Physical Sciences and Mathematics Commons^™

Air-Oxidation Of Phenolic Resin Aerogels: Backbone Reorganization, Formation Of Ring-Fused Pyrylium Cations, And The Effect On Microporous Carbons With Enhanced Surface Areas, Hojat Majedi Far, Suraj Donthula, Tahereh Taghvaee, Adnan Malik Saeed, Zachary Garr, Chariklia Sotiriou-Leventis, Nicholas Leventis

Chemistry Faculty Research & Creative Works

This paper is a thorough investigation of the chemical transformations during pyrolytic conversion of phenolic resins to carbons, and reports that all carbons obtained from main-stream phenolic resins including phloroglucinol-formaldehyde (FPOL), phloroglucinol-terephthalaldehyde (TPOL), resorcinol-formaldehyde (RF), and phenol-formaldehyde (PF) contain fused pyrylium rings and charge-compensating phenoxides. Those four phenolic resins were prepared via a fast HCl-catalyzed process as low-density nanostructured solids classified as aerogels, which, owing to their open porosity, allowed air circulation through their bulk. In that regard, the first step of this study was the air-oxidation of those phenolic resin aerogels at 240 °C. In FPOL and TPOL aerogels, …

Middle Miocene Paleoenvironmental Reconstruction Of The Central Great Plains From Stable Carbon Isotopes In Large Mammals, Willow H. Nguy

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Middle Miocene (18-12 Mya) mammalian faunas of the North American Great Plains contained a much higher diversity of apparent browsers than any modern biome. This has been attributed to greater primary productivity, which may have supported greater browser diversity that commonly corresponds with densely vegetated habitats. However, several lines of proxy evidence suggest that open woodlands or savannas dominated middle Miocene biomes; neither of which support many browsers today. Stable carbon isotopes in mammalian herbivore tooth enamel were used to reconstruct vegetation structure of middle Miocene biomes.

Stable carbon isotopes in C₃ dominated environments reflect vegetation density and herbivores …

Embodied Carbon: A Framework For Prioritizing And Reducing Emissions In The Building Industry, Natalie C. Wheating

Master's Projects and Capstones

Global climate change is one of the most impactful environmental issues in modern times, and the construction industry is known to be one of the largest contributors to carbon emissions—one of the key causes of climate change. Embodied carbon emissions of buildings are an often overlooked, but significant, influencer of a building’s overall carbon footprint. This gives rise to the need for improved life cycle analysis of buildings and identification of opportunities to reduce the total carbon footprint of a building throughout its life cycle. This paper analyzes the current state of the building industry that limits the consideration of …

Analysis Of Carbon And Nitrogen Stable Isotope Levels In Side-Blotched Lizards ( Uta Stansburiana ) Fed Varying Diets, Kati Mattinson

Physics Capstone Projects

When attempting to determine the diet of wild animals, a limited number of techniques currently exist. Often, biologists look at the stomach contents or feces of an animal, if they cannot observe what it is eating directly. However, these techniques often cannot be used with reptiles because they may not eat often or may have an empty stomach when the contents of their stomach are examined. Many ecologists have begun to use stable isotopes of carbon and nitrogen to determine what an animal has eaten. Stable isotopes are useful because unlike radioactive isotopes, stable isotopes do not decay and thus …

Molecular And Optical Properties Of Tree-Derived Dissolved Organic Matter In Throughfall And Stemflow From Live Oaks And Eastern Red Cedar, Aron Stubbins, Leticia M. Silva, Thorsten Dittmar, John T. Van Stan

School of Earth, Environment, and Sustainability Faculty Publications

Studies of dissolved organic matter (DOM) transport through terrestrial aquatic systems usually start at the stream. However, the interception of rainwater by vegetation marks the beginning of the terrestrial hydrological cycle making trees the headwaters of aquatic carbon cycling. Rainwater interacts with trees picking up tree-DOM, which is then exported from the tree in stemflow and throughfall. Stemflow denotes water flowing down the tree trunk, while throughfall is the water that drips through the leaves of the canopy. We report the concentrations, optical properties (light absorbance) and molecular signatures (ultrahigh resolution mass spectrometry) of tree-DOM in throughfall and stemflow from …

Nutrient And Phytoplankton Dynamics On The Inner Shelf Of The Eastern Bering Sea, Calvin W. Mordy, Allan H. (Allan Houston) Devol, Lisa B. Eisner, Nancy Kachel, Carol A. Ladd, Michael W. Lomas, Peter Proctor, Raymond Nicholas Sambrotto, David Shull, Phyllis Jean Stabeno, Eric Wisegarver

Environmental Sciences Faculty and Staff Publications

In the Bering Sea, the nitrogen cycle near Nunivak Island is complicated due to limited nutrient replenishment across this broad shelf, and substantial nitrogen loss through sedimentary processes. While diffusion at the inner front may periodically support new production, the inner shelf in this region is generally described as a regenerative system. This study combines hydrographic surveys with measurements of nitrogen assimilation and benthic fluxes to examine nitrogen cycling on the inner shelf, and connectivity between the middle and inner shelves of the southern and central Bering Sea. Results establish the inner shelf as primarily a regenerative system even in …

