Surfactant templating provides for the synthesis of ordered mesoporous silica and the opportunity to tailor the pore size, pore structure, particle morphology and surface functionality of the silica through the selection of synthesis conditions and surfactant template. This work extends the synthesis of nanostructured silica using fluorinated surfactant templates to the synthesis of organic/inorganic composites. The effect of fluorinated surfactant templates (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and C10F21C2H4NC5H5Cl), which have highly hydrophobic fluorocarbon tails, on functional group incorporation, accessibility, and silica textural properties is examined and compared to properties of hydrocarbon surfactant (C16H33N(CH3)3Br, CTAB) templated silica. Hydrocarbon (vinyl, n-decyl and 3-aminopropyl) and fluorocarbon (perfluoro-octyl, perfluorodecyl) functional group incorporation by direct synthesis is demonstrated, and its effects on silica properties are interpreted based on the aggregation behavior with the surfactant templates. Silica materials synthesized with CTAB possess greater pore order than materials synthesized with the fluorocarbon surfactants. The incorporation of the short vinyl chain substantially reduces silica pore size and pore order. However, pore order increases with functionalization for materials synthesized with the fluorinated surfactant having the longest hydrophobic chain. The incorporation of longer chain functional groups (n-decyl, perfluorodecyl, perfluoro-octyl) by direct synthesis results in hexagonal pore structured silica for combinations of hydrocarbon/fluorocarbon surfactant and functional groups. The long chain of these silica precursors, which can be incorporated in the surfactant micelle core, affect the pore size less than vinyl incorporation. Synthesis using the longer chain fluoro-surfactant (C8F17C2H4NC5H5Cl) template in ethanol/water solution results in highest incorporation of both n-decyl and the fluorocarbon functional groups, with a corresponding loss of material order in the fluorinated material. Matching the fluorocarbon surfactant (C6F13C2H4NC5H5Cl) to the perfluoro-octyl precursor did not show improved functional group incorporation. Higher incorporation of the perfluoro-octyl functional group was observed for all surfactant templates, but the perfluoro-decyl silica is a better adsorbent for the separation of hydrocarbon and fluorocarbon tagged anthraquinones. Incorporating a reactive hydrophilic functional group (3-aminopropyl) suggests further applications of the resulting nanoporous silica. Greater amine incorporation is achieved in the CTAB templated silica, which has hexagonal pore structure; the order and surface area decreases for the fluorinated surfactant templated material.

The structure of nanoporous gold (np-Au) provides a very limited volume for deformation to occur, and thus offers an opportunity to study the role of defects such as dislocations in nanoscale metal volumes. A practical goal is to understand mechanical properties of np-Au so that it can be can produced in stable form, for use in applications that require some mechanical integrity. Bulk and thin film np-Au have been fabricated and studied here. Bulk np-Au was prepared by electrochemically dealloying Au-Ag alloys with 25 and 30 at.% Au. In the lower Au content material, cracks always formed during dealloying. When Au content increased to 30 at.% and a two-step electrochemical dealloying method was used (first using diluted electrolyte and then concentrated acid), bulk np-Au with no volume change and minimal cracking was successfully fabricated. Thermal and mechanical behavior of np-Au was studied by heat treatment and microindentation. During annealing in air, Ostwald ripening governed ligament coarsening, while annealing of ligaments in vacuum was more likely a sintering process. Nanoporous Au thin films were produced by dealloying sputtered Au-Ag alloy films. Residual stresses in np-Au films were measured with wafer curvature. Similar to bulk materials, np-Au thin films made from 25 at.% Au alloy films exhibited extensive cracking during dealloying, whereas films from 30 at.% Au precursor alloys were completely crack-free. 25 at.% Au np-Au films carried almost no stress because of extensive cracking, whereas stress in 30 at.% Au np-Au films was up to ~230 MPa. Ligament coarsening followed a t1/8 time dependence for stress-free films, versus t1/4 in films under stress. It was proposed that bulk diffusion was responsible for formation of larger pits at grain centers during the incipient stages of dealloying. In situ nanoindentation experiments inside the transmission electron microscope were performed to investigate deformation of np-Au films and dislocation motion within ligaments. Dislocations were generated easily and moved along ligament axes, after which they interacted with other dislocations in the nodes of the porous network. It was found that slower displacement rates caused load drops to occur at shorter distance intervals and longer time intervals.

