENMs.
My work has yielded a straightforward, cost-effective, and high-throughput method of evaluating viability and oxygen consumption in aerobic bacteria. I have used this method to test a broad range of toxic substances, including, metal ions, antibiotics, and untransformed and transformed ENMs. I observed species specific toxic responses to Ag+, PVP-AgENMs, and sAgENMs in PGPR. These results not only show the clear utility of the methodology, but also that it will be crucial to continue examining the responses of specific bacterial strains even as nanotoxicology, as a field, must move toward more complex and environmentally relevant systems.
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Rosillo-Lopez, Martin. "Preparation, chemistry and applications of novel carbon nanomaterials." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10047526/.
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The isolation of graphene in 2004, and subsequent Nobel Prize for Physics being awarded to Andre Geim and Konstantin Novoselov in 2010, has sparked a renewed interest in graphene around the world due to graphene’s remarkable physical properties such as mechanical stability, optical transparency, impermeability and electrical and thermal conductivity. Graphene Oxide (GO), the oxidised analogue of graphene, has also received much attention owing to its hydrophilic nature. This has made GO a very promising material for aqueous processing, giving it a significant advantage over graphene. In this way, GO has been used in many composite materials, involving biological molecules, metal-organic-frameworks (MOFs) and other hybrid systems. Unfortunately, much uncertainty surrounds the chemical nature of GO, and therefore its chemistry, thus creating a lot of controversy in the literature. Similarly, the preparation of GO also results in lengthy procedures and toxic by-products. To address these issues, this thesis describes the preparation of alternative carbon nanomaterials, as a potential substitute to GO, which have well-defined structures and chemistry and/or reduce the toxic waste produced. The chemistry and applications of these new materials are explored and benchmarked against conventional GO, which is prepared via permanganate oxidation (PM-GO). The preparation of three novel carbon materials, carboxylated graphene nanoflakes (cx-GNFs), nano-graphene oxide (nGO) and GO prepared via dichromate oxidation (DC-GO) are initially reported, along with extensive characterisations. The cx-GNFs are a highly soluble (~100 mg mL-1) and well-defined material consisting of carboxyl groups and unoxidised sp2 carbon only. nGO is prepared via an eco-friendly procedure producing nano-sized GO and DC-GO was prepared in order to elucidate its chemical structure which remains uncertain in the literature. The thermal annealing behaviour of the materials are reported next and the cx-GNFs and the nGO are shown to form carboxylic anhydrides in yields up to 81%, which is the first experimental evidence for this functional group at the graphene edge. The existence of carboxylic anhydrides in dynamic equilibrium with carboxylic acids in water was demonstrated at room temperature for the cx-GNFs, and was consequently exploited for room temperature chemical functionalisations with well-known amines such as ethylenediamine and cysteamine. These functionalised materials were then explored in the context of tagging gold nanoparticles and changing the zeta potential of the native cx-GNFs. The application of these novel materials in heavy-metal extraction is also presented and found to greatly exceed the capacity of PM-GO - by up to six times. Collaborations with other research groups in the field of nano-sensors, ice-nucleation and electrochemistry, revealed the cx-GNFs to be a particularly promising material.
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Dahl, Jennifer Ann. "Synthesis of functional nanomaterials within a green chemistry context /." Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2007. http://hdl.handle.net/1794/6131.
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Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 158-183). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
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Dahl, Jennifer Ann 1976. "Synthesis of functional nanomaterials within a green chemistry context." Thesis, University of Oregon, 2007. http://hdl.handle.net/1794/6131.
Full textAbstract:
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
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Galhotra, Pragati. "Carbon dioxide adsorption on nanomaterials." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/670.
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In this study, CO2 adsorption in the presence and absence of co-adsorbed H2O was investigated on different nanomaterials including nanocrystalline NaY zeolite (nano NaY), ZnO, MgO and λ-Al2O3 nanoparticles as well as mixed phase aluminum nanowhiskers. In the case of nano NaY, FTIR spectra show that a majority of CO2 adsorbs in the pores of these zeolites in a linear complex with the exchangeable cation. Most interesting is the formation of carbonate and bicarbonate on the external surface of nano NaY zeolites, suggesting unique sites for CO2 adsorption on the surface of these small nanomaterials. Adsorption of 18O-labeled carbon dioxide and theoretical quantum chemical calculations confirms the assignment of these different species. For aluminum oxyhydroxide nanowhiskers and gamma alumina in the absence of co-adsorbed water, CO2 reacts with surface hydroxyl groups to yield adsorbed bicarbonate as well as some carbonate. C18O2 adsorption confirms these assignments. In the case of nanoparticulate ZnO, CO2 adsorption under dry conditions results in formation of carbonate, bicarbonates as well as carboxylates. However, in the presence of co-adsorbed water, only carbonate species is formed. 18O-labeled carbon dioxide adsorption and theoretical quantum chemical calculations confirm the vibrational assignment for these different species. Mixed isotope studies with H216O + C18O2 and H218O + C16O2 suggest that there is extensive exchange between oxygen in adsorbed water and oxygen atoms in gas-phase carbon dioxide. CO2 adsorption on MgO surfaces, under dry conditions results in formation of carbonate and bicarbonates. Implications for the use of these nanomaterials in carbon dioxide uptake and storage are discussed.
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Jiang, Ye. "Growth mechanism and surface chemistry of II-VI 2D nanomaterials." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS058.
