Poly(ethylene oxide) (PEO) is known for facilitating the electrospinning of biopolymer solutions, that are otherwise not electrospinnable. The objective of this study was to investigate the mechanism by which PEO enables the formation of whey protein isolate (WPI) electrospun fibers under different pH conditions. This investigation revealed that the addition of PEO increased the viscosity of WPI/PEO (10% w/w WPI; 0.4% w/w PEO) solutions. Difference in pH levels of the polymer solutions affected electrospinnability and fiber morphology. Acidic solutions resulted in smooth fibers (700 ± 105 nm) while neutral solutions produced spheres (2.0 ± 1.0 um) linked with ultrafine fibers (138 ± 32 nm). In comparison, alkaline solutions produced fibers (191 ± 38 nm) that were embedded with spindle-like beads (1.0 ± 0.5 um). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analyses revealed that the native globular configuration of WPI was not altered under neutral conditions. By contrast, the electrophoresis and spectrometry data indicated that WPI was denatured and hydrolyzed under acidic conditions, which facilitated the formation of smooth fibers. C13 nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies showed that the increase random coil and a-helix secondary structures in WPI contributed to the formation of bead-less electrospun fibers. Also, C13 NMR analysis showed no evidence of chemical interaction between WPI and PEO. Scanning transmission electron microscopy coupled with energy dispersive X-rays (STEM-EDAX) revealed that WPI was uniformly distributed within WPI/PEO electrospun fibers. Observations by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) indicated that fibers possessed a solid core. All these findings suggested that PEO enables the formation of WPI/PEO electrospun fibers by entanglement/entrapment/deposition. Preliminary studies were conducted on hydroxypropyl methyl cellulose (HPMC). In the absence of PEO, HPMC enabled the formation of WPI electrospun fibers under acidic conditions (124 ± 46 nm). FTIR analyses indicated that there was no interaction between HPMC and WPI, suggesting that HPMC aided in the electrospinning of WPI fibers, also by entanglement/entrapment/deposition. Hence, HPMC and PEO aid in the electrospinning of WPI fibers by entanglement/entrapment/deposition, which can be manipulated by alterations in the protein configuration and solution properties. / Natural Sciences and Engineering Research Council (NSERC) of Canada and the Dairy Farmers of Ontario (DFO)

Thesis (Ph.D.)--Ohio University, November, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: John F. Rabolt, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 109-113). Also available via the World Wide Web.

Thesis (D.Eng.)--University of Delaware, 2009. / Principal faculty advisors: John F. Rabolt and D. Bruce Chase, Dept. of Materials Science & Engineering. Includes bibliographical references.

Properties of textiles have great influences on the thermo-physiological and skin sensorial wear comfort of the human body. Sportswear is expected to have good moisture management property, which is key factor to achieve wear comfort. For some sports, they are also expected to have low friction with skin and antibacterial capability. To meet these demands, single-layer fabrics are utterly incompetent. Thus, model dual-layer textiles that consist of a thin hydrophobic electrospun inner layer and a thick hydrophilic electrospun outer layer are designed and fabricated to verify the possibility to simultaneously achieve dual functionalities, including good moisture transport property, with low friction with skin or good antibacterial property. The hydrophobic inner layer ensures low water absorption and transmission of sweat via capillary motion, while the hydrophilic outer layer draws the sweat out from the inner layer and facilitates evaporation to the surrounding environment. In the PhD work presented in this thesis, electrospun nanofibrous mats are used as the model textiles because they have large specific surface area due to a lot of interpenetrating pores between the nanofibers, which could facilitate both the capillary motion and effect of surface modification and incorporation of functional materials. Also, to let the moisture transport away fast, fairly thin hydrophobic inner layers could be achieved by electrospinning because it could control the thickness accurately. To improve the moisture transport property, the capillary motion in the textile is facilitated by decreasing the pore size or increasing the surface hydrophilicity. Dual-layer mats composed of a thick layer of hydrophilic polyacrylonitrile (PAN) nanofibers and a thin layer of hydrophobic polystyrene (PS) nanofibers with and without interpenetrating nanopores are fabricated respectively. Then the mats are coated with polydopamine (PDOPA) to different extents to tailor the water wettability of the PS layer. It is found that with a large quantity of nanochannels, the porous PS nanofibers exhibit a stronger capillary effect than the solid PS nanofibers. The capillary motion in the porous PS nanofibers can be further enhanced by slight surface modification with PDOPA while retaining the large hydrophilicity difference between the two layers, inducing a strong push-pull effect to transport water from the PS to the PAN layer. To lower the friction between the textile and skin, both of the hydration of the skin and the chemical component of textiles are modified. Core-shell nanofibers with a PAN-rich core and a poly (vinylidene fluoride) (PVDF)-rich shell are fabricated by single-spinneret electrospinning and used as the inner layer of the dual-layer mats. The dual-layer textile has good moisture transport property and the inner layer of the textile has lower friction with the skin, because the PAN in the inner layer could increase the wettability of the layer, thus improve the capillary effect, and the PVDF-rich shell could lower the friction between the textile and the skin. The synergistic combination of a considerably hydrophobic PAN/PVDF inner layer and a highly hydrophilic CA outer layer induces a strong push-pull effect, resulting in efficient moisture-wicking. To introduce antibacterial property to the dual-layer textile, zinc oxide (ZnO) NPs were covalently attached on the surface of the ethoxysilane-functionalized cross-linked PVDF inner layer. The results of related testes show that the incorporation of the ZnO NPs could render the textile antibacterial property as well as enhance the water wettability of the inner, thus the moisture transport property of the textile is also strongly improved. Also, the ZnO NPs show very good anti-wash property due to the covalent bonding with the inner layer. Thus the potential health risk caused by the detachment of the NPs could be avoided. In summary, the research results presented in this thesis provide effective strategies to enhance the capillary motion and moisture transport property of the textile, as well as achieve dual functionalities. The design concepts demonstrated in this PhD research can be used as model systems for development of novel multifunctional textiles in industries.

