Richard McCreery - Academia.edu (original) (raw)

Papers by Richard McCreery

JOURNAL-ELECTROCHEMICAL …, 2000

The oxygen reduction reaction has been studied extensively on metal electrodes (Pt, Hg, Ag, and A... more The oxygen reduction reaction has been studied extensively on metal electrodes (Pt, Hg, Ag, and Au) and nonmetal electrodes (car-bon, diamond, and metal oxides), due mainly to the importance of dioxygen reduction to electrochemical energy conversion.1-18 Many different types of ...

Advanced Energy Materials

Journal of the American Chemical Society, Feb 7, 2018

Photocurrents generated by illumination of carbon-based molecular junctions were investigated as ... more Photocurrents generated by illumination of carbon-based molecular junctions were investigated as diagnostics of how molecular structure and orbital energies control electronic behavior. Oligomers of eight aromatic molecules covalently bonded to an electron-beam deposited carbon surface were formed by electrochemical reduction of diazonium reagents, with layer thicknesses in the range of 5-12 nm. Illumination through either the top or bottom partially transparent electrodes produced both an open circuit potential (OCP) and a photocurrent (PC), and the polarity and spectrum of the photocurrent depended directly on the relative positions of the frontier orbitals and the electrode Fermi level (E). Electron donors with relatively high HOMO energies yielded positive OCP and PC, and electron acceptors with LUMO energies closer to E than the HOMO energy produced negative OCP and PC. In all cases, the PC spectrum and the absorption spectrum of the oligomer in the molecular junction had very ...

Micron (Oxford, England : 1993), Jan 7, 2018

We report, for the first time, the three dimensional reconstruction (3D) of a transistor from a m... more We report, for the first time, the three dimensional reconstruction (3D) of a transistor from a microprocessor chip and roughness of molecular electronic junction obtained by electron tomography with Hole Free Phase Plate (HFPP) imaging. The HFPP appears to enhance contrast between inorganic materials and also increase the visibility of interfaces between different materials. We demonstrate that the degree of enhancement varies depending on material and thickness of the samples using experimental and simulation data.

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1992

American Laboratory, 1996

J Org Chem, 1980

The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized ... more The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized 1, 4-dimethoxynaphthalenes has been studied under a variety of conditions. Many substituted 1, 4-dimethoxy aromatics afford high yields of the respective quinone ...

J Med Chem, 1978

... Chem., 3, 222 (1966). (7) T.-Y. Shen, R. E. Witzel, G. L. Walford, and M'. V. Ruyle, US.... more ... Chem., 3, 222 (1966). (7) T.-Y. Shen, R. E. Witzel, G. L. Walford, and M'. V. Ruyle, US. Patent 3759948 (1973). ... Reactions of Chlorpromazine Cation Radical with Physiologically Occurring Nucleophiles Hung-Yuan Cheng, Patricia Holt Sackett, and Richard L. McCreery* ...

J Med Chem, 1978

The oxidation of 7-hydroxychlorpromazine, a process associated with several side effects of chlor... more The oxidation of 7-hydroxychlorpromazine, a process associated with several side effects of chlorpromazine therapy, was examined in vitro by electrochemistry and rapid-scanning spectrophotometry. At pH 2, the oxidation results in a quantitative yield of 7,8-dioxochlorpromazine, but several intermediates are observable during the course of the reaction. These include a quinone imine with a half-life of 0.1 s, a monosubstituted benzoquinone with a half-life of-50 s, and a disubstituted benzoquinone with a half-life of-5 min. The concentrations of each intermediate were determined quantitatively as a function of time, and a complete oxidation mechanism is proposed. At pH 7. the yield of 7,8-dioxochlorpromazine is less than at pH 2, and an additional reaction pathway icvolving direct hydroxylation of the quinone imine is observed. The relationship of these reactions to the pharmacology of the hydroxylated chlorpromazine metabolites is discussed

