Plasma Ion Irradiation Research Articles

Modification of Carbon Fiber Surface under Plasma Ion Irradiation with Energies from Hundreds of eV to Tens of keV

Modification of Carbon Fiber Surface under Plasma Ion Irradiation with Energies from Hundreds of eV to Tens of keV

Nitrogen plasma modified CVD grown graphene as counter electrodes for bifacial dye-sensitized solar cells

In this study, we report modification of few-layer graphene grown by chemical vapour deposition via nitrogen plasma ion irradiation and its application as counter electrodes in bifacial dye-sensitized solar cells (DSSCs). The incorporation of nitrogen (N) atoms and defects are confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. Electrochemical impedance spectroscopy measurement reveals that the charge transfer resistance of graphene for triiodide reduction shows a decrease with increasing plasma treatment time, which is attributed to the increase of catalytic sites. The energy conversion efficiency of 3.12% is obtained when using the N-doped graphene films as counter electrodes, which is nearly 3 times higher than that of the pristine graphene films in DSSCs. More importantly, the DSSCs based on N-doped graphene CEs show much higher ηrear/ηfront ratio and better long-term stability than that based on Pt CEs. These results reveal the promising potential of this transparent N-doped graphene CEs in low cost and effective bifacial DSSCs.

Nitrogen-atom endohedral fullerene synthesis with high efficiency by controlling plasma-ion irradiation energy and C60 internal energy

The nitrogen-atom endohedral fullerene (N@C60) has been synthesized by controlling the plasma ion irradiation energy (Ei) and fullerene (C60) behavior in the sublimation phase. We examined the relationship between the synthesis purity of N@C60 [molar concentration ratio of N@C60 to pristine fullerene (C60)] and Ei, which was controlled by changing the substrate bias voltages (Vsub) and gas pressure (PN2) during the plasma irradiation process. High-density nitrogen-molecular ions (N2+) with a suitable Ei near 80 eV are confirmed to be the optimum condition of the nitrogen plasma for the synthesis of high-purity N@C60. In addition, high sublimation of C60 contributes to a higher yield due to the high internal energy of C60 and the related cage defects that are present under these conditions. As a result, a purity of 0.83% is realized for the first time, which is almost two orders of magnitude higher than that using other methods.

Powder modification under influence of heat, electric field and particle irradiation

Influence of heat, electric field and particle irradiation of powders of boron and tungsten are presented and discussed in the paper. It is shown that the particles of both powders are emitted from their surface when electric field applied normally to the powder surface exceeds some minimal magnitude. Simultaneous influence of electric field and irradiation by hydrogen- and argon plasma ions or by hydrogen atoms activates particle emission at the temperatures <1300K. Hydrogen- and argon plasma ion irradiation in the temperature range 1300–1800K stimulates a succession of powder modifications with the increase of powder temperature and power of ion irradiation.Driving forces and processes of powder modifications were found to be electric field forces, irradiation enhanced diffusion, interatomic forces, surface tension, sputtering by ion irradiation and ion induced stresses in the newly formed uniform layers.

Control of nanoparticle synthesis using physical and chemical dynamics of gas–liquid interfacial non-equilibrium plasmas

Plasmas generated in contact with liquids have attracted considerable attention as a novel reactive field in nano-biomaterial creation because the brand-new chemical and biological reactions are yielded at the gas–liquid interface, which are induced by the physical actions of the non-equilibrium plasmas. Highly ordered periodic structures of gold nanoparticles (AuNPs) are formed by transcribing the plasma structure to the surface of the liquid, where the spatially selective synthesis of the AuNPs is realized. Furthermore, the plasma structure is controlled using a ring or disk electrode under strong magnetic fields up to 4 T. The ring structure of the nanoparticles is found to be formed in accordance with the shadow region of the ring electrode. It is found that the AuNPs are synthesized by the reduction effect of the hydrogen radical via irradiation of neutral radicals of the plasma and are destroyed by the oxidation effect of the fluorine radical via high-energy plasma-ion irradiation.

