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Full-Text Articles in Nanoscience and Nanotechnology

Photoinduced Hole Transfer And Recombination Dynamics Of A Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst, Orion Magruder Pearce Jan 2019

Photoinduced Hole Transfer And Recombination Dynamics Of A Cds Quantum Dot Sensitized Mononuclear Water Oxidation Catalyst, Orion Magruder Pearce

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Artificial photosynthesis represents a promising strategy to capture and store solar energy through the production of carbon neutral fuels. This process begins with absorption of a photon by a semiconductor creating an electron-hole pair which are then separated and used to drive reduction and oxidation reactions. CdS nanostructures are model light absorbers for studying these charge transfer reactions and have already demonstrated photoinduced electron transfer to drive a variety of reactions. However, there has been comparatively little progress in understanding how CdS nanostructures may be used to sensitize oxidation reactions such as water oxidation. To this end, we undertook a ...


Designing Materials For Inorganic And Living Photocatalytic Systems For Air, Water, And Co2 Reduction From Sunlight, Yuchen Ding Jan 2018

Designing Materials For Inorganic And Living Photocatalytic Systems For Air, Water, And Co2 Reduction From Sunlight, Yuchen Ding

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Several strategies are currently being investigated for conversion of incident sunlight into chemical fuels, with readily available chemical feedstocks like air, water, and carbon-dioxide. This thesis focuses on research approach on designing high-efficiency and high-selective photocatalytic materials, ranging from inexpensive and stable inorganic photocatalysts to living nano-biohybrid organisms to achieve solar energy conversion.

This thesis is divided into multiple sections based on the materials and concepts in designing high-efficient and high-selective solar fuel generator. After a brief introduction of photocatalysis in Chapter 1, we describe a novel electrochemical anodization technique for making a wide-variety of doped metal-oxide nanotubes. Using optoelectronic ...


Excited-State Dynamics Of Semiconductor Nanocrystals: Trapped-Hole Diffusion And Electron-Transfer Kinetics In Cds And Cdse Nanorods, James Keller Utterback Jan 2018

Excited-State Dynamics Of Semiconductor Nanocrystals: Trapped-Hole Diffusion And Electron-Transfer Kinetics In Cds And Cdse Nanorods, James Keller Utterback

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Colloidal semiconductor nanocrystals have many remarkable properties—such as exceptionally tunable excited states and surface chemistry—that have led to an enthusiastic interest in using them for optoelectronic applications such as solar-energy conversion. Such technologies require control over the generation, separation, and extraction of photoexcited electrons and holes. However, the interpretation of experimentally measured excited-state decay curves is challenging because they typically exhibit complicated shapes that are elusive to simple kinetic models. To understand the principles that govern electron and hole relaxation dynamics in these complex systems, models rooted in fundamental physical phenomena are needed. This dissertation describes efforts to ...


Using Semiconductor Nanocrystals To Drive Redox Enzymes With Light, Hayden Tyler Hamby Jan 2018

Using Semiconductor Nanocrystals To Drive Redox Enzymes With Light, Hayden Tyler Hamby

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Nanocrystals are an emergent strategy for providing electrons to redox enzymes for catalysis. In this dissertation I present my work on the investigation of how nanocrystals can be used to drive active site chemistry of two different enzymes. In the first project I present for the first time the direct coupling of cadmium sulfide nanorods (CdS NRs) to a CO2 reduction enzyme for the creation of new carbon-carbon bonds using light. Under optimal conditions, the maximum turnover frequency (TOFmax) for CO2 reduction is similar to that obtained in the native system where the native electron donor ferredoxin ...


Controlling The Photophysical Properties Of Semiconductor Quantum Dot Arrays By Strategic Alteration Of Their Surface Chemistry, Ashley R. Marshall Jan 2017

Controlling The Photophysical Properties Of Semiconductor Quantum Dot Arrays By Strategic Alteration Of Their Surface Chemistry, Ashley R. Marshall

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Semiconductor quantum dots (QDs) are interesting materials that, after less than 40 years of research, are used in commercial products. QDs are now found in displays, such as Samsung televisions and the Kindle Fire, and have applications in lighting, bio-imaging, quantum computing, and photovoltaics. They offer a large range of desirable properties: a controllable band gap, solution processability, controlled energy levels, and are currently the best materials for multiple exciton generation. The tunable optoelectronic properties of QDs can be controlled using size, shape, composition, and surface treatments—as shown here. Due to the quasi-spherical shape of QDs the surface to ...


Photophysics And Electron Transfer Dynamics Of Type-Ii And Quasi Type-Ii Heterostructure Nanocrystals, Amanda Norell Grennell Jan 2017

Photophysics And Electron Transfer Dynamics Of Type-Ii And Quasi Type-Ii Heterostructure Nanocrystals, Amanda Norell Grennell

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of ...


Photophysics And Electron Transfer Dynamics Of Type-Ii And Quasi Type-Ii Heterostructure Nanocrystals, Amanda N. Grennell Jan 2017

Photophysics And Electron Transfer Dynamics Of Type-Ii And Quasi Type-Ii Heterostructure Nanocrystals, Amanda N. Grennell

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of ...


