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- All Subjects: Chalcogenides
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Description
In this dissertation, three complex material systems including a novel class of hyperuniform composite materials, cellularized collagen gel and low melting point alloy (LMPA) composite are investigated, using statistical pattern characterization, stochastic microstructure reconstruction and micromechanical analysis. In Chapter 1, an introduction of this report is provided, in which a brief review is made about these three material systems. In Chapter 2, detailed discussion of the statistical morphological descriptors and a stochastic optimization approach for microstructure reconstruction is presented. In Chapter 3, the lattice particle method for micromechanical analysis of complex heterogeneous materials is introduced. In Chapter 4, a new class of hyperuniform heterogeneous material with superior mechanical properties is investigated. In Chapter 5, a bio-material system, i.e., cellularized collagen gel is modeled using correlation functions and stochastic reconstruction to study the collective dynamic behavior of the embed tumor cells. In chapter 6, LMPA soft robotic system is generated by generalizing the correlation functions and the rigidity tunability of this smart composite is discussed. In Chapter 7, a future work plan is presented.
ContributorsXu, Yaopengxiao (Author) / Jiao, Yang (Thesis advisor) / Liu, Yongming (Committee member) / Wang, Qing Hua (Committee member) / Ren, Yi (Committee member) / Arizona State University (Publisher)
Created2018
Description
Two-dimensional transition metal dichalcogenides (TMDCs) such as
molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2) are attractive for use in biotechnology, optical and electronics devices due to their promising and tunable electrical, optical and chemical properties. To fulfill the variety of requirements for different applications, chemical treatment methods are developed to tune their properties. In this dissertation, plasma treatment, chemical doping and functionalization methods have been applied to tune the properties of TMDCs. First, plasma treatment of TMDCs results in doping and generation of defects, as well as the synthesis of transition metal oxides (TMOs) with rolled layers that have increased surface-to-volume ratio and are promising for electrochemical applications. Second, chemical functionalization is another powerful approach for tuning the properties of TMDCs for use in many applications. To covalently functionalize the basal planes of TMDCs, previous reports begin with harsh treatments like lithium intercalation that disrupt the structure and lead to a phase transformation from semiconducting to metallic. Instead, this work demonstrates the direct covalent functionalization of semiconducting MoS2 using aryl diazonium salts without lithium treatments. It preserves the structure and semiconducting nature of MoS2, results in covalent C-S bonds on basal planes and enables different functional groups to be tethered to the MoS2 surface via the diazonium salts. The attachment of fluorescent proteins has been used as a demonstration and it suggests future applications in biology and biosensing. The effects of the covalent functionalization on the electronic transport properties of MoS2 were then studied using field effect transistor (FET) devices.
molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2) are attractive for use in biotechnology, optical and electronics devices due to their promising and tunable electrical, optical and chemical properties. To fulfill the variety of requirements for different applications, chemical treatment methods are developed to tune their properties. In this dissertation, plasma treatment, chemical doping and functionalization methods have been applied to tune the properties of TMDCs. First, plasma treatment of TMDCs results in doping and generation of defects, as well as the synthesis of transition metal oxides (TMOs) with rolled layers that have increased surface-to-volume ratio and are promising for electrochemical applications. Second, chemical functionalization is another powerful approach for tuning the properties of TMDCs for use in many applications. To covalently functionalize the basal planes of TMDCs, previous reports begin with harsh treatments like lithium intercalation that disrupt the structure and lead to a phase transformation from semiconducting to metallic. Instead, this work demonstrates the direct covalent functionalization of semiconducting MoS2 using aryl diazonium salts without lithium treatments. It preserves the structure and semiconducting nature of MoS2, results in covalent C-S bonds on basal planes and enables different functional groups to be tethered to the MoS2 surface via the diazonium salts. The attachment of fluorescent proteins has been used as a demonstration and it suggests future applications in biology and biosensing. The effects of the covalent functionalization on the electronic transport properties of MoS2 were then studied using field effect transistor (FET) devices.
