Matching Items (20)

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Development of Nanozymes from 2D Materials for Optical Detection of Neurotransmitters

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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

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.

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2019-05

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The Effect of Cu3Au Parent Phase Crystallography on Nanoporous Gold Morphology

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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

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.

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2019-05

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Composite Bricks from Fungus Mycelium and Nanomaterials for Sustainable Applications

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Plastics make up a large proportion of solid waste that ends up in landfills and pollute ecosystems, and do not readily decompose. Composites from fungus mycelium are a recent and promising alternative to replace plastics. Mycelium is the root-like fibers

Plastics make up a large proportion of solid waste that ends up in landfills and pollute ecosystems, and do not readily decompose. Composites from fungus mycelium are a recent and promising alternative to replace plastics. Mycelium is the root-like fibers from fungi that grow underground. When fed with woody biomass, the mycelium becomes a dense mass. From there, the mycelium is placed in mold to take its shape and grow. Once the growth process is done, the mycelium is baked to end the growth, thus making a mycelium brick. The woody biomass fed into the mycelium can include materials such as sawdust and pistachio shells, which are all cheap feedstock. In comparison to plastics, mycelium bricks are mostly biodegradable and eco-friendly. Mycelium bricks are resistant to water, fire, and mold and are also lightweight, sustainable, and affordable. Mycelium based materials are a viable option to replace less eco-friendly materials. This project aims to explore growth factors of mycelium and incorporate nanomaterials into mycelium bricks to achieve strong and sustainable materials, specifically for packaging materials. The purpose of integrating nanomaterials into mycelium bricks is to add further functionality such as conductivity, and to enhance properties such as mechanical strength.

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2019-05

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Selenium Removal with Nanotechnology-Enabled Water Treatment Using Conductive Copolymer Sorbents

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Heavy metals such as selenium can be especially important to limit because they can cause serious health problems even at relatively low concentrations. In an effort to selectively remove selenium from solution, a PAABA (poly(aniline-co-p-aminobenzoic acid) conductive copolymer was synthesized

Heavy metals such as selenium can be especially important to limit because they can cause serious health problems even at relatively low concentrations. In an effort to selectively remove selenium from solution, a PAABA (poly(aniline-co-p-aminobenzoic acid) conductive copolymer was synthesized in a selenic acid solution, and its ability to remove selenium was studied. Analysis of the Raman spectra confirmed the hypothesized formation of PAABA polymer. Constant voltage cycles showed success in precipitating the selenium out of solution via electroreduction, and ICP-MS confirmed the reduction of selenium concentrated in solution. These results indicate the PAABA synthesized in selenic acid shows promise for selective water treatment.

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2020-05

Nanotechnology Activity Videos

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Many nanotechnology-related principles can be demonstrated in a way that is understandable for elementary school-aged children through at-home activity videos. As a part of a National Science Foundation funded grant, Dr. Qing Hua Wang’s research group at Arizona State University

Many nanotechnology-related principles can be demonstrated in a way that is understandable for elementary school-aged children through at-home activity videos. As a part of a National Science Foundation funded grant, Dr. Qing Hua Wang’s research group at Arizona State University developed a nanotechnology-related activity website, Nano@Home, for students. In conjunction with ASU’s virtual Open Door 2021, this creative project aimed to create activity videos based on the Nano@Home website to make the activities more interactive for students.

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2021-05

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Carbon nanomaterials for energy storage, actuators and environmental applications

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Carbon nanomaterials have caught tremendous attention in the last few decades due to their unique physical and chemical properties. Tremendous effort has been made to develop new synthesis techniques for carbon nanomaterials and investigate their properties for different applications. In

Carbon nanomaterials have caught tremendous attention in the last few decades due to their unique physical and chemical properties. Tremendous effort has been made to develop new synthesis techniques for carbon nanomaterials and investigate their properties for different applications. In this work, carbon nanospheres (CNSs), carbon foams (CF), and single-walled carbon nanotubes (SWNTs) were studied for various applications, including water treatment, energy storage, actuators, and sensors.

A facile spray pyrolysis synthesis technique was developed to synthesize individual CNSs with specific surface area (SSA) up to 1106 m2/g. The hollow CNSs showed adsorption of up to 300 mg rhodamine B dye per gram carbon, which is more than 15 times higher than that observed for conventional carbon black. They were also evaluated as adsorbents for removal of arsenate and selenate from water and displayed good binding to both species, outperforming commercial activated carbons for arsenate removal in pH > 8. When evaluated as supercapacitor electrode materials, specific capacitances of up to 112 F/g at a current density of 0.1 A/g were observed. When used as Li-ion battery anode materials, the CNSs achieved a discharge capacity of 270 mAh/g at a current density of 372 mA/g (1C), which is 4-fold higher than that of commercial graphite anode.

