Charging effects and quantum properties of small superconducting tunnel junctions. M. Iansiti, M.... more Charging effects and quantum properties of small superconducting tunnel junctions. M. Iansiti, M. Tinkham, AT Johnson, Walter F. Smith, and CJ Lobb Department of Physics and Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138. ...
In the effort to make better and less expensive optoelectronics devices molecular self-assembly p... more In the effort to make better and less expensive optoelectronics devices molecular self-assembly proves to be a solution - in solution.
Nanowires have been made by decomposing organometallic gases in a UHV scanning tunneling microsco... more Nanowires have been made by decomposing organometallic gases in a UHV scanning tunneling microscope (STM); this process is a form of chemical vapor deposition (CVD). Our STM is coupled to a commercial scanning electron microscope (SEM), which ...
Tetrakis(4-sulfonatophenyl) porphine (TPPS4) molecules form complexes with chrysotile nanotubes i... more Tetrakis(4-sulfonatophenyl) porphine (TPPS4) molecules form complexes with chrysotile nanotubes in a chloroform-methanol solvent; the self-assembly is driven by Coulombic attractions. The UV/vis absorption spectrum indicates J-aggregation. In AFM, the complexes appear as ...
APS Bulletin of the American Physical Society. 2005 APS March Meeting. MondayFriday, March 2125... more APS Bulletin of the American Physical Society. 2005 APS March Meeting. MondayFriday, March 2125, 2005; Los Angeles, CA. ...
Submitted for the MAR06 Meeting of The American Physical Society Atomic Force Microscope-Based Su... more Submitted for the MAR06 Meeting of The American Physical Society Atomic Force Microscope-Based Surface Potential and Surface Photovoltage Studies of Porphyrin Nanorod Thin Films TODD HOLDEN, Brooklyn College of CUNY, WALTER SMITH, Haverford College, A.D. SCHWAB, Appalachian State University, J.C. DE PAULA, Lewis and Clark College — We have performed atomic force microscope-based surface potential and surface photovoltage measurements on porphyrin grown as nanorods about 5 nm in diameter and 1 micron long. These nanorods have been shown to have peculiar photoconducting properties in that the photoconductivity grows under light illumination for up to 1 hour. In addition, when a current is flowed through the nanorods, they become “trained.” That is after the light is turned off and the ends of the nanorod are short circuited together, a small current will flow opposite to the direction of the original photocurrent. The material exhibits nanoscale potential fluctuations as well as selec...
Submitted for the MAR07 Meeting of The American Physical Society Persistent Photoconductivity and... more Submitted for the MAR07 Meeting of The American Physical Society Persistent Photoconductivity and Photo-induced Morphology Changes of Porphyrin Nanorods B.E. FELDMAN, E.A. MULLER, V.H. JOINES, W.F. SMITH, Haverford College, A.D. SCHWAB, Appalachian State U., J.C. DE PAULA, Lewis and Clark College, D.E. JOHNSTON, A.T. JOHNSON, U. of Pennsylvania — Tetrakis(4-sulfonatophenyl) porphine self assembles into welldefined nanorods with intriguing photoelectronic properties.1 Recently, we have found that, over long time scales, they undergo a transition from non-persistent photoconductivity (NPPC) to a new mode, in which part of the conductivity persists after the light is blocked, decaying over hundreds of seconds. NPPC initially dominates, but its growth asymptotes within 2-3 hours of illumination, while the persistent current continues to grow, even after 8 hours of light exposure. The decay of persistent current after the light is blocked can be roughly modeled by a single exponential; a...
Bulletin of the American Physical Society, Mar 19, 2009
ABSTRACT Diacid meso-tetra(4-sulfonatophenyl)porphine (TPPS4^2- ) monomers have been shown to sel... more ABSTRACT Diacid meso-tetra(4-sulfonatophenyl)porphine (TPPS4^2- ) monomers have been shown to self assemble into nanorods with well-defined cross-section^1 and intriguing photoelectronic properties^2. However, the structure and conduction mechanism of these nanorods is poorly understood, and questions remain about the aggregation process. Using density functional theory (DFT), we first obtain optimized geometries and atomic-charges for the monomers, which we then use for subsequent molecular dynamics (MD) simulations to observe the initial stages of the self-assembly process. This work uses the resources of the National Energy Research Scientific Computing Center. ^1A.D. Schwab et al., J. Phys. Chem. B 107, 11339 (2003). ^2A.D. Schwab et al., Nano Letters 4, 1261 (2004).
We briefly review our work on the use of the scanning tunneling microscope (STM) for the synthesi... more We briefly review our work on the use of the scanning tunneling microscope (STM) for the synthesis and study of structures down to the 10 nm scale. In particular, we have demonstrated for the first time that the STM can dissociate organometallic gas molecules and thus produce a pattern of a desired metal. The smallest patterns thus far have been
Charging effects and quantum properties of small superconducting tunnel junctions. M. Iansiti, M.... more Charging effects and quantum properties of small superconducting tunnel junctions. M. Iansiti, M. Tinkham, AT Johnson, Walter F. Smith, and CJ Lobb Department of Physics and Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138. ...