Creation of Nanoparticle–Nanotube Conjugates for Life-Science Application Using Gas–Liquid Interfacial Plasmas

Gold nanoparticles (AuNPs) conjugated with carbon nanotubes (CNTs) and/or biomolecules such as DNA are synthesized by a novel plasma technique combined with the introduction of ionic liquids or aqueous solutions for application to life sciences. We successfully generated the gas–liquid interfacial discharge plasma (GLIDP) using an ionic liquid, in which a large sheath electric field was formed on the ionic liquid and high-energy plasma ion irradiation to the ionic liquid was realized. Using this GLIDP, it is found that the high-energy ion irradiation to the ionic liquid is effective for the synthesis of AuNPs. Furthermore, controlled ion irradiation to the ionic liquid including functional groups can realize distance-controlled synthesis of AuNPs on CNTs by dissociation of the ionic liquid and the functionalization of CNTs by dissociated carboxyl and amino groups. On the other hand, DNA is used as the functional group that connects the AuNPs to the CNTs. Monodispersed and high-density AuNPs are synthesized on CNTs in the same way as the carboxyl and amino groups.

Creation of Novel Nano-Bio Conjugates for Life Sciences Using Gas-Liquid Phases Plasmas

ABSTRACTThe gold nanoparticles (AuNPs) conjugated with carbon nanotubes (CNTs) and/or biomolecules such as DNA are synthesized using a novel plasma technique combined with introduction of ionic liquids or aqueous solution for application to life sciences.First, we successfully generate the gas-liquid interfacial discharge plasma (GLIDP) using an ionic liquid, in which the large sheath electric field is formed on the ionic liquid and the plasma ion irradiation to the ionic liquid with high energy is realized.Second, it is found that the high energy ion irradiation to the ionic liquid is effective for the synthesis of the AuNPs. Furthermore, the controlled ion irradiation to the ionic liquid including a carboxyl group can realize the density-controlled synthesis of the AuNPs on the CNTs by dissociation of the ionic liquid and the controlled functionalization of the CNTs by the dissociated carboxyl group.Third, the size- and morphology-controlled AuNPs covered with DNA are synthesized using the GLIDP with aqueous solution, where DNA prevents the AuNPs from further clustering, resulting in the small-sized AuNPs. The synthesized AuNPs conjugated with DNA can be encapsulated into the CNTs using the DC electric field. The CNTs work as vectors to deliver DNA into living cells because the CNTs have the unique ability to easily penetrate cell membranes with low cytotoxicity.

S055011 強磁場中の気液界面プラズマ流によるナノ粒子空間構造制御合成

Highly-ordered periodic structures of the gold nanoparticles (AuNPs) are formed by transcribing the plasma structure to the surface of the liquid, where the spatially selective synthesis of the AuNPs is realized. Furthermore, the plasma structure is controlled by using a ring or disk electrode under the strong magnetic fields up to 4 tesla. The ring structure of the nanoparticles is found to be formed in accordance with the shadow region of the ring electrode. It is found that the AuNPs are synthesize by the reduction effect of the hydrogen radical via irradiation of neutral radical of the plasma and are destroyed by the oxidation effect of the fluorine radical via high-energy plasma ion irradiation.

Electrical Transport Properties of C59N Azafullerene Encapsulated Double-Walled Carbon Nanotube

Electrical transport properties of double-walled carbon nanotubes (DWNTs) are modulated by encapsulating the azafullerene C59N which is synthesized via a plasma ion-irradiation method. The encapsulation of C59N molecules inside DWNTs has been confirmed by both transmission electron microscopy and Raman spectroscopy. The pristine DWNTs with outer diameter 4 - 5 nm are found to exhibit an ambipolar semiconducting behavior due to their small band gap. It is found that C60 fullerene encapsulated DWNTs exhibit a unipolar p-type semiconducting behavior. By comparison, C59N encapsulated DWNTs display an n-type semiconducting behavior. Our findings demonstrate that C59N operates as an electron donor compared with the acceptor behavior of C60, which is further clarified by photoelectron emission spectroscopy.

カーボンナノチューブ (CNT) を用いた抗原&amp;mdash;抗体センサの応用

An antigen-antibody sensor consisting of a silicon-based chip contains a mixture of poly [ethylene glycol] (PEG)-grafted carbon nanotubes (PEG-CNTs) and CNTs modified with an antigen by using plasma ion irradiation (plasma activation) method, is developed. According to result of experiments, impedance increased due to antigen/antibody reaction. The results indicate that this antigen-antibody sensor could react until 10 g/ml antigen density.