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Grâce à leurs propriétés optiques et électroniques uniques, les nanocristaux de semi-conducteurs colloïdaux bidimensionnels tels que les nanoplaquettes de chalcogénure de cadmium ont émergé comme une nouvelle classe de nanomatériaux. Tout comme les puits quantiques, ces nanocristaux ont un confinement electronique limité à une seule direction, l'épaisseur qui est contrôlée au niveau atomique. Ces nanoplaquettes colloïdales apparaissent ainsi comme de bons candidats pour la fabrication de dispositifs optoélectroniques. Cependant, leur mécanisme de formation reste sujet à discussion. Ainsi, cette thèse se concentre tout d’abord sur l'étude de la synthèse de nanoplaquettes de CdSe zinc blende et l’effet de la longueur de la chaine aliphatique des carboxylates sur ces dernières, ouvrant ainsi la voie à une meilleure compréhension de la croissance des nanocristaux bidimensionnels.Par la suite, la nature et la localisation de ces ligands carboxylates en surface des nanoplaquettes a été étudié par des techniques de RMN. Cette étude semble confirmer l’effet de la gêne stérique sur la croissance des nanoplaquettes. La RMN du solide en corrélation 13C-1H 2D, se basant sur l’interaction dipolaire, indique que les acétates et les carboxylates à longue chaîne sont très probablement distribués de manière homogène à la surface des nanoplaquettes de CdSe. Dans une dernière partie, j’explore la possibilité d’améliorer les propriétés optiques de nanoplaquettes synthetisées par déposition de couches atomiques en voie colloïdale (c-ALD) en utilisant des recuits, visant à améliorer la structure et la surface des matériauxColloidal two-dimensional semiconductor nanocrystals such as nanoplatelets of cadmium chalcogenides, have emerged as a new class of nanomaterials due to their unique optical and electronic properties. These nanocrystals possess exciton confinement along one direction in analogy to quantum wells, with their thickness controlled at atomic level.Although colloidal two-dimensional nanoplatelets have been considered as potential candidates for the fabrication of optoelectronic devices, their formation mechanism e.g. zinc blende CdSe nanoplatelets is still under debate. Thereby this thesis first focuses on the study of CdSe nanoplatelets synthesis and size of the aliphatic chain in the carboxylate, paving the way to a better understanding of two-dimensional nanocrystals’ growth.Successively surface carboxylate ligands are investigated by NMR techniques which gives us an idea of how surface ligands are composed and relocated. Our study of ligand quantification on nanoplatelets’ surface appears to support the proposed effect from steric hinderance on NPLs growth. 13C-1H 2D correlation solid state NMR based on the dipolar interaction indicates that acetates and long alkyl chain carboxylates should be distributed homogenously on the surface of the CdSe NPLs. In the last part, I explore the possibility of improving the optical features of nanoplatelets synthesized from colloidal atomic-layer-deposition technique through optimizing both interior and surface structures by an annealing process
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Kim, Se Hye. "THE SELF-ASSEMBLY OF FUNCTIONAL NANOMATERIALS." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373638833.
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Schwarb, Ryan Evan. "Synthesis and Characterization of Reactive Core-Shell Nanoparticles." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1332256634.
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Small, William Richard. "Fabrication of novel sensors from nanomaterials." Thesis, University of Hull, 2009. http://hydra.hull.ac.uk/resources/hull:1752.
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This thesis describes the fabrication and characterisation of novel sensors from nanomaterials. These are materials that have at least one length scale in the nanometre region, and in many cases they exhibit fascinating electrical, mechanical or optical properties due to their small size. While their small size makes them candidates for miniaturising macro-scale technologies, many researchers are concerned with exploiting their unique properties in larger scale applications. These might include strong, lightweight building materials based on their mechanical properties, or visual displays based on their electrical and/or optical properties. To achieve transfer of the properties from the nano-scale to the macro-scale however is not straight forward, and there are a number of obstacles that must be overcome. One obstacle is that of processing the nanomaterials, ensuring that their properties do not become lost when they are incorporated into bulk materials or composites due to aggregation or poor interactions with their host matrix. This obstacle will also be addressed in the thesis, as we fabricate and characterise composites incorporating nanomaterials, and develop methods to process these materials into novel sensors. The synthesis and characterisation of a number of different composites has been achieved, incorporating either carbon nanotubes or silver nanowires as the nanomaterials of interest. These have been fabricated using either mixing or in situ polymerisation routes, with surfactants, polysaccharides or conducting polymers as the dispersant. The composites are all soluble in either water or organic solvents to give stable dispersions, and show interesting properties including optical activity, high loading fractions of the nanomaterials and electrochromic behaviour. The methods that we have developed for processing the dispersions are drop deposition, inkjet printing and dielectrophoretic assembly. Drop deposition has been performed as it forms the basis of numerous solution-based processing techniques, and we have investigated specifically the effects of substrate hydrophobicity and the effect of aggregates in the dispersion on the resulting composite films that are formed. We have reported for the first time the inkjet printing of single wall carbon nanotubes, and have printed composite films that show good transparency and high conductivity. A novel method for arresting the structures formed through dielectrophoretic assembly within a gel solution has also been developed. This has led to the fabrication of electrically anisotropic gels, and free-standing 'strings' of yeast cells. Novel sensors have been fabricated through two of our processing methods. Thin films containing carbon nanotubes have been inkjet printed, and show sensitivity to water vapour (with gellan gum as the composite material) and alcohol vapour (with a water soluble conducting polymer as the composite material). A sensor based on biotin-functionalised silver nanowires assembled into a microwire and encapsulated within agarose gel has also been fabricated. This sensor showed sensitivity to streptavidin when the response was measured parallel to the formed microwire, but gave a much lower signal when the response was measured perpendicular to the microwire. This provides a proof of concept that a whole range of biosensors based on assembled silver nanowires into an anisotropic gel can be produced by employing an antigen-antibody strategy, similar to the one shown for biotin-streptavidin.
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Zimmer, John P. (John Philip). "Quantum dot-based nanomaterials for biological imaging." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37888.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.
Includes bibliographical references.
Quantum dot-based fluorescent probes were synthesized and applied to biological imaging in two distinct size regimes: (1) 100-1000 nm and (2) < 10 nm in diameter. The larger diameter range was accessed by doping CdSe/ZnS or CdS/ZnS quantum dots (QDs) into shells grown on the surfaces of pre-formed sub-micron SiO2 microspheres. The smaller diameter range was accessed with two different materials: very small InAs/ZnSe QDs and CdSe/ZnS QDs, each water solubilized with small molecule ligands chosen for their ability not only to stabilize QDs in water but also to minimize the total hydrodynamic size of the QD-ligand conjugates. Indium arsenide QDs were synthesized because nanocrystals of this material can be tuned to fluoresce in the near infrared (NIR) portion of the electromagnetic spectrum, especially in the 700-900 nm window where many tissues in the body absorb and scatter minimally, while maintaining core sizes of 2 nm or less. The QD-containing microspheres were used to image tumor vasculature in living animals, and to generate maps of size-dependent extravasation. With subcutaneously delivered nAs/ZnSe QDs, multiple lymph node mapping was demonstrated in vivo for the first time with nanocrystals. When administered intravenously, < 10 nm QDs escaped from the vasculature, or were efficiently cleared from circulation by the kidney. Both of these behaviors, previously unreported, mark key milestones in the realization of an ideal fluorescent QD probe for imaging specific compartments in vivo. Also presented in this thesis is the growth of single-crystalline cobalt nanorods through the oriented attachment of spherical cobalt nanocrystal monomers.
