Parkinson’s disease (PD) is characterized by progressive dopaminergic cell loss in the substantia nigra (SN) and elevated iron levels demonstrated by autopsy. Direct visualization of iron with live imaging techniques has not yet been successful. The aim of this study is to visualize and quantify the distribution of cellular iron using an intrinsic iron hyperspectral fluorescence signal. The 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of PD was established in SHSY5Y cells exposed to iron with ferric ammonium citrate (FAC, 100 μM). The hyperspectral fluorescence signal of iron was examined using a high-resolution dark-field optical microscope system with signal absorption for the visible/near infrared spectral range. The 6-h group showed heavy cellular iron deposition compared with the 1-h group. The cellular iron was dispersed in a small particulate form, whereas the extracellular iron was aggregated. In addition, iron particles were found to be concentrated on the cell membrane/edge of shrunken cells. The iron accumulation readily occurred in MPP+-induced cells, which is consistent with previous studies demonstrating elevated iron levels in the SN. This direct iron imaging could be applied to analyze the physiological role of iron, and its application might be expanded to various neurological disorders involving metals, such as copper, manganese, or zinc.
We report the application of an optical microscope equipped with a high-resolution dark-field condenser for detecting dynamic responses of cellular nanostructures in real time. Our system provides an easy-to-use technique to visualize biological specimens without any staining. This system can visualize the dynamic behavior of nanospheres and nanofibers, such as F-actin, at the leading edges of adjacent neuronal cells. We confirmed that the nanofibers imaged with this high-resolution optical microscopic technique are F-actin by using fluorescence microscopy after immunostaining the F-actin of fixed cells. Furthermore, cellular dynamics are enhanced by applying noncontact electric field stimulation through a transparent graphene electric field stimulator. High-resolution label-free optical microscopy enables the visualization of nanofiber dynamics initiated by filopodial nanofiber contacts. In conclusion, our optical microscopy system allows the visualization of nanoscale cellular dynamics under various external stimuli in real time without specific staining.
Electrical stimulation affects cellular behaviors including division, migration and wound healing [1-3]. Cellular
injury often occurs due to the imbalance of the endogenous electric field [3]. In order to recover from the injury,
wound healing process requires various cellular changes such as regeneration, migration, and the enhancement of cytoskeletal proteins and growth factors. In previous reports, a weak non-contact electric field stimulation (nEFS) accelerates the cell migration as well as cell-to-cell coupling between neuronal cell junction which are accompanied by increasing of cytoskeletal proteins [4, 5]. In this paper, we further investigated the wound
healing effect of the nEFS in the neuronal cells (SHSY5Y cells) with live cell optical imaging. Cells were
cultured over the optically transparent graphenen EF stimulator. Cellular behavioral changes upon nEFS were
recorded with live optical imaging during stimulation of 120 minutes. The ability of wound healing was
significantly enhanced with the nEFS. In particular, nEFS significantly shorten the duration of wound healing
process. Moreover, after treating cells with cytochalasin D, a block polymerization of the actin filaments, the
nEFS significantly enhanced wound healing process of cytochalasin D treated neural cells as compared to the control neural cells. This study suggests that nEFS may provide an effective way to control neural cells repairing
process from cellular injury. Further mechanism study about the effect of nEFS on the wound healing may shed
new light on cellular behavior.
Parkinson’s disease (PD) is characterized by progressive dopaminergic cell loss in the substantianigra (SN)
and elevated iron levels demonstrated by autopsy and with 7-Tesla magnetic resonance imaging. Direct
visualization of iron with live imaging techniques has not yet been successful. The aim of this study is to visualize and quantify the distribution of cellular iron using an intrinsic iron hyperspectral fluorescence
signal. The 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of PD was established in SHSY5Y cells. The cells were exposed to iron by treatment with ferric ammonium citrate (FAC, 100 μM)
for up to 6 hours. The hyperspectral fluorescence imaging signal of iron was examined usinga high-
resolution dark-field optical microscope system with signal absorption for the visible/ near infrared
(VNIR) spectral range. The 6-hour group showed heavy cellular iron deposition compared with the small
amount of iron accumulation in the 1-hour group. The cellular iron was dispersed in a small, particulate
form, whereas extracellular iron was detected in an aggregated form. In addition, iron particles were
found to be concentrated on the cell membrane/edge of shrunken cells. The cellular iron accumulation readily occurred in MPP+-induced cells, which is consistent with previous studies demonstrating elevated iron levels in the SN in PD. This direct iron imaging methodology could be applied to analyze the
physiological role of iron in PD, and its application might be expanded to various neurological disorders involving other metals, such as copper, manganese or zinc.
In this study, an apertureless near-field scanning optical microscope-Raman spectroscopy system is constructed and the topography and Raman scattering image of carbon nano-materials are simultaneously measured with high spatial resolution by using a sharp Au tip. The Rayleigh scattering image, and Raman scattering image of the carbon nanotubes showed improved spatial resolution and enhanced scattering intensity owing to the optical antenna effect of Au tip.
