Matching Items (11)
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- All Subjects: Nanoparticles
- Creators: Westerhoff, Paul K
- Creators: Dai, Lenore L
- Creators: Green, Matthew
- Member of: Theses and Dissertations
Description
Liquid-liquid interfaces serve as ideal 2-D templates on which solid particles can self-assemble into various structures. These self-assembly processes are important in fabrication of micron-sized devices and emulsion formulation. At oil/water interfaces, these structures can range from close-packed aggregates to ordered lattices. By incorporating an ionic liquid (IL) at the interface, new self-assembly phenomena emerge. ILs are ionic compounds that are liquid at room temperature (essentially molten salts at ambient conditions) that have remarkable properties such as negligible volatility and high chemical stability and can be optimized for nearly any application. The nature of IL-fluid interfaces has not yet been studied in depth. Consequently, the corresponding self-assembly phenomena have not yet been explored. We demonstrate how the unique molecular nature of ILs allows for new self-assembly phenomena to take place at their interfaces. These phenomena include droplet bridging (the self-assembly of both particles and emulsion droplets), spontaneous particle transport through the liquid-liquid interface, and various gelation behaviors. In droplet bridging, self-assembled monolayers of particles effectively "glue" emulsion droplets to one another, allowing the droplets to self-assembly into large networks. With particle transport, it is experimentally demonstrated the ILs overcome the strong adhesive nature of the liquid-liquid interface and extract solid particles from the bulk phase without the aid of external forces. These phenomena are quantified and corresponding mechanisms are proposed. The experimental investigations are supported by molecular dynamics (MD) simulations, which allow for a molecular view of the self-assembly process. In particular, we show that particle self-assembly depends primarily on the surface chemistry of the particles and the non-IL fluid at the interface. Free energy calculations show that the attractive forces between nanoparticles and the liquid-liquid interface are unusually long-ranged, due to capillary waves. Furthermore, IL cations can exhibit molecular ordering at the IL-oil interface, resulting in a slight residual charge at this interface. We also explore the transient IL-IL interface, revealing molecular interactions responsible for the unusually slow mixing dynamics between two ILs. This dissertation, therefore, contributes to both experimental and theoretical understanding of particle self-assembly at IL based interfaces.
ContributorsFrost, Denzil (Author) / Dai, Lenore L (Thesis advisor) / Torres, César I (Committee member) / Nielsen, David R (Committee member) / Squires, Kyle D (Committee member) / Rege, Kaushal (Committee member) / Arizona State University (Publisher)
Created2013
Description
As the use of engineered nanomaterials (ENMs) in consumer products becomes more common, the amount of ENMs entering wastewater treatment plants (WWTPs) increases. Investigating the fate of ENMs in WWTPs is critical for risk assessment and pollution control. The objectives of this dissertation were to (1) quantify and characterize titanium (Ti) in full-scale wastewater treatment plants, (2) quantify sorption of different ENMs to wastewater biomass in laboratory-scale batch reactors, (3) evaluate the use of a standard, soluble-pollutant sorption test method for quantifying ENM interaction with wastewater biomass, and (4) develop a mechanistic model of a biological wastewater treatment reactor to serve as the basis for modeling nanomaterial fate in WWTPs. Using titanium (Ti) as a model material for the fate of ENMs in WWTPs, Ti concentrations were measured in 10 municipal WWTPs. Ti concentrations in pant influent ranged from 181 to 3000 µg/L, and more than 96% of Ti was removed, with effluent Ti concentrations being less than 25 µg/L. Ti removed from wastewater accumulated in solids at concentrations ranging from 1 to 6 µg Ti/mg solids. Using transmission electron microscopy, spherical titanium oxide nanoparticles with diameters ranging from 4 to 30 nm were found in WWTP effluents, evidence that some nanoscale particles will pass through WWTPs and enter aquatic systems. Batch experiments were conducted to quantify sorption of different ENM types to activated sludge. Percentages of sorption to 400 mg TSS/L biomass ranged from about 10 to 90%, depending on the ENM material and functionalization. Natural organic matter, surfactants, and proteins had a stabilizing effect on most of the ENMs tested. The United States Environmental Protection Agency's standard sorption testing method (OPPTS 835.1110) used for soluble compounds was found to be inapplicable to ENMs, as freeze-dried activated sludge transforms ENMs into stable particles in suspension. In conjunction with experiments, we created a mechanistic model of the microbiological processes in membrane bioreactors to predict MBR, extended and modified this model to predict the fate of soluble micropollutants, and then discussed how the micropollutant fate model could be used to predict the fate of nanomaterials in wastewater treatment plants.