Simulation Studies Of Diblock-Copolymer Grafted Nanoparticle Assembly In Solvent And Polymer Matrix, Carla E. Estridge Jan 2015

Simulation Studies Of Diblock-Copolymer Grafted Nanoparticle Assembly In Solvent And Polymer Matrix, Carla E. Estridge

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Macroscopic properties of polymer nanocomposites are fundamentally linked to the morphology (or assembled structure) of its constituents. In order to design composites to have specific macroscopic properties it is important to be able to control the assembly of the constituents in the composite. In this thesis we use molecular simulations to study the molecular-level interactions and assembly of one class of polymer nanocomposites, namely diblock-copolymer grafted nanoparticles in solvent and in polymer matrix.

First, we study how the molecular features of the diblock-copolymer grafts affect the assembly of grafted nanoparticles in a (implicit) small molecule solvent. Using coarse-grained molecular dynamics ...


Charge Transfer Dynamics In Complexes Of Light-Absorbing Cds Nanorods And Redox Catalysts, Molly Bea Wilker Jan 2015

Charge Transfer Dynamics In Complexes Of Light-Absorbing Cds Nanorods And Redox Catalysts, Molly Bea Wilker

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This dissertation describes research efforts to understand the photoexcited charge transfer kinetics in complexes of colloidal CdS nanorods coupled with either a water oxidation or reduction catalyst. The first project focuses on the charge transfer interactions between photoexcited CdS nanorods and a mononuclear water oxidation catalyst derived from the [Ru(bpy)(tpy)Cl]+ parent structure. Upon excitation, hole transfer from CdS oxidizes the catalyst (Ru2+→Ru3+) on a 100 ps – 1 ...


Interactions Of Nanomaterials With Biological Systems: A Study Of Bio-Mineralized Nanoparticles And Nanoparticle Antibiotics, Jennifer Chappell Gifford Jan 2015

Interactions Of Nanomaterials With Biological Systems: A Study Of Bio-Mineralized Nanoparticles And Nanoparticle Antibiotics, Jennifer Chappell Gifford

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Nature is continually able to out-perform laboratory syntheses of nanomaterials with control of specific properties under ambient temperatures, pressures and pH. The investigation of existing biomolecule-mediated nanoparticle synthesis provides insight and knowledge necessary for duplicating these processes. In this way, peptides or proteins with nanomaterial mediation capabilities can be: 1) explored to further understand the ways in which biomolecules create specific nanoparticles then 2) used to create genetically encodable tags for use in electron tomography. The goal of designing such a tag was to assist in closing the resolution gap that exists in current imaging techniques between approximately 5 nm ...


Self-Assembled Nanostructures In Block Copolymer Thin Films For Nanofabrication, Chunlin He Jan 2014

Self-Assembled Nanostructures In Block Copolymer Thin Films For Nanofabrication, Chunlin He

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Self-assembly of block copolymer in thin films provides an attractive approach to fabricating nanoscale dots and lines (5~100 nm) rapidly and in parallel over wafer-scale areas. This PhD dissertation mainly studies using the cross-linking reaction based on epoxide incorporated in copolymers to control the nanostructures of self-assembled block copolymer in thin films.

Although control over the domain orientation and long-range order of block copolymer nanostructures self-assembled in thin films has been achieved using various directed self-assembly techniques, more challenging but equally important for many lithographic applications is the ability to precisely control the shape of the interface between domains ...


Synthesis And Functionalization Of Gold Nanoparticles Using Chemically Modified Ssdna, Philip Gerard Calabrese Jan 2014

Synthesis And Functionalization Of Gold Nanoparticles Using Chemically Modified Ssdna, Philip Gerard Calabrese

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

In the first part of this thesis, methods for functionalizing spherical gold nanoparticles with nucleic acid binding ligands (aptamers) that target the VEGF receptor complex were developed. In order to provide a multiplexed labeling strategy for imaging the VEGF receptor complex in electron microscopy, gold nanoparticles of distinct sizes were conjugated to modified ssDNA aptamers that target the VEGF-A cytokine, the VEGFR-2 RTK receptor and a membrane associated co-receptor, Nrp-1. The modified ssDNA gold nanoparticle conjugates were applied to a human lung carcinoma cell line (A549) which has been shown to express each of these proteins and used as a ...


Rna Mediated Assembly Of Nanostructures, Jessica Lynn Rouge Jan 2012

Rna Mediated Assembly Of Nanostructures, Jessica Lynn Rouge

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

The first chapter of this work presents a comprehensive look at RNA mediated nanoparticle formation. The overall goal of this research is to gain a deeper understanding of the RNA-particle formation mechanism and the basic properties of the materials selected by modified RNA molecules. Understanding such RNA-substrate interactions and how they translate into the physical and chemical characteristics of the nanoparticles they create are important fundamental concepts when considering these biotemplated materials as potential chemical catalysts. The RNA sequences discussed in the first chapter (referred to as Pdases) were discovered using RNA in vitro selection techniques. These Pdases were found ...


Ultrafast Optical Studies Of Multiple Exciton Generation In Lead Chalcogenide Quantum Dots, Aaron G. Midgett Jan 2011

Ultrafast Optical Studies Of Multiple Exciton Generation In Lead Chalcogenide Quantum Dots, Aaron G. Midgett

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy conversion. Present day, first and second-generation solar cells can at most convert each absorbed photon into a single electron hole pair, thereby establishing a theoretical limit to the power conversion efficiency. The process of multiple exciton generation (MEG) in semiconductor quantum dots increases that theoretical efficiency from 33% to 42% by utilizing the excess energy of high energy photons that is otherwise wasted as heat to excite a second electron-hole pair, thereby boosting the potential photocurrent ...