O objetivo deste estudo foi produzir, por electrospinning, fibras de pentóxido de nióbio(Nb2O5), usando como precursor o nióbio metálico. A solução utilizada para o electrospinning foi preparada pela dissolução do precursor em ácido fluorídrico (HF), seguida da adição de ácido acético e da solução polimérica de polivinilpirrolidona (PVP). A solução final foi submetida ao processo de electrospinning com tensão elétrica variando de 14 a 16 kV, distância entre coletor e capilar de 13 cm e fluxo de 1,5 mL/h. As fibras obtidas foram submetidas a tratamento térmico às temperaturas de 600, 700 e 800°C por um período de 1 hora, com taxa de aquecimento de 0,8°C/min. As fibras foram caracterizadas através de análises térmicas, espectroscopia de infravermelho por transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), espectroscopia de reflectância difusa (ERD). Também foram realizadas medidas de tamanho de cristalito pela fórmula de Scherrer, diâmetro médio com auxílio do aplicativo Image Tool e área superficial pelo modelo proposto por Brunnauer, Emmet e Teller (BET). Os resultados indicaram que foram formadas fibras da fase hexagonal (TT- Nb2O5), e que o aumento da tensão aplicada provocou uma redução no diâmetro das fibras, sendo 90 nm, o menor diâmetro médio obtido para as fibras produzidas aplicando uma tensão de 16 kV e sinterização a 700 ºC. O tamanho de cristalito médio aumentou de 18,48 para 36,08 nm, com o aumento da temperatura de tratamento térmico, resultando em queda da área superficial de 43,6 para 31,3 m2/g. Os valores de band gap medidos variaram de 3,32 a 3,57 eV, indicando que as nanofibras são semicondutores de gap largo. / This study aimed to produce by electrospinning, niobium pentoxide (Nb2O5) fibers, using metallic niobium as precursor. The solution used for electrospinning was prepared by dissolving the precursor in hydrofluoric acid (HF), followed by addition of acetic acid and solution of PVP polymer. The final solution was subjected to the process of electrospinning with voltage ranging from 14 to 16 kV, the distance between collector and capillary was 13 cm and flow of 1.5 mL / h. Fibers obtained were subjected to heat treatment at temperatures of 600, 700 and 800 ° C for a period of 1 hour, at a heating rate of 0.8 °C / min. Finally, Nb2O5 fibers were characterized by thermal analysis, Fourier Transform Infrared Spectroscopy(FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (ERD). The crystallite size was measured by the Scherrer equation, the average diameter was obtained by Image Tool and the surface area by the model proposed by Brunnauer, Emmet and Teller (BET). The results showed that fibers were formed and presented hexagonal phase (TT-Nb2O5), and that the increase of the voltage caused a decrease in fiber diameter, with the smallest average diameter of 90 nm, obtained for fibers produced by applying a voltage of 16 kV and sintering at 700 °C. The average crystallite size increased from 18.48 to 36.08 nm with increasing calcination temperature, resulting in decreased surface area of 43.568 to 31.344 m2 / g. The band gap values measured ranged from 3.32 to 3.57 eV, indicating that the nanofibers are wide band gap semiconductors.

