Henning Groenzin - Academia.edu (original) (raw)

Papers by Henning Groenzin

Research paper thumbnail of 1-2. New insights into asphaltene molecular size and structure by combination of HRTEM and FD

Research paper thumbnail of Aqueous hydrogen bonding probed with polarization and matrix isolation spectroscopy

Journal of Molecular Structure, May 1, 2010

Research paper thumbnail of The single-crystal, basal face of ice Ih investigated with sum frequency generation

Journal of Chemical Physics, Dec 4, 2007

Sum frequency generation spectroscopy has been used to investigate the hydrogen-bonded region of ... more Sum frequency generation spectroscopy has been used to investigate the hydrogen-bonded region of single-crystal, hexagonal ice in the temperature range of 113–178K. The temperature and polarization dependences of the signal are used in conjunction with a recent theoretical model to suggest an interpretation of the bluest and reddest of the hydrogen-bonded peaks. The reddest feature is associated with strong hydrogen bonding; the dynamic polarizability of this feature is primarily parallel to the surface. It is assigned to a cooperative motion among the companion to the free-OH and four-coordinate oscillators hydrogen bonded to dangling lone-pair molecules on the surface. The bluest hydrogen-bonded feature is similarly assigned to a cooperative motion of the OH stretch of dangling lone-pair molecules and of four-coordinate molecules in the lower half bilayer that are hydrogen bonded to free-OH molecules. Reconstruction induced strain is present at as low as 113K. These results provide a richer picture of the ice surface than has heretofore been possible.

Research paper thumbnail of Multiplexed polarization spectroscopy: Measuring surface hyperpolarizability orientation

Journal of Chemical Physics, Aug 3, 2010

Infrared-visible sum frequency generation ͑SFG͒ has seen increasing usage as a surface probe, par... more Infrared-visible sum frequency generation ͑SFG͒ has seen increasing usage as a surface probe, particularly for liquid interfaces since they are amenable to few alternate probes. Interpreting the SFG data to arrive at a molecular-level configuration on the surface, however, remains a challenge. This paper reports a technique for analyzing and interpreting SFG data-called polarization-angle null or PAN-SFG. PAN-SFG enables ready identification of the ratio of the surface tangential and longitudinal hyperpolarizabilities-the hyperpolarizability direction-as well as the phase relationship between these components separated from the optical factors due to the substrate and experimental geometry. Separation of the surface optical factors results in an immediate connection between the null angle and the surface species polarization. If the Raman polarizability is also known, then PAN-SFG analysis, like the previously reported null techniques, provides a very accurate orientation. In addition, the reported polarization-angle, phase-shift analysis enables facile separation of the nonresonant background polarization from that of the resonant signal. Beyond orientation, PAN-SFG can be used to deconvolute overlapping resonances and identify components beyond a dipole response. This paper reports PAN-SFG for two systems providing deeper insight into both. An acetonitrile-water mixture was previously reported to undergo a phase transition at 7 mol %, attributed to a sudden change in orientation. PAN-SFG demonstrates that acetonitrile generates a classic dipole response and provides compelling evidence that the acetonitrile configuration remains constant as a function of concentration. An alternate model for the phase transition is presented. Like many aqueous systems, the SFG spectrum of the hydrogen-bonded region of ice consists of broad and overlapping features; features previously identified with PAN-SFG. Here PAN-SFG analysis is used to show that the reddest of these, the feature at 3098 cm −1 , contains a significant quadrupole contribution that grows as the temperature is lowered. The quadrupole and its temperature dependence are used to assign the 3098 cm −1 feature to bilayer-stitching-hydrogen bonds. This is the first definitive assignment in the hydrogen-bonded region of water.