(cont.) When administered intravenously, < 10 nm QDs escaped from the vasculature, or were efficiently cleared from circulation by the kidney. Both of these behaviors, previously unreported, mark key milestones in the realization of an ideal fluorescent QD probe for imaging specific compartments in vivo. Also presented in this thesis is the growth of single-crystalline cobalt nanorods through the oriented attachment of spherical cobalt nanocrystal monomers.
by John P. Zimmer.
Ph.D.
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Clark, Jonathan Edward. "Unique Applications of Nanomaterials in Separation Science." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282335513.
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Abitbol, Tiffany. "Preparation and characterization of cellulose-based nanomaterials." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104515.
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The interest in cellulose for the purposes of nanocomposite engineering lies in its natural abundance and renewable nature, but also in the truly impressive range of diverse properties which can be accessed from the raw resource. In cellulosic nanocomposite materials, the cellulose component may provide the polymeric matrix for nanoparticles and/or the nanometer-scale constituent. This dissertation presents unique cellulose-based nanocomposites and examines the properties of these materials. Fluorescent cellulose triacetate films are obtained by solvent casting suspensions of CdSe/ZnS quantum dots in polymer solution. The films possess properties characteristic to each distinct component: for instance, the optical absorbance and fluorescence are defined by the quantum dots, and the optical clarity and mechanical properties by the polymer. Surface hydrolysis of the hydrophobic films does not substantially alter bulk film properties but does impart aqueous compatibility, allowing film pieces to be introduced into wet paper-making suspensions to produce novel fluorescent papers. The mixture of quantum dots in cellulose triacetate solution is also employed to electrospin sub-micron diameter, birefringent, fluorescent fibers. A different cellulosic-quantum dot system is explored with the asymmetric, reducing end tagging of cellulose nanocrystals. The target fluorescently-labeled cellulose nanocrystal is achieved but the presence of substantial unreacted starting material seems unavoidable, apparently regardless of reaction conditions. Finally, a cellulosic-nanocomposite hydrogel is prepared by incorporating cellulose nanocrystals into polyvinyl alcohol hydrogels with the aim of reinforcement. The cellulose nanocrystal-loaded hydrogels exhibit distinct morphologies and microstructures, and improved elastic strengths. The thesis discusses the rationale and promise of employing cellulose particles and polymers in nanocomposite materials.L'intérêt d'utiliser la cellulose dans l'ingénierie des nanocomposites repose sur son abondance naturelle, son aspect renouvelable et sa grande variété de propriétés qui sont accessibles à partir de sa source brute. Dans les matériaux nanocomposites, la cellulose peut fournire une matrice polymérique aux nanoparticules ou peut être utiliser comme constituants nanométriques. Cette thèse présente de nouveaux matériaux nanocomposites faits à partir de cellulose et en examine les propriétés uniques. Des films fluorescents de triacétate de cellulose ont été obtenu par coulée-évaporation de suspension de points quantiques de CdSe/ZnS dans une solution de polymère. Ces films possèdent des propriétés caractéristiques distinctives. Par exemple, l'absorbance optique et la fluorescence sont définis par les points quantiques, tandis que la clarté optique et la plasticité sont définis par le polymère. L'hydrolyse à la surface des films hydrophobiques n'a pas altéré de manière significative les propriétés générales du film, mais les a rendu compatibles en milieux aqueux, ce qui a permis l'introduction de morceaux de ces films dans le procédé de fabrication du papier pour produire du papier fluorescent. Le mélange de points quantiques dans une solution de triacétate de cellulose a aussi été employé pour l'électrofilage de fibres fluorescentes ayant des diamètres inférieurs à un micron. Un système différent de points quantiques et de cellulose a aussi été exploré. Dans ce dernier système, le marquage asymétrique d'une des extrémité des nanocristaux de cellulose a été réalisé avec succès. Cependant, même en modifiant les conditions expérimentales, la présence d'une quantité substantielle de matériaux réactifs non-réagis n'a pu être évitée. De plus, un nanocomposite hydrogel à base de cellulose a été préparé par incorporation de nanocristaux de cellulose dans un hydrogel d'alcool de polyvinyle, à des fins de renforcement. L'hydrogel ainsi formé possède une microstructure distincte, une intégrité structurale améliorée, un module plus élevé ainsi qu'une structure résiliente au gonflement d'eau. Cette thèse aborde les principes et applications prometteuses de l'emploi des particules de cellulose et polymères dans la fabrication de matériaux nanocomposites.
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Soehnlen, Eric Scott. "Novel Nanomaterials for Tumor Targeted Imaging and Therapy." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1343055033.
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Xie, Fangyou. "Pressure Driven Desalination Utilizing Nanomaterials." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2204.
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Nanomaterials such as graphene oxide and carbon nanotubes, have demonstrated excellent properties for membrane desalination, including decrease of maintenance, increase of flux rate, simple solution casting, and impressive chemical inertness. Here, two projects are studied to investigate nanocarbon based membrane desalination. The first project is to prepare hybrid membranes with amyloid fibrils intercalated with graphene oxide sheets. The addition of protein amyloid fibrils expands the interlayer spacing between graphene oxide nanosheets and introduces additional functional groups in the diffusion pathways, resulting in increase of flux rate and rejection rate for the organic dyes. Amyloid fibrils also provide structural assistance to the hybrid membrane, which supresses cracking and instability of graphene oxide sheets. The second project is to fabricate polymer nanocomposite membranes with carbon nanotubes encapsulated by polymerized surfactants. The designed polymerizable surfactant forms lyotropic liquid crystalline mesophases in an aqueous medium with hexagonal packing of cylindrical micelles. The adsorption of surfactants on the surface of carbon nanotubes allows a stable dispersion of carbon nanotubes encapsulated in the cylindrical micelles, resulting in the ordered structure. After photo-polymerization, the composite membranes display enhanced dye rejection. Both projects have shown promising ways to improve membrane filtration by using nanomaterials.
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Dai, Lin. "Electrocatalysis at Metal Nanomaterials." Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1343189565.
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Alharthi, Fahad Ahmed A. "New inorganic nanomaterials for low-voltage transistor applications." Thesis, University of Hull, 2016. http://hydra.hull.ac.uk/resources/hull:16517.