Novel Gas‐Liquid Interfacial Plasmas for Synthesis of Metal Nanoparticles

AbstractSpatially and temporally stable gas‐liquid interfacial plasmas are created using ionic liquids as electrodes of a direct‐current (DC) discharge under a low gas pressure condition. The potential structure formation in the gas‐liquid interfacial region and the resultant behavior of the plasma ions are revealed by changing a polarity of the electrode in the liquid. When the ionic liquid is utilized as a cathode electrode, the positive ions in the plasma are irradiated to the ionic liquid and cause the physical and chemical reactions of the ionic liquid at the interface. The plasma ion irradiation can easily be controlled by changing the plasma parameter and is found to be effective for the metal nanoparticle synthesis in comparison with an electron irradiation.magnified image

Gas–liquid interfacial plasmas: basic properties and applications to nanomaterial synthesis

A boundary between plasmas and liquids, which activates physical and chemical reactions, has successfully been generated under a low gas pressure condition by utilizing ionic liquids with unique properties such as fully ionized plasma state, extremely low vapor pressure and high heat capacity. Due to the formation and control of a sheath electric field just above the ionic liquid, the plasma-ion behavior can be manipulated and the effects of the ion irradiation on the ionic liquid are quantitatively revealed. In connection with the plasma-ion irradiation, the secondary electron emission is found to be enhanced by introducing the ionic liquid as a cathode electrode. The control of the plasma-ion irradiation flux and energy to the ionic liquid leads to the creation of various kinds of metal nanoparticles by the reduction in metal chlorides and the realization of efficient synthesis. Furthermore, the metal nanoparticles are synthesized with carbon nanotubes as a template in the ionic liquid using the plasma irradiation method. It is found that the high density, mono-dispersed and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas–liquid interfaced plasmas.

カーボンナノチューブ（CNT）を用いた抗原&amp;mdash;抗体センサの研究

An antigen-antibody sensor consisting of a silicon-based chip contains a mixture of poly[ethylene glycol] (PEG)-grafted single-walled carbon nanotubes (PEG-SWCNTs) and SWCNTs modified with an antigen by using plasma ion irradiation (plasma activation) method , was developed. According to X-ray photoelectron spectroscopy (XPS) analysis, peaks which correspond to CO and COOH radicals increased in impedance due to BSA/anti-BSA binding. The results of this study indicate that this antigen-antibody sensor reacts with a quick response time.

Liquid-Gas Interfacial Plasmas for the Formation of Novel Nanobiomaterials

The liquid–gas interfacial region, which is the boundary between plasmas and liquids, activates physical and chemical reactions, thus attracting much attention as a novel reactive field in nanobiomaterial creation. Owing to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we successfully created a reactive liquid–gas (ionic liquids–plasmas) interfacial field under a low gas pressure condition, in which the plasma ion behavior can be controlled. The effects of plasma ion irradiation on the liquid medium are for the first time revealed quantitatively. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the liquid–gas interfacial plasma were investigated by changing the polarity of the electrode in the liquid to evaluate liquid–plasma interactions. These results may contribute to systematizing the field of liquid–gas interfacial plasma physics for certain applications. Furthermore, novel nanobiocomposite materials, such as DNA-encapsulated carbon nanotubes, were formed using liquid-phase plasma, and for the first time, modifications of the electrical properties of nanocarbons according to the types of encapsulated DNA were demonstrated.

Chemical Modification of Carbon Nanotube Based Bio-Nanosensor by Plasma Activation

Chemical modification with plasma ion irradiation (plasma activation) is demonstrated on a bio-nanosensor based on poly(ethylene glycol)-grafted single-walled carbon nanotubes (PEG-SWNTs). By X-ray photoelectron spectroscopy (XPS) analysis, peaks that correspond to CO and COOH radicals are observed. In addition, the evaluation of the characteristic responses of the bio-nanosensor using a bovine serum albumin (BSA) antigen or oligonucleotide reveals an increase in impedance due to an antigen–antibody reaction or oligonucleotide hybridization. From these results, the bio-nanosensor is found to react with a short response time (60 s).