Research paper thumbnail of Sum-frequency generation: Polarization surface spectroscopy analysis of the vibrational surface modes on the basal face of ice Ih

Journal of Chemical Physics, Jun 7, 2008

In recent years, sum-frequency generation (SFG) has been used to investigate numerous interfaces ... more In recent years, sum-frequency generation (SFG) has been used to investigate numerous interfaces including aqueous interfaces. A longstanding challenge to interpretation of the SFG results, along with the related aqueous-solution infrared and Raman spectra, is a lack of connection between features in the broad hydrogen-bonded region and molecular-level interactions or configurations. This paper reports results of a newly developed polarization analysis of the generated sum-frequency signal as a function of wavelength both to deconvolute spectral resonances and to characterize the dynamic polarization associated with the resonances. Operationally, the polarization angle of the generated sum frequency is determined by identifying the null angle. The technique is hence termed polarization-angle null analysis or PAN. PAN applied to ice is very powerful; it reveals that the hydrogen-bonded region of the basal face of ice Ih contains at least five oscillators, each with a distinct polarization. The dynamic polarizability of the longest wavelength oscillator is nearly entirely transverse (perpendicular to the surface normal, i.e., in the surface plane); in contrast, the shortest wavelength oscillator is almost entirely longitudinal (along the surface normal).

Research paper thumbnail of Surface Characterization of Nanoscale TiO<sub>2</sub> Film by Sum Frequency Generation Using Methanol as a Molecular Probe

Journal of Physical Chemistry B, Nov 27, 2003

ABSTRACT

Research paper thumbnail of Proton order in the ice crystal surface

Proceedings of the National Academy of Sciences of the United States of America, Apr 22, 2008

Research paper thumbnail of Molecular Species on Nanoparticulate Anatase TiO<sub>2</sub> Film Detected by Sum Frequency Generation: Trace Hydrocarbons and Hydroxyl Groups

Langmuir, Aug 1, 2003

Visible-infrared sum frequency generation (SFG) has been applied to probe molecular species on th... more Visible-infrared sum frequency generation (SFG) has been applied to probe molecular species on the surface of nanoparticulate anatase TiO2 films. A trace hydrocarbon film on the surface, not detected by Fourier transform infrared spectroscopy (FTIR), is easily sensed with SFG. The first direct observation of hydroxyl groups (-OH) on the TiO2 film surface by SFG is reported. A broad vibrational band with multiple peaks in the region of 3500-3800 cm-1 ascribed to OH groups reflects the surface heterogeneity of the material.

Research paper thumbnail of Sum frequency generation on single-crystalline ice Ih

Research paper thumbnail of High yield, single crystal ice via the Bridgman method

Review of Scientific Instruments, Mar 1, 2016

The surface chemistry of ice and of water is an important topic of study, especially given the ro... more The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature.

Research paper thumbnail of Comparative Study of Acetic Acid, Methanol, and Water Adsorbed on Anatase TiO<sub>2</sub> Probed by Sum Frequency Generation Spectroscopy

Journal of the American Chemical Society, Jun 22, 2005

The adsorption entropy change caused by the loss of translation and rotation can be calculated vi... more The adsorption entropy change caused by the loss of translation and rotation can be calculated via the molecular partition function Q. 1

Research paper thumbnail of Direct Observation of Competitive Adsorption between Methanol and Water on TiO<sub>2</sub>: An in Situ Sum-Frequency Generation Study

Journal of the American Chemical Society, Jun 15, 2004

The competitive adsorption between water and methanol, as well as reversible hydroxylation/dehydr... more The competitive adsorption between water and methanol, as well as reversible hydroxylation/dehydroxylation on the TiO2 surface, is unambiguously resolved for the first time by an in situ sum-frequency generation study.

Research paper thumbnail of PROBING THE NATIVE SURFACE MODES OF ICE (Ih)

The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particula... more The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particular the ppp polarization combination will be discussed. The detailed structure of the spectrum allows the correlation of the SFG bands to the molecular motion of the ice surface. The bands seem to arise from strongly coupled global stretch vibrations, which explains their large oscillator strength. The quality of the SFG spectrum, in particular the ppp combination, is strongly affected by the quality and crystallinity of the ice surface. The samples on which the spectra were taken were cut from single domain ice samples of 3 in in size. The cryptomorphological crystal growth methodology and subsequent characterization techniques prior to SFG interrogation will be described. Investigation of the degree of coupling between the oscillators by isotopic dilution is in progress.