Carbon Sequestration By Australian Tidal Marshes, Peter I. Macreadie, Q. R. Oliver, J. J. Kelleway, Oscar Serrano, P. E. Carnell, C. J. Ewers Lewis, T. B. Atwood, J. Sanderman, J. Baldock, R. M. Connolly, C. M. Duarte, Paul Lavery, A. Steven, C. E, Lovelock

Research outputs 2014 to 2021

Australia’s tidal marshes have suffered significant losses but their recently recognised importance in CO2 sequestration is creating opportunities for their protection and restoration. We compiled all available data on soil organic carbon (OC) storage in Australia’s tidal marshes (323 cores). OC stocks in the surface 1 m averaged 165.41 (SE 6.96) Mg OC ha − 1 (range 14 – 963 Mg OC ha − 1). The mean OC accumulation rate was 0.55 ± 0.02 Mg OC ha − 1 yr − 1. Geomorphology was the most important predictor of OC stocks, with fluvial sites having twice the stock of OC …

Preparation And Electrochemical Properties Of Attapulgite-Supported Nitrogen-Doped Carbon@Nico2O4Composites For Supercapacitors, Hui Wan, Zong-Rong Ying, Xin-Dong Liu, Jian-Jian Lu, Wen-Wen Zhang

Journal of Electrochemistry

In this work, the attapulgite-supported nitrogen-doped carbon (ANC) was prepared by in-situ chemically polymerizing polyaniline coating upon attapulgite, followed by high temperature heat treatment, and then NiCo₂O₄was reacted onto the surface of ANC by a combination of hydrothermal reaction and calcination to synthesize ANC@NiCo₂O₄ composites. The chemical composition and morphology of the samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ adsorption/desorption. The electrochemical properties were evaluated by means of constant current charge discharge (GCD) and cyclic voltammetry (CV). …

Probe Sensor Using Nanostructured Multi-Walled Carbon Nanotube Yarn For Selective And Sensitive Detection Of Dopamine, Wed Al-Graiti, Zhilian Yue, Javad Foroughi, Xu-Feng Huang, Gordon G. Wallace, Ray H. Baughman, Jun Chen

Australian Institute for Innovative Materials - Papers

The demands for electrochemical sensor materials with high strength and durability in physiological conditions continue to grow and novel approaches are being enabled by the advent of new electromaterials and novel fabrication technologies. Herein, we demonstrate a probe-style electrochemical sensor using highly flexible and conductive multi-walled carbon nanotubes (MWNT) yarns. The MWNT yarn-based sensors can be fabricated onto micro Pt-wire with a controlled diameter varying from 100 to 300 µm, and then further modified with Nafion via a dip-coating approach. The fabricated micro-sized sensors were characterized by electron microscopy, Raman, FTIR, electrical, and electrochemical measurements. For the first time, the …

Hollow Carbon Nanobubbles: Monocrystalline Mof Nanobubbles And Their Pyrolysis, Wei Zhang, Xiangfen Jiang, Yanyi Zhao, Arnau Carne-Sanchez, Victor Malgras, Jeonghun Kim, Jung Ho Kim, Shaobin Wang, Jian Liu, Ji-Sen Jiang, Yusuke Yamauchi, Ming Hu

Australian Institute for Innovative Materials - Papers

While bulk-sized metal-organic frameworks (MOFs) face limits to their utilization in various research fields such as energy storage applications, nanoarchitectonics is believed to be a possible solution. It is highly challenging to realize MOF nanobubbles with monocrystalline frameworks. By a spatially controlled etching approach, here, we can achieve the synthesis of zeolitic imidazolate framework (ZIF-8) nanobubbles with a uniform size of less than 100 nm. Interestingly, the ZIF-8 nanobubbles possess a monocrystalline nanoshell with a thickness of around 10 nm. Under optimal pyrolytic conditions, the ZIF-8 nanobubbles can be converted into hollow carbon nanobubbles while keeping their original shapes. The …

Flexible Polycaprolactone (Pcl) Supercapacitor Based On Reduced Graphene Oxide (Rgo)/Single-Wall Carbon Nanotubes (Swnts) Composite Electrodes, Hyeon Taek Jeong, Yong-Ryeol Kim, Byung Chul Kim

Australian Institute for Innovative Materials - Papers

The reduced graphene oxide (rGO)/single-wall carbon nanotubes (SWNTs) composites are coated onto the polycaprolactone (PCL) substrate via spray coating technique to prepare a flexible supercapacitor. The electrochemical properties of the flexible PCL supercapacitor as a function of bending cycles and angles are evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. The EIS and charge/discharge curves of the flexible PCL supercapacitor exhibit capacitive behavior even after prolonged bending cycles up to 500. The highest capacitance value of the unbent PCL supercapacitor is 52.5 F g-1 which retained 65% after 500 bending with 6000th galvanostatic charge/discharge cycles.