O objetivo deste estudo foi produzir, por electrospinning, fibras de pentóxido de nióbio(Nb2O5), usando como precursor o nióbio metálico. A solução utilizada para o electrospinning foi preparada pela dissolução do precursor em ácido fluorídrico (HF), seguida da adição de ácido acético e da solução polimérica de polivinilpirrolidona (PVP). A solução final foi submetida ao processo de electrospinning com tensão elétrica variando de 14 a 16 kV, distância entre coletor e capilar de 13 cm e fluxo de 1,5 mL/h. As fibras obtidas foram submetidas a tratamento térmico às temperaturas de 600, 700 e 800°C por um período de 1 hora, com taxa de aquecimento de 0,8°C/min. As fibras foram caracterizadas através de análises térmicas, espectroscopia de infravermelho por transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), espectroscopia de reflectância difusa (ERD). Também foram realizadas medidas de tamanho de cristalito pela fórmula de Scherrer, diâmetro médio com auxílio do aplicativo Image Tool e área superficial pelo modelo proposto por Brunnauer, Emmet e Teller (BET). Os resultados indicaram que foram formadas fibras da fase hexagonal (TT- Nb2O5), e que o aumento da tensão aplicada provocou uma redução no diâmetro das fibras, sendo 90 nm, o menor diâmetro médio obtido para as fibras produzidas aplicando uma tensão de 16 kV e sinterização a 700 ºC. O tamanho de cristalito médio aumentou de 18,48 para 36,08 nm, com o aumento da temperatura de tratamento térmico, resultando em queda da área superficial de 43,6 para 31,3 m2/g. Os valores de band gap medidos variaram de 3,32 a 3,57 eV, indicando que as nanofibras são semicondutores de gap largo. / This study aimed to produce by electrospinning, niobium pentoxide (Nb2O5) fibers, using metallic niobium as precursor. The solution used for electrospinning was prepared by dissolving the precursor in hydrofluoric acid (HF), followed by addition of acetic acid and solution of PVP polymer. The final solution was subjected to the process of electrospinning with voltage ranging from 14 to 16 kV, the distance between collector and capillary was 13 cm and flow of 1.5 mL / h. Fibers obtained were subjected to heat treatment at temperatures of 600, 700 and 800 ° C for a period of 1 hour, at a heating rate of 0.8 °C / min. Finally, Nb2O5 fibers were characterized by thermal analysis, Fourier Transform Infrared Spectroscopy(FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (ERD). The crystallite size was measured by the Scherrer equation, the average diameter was obtained by Image Tool and the surface area by the model proposed by Brunnauer, Emmet and Teller (BET). The results showed that fibers were formed and presented hexagonal phase (TT-Nb2O5), and that the increase of the voltage caused a decrease in fiber diameter, with the smallest average diameter of 90 nm, obtained for fibers produced by applying a voltage of 16 kV and sintering at 700 °C. The average crystallite size increased from 18.48 to 36.08 nm with increasing calcination temperature, resulting in decreased surface area of 43.568 to 31.344 m2 / g. The band gap values measured ranged from 3.32 to 3.57 eV, indicating that the nanofibers are wide band gap semiconductors.

