The adsorption and separation of platinum(IV) and palladium(II) chlorido species (PtCl₆²⁻ and PdCl₄²⁻) on polystyrene-based beads and nanofibers as well as silica microparticles functionalized with polyamine centres derived from ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) is described. The functionalized sorbent materials were characterized by using microanalysis, SEM, XPS, BET and FTIR. The nanofiber sorbent material functionalized with ethylenediamine (F-EDA) had the highest loading capacity which was attributed to its high nitrogen content (10.83%) and larger surface area (241.3m²/g). The adsorption and loading capacities of the sorption materials were investigated using both the batch and column studies in 1 M HCI. The adsorption studies for both PtCl₆²⁻ and PdCl₄²⁻ on the polystyrene-based sorbent materials fit the Langmuir isotherm while the silica-based sorbents fitted the Freundlich isotherm with R² values > 0.99. In the column experiment the highest loading capacity of Pt and Pd were 7.4 mg/g and 4.3 mg/g respectively on the nanofiber sorbent material based on ethylenediamine (EDA). The polystyrene and silica-based resins with triethylenetetramine (TETA) functionality (M-TETA and S-TETA) showed selectivity for platinum and palladium, respectively. Metal chlorido complexes loaded on the sorbent materials were recovered by using 3% m/v thiourea solution as teh eluting agent with quantitative desorption efficiency under the selected experimental conditions. The separation of platinum from palladium was partially achieved by selective stripping of PtCl₆²⁻ with 0.5 M of NaClO₄ in 1.0 M HCI with PdCl₄²⁻ was eluted with 0.5 M thiourea in 1.0 M HCI. The selectivity of the M-TETA and S-TETA sorbent materials was proved by column separation of platinum(IV) and palladium(II), respectively, from synthetic solutions containing iridium(IV) and rhodium(III). The loading capacity for platinum on M-TETA was 0.09 mg/g while it was 0.27 mg/g for palladium on S-TETA. / Acrobat PDFMaker 10.1 for Word / Adobe Acrobat 9.54 Paper Capture Plug-in

Bidentate imidazole-based extractants, 1-octylimidazole-2-aldoxime (OIMOX) and 1-octyl-2-(2′-pyridyl)imidazole (OPIM), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Cu²⁺and Ni²⁺ respectively from base metals in a solvent extraction system. The study was extended to evaluate the sorption and separation of Ni²⁺ from other base metals in a solid-solution system using microspherical Merrifield resins and nanofibers functionalized with 2,2′-pyridylimidazole. Copper was effectively separated with OIMOX and DNNSA as extractants from nickel with ΔpH½ ≈1.05 and the extraction order of Cu²⁺ > Ni²⁺ > Zn²⁺ > Cd²⁺> Co²⁺ was achieved as a function of pH. At pH 1.65 the extracted copper, from a synthetic mixture of the base metals reached 90.13(±0.90)%, and through a two-step extraction process 98.22(±0.29)% copper was recovered with negligible nickel and cobalt impurities. Stripping of the copper from the loaded organic phase using TraceSelect sulphuric acid at pH 0.35 yielded 96.60(±0.44)% of the loaded quantity after the second stage of stripping. The separation of Ni²⁺ from the borderline and hard acids; Co²⁺, Cu²⁺, Zn²⁺, Fe2²⁺, Fe²⁺, Mn²⁺, Mg2²⁺ and Ca²⁺ at a pH range of 0.5-3.5 with OPIM and DNNSA was acvieved to the tune of a ΔpH½≈ 1.6 with respect to cobalt from a sulfate and sulfate/chloride media. A three-stage counter-current extraction of Ni²⁺, at the optimized pH of 1.89, from a synthetic mixture of Ni²⁺, Co²⁺ and Cu²⁺, yielded 99.01(±1.79)%. The total co-extracted Cu²⁺ was 48.72(±0.24)% of the original quantity in the mixture, and it was 19.85(±0.28%) for Co²⁺. The co-extracted Cu²⁺ was scrubbed off from the loaded organic phase at pH≈8.5 by using an ammonium buffer, while co-extracted Co²⁺ was selectively and quantitatively stripped with H₂SO₄ at pH 1.64. The total recovery of Ni²⁺ by stripping at pH 0.32 was 94.05(±1.70)%. In the solid-liquid system, Ni²⁺ was separated from Co²⁺, Cu²⁺, and Fe²⁺ with the microspherical resins funtionalised with 2,2′-pyridylimidazole by a separation factor (β) in the range 22-45. Electrospun nanofibers as sorbents yielded high sorption capacity in the range of 0.97 - 1.45 mmol.g⁻¹ for the same metals ions. Thus, 1-octylimidazole-2-aldoxime (OIMOX), and1-octyl-2-(2′-pyridyl)imidazole (OPIM) can be effectively utilized alongside DNNSA as a co-extractant in the separation of Cu²⁺ and Ni²⁺ respectively from base metals in acidic sulfate medium in a solvent extraction process, and the latter as a selective ligand in the solid-liquid separation of Ni²⁺ from Co²⁺, Cu²⁺, and Fe²⁺.