ContributorsKiser, Mehlika Ayla (Author) / Westerhoff, Paul K (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Hristovski, Kiril D (Committee member) / Arizona State University (Publisher)
Created2011
Description
Environmentally responsive microgels have drawn significant attention due to their intrinsic ability to change volume in response to various external stimuli such as pH, temperature, osmotic pressure, or electric and magnetic fields. The extent of particle swelling is controlled by the nature of the polymer-solvent interaction. This thesis focuses on design and synthesis of environmentally responsive microgels and their composites, and encompasses methods of utilizing microgel systems in applications as vehicles for the adsorption, retention, and targeted delivery of chemical species. Furthermore, self-assembled microgel particles at ionic liquid (IL)-water interfaces demonstrate responsive colloidal lattice morphology. The thesis first reports on the fundamental aspects of synthesis, functionalization, and characteristic properties of multifunctional environmentally responsive microgels derived from poly(N-isopropylacrylamide) (PNIPAm) and other functional co-monomers. In particular, the uptake and release of active chemical species such as rheology modifiers into and from these ionic microgels is demonstrated. Moreover, a facile tunable method for the formation of organic-inorganic composites with Fe3O4 nanoparticles adsorbed and embedded within ionic microgel particles is explored. Additionally, the development of zwitterionic microgels (ZI-MG) is presented. These aqueous ZI-MG dispersions exhibit reversible parabolic swelling as a function of pH and display a minimum hydrodynamic diameter at a tunable isoelectric point (IEP). This study also elucidates the controlled uptake and release of surfactants from these particle systems. The extent of surfactant loading and the ensuing relative swelling/deswelling behaviors within the polymer networks are explained in terms of their binding interactions. The latter part of this thesis highlights the versatility of fluorescently labeled microgel particles as stabilizers for IL-water droplets. When the prepared particles form monolayers and equilibrate at the liquid-liquid interface, the colloidal lattice organization may re-order itself depending on the surface charge of these particles. Finally, it is shown that the spontaneously formed and densely packed layers of microgel particles can be employed for extraction applications, as the interface remains permeable to small active species.
ContributorsChen, Haobo (Author) / Dai, Lenore L (Committee member) / Chen, Kangping (Committee member) / Forzani, Erica (Committee member) / Lind, Mary Laura (Committee member) / Mu, Bin (Committee member) / Arizona State University (Publisher)
Created2015
Description
Drinking water filtration using reverse osmosis (RO) membranes effectively removes salts and most other inorganic, organic, and microbial pollutants. RO technologies are utilized at both the municipal and residential scale. The formation of biofilms on RO membranes reduces water flux and increases energy consumption. The research conducted for this thesis involves In-Situ coating of silver, a known biocide, on the surface of RO membranes. This research was adapted from a protocol developed for coating flat sheet membranes with silver nanoparticles, and scaled up into spiral-wound membranes that are commonly used at the residential scale in point-of-use (POU) filtration systems. Performance analyses of the silver-coated spiral-wound were conducted in a mobile drinking water treatment system fitted with two POU units for comparison. Five month-long analyses were performed, including a deployment of the mobile system. In addition to flux, salt rejection, and other water quality analyses, additional membrane characterization tests were conducted on pristine and silver-coated membranes.