FABRICATION OF NANOPOROUS GOLD AND BIOLOGICAL APPLICATIONS By Badharinadh Uppalapati A Dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2014 Major Director: Maryanne M. Collinson, Professor, Department of Chemistry Fabrication of nanoporous gold electrodes by dealloying Au:Ag alloys has attracted much attention in sensing applications. In the first part of this work, the electrochemical response of the redox active molecule, potassium ferricyanide, in a solution of bovine serum albumin in buffer, serum or blood was studied using nanoporous gold and comparisons made to planar gold. Nanoporous gold electrodes with different surface areas and porosity were prepared by dealloying Au:Ag alloy in nitric acid for different dealloying times, specifically, 7.5, 10, 12.5, 20 minutes. Characterization was done using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Using cyclic voltammetry, planar gold electrodes exposed to bovine serum albumin in buffer showed a decrease in Faradaic peak current and an increase in peak splitting for potassium ferricyanide. The time required for the peak Faradaic current to drop to one-half of its original value was 3 minutes. At nanoporous gold electrodes, however, no significant reduction in Faradaic peak current or increase in peak splitting was observed. Nanoporous gold electrodes having the smallest pore size and largest surface area showed ideal results to biofouling. These electrodes are believed to impede the mass transport of large biomolecules while allowing small redox molecules to exchange electrons effectively with the electrode. In the second part of this work, the open circuit potential (OCP) of biologic solutions (e.g., blood) was measured using nanoporous gold electrodes. Historically, the measurement of blood redox potential has been hindered due to significant fouling and surface passivation of the metal electrodes. As nanoporous gold electrodes retained electrochemical activity of redox probes like potassium ferricyanide in human serum and rabbit blood, they were used to measure the OCP of blood and plasma from various animals like pig, rabbit, rat, monkey and humans. Comparisons were made to planar gold electrodes. The OCP values at both the planar gold and nanoporous gold electrodes were different from each other and there was variability due to different constituents present in blood and plasma. The OCP of rabbit blood and crashed rabbit blood was measured and the values were found to be different from each other indicating that ORP helps in measuring the animal condition. Ascorbic acid was added to rabbit and sheep blood and OCP measured at the nanoporous electrodes. Addition of reducing agent to blood at different intervals and different concentrations showed a change in potential with concentration.

Nous avons développé de nouveaux systèmes polymères nanoporeux et fonctionnalisés en vue de leur utilisation comme nanoréacteurs. Deux approches complémentaires ont été envisagées pour la génération des précurseurs nanostructurés des matériaux mésoporeux. La première stratégie repose sur la synthèse de copolymères diblocs poly(D,L-lactide)-bloc-polystyrène (PLA-b-PS) semi-hydrolysable possédant une fonction réactive au point de jonction entre les deux bloc (SO3H) ; la deuxième voie est fondée sur la préparation de réseaux interpénétrés de polymères dont l'un des sous-réseaux est stable et fonctionnalisé (PS) et l'autre est hydrolysable (PLA). L'obtention de la porosité dans ces systèmes organisés a résulté de l'hydrolyse sélective et quantitative des domaines de la phase dégradable. La caractérisation des différents systèmes a été effectuée au moyen de diverses techniques d'analyse fine, telles que des techniques spectroscopiques, la microscopie électronique à balayage, la thermoporométrie par DSC et l'adsorption-désorption d'azote. Ces études physico-chimiques ont permis d'accéder à l'organisation de la porosité et de la chimie de surface, ainsi qu'aux propriétés spécifiques des matériaux nanoporeux. La dernière partie a traité de l'étude des applications potentielles de ces matrices poreuses fonctionnalisées comme nanoréacteurs dans le domaine de la catalyse d'une part, et dans la purification de l'acide phosphorique tunisien, d'autre part / Novel functionalized nanoporous polymer systems have been developed in order to be used as nanoreactors. Two complementary approaches have been envisioned for the generation of the nanostructured precursors of mesoporous materials. The first approach relies on the synthesis of semi-hydrolysable poly(D,L-lactide)-block-polystyrene (PLA-b-PS) diblock copolymers with a functional group (e.g. sulfonic acid) at the junction point between the two blocks, while the second strategy involves the preparation of interpenetrating polymer networks based on a functionalized stable sub-network (PS) and a hydrolyzable one (PLA). The generation of porosity in such organized systems results from the selective and quantitative hydrolysis of domains from the degradable phase. The characterization of different systems has been realized by means of miscellaneous analytical techniques, including spectroscopic techniques, scanning electron microscopy, DSC-based thermoporometry, and nitrogen sorption measurements. Such physico-chemical investigations permitted to get access to the organization of porosity and surface chemistry, as well as the specific properties of nanoporous materials. Lastly, we have investigated the potential applications of these functionalized porous matrices as nanoreactors in the area of catalysis as well as in the purification of Tunisian phosphoric acid