No description available.

Orientador: Nelson Eduardo Durán Caballero / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T20:45:34Z (GMT). No. of bitstreams: 1 Ridolfi_DanielaMissiani_D.pdf: 3264748 bytes, checksum: faea0a4fec50e345e79d3072a773bb48 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho nanofibras de quitosana/poli (óxido de etileno) (PEO) (5:1) com nanocristais de celulose (NCC) foram produzidas com sucesso por eletrofiação e foi verificado o efeito da adição dos NCC nas propriedades das nanofibras obtidas. Os ensaios de eletrofiação foram realizados com amostras de NCC obtidas por hidrólise ácida. A eletrofiação de soluções de quitosana, sem e com NCC, resultaram na formação de muitas gotas (beads). Portanto, foi necessário adicionar o PEO nas soluções. Embora a adição de PEO tenha favorecido a formação de fibras, as soluções de quitosana/PEO sem NCC geraram também gotas enquanto que as soluções de quitosana/PEO contendo NCC resultaram em fibras uniformes. As soluções de quitosana/PEO com NCC apresentaram maior viscosidade em relação à solução sem NCC, o que pode ter favorecido a formação de fibras uniformes. As soluções de quitosana/PEO contendo 10% (m/m) de NCC produziram fibras mais finas em relação às soluções com 5% (m/m) de NCC provavelmente devido à maior condutividade da solução. Análises termogravimétricas mostraram que os NCC interferem na decomposição do PEO, mas sem prejudicar o desempenho do material. As nanofibras de quitosana/PEO contendo NCC apresentaram menor cristalinidade em relação às nanofibras sem NCC. Resultados de ensaios com células em culturas de fibroblastos 3T3 mostraram que as nanofibras de quitosana/PEO (com 10% de NCC) promoveram a adesão celular e mantiveram a morfologia celular característica o que sugere um potencial dessas nanofibras para aplicações em engenharia de tecidos / Abstract: In this work chitosan/ poly (ethylene oxide) (PEO) (5:1) nanofibers with cellulose nanocrystals (CNC) were successfully produced by the electrospinning technique and the effect of the addition of CNC on the nanofibers properties was evaluated. The electrospinning assays were performed with samples of CNC obtained by acid hydrolysis. The electrospinning of chitosan solutions, with and without CNC, resulted in the formation of many drops (beads). Therefore, it was necessary to add PEO on solutions. Although the PEO addition has favored the fiber formation, the chitosan/PEO solutions without CNC showed beads while chitosan/PEO solutions with CNC resulted in uniform fibers. The chitosan/PEO solutions with CNC showed higher viscosity compared to the solution without CNC, which may have favored the formation of uniform fibers. Solutions of chitosan/PEO containing 10% (w/w) of CNC produced thinner fibers compared to solutions containing 5% (w/w) of CNC probably due the higher solution conductivity. Thermogravimetric analysis (TGA) showed that the CNC has an effect on the PEO decomposition, however, it does not impair the performance of the material. The chitosan/PEO nanofibers with CNC showed lower crystallinity compared the nanofibers without CNC. Results from cell assay in cultures of 3T3 fibroblasts showed that the chitosana/PEO nanofibers (with 10% of CNC) promoted cell attachment and maintained the characteristic cell morphology which suggests potential applications of these nanofibers in cell tissue engineering / Doutorado / Físico-Química / Doutora em Ciências