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This research aims to synthesise and characterise solution-processable high-k dielectric nanorods, which are potentially suitable for use as the dielectric layer in low-voltage Organic Field-Effect Transistor (OFET) applications. Oleic acid-stabilised titanium dioxide nanorods (TiO2-OA), metal-doped anatase titanium oxide (TiO2-OA-M; M=Nb, In, or Nb/In) nanorods, rutile titanium oxide nanorods (TiO2) and barium titanium oxide nanorods (BaTiO3) have been prepared and investigated. Solution processable oleic acid-stabilised titanium dioxide nanorods (TiO2-OA) have been prepared by hydrolysis of titanium (IV) tetraisopropoxide (TTIP) with oleic acid (OA) as surfactant in the presence of trimethylamine N-oxide (TMAO). Furthermore, a series of ligand exchange reactions were carried out to replace the oleic acid bonded on the surface of TiO2-OA with diethyl 2-phenylethyl phosphonate (DEPPNA), octadecylphosphonic acid (ODPA) or octylphosphonic acid (OPA). The ligand exchange rate was characterised by a combination of 31P liquid NMR, ICP, CHN, and FT-IR. The solubility of the ligand-exchanged products in chlorobenzene was also investigated. A novel method based on the co-hydrolysis of titanium (IV) tetraisopropoxide (TTIP) and niobium or/and indium isopropoxide or ethoxide has been investigated to prepare solution-processable, oleic acid- stabilised, niobium- and indium-doped, anatase TiO2 nanorods (TiO2-OA-M; M = Nb, In or Nb/In). The effect of niobium and indium precursors, the molar ratio of Nb or In precursors/TTIP and reaction time on the composition, structure and morphology of the Nb or In doped TiO2 products have been investigated by a combination of XPS, XRD, ICP, CHN, FT-IR and TEM. Furthermore, a series of ligand exchange reactions were carried out to replace the oleic acid, which is bonded on the surface of TiO2-OA-M, with diethyl 2-phenylethyl phosphonate (DEPPNA) or octadecylphosphonic acid (ODPA). The solubility of the products in chlorobenzene was also investigated. Rutile titanium dioxide nanorods with different sizes were prepared by three different approaches. In the first approach,hair-like rutile nanorods TiO2 were prepared by simple hydrolysis of a TiOCl2 solution at low temperature (50, 70 and 90 °C). In the second approach, rutile nanorods TiO2 with a length of 150-200 nm and a width of 25-40 nm were prepared by using a hydrothermal treatment of TiOCl2 at 220 °C. In the third approach, rutile nanorods TiO2 with length of 80 nm and diameter of 20 nm were prepared by using an hydrothermal reaction of TiOCl2 in the presence of 3-hydroxytyramine hydrogen chloride, [(HO)2C6H3CH2CH2NH2·HCl] at 150°C. In order to improve the solubility of the obtained rutile titanium dioxide nanorods in organic solvents, different surface-modification methods have been investigated to coat the surface of the rutile titanium dioxide nanorods with various organic ligands. In the first method, a modification of the TiO2 nanorods with oleic acid (OA) in chlorobenzene was investigated. In the second method, a two-stage treatment of TiO2 nanorods in an acidic medium was studied, using a selection of oleic acid (OA), diethyl 2-phenylethyl phosphonate (DEPPNA), octylphosphonic acid (OPA) and decylphosphonic acid (ODPA) as ligands. In the third method, wet TiO2 nanorods before dry was directly modified with a range of oleic acid and amines, e.g., octylamine, dodecylamine and hexadecylamine, as ligands. All the products were characterized by a combination of XRD, ICP, CHN, FT-IR and TEM. The preparation of barium titanium oxide nanorods (BaTiO3) has been investigated by different approaches. In the first approach, a hydrothermal reaction was carried out to convert the titanium dioxide nanorods prepared in the first and third parts in this research into BaTiO3 nanorods. The effect of the molar ratio of Ba/Ti, the reaction pH, reaction time and temperature on the composition, structure and morphology of the products were fully investigated. In the second approach, a hydrothermal reaction using a single source Ba/Ti precursor, i.e., barium titanium ethylhexano-isoproxide BaTi(O2CC7H15)(OC3H7)5, was carried out to prepare barium titanium oxide nanorods. In the third approach, barium titanium oxide nanorods were prepared by using a hydrothermal reaction between barium chloride (BaCl2) and titanium oxy chloride (TiOCl2) in the presence of ethylene glycol as surfactant. All the products have been characterised by a combination of XRD, ICP, CHN, FT-IR and TEM.
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Samarakoon, Duminda K. "Structural, electronic, and magnetic properties of graphene-based nanomaterials." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/708.
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The binding of radical groups such as hydrogen, hydroxyl, epoxide, or fluorine to the graphene surface, forms covalent bonds and transforms the trigonal sp2 orbital to the tetragonal sp3 orbital. Such a transformation drastically modifies electronic properties, which leads to the opening of a bandgap through the removal of the bands near the Fermi level of the pristine graphene. We have investigated the structural, electronic, magnetic, and vibrational properties of functionalized graphene based on first-principles densityfunctional calculations. A twist-boat conformation is identified as the energetically most favorable nonmetallic configuration for fully oxidized graphene. The calculated Raman G-band blue shift is in very good agreement with experimental observations. A detailed analysis of fluorographene membranes indicates that there exist prominent chair and stirrup conformations, which correlate with the experimentally observed in-plane lattice expansion contrary to a contraction in graphane. The optical response of fluorographene is investigated using the GW-Bethe-Salpeter equation approach. The results are in good conformity with the experimentally observed optical gap and reveal predominant chargetransfer excitations arising from strong electron-hole interactions. The appearance of bounded excitons in the ultraviolet region can result in an excitonic Bose-Einstein condensate in fluorographene. Hydrogenated epitaxial graphene has distinctive electronic properties compared to the two-sided hydrogenated graphene. The stability of a given hydrogenation pattern is strongly influenced by the amount of sp2-hybridized bonding in the structure. A trigonal planar networked hydrogenation pattern is identified as an intrinsic ferromagnetic semiconductor, which is in good conformity with experimental observations. The electronic structure of graphite and rotational-stacked multilayer epitaxial graphene as a function of the applied electric bias is investigated using dispersion-corrected density-functional theory. The tailoring of electronic band structure correlates with the interlayer coupling tuned by the applied bias. The implications of controllable electronic structure of rotationally fault-stacked epitaxial graphene grown on the C-face of SiC for future device applications are discussed. We have also investigated the electronic properties of fully hydrogenated boron-nitride (BN) layer and zigzag-edged nanoribbons using dispersion-corrected density-functional calculations. Among various low-energy hydrogenated membranes referred to as chair, boat, twist-boat, and stirrup, the stirrup conformation is the most energetically favorable one. The zigzag-edged BN nanoribbon, prominently fabricated in experiments, possesses intrinsic half-metallicity with full hydrogenation. The half-metallicity can be tuned by applying a transverse electric bias, thereby providing a promising route for spintronics device applications.
