Gas Liquid Interfacial Plasmas Research Articles

Structure Controlled Nanoparticle Conjugates Synthesized by Gas-Liquid Interfacial Plasmas

A periodic structure of gold nanoparticles (AuNPs) is formed by reducing a solution of gold chloride using novel plasma techniques, where a spatio-periodically generated plasma is transcribed to the AuNP structure formed on the ionic liquid (IL) surface under the strong magnetic field. In addition, it is found that a ring-shaped AuNP structure is formed corresponding to the shape of a ring electrode inserted into the plasma, where the AuNPs are synthesized at the position without plasma irradiation due to the shielding by the ring electrode. On the other hand, the periodic structure of the AuNPs are synthesized on the carbon nanotubes (CNTs) working as a template, where the controlled ion irradiation to the IL including functional groups can realize the distance-controlled synthesis of the AuNPs by dissociation of the IL and the functionalization of the CNTs by the dissociated carboxyl and amino groups. Furthermore, DNA is used as the functional group which connects the AuNPs to the CNTs. The mono-dispersed and high-density AuNPs are synthesized on the CNTs in the same way as the carboxyl and amino groups.

(Invited) Controlled Functionalization of Carbon Nanotubes with Nanoparticles Using Gas-Liquid Interfacial Discharge Plasmas

A periodic structure of gold (Au) nanoparticles is formed by reducing an aqueous solution of gold chloride using novel plasma techniques, where the Au nanoparticles are synthesized on the carbon nanotubes (CNTs) working as a template or a spatio-periodically generated plasma is transcribed to the Au nanoparticle structure formed on the liquid surface under the strong magnetic field. In addition, it is found that a ring-shaped nanoparticle structure is formed corresponding to the shape of a ring electrode inserted into the plasma, where the nanoparticles are