6 research outputs found
How Do Colloidal Nanoparticles Move in a Solution under an Electric Field?: <i>In Situ</i> Light Scattering Analysis
Understanding the dynamics of colloidal
nanoparticles
(NPs) in
a solution is the key to assembling them into solids through a solution
process such as electrophoretic deposition. In this study, newly developed in situ analysis with light scattering is used to examine
NP dynamics induced by a non-uniform electric field. We reveal that
the symmetric directions of moving NP aggregates are due to dielectrophoresis
between the cylindrical electrodes, while the actual NP deposition
is based on the charge of NPs (electrophoresis). Over time, the symmetry
of the dynamics becomes less evident, inducing feeble deposition as
the less-ordered dynamics become stronger. Eventually, two separate
deposition mechanisms emerge as the deposition rate decreases with
the change in the NP dynamics. Furthermore, we identify the vortex-like
NP motion between the electrodes. These in situ analyses
provide insights into the electrophoretic deposition mechanism and
NP behavior in a solution under an electric field for fine film construction
How Do Colloidal Nanoparticles Move in a Solution under an Electric Field?: <i>In Situ</i> Light Scattering Analysis
Understanding the dynamics of colloidal
nanoparticles
(NPs) in
a solution is the key to assembling them into solids through a solution
process such as electrophoretic deposition. In this study, newly developed in situ analysis with light scattering is used to examine
NP dynamics induced by a non-uniform electric field. We reveal that
the symmetric directions of moving NP aggregates are due to dielectrophoresis
between the cylindrical electrodes, while the actual NP deposition
is based on the charge of NPs (electrophoresis). Over time, the symmetry
of the dynamics becomes less evident, inducing feeble deposition as
the less-ordered dynamics become stronger. Eventually, two separate
deposition mechanisms emerge as the deposition rate decreases with
the change in the NP dynamics. Furthermore, we identify the vortex-like
NP motion between the electrodes. These in situ analyses
provide insights into the electrophoretic deposition mechanism and
NP behavior in a solution under an electric field for fine film construction
How Do Colloidal Nanoparticles Move in a Solution under an Electric Field?: <i>In Situ</i> Light Scattering Analysis
Understanding the dynamics of colloidal
nanoparticles
(NPs) in
a solution is the key to assembling them into solids through a solution
process such as electrophoretic deposition. In this study, newly developed in situ analysis with light scattering is used to examine
NP dynamics induced by a non-uniform electric field. We reveal that
the symmetric directions of moving NP aggregates are due to dielectrophoresis
between the cylindrical electrodes, while the actual NP deposition
is based on the charge of NPs (electrophoresis). Over time, the symmetry
of the dynamics becomes less evident, inducing feeble deposition as
the less-ordered dynamics become stronger. Eventually, two separate
deposition mechanisms emerge as the deposition rate decreases with
the change in the NP dynamics. Furthermore, we identify the vortex-like
NP motion between the electrodes. These in situ analyses
provide insights into the electrophoretic deposition mechanism and
NP behavior in a solution under an electric field for fine film construction
How Do Colloidal Nanoparticles Move in a Solution under an Electric Field?: <i>In Situ</i> Light Scattering Analysis
Understanding the dynamics of colloidal
nanoparticles
(NPs) in
a solution is the key to assembling them into solids through a solution
process such as electrophoretic deposition. In this study, newly developed in situ analysis with light scattering is used to examine
NP dynamics induced by a non-uniform electric field. We reveal that
the symmetric directions of moving NP aggregates are due to dielectrophoresis
between the cylindrical electrodes, while the actual NP deposition
is based on the charge of NPs (electrophoresis). Over time, the symmetry
of the dynamics becomes less evident, inducing feeble deposition as
the less-ordered dynamics become stronger. Eventually, two separate
deposition mechanisms emerge as the deposition rate decreases with
the change in the NP dynamics. Furthermore, we identify the vortex-like
NP motion between the electrodes. These in situ analyses
provide insights into the electrophoretic deposition mechanism and
NP behavior in a solution under an electric field for fine film construction
Anomalous K-Point Phonons in Noble Metal/Graphene Heterostructure Activated by Localized Surface Plasmon Resonance
The metal/graphene interface has been one of the most important research topics with regard to charge screening, charge transfer, contact resistance, and solar cells. Chemical bond formation of metal and graphene can be deduced from the defect induced D-band and its second-order mode, 2D band, measured by Raman spectroscopy, as a simple and nondestructive method. However, a phonon mode located at ???1350 cm-1, which is normally known as the defect-induced D-band, is intriguing for graphene deposited with noble metals (Ag, Au, and Cu). We observe anomalous K-point phonons in nonreactive noble metal/graphene heterostructures. The intensity ratio of the midfrequency mode at ???1350 cm-1 over G-band (???1590 cm-1) exhibits nonlinear but resonant behavior with the excitation laser wavelength, and more importantly, the phonon frequency-laser energy dispersion is ???10-17 cm-1 eV-1, which is much less than the conventional range. These phonon modes of graphene at nonzero phonon wave vector (q ??? 0) around K points are activated by localized surface plasmon resonance and not by the defects due to chemical bond formation of metal/graphene. This hypothesis is supported by density functional theory (DFT) calculations for noble metals and Cr along with the measured contact resistances
Modulation of the Dirac Point Voltage of Graphene by Ion-Gel Dielectrics and Its Application to Soft Electronic Devices
We investigated systematic modulation of the Dirac point voltage of graphene transistors by changing the type of ionic liquid used as a main gate dielectric component. Ion gels were formed from ionic liquids and a non-triblock-copolymer-based binder involving UV irradiation. With a fixed cation (anion), the Dirac point voltage shifted to a higher voltage as the size of anion (cation) increased. Mechanisms for modulation of the Dirac point voltage of graphene transistors by designing ionic liquids were fully understood using molecular dynamics simulations, which excellently matched our experimental results. It was found that the ion sizes and molecular structures play an essential role in the modulation of the Dirac point voltage of the graphene. Through control of the position of their Dirac point voltages on the basis of our findings, complementary metal–oxide–semiconductor (CMOS)-like graphene-based inverters using two different ionic liquids worked perfectly even at a very low source voltage (<i>V</i><sub>DD</sub> = 1 mV), which was not possible for previous works. These results can be broadly applied in the development of low-power-consumption, flexible/stretchable, CMOS-like graphene-based electronic devices in the future