The Journal of Chemical Physics, Jan 14, 2007

The electronic properties of molecular junctions of the general type carbon/molecule/TiO2Au were ... more The electronic properties of molecular junctions of the general type carbon/molecule/TiO2Au were examined as examples of "molecular heterojunctions" consisting of a molecular monolayer and a semiconducting oxide. Junctions containing fluorene bonded to pyrolyzed photoresist film (PPF) were compared to those containing Al2O3 instead of fluorene, and those with only the TiO2 layer. The responses to voltage sweep and pulse stimulation were strongly dependent on junction composition and temperature. A transient current response lasting a few milliseconds results from injection and trapping of electrons in the TiO2 layer, and occurred in all three junction types studied. Conduction in PPFTiO2Au junctions is consistent with space charge limited conduction at low voltage, then a sharp increase in current once the space charge fills all the traps. With fluorene present, there is a slower, persistent change in junction conductance which may be removed by a reverse polarity pulse. This "memory" effect is attributed to a redox process in the TiO2 which generates TiIII and/or TiII, which have much higher conductance than TiO2 due to the presence of conduction band electrons. The redox process amounts to "dynamic doping" of the TiO2 layer by the imposed electric field. The memory effect arises from a combination of the properties of the molecular and oxide layers, and is a special property of the molecular heterojunction configuration.

Nano Letters, 2011

Diffusion of metal atoms onto a molecular monolayer attached to a conducting surface permits elec... more Diffusion of metal atoms onto a molecular monolayer attached to a conducting surface permits electronic contact to the molecules with minimal heat transfer or structural disturbance. Surface-mediated metal deposition (SDMD) involves contact between "cold" diffusing metal atoms and molecules, due to shielding of the molecules from direct exposure to metal vapor. Measurement of the current through the molecular layer during metal diffusion permits observation of molecular conductance for junctions containing as few as one molecule. Discrete conductance steps were observed for 1-10 molecules within a monolayer during a single deposition run, corresponding to "recruitment" of additional molecules as the contact area between the diffusing Au layer and molecules increases. For alkane monolayers, the molecular conductance measured with SDMD exhibited an exponential dependence on molecular length with a decay constant (β) of 0.90 per CH(2) group, comparable to that observed by other techniques. Molecular conductance values were determined for three azobenzene molecules, and correlated with the offset between the molecular HOMO and the contact Fermi level, as expected for hole-mediated tunneling. Current-voltage curves were obtained during metal deposition showed no change in shape for junctions containing 1, 2, and 10 molecules, implying minimal intermolecular interactions as single molecule devices transitioned into several molecules devices. SDMD represents a "soft" metal deposition method capable of providing single molecule conductance values, then providing quantitative comparisons to molecular junctions containing 10(6) to 10(10) molecules.

Surface and Coatings Technology, 2001

Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion ... more Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion of AA2024-T3 and pure Al are studied in this work. Raman spectroscopy was used to investigate the nature of chromate in CCCs through a comparison with the spectra of known standards and artificial Cr(III)/Cr(VI) mixed oxides. Chromate was shown to be released from CCCs and to migrate to and protect a nearby, uncoated area in the artificial scratch cell. However, experiments investigating the effect of chromate in solution on anodic dissolution kinetics under potentiostatic control indicated that large chromate concentrations were needed to have an effect.

Journal of the American Chemical Society, 2011

The Journal of Organic Chemistry, 1980

The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized ... more The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized 1, 4-dimethoxynaphthalenes has been studied under a variety of conditions. Many substituted 1, 4-dimethoxy aromatics afford high yields of the respective quinone ...

Journal of Medicinal Chemistry, 1976

The possibility that catecholamines can be oxidized via aberrant pathways in vivo is open to ques... more The possibility that catecholamines can be oxidized via aberrant pathways in vivo is open to question, but in vitro oxidation via aerobic manipulations is established. Assuming oxidation does occur, we have examined quantitatively the fast chemical reactions of the initial oxidation products, the o-quinones. The nature and rates of these reactions were studies under the conditions simulating closely those which presumably exist in mammalian brain. The results are in close accord with existing literature and especially support oxidation pathways recently reported in [3H]-norepinephrine binding to particulate cell fractions.