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Lu, Tian. "Nanomaterials For Liquid Chromatography and Laser Desorption/Ionization MassSpectrometry." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376981440.
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Lichtenberg, Stuart. "Nanomaterials for Double-Stranded RNA Delivery." UKnowledge, 2019. https://uknowledge.uky.edu/pss_etds/124.
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RNA interference has enormous potential as a potent, specific, and environmentally friendly alternative to small molecule pesticides for crop protection. The use of exogenous double-stranded RNA offers flexibility in targeting and use in crops in which transgenic manipulation is not an option. The combination of RNAi with nanotechnology offers further advantages that are not available with dsRNA alone. In this work, I have evaluated several different combinations of nanomaterials and polymers for use in RNAi-based pest control systems. First, I have characterized the use of chitosan/dsRNA polyplex nanoparticles for gene knockdown using the model nematode Caenorhabditis elegans. Though chitosan/dsRNA polyplexes are equally as effective as naked dsRNA for gene knockdown on a concentration basis, these materials are assimilated into cells in a manner independent of dsRNA specific transport proteins. The mechanism of uptake is likely clathrin-mediated endocytosis. In addition, I identify a significant and yet unreported side-effect associated with chitosan exposure, the dysregulation of a major myosin isoform. Next, I have determined the efficacy of chitosan/dsRNA polyplex nanoparticles under different environmental conditions. The presence of inorganic ions (phosphate and nitrate) at realistic environmental concentrations does not alter the efficacy of the nanoparticles for gene knockdown, nor do they inhibit knockdown by naked dsRNA. These conditions did not cause any significant changes to the hydrodynamic diameter or zeta potential of the particles themselves between treatments. By contrast, a pH higher than six and the presence of natural organic matter significantly reduce the efficacy of the nanomaterials at gene knockdown but leave knockdown by naked dsRNA unaffected. Though some changes in polyplex size are observed in the pH treatments, these changes are comparatively small, and particles remain well within the size that can be ingested by C. elegans. At pH 8, the charge of the particles is effectively neutral. Similarly, concentrations of natural organic matter >2.5 mg/L cause a charge reversal of the particles, from strongly cationic to strongly anionic. Large aggregates are also visible in each of these treatments. Lastly, I characterize the efficacy of a suite of different polymer and solid core nanomaterials for dsRNA delivery, similar to the above. Poly-L-lysine, poly-L-arginine, Ge-doped imogolite, and poly-L-arginine-citrate coated Au nanoparticles all fail to cause any appreciable knockdown in the same C. elegans reporter system. Uptake of the polymers was exceedingly poor, and though the Au particles appear to have been ingested, there is no evidence of significant gene knockdown. Furthermore, poly-L-arginine caused significant injury to the mouthparts of C. elegans exposed to these materials. Layered double-hydroxide nanoparticles were successful at gene knockdown, and appear to function slightly better than naked dsRNA alone, and were translocated in C. elegans in a similar fashion to naked dsRNA. Taken together, these findings aid in the development of safe and effective RNAi biological control agents.
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Tripathy, Jagnyaseni. "Template-Assisted Fabrication of Ferromagnetic Nanomaterials." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1951.
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Abstract
Template assisted deposition was used to produce various nanomaterials including simple nanowires, nanorods, multi-segmented metal nanowires, core-shell nanowires, alloy and polymer wires and tubes. Anodized aluminum oxide (AAO) membranes were used as templates for the growth of the various structures using an electrochemical deposition method and also by wetting the porous templates. In the electrochemical deposition method, the pore size of the templates affects the rate of synthesis and the structures of the nanomaterials while in the wetting method, the viscosity and reaction time in the polymer solution influence the structures of the nanomaterials.
A conventional two-step anodization procedure was used to synthesize thick AAO templates with porous hexagonal channels at a constant applied voltage and temperature. A maximum thickness of over 180 µm oxide layer could be fabricated using mild anodization at 60 V and 80 V. Compared to conventional mild anodization, these conditions facilitated faster growth of oxide layers with regular pore arrangement.
Polyethylene glycol (PEG) containing ferromagnetic nanowires were synthesized using template assisted electrochemical deposition method. During the synthesis, simultaneous deposition of polymer and metal ions resulted nanowires coated with a uniform layer of PEG without interfering with the structure and magnetic properties of the nanowires.
PEG-coated Ni nanowires were embedded in polyethylene diacrylate (PEGDA) matrix after the removal of the AAO templates. Comparison of results with and without a magnetic field during embedding showed that the presence of magnetic field supported embedding of nanowire arrays in polymer.
Influence of using AAO templates with several pore diameters for the synthesis of bimetallic nanowires were studied by growing Ni-Fe and Ni-Co bi-metallic nanowires. At a constant applied current by using templates with a pore diameters of 60 nm alloy formed while with a pore diameter of 130 nm core-shell nanowires formed.
Polyvinylidene fluoride (PVDF) films and nanotubes were synthesized using a solution recrystallization method that favored the formation of piezoelectric β phase thin films. Variation in the concentration of polymer in the mixture solution allowed synthesis of different types of structures such as PVDF composites, nanorods and nanocrystals with tunable morphologies.
Keywords: One-dimensional structures, electrodeposition, porous alumina, ferromagnetic nanostructures, magnetic core-shell nanowires, alloys, polymer composite, stimuli-active, PEGDA, azobenzene, and PVDF.
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Shieh, Aileen. "Self-assembled Nanomaterials for Chemotherapeutic Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480594149120089.
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King, Martin O. "Spectroscopy and microscopy of transition metal chalcogenide nanomaterials." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4506/.
