Download or read book Characterization of Functionalized Self assembled Monolayers and Surface attached Interlocking Molecules Using Near edge X ray Absorption Fine Structure Spectroscopy written by Trevor Michael Willey and published by . This book was released on 2004 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of Functionalized Bio Molecular Surfaces with Self Assembled Monolayers and Bioreactive Ligands for Nano written by and published by . This book was released on 2008 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, the synthesis and characterization of functionalized biosurfaces that can be used for bioseparations and bio-nanotechnology are reported. A novel protein purification technique that incorporates chelating ligands and polymers onto the same chromatographic matrix is explored. A polysaccharide based gel, agarose, was modified systematically with hybrid ligands of the chelator iminodiacetic acid (IDA) and the polymer polyethylene glycol (PEG). The PEG molecule acts as a blocking polymer that can allow only small proteins to permeate onto the matrix surfaces and form conventional immobilized metal ion affinity chromatographic (IMAC) interactions with the chelators. Kinetic studies of chelator and polymer attachment were performed in order to effectively control the chelator and polymer densities on the matrix. Studies with different PEG surface densities and their effects on the adsorption of several proteins (e.g. myoglobin, lysozyme and bovine serum albumin (BSA)) were evaluated to characterize these new hybrid size exclusion IMAC (SEIMAC) matrices. An exclusion effect was observed while adsorption as observed in IMAC systems took place. Functionalization schemes and procedures were extended in the activation and incorporation of affinity ligands on inorganic surfaces such as gold surfaces. Functional gold platforms were explored for development of nano-interconnects via functionalized self assembled monolayers (FSAMs) on gold to attach specific affinity ligands as linkers to immobilize biomolecules, such as microtubules (MTs). MTs eventually could be utilized as self assembling structures and templates for fabrication of nano-scale bio-interconnect arrays and networks. In this work, different organothiols were used to form FSAMs and anti-glutathione S-transferase was attached as a linker to utilize the attachment of MT cap proteins, gamma-tubulin. The gamma-tubulin could recognize specifically a heterodimer of the MTs and can provide a nucleation center for MT growth. Several methodologies were employed including photolithographic methods and the use of photoreactive compounds for proper micro/nano scale dual protein functionalization of surfaces with homogeneous affinity ligands and with heterogeneous ligands as well.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 740 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Electronic Structure of Biomolecular Self Assembled Monolayers written by Matthaeus Anton Wolak and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The studies presented here address the characterization of the electronic structure of various self-assembled monolayers (SAMs) of peptide nucleic acid (PNA) and tetraphenylporphyrin (TPP) SAMs and arrays, formed on gold substrates. PNA is a promising alternative to DNA for bio-sensing applications, as well as for strategies for self-assembly based on nucleic acid hybridization. In recent years charge transfer through PNA molecules was a focus of research due to possible applications in self-assembled molecular circuits and molecular tools. In light of this research it is interesting to investigate the electronic structure of PNA interfaces to gold, a potential electrode material. TPP is, due to its electronic structure, an organic p-type molecular semiconductor. Such a material can provide an alternative to standard micro- and optoelectronic devices and in recent years more attention was paid to semiconducting polymers and organic compounds offering these low-cost and flexible alternatives. Therefore, it is of high importance to investigate the prospect of using modified TPP molecules for the formation of interconnected molecular networks on metallic surfaces. All investigated monolayers were formed from solution in a nitrogen atmosphere inside a homemade glove box. This process allowed for PNA SAM and TPP SAM and array formation on clean Au substrates without the exposure to the ambient atmosphere. Ultraviolet and X-ray photoemission spectroscopy (UPS and XPS) measurements on the resulting PNA SAMs and TPP SAMs and arrays, which were performed in a to the glove box attached vacuum chamber containing a photoemission spectrometer, revealed the hole injection barriers at the interfaces and the interface dipoles. In addition to the UPS and XPS measurements on PNA, electronic structure calculations based on molecular dynamics sampling of the PNA structure were obtained, yielding the HOMO-LUMO gap and the electronic density of states for PNA.