Le contrôle de la polarisation et de l’aimantation par le biais de champs magnétiques et électriques respectifs font des systèmes magnétoélectriques des candidats prometteurs à de nombreuses applications, parmi lesquelles les dispositifs micro-ondes, les dispositifs de stockage de données à haute densité, etc. L’élaboration d’hétérostructures toujours plus innovantes reste un défi majeur dans le but d’optimiser les densités d’interfaces entre les phases ferroélectriques et ferromagnétiques,et ainsi promouvoir les interactions de couplage mécaniques. Au cours de ce projet de thèse, deux stratégies sont mises en oeuvre pour la conception des matériaux : i) une structure coeur-écorce de type (1-1) composée de nanofils ferromagnétiques (1) dans des nanotubes ferroélectriques (1) àl’intérieur d’une membrane nanoporeuse tridimensionnelle auto supportée etii) une structure en couche mince de type (1-3) constituée de nanofils ferromagnétiques (1) supportés sur un substrat rigide et encapsulés dans une matrice ferroélectrique (3). / Controlling polarization or magnetization by an applied magneticand electric field respectively make magnetoelectric systems promisingcandidates for applications in microwave devices, high density data storagedevices, etc. Designing innovative magnetoelectric heterostructures is thus achallenge to optimize interface density between both ferroelectric andferromagnetic phases, and promote mechanical coupling interactions. In thisthesis project, two strategies are followed for material design: i) 1-1 coreshellstructure with ferromagnetic nanowires (1) inside ferroelectricnanotubes in a self-supported tridimensionnal porous template (1) and ii) 1-3structure where ferromagnetic nanowires (1) are supported on a substrateand embedded in a ferroelectric matrix (3).

Hydrogen storage is a developing technology that can be used as an energy vector for sustainable energy applications such as fuel cells for transport applications or for supplying power to the grid in moments of high demand. However, before hydrogen can be used as a practical energy vector, hydrogen storage issues, such as low gravimetric storage density, need to be addressed. One possible solution could be using nanoporous materials to physically adsorb hydrogen at low temperatures and moderate pressures. Hydrogen adsorption excess isotherms in solid-state porous materials can be obtained experimentally. However, the total amount stored in them, a quantity of more practical interest, cannot be measured by experimental techniques. Therefore, a model developed at the University of Bath is used to predict the total amount of hydrogen contained in nanoporous materials from their experimentally derived excess isotherm data. According to inelastic neutron scattering experiments (TOSCA, ISIS, RAL, Oxfordshire), solid-like hydrogen is likely to exist within the pores. The model is applied in this work in order to search for relationships between intrinsic properties of the materials (BET surface area, pore volume and pore size) and the predicted total hydrogen capacity of the materials. The model assumes adsorbed hydrogen at a constant density within the pore (defined as the absolute), also taking bulk hydrogen in the pore (amount that is not considered to be adsorbed by the adsorbent), into account. Several MOF datasets have been used to search for these relations, since they are the materials that have the highest hydrogen uptake in solid-state adsorption. Different MOFs and MOF families have been tested in order to widen the range of the correlations. Also, different strategies, such as fixing the pore volume when applying the fittings, relying on experimental data, or using high pressure hydrogen isotherm data to increase the robustness of the model have been researched. These MOFs have been either synthesized and characterized at the University of Bath or their datasets obtained from literature. Some of these MOFs with zeolitic structure exhibited unreported flexibility, being their structures further characterized. Changes on accessible pore size for hydrogen storage were also investigated using C60 in IRMOF-1. The final aim of this work is to find possible correlations between BET surface area, pore volume and pore size to find out what the values of these parameters have to be in a specific material to fulfil the DOE hydrogen storage requirements.