Kyoung In Min, Ki Kang Kim, Myoung-Kyu Oh, Soo Bong Choi, Heesuk Rho, Ha Jin Lee, Kay Hyeok An, Young Chul Choi, Jong Hun Han, Kyung Hui Oh, Young-Hee Lee, Mun Seok Jeong
We investigated single wall carbon nanotubes (SWCNTs) synthesized by the HiPCO method and further processed with nitronium hexafluoroantimonate (NO2SbF6 : NHFA) treatment using continuous resonant Raman scattering in the range of 570-900 nm. According to the population ratio calculation results from Raman scattering data, it is obvious that semiconducting SWCNTs with small diameter and metallic SWCNTs were selectively removed by NHFA.
Carbon nanotubes (CNTs) can exist as clusters whenever doping amount in nematic liquid crystal (LC) mixture exceeds
critical point. Based on experimental observation of electric field-dependent shape of the CNT cluster, it elongates along
the field direction and its original morphology of the cluster is restored after the removal of the field. The elongation was
fully reversible only below a certain breakdown field. Both clusters and elongated CNTs were observed under nonpolarized
and polarized light. The cluster absorbs incident light completely while the elongated one absorbs light
propagating along the long axis only. Utilizing the field-controlled cluster, light modulation for display application is
possible.
We demonstrate doping-free and adaptive inverter to verify that the single ambipolar SWCNT transistors can be utilized both p- and n-type. Furthermore, we fabricate an adaptive logic circuit that can reveal multifunctions such as NOR and NAND gate using four ambipolar transistors. This new approach is innovative in several aspects, for instance, in improving integration density, simplicity without intentional doping, and its multifunctionality and ensures multidisciplinary interests in materials, physics, mechanics, and electronics areas.
The effect of using EBL with devices incorporating CNT has also been investigated. The effect on metallic and
semiconducting CNT exposure in the channel of the transistor devices was examined and a physical mechanism for the
variations discussed. We show that the subsequent generation of trap states along the CNT channel varies the conduction
mechanism of the nanotube and has a significant effect on device performance. Metallic and semiconducting CNT react
very differently, with an apparent increased localization effect in the metallic tubes responsible for dramatic decreases in
conductance.
Nanodispersion of single-walled carbon nanotubes (SWCNTs) has been systematically investigated with the use of
sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) surfactant in de-ionized water. A high concentration of
nanodispersed SWCNTs up to 0.08 mg/mL was achieved with introduction of an additional dispersant of PVP by
optimizing surfactant concentration, sonication time, and centrifugation speed, which was crucial to obtaining a high
concentration of SWCNTs in the supernatant solution. We also demonstrate that diameters of the nanodispersed
nanotubes can be sorted out by controlling the centrifugation speed and furthermore the saturated SWCNT concentration
was nearly constant, independent of the initial concentration at high centrifugation speed. Two dispersion states were
identified depending on the centrifugation speed: an intermediate dispersion of nanodispersion mixed with
macrodispersion (I) and nanodispersion (II). This was verified by Raman spectroscopy, scanning probe microscopy,
optical absorption spectroscopy, and photoluminescence measurements. The obtained SWCNT solution was stable up to
about ten days. Some aggregated SWCNT solution after a long period of time was fully recovered to initial state of
dispersion after re-sonication for a few minutes. Our systematic study on high concentration nanodispersion of SWCNTs
with selective diameters provides an opportunity to extend the application areas of high quality SWCNTs in large
quantity.
Seung Jin Chae, Fethullah Günes, Ki Kang Kim, Eun Sung Kim, Gang Hee Han, Soo Min Kim, Hyeon-Jin Shin, Seon-Mi Yoon, Jae-Young Choi, Min Ho Park, Cheol Woong Yang, Didier Pribat, Young Hee Lee
Highly crystalline few-graphene layers were synthesized on poly-nickel, Ni(111) and Ni-deposited substrates by
optimizing the mixing ratio of C2H2/H2 and C2H4/H2 and growth time. The hydrogen effect was investigated to minimize
defects and maintain uniformity of the synthesized few-layer graphenes. Using the optimized ratio of hydrogen and
acetylene mixture, few graphene layers with large sizes of up to 4 inches in diameter were also synthesized on Ni
evaporated Si substrate with different thicknesses and were transferred successfully onto PET film. We also found that
the wrinkles, different from inherent ripples, were formed in the graphene layer independent of the location of the grain
boundary of poly-Ni substrate and growth conditions. This was attributed to the formation of a step terrace followed by
the terrace bunching to result in higher wrinkles due to the thermal mismatch existing between Ni substrate and graphene
layers during thermal quenching. A sheet resistance of 233 Ω/sq was obtained at a transmittance of 65%.