Carbon foams were synthesized using direct pyrolysis and had SSA up to 2340 m2/g. When used as supercapacitor electrode materials, a specific capacitance up to 280 F/g was achieved at current density of 0.1 A/g and remained as high as 207 F/g, even at a high current density of 10 A/g.

A printed walking robot was made from common plastic films and coatings of SWNTs. The solid-state thermal bimorph actuators were multifunctional energy transducers powered by heat, light, or electricity. The actuators were also investigated for photo/thermal detection. Electrochemical actuators based on MnO2 were also studied for potential underwater applications.

SWNTs were also used to fabricate printable electrodes for trace Cr(VI) detection, which displayed sensitivity up to 500 nA/ppb for Cr(VI). The limit of detection was shown to be as low as 5 ppb. A flow detection system based on CNT/printed electrodes was also demonstrated.

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2015

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Liquid-phase exfoliation and applications of pristine two-dimensional transition metal dichalcogenides and metal diborides

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Ultrasonication-mediated liquid-phase exfoliation has emerged as an efficient method for producing large quantities of two-dimensional materials such as graphene, boron nitride, and transition metal dichalcogenides. This thesis explores the use of this process to produce a new class of boron-rich,

Ultrasonication-mediated liquid-phase exfoliation has emerged as an efficient method for producing large quantities of two-dimensional materials such as graphene, boron nitride, and transition metal dichalcogenides. This thesis explores the use of this process to produce a new class of boron-rich, two-dimensional materials, namely metal diborides, and investigate their properties using bulk and nanoscale characterization methods. Metal diborides are a class of structurally related materials that contain hexagonal sheets of boron separated by metal atoms with applications in superconductivity, composites, ultra-high temperature ceramics and catalysis. To demonstrate the utility of these materials, chromium diboride was incorporated in polyvinyl alcohol as a structural reinforcing agent. These composites not only showed mechanical strength greater than the polymer itself, but also demonstrated superior reinforcing capability to previously well-known two-dimensional materials. Understanding their dispersion behavior and identifying a range of efficient dispersing solvents is an important step in identifying the most effective processing methods for the metal diborides. This was accomplished by subjecting metal diborides to ultrasonication in more than thirty different organic solvents and calculating their surface energy and Hansen solubility parameters. This thesis also explores the production and covalent modification of pristine, unlithiated molybdenum disulfide using ultrasonication-mediated exfoliation and subsequent diazonium functionalization. This approach allows a variety of functional groups to be tethered on the surface of molybdenum disulfide while preserving its semiconducting properties. The diazonium chemistry is further exploited to attach fluorescent proteins on its surface making it amenable to future biological applications. Furthermore, a general approach for delivery of anticancer drugs using pristine two-dimensional materials is also detailed here. This can be achieved by using two-dimensional materials dispersed in a non-ionic and biocompatible polymer, as nanocarriers for delivering the anticancer drug doxorubicin. The potency of this supramolecular assembly for certain types of cancer cell lines can be improved by using folic-acid-conjugated polymer as a dispersing agent due to strong binding between folic acid present on the nanocarriers and folate receptors expressed on the cells. These results show that ultrasonication-mediated liquid-phase exfoliation is an effective method for facilitating the production and diverse application of pristine two-dimensional metal diborides and transition metal dichalcogenides.

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2018

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Artificial Enzymes from Hafnium Diboride Nanosheets Dispersed in Biocompatible Block Copolymers

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Nanomaterials that exhibit enzyme-like catalytic activity or nanozymes have many advantages compared to biological enzymes such as low cost of production and high stability. There is a substantial interest in studying two-dimensional materials due to their exceptional properties. Hafnium diboride

Nanomaterials that exhibit enzyme-like catalytic activity or nanozymes have many advantages compared to biological enzymes such as low cost of production and high stability. There is a substantial interest in studying two-dimensional materials due to their exceptional properties. Hafnium diboride is a type of two-dimensional material and belongs to the metal diborides family made of hexagonal layers of boron atoms separated by metal layers. In this work, the peroxidase-like activity of hafnium diboride nanoflakes dispersed in the block copolymer F77 was discovered for the first time. The kinetics, mechanisms and catalytic performance towards the oxidation of the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide are presented in this work. Kinetic parameters were determined by steady-state kinetics and a comparison with other nanozymes is given. Results show that the HfB2/F77 nanozyme possesses a unique combination of unusual high affinity towards hydrogen peroxide and high activity per cost. These findings are important for applications that involve reactions with hydrogen peroxide.

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2019

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Surface Treatment of Two-Dimensional Molybdenum Disulfide

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.

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.

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2018

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Surface interactions of layered chalcogenides in covalent functionalization and metal adsorption

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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,

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.

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2019