513 research outputs found
Label-free as-grown double wall carbon nanotubes bundles for Salmonella typhimurium immunoassay
Background:
A label-free immunosensor from as-grown double wall carbon nanotubes (DW) bundles was
developed for detecting Salmonella typhimurium. The immunosensor was fabricated by using
the as-grown DW bundles as an electrode material with an anti-Salmonella impregnated on
the surface. The immunosensor was electrochemically characterized by cyclic voltammetry.
The working potential (100, 200, 300 and 400 mV vs. Ag/AgCl) and the anti-Salmonella
concentration (10, 25, 50, 75, and 100 μg/mL) at the electrode were subsequently optimized.
Then, chronoamperometry was used with the optimum potential of 100 mV vs. Ag/AgCl) and
the optimum impregnated anti-Salmonella of 10 μg/mL to detect S. typhimurium cells (0-109
CFU/mL).
Results:
The DW immunosensor exhibited a detection range of 102 to 107 CFU/mL for the bacteria
with a limit of detection of 8.9 CFU/mL according to the IUPAC recommendation. The
electrode also showed specificity to S. typhimurium but no current response to Escherichia
coli. Conclusions:
These findings suggest that the use of a label-free DW immunosensor is promising for
detecting S. typhimurium
Flexible and transparent supercapacitors and fabrication using thin film carbon electrodes with controlled morphologies
Mechanically flexible and optically transparent thin film solid state supercapacitors are fabricated by assembling nano-engineered carbon electrodes in porous templates. The electrodes have textured graphitic surface films with a morphology of interconnected arrays of complex shapes and porosity. The graphitic films act as both electrode and current collector, and when integrated with solid polymer electrolyte function as thin film supercapacitors. The nanostructured electrode morphology and conformal electrolyte packaging provide enough energy and power density for electronic devices in addition to possessing excellent mechanical flexibility and optical transparency
Local charge transfer doping in suspended graphene nanojunctions
We report electronic transport measurements in nanoscale graphene transistors
with gold and platinum electrodes whose channel lengths are shorter than 100
nm, and compare them with transistors with channel lengths from 1 \textmu{}m to
50 \textmu{}m. We find a large positive gate voltage shift in charge neutrality
point (NP) for transistors made with platinum electrodes but negligible shift
for devices made with gold electrodes. This is consistent with the transfer of
electrons from graphene into the platinum electrodes. As the channel length
increases, the disparity between the measured NP using gold and platinum
electrodes disappears.Comment: 11 pages, 3 figures, to appear in Appl. Phys. Let
Second harmonic microscopy of monolayer MoS2
We show that the lack of inversion symmetry in monolayer MoS2 allows strong
optical second harmonic generation. Second harmonic of an 810-nm pulse is
generated in a mechanically exfoliated monolayer, with a nonlinear
susceptibility on the order of 1E-7 m/V. The susceptibility reduces by a factor
of seven in trilayers, and by about two orders of magnitude in even layers. A
proof-of-principle second harmonic microscopy measurement is performed on
samples grown by chemical vapor deposition, which illustrates potential
applications of this effect in fast and non-invasive detection of crystalline
orientation, thickness uniformity, layer stacking, and single-crystal domain
size of atomically thin films of MoS2 and similar materials.Comment: 6 pages, 4 figure
Molecular Simulation of MoS2 Exfoliation.
A wide variety of two-dimensional layered materials are synthesized by liquid-phase exfoliation. Here we examine exfoliation of MoS2 into nanosheets in a mixture of water and isopropanol (IPA) containing cavitation bubbles. Using force fields optimized with experimental data on interfacial energies between MoS2 and the solvent, multimillion-atom molecular dynamics simulations are performed in conjunction with experiments to examine shock-induced collapse of cavitation bubbles and the resulting exfoliation of MoS2. The collapse of cavitation bubbles generates high-speed nanojets and shock waves in the solvent. Large shear stresses due to the nanojet impact on MoS2 surfaces initiate exfoliation, and shock waves reflected from MoS2 surfaces enhance exfoliation. Structural correlations in the solvent indicate that shock induces an ice VII like motif in the first solvation shell of water
Valley trion dynamics in monolayerï¾ MoSe2
Charged excitons called trions play an important role in the fundamental valley dynamics in newly emerging two-dimensional semiconductor materials. We use ultrafast pump-probe spectroscopy to study the valley trion dynamics in aï¾ MoSe2ï¾ monolayer grown by using chemical vapor deposition. The dynamics displays an ultrafast trion formation followed by a nonexponential decay. The measurements at different pump fluences show that the trion decay dynamics becomes slower as the excitation density increases. The observed trion dynamics and the associated density dependence are a result of the trapping by two defect states as being the dominating decay mechanism. The simulation based on a set of rate equations reproduces the experimental data for different pump fluences. Our results reveal the important trion dynamics and identify the trapping by defect states as the primary trion decay mechanism in monolayerï¾ MoSe2ï¾ under the excitation densities used in our experiment
- …