La tuberculose tue environ 2 millions de personnes chaque année, principalement à cause d’un diagnostic tardif ou inefficace ou de soins trop tardifs. Les techniques de diagnostic les plus efficaces sont souvent coûteuses et complexes à mettre en oeuvre dans les pays en voie de développement, régions de plus forte incidence de la maladie. L’objectif de ce projet est l’élaboration de capteurs luminescents à base de matériaux nanoporeux élaborés par procédé Sol-Gel pour détecter un métabolite très spécifique de Mycobacterium tuberculosis, l’acide nicotinique (AN), présent dans l’haleine des malades à des concentrations de quelques dizaines à quelques centaines de ppq, et de le discriminer vis-à-vis d’autres métabolites.Un complexe de nitrate de terbium (III) a été choisi comme molécule-sonde car la luminescence du terbium (III) peut être exaltée en présence de certains ligands organiques, notamment l’acide nicotinique. Une première étape a consisté à déterminer en solution les conditions de pH les plus favorables à la formation de complexes luminescent Tb(III)/AN. Ainsi l’établissement d’un pH de 6,4 dans un milieu tampon à base d’hexamine permet d’optimiser la formation du complexe Tb(III)/AN et le transfert d’énergie du ligand vers le cation. Le dosage de l’acide nicotinique est possible dans ces conditions dans une gamme de concentration de 400 nmol.L-1 à 100 μmol.L-1, soit de 7,2 ppb à 1,8 ppm.La seconde étape a consisté à produire des matrices nanoporeuses à base d’alcoxydes de silicium en vue d’obtenir des matrices à pH intrapore similaire ou proche de 6,4. Les variations de pH intrapore des matrices lors du piégeage de vapeur d’eau et/ou de dioxyde de carbone, deux interférents présents à des concentrations élevées dans l’haleine, ont été étudiées au moyen d’un colorant sensible au pH, le bleu de bromothymol. Les matrices ont été élaborées à partir de deux précurseurs de silice, dont un possédant une chaîne aminopropyle lui conférant un caractère basique. L’exposition des matrices à de la vapeur d’eau jusqu’à saturation a montré que le pH intrapore des matrices contenant 3% du précurseur aminé varie entre 6,5 et 6, gamme de pH optimisée pour la formation du complexe Tb(III)/AN.Dans la dernière étape, des matrices à 3% de précurseur aminé, dopés de terbium et tamponnées à pH 6,4 avec de l’hexamine ont été élaborées. Des mesures de luminescence de matrices exposées de manière statique à des vapeurs d’acide nicotinique pur ou provenant d’une solution aqueuse saturée ont montré une augmentation de la luminescence des matrices, preuve d’un piégeage effectif de l’acide nicotinique et de la formation in situ de complexes luminescents Tb(III)/AN. Malgré la présence d’eau qui désactive partiellement l’état excité de Tb3+, le piégeage de l’acide nicotinique et la formation de complexes Tb(III)/NA dans ces matrices demeure efficace. .Les études d’interférence ont permis de montrer que la présence de marqueurs secondaires, comme le nicotinate de méthyle, affecte la luminescence des complexes Tb(III)/AN uniquement par absorption compétitive du rayonnement d’excitation. Des solutions permettant de s’affranchir des interférences des métabolites secondaires sont à l’étude. / Tuberculosis kills nearly 2 million people each year, mainly because of late or inefficient diagnostic or late cures. The most efficient methods are often too expensive and too complex to implement in developing countries, areas of greater incidence of the disease. The aim of this project is the design of luminescent sensors for the detection of a very specific tuberculosis metabolite, nicotinic acid, detected in concentration ranging from around ten to hundred ppq, present in sick people’s breath, and to discriminate it from other metabolites.A terbium nitrate complex is used as its luminescence can be sensitized by organic ligands, as nicotinic acid. A first step was the optimization of the pH of aqueous solution to enhance the complexation between Tb3+ ion and nicotinic acid. A solution buffered at pH 6,4 using hexamine