Electronic skin (e-skin) materials have gained a wide range of attention due to their multiple applications in different areas, including soft robotics, skin attachable electronics, prosthetics, and health care. These materials are required to emulate tactile perceptions and sense the surrounding environments while maintaining properties such as flexibility and stretchability. Current e-skin fabrication techniques, such as photolithography, screen printing, lamination, and laser reducing, have limitations in terms of costs and manufacturing scalability, which ultimately preventing e-skin widespread usage. In this work, we introduce conductive stretchable 3D printable skin-like nanocomposite material. Our nanocomposite is easily 3D printed, cost-effective, and actively senses physical stimuli, such as strain and pressure, which gave them the potential to be used in prosthetics, skin-attachable electronics, and soft robotics applications. Using the conductive properties of carbon nanofibers, alongside a polymeric matrix based on Smooth-on platinum cured silicone and crosslinked PDMS, we can obtain a flexible and stretchable material that resembles human skin and can conduct electricity. A great advantage in our composite is the ability to tune its mechanical properties to fit the desired application area through varying PDMS's chain lengths and composition ratios in the nanocomposite. Also, the interconnecting network of micrometer-long nanofibers allows the measurement of resistivity changes upon physical stimuli, granting the nanocomposite sensing abilities. Moreover, we explored and optimized 3D printing of the nanocomposite material, which offering simplicity and versatility for fabricating complex 3D structures at lower costs.

The main goal of this diploma´s thesis is to review final qualities of traditional porcelain body with using nanofibers. The theoretical part of the thesis summarizes the current knowledge of the research on ceramic composite with using nanofibers. The vast majority of these researches is engaged by reinforcing technical ceramics, on the other hand area of traditional porcelain is still unexplored area. Besides that there are shown technological ways of the production and dispersion of the most important types of nanofibers. In the practical part of this thesis is experimentaly defined the most effecient way of homogenization procedure and the most effecient dose of nanofibers for pure kaolin body. In conclusion are compared the resulting properties of traditional porcelain body with using Al2O3 and SiO2 nanofibers.

Polymer nanofibers have attracted a lot of industrial interest in the past decade. In general, these fibers need to be thermally stable for many applications, such as in the aerospace industry. However, most of these polymer nanofibers suffer from low temperature degradation, limiting their use in many potential applications. Graphene, which is one sheet of graphite, has unique properties such as high conductivity, and high thermal stability. This exceptional material can be incorporated into the polymer nanofibers as nanofillers in order to enhance their thermal properties. The aim of this dissertation is to investigate the effect of adding graphene nanofillers into the polymer fiber on the resulting fibers’ thermal properties. For that purpose, polyvinyl alcohol (PVA), a non-conductive polymer and a different source of graphene, namely graphene foam, expendable graphite and graphite powder were used. The growth technique was the electrospinning technique which offers a variety of parameters that need to be optimized. For this includes, the amount of PVA in the water solvent, the flow rate, the applied voltage, the growth time, and the tip/collector distance. In summary, it has been optimized that the best conditions for growth of fibers will be as follows: PVA concentration will be fixed at 10 wt%, flow rate will be 3 ml/h, applied voltage will be 30 kV, growth time of 60 s and tip/collector distance will be fixed at 12 cm. The resulted PVA fibers from these conditions were smooth continuous and hollow with diameter ranging between 190-340 nm, while PVA/graphene nano-fibers are much thinner with diameter ranging between 132 - 235 nm when the same parameters were used with only graphene concentration varied. The fiber obtained with PVA showed a hollow structure which is desirable for incorporation of graphene nanofillers. The dispersion of the different source of graphene sheets in the starting PVA solution showed enhanced thermal stability compared to the PVA fibers alone. Furthermore, an increase in the thermal stability is observed with increasing concentration of graphene nanofillers. This work shows the promising use of graphene as nanofillers for PVA fibers. This can be expended to other non-conductive and conductive polymers in order to broaden the application of these fibers in the industries, where thermal stability is a prerequisite. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Physics / unrestricted