O objetivo deste estudo foi produzir, por electrospinning, fibras de pentóxido de nióbio(Nb2O5), usando como precursor o nióbio metálico. A solução utilizada para o electrospinning foi preparada pela dissolução do precursor em ácido fluorídrico (HF), seguida da adição de ácido acético e da solução polimérica de polivinilpirrolidona (PVP). A solução final foi submetida ao processo de electrospinning com tensão elétrica variando de 14 a 16 kV, distância entre coletor e capilar de 13 cm e fluxo de 1,5 mL/h. As fibras obtidas foram submetidas a tratamento térmico às temperaturas de 600, 700 e 800°C por um período de 1 hora, com taxa de aquecimento de 0,8°C/min. As fibras foram caracterizadas através de análises térmicas, espectroscopia de infravermelho por transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), espectroscopia de reflectância difusa (ERD). Também foram realizadas medidas de tamanho de cristalito pela fórmula de Scherrer, diâmetro médio com auxílio do aplicativo Image Tool e área superficial pelo modelo proposto por Brunnauer, Emmet e Teller (BET). Os resultados indicaram que foram formadas fibras da fase hexagonal (TT- Nb2O5), e que o aumento da tensão aplicada provocou uma redução no diâmetro das fibras, sendo 90 nm, o menor diâmetro médio obtido para as fibras produzidas aplicando uma tensão de 16 kV e sinterização a 700 ºC. O tamanho de cristalito médio aumentou de 18,48 para 36,08 nm, com o aumento da temperatura de tratamento térmico, resultando em queda da área superficial de 43,6 para 31,3 m2/g. Os valores de band gap medidos variaram de 3,32 a 3,57 eV, indicando que as nanofibras são semicondutores de gap largo. / This study aimed to produce by electrospinning, niobium pentoxide (Nb2O5) fibers, using metallic niobium as precursor. The solution used for electrospinning was prepared by dissolving the precursor in hydrofluoric acid (HF), followed by addition of acetic acid and solution of PVP polymer. The final solution was subjected to the process of electrospinning with voltage ranging from 14 to 16 kV, the distance between collector and capillary was 13 cm and flow of 1.5 mL / h. Fibers obtained were subjected to heat treatment at temperatures of 600, 700 and 800 ° C for a period of 1 hour, at a heating rate of 0.8 °C / min. Finally, Nb2O5 fibers were characterized by thermal analysis, Fourier Transform Infrared Spectroscopy(FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (ERD). The crystallite size was measured by the Scherrer equation, the average diameter was obtained by Image Tool and the surface area by the model proposed by Brunnauer, Emmet and Teller (BET). The results showed that fibers were formed and presented hexagonal phase (TT-Nb2O5), and that the increase of the voltage caused a decrease in fiber diameter, with the smallest average diameter of 90 nm, obtained for fibers produced by applying a voltage of 16 kV and sintering at 700 °C. The average crystallite size increased from 18.48 to 36.08 nm with increasing calcination temperature, resulting in decreased surface area of 43.568 to 31.344 m2 / g. The band gap values measured ranged from 3.32 to 3.57 eV, indicating that the nanofibers are wide band gap semiconductors.

Surface enhanced Raman spectroscopy (SERS) has great potential for design of next generation point-of-care (POC) diagnostic devices. However, its practical application in medical diagnosis is limited due to high cost of SERS substrates. The goal for this thesis was to develop affordable SERS substrates, and demonstrate their efficacy in the detection and assay of a Raman probe and diabetes biomarkers, using 514nm and 1064nm Raman spectrometers. Rapid and less energy intensive methods were optimised for manufacturing three categories of SERS substrates: 1) chemically roughened silver (Ag) metal, 2) Ag and gold (Au) nanoparticles (NPs) prepared using microemulsions, and 3) Ag and Au NPs’ coated insoluble electrospun membranes. Immersion of Ag metal for 30 seconds in ammonia (NH4OH), followed by 10 seconds in nitric acid (HNO3) produced optimum roughened Ag metal SERS substrates. For synthesis of gold (Au) and Ag NPs, microemulsion compositions were varied, and the use of sodium borohydrate (NaBH4) produced the desired larger sizes and anisotropic shapes of the NPs. Nanostructured planar SERS structures based on insoluble electrospun membranes, were prepared by covalently binding Au or Ag NPs, on electrospun poly acrylic acid-ethylene glycol (PAA-EG) fibres. Ag metal SERS substrates provided the best SERS enhancement for the Raman probe molecule, 4-methylbenzenethiol (MBT), with a detection limit of 1aM, using 514nm Raman spectrometer. The Ag metal SERS substrates were then used to demonstrate proof-of-concept for the use of SERS for assay of diabetes biomarkers. The higher laser intensity of 106nm Raman caused burning of the dry NPs’ incorporated SERS substrates; but the thermally conductivity of solid Ag in Ag metal SERS substrate allowed SERS detection of 1nM MBT. To conclude, chemically roughened Ag metal SERS substrates proved cost effective and robust for quantitative SERS detection of MBT and diabetes biomarkers both with 514nm and 1064nm Raman spectrometers.