Since it was isolated in 2004, graphene, the first known 2D crystal, is the object of a growing interest, due to the range of its possible applications as well as its intrinsic properties. From large scale electronics and photovoltaics to spintronics and fundamental quantum phenomena, graphene films have attracted a large community of researchers. But bringing graphene to industrial applications will require a reliable, low cost and easily scalable synthesis process. In this paper we present a new growth process based on plasma enhanced chemical vapor deposition. Furthermore, we show that, when the substrate is an oxidized silicon wafer covered by a nickel thin film, graphene is formed not only on top of the nickel film, but also at the interface with the supporting SiO2 layer. The films grown using this method were characterized using classical methods (Raman spectroscopy, AFM, SEM) and their conductivity is found to be close to those reported by others.
The properties of liquid crystal (LCs) can be altered by incorporating guest materials. The physical properties of carbon nano tubes doped liquid crystal (CNTs/LC) and pristine LC have been investigated. The rotational viscosity of CNTs/LC was lower whereas dielectric anisotropy was almost the same as compared to pristine LC. Also the twisted nematic LC cell driven by vertical field and homogeneously aligned nematic LC cells doped with carbon nanotubes (CNTs) driven by an in-plane field were fabricated and their electro-optic characteristics were investigated. The response time of CNTs doped LC was found to be improved due to the decrease in rotational viscosity.
Flexible transparent conducting films (TCFs) were fabricated on a PET substrate by various methods using carbon
nanotubes dispersed in organic or water-based solution. Thin multi-walled carbon nanotubes, double-walled carbon
nanotubes, and single-walled carbon nanotubes were used to compare the performance for TCFs. Optimal design rules
for types of nanotubes, surfactants, the degree of dispersion, and film preparation methods were discussed. The TCFs
were characterized by scanning electron microscopy, TGA, Raman, optical absorption spectra, and sheet resistance. The
dispersion of CNTs in water and in bisolvent has been tried. A simple acid treatment on the TCF film increased the
conductivity by about four times. Doping and functionalization techniques will be further introduced to improve the
conductivity of the film.
This work reports the elongation and subsequent dispersion of carbon nano tube (CNT) aggregates driven by the electric field in a liquid crystal (LC) medium. Longitudinal and cross sectional views of CNT aggregates were investigated in homogeneously aligned cell driven by in-plane field and homeotropic aligned cell, respectively. CNT aggregates firstly were aligned toward field line by dielectrophoretic torque and secondly they were elongated above a certain threshold field due to interaction between induced dipole moment and electric field. The CNTs aggregates elongated linearly with varying electric fields. The original morphology of the CNT aggregates was restored after the removal of the field. The evidence of a complete restoration indicated that the elasticity of CNT aggregates obeyed Hooke's Law. The elongation was fully reversible only below a certain breakdown field. Above breakdown electric field, CNT aggregates were ruptured and fragmented into small pieces and consequently CNTs got dispersed in LC medium.
Chandan Biswas, Seung Yol Jeong, Seong Chu Lim, Dong Jae Bae, Young Hee Lee, Hyun Jin Shin, Seon-Mi Yoon, Jae Young Choi, Ok Hwan Cha, Mun Seok Jeong, David Perello, Minhee Yun
CdSe/ZnS core/shell quantum dots have been decorated on thin multiwalled and singlewalled carbon nanotubes (CNTs)
by chemical functionalization and substrate gate-bias control. CdSe quantum dots were negatively charged by adding
mercaptoacetic acid (MAA). The silicon oxide substrate was decorated by octadecyltrichlorosilane (OTS) and converted
to hydrophobic surface. The negatively charged CdSe/ZnS NCs were adsorbed on the SWCNT surface by applying the
negative gate bias. The selective adsorption of CdSe/ZnS quantum dots on SWCNTs was confirmed by confocal laser
scanning microscope. Quantum dots decorated carbon nanotubes have been used for effective photogenaration and
carrier transport through the organic photovoltaic device which has fabricated using effective polymers. The results
clearly indicate the efficient photocurrent generation and carrier transport which effectively increased the efficiency of
the device for the next generation organic solar cell applications.
Recently, active researches on carbon Nanotube (CNT)-doped liquid crystal (LC) mixtures are progressing. Based on
experimental observations, CNTs are known to align parallel to the LC director and experience orientational deformation
associated with the LC deformation under an electric field. Theoretical calculation also shows that the LC is strongly
anchored on CNT in a way that the LC director is parallel to the CNT long axis. Many experimental results have been
reported regarding to CNT effects on electro-optic characteristics of the LC device such as threshold voltage, residual dc and
response time, and physical properties of a nematic LC such as rotational viscosity, dielectric anisotropy, elastic constants
and clearing temperature, although some are still controversial. In this talk, historical reviews as well as our achievements on
CNT-LC mixtures will be discussed.
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