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This thesis details the physical and electronic structure of several technologically important transition metal chalcogenides (TMCs) using a combination of transmission electron microscopy (TEM) and surface science experimental techniques. The materials studied include CuxTe and CdTe, which find application in high efficiency, low weight photovoltaic devices. CuxTe alloys are frequently used as an electrical back contact in high efficiency CdTe photovoltaics. Here, we examine the alloying of Te on the Cu(111), polycrystalline Cu and Cu(643) surfaces. Chapter 3 of this thesis shows that the alloying of Te and Cu(111) is facile at room temperature, contrary to previous reports. Two distinct surface phases exist, depending on Te surface concentration. Below a coverage of 0.33 monolayers (MLs) of Te a surface substitutional alloy (SSA) is found to exist, where a Te adatom substituted for a surface Cu atom. For Te coverages greater than 0.66 ML, an unusual Cu3Te2 alloy continually grows on the surface, stabilised by a good lattice match to the Cu(111) substrate. The surface alloying of the Cu-Te system displays an intriguing dependence on the surface termination of the Cu substrate. Of the three Cu substrates studied here, Cu(111), Cu(643)R and polycrystalline Cu, a 1 ML film of Te gave ordered alloy structures with stoichiometries of Cu3Te2, CuTe and Cu2Te, respectively. In chapter 4, the study of thin film photovoltaics is extended to the deposition of CdTe onto Cu and CuxTe substrates. CdTe is observed to grow three dimensionally on Cu(111), Cu3Te2 and Cu2Te. Cu+ diffusion, crucial for photovoltaic performance, is detected for CdTe thicknesses greater than 2 ML and is assigned, predominately, to Cu2Te crystallites forming within the CdTe layer, with a minor amount of Cu residing in interstitial sites in the host CdTe structure. Chapter 5 describes the alloying of Te with a intrinsically chiral surface, Cu(643)R, the first study of its kind. The results of this study reveal that step mediated alloying occurs between Cu and Te with significant faceting of the surface. Two ordered CuTe alloy phases were observed for sub-monolayer Te coverages. The low coverage alloy exists for Te coverages between 0.18 ML and 0.45 ML and has a chiral unit cell. The high coverage alloy exists for Te coverages between 0.45 ML and 1.5 ML and has an achiral unit cell. The atomic positions of these surface alloys are tentatively interpreted from the scanning tunnelling microscopy (STM) images. In contrast to the thin film experiments in chapters 3-5, chapter 6 describes a study of TaS3 nanoribbons. These studies reveal that the nanoribbons have a distinct core-shell type structure. Characterisation with surface science techniques shows that the shell is nonstoichiometric and amorphous while TEM shows a crystalline core to the material. Interestingly, the TaS3 are observed to be unstable when interfaced on a Au substrate, with the shell persistently losing S to the substrate, which have potential implications in device integration.
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Kraft, Marco. "Spectroscopic characterization of upconversion nanomaterials with systematically varied material composition and surface chemistry." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19657.
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Ziel dieser Doktorarbeit war es, den Einfluss von verschiedenen Parametern auf die spektroskopischen Eigenschaften von Lanthanid-basierten Aufkonversions-Materialien zu erforschen. Ein besonderer Fokus lag dabei auf hexagonalen Natrium-Yttrium-Tetrafluorid Kristallen, die mit dreifachgeladenen Yb und Er oder Tm Ionen kodotiert wurden. Eine wesentliche Voraussetzung für mögliche Anwendungen dieser Kristalle ist ein Verständnis aller ihrer wichtigen photophysikalischen Besonderheiten.
Die erste Studie dieser Doktorarbeit untersuchte daher, wieso Nanokristalle viel weniger absorbierte in ausgesendete Photonen umwandeln als mikrokristalline Teilchen. Die Ergebnisse zeigten, dass man ungeschalte Kristalle aufgrund von Oberflächen-Lösch-Effekten in zwei Teile unterteilen kann, einen strahlenden Kern und eine Schale aus stark oder vollständig gelöschten oberflächennahen Lanthanid-Ionen, welche für Kristalle abnehmender Größe einen immer größeren Volumenanteil einnimmt. Die zweite Studie untersuchte exemplarisch, ob eine kompliziertere Partikelarchitektur, bestehend aus einem einfach-dotierten Er Kern und Yb als Schalenmaterial, diesen Effizienzverlust der Lumineszenz reduzieren kann. Die Ergebnisse zeigten jedoch, dass dies nicht der Fall ist. Eine weitere Studie untersuchte den Einfluss der Konzentration der Tm Ionen in Yb, Tm kodotierten Nanokristallen auf die spektroskopischen Eigenschaften dieser Materialien und zeigte, dass für eine maximale Emission im Lichtwellenbereich über 700 nm andere Tm Konzentrationen benötigt werden als für maximale Lichtemissionen in den unteren Lichtwellenbereichen. Die letzte Studie untersuchte den Einfluss eines zuvor berichteten Zersetzungsprozesses von exemplarisch ausgewählten Yb, Tm kodotierte Nanokristallen in wässrigen Dispersionen auf deren spektroskopische Eigenschaften. Mithilfe dieser Ergebnisse war es möglich, mehrere Emissionsbanden als Parameter für das Langzeit-Stabilitäts-Monitoring dieser Materialien zu identifizieren.This PhD thesis investigated the influence of various parameters on the spectroscopic properties of so-called upconversion nanoparticles (UCNPs). A special emphasis was dedicated to hexagonal-phase sodium yttrium tetrafluoride crystals that were codoped with trivalent Yb and either Er or Tm ions. Such UCNPs can, however, experience no breakthrough in the field of UC nanotechnology before all of their important photophysical features are understood. The first study of this PhD thesis therefore investigated, why nanocrystalline upconverters with different surface chemistries convert less absorbed to emitted photons than their microcrystalline counterparts. The results revealed that upconverting crystals apparently have to be subdivided into two parts, with one being the luminescent core and the other being a completely dark shell that is quenched by surface effects and assumes an ever increasing volumetric content for small UCNPs. The second study exemplarily investigated, if a more complex particle nanostructure that consisted of a Er doped core, surrounded by a Yb doped shell, could overcome these efficiency losses, however, it concluded that it does not. Another study explored the influence of Tm doping concentrations of Yb, Tm codoped nanocrystals on their spectroscopic properties and concluded that different Tm doping concentrations are required for a maximum upconversion luminescence in the wavelength regions above 700 nm, than for the wavelength regions below that. The last study of this PhD thesis investigated the influence of a previously reported dissolution process of UCNPs in aqueous solutions on the spectroscopic properties of exemplarily chosen Yb, Tm codoped nanocrystals. These results were then utilized to identify several upconversion emission bands that can be used as a screening parameter for the long-term stability monitoring of UCNPs.