For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system.
For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system.
ContributorsZimmerman, Sean (Author) / Westerhoff, Paul K (Thesis advisor) / Sinha, Shahnawaz (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2017
Description
Nitrate contamination to groundwater and surface water is a serious problem in areas with high agricultural production due to over application of fertilizers. There is a need for alternative technologies to reduce nutrient runoff without compromising yield. Carbon nanoparticles have adsorptive properties and have shown to improve germination and yield of a variety of crops. Graphite nanoparticles (CNP) were studied under a variety of different fertilizer conditions to grow lettuce for the three seasons of summer, fall, and winter. The aim of this thesis was to quantify the effect of CNPs on nitrate leaching and lettuce growth. This was accomplished by measuring the lettuce leaf yield, formulating a nutrient balance using the leachate, plant tissue, and soil data, and changing the hydraulic conductivity of the soil to assess the effect on nutrient mobility. summer and fall experiments used Arizona soil with different amounts of nitrogen, phosphorus, and potassium (NPK) fertilizer being applied to the soil with and without CNPs. The winter experiments used three different soil blends of Arizona soil, Arizona soil blended with 30% sand, and Arizona soil blended with 70% sand with a constant fertilizer treatment of 30% NPK with and without CNPs. The results showed that the 70% NPK with CNP treatment was best at reducing the amount of nitrate leached while having little to no compromise in yield. The winter experiments showed that the effectiveness of CNPs in reducing nitrate leaching and enhancing yield, improved with the higher the hydraulic conductivity of the soil.
ContributorsPandorf, Madelyn (Author) / Westerhoff, Paul K (Thesis advisor) / Boyer, Treavor (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2018
Description
Engineered nanoparticles (NPs) pose risk potentials, if they exist in water systems at significant concentrations and if they remain reactive to cause toxicity. Three goals guided this study: (1) establishing NP detecting methods with high sensitivity to tackle low concentration and small sizes, (2) achieving assays capable of measuring NP surface reactivity and identifying surface reaction mechanisms, and (3) understanding the impact of surface adsorption of ions on surface reactivity of NPs in water.
The size detection limit of single particle inductively coupled plasma spectrometry (spICP-MS) was determined for 40 elements, demonstrating the feasibility of spICP-MS to different NP species in water. The K-means Clustering Algorithm was used to process the spICP-MS signals, and achieved precise particle-noise differentiation and quantitative particle size resolution. A dry powder assay based on NP-catalyzed methylene blue (MB) reduction was developed to rapidly and sensitively detect metallic NPs in water by measuring their catalytic reactivity.
Four different wet-chemical-based NP surface reactivity assays were demonstrated: “borohydride reducing methylene blue (BHMB)”, “ferric reducing ability of nanoparticles (FRAN)”, “electron paramagnetic resonance detection of hydroxyl radical (EPR)”, and “UV-illuminated methylene blue degradation (UVMB)”. They gave different reactivity ranking among five NP species, because they targeted for different surface reactivity types (catalytic, redox and photo reactivity) via different reaction mechanisms. Kinetic modeling frameworks on the assay outcomes revealed two surface electron transfer schemes, namely the “sacrificial reducing” and the “electrode discharging”, and separated interfering side reactions from the intended surface reaction.
The application of NPs in chemical mechanical polishing (CMP) was investigated as an industrial case to understand NP surface transformation via adsorbing ions in water. Simulation of wastewater treatment showed CMP NPs were effectively removed (>90%) by lime softening at high pH and high calcium dosage, but 20-40% of them remained in water after biomass adsorption process. III/V ions (InIII, GaIII, and AsIII/V) derived from semiconductor materials showed adsorption potentials to common CMP NPs (SiO2, CeO2 and Al2O3), and a surface complexation model was developed to determine their intrinsic complexation constants for different NP species. The adsorption of AsIII and AsV ions onto CeO2 NPs mitigated the surface reactivity of CeO2 NPs suggested by the FRAN and EPR assays. The impact of the ion adsorption on the surface reactivity of CeO2 NPs was related to the redox state of Ce and As on the surface, but varied with ion species and surface reaction mechanisms.