Research paper thumbnail of Procede et dispositif de determination de la pression de depart d'une precipitation d'asphaltene

L'invention concerne un procede permettant de determiner la pression de depart d'une prec... more L'invention concerne un procede permettant de determiner la pression de depart d'une precipitation d'asphaltene dans un fluide de formation. Selon un mode de realisation, le procede consiste a) a isoler un echantillon de fluide de formation de fond de trou; b) a illuminer ledit echantillon a l'aide d'un rayonnement ultraviolet; c) a mesurer l'energie de fluorescence provenant de l'echantillon; d) a reduire la pression exercee sur l'echantillon; e) a repeter les phases b) a d); et f) a regler la pression de depart de la precipitation d'asphaltene pour qu'elle soit egale a la pression exercee sur l'echantillon, lorsqu'on detecte une brusque modification de l'energie de fluorescence. Un dispositif d'analyse optique de fond de trou comprend une lampe ultraviolette; un piston concu de facon a reduire la pression fluidique dans une region cellulaire optique par augmentation du volume d'un echantillon de fluide de formation isole;...

Research paper thumbnail of Abstract template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe Reference

template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using ... more template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe Reference J. Phys. Chem. B 2004, 108, 265-272. Authors Wang, Chuan-yi; Groenzin, Henning; Shultz, Mary Jane Abstract Sum frequency generation (SFG) vibrational spectroscopy is applied to study the surfaceSum frequency generation (SFG) vibrational spectroscopy is applied to study the surface characteristics of a film composed of nanoscale TiO2 particles, in which methanol is employed as a molecular probe. The SFG signal from methanol adsorbed on the TiO2 film surface in the CH region consists of four primary peaks located at 2828, 2855, 2935, and 2968 cm. The peaks at 2855 and 2968 cm arise from molecular methanol; the other two are attributed to methoxy produced by dissociative chemisorption of methanol on TiO2. Changes in the SFG features with methanol pressure and with surface temperature provide the first direct proof of methoxy generation on nanoparticul...

Research paper thumbnail of Sum-frequency studies of single crystalline ice Ih

... The violation of the second ice rule is called a Bjerrum defect. There are two types of Bjerr... more ... The violation of the second ice rule is called a Bjerrum defect. There are two types of Bjerrum defects; a bond with one hydrogen too many is called a D defect while a bond with one hydrogen too few is called an L defect. A 2 ...

Research paper thumbnail of Molecular Size and Structure of Asphaltenes from Various Sources

Energy & Fuels, 2000

... within in a single molecule. Previously, various fluorescence studies have shown that strong ... more ... within in a single molecule. Previously, various fluorescence studies have shown that strong intermolecular energy transfer occurs with crude oils and asphaltenes at sufficiently high concentrations. 17,36 - 38 This energy transfer ...

Research paper thumbnail of PROBING THE NATIVE SURFACE MODES OF ICE (Ih)

The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particula... more The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particular the ppp polarization combination will be discussed. The detailed structure of the spectrum allows the correlation of the SFG bands to the molecular motion of the ice surface. The bands seem to arise from strongly coupled global stretch vibrations, which explains their large oscillator strength. The quality of the SFG spectrum, in particular the ppp combination, is strongly affected by the quality and crystallinity of the ice surface. The samples on which the spectra were taken were cut from single domain ice samples of 3 in in size. The cryptomorphological crystal growth methodology and subsequent characterization techniques prior to SFG interrogation will be described. Investigation of the degree of coupling between the oscillators by isotopic dilution is in progress.

Research paper thumbnail of Apparatus and methods for determining velocity of oil in a flow stream

Research paper thumbnail of High yield, single crystal ice via the Bridgman method

Review of Scientific Instruments, 2016

The surface chemistry of ice and of water is an important topic of study, especially given the ro... more The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature.