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Becerril-Garcia, Hector Alejandro. "DNA-Templated Nanomaterials." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1823.pdf.
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Newsome, Toni Elwell. "Development of Electrospun Nanomaterials and Their Applications in Separation Science." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1394798760.
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Mueller, Paul S. "Synthesis of silica based porous nanomaterials." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1368.
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Silica is one of the most abundant elements on the planet, has flexible bonding properties and generally excellent stability. Because of these properties, silica has been a vital component in technologies ranging from ancient glassware to modern supercomputers. Silica is able to form a wide range of materials both alone and as a component of larger material frameworks. Porous silica based nanomaterials are rapidly growing in importance because of their many applications in a wide variety of fields. This thesis focuses on the synthesis of silica based porous nanomaterials: nanocrystalline zeolites, mesoporous silica nanoparticles, and iron oxide core/shell nanocomposites. The synthetic conditions of these materials were varied in order to maximize efficiency, minimize environmental impact, and produce high quality material with far reaching potential applications. The materials were characterized by physicochemical techniques including Transmission Electron Microscopy, Dynamic Light Scattering, Powder X-Ray Diffraction, Solid State NMR, and Nitrogen Adsorption Isotherms. The materials were evaluated and conditions were controlled to produce high yields of quality nanomaterials and hypothesize methods for further synthetic control. The products will be used in studies involving nanoparticle toxicity, environmental remediation, and drug delivery.
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Tsui, Hei Man. "Synthesis and Characterization of Magnetic Cabides and Oxides Nanomaterials." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5366.
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The design and development of nanoparticles is of great interest in the current energy and electronic industry. However, based on the current materials available the production cost can be high with insignificant magnetic and mechanical properties. Specifically, rare-earth magnetic materials composed of neodymium and samarium are known for their high magnetic performance, however, due to the cost of development there is a need to develop a versatile and cost effective material. Alternatively, cobalt carbide nanomaterials have shown to be a promising alternative for rare-earth free magnets as they exhibit comparable properties as hexaferrite magnetic materials. The primary goal of this dissertation focuses on the development of nanoparticles for permeant magnetic, and magnetic refrigeration applications. The first part of this work focuses on the synthesis of cobalt carbide (CoxC, x=2,3) nanoparticles using a novel polyol synthesis method by introducing a small amount of Ru, Cu, or Au as nucleating agent. It was found that the morphology and magnetic properties of the as-synthesized CoxC nanoparticles change as a result of directional growth of nanoparticles using nucleating agents. Needle-like particle morphology ranges from 20-50 nm in width and as long as 1 µm in length were synthesized using Ru as nucleating agent. These particles exhibit magnetization saturation of 33.5 emu/g with a coercivity of 2870 Oe and a maximum energy product 1.92 MGOe (BHmax) observed. Particle morphology is a critical aspect in the development of magnetic nanoparticles as anisotropic particles have shown increased coercivity and magnetic properties. These CoxC nanomaterials have a higher maximum energy product compared to previous work providing further insight into the development of non-rare earth magnetic material.
The second part of this dissertation work focuses on the sol-gel synthesis of perovskite LaCaMnO3 (LCMO) nanomaterials. In this process, various chain lengths of polyethylene glycol (PEG) was added into a solution consisting of La, Ca, and Mn salts. The solution was left for the gelation process, and high temperature sintering to obtain the final product. By varying the polymer chain of the PEG, the size of the as synthesized LaCaMnO3 nanomaterials were altered. The as-synthesized LCMO nanomaterials have shown a maximum change in magnetic entropy (-ΔSM) was found to be 19.3 Jkg-1K-1 at 278 K for a field change of 0-3 T and 8.7 Jkg-1K-1 for a field change of 0-1 T. This is a significant improvement in comparison to current literature of the material suggesting that this is a promising alternative to Gd materials that is prone to oxidation. With additional development, LCMO or related maganites could lead to application in commercial technologies.
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Shrestha, Khadga M. "Modifying nanoparticle shape by choice of synthetic method: nanorods, spheres, mutipods, and gels." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14898.
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Doctor of PhilosophyDepartment of Chemistry
Kenneth J. Klabunde
A series of nanoparticle synthesis methods were devised with the aim of controlling shape. CuO nanorods were synthesized by a hydrothermal treatment with different chemical combinations. Physical parameters: concentration, temperature, and aging time greatly affected the size, morphology and the composition of nanorods. These CuO nanomaterials were reduced to metallic copper at elevated temperature by 4% H[subscript]2 diluted in helium while preserving the morphology. The CuO and Cu nanomaterials were employed for near infra-red (NIR) diffuse reflectance. Among them, CuO nanorods were found to be the best NIR diffuse reflectors, indicating potential application as NIR obscurants. Cu[subscript]2O and its composite samples with different morphologies, some with unique morphologies, were synthesized by reducing Cu[superscript]2[superscript]+ precursors without using any surfactant. The effects of change of Cu-precursors, reducing agents, and other physical conditions such as temperature and pressure were investigated. Since Cu[subscript]2O is a semiconductor (E[subscript]g ~ 2.1 eV), these samples were used as photocatalyst for the degradation of methyl violet B solution under UV-vis light and as dark catalysts for decomposition of H[subscript]2O[subscript]2 to investigate the effect of morphology. The photocatalytic activity was found to be morphology dependent and the dark catalytic activity was found to be dependent on both surface area and morphology. Mixed oxides of MgO and TiO[subscript]2 with different ratios, and pure TiO[subscript]2 were synthesized by two methods—flame synthesis and aerogel. These mixed oxides were employed as photo-catalysts under UV-vis light to oxidize acetaldehyde. The mixed oxides with low content of MgO (~ 2 mole %) were found to be more UV active photo-catalysts for the degradation of acetaldehyde than the degradation by TiO[subscript]2. The mixed oxides prepared by the aerogel method were found to be superior photo-catalysts than the mixed oxides of equal ratio prepared by flame synthesis. Silica aerosol gels were prepared by two methods: detonation and flame synthesis. Hexamethyldisiloxane (HMDSO) was used as a precursor during the detonation at different conditions. Interestingly, spherical silica nanoparticles were found to be formed by the detonation. Relatively smaller silica nanoparticles with larger volume fraction were found to be favorable for the formation of silica aerosol gels. During the flame synthesis, the silicon precursors, dimethoxydimethylsilane (DMDMS) and HMDSO, were used. Different shapes—spherical, oval, and non-spherical—and sizes of silica particles were formed. These silica nanomaterials were almost amorphous, and they might have many potential applications.
