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Articles 1 - 8 of 8
Full-Text Articles in Physics
Force-Feedback High-Speed Atomic Force Microscope For Studying Large Biological Systems, Byung I. Kim, Ryan Boehm
Force-Feedback High-Speed Atomic Force Microscope For Studying Large Biological Systems, Byung I. Kim, Ryan Boehm
Physics Faculty Publications and Presentations
We designed and developed a high-speed atomic force microscope (HSAFM) utilizing a force-feedback scheme for imaging large biological samples. The system collects three simultaneous images: a deflection image, a topographic image, and a force image. We demonstrated that this force-feedback HSAFM is capable of acquiring large topographic images of Escherichia coli biofilms at approximately one frame per second in air. We discuss how the self-actuating cantilever and the piezo tube follow those larger biological topographic features during the HSAFM imaging process.
Influence Of Solvent On The Chiral Resolution Of Organic Molecules On Au(111): Ec-Stm Study Of Biphenyl Dicarboxylic Acid On Au(111) In An Aqueous Environment, Byung I. Kim, Joey Hanson, Matthew Turner, Lauren Reeder
Influence Of Solvent On The Chiral Resolution Of Organic Molecules On Au(111): Ec-Stm Study Of Biphenyl Dicarboxylic Acid On Au(111) In An Aqueous Environment, Byung I. Kim, Joey Hanson, Matthew Turner, Lauren Reeder
Physics Faculty Publications and Presentations
Adsorption-induced chiral resolution of organic molecules is important due to its potential applications in stereo-selective catalysis. We studied the adsorption-induced chiral resolution using a model achiral molecule of 4,4′ biphenyl dicarboxylic acid (BPDA) on Au(111) in 0.1 M perchloric acid (HClO4) by electrochemical scanning tunneling microscopy (EC-STM). Our experimental data showed that the BPDA molecules formed island structures with distinctive preferred orientations at the length scale of the molecular size. The molecules did not show any orientational ordering above the length scale, indicating that chiral resolution was absent in the aqueous environment. Previously, the molecules were found to …
Effects Of Long-Range Tip-Sample Interaction On Magnetic Force Imaging: A Comparative Study Between Bimorph Driven System And Electrostatic Force Modulation, Byung I. Kim
Physics Faculty Publications and Presentations
Magnetic force microscopy (MFM) using electrostatic force modulation has been designed and developed to avoid the drawbacks of the bimorph driven system. The bimorph driven system has poor frequency response and overlap of the topographic features on magnetic structures of the MFM images. In the electrostatic force modulation system, the amplitude increases in the noncontact regime as the tip approaches due to the capacitive coupling between tip and sample. MFM using electrostatic force modulation has been applied to observe maze-like stripe domain structures on a CoCr film. The contrast mechanism and imaging stability of MFM using electrostatic force modulation are …
Unusual Crystallite Growth And Modification Of Ferromagnetism Due To Aging In Pure And Doped Zno Nanoparticles, Aaron Thurber, Gordon A. Alanko, Geoffrey L. Beausoleil Ii, Kelsey Dodge, Charles Hanna, Alex Punnoose
Unusual Crystallite Growth And Modification Of Ferromagnetism Due To Aging In Pure And Doped Zno Nanoparticles, Aaron Thurber, Gordon A. Alanko, Geoffrey L. Beausoleil Ii, Kelsey Dodge, Charles Hanna, Alex Punnoose
Physics Faculty Publications and Presentations
We report the unusual growth of pure and Fe-doped ZnO nanoparticles prepared by forced hydrolysis and the weakening of ferromagnetism due to aging in ambient conditions. More than four dozen nanoparticle samples in the size range of 4–20 nm were studied over 1 to 4 years. The as-prepared samples had significant changes in their crystallite sizes and magnetization as they aged in ambient conditions. Detailed studies using x ray diffraction and transmission electron microscopy (TEM) demonstrated that the crystallite size increased by as much as 1.4 times. Lattice parameters and strain also showed interesting changes. Magnetometry studies of Zn1−x …
Size, Surface Structure, And Doping Effects On Ferromagnetism In Sno2, Gordon A. Alanko, Aaron Thurber, Charles Hanna, Alex Punnoose
Size, Surface Structure, And Doping Effects On Ferromagnetism In Sno2, Gordon A. Alanko, Aaron Thurber, Charles Hanna, Alex Punnoose
Physics Faculty Publications and Presentations
The effects of crystallite size, surface structure, and dopants on the magnetic properties of semiconducting oxides are highly controversial. In this work, Fe:SnO2 nanoparticles were prepared by four wet-chemical methods, with Fe concentration varying from 0% to 20%. Analysis confirmed pure single-phase cassiterite with a crystallite size of 2.6 ± 0.1 nm that decreased with increasing. Fe% doped substitutionally as Fe3+. Pure SnO2 showed highly reproducible weak magnetization that varied significantly with synthesis method. Interestingly, doping SnO2 with Fe < 2.5% produced enhanced magnetic moments in all syntheses; the maximum of 1.6 × 10−4 µB/Fe ion at 0.1% Fe doping was much larger than the 2.6 × …
Concentration Dependence Of Magnetic Moment In Ce1-XFeXO2, Geoffrey L. Beausoleil Ii, Aaron Thurber, S. S. Rao, Gordon A. Alanko, Charles Hanna, Alex Punnoose
Concentration Dependence Of Magnetic Moment In Ce1-XFeXO2, Geoffrey L. Beausoleil Ii, Aaron Thurber, S. S. Rao, Gordon A. Alanko, Charles Hanna, Alex Punnoose
Physics Faculty Publications and Presentations
In this study, we examined the impact of iron doping on the structural, chemical, and magnetic properties of ceria (Ce1-xFexO2). Samples were produced in triplicate through a coprecipitation approach in a forced hydrolysis synthesis that yielded consistently sized nanocrystals using three different cerium precursors: cerium chloride, cerium ammonium nitrate, and cerium nitrate. Particles were characterized by x ray diffraction (XRD), x ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy, and vibrating sample magnetometry (VSM). XPS and EPR data shows iron to be in the Fe3+ state and confirms …
Limits On Large Extra Dimensions Based On Observations Of Neutron Stars With The Fermi-Lat, Jay Norris
Limits On Large Extra Dimensions Based On Observations Of Neutron Stars With The Fermi-Lat, Jay Norris
Physics Faculty Publications and Presentations
We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to γγ should contribute to the flux from NSs. Considering …
Cantilever-Based Optical Interfacial Force Microscopy, Byung I. Kim
Cantilever-Based Optical Interfacial Force Microscopy, Byung I. Kim
Physics Faculty Publications and Presentations
Atomic force microscopy (AFM) is one of the most important tools that lead current nanoscience and nanotechnology in many diverse areas including physics, chemistry, material engineering, and nano-biology. The current AFM technique has been routinely applied to forced unbinding processes of biomolecular complexes such as antibody-antigen binding, ligand-receptor pairs, protein unfolding, DNA unbinding, and RNA unfolding studies (Butt et al., 2005; Fritz & Anselmetti, 1997; Schumakovitch et al., 2002). AFMs have also been applied to intermolecular friction studies (Carpick et al., 1997; Colchero et al., 1996; Fernandez-Torres et al., 2003; Goddenhenrich et al., 1994; Goertz et al., 2007; B.I. Kim …