allows optimization of the complex formation and energy transfer from nicotinic acid to terbium. Sampling of nicotinic acid can be done in the range 400 nM-100 μM, or from 7,2 to 1,8 ppm.The second step was to design nanoporous matrices from silicon alcoxydes to obtain matrix with an intraporous pH of 6,4. We studied the changes of the matrix intraporous pH while trapping water vapor or carbon dioxide, present in high concentration in breath, using bromothymol blue as pH indicator. The matrices were produced from 2 silicon precursors, one of them containing an aminopropyle carbon chain, conferring an alkaline nature. Changes of the matrix pH between 6,5 and 6 were observed following the exposure of a silica matrix containing 3 % of the aminated precursor to water vapor to saturation. This range of pH value is optimized to favor Tb3+-nicotinic acid complex formation.In the last step, silica matrix containing 3% of the aminated precursor, doped with terbium and buffered at pH 6,4 with hexamine were designed. Luminescence measurements made on matrix exposed to vapors from pure nicotinic acid or saturated aqueous solution, showed an increase of the matrix luminescence, proof of the trapping of nicotinic acid in the nanoporous matrix and of the complexation between nicotinic acid and Tb3+. Trapping of nicotinic acid and subsequent complexation with Tb3+ are lowered by the presence of water vapor, which can partially deactivate the luminescent excited state of Tb3+. Interference studies showed that secondary metabolites as methyl nicotinate can only affect the luminescence of Tb3+/AN complex by competitive absorption of the excitation radiation. Detection methods free of interferences from the secondary metabolites are studied.

Micro-encapsulation of heart explant-derived stem cells (EDCs) within protective nanoporous gel (NPG) cocoons improves cardiac function and long-term retention of transplanted cells after ischemic injury by limiting detachment induced cell death and vascular clearance of intramyocardial injected cells. Although cocooned EDCs boost cardiac function, the fundamental mechanism is unclear. Here, we investigate the effects of altering cocoon stiffness and size on human EDC mediated repair of damaged myocardium using an immunodeficient mouse model of ischemic cardiomyopathy. First, we found that increasing cocoon stiffness by altering NPG content boosted cell viability and migration; effectively forcing cocooned cells to adopt a migratory, invasive phenotype. Although cocooning improved retention of transplanted cells, increasing cocoon stiffness had no additional effects on long-term engraftment despite markedly improving cardiac function and fibrosis after myocardial infarction. Given increased cocoon stiffness boosted the production and microRNA cargo within EDC nanovesicles, the observed benefits in post-ischemic function are likely dependent more on paracrine production of transplanted cells rather than simply increasing the number of cells retained. The effect of cocoon diameter on EDC phenotype and cell mediated repair of ischemic myocardium was evaluated using microfluidic-based cocooning enabling deterministic encapsulation within defined cocoon size and intracapsular cell number while maintaining a fixed cocoon stiffness. Increased cocoon size enhanced post-ischemic cardiac function by reducing clearance of transplanted cells and increased paracrine stimulation of endogenous repair. The latter being attributable to microfluidic cocooning closely following the expected Poisson distribution with smaller cocoons having a greater proportion of single cells while larger cocoons contained greater proportions of multicellular aggregates which enhanced cell-cell interactions to increase the amount and breadth of cytokines/nanoparticles delivered to injured myocardium. In conclusion, altering the biophysical properties of NPG surrounding cocooned cells provides a straightforward means of boosting the regenerative potential of heart EDCs for repair of injured myocardium.