JOURNAL-ELECTROCHEMICAL …, 2000

The oxygen reduction reaction has been studied extensively on metal electrodes (Pt, Hg, Ag, and A... more The oxygen reduction reaction has been studied extensively on metal electrodes (Pt, Hg, Ag, and Au) and nonmetal electrodes (car-bon, diamond, and metal oxides), due mainly to the importance of dioxygen reduction to electrochemical energy conversion.1-18 Many different types of ...

Advanced Energy Materials

Journal of the American Chemical Society, Feb 7, 2018

Photocurrents generated by illumination of carbon-based molecular junctions were investigated as ... more Photocurrents generated by illumination of carbon-based molecular junctions were investigated as diagnostics of how molecular structure and orbital energies control electronic behavior. Oligomers of eight aromatic molecules covalently bonded to an electron-beam deposited carbon surface were formed by electrochemical reduction of diazonium reagents, with layer thicknesses in the range of 5-12 nm. Illumination through either the top or bottom partially transparent electrodes produced both an open circuit potential (OCP) and a photocurrent (PC), and the polarity and spectrum of the photocurrent depended directly on the relative positions of the frontier orbitals and the electrode Fermi level (E). Electron donors with relatively high HOMO energies yielded positive OCP and PC, and electron acceptors with LUMO energies closer to E than the HOMO energy produced negative OCP and PC. In all cases, the PC spectrum and the absorption spectrum of the oligomer in the molecular junction had very ...

Micron (Oxford, England : 1993), Jan 7, 2018

We report, for the first time, the three dimensional reconstruction (3D) of a transistor from a m... more We report, for the first time, the three dimensional reconstruction (3D) of a transistor from a microprocessor chip and roughness of molecular electronic junction obtained by electron tomography with Hole Free Phase Plate (HFPP) imaging. The HFPP appears to enhance contrast between inorganic materials and also increase the visibility of interfaces between different materials. We demonstrate that the degree of enhancement varies depending on material and thickness of the samples using experimental and simulation data.

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1992

American Laboratory, 1996

J Org Chem, 1980

The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized ... more The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized 1, 4-dimethoxynaphthalenes has been studied under a variety of conditions. Many substituted 1, 4-dimethoxy aromatics afford high yields of the respective quinone ...

J Med Chem, 1978

... Chem., 3, 222 (1966). (7) T.-Y. Shen, R. E. Witzel, G. L. Walford, and M'. V. Ruyle, US.... more ... Chem., 3, 222 (1966). (7) T.-Y. Shen, R. E. Witzel, G. L. Walford, and M'. V. Ruyle, US. Patent 3759948 (1973). ... Reactions of Chlorpromazine Cation Radical with Physiologically Occurring Nucleophiles Hung-Yuan Cheng, Patricia Holt Sackett, and Richard L. McCreery* ...

J Med Chem, 1978

The oxidation of 7-hydroxychlorpromazine, a process associated with several side effects of chlor... more The oxidation of 7-hydroxychlorpromazine, a process associated with several side effects of chlorpromazine therapy, was examined in vitro by electrochemistry and rapid-scanning spectrophotometry. At pH 2, the oxidation results in a quantitative yield of 7,8-dioxochlorpromazine, but several intermediates are observable during the course of the reaction. These include a quinone imine with a half-life of 0.1 s, a monosubstituted benzoquinone with a half-life of-50 s, and a disubstituted benzoquinone with a half-life of-5 min. The concentrations of each intermediate were determined quantitatively as a function of time, and a complete oxidation mechanism is proposed. At pH 7. the yield of 7,8-dioxochlorpromazine is less than at pH 2, and an additional reaction pathway icvolving direct hydroxylation of the quinone imine is observed. The relationship of these reactions to the pharmacology of the hydroxylated chlorpromazine metabolites is discussed