Research paper thumbnail of 1-2. New insights into asphaltene molecular size and structure by combination of HRTEM and FD

Research paper thumbnail of Aqueous hydrogen bonding probed with polarization and matrix isolation spectroscopy

Journal of Molecular Structure, May 1, 2010

Research paper thumbnail of The single-crystal, basal face of ice Ih investigated with sum frequency generation

Journal of Chemical Physics, Dec 4, 2007

Sum frequency generation spectroscopy has been used to investigate the hydrogen-bonded region of ... more Sum frequency generation spectroscopy has been used to investigate the hydrogen-bonded region of single-crystal, hexagonal ice in the temperature range of 113–178K. The temperature and polarization dependences of the signal are used in conjunction with a recent theoretical model to suggest an interpretation of the bluest and reddest of the hydrogen-bonded peaks. The reddest feature is associated with strong hydrogen bonding; the dynamic polarizability of this feature is primarily parallel to the surface. It is assigned to a cooperative motion among the companion to the free-OH and four-coordinate oscillators hydrogen bonded to dangling lone-pair molecules on the surface. The bluest hydrogen-bonded feature is similarly assigned to a cooperative motion of the OH stretch of dangling lone-pair molecules and of four-coordinate molecules in the lower half bilayer that are hydrogen bonded to free-OH molecules. Reconstruction induced strain is present at as low as 113K. These results provide a richer picture of the ice surface than has heretofore been possible.

Research paper thumbnail of Multiplexed polarization spectroscopy: Measuring surface hyperpolarizability orientation

Journal of Chemical Physics, Aug 3, 2010

Infrared-visible sum frequency generation ͑SFG͒ has seen increasing usage as a surface probe, par... more Infrared-visible sum frequency generation ͑SFG͒ has seen increasing usage as a surface probe, particularly for liquid interfaces since they are amenable to few alternate probes. Interpreting the SFG data to arrive at a molecular-level configuration on the surface, however, remains a challenge. This paper reports a technique for analyzing and interpreting SFG data-called polarization-angle null or PAN-SFG. PAN-SFG enables ready identification of the ratio of the surface tangential and longitudinal hyperpolarizabilities-the hyperpolarizability direction-as well as the phase relationship between these components separated from the optical factors due to the substrate and experimental geometry. Separation of the surface optical factors results in an immediate connection between the null angle and the surface species polarization. If the Raman polarizability is also known, then PAN-SFG analysis, like the previously reported null techniques, provides a very accurate orientation. In addition, the reported polarization-angle, phase-shift analysis enables facile separation of the nonresonant background polarization from that of the resonant signal. Beyond orientation, PAN-SFG can be used to deconvolute overlapping resonances and identify components beyond a dipole response. This paper reports PAN-SFG for two systems providing deeper insight into both. An acetonitrile-water mixture was previously reported to undergo a phase transition at 7 mol %, attributed to a sudden change in orientation. PAN-SFG demonstrates that acetonitrile generates a classic dipole response and provides compelling evidence that the acetonitrile configuration remains constant as a function of concentration. An alternate model for the phase transition is presented. Like many aqueous systems, the SFG spectrum of the hydrogen-bonded region of ice consists of broad and overlapping features; features previously identified with PAN-SFG. Here PAN-SFG analysis is used to show that the reddest of these, the feature at 3098 cm −1 , contains a significant quadrupole contribution that grows as the temperature is lowered. The quadrupole and its temperature dependence are used to assign the 3098 cm −1 feature to bilayer-stitching-hydrogen bonds. This is the first definitive assignment in the hydrogen-bonded region of water.

