ABSTRACT: New sensing techniques for detecting molecules, especially self-cleaning sensors, are in demand. Here we describe a room-temperature process in which a nanostructured substrate catalyzes the reaction of a target molecule with atmospheric oxygen and the reaction energy is absorbed by the substrate, where it can in principle be detected. Specifically, we report first-principles calculations describing a reaction between 2,4-dinitrotoluene (DNT) and atmospheric O(2) catalyzed by Fe-porphyrin at room temperature, incorporating an oxygen into the methyl group of DNT and releasing 1.9 eV per reaction. The atomic oxygen left on the Fe site can be removed by reacting with another DNT molecule, restoring the Fe catalyst.
Nano Letters 01/2013; · 13.20 Impact Factor
Journal of Power Sources 01/2013; 237:64-73. · 4.95 Impact Factor
ABSTRACT: A mathematical derivation of an analytical expression is presented to evaluate the van der Waals interaction between a sphere and a cylindrical rod. This expression then is applied to study the growth of one-dimensional nanostructures, such as nanorods, using a common growth mechanism in colloidal chemistry, the oriented attachment growth mechanism. Parameters associated with the dimensions and the separation of nanoparticles and nanorods are varied in calculations to assess their influence on the magnitude of the van der Waals interaction.
Physical Chemistry Chemical Physics 04/2012; 14(13):4548-53. · 3.57 Impact Factor
ABSTRACT: Graphene with high carrier mobility \mu\ is required both for graphene-based
electronic devices and for the investigation of the fundamental properties of
graphene's Dirac fermions. It is largely accepted that the mobility-limiting
factor in graphene is the Coulomb scattering off of charged impurities that
reside either on graphene or in the underlying substrate. This is true both for
traditional graphene devices on SiO2 substrates and possibly for the recently
reported high-mobility suspended and supported devices. An attractive approach
to reduce such scattering is to place graphene in an environment with high
static dielectric constant \kappa\ that would effectively screen the electric
field due to the impurities. However, experiments so far report only a modest
effect of high-\kappa\ environment on mobility. Here, we investigate the effect
of the dielectric environment of graphene by studying electrical transport in
multi-terminal graphene devices that are suspended in liquids with \kappa\
ranging from 1.9 to 33. For non-polar liquids (\kappa <5) we observe a rapid
increase of \mu\ with \kappa\ and report a record room-temperature mobility as
large as ~60,000 cm2/Vs for graphene devices in anisole (\kappa=4.3), while in
polar liquids (\kappa >18) we observe a drastic drop in mobility. We
demonstrate that non-polar liquids enhance mobility by screening charged
impurities adsorbed on graphene, while charged ions in polar liquids cause the
observed mobility suppression. Furthermore, using molecular dynamics simulation
we establish that scattering by out-of-plane flexural phonons, a dominant
scattering mechanism in suspended graphene in vacuum at room temperature, is
suppressed by the presence of liquids. We expect that our findings may provide
avenues to control and reduce carrier scattering in future graphene-based
ABSTRACT: Defects are known to affect nanoscale phase transitions, but their specific role in the metal-to-insulator transition in VO(2) has remained elusive. By combining plasmon resonance nanospectroscopy with density functional calculations, we correlate decreased phase-transition energy with oxygen vacancies created by strain at grain boundaries. By measuring the degree of metallization in the lithographically defined VO(2) nanoparticles, we find that hysteresis width narrows with increasing size, thus illustrating the potential for domain boundary engineering in phase-changing nanostructures.
Nano Letters 02/2012; 12(2):780-6. · 13.20 Impact Factor
ABSTRACT: Graphene with high carrier mobility μ is required both for graphene-based electronic devices and for the investigation of the fundamental properties of Dirac fermions. An attractive approach to increase the mobility is to place graphene in an environment with high static dielectric constant κ that would screen the electric field due to the charged impurities present near graphene's surface. Here we investigate the effect of the dielectric environment of graphene and study electrical transport in multi-terminal graphene devices suspended in liquids with κ ranging from 1.9 to 33. For non-polar liquids (κ<5), we observe a rapid increase of μ(κ), with room-temperature mobility reaching ~60,000 cm(2) Vs(-1) for devices in anisole (κ = 4.3). We associate this trend with dielectric screening of charged impurities adsorbed on graphene. We observe much lower mobility μ~20,000 cm(2) Vs(-1) for devices in polar liquids (κ ≥ 18) and explain it by additional scattering caused by ions present in such liquids.
Nature Communications 01/2012; 3:734. · 7.40 Impact Factor
ABSTRACT: The unimolecular decomposition reaction of TNT can in principle be used to design ways to either detect or remove TNT from the environment. Here, we report the results of a density functional theory study of possible ways to lower the reaction barrier for this decomposition process by ionization, so that decomposition and/or detection can occur at room temperature. We find that ionizing TNT lowers the reaction barrier for the initial step of this decomposition. We further show that a similar effect can occur if a positive moiety is bound to the TNT molecule. The positive charge produces a pronounced electron redistribution and dipole formation in TNT with minimal charge transfer from TNT to the positive moiety.
The Journal of Physical Chemistry A 06/2011; 115(28):8142-6. · 2.95 Impact Factor