The Journal of Chemical Physics, Jan 14, 2007

The electronic properties of molecular junctions of the general type carbon/molecule/TiO2Au were ... more The electronic properties of molecular junctions of the general type carbon/molecule/TiO2Au were examined as examples of "molecular heterojunctions" consisting of a molecular monolayer and a semiconducting oxide. Junctions containing fluorene bonded to pyrolyzed photoresist film (PPF) were compared to those containing Al2O3 instead of fluorene, and those with only the TiO2 layer. The responses to voltage sweep and pulse stimulation were strongly dependent on junction composition and temperature. A transient current response lasting a few milliseconds results from injection and trapping of electrons in the TiO2 layer, and occurred in all three junction types studied. Conduction in PPFTiO2Au junctions is consistent with space charge limited conduction at low voltage, then a sharp increase in current once the space charge fills all the traps. With fluorene present, there is a slower, persistent change in junction conductance which may be removed by a reverse polarity pulse. This "memory" effect is attributed to a redox process in the TiO2 which generates TiIII and/or TiII, which have much higher conductance than TiO2 due to the presence of conduction band electrons. The redox process amounts to "dynamic doping" of the TiO2 layer by the imposed electric field. The memory effect arises from a combination of the properties of the molecular and oxide layers, and is a special property of the molecular heterojunction configuration.

Nano Letters, 2011

Diffusion of metal atoms onto a molecular monolayer attached to a conducting surface permits elec... more Diffusion of metal atoms onto a molecular monolayer attached to a conducting surface permits electronic contact to the molecules with minimal heat transfer or structural disturbance. Surface-mediated metal deposition (SDMD) involves contact between "cold" diffusing metal atoms and molecules, due to shielding of the molecules from direct exposure to metal vapor. Measurement of the current through the molecular layer during metal diffusion permits observation of molecular conductance for junctions containing as few as one molecule. Discrete conductance steps were observed for 1-10 molecules within a monolayer during a single deposition run, corresponding to "recruitment" of additional molecules as the contact area between the diffusing Au layer and molecules increases. For alkane monolayers, the molecular conductance measured with SDMD exhibited an exponential dependence on molecular length with a decay constant (β) of 0.90 per CH(2) group, comparable to that observed by other techniques. Molecular conductance values were determined for three azobenzene molecules, and correlated with the offset between the molecular HOMO and the contact Fermi level, as expected for hole-mediated tunneling. Current-voltage curves were obtained during metal deposition showed no change in shape for junctions containing 1, 2, and 10 molecules, implying minimal intermolecular interactions as single molecule devices transitioned into several molecules devices. SDMD represents a "soft" metal deposition method capable of providing single molecule conductance values, then providing quantitative comparisons to molecular junctions containing 10(6) to 10(10) molecules.

Surface and Coatings Technology, 2001

Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion ... more Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion of AA2024-T3 and pure Al are studied in this work. Raman spectroscopy was used to investigate the nature of chromate in CCCs through a comparison with the spectra of known standards and artificial Cr(III)/Cr(VI) mixed oxides. Chromate was shown to be released from CCCs and to migrate to and protect a nearby, uncoated area in the artificial scratch cell. However, experiments investigating the effect of chromate in solution on anodic dissolution kinetics under potentiostatic control indicated that large chromate concentrations were needed to have an effect.

Journal of the American Chemical Society, 2011

The Journal of Organic Chemistry, 1980

The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized ... more The anodic oxidation of 12 functionalized 1, 4-dimethoxybenzene derivatives and 8 functionalized 1, 4-dimethoxynaphthalenes has been studied under a variety of conditions. Many substituted 1, 4-dimethoxy aromatics afford high yields of the respective quinone ...

Journal of Medicinal Chemistry, 1976

The possibility that catecholamines can be oxidized via aberrant pathways in vivo is open to ques... more The possibility that catecholamines can be oxidized via aberrant pathways in vivo is open to question, but in vitro oxidation via aerobic manipulations is established. Assuming oxidation does occur, we have examined quantitatively the fast chemical reactions of the initial oxidation products, the o-quinones. The nature and rates of these reactions were studies under the conditions simulating closely those which presumably exist in mammalian brain. The results are in close accord with existing literature and especially support oxidation pathways recently reported in [3H]-norepinephrine binding to particulate cell fractions.