Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Chemistry

PDF

University of Richmond

Series

2015

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd Aug 2015

Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd

Chemistry Faculty Publications

Networked films of monolayer-protected clusters (MPCs), alkanethiolate-stabilized gold nanoparticles, can be thermally decomposed to form stable gold on glass substrates that are subsequently modified with self-assembled monolayers (SAMs) for use as modified electrodes. Electrochemical assessment of these SAM-modified gold substrates, including double-layer capacitance measurements, linear sweep desorption of the alkanethiolates, and diffusional redox probing, all show that SAMs formed on gold supports formed from thermolysis of MPC films possess substantially higher defect density compared to SAMs formed on traditional evaporated gold. The density of defects in the SAMs on thermolyzed gold is directly related to the strategies used to assemble …

Go to article

Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold Mar 2015

Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold

Chemistry Faculty Publications

A systematic study of the structure–function relationships critical to understanding the sensing mechanism of 1st generation amperometric glucose biosensors with an embedded nanoparticle (NP) network is presented. Xerogel-based films featuring embedded glucose oxidase enzyme and doped with alkanethiolate-protected gold NPs, known as monolayer protected clusters (MPCs), exhibit significantly enhanced performance compared to analogous systems without NPs including higher sensitivity, faster response time, and extended linear/dynamic ranges. The proposed mechanism involves diffusion of the glucose to glucose oxidase within the xerogel, enzymatic reaction production of H2O2 with subsequent diffusion to the embedded network of MPCs where it is oxidized, an event …

Go to article

Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold Feb 2015

Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold

Chemistry Faculty Publications

For most chemistry curricula, laboratory-based activities in quantitative and instrumental analysis continue to be an important aspect of student development/training, one that can be more effective if conceptual understanding is delivered through an inquiry-based process relating the material to relevant issues of public interest and student career trajectories. Laboratory experiences that actively engage students in this manner can be difficult to identify and execute. A special topics, project-based laboratory module is presented here that utilizes multiple techniques and instruments to investigate toxic metal content (lead, cadmium, and arsenic) in children’s toys and toy jewelry. The module effectively illustrates a considerable …

Go to article

Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold Jan 2015

Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold

Chemistry Faculty Publications

Xerogel-based first-generation amperometric glucose biosensors, constructed through specific layer-by-layer assembly of films featuring glucose oxidase doped xerogel, a diffusion-limiting xerogel layer, and capped with both electropolymerized polyphenol and blended polyurethane semipermeable membranes, are presented. The specific combination of xerogels formed from specific silane precursors, including propyl-trimethoxysilane, isobutyl-trimethoxysilane, octyl-trimethoxysilane, and hydroxymethyl-triethoxysilane, exhibit impressive dynamic and linear ranges of detection (e.g., ≥24–28 mM glucose) and low response times, as well as significant discrimination against common interferent species such as acetaminophen, ascorbic acid, sodium nitrite, oxalic acid, and uric acid as determined by selectivity coefficients. Additionally, systematic electrochemical and contact angle studies of …

Go to article

Friedel–Crafts Hydroxyalkylation Of Indoles Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Christopher D. Poff, Alissa N. Nizinski Jan 2015

Friedel–Crafts Hydroxyalkylation Of Indoles Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Christopher D. Poff, Alissa N. Nizinski

Chemistry Faculty Publications

Indoles and N-alkylindoles undergo Friedel–Crafts addition to aldehydes in the presence of trimethylsilyl trifluoromethanesulfonate and a trialkylamine to produce 3-(1- silyloxyalkyl)indoles. Neutralization of the reaction mixture with pyridine followed by deprotection under basic conditions with tetrabutylammonium fluoride provides the 1:1 adduct as the free alcohol. This method prevents spontaneous conversion of the desired products to the thermodynamically favored bisindolyl(aryl)methanes, a process typically observed when indoles are reacted with aldehydes under acidic conditions.

Go to article

First Principles Predictions Of Van Der Waals Bonded Inorganic Crystal Structures: Test Case, Hgcl2, Valentino R. Cooper, Kelling J. Donald Jan 2015

First Principles Predictions Of Van Der Waals Bonded Inorganic Crystal Structures: Test Case, Hgcl2, Valentino R. Cooper, Kelling J. Donald

Chemistry Faculty Publications

We study the crystals structure and stability of four possible polymorphs of HgCl2 using first principles density functional theory. Mercury (II) halides are a unique class of materials which, depending on the halide species, form in a wide range of crystal structures, ranging from densely packed solids to layered materials and molecular solids. Predicting the groundstate structure of any member of this group from first principles, therefore, requires a general purpose functional that treats van der Waals bonding and covalent/ionic bonding adequately. Here, we demonstrate that the non-local van der Waals density functional paired with the C09 exchange functional …

Go to article

One-Pot Silyl Ketene Acetal-Formation-Mukaiyama–Mannich Additions To Imines Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Jared A. Ingersoll, Hadleigh M. Glist, Carolyn M. Dombrowski, Adam T. Barnett Jan 2015

One-Pot Silyl Ketene Acetal-Formation-Mukaiyama–Mannich Additions To Imines Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Jared A. Ingersoll, Hadleigh M. Glist, Carolyn M. Dombrowski, Adam T. Barnett

Chemistry Faculty Publications

In the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine base, thioesters are readily converted to silyl ketene acetals in situ and undergo Mukaiyama–Mannich addition to N-phenylimines in one pot. The silyl triflates appears to play two roles, activating both the thioester and the imine. This process also works well when thioesters are replaced with amides, esters, or ketones. Products are isolated as desilylated anilines without the necessity of a deprotection step. Yields range from 65-99%.

Go to article