Capillary-Induced Ge Uniformly Distributed In N-Doped Carbon Nanotubes With Enhanced Li-Storage Performance, Haipeng Guo, Boyang Ruan, Lili Liu, Lei Zhang, Zhanliang Tao, Shulei Chou, Jiazhao Wang, Hua-Kun Liu

Australian Institute for Innovative Materials - Papers

Germanium (Ge) is a prospective anode material for lithium-ion batteries, as it possesses large theoretical capacity, outstanding lithium-ion diffusivity, and excellent electrical conductivity. Ge suffers from drastic capacity decay and poor rate performance, however, owing to its low electrical conductivity and huge volume expansion during cycling processes. Herein, a novel strategy has been developed to synthesize a Ge at N-doped carbon nanotubes (Ge at N-CNTs) composite with Ge nanoparticles uniformly distributed in the N-CNTs by using capillary action. This unique structure could effectively buffer large volume expansion. When evaluated as an anode material, the Ge at N-CNTs demonstrate enhanced cycling …

Temporal Variability Of Fluorescent Dissolved Organic Matter At A Brackish, Tidal Marsh-Estuary Interface, Alana B. Menendez

Dissertations and Theses

Marshes are both terrestrial and aqueous, sitting as an intermediate between land and water. Studies over constrained numbers of tidal cycles have demonstrated that these marshes are net exporters of dissolved organic carbon (DOC) to adjoining estuaries, however, there is need for continuous monitoring to better understand the temporal variability of this flux: tidally, seasonally, and during episodic rain events. Through use of a YSI EXO2 sonde, an in situ optical sensor at the interface of the brackish, tidal Kirkpatrick Marsh and Rhode River sub-estuary in Edgewater, Maryland (located on the northwestern shore of the Chesapeake Bay), we were able …

Eukaryotic Microbes, Principally Fungi And Labyrinthulomycetes, Dominate Biomass On Bathypelagic Marine Snow, Alexander B. Bochdansky, Melissa A. Clouse, Gerhard J. Herndl

OES Faculty Publications

In the bathypelagic realm of the ocean, the role of marine snow as a carbon and energy source for the deep-sea biota and as a potential hotspot of microbial diversity and activity has not received adequate attention. Here, we collected bathypelagic marine snow by gentle gravity filtration of sea water onto μm filters from similar to 1000 to 3900 m to investigate the relative distribution of eukaryotic microbes. Compared with sediment traps that select for fast-sinking particles, this method collects particles unbiased by settling velocity. While prokaryotes numerically exceeded eukaryotes on marine snow, eukaryotic microbes belonging to two very distant …

Marsh-Exported Dissolved Organic Matter Fate In Estuaries, Laura Ann Logozzo

Dissertations and Theses

Dissolved organic matter (DOM) is a significant driver of estuarine productivity and nutrient cycling. The colored component of DOM, chromophoric dissolved organic matter (CDOM), impacts coastal optical properties, ocean color, and light attenuation. While marshes are largely considered sinks for carbon due to their high productivity and low soil carbon degradation rates, laterally they are sources of carbon as optically and chemically distinct DOM to surrounding aquatic ecosystems; these inputs are often essential in sustaining a net heterotrophic system. However, the photoreactivity and bioavailability of marsh-exported DOM is largely uncategorized, thus making it difficult to quantify its impacts on estuarine …

Climate Change, Spruce Root Phenology, And Allocation Of Carbon Below- And Above-Ground, Marie Louise Orton

Legacy Theses & Dissertations (2009 - 2024)

Tree ring analysis has relied on a close relationship between climate and photosynthetically-derived stem enlargement. Lengthening growing seasons associated with climate warming have been predicted to enhance carbon sequestration as wood in trees, but this

Iron Reduction In Soot, Hector Casique

All Master's Theses

Ferrous iron (Fe(II)) has been implicated as one contributor in the generation of reactive oxygen species (ROS) from ambient particles emitted during the incomplete combustion of fossil and biomass fuels. Although ROS are known to induce unhealthy oxidative stress in cellular systems, the mechanisms of Fe(II) formation and stabilization in aerosol particles are still not well understood. Here, we investigate the role of soot on Iron reduction from Fe(III) to Fe(II), under various conditions including those encountered in the tailpipe of a vehicle. Aqueous leaching experiments of soot-hematite mixtures were carried out while analyzing for Fe(II) spectrophotometrically, and changes in …

Photoluminescence Mechanism And Applications Of Graphene Quantum Dots, Yiyang Liu

Theses and Dissertations--Chemistry

Graphene quantum dots (GQDs) are small pieces of graphene oxide whose physical dimensions are so confined (a few to a few tens nm) that they have a finite bandgap due to a quantum confinement effect. The finite bandgap of GQDs grants them pronounced absorption bands and a substantial photoluminescence. These optical properties are rarely observed in traditional carbon materials, since most of carbon materials are metallic with a near-zero bandgap and thus have broad absorption spectra with no photoluminescence. The unique optical properties of GQDs, along with GQDs’ inherited advantages from carbon material family (cheap, abundant, non-toxic), make GQDs an …