Download or read book Intermolecular Interactions and Surface Properties of Self Assembled Monolayers of Functional Boron Clusters written by Dominic Pascal Goronzy and published by . This book was released on 2019 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-assembled monolayers (SAMs) are an advantageous platform for probing the fundamental interactions that dictate the spontaneous formation of nanostructures and supramolecular assemblies and directly affect macroscale properties. As such, SAMs provide an avenue for creating surfaces with defined chemical and physical properties. The assembly of these nanoscale constructs is driven by three primary factors: the interface between the substrate and the monolayer, the interactions between the adsorbate molecules, and the interface between the monolayer and the environment. I studied an icosahedral cage boron cluster, the carborane, as a building block for SAMs with properties that we can tune to advantage. Carboranes have several favorable traits, including providing a scaffold for a variety of functional groups. A chalcogenide group, typically a thiol, is used for surface attachment; moreover, bifunctional carboranes also enable control of the valency during assembly and greater reactivity at the environmental interface of the SAM. Additionally, isomers of carboranethiol have distinct dipole moments in terms of orientation and magnitude. The dipoles can lead to the formation of long-range dipole dipole networks within the SAM, which can stabilize the SAM and also modify the surface properties of the material. The rigid, symmetric backbone of the carborane cage results in SAMs that are relatively pristine and defect free. Due to these advantageous traits, carboranes enable the creation of monolayers with tunable interactions at the SAM interfaces. This system not only enables myself and others to study the molecular forces of assembly but also facilitates the simultaneous modification of both chemical and physical properties of surfaces and interfaces. This thesis describes several carborane based surface assemblies and the variable interactions they have within the SAM interfaces. The introduction of a second thiol group to the carborane cage can be used to modulate the interaction of the SAM with the substrate. Carboranedithiol SAMs exhibit two binding modes, a monovalent state and a divalent state. The presence of these two modes enables tuning of valency using acid base chemistry and thus the ratio of singly bound to dual bound surface molecules can be modified during deposition. Another avenue to alter the interactions at the substrate-monolayer interface is to use an alternative functional group for surface attachment. A chalcogenide group similar to thiol is selenol, however carboraneselenolate SAMs have a distinct surface morphology compared to carboranethiolate SAMs. Carboraneselenolate SAMs exhibit a dynamic double lattice where surface molecules appear to switch between high- and low-conductance binding modes. This morphology is consistent with other cage molecule selenolate SAMs and is typically associated with substrate-mediated interactions. In contrast, the carboraneselenolate SAMs are resistant to thermal rearrangement and desorption due to the dipole dipole interactions within the monolayer. Carboranethiols can be modified by adding a carboxylic acid functional group that both alter the interactions within the monolayer and provide a platform for further reactions at the environmental interface. The introduction of a laterally positioned carboxyl functional group increases the steric demands of the molecule, thereby decreasing the packing density, but also enables hydrogen bonding interactions within the monolayer. The pKa of the surface bound carboxylic acid is shifted such that it is approximately two pH units less acidic than in solution. This shift is driven by the dielectric of the environment that the carboxyl group experiences on the surface, which is determined by the intermolecular interactions within the monolayer, partial desolvation, and the proximity to the substrate surface. The carboxyl group also remains available for further chemistry on the surface and can coordinate with a variety of metal ions or be used as an attachment point for performing chemical lift off lithography (CLL). This lithographic technique was performed successfully on several types of carboxyl carboranethiolate SAMs. The use of these SAMs also enabled the characterization of the post CLL substrate surface via scanning tunneling microscopy. This analysis revealed the molecules left behind during the CLL process are either in small molecular islands or sparsely packed, highly mobile molecules. There remain many opportunities for further chemistry to be performed with these carboxyl terminated SAMs or with carboranethiol SAMs with other additional functional groups. Carborane-based SAMs are a versatile system that provides a high degree of tunability at all three interfaces of a SAM. The work presented lays the foundation for further application in lithography, like CLL, as well as the use of these SAMs in organic electronics and devices and as interfacial materials.
Download or read book Characterization of Redox active Monolayers for Use in Molecular Memory Devices written by Amir Ali Yasseri and published by . This book was released on 2004 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Formation and Study of Self assembled Monolayers with Molecular Recognition and Catalytic Properties written by David Alan Offord and published by . This book was released on 1995 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Self Assembly of Flat Organic Molecules on Metal Surfaces written by Manuela Mura and published by Springer Science & Business Media. This book was released on 2012-06-30 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Manuela Mura's thesis is devoted to ab initio studies of self-assembled organic molecules on a gold surface. This area of research is particularly vibrant because of the various applications such studies have in nanoscience and surface chemistry and physics. In this thesis Manuela Mura uses theory to suggest atomistic models for the observed assembled and she proposes an assembly mechanism. The methods and results developed as part of this work will be of wide interest to physicists and chemists working on the assemblies of organic molecules on crystal surfaces.
Download or read book Structure Stability and Reactivity of Self assembled Monolayers on AU 111 written by Lili Duan and published by . This book was released on 2001 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structural Characterization of Self assembled Monolayers Within Molecular Junctions written by Paula Elena Colavita and published by . This book was released on 2005 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Dynamics in Self assembled Monolayers and Polymers Studied Via Sensitive Dielectric Spectroscopy written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For many molecular systems, interpreting experimental molecular dynamics, by studying the response of a system to external stimuli, is a difficult task. Often the experimental response cannot be reasonably connected to a specific molecular motion. The aim of this work is to examine molecular systems where this difficulty can be overcome. We use sensitive dielectric spectroscopy to investigate the molecular dynamics of two different systems, chlorosilane self-assymbled monolayers and modified siloxane polymers. The polymers studied responded to changes in their surrounding media by altering their wetting characterstics. Because this macroscopic responsive is present, we are able correlate the microscopic response (as measured by dielectric spectroscopy) to likely molecular motions. The goal of the self-assembled monolayer work is similar albeit by a different approach. In this case, the degrees of freedom were limited by using surface bound molecules. By controlling the molecular density we are able to investigate both local, non-cooperative motions as well as interacting dynamics. Specifically, we will show a connection between the interacting dynamics of the self-assembled monolayers to glass transitions found in more complicated materials.