Orientador: Deuber Lincon da Silva Agostini / Resumo: Neste trabalho foram produzidas nanofibras eletrofiadas constituídas de poli(álcool vinílico) (PVA) com poli(3,4-etilenodioxitiofeno):poli(estireno sulfonado) (PEDOT:PSS) (PVA/PEDOT:PSS) e nanofibras de poli(álcool vinílico) (PVA) com polipirrol (PPy) (PVA/PPy) com propriedades elétricas para utilização como sensores de gás. O PVA é um polímero isolante, solúvel em água com elevado peso molecular que lhe confere as características ideais para a produção de nanofibras, sendo este usado como polímero de suporte para os polímeros condutores PEDOT:PSS e PPy. Foram investigados o efeito das diferentes concentrações de PVA na produção das nanofibras eletrofiadas, onde a concentração de 6% apresentou os melhores resultados na formação de nanofibras. Também foram investigados a influência das concentrações de PEDOT:PSS e PPy na estrutura e propriedades das nanofibras eletrofiadas, através da análise morfológica e resistividade elétrica, no qual obteve-se a formação de nanofibras para todas as concentrações. Em seguida as nanofibras foram depositadas em eletrodos interdigitados para a realização das caracterizações elétricas e teste como sensor de gás, no qual comprovou-se a sensibilidade das nanofibras constituídas de condutor/isolante na presença de gás amônia (NH3). / Abstract: In this work were produced electrospunnanofibers of polyvinyl alcohol (PVA) with poly(3,4-ethylenedioxythiophene):poly(sulfonated styrene) (PEDOT:PSS) (PVA/PEDOT:PSS) and poly(vinyl alcohol) nanofibers (PVA) with polypyrrole (PPy) (PVA/PPy) with electrical properties for use as gas sensors. PVA is a high molecular weight water soluble insulating polymer which gives it the ideal characteristics for the production of nanofiber, which is used as a support polymer for the PEDOT:PSS and PPy conductive polymers. It wasinvestigated the effect of different PVA concentrations on the production of electrospunnanofibers, where the 6% concentration showed the best results in the formation of nanofibers. The influence of PEDOT:PSS and PPy concentrations on the structure and properties of nanofibers was also investigated, through morphological analysis and electrical resistivity, which obtained the formation of nanofibers for all concentrations. Then the nanofibers were deposited on interdigitated electrodes to perform the electrical characterization and test as a gas sensor, which proved the sensitivity of conductor / insulating nanofibers in the presence of ammonia gas (NH3). / Mestre