Nanostructured materials have received a surge of interest in recent years since it has become apparent that reducing the size of a material often leads to heightened mechanical behavior. From a fundamental standpoint, this stems from the confinement of dislocations. Applications in microelectromechanical devices, lithium ion batteries, gas sensing and catalysis are realized by combining the improvements in mechanical behavior from material size reduction with the heightened chemical activity offered by materials with a high surface-area-to-volume ratio. In this study, films of nanoporous Si-Mg were produced through magnetron sputtering, followed by dealloying using an environmentally benign process with distilled water. The film composition and structure was characterized both at the surface and throughout the film thickness, while the mechanical behavior was explored with nanoindentation. Dispenser cathodes operate via thermionic emission and are an important area of interest in vacuum electron devices. While scientists have known for many years what elemental constituents are used to manufacture dispenser cathodes of excellent emission behavior, a fundamental understanding has yet to be realized. In this study, components of a scandate cathode that exhibited excellent emission behavior were characterized and used to inform the study of model thin films. Isolating relevant components of the scandate cathode for careful study could help inform future breakthroughs in understanding the working mechanism(s) of the scandate cathode. The structure, composition and electronic behavior of model W-Al alloy films were characterized experimentally and compared to computation. Moreover, a unique vacuum chamber was designed to activate modern thermionic dispenser cathodes, observe residual gas species present, and measure the work function through various state-of-the-art techniques.

Transport Membrane Condenser (TMC) is an innovative technology based on the property of a nano-scale porous material which can extract both waste heat and water from exhaust gases. This technology tremendously improves the efficiency of boilers and gas/coal combustors by lowering waste heat and increasing water recovery. Contaminants in the flue gases, such as CO2, O2, NOx, and SO2 are inhibited from passing through the membrane by the membrane’s high selectivity. The condensed water through these tubes is highly pure and can be used as the makeup water for many industrial applications. The goal of this research is to investigate the heat transfer, condensation rate, pressure drop and overall performance of crossflow heat exchangers. In this research, a numerical model has been developed to predict condensation of water vapor over and inside of nano-porous layers. Both capillary condensation inside the nanoscale porous structure of the TMC and the surface condensation were considered in the proposed method using a semi-empirical model. The transport of the water vapor and the latent heat of condensation were applied in the numerical model using the pertinent mass, momentum, turbulence and energy equations. By using the proposed model and simulation procedure, the effect of various inlet parameters such as inlet mass flow rate, inlet temperature, and water vapor content of the inlet flow on the performance of the cross-flow TMC heat exchanger was studied to obtain the optimum performance of the heat exchangers at different working conditions. The performance of the TMC heat exchangers for inlet flue gas rate 40 to 120 kg/h, inlet water rate 60 to 140 kg/h, inlet flue gas relative humidity 20 to 90%, and tube pitch ratio 0.25 to 2.25 has been studied. The obtained results show that the water condensation flux continuously increases with the increase of the inlet flue-gas flow rate, water flow rate, and the flue-gas humidity. The total heat flux also follows the same trend due to the pronounced effect of the latent heat transfer from the condensation process. The water condensation flux and the overall heat transfer increase at the beginning for small values of the tube pitches and then decreases as the tube pitch increases furthermore. In addition to the cross-flow TMC heat exchangers, the performance of a shell and tube TMC heat exchanger for high pressure and temperature oxy-combustion applications has been investigated. The performance analysis for a 6-heat exchanger TMC unit shows that heat transfer of the 2-stage TMC unit is higher than the 2-stage with the same number of the heat exchanger in each unit.