In the effort to make better and less expensive optoelectronics devices molecular self-assembly p... more In the effort to make better and less expensive optoelectronics devices molecular self-assembly proves to be a solution - in solution.
Nanowires have been made by decomposing organometallic gases in a UHV scanning tunneling microsco... more Nanowires have been made by decomposing organometallic gases in a UHV scanning tunneling microscope (STM); this process is a form of chemical vapor deposition (CVD). Our STM is coupled to a commercial scanning electron microscope (SEM), which ...
Tetrakis(4-sulfonatophenyl) porphine (TPPS4) molecules form complexes with chrysotile nanotubes i... more Tetrakis(4-sulfonatophenyl) porphine (TPPS4) molecules form complexes with chrysotile nanotubes in a chloroform-methanol solvent; the self-assembly is driven by Coulombic attractions. The UV/vis absorption spectrum indicates J-aggregation. In AFM, the complexes appear as ...
APS Bulletin of the American Physical Society. 2005 APS March Meeting. MondayFriday, March 2125... more APS Bulletin of the American Physical Society. 2005 APS March Meeting. MondayFriday, March 2125, 2005; Los Angeles, CA. ...
Submitted for the MAR06 Meeting of The American Physical Society Atomic Force Microscope-Based Su... more Submitted for the MAR06 Meeting of The American Physical Society Atomic Force Microscope-Based Surface Potential and Surface Photovoltage Studies of Porphyrin Nanorod Thin Films TODD HOLDEN, Brooklyn College of CUNY, WALTER SMITH, Haverford College, A.D. SCHWAB, Appalachian State University, J.C. DE PAULA, Lewis and Clark College — We have performed atomic force microscope-based surface potential and surface photovoltage measurements on porphyrin grown as nanorods about 5 nm in diameter and 1 micron long. These nanorods have been shown to have peculiar photoconducting properties in that the photoconductivity grows under light illumination for up to 1 hour. In addition, when a current is flowed through the nanorods, they become “trained.” That is after the light is turned off and the ends of the nanorod are short circuited together, a small current will flow opposite to the direction of the original photocurrent. The material exhibits nanoscale potential fluctuations as well as selec...
Submitted for the MAR07 Meeting of The American Physical Society Persistent Photoconductivity and... more Submitted for the MAR07 Meeting of The American Physical Society Persistent Photoconductivity and Photo-induced Morphology Changes of Porphyrin Nanorods B.E. FELDMAN, E.A. MULLER, V.H. JOINES, W.F. SMITH, Haverford College, A.D. SCHWAB, Appalachian State U., J.C. DE PAULA, Lewis and Clark College, D.E. JOHNSTON, A.T. JOHNSON, U. of Pennsylvania — Tetrakis(4-sulfonatophenyl) porphine self assembles into welldefined nanorods with intriguing photoelectronic properties.1 Recently, we have found that, over long time scales, they undergo a transition from non-persistent photoconductivity (NPPC) to a new mode, in which part of the conductivity persists after the light is blocked, decaying over hundreds of seconds. NPPC initially dominates, but its growth asymptotes within 2-3 hours of illumination, while the persistent current continues to grow, even after 8 hours of light exposure. The decay of persistent current after the light is blocked can be roughly modeled by a single exponential; a...
Bulletin of the American Physical Society, Mar 19, 2009
ABSTRACT Diacid meso-tetra(4-sulfonatophenyl)porphine (TPPS4^2- ) monomers have been shown to sel... more ABSTRACT Diacid meso-tetra(4-sulfonatophenyl)porphine (TPPS4^2- ) monomers have been shown to self assemble into nanorods with well-defined cross-section^1 and intriguing photoelectronic properties^2. However, the structure and conduction mechanism of these nanorods is poorly understood, and questions remain about the aggregation process. Using density functional theory (DFT), we first obtain optimized geometries and atomic-charges for the monomers, which we then use for subsequent molecular dynamics (MD) simulations to observe the initial stages of the self-assembly process. This work uses the resources of the National Energy Research Scientific Computing Center. ^1A.D. Schwab et al., J. Phys. Chem. B 107, 11339 (2003). ^2A.D. Schwab et al., Nano Letters 4, 1261 (2004).
We briefly review our work on the use of the scanning tunneling microscope (STM) for the synthesi... more We briefly review our work on the use of the scanning tunneling microscope (STM) for the synthesis and study of structures down to the 10 nm scale. In particular, we have demonstrated for the first time that the STM can dissociate organometallic gas molecules and thus produce a pattern of a desired metal. The smallest patterns thus far have been
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