Computational Study of CO2 Adsorption and Reduction on Doped Graphene Sheets

In recent decades, growing CO2 in the Earth\u27s atmosphere has become a major issue. Thus, it is crucial to reduce the level of concentration of CO2 in the atmosphere. We have investigated the adsorption and reduction of CO2 on metal-doped graphene sheets, through computational methods. The electrochemical reduction of CO2 to CO, CH3OH and CH4 were calculated. Co-doped graphene sheet shows very promising catalytic behavior for CO2 reduction with the highest elemental reaction energy less than 0.7 eV. In addition, tThe reaction pathways reveal the possible rate limiting step could be the removal of the second H2O, CH3OH or CH4 from the doped graphene sheet, depending upon the type of dopant in graphene

Computational Study of the Electronic Structure of Various Cobalt (Hydroxy) Oxides in Electrolysis Reactions

In their electrolysis reaction to produce H 2 fuel, the Solar Thermal Decoupled Electrolysis group at Valparaiso University observed increased reaction rate as time goes on and proposed that the deposited products on the Ni anode might be conductive and acting as a new electrode surface. It is of great interest to gain a better understanding of the underlying mechanism. In this study, the structure and stability of various cobalt (hydroxy)oxide species on a Ni (111) surface were determined from first-principles calculations to see if the observations made by the Solar Thermal Decoupled Electrolysis group are consistent with theoretical results and what could be responsible for the extended conductive electrode. From the known bulk crystal structures of various cobalt (hydroxy)oxide species, mono-layers of each of these materials were constructed. These monolayers were then placed on a Ni (111) metal support and optimal configurations of the combined systems were determined. The electronic structure of the cobalt (hydroxy) oxide monolayers and bulks will be reported

Electron transport in molecular systems

The remarkable advances in nanoscience and nanotechnology over the last two decades allow one to manipulate individuals atoms, molecules and nanostructures, make it possible to build devices with only a few nanometers, and enhance the nano-bio fusion in tackling biological and medical problems. It complies with the ever-increasing need for device miniaturization, from magnetic storage devices, electronic building blocks for computers, to chemical and biological sensors. Despite the continuing efforts based on conventional methods, they are likely to reach the fundamental limit of miniaturization in the next decade, when feature lengths shrink below 100 nm. On the one hand, quantum mechanical efforts of the underlying material structure dominate device characteristics. On the other hand, one faces the technical difficulty in fabricating uniform devices. This has posed a great challenge for both the scientific and the technical communities. The proposal of using a single or a few organic molecules in electronic devices has not only opened an alternative way of miniaturization in electronics, but also brought up brand-new concepts and physical working mechanisms in electronic devices. This thesis work stands as one of the efforts in understanding and building of electronic functional units at the molecular and atomic levels. We have explored the possibility of having molecules working in a wide spectrum of electronic devices, ranging from molecular wires, spin valves/switches, diodes, transistors, and sensors. More specifically, we have observed significant magnetoresistive effect in a spin-valve structure where the non-magnetic spacer sandwiched between two magnetic conducting materials is replaced by a self-assembled monolayer of organic molecules or a single molecule (like a carbon fullerene). The diode behavior in donor(D)-bridge(B)-acceptor(A) type of single molecules is then discussed and a unimolecular transistor is designed. Lastly, we have proposed and primarily tested the idea of using functionalized electrodes for rapid nanopore DNA sequencing. In these studies, the fundamental roles of molecules and molecule-electrode interfaces on quantum electron transport have been investigated based on first-principles calculations of the electronic structure. Both the intrinsic properties of molecules themselves and the detailed interfacial features are found to play critical roles in electron transport at the molecular scale. The flexibility and tailorability of the properties of molecules have opened great opportunity in a purpose-driven design of electronic devices from the bottom up. The results that we gained from this work have helped in understanding the underlying physics, developing the fundamental mechanism and providing guidance for future experimental efforts

Functionalized nanopore-embedded electrodes for rapid DNA sequencing

The determination of a patient's DNA sequence can, in principle, reveal an increased risk to fall ill with particular diseases [1,2] and help to design "personalized medicine" [3]. Moreover, statistical studies and comparison of genomes [4] of a large number of individuals are crucial for the analysis of mutations [5] and hereditary diseases, paving the way to preventive medicine [6]. DNA sequencing is, however, currently still a vastly time-consuming and very expensive task [4], consisting of pre-processing steps, the actual sequencing using the Sanger method, and post-processing in the form of data analysis [7]. Here we propose a new approach that relies on functionalized nanopore-embedded electrodes to achieve an unambiguous distinction of the four nucleic acid bases in the DNA sequencing process. This represents a significant improvement over previously studied designs [8,9] which cannot reliably distinguish all four bases of DNA. The transport properties of the setup investigated by us, employing state-of-the-art density functional theory together with the non-equilibrium Green's Function method, leads to current responses that differ by at least one order of magnitude for different bases and can thus provide a much more robust read-out of the base sequence. The implementation of our proposed setup could thus lead to a viable protocol for rapid DNA sequencing with significant consequences for the future of genome related research in particular and health care in general.Comment: 12 pages, 5 figure