The demand for energy storage technologies is rapidly increasing in portable electronics, transportation, and renewable energy systems. Thus, the objective of this research is to develop and enhance the performance of Ni-based electrochemical supercapacitors by optimizing synthesis conditions and design of the electrode materials. Conventional and on-chip supercapacitors were developed with notable performance enhancement. For conventional supercapacitors, a uniform and conformal coating process was developed to deposit Ni(OH)2 nanoflakes on carbon microfibers in-situ by a simple chemical bath deposition at room temperature. The microfibers conformally-coated with Ni(OH)2 make direct physical contacts with essentially every single nanoflakes, leading to more efficient electron transport. Using this strategy, we have achieved devices that exhibit five times higher specific capacitance compared to planar (non-conformal) Ni(OH)2 nanoflakes electrodes prepared by drop casting of Ni(OH)2 on the carbon microfibers (1416 F/g vs. 275 F/g). For on-chip storage applications, microfabricated supercapacitors were developed using a combination of top-down photolithography and bottom-up CBD. The resulting Ni(OH)2 micro-supercapacitors show high-rate redox activity up to 500 V/s and an areal cell capacitance of 16 mF/cm2 corresponding to a volumetric stack capacitance of 325 F/cm3. This volumetric capacitance is 2-fold higher than carbon and metal oxide based micro-supercapacitors. Furthermore, these micro-supercapacitors show a maximum energy density of 21 mWh/cm3, which is superior to the Li-based thin film batteries. To enhance cycling stability, Ni-Cu-OH and Ni-Co-OH ternary electrodes have been prepared with different Ni:Cu and Ni:Co ratios by CBD at room temperature on carbon microfibers. It is observed that the electrodes with Ni:Cu and Ni:Co composition ratio of 100:10 results in an optimum capacitance and cycling stability. For the optimum composition, Ni-Co-OH with graphene and carbon nanofibers electrode was tested, with resultant improvement in electrode potential window, equivalent series resistance, and cyclic stability. To further increase energy density, Ni(OH)2//Graphene asymmetric supercapacitor were fabricated with areal capacitance of 253 mF/cm2 at 5 mA/cm2 which is higher than NiO//rGO prepared by hydrothermal method. Ni-Co-OH/G-CNF//Graphene asymmetric supercapacitor results in a maximum power of 23 mW within an operating voltage of 2.2 V which are higher than of Ni(OH)2//Graphene (15.94 mW within 1.8 V). Our asymmetric supercapacitors have flexible-electrodes, low-cost fabrication process and environmentally friendly materials.

Our work addresses a novel biocompatible plasmon-enhanced nanostructure approach based on the combination of metal nanoparticles, light emitting polymer-based nanostructures, and scalable cellulose nanofiber templates via a one-step facile electrospinning process that can easily be applied to biomedical devices. In collaboration with the Team of Prof. Lee Goldstein in the Boston University medical campus, we demonstrated light emission from small-size (below 200nm) polymer nanoparticles coupled to plasmonic nanoparticles and to light-emitting biocompatible molecules. In order to fully demonstrate the potential of our novel plasmonic nanostructures we developed Magnetic resonance imaging (MRI) reagent doped Polycaprolactone (Core)-Polyethylene glycol (shell) core-shell nanoparticles and studied their size distribution and dispersion properties in a phosphate buffered saline solution. Our materials were optimized in order to obtain no aggregation of the nanoparticles in solution. The presence of MRI reagent in nanoparticles were demonstrated via Inversion Recovery Sequences (IR) by characterizing the different T1 relaxation times. The concentration of Gd in the nanoparticles dispersion was estimated with different dilution of Gd commercial reagent as a reference. In addition, we combined facile electrospinning fabrication with top down nano-deposition and demonstrated a novel and scalable plasmonic resonant medium for rapid and reliable Raman scattering sensing of molecular monolayers and bacteria. Specifically, aided by PCA multivariate data analysis techniques, we demonstrated fingerprinting Surface Enhanced Raman Scattering (SERS) spectra of different bacteria strains (E. Coli K12, E. coli BL21 (DE3) and E. coli DH 5α) entrapped in our novel plasmonic networks. Finally, in this thesis we have also addressed the development of novel, Si-compatible and largely tunable plasmonic materials for biosensing applications in the mid-infrared spectral range and developed a novel type of transparent conductive oxide based on the Indium Silicon Oxide (ISO) material (Indium Silicon Oxide) that features enhanced surface smoothness and thermal stability compared to Indium tin oxide (ITO) and Titanium nitride (TiN) alternative plasmonic materials. In collaboration with our collaborators at Columbia University, we demonstrated the tunability of near-field plasmonic resonances from 1.8 to 5.0 μm as a function of different annealing temperature. This work provides an enabling first-step towards the development of novel Si-compatible materials with tunable plasmon resonances for metamaterials and sensing devices that operate across the infrared spectrum. / 2019-07-02T00:00:00Z