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J Chem Phys ; 136(12): 124702, 2012 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-22462883


The electronic properties of p-type, n-type, and ambipolar spiro materials have been investigated using a combination of photoemission spectroscopy, electron energy-loss spectroscopy, and density functional based calculations. Our results provide insight into the occupied density of states as well as the electronic excitation spectra. Comparison of experimental and theoretical data allows the identification of the orbitals responsible for charge transport and optical properties.

ACS Appl Mater Interfaces ; 3(7): 2195-9, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21671615


Single-crystal-like organic heterojuntions are fabricated with disk-like molecules and different rodlike molecules. Hole transparent and blocking transport are demonstrated with photoemission spectroscopy and field-effect transistors. These results demonstrate a route to utilize adjustable interfacial electronic structure and control transport behavior in developing functional organic crystalline devices and crystalline nanocircuits.

J Chem Phys ; 134(19): 194504, 2011 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-21599070


The electronic excitations of manganese phthalocyanine (MnPc) films were studied as a function of potassium doping using electron energy-loss spectroscopy in transmission. Our data reveal doping induced changes in the excitation spectrum, and they provide evidence for the existence of three doped phases: K(1)MnPc, K(2)MnPc, and K(4)MnPc. Furthermore, the addition of electrons first leads to a filling of orbitals with strong Mn 3d character, a situation which also affects the magnetic moment of the molecule.

ACS Nano ; 3(12): 4098-104, 2009 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-19908851


The use of SiO(2) as a catalyst for graphitic nanostructures, such as carbon nanotubes and graphene, is a new and rapidly developing catalyst system. A key question is whether carbide phases form in the reaction. We show the formation of SiC from SiO(2) nanoparticles for the synthesis of graphitic carbon nanostructures via chemical vapor deposition (CVD) at 900 degrees C. Our findings point to the carbothermal reduction of SiO(2) in the CVD reaction. The inclusion of triethyl borate apparently accelerates the process and leads to improved yields. The study helps better understand the growth mechanisms at play in carbon nanotube and carbon nanofiber formation when using SiO(2) catalysts.

Cristalização/métodos , Grafite/química , Modelos Químicos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Dióxido de Silício/química , Simulação por Computador , Gases/química , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
J Phys Chem B ; 113(30): 10051-4, 2009 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-19572657


Nanometer thin films of nonsublimable multinuclear transition metal complexes were deposited on Si by means of spin coating to enable photoelectron spectroscopy studies. In combination with density functional theory calculations, photoelectron spectroscopy is applied to gain insight into the electronic and magnetic properties of the complexes.