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He, Jie. "Plasmonic Nanomaterials for Biosensing, Optimizations and Applications." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522336210516443.
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Shukr, Delan. "Carbon nanomaterials as electrical conductors in electrodes." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85056.
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In this project, different molecules have been investigated with the purpose of creating anohmic contact between metals and carbon nano materials. In particular, we considered simplemolecules connecting a graphene layer and a copper-slab. In order to determine the capability of such systems, the electronic structure was computedusing Density Functional Theory (DFT). Structural relaxation was performed in order to findcandidates where the metal and the graphene binds chemically with the hypothesis that thehybridization of the states will induce more states at the Fermi level. Six different molecularchains were tested and three of them were found to chemisorb to the graphene sheet and thecopper surface simultaneously. The electronic properties for these systems were then furtherinvestigated using the density of states (DOS). An overlap density of states (ODOS) wasdefined in order to evaluate the respective contribution of the graphene, metal and molecule. From the DOS analysis, we report that these systems did not form ohmic contacts as the resultshows too few states close to the Fermi level. The most interesting case was using a hexanolchain which had some partially overlapping states seen from the ODOS of the graphenemoleculeand graphene-Cu at the Fermi level. However, these were only small contributions.Further research is crucial in order to find a more suitable molecular chain between thegraphene and the copper for an ohmic contact.
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Hinde, Christopher. "Design of hybrid nanomaterials as sustainable heterogeneous oxidation catalysts." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/380904/.
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Anion exchange properties of a microporous copper chlorophosphate have been exploited to demonstrate, for the first time, a method for generating monodisperse and uncapped noble metal nanoparticles by thermal extrusion. Confirmed initially by structural characterisation with PXRD, SEM and TEM studies, the microporous framework supported Au, Pt and Pd nanoparticles were shown to activate molecular oxygen for the environmentally benign oxidation of benzyl alcohol to benzaldehyde. Probing of the kinetic properties demonstrated contrasting catalytic features for each of the NP catalysts, with the Pt NP catalyst showing heightened activity and a propensity for selectivity toward benzaldehyde. In-depth physico-chemical analysis of the metal NP catalysts revealed a dependence of the activation/extrusion parameters to the activity and catalytic properties of the resulting materials. Utilising X-ray techniques such as XAS (EXAFS and XANES) and XPS, coupled with the investigation of catalytic properties toward aerobic oxidation of vanillyl alcohol to vanillin, it was established that reduction in the presence of H2 at moderate temperatures is a much more efficient process to calcination in air at much higher temperatures, to afford the complete extrusion of complex anions for active NP formation. Structure-property correlations were harnessed to rationalise the superior catalytic properties of the Pt catalyst compared with the Au and Pd counterparts, exposing the extent of extrusion and revealing a contrast in the nature of complex anion-support interactions. To further exemplify the scope of hybrid metal nanoparticle/microporous nanomaterials in the pursuit of new, efficient, green and industrially applicable catalysts, the highly robust UiO-66 type MOFs have been utilised as NP hosts for tandem catalytic applications. A facile method of NP deposition on UiO-66 has been demonstrated using established colloidal synthesis methods with PVP, to generate active Au NP materials for the selective oxidation of cinnamyl alcohol to cinnamaldehyde using simple peroxides. By introducing amine functionality to the MOF with 2-aminoterephthalic acid to form the isoreticular NH2-UiO-66 as a host for Au NPs, an effective catalyst for the two step process involving the aforementioned oxidation with subsequent Knoevenagel condensation reaction (coupling the aldehyde with an activated methylene compound at the –NH2 sites on the MOF) has been achieved in good yield.
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Navarreto, Lugo Monica. "CHEMICAL DESIGN OF FUNCTIONALIZED NANOMATERIALS FOR SENSING AND BACTERIAL TREATMENT APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1553701749029872.
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Baghdadi, Neazar Eassam. "Design and synthesis of iron oxide nanomaterials for biomedical applications." Thesis, University of Hull, 2016. http://hydra.hull.ac.uk/resources/hull:14799.
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Nanotechnology products have huge potential to be a part of the developments in various fields, including functional materials, electronics and medicine. Using nanomaterials in medical applications has been successful for disease diagnosis and drug delivery systems. One of the safest and most versatile nanomaterials utilized for medical purposes are iron oxide nanomaterials. This thesis presents the synthesis, coating and targeting vector modification of iron oxide materials for several biomedical applications including multimodal imaging and cancer cell targeting. Iron oxide nanorods (NRDs) were produced and coated with silica shells as well as other surface modifying molecules including azamacrocycles (DO3A) and polyethylene glycol chains (PEG) which were attached in a one pot reaction. The presence of PEG on the NRDs surface gave improved suspension stability over a wide range of salt concentrations and pH values. Radiolabelling of the NRDs was demonstrated with the positron emitting radioisotope ⁶⁸Ga. The use of nanorods as magnetic resonance imaging (MRI) contrast agents gave a two-fold increase in T2 relaxivity (180 s⁻¹) compared to previous work using spherical nanoparticles. The ⁶⁸Ga labelled NRD constructs show high radiochemical stability against transferrin challenge over a 3 h incubation period. An in vivo bio-distribution study was carried out by intravenously injecting a CD1 nude female mice with 2 mg of (NRDs-PEG), then multimodal imaging analysis was performed using MRI and positron emission tomography (PET) imaging. The NRDs with sizes between 100 to 200 nm showed rapid accumulation in the liver after 5 min due to uptake by macrophages and Kupffer cells as part of reticuloendothelial system, and a small quantity accumulated in the lung and spleen. It was also observed that in the MRI T2 weighted image, the liver is significantly darker than the T1 weighted imaging which confirms the sample accumulation. The multimodal images proved that the radiolabelled NRDs were stable in vivo on the timescale of the imaging study. Iron oxide nanoparticles (IONPs) were functionalised for targeting cancer cells. The IONPs were conjugated to a chemokine receptor targeting vector and the targeting properties were tested in vitro using Jurkat cancer cells with flow cytometry in an antibody competition assay. The NPs showed 100% inhibition of the anti-CXCR4 antibody binding in this assay.