Download or read book Self assembly of Amino Acids on Noble Metal Surfaces written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the 110 substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T> 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the
Download or read book Understanding On surface Structure Formation and Chemical Transformations from Theoretical Spectroscopy written by Hazem Aldahhak and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic molecules experience appealing applications in the industry of electronic devices. The key to developing the functionality of these applications lies in the thorough understanding of the electronic structure of the employed molecules and their interactions with the unavoidable surfaces. In the first part of this thesis, state-of-the-art density functional theory (DFT) calculations in close collaboration with experiment have been presented to exemplary address the on-surface structure formation in the prototypical (i) perylene-based diindenoperylene molecule (DIP) on a reactive surface and in (ii) a functional molecule with a nonuniform internal charge distribution, namely the perylene-3,4,9,10-tetracarboxylic diahydride(PTCDA), on ionic surfaces. For both systems, the adsorption mechanisms have been rationalised and compared. The second part of this thesis presents a DFT-guided multi-technique investigation on the interfacial chemistry of a macrocyclic low-symmetry molecule, namely the free-base5,10,15-tris(pentafluorophenyl)corroles (H3TpFPC), adsorbed on Ag(111). Combining structural modelling with high-level calculations of relevant X-ray core-levels and absorption edges, a detailed insight into the complex on-surface chemistry of corroles has been achieved. Beside corroborating the on-surface reactions and providing valuable information on the geometries of corrolic species, it is demonstrated that theory-assisted near edge X-ray absorption fine-structure (NEXAFS) spectroscopy enables the site-sensitive monitoring of on-surface chemical reactions, thus, providing information not accessible by other techniques. ; eng
Download or read book Characterization and Functionalization of Substrates and Nanoparticles for Detection of Surface Binding Events of Biomolecules written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation mainly focuses on detection of biomolecules on metal and metal-oxide surfaces by photoelectrochemistry. Characterization of DNA monolayers on the surface of gold was studied in detail by X-ray photoelectron spectroscopy (XPS), Polarization Modulated Infrared reflectance absorbance Spectroscopy (PMIRRAS) and FTIR. An electrochemical technique Chronocoulometry (CC) quantified the surface coverage of ssDNA on gold using a redox label. The issues that affected the hybridization efficiency of DNA on the gold surface were analyzed and parameters for optimum hybridization were established by the same techniques used to detect ssDNA on the surface. Though gold is a well-known surface, the thiol chemistry, which is the basis of attaching DNA on the surface, is not robust and reproducible due to the desorption of probes from the surface during hybridization, which involves elevating the temperature. Hybridization yield on gold surfaces could not be determined accurately as the desorption of probe from the surface was a competing phenomenon during hybridization event. As a result, new substrates were analyzed and indium-doped tin oxide (ITO) was found to be a very useful substrate because of the ease with which it can be modified with COOH, Phosphates, Phosphonates and silanes. In addition, the physical properties of ITO make it an attractive candidate to use in creating bioarrays. It is highly conductive and tansparent in the visible region and reflective in the IR. Compared to the thiol chemistry on gold the phosphates are much stronger and resistant to elevated temperatures used for hybridization. ITO electrodes can sustain relatively high potentials required to oxidize gold nanoparticles used as labels to detect hybridization. All these properties can be utilized to characterize ssDNA modified ITO surfaces and surface DNA hybridization either by optical or electrical methods. 12-Phosphonododecanoic acid (12-PDA) formed a well-ordered monolayer on the ITO.
Download or read book Formation and Characterization of Molecular Junctions Based on Self assembled Monolayers on Au and GaAs written by Candra Panglijen and published by . This book was released on 2006 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Specimen Handling Preparation and Treatments in Surface Characterization written by Alvin W. Czanderna and published by Springer Science & Business Media. This book was released on 1998 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is intended for professionals, researchers, technicians and students who are newcomers to the field as well as those with experience. It will be an important resource in the following fields: surface science, electronic materials and processes, thin film deposition, surface compositional analysis and related topical areas such as corrosion, oxidation, reduction, adsorption, desorption, adhesion, epitaxial growth and contamination. The presentation uses a tutorial and pedagogical approach.
Download or read book Molecular Electronics written by Ari Aviram and published by . This book was released on 1998 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume explores the resurgence of interest in the field of molecular electronics in view of recent advances in such areas as molecular wires, molecular components, fabrication, and assemblies of molecular scale devices and their wiring on surfaces. It shows how molecular electronics offer scientists an opportunity to study and understand a new class of materials, on the molecular level and in isolation, while offering to engineers a new microelectronics technology.