The size detection limit of single particle inductively coupled plasma spectrometry (spICP-MS) was determined for 40 elements, demonstrating the feasibility of spICP-MS to different NP species in water. The K-means Clustering Algorithm was used to process the spICP-MS signals, and achieved precise particle-noise differentiation and quantitative particle size resolution. A dry powder assay based on NP-catalyzed methylene blue (MB) reduction was developed to rapidly and sensitively detect metallic NPs in water by measuring their catalytic reactivity.
Four different wet-chemical-based NP surface reactivity assays were demonstrated: “borohydride reducing methylene blue (BHMB)”, “ferric reducing ability of nanoparticles (FRAN)”, “electron paramagnetic resonance detection of hydroxyl radical (EPR)”, and “UV-illuminated methylene blue degradation (UVMB)”. They gave different reactivity ranking among five NP species, because they targeted for different surface reactivity types (catalytic, redox and photo reactivity) via different reaction mechanisms. Kinetic modeling frameworks on the assay outcomes revealed two surface electron transfer schemes, namely the “sacrificial reducing” and the “electrode discharging”, and separated interfering side reactions from the intended surface reaction.
The application of NPs in chemical mechanical polishing (CMP) was investigated as an industrial case to understand NP surface transformation via adsorbing ions in water. Simulation of wastewater treatment showed CMP NPs were effectively removed (>90%) by lime softening at high pH and high calcium dosage, but 20-40% of them remained in water after biomass adsorption process. III/V ions (InIII, GaIII, and AsIII/V) derived from semiconductor materials showed adsorption potentials to common CMP NPs (SiO2, CeO2 and Al2O3), and a surface complexation model was developed to determine their intrinsic complexation constants for different NP species. The adsorption of AsIII and AsV ions onto CeO2 NPs mitigated the surface reactivity of CeO2 NPs suggested by the FRAN and EPR assays. The impact of the ion adsorption on the surface reactivity of CeO2 NPs was related to the redox state of Ce and As on the surface, but varied with ion species and surface reaction mechanisms.
ContributorsBi, Xiangyu (Author) / Westerhoff, Paul K (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Herckes, Pierre (Committee member) / Richert, Ranko (Committee member) / Arizona State University (Publisher)
Created2018
Description
Rapid development of new technology has significantly disrupted the way radiotherapy is planned and delivered. These processes involve delivering high radiation doses to the target tumor while minimizing dose to the surrounding healthy tissue. However, with rapid implementation of these new technologies, there is a need for the detection of prescribed ionizing radiation for radioprotection of the patient and quality assurance of the technique employed. Most available clinical sensors are subjected to various limitations including requirement of extensive training, loss of readout with sequential measurements, sensitivity to light and post-irradiation wait time prior to analysis. Considering these disadvantages, there is still a need for a sensor that can be fabricated with ease and still operate effectively in predicting the delivered radiation dose.
The dissertation discusses the development of a sensor that changes color upon exposure to therapeutic levels of ionizing radiation used during routine radiotherapy. The underlying principle behind the sensor is based on the formation of gold nanoparticles from its colorless precursor salt solution upon exposure to ionizing radiation. Exposure to ionizing radiation generates free radicals which reduce ionic gold to its zerovalent gold form which further nucleate and mature into nanoparticles. The generation of these nanoparticles render a change in color from colorless to a maroon/pink depending on the intensity of incident ionizing radiation. The shade and the intensity of the color developed is used to quantitatively and qualitatively predict the prescribed radiation dose.
The dissertation further describes the applicability of sensor to detect a wide range of ionizing radiation including high energy photons, protons, electrons and emissions from radioactive isotopes while remaining insensitive to non-ionizing radiation. The sensor was further augmented with a capability to differentiate regions that are irradiated and non-irradiated in two dimensions. The dissertation further describes the ability of the sensor to predict dose deposition in all three dimensions. The efficacy of the sensor to predict the prescribed dose delivered to canine patients undergoing radiotherapy was also demonstrated. All these taken together demonstrate the potential of this technology to be translatable to the clinic to ensure patient safety during routine radiotherapy.
The dissertation discusses the development of a sensor that changes color upon exposure to therapeutic levels of ionizing radiation used during routine radiotherapy. The underlying principle behind the sensor is based on the formation of gold nanoparticles from its colorless precursor salt solution upon exposure to ionizing radiation. Exposure to ionizing radiation generates free radicals which reduce ionic gold to its zerovalent gold form which further nucleate and mature into nanoparticles. The generation of these nanoparticles render a change in color from colorless to a maroon/pink depending on the intensity of incident ionizing radiation. The shade and the intensity of the color developed is used to quantitatively and qualitatively predict the prescribed radiation dose.
The dissertation further describes the applicability of sensor to detect a wide range of ionizing radiation including high energy photons, protons, electrons and emissions from radioactive isotopes while remaining insensitive to non-ionizing radiation. The sensor was further augmented with a capability to differentiate regions that are irradiated and non-irradiated in two dimensions. The dissertation further describes the ability of the sensor to predict dose deposition in all three dimensions. The efficacy of the sensor to predict the prescribed dose delivered to canine patients undergoing radiotherapy was also demonstrated. All these taken together demonstrate the potential of this technology to be translatable to the clinic to ensure patient safety during routine radiotherapy.
ContributorsSubramaniam Pushpavanam, Karthik (Author) / Rege, Kaushal (Thesis advisor) / Sapareto, Stephen (Committee member) / Nannenga, Brent (Committee member) / Green, Matthew (Committee member) / Mu, Bin (Committee member) / Arizona State University (Publisher)
Created2019
Description
Gold nanoparticles are valuable for their distinct properties and nanotechnology applications. Because their properties are controlled in part by nanoparticle size, manipulation of synthesis method is vital, since the chosen synthesis method has a significant effect on nanoparticle size. By aiding mediating synthesis with proteins, unique nanoparticle structures can form, which open new possibilities for potential applications. Furthermore, protein-mediated synthesis favors conditions that are more environmentally and biologically friendly than traditional synthesis methods. Thus far, gold particles have been synthesized through mediation with jack bean urease (JBU) and para mercaptobenzoic acid (p-MBA). Nanoparticles synthesized with JBU were 80-90nm diameter in size, while those mediated by p-MBA were revealed by TEM to have a size between 1-3 nm, which was consistent with the expectation based on the black-red color of solution. Future trials will feature replacement of p-MBA by amino acids of similar structure, followed by peptides containing similarly structured amino acids.
ContributorsHathorn, Gregory Michael (Author) / Nannenga, Brent (Thesis director) / Green, Matthew (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Polymer-gold composite particles are of tremendous research interests. Contributed by their unique structures, these particles demonstrate superior properties for optical, catalytic and electrical applications. Moreover, the incorporation of “smart” polymers into polymer-gold composite particles enables the composite particles synergistically respond to environment-stimuli like temperature, pH and light with promising applications in multiple areas.
A novel Pickering emulsion polymerization route is found for synthesis of core-shell structured polymer-gold composite particles. It is found that the surface coverage of gold nanoparticles (AuNP) on a polystyrene core is influenced by gold nanoparticle concentration and hydrophobicity. More importantly, the absorption wavelength of polystyrene-gold composite particles is tunable by adjusting AuNP interparticle distance. Further, core-shell structured polystyrene-gold composite particles demonstrate excellent catalyst recyclability.
Asymmetric polystyrene-gold composite particles are successfully synthesized via seeded emulsion polymerization, where AuNPs serve as seeds, allowing the growth of styrene monomers/oligomers on them. These particles also demonstrate excellent catalyst recyclability. Further, monomers of “smart” polymers, poly (N-isopropylacrylamide) (PNIPAm), are successfully copolymerized into asymmetric composite particles, enabling these particles’ thermo-responsiveness with significant size variation around lower critical solution temperature (LCST) of 31°C. The significant size variation gives rise to switchable scattering intensity property, demonstrating potential applications in intensity-based optical sensing.
Multipetal and dumbbell structured gold-polystyrene composite particles are also successfully synthesized via seeded emulsion polymerization. It is intriguing to observe that by controlling reaction time and AuNP size, tetrapetal-structured, tripetal-structured and dumbbell-structured gold-polystyrene are obtained. Further, “smart” PNIPAm polymers are successfully copolymerized into dumbbell-shaped particles, showing significant size variation around LCST. Self-modulated catalytic activity around LCST is achieved for these particles. It is hypothesized that above LCST, the significant shrinkage of particles limits diffusion of reaction molecules to the surface of AuNPs, giving a reduced catalytic activity.
Finally, carbon black (CB) particles are successfully employed for synthesis of core- shell PNIPAm/polystyrene-CB particles. The thermo-responsive absorption characteristics of PNIPAm/polystyrene-CB particles enable them potentially suitable to serve as “smart” nanofluids with self-controlled temperature. Compared to AuNPs, CB particles provide desirable performance here, because they show no plasmon resonance in visible wavelength range, whereas AuNPs’ absorption in the visible wavelength range is undesirable.
A novel Pickering emulsion polymerization route is found for synthesis of core-shell structured polymer-gold composite particles. It is found that the surface coverage of gold nanoparticles (AuNP) on a polystyrene core is influenced by gold nanoparticle concentration and hydrophobicity. More importantly, the absorption wavelength of polystyrene-gold composite particles is tunable by adjusting AuNP interparticle distance. Further, core-shell structured polystyrene-gold composite particles demonstrate excellent catalyst recyclability.
Asymmetric polystyrene-gold composite particles are successfully synthesized via seeded emulsion polymerization, where AuNPs serve as seeds, allowing the growth of styrene monomers/oligomers on them. These particles also demonstrate excellent catalyst recyclability. Further, monomers of “smart” polymers, poly (N-isopropylacrylamide) (PNIPAm), are successfully copolymerized into asymmetric composite particles, enabling these particles’ thermo-responsiveness with significant size variation around lower critical solution temperature (LCST) of 31°C. The significant size variation gives rise to switchable scattering intensity property, demonstrating potential applications in intensity-based optical sensing.
Multipetal and dumbbell structured gold-polystyrene composite particles are also successfully synthesized via seeded emulsion polymerization. It is intriguing to observe that by controlling reaction time and AuNP size, tetrapetal-structured, tripetal-structured and dumbbell-structured gold-polystyrene are obtained. Further, “smart” PNIPAm polymers are successfully copolymerized into dumbbell-shaped particles, showing significant size variation around LCST. Self-modulated catalytic activity around LCST is achieved for these particles. It is hypothesized that above LCST, the significant shrinkage of particles limits diffusion of reaction molecules to the surface of AuNPs, giving a reduced catalytic activity.
Finally, carbon black (CB) particles are successfully employed for synthesis of core- shell PNIPAm/polystyrene-CB particles. The thermo-responsive absorption characteristics of PNIPAm/polystyrene-CB particles enable them potentially suitable to serve as “smart” nanofluids with self-controlled temperature. Compared to AuNPs, CB particles provide desirable performance here, because they show no plasmon resonance in visible wavelength range, whereas AuNPs’ absorption in the visible wavelength range is undesirable.
ContributorsZhang, Mingmeng (Author) / Dai, Lenore L (Committee member) / Phelan, Patrick E (Committee member) / Otanicar, Todd P (Committee member) / Lin, Jerry (Committee member) / He, Ximin (Committee member) / Arizona State University (Publisher)
Created2015
Description
A comprehensive and systematic investigation on the diffusion and phase behaviors of nanoparticles and macromolecules in two component liquid-liquid systems via Molecule Dynamic (MD) simulations is presented in this dissertation.
The interface of biphasic liquid systems has attracted great attention because it offers a simple, flexible, and highly reproducible template for the assembly of a variety of nanoscale objects. However, certain important fundamental issues at the interface have not been fully explored, especially when the size of the object is comparable with the liquid molecules. In the first MD simulation system, the diffusion and self-assembly of nanoparticles with different size, shape and surface composition were studied in an oil/water system. It has been found that a highly symmetrical nanoparticle with uniform surface (e.g. buckyball) can lead to a better-defined solvation shell which makes the “effective radius” of the nanoparticle larger than its own radius, and thus, lead to slower transport (diffusion) of the nanoparticles across the oil-water interface. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive polymer with a Lower Critical Solution Temperature (LCST) of 32°C in pure water. It is one of the most widely studied stimulus-responsive polymers which can be fabricated into various forms of smart materials. However, current understanding about the diffusive and phase behaviors of PNIPAM in ionic liquids/water system is very limited. Therefore, two biphasic water-ionic liquids (ILs) systems were created to investigate the interfacial behavior of PNIPAM in such unique liquid-liquid interface. It was found the phase preference of PNIPAM below/above its LCST is dependent on the nature of ionic liquids. This potentially allows us to manipulate the interfacial behavior of macromolecules by tuning the properties of ionic liquids and minimizing the need for expensive polymer functionalization. In addition, to seek a more comprehensive understanding of the effects of ionic liquids on the phase behavior of PNIPAM, PNIPAM was studied in two miscible ionic liquids/water systems. The thermodynamic origin causes the reduction of LCST of PNIPAM in imidazolium based ionic liquids/water system was found. Energy analysis, hydrogen boding calculation and detailed structural quantification were presented in this study to support the conclusions.
The interface of biphasic liquid systems has attracted great attention because it offers a simple, flexible, and highly reproducible template for the assembly of a variety of nanoscale objects. However, certain important fundamental issues at the interface have not been fully explored, especially when the size of the object is comparable with the liquid molecules. In the first MD simulation system, the diffusion and self-assembly of nanoparticles with different size, shape and surface composition were studied in an oil/water system. It has been found that a highly symmetrical nanoparticle with uniform surface (e.g. buckyball) can lead to a better-defined solvation shell which makes the “effective radius” of the nanoparticle larger than its own radius, and thus, lead to slower transport (diffusion) of the nanoparticles across the oil-water interface. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive polymer with a Lower Critical Solution Temperature (LCST) of 32°C in pure water. It is one of the most widely studied stimulus-responsive polymers which can be fabricated into various forms of smart materials. However, current understanding about the diffusive and phase behaviors of PNIPAM in ionic liquids/water system is very limited. Therefore, two biphasic water-ionic liquids (ILs) systems were created to investigate the interfacial behavior of PNIPAM in such unique liquid-liquid interface. It was found the phase preference of PNIPAM below/above its LCST is dependent on the nature of ionic liquids. This potentially allows us to manipulate the interfacial behavior of macromolecules by tuning the properties of ionic liquids and minimizing the need for expensive polymer functionalization. In addition, to seek a more comprehensive understanding of the effects of ionic liquids on the phase behavior of PNIPAM, PNIPAM was studied in two miscible ionic liquids/water systems. The thermodynamic origin causes the reduction of LCST of PNIPAM in imidazolium based ionic liquids/water system was found. Energy analysis, hydrogen boding calculation and detailed structural quantification were presented in this study to support the conclusions.
ContributorsGao, Wei (Author) / Dai, Lenore (Thesis advisor) / Jiao, Yang (Committee member) / Liu, Yongming (Committee member) / Green, Matthew (Committee member) / Emady, Heather (Committee member) / Arizona State University (Publisher)
Created2017