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Projects below represent the major focus of research in the Hemminger group. For each category we include a brief description of the research overview as well as the instrumentation we employ for the projects.
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ION PROFILES AT AQUEOUS INTERFACES |
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We employ x-ray photoelectron spectroscopy (XPS) to probe the distributions of halide ions at interfaces. These fundamental studies have a profound impact on the understanding of atmospheric interfacial chemistry.
About x-ray photoelectron spectroscopy (XPS)
This gives a nice overview of the XPS technique. A worthwhile read for anyone who is breathing.
Partitioning of ions at liquid surfaces
In collaboration with the Advanced Light Source (ALS) at Lawrence Berkeley National Labs, we use XPS to probe the ion concentration
as a function of depth from the surface of liquids.
The effect of organic surfactants on ion surface partitioning
Some text goes here about this project. Yay text.
Reactions of OH radical with ions at surfaces
Some text goes here about this project. Yay text.
Panorama of our XPS Laboratory
Follow this link to a full 360 degree panorama of our XPS laboratory. Requires Apple QuickTime VR 5 or later
(comes with many recent complete installations of QuickTime).
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OPTICAL PROPERTIES OF NANOPARTICLE ARRAYS |
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We research the phenomenon and find new applications of the unique electromagnetic properties of metal nanoparticles assembled in to linear arrays.
Physical Vapor Deposition (PVD)
Our method of making silver and gold nanoparticle arrays with particle gaps less than 10nm.
Surface Enhanced Raman Spectroscopy (SERS) on Silver Nanoparticle Arrays
Silver nanoparticle arrays enhance applied electromagnetic fields that enable SERS-based investigations. Using surface assembled thiophenol as a Raman probe, these linear arrays exhibit highly polarization-dependent surface enhanced Raman scattering. When light is polarized along the axis of the arrays, the enhanced Raman scattering signal is significantly stronger than Raman scattering when the incident light is polarized perpendicular to the axis of the arrays.
Surface Plasmon-Enhanced Photoluminescence of Hybrid Semiconductor Nanowires
Starting with the metal nanoparticle arrays mentioned above, we further desoposit semiconductor materials like CdS or CdSe forming core/shell hybrid nanowires. The coupling between the semiconductor shells and the surface plasmon supported by the metal cores yields enhanced photoluminescence.
Photochemistry on Silver Arrays
Utilizing the amplification of an applied electromagnetic field in the gaps between the nanoparticles in the array, we explore the further fabrication techniques of hybrid nanowires. From solution, we photodeposit complex metals and semiconductors using the enhanced electromagnetic fields. Further treatment of these hybrid wires can lead to one dimensional p-n junctions with application to solar cell technology.
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ORGANIC DEHYDROGENATION ON PLATINUM NANOPARTICLES |
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This block of text is for the title of this section which I have yet to write. We use scanning tunneling microscopy (STM) to image the reaction and high resolution electron energy loss spectroscopy (HREELS) to provide vibrational spectroscopy of these reactions.
About scanning tunneling microscopy (STM)
This gives a nice overview of the STM technique. A worthwhile read for anyone who is breathing.
High resolution mass spectrometry of carbene dehydrogenation
This text is a place holder for item one. So is this text. Yay. Text is fun. On the other hand, this text is here simply because I'm
on a roll.
Panorama of our STM Laboratory
Follow this link to a full 360 degree panorama of our STM laboratory. Requires Apple QuickTime VR 5 or later
(comes with many recent complete installations of QuickTime).
About electron energy loss spectroscopy (EELS), and high-resolution EELS (HREELS)
This gives a nice overview of these techniques. A worthwhile read for anyone who is breathing.
Panorama of the HREELS and TPD Laboratory
Follow this link to a full 360 degree panorama of the laboratory that contains our HREELS instrument.
Requires Apple QuickTime VR 5 or later
(comes with many recent complete installations of QuickTime).
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WATER INTERACTIONS WITH ORGANIC SURFACES |
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Aerosol surfaces contain a high fraction of organic molecules which are aged by photochemical and radical oxidation reactions in the atmosphere. We employ temperature programmed desorption (TPD) spectroscopy to characterize the fundamental interaction between water and mimetic organic aerosol surfaces.
About temperature programmed desorption (TPD) spectroscopy
This gives a nice overview of TPD. A worthwhile read for anyone who is breathing.
Water interaction with a mixed monolayer
Mixed self-assembled monolayers of hydrophilic and hydrophobic character mimic the surfaces of processed, atmospherically
aged aerosol. We characterize the interaction of these monolayers with water to determine how the hydrophilic and hydrophobic
domain size affects the water binding.
Characterization of thiol monolayer formation on gold
Formation of self-assembled thiol monolayers on gold is a well-known technique in many fields of science. Most of these reactions
are performed in solution (e.g. ethanol), but questions remain regarding thiol monolayer formation from gas-phase adsorbates. We
are presently developing experiments to elucidate this mechanism.
Panorama of the HREELS and TPD Laboratory
Follow this link to a full 360 degree panorama of the laboratory that contains our TPD instrument.
Requires Apple QuickTime VR 5 or later
(comes with many recent complete installations of QuickTime).
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