ContributorsChu, Ximo (Author) / Wang, Qing Hua (Thesis advisor) / Sieradzki, Karl (Committee member) / Green, Alexander (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2018
Description
Flame retardants (FRs) are applied to variety of consumer products such as textiles and polymers for fire prevention and fire safety. Substantial research is ongoing to replace traditional FRs with alternative materials that are less toxic, present higher flame retardancy and result in lower overall exposure as there are potential health concerns in case of exposure to popular FRs. Carbonaceous nanomaterials (CNMs) such as carbon nanotubes (CNTs) and graphene oxide (GO) have been studied and applied to polymer composites and electronics extensively due to their remarkable properties. Hence CNMs are considered as potential alternative materials that present high flame retardancy. In this research, different kinds of CNMs coatings on polyester fabric are produced and evaluated for their use as flame retardants. To monitor the mass loading of CNMs coated on the fabric, a two-step analytical method for quantifying CNMs embedded in polymer composites was developed. This method consisted of polymer dissolution process using organic solvents followed by subsequent programmed thermal analysis (PTA). This quantification technique was applicable to CNTs with and without high metal impurities in a broad range of polymers. Various types of CNMs were coated on polyester fabric and the efficacy of coatings as flame retardant was evaluated. The oxygen content of CNMs emerged as a critical parameter impacting flame retardancy with higher oxygen content resulting in less FR efficacy. The most performant nanomaterials, multi-walled carbon nanotubes (MWCNTs) and amine functionalized multi-walled carbon nantoubes (NH2-MWCNT) showed similar FR properties to current flame retardants with low mass loading (0.18 g/m2) and hence are promising alternatives that warrant further investigation. Chemical/physical modification of MWCNTs was conducted to produce well-dispersed MWCNT solutions without involving oxygen for uniform FR coating. The MWCNTs coating was studied to evaluate the durability of the coating and the impact on the efficacy during use phase by conducting mechanical abrasion and washing test. Approximately 50% and 40% of MWCNTs were released from 1 set of mechanical abrasion and washing test respectively. The losses during simulated usage impacted the flame retardancy negatively.
ContributorsNosaka, Takayuki (Author) / Herckes, Pierre (Thesis advisor) / Westerhoff, Paul (Committee member) / Wang, Qing Hua (Committee member) / Arizona State University (Publisher)
Created2018
Description
Layered chalcogenides are a diverse class of crystalline materials that consist of covalently bound building blocks held together by van der Waals forces, including the transition metal dichalcogenides (TMDCs) and the pnictogen chalcogenides (PCs) among all. These materials, in particular, MoS2 which is the most widely studied TMDC material, have attracted significant attention in recent years due to their unique physical, electronic, optical, and chemical properties that depend on the number of layers. Due to their high aspect ratios and extreme thinness, 2D materials are sensitive to modifications via chemistry on their surfaces. For instance, covalent functionalization can be used to robustly modify the electronic properties of 2D materials, and can also be used to attach other materials or structures. Metal adsorption on the surfaces of 2D materials can also tune their electronic structures, and can be used as a strategy for removing metal contaminants from water. Thus, there are many opportunities for studying the fundamental surface interactions of 2D materials and in particular the TMDCs and PCs.
The work reported in this dissertation represents detailed fundamental studies of the covalent functionalization and metal adsorption behavior of layered chalcogenides, which are two significant aspects of the surface interactions of 2D materials. First, we demonstrate that both the Freundlich and Temkin isotherm models, and the pseudo-second-order reaction kinetics model are good descriptors of the reaction due to the energetically inhomogeneous surface MoS2 and the indirect adsorbate-adsorbate interactions from previously attached nitrophenyl (NP) groups. Second, the covalent functionalization using aryl diazonium salts is extended to nanosheets of other representative TMDC materials MoSe2, WS2, and WSe2, and of the representative PC materials Bi2S3 and Sb2S3, demonstrated using atomic force microscopy (AFM) imaging and Fourier transform infrared spectroscopy (FTIR). Finally, using AFM and X-ray photoelectron spectroscopy (XPS), it is shown that Pb, Cd Zn and Co form nanoclusters on the MoS2 surface without affecting the structure of the MoS2 itself. The metals can also be thermally desorbed from MoS2, thus suggesting a potential application as a reusable water purification technology.
The work reported in this dissertation represents detailed fundamental studies of the covalent functionalization and metal adsorption behavior of layered chalcogenides, which are two significant aspects of the surface interactions of 2D materials. First, we demonstrate that both the Freundlich and Temkin isotherm models, and the pseudo-second-order reaction kinetics model are good descriptors of the reaction due to the energetically inhomogeneous surface MoS2 and the indirect adsorbate-adsorbate interactions from previously attached nitrophenyl (NP) groups. Second, the covalent functionalization using aryl diazonium salts is extended to nanosheets of other representative TMDC materials MoSe2, WS2, and WSe2, and of the representative PC materials Bi2S3 and Sb2S3, demonstrated using atomic force microscopy (AFM) imaging and Fourier transform infrared spectroscopy (FTIR). Finally, using AFM and X-ray photoelectron spectroscopy (XPS), it is shown that Pb, Cd Zn and Co form nanoclusters on the MoS2 surface without affecting the structure of the MoS2 itself. The metals can also be thermally desorbed from MoS2, thus suggesting a potential application as a reusable water purification technology.
ContributorsLi, Duo, Ph.D (Author) / Wang, Qing Hua (Thesis advisor) / Green, Alexander A. (Committee member) / Chan, Candace K. (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2019
Description
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) like molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are effective components in optoelectronic devices due to their tunable and attractive electric, optical and chemical properties. Combining different 2D TMDCs into either vertical or lateral heterostructures has been pursued to achieve new optical and electronic properties. Chemical treatments have also been pursued to effectively tune the properties of 2D TMDCs. Among many chemical routes that have been studied, plasma treatment is notable for being rapid and versatile. In Wang’s group earlier work, plasma treatment of MoS2 and WS2 resulted in the formation of MoO3 and WO3 nanosheets and nanoscrolls. However, plasma treatment of 2D TMDC heterostructures have not been widely studied. In this dissertation, MoS2/WS2 vertical and lateral heterostructures were grown and treated with air plasma. The result showed that the vertical heterostructure and lateral heterostructures behaved differently. For the vertical heterostructures, the top WS2 layer acts as a shield for the underlying MoS2 monolayer from oxidizing and forming transition metal oxide nanoscrolls, as shown by Raman spectroscopy and atomic force microscopy (AFM). On the contrary, for the lateral heterostructures, the WS2 that was grown surrounding the MoS2 triangular core served as a tight frame to stop the propagation of the oxidized MoS2, resulting a gradient of crack distribution. These findings provide insight into how plasma treatment can affect the formation of oxide in heterostructure, which can have further application in nanoelectronic devices and electrocatalysts.
ContributorsChen, Mu-Tao (Author) / Wang, Qing Hua (Thesis advisor) / Green, Alexander (Committee member) / Yao, Yu (Committee member) / Arizona State University (Publisher)
Created2019
Description
In this research, the effect of the crystal structure of the parent phase on the morphology of nanoporous gold is explored. Specifically, Cu-Au alloys are studied. For this experiment, Cu0.75Au0.25 is heat treated to achieve an ordered phase Cu3Au and a disordered random solid solution, face centered cubic, Cu0.75Au0.25 phase, which are then dealloyed to form nanoporous gold (NPG). Using a morphology digital image analysis software called AQUAMI, SEM images of the NPG morphology were characterized to collect data on the ligament length, ligament diameter, porosity size, etc. of the samples. It was determined that the NPG formed from the ordered parent phase had an average ligament diameter that was 10 nm larger than the NPG formed from the disordered parent phase. This may be due to the ordered crystal structure allowing for faster gold diffusion and coarsening resulting in an increased average ligament size. Further future work is needed in order to obtain further evidence to support this hypothesis.
ContributorsTse, Ariana Yusof (Author) / Sieradzki, Karl (Thesis director) / Wang, Qing Hua (Committee member) / Materials Science and Engineering Program (Contributor) / Walter Cronkite School of Journalism & Mass Comm (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
This paper discusses the possibility of utilizing 2D molybdenum disulfide (MoS2) as a nanozyme to detect dopamine colorimetric assays, first by detecting color change in liquid solutions due to oxidation and then second on paper-based assays. MoS2 samples dispersed in methylcellulose (MC) solution were prepared using liquid-phase exfoliation through sonication. The dopamine (DOPA) and hydrogen peroxide (H¬¬2O2) solutions were prepared separately in specific concentrations. The solutions were mixed in a well plate and colorimetric results were analyzed by a plate reader, revealing a quantitative relationship between dopamine concentration and absorbance. Subsequent testing was conducted using paper assays, where combined solutions of DOPA and H2O2 were dropped onto paper with printed wax wells that contained dried MoS2. An analysis of the color change was conducted using a smartphone application called Color Grab to detect the red, green, and blue (RGB) values. Plotting the RGB results across the dopamine concentrations revealed a positively correlated relationship between the two factors, suggesting that a predictive model could be developed to predict dopamine concentrations based on measured colorimetric values.
ContributorsNalla, Akshay (Co-author, Co-author) / Wang, Qing Hua (Thesis director) / Green, Alexander (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05