Synthesis and electronic-property control of Cs-encapsulated single- and double-walled carbon nanotubes by plasma ion irradiation

The synthesis of Cs-encapsulated single-walled carbon nanotubes (Cs@SWNTs) and double-walled carbon nanotubes (Cs@DWNTs) is realized by a plasma ion-irradiation method. Transmission electron microscopy observations confirm that chainlike and amorphous Cs fill SWNTs and DWNTs, respectively. The electronic transport properties of Cs@SWNTs and Cs@DWNTs are experimentally investigated at both room and low temperatures by fabricating them as the channels of field-effect transistor devices. Our results reveal that both Cs@SWNTs and Cs@DWNTs exhibit n-type semiconducting behavior at room temperature. The electronic properties of the Cs-encapsulated nanotubes can be controlled by adjusting the Cs filling levels during the plasma ion irritation process. At low temperatures, Coulomb blockade transport characteristics are observed for both encapsulated nanotubes, and the size of quantum dots formed in Cs@DWNTs is much smaller than that formed in Cs@SWNTs. More importantly, the n-type characteristics of Cs@SWNTs and Cs@DWNTs are found to remain stable, even in air, owing to Cs encapsulation.

N-type and p-type double-walled carbon nanotube field-effect transistors based on charge-transfer modulation

Electrical transport properties of double-walled carbon nanotubes (DWNTs) are modulated by encapsulating alkali-metal Cs atom or C60 molecules via a plasma ion-irradiation method. The pristine DWNTs are found to exhibit ambipolar semiconducting behavior due to their small bandgap. In contrast, Cs and C60 encapsulated DWNTs exhibit high performance unipolar n-type and p-type semiconducting behavior since they can operate as an electron donor and acceptor, respectively. Moreover, by controlling the filling level, p–n junction is found to be formed in DWNTs by Cs encapsulation. Our results indicate that DWNTs have great potential as building blocks for various electronic nano devices.

Ion irradiation effects on ionic liquids interfaced with rf discharge plasmas

The availability of plasma ion irradiation toward a gas-liquid interface is investigated in a rf discharge system incorporating an ionic liquid. The introduction of the ionic liquid to the plasma causes the formation of a sheath electric field on the ionic liquid surface, resulting in the acceleration of the ions to the ionic liquid and the generation of secondary electrons from the ionic liquid by the ion irradiation. These effects are found to advance the discharge process and enhance the plasma production.

DNA Encapsulation Inside Carbon Nanotubes Using Micro Electrolyte Plasmas

AbstractDNA encapsulated carbon nanotubes are formed using a plasma ion irradiation method in electrolyte solutions with DNA, which can be regarded as electrolyte plasmas from the view point that the electrolyte solutions consist of positive and negative ions, and neutral particles in the same way as gas phase plasmas. When both the direct current (DC) and radio frequency (RF) electric fields are applied to the DNA electrolyte plasmas through micro gap electrodes, DNA which is negatively charged in solutions tends to change its conformation from random‐coil to stretched‐form by the RF field and be irradiated to the carbon‐nanotube coated anodeelectrode by the DC field. Based on Raman spectroscopy and transmission electron microscopy analyses, DNA is confirmed to be inserted into the carbon nanotubes. The creation of DNA encapsulated carbon nanotubes using the micro electrolyte plasmas supports the validity of the plasma concept extended from gas to liquid phase, which could pioneer novel applications in such nanoelectronics and biomedical fields. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Investigations of low-energy ion irradiation influence on glassy polymeric carbon

Glassy polymeric carbon (GPC), which is made from phenolic resins, has a high chemical inertness and is used as high temperature and radiation resistant coatings, as high temperature heat-exchangers, as well as a biomaterial in medicine for the manufacture of heart valves and prosthetic devices [G.M. Jenkins, D. Ila, H. Maleki, Mater. Res. Soc. Symp. Proc. 394 (1995) 181]. GPC is also used for the harsh environment of space, as well as for protective coating against extreme environments such as high temperature, highly ionizing radiation, as well as corrosive environments.In this work, we present the results of our investigation of the influence of the low-energy ion irradiation in glow-discharge plasma on GPC.Chemical changes in GPC prepared at 1000°C were studied using FTIR, micro-Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Porosity changes were monitored through introducing lithium from a molten LiCl salt into GPC and using the (p,α) nuclear reaction analysis (NRA) to measure Li concentration in treated GPC.