Research paper thumbnail of Sum-frequency generation: Polarization surface spectroscopy analysis of the vibrational surface modes on the basal face of ice Ih

Journal of Chemical Physics, Jun 7, 2008

In recent years, sum-frequency generation (SFG) has been used to investigate numerous interfaces ... more In recent years, sum-frequency generation (SFG) has been used to investigate numerous interfaces including aqueous interfaces. A longstanding challenge to interpretation of the SFG results, along with the related aqueous-solution infrared and Raman spectra, is a lack of connection between features in the broad hydrogen-bonded region and molecular-level interactions or configurations. This paper reports results of a newly developed polarization analysis of the generated sum-frequency signal as a function of wavelength both to deconvolute spectral resonances and to characterize the dynamic polarization associated with the resonances. Operationally, the polarization angle of the generated sum frequency is determined by identifying the null angle. The technique is hence termed polarization-angle null analysis or PAN. PAN applied to ice is very powerful; it reveals that the hydrogen-bonded region of the basal face of ice Ih contains at least five oscillators, each with a distinct polarization. The dynamic polarizability of the longest wavelength oscillator is nearly entirely transverse (perpendicular to the surface normal, i.e., in the surface plane); in contrast, the shortest wavelength oscillator is almost entirely longitudinal (along the surface normal).

Research paper thumbnail of Surface Characterization of Nanoscale TiO<sub>2</sub> Film by Sum Frequency Generation Using Methanol as a Molecular Probe

Journal of Physical Chemistry B, Nov 27, 2003

ABSTRACT

Research paper thumbnail of Proton order in the ice crystal surface

Proceedings of the National Academy of Sciences of the United States of America, Apr 22, 2008

Research paper thumbnail of Molecular Species on Nanoparticulate Anatase TiO<sub>2</sub> Film Detected by Sum Frequency Generation: Trace Hydrocarbons and Hydroxyl Groups

Langmuir, Aug 1, 2003

Visible-infrared sum frequency generation (SFG) has been applied to probe molecular species on th... more Visible-infrared sum frequency generation (SFG) has been applied to probe molecular species on the surface of nanoparticulate anatase TiO2 films. A trace hydrocarbon film on the surface, not detected by Fourier transform infrared spectroscopy (FTIR), is easily sensed with SFG. The first direct observation of hydroxyl groups (-OH) on the TiO2 film surface by SFG is reported. A broad vibrational band with multiple peaks in the region of 3500-3800 cm-1 ascribed to OH groups reflects the surface heterogeneity of the material.

Research paper thumbnail of Sum frequency generation on single-crystalline ice Ih

Research paper thumbnail of High yield, single crystal ice via the Bridgman method

Review of Scientific Instruments, Mar 1, 2016

The surface chemistry of ice and of water is an important topic of study, especially given the ro... more The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature.

Research paper thumbnail of Comparative Study of Acetic Acid, Methanol, and Water Adsorbed on Anatase TiO<sub>2</sub> Probed by Sum Frequency Generation Spectroscopy

Journal of the American Chemical Society, Jun 22, 2005

The adsorption entropy change caused by the loss of translation and rotation can be calculated vi... more The adsorption entropy change caused by the loss of translation and rotation can be calculated via the molecular partition function Q. 1

Research paper thumbnail of Direct Observation of Competitive Adsorption between Methanol and Water on TiO<sub>2</sub>: An in Situ Sum-Frequency Generation Study

Journal of the American Chemical Society, Jun 15, 2004

The competitive adsorption between water and methanol, as well as reversible hydroxylation/dehydr... more The competitive adsorption between water and methanol, as well as reversible hydroxylation/dehydroxylation on the TiO2 surface, is unambiguously resolved for the first time by an in situ sum-frequency generation study.

Research paper thumbnail of PROBING THE NATIVE SURFACE MODES OF ICE (Ih)

The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particula... more The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particular the ppp polarization combination will be discussed. The detailed structure of the spectrum allows the correlation of the SFG bands to the molecular motion of the ice surface. The bands seem to arise from strongly coupled global stretch vibrations, which explains their large oscillator strength. The quality of the SFG spectrum, in particular the ppp combination, is strongly affected by the quality and crystallinity of the ice surface. The samples on which the spectra were taken were cut from single domain ice samples of 3 in in size. The cryptomorphological crystal growth methodology and subsequent characterization techniques prior to SFG interrogation will be described. Investigation of the degree of coupling between the oscillators by isotopic dilution is in progress.

Research paper thumbnail of Procede et dispositif de determination de la pression de depart d'une precipitation d'asphaltene

L'invention concerne un procede permettant de determiner la pression de depart d'une prec... more L'invention concerne un procede permettant de determiner la pression de depart d'une precipitation d'asphaltene dans un fluide de formation. Selon un mode de realisation, le procede consiste a) a isoler un echantillon de fluide de formation de fond de trou; b) a illuminer ledit echantillon a l'aide d'un rayonnement ultraviolet; c) a mesurer l'energie de fluorescence provenant de l'echantillon; d) a reduire la pression exercee sur l'echantillon; e) a repeter les phases b) a d); et f) a regler la pression de depart de la precipitation d'asphaltene pour qu'elle soit egale a la pression exercee sur l'echantillon, lorsqu'on detecte une brusque modification de l'energie de fluorescence. Un dispositif d'analyse optique de fond de trou comprend une lampe ultraviolette; un piston concu de facon a reduire la pression fluidique dans une region cellulaire optique par augmentation du volume d'un echantillon de fluide de formation isole;...

Research paper thumbnail of Abstract template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe Reference

template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using ... more template: TitleSurface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe Reference J. Phys. Chem. B 2004, 108, 265-272. Authors Wang, Chuan-yi; Groenzin, Henning; Shultz, Mary Jane Abstract Sum frequency generation (SFG) vibrational spectroscopy is applied to study the surfaceSum frequency generation (SFG) vibrational spectroscopy is applied to study the surface characteristics of a film composed of nanoscale TiO2 particles, in which methanol is employed as a molecular probe. The SFG signal from methanol adsorbed on the TiO2 film surface in the CH region consists of four primary peaks located at 2828, 2855, 2935, and 2968 cm. The peaks at 2855 and 2968 cm arise from molecular methanol; the other two are attributed to methoxy produced by dissociative chemisorption of methanol on TiO2. Changes in the SFG features with methanol pressure and with surface temperature provide the first direct proof of methoxy generation on nanoparticul...

Research paper thumbnail of Sum-frequency studies of single crystalline ice Ih

... The violation of the second ice rule is called a Bjerrum defect. There are two types of Bjerr... more ... The violation of the second ice rule is called a Bjerrum defect. There are two types of Bjerrum defects; a bond with one hydrogen too many is called a D defect while a bond with one hydrogen too few is called an L defect. A 2 ...

Research paper thumbnail of Molecular Size and Structure of Asphaltenes from Various Sources

Energy & Fuels, 2000

... within in a single molecule. Previously, various fluorescence studies have shown that strong ... more ... within in a single molecule. Previously, various fluorescence studies have shown that strong intermolecular energy transfer occurs with crude oils and asphaltenes at sufficiently high concentrations. 17,36 - 38 This energy transfer ...

Research paper thumbnail of PROBING THE NATIVE SURFACE MODES OF ICE (Ih)

The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particula... more The structure of the Sum Frequency Generation spectrum of the native surface of ice, in particular the ppp polarization combination will be discussed. The detailed structure of the spectrum allows the correlation of the SFG bands to the molecular motion of the ice surface. The bands seem to arise from strongly coupled global stretch vibrations, which explains their large oscillator strength. The quality of the SFG spectrum, in particular the ppp combination, is strongly affected by the quality and crystallinity of the ice surface. The samples on which the spectra were taken were cut from single domain ice samples of 3 in in size. The cryptomorphological crystal growth methodology and subsequent characterization techniques prior to SFG interrogation will be described. Investigation of the degree of coupling between the oscillators by isotopic dilution is in progress.

Research paper thumbnail of Apparatus and methods for determining velocity of oil in a flow stream

Research paper thumbnail of High yield, single crystal ice via the Bridgman method

Review of Scientific Instruments, 2016

The surface chemistry of ice and of water is an important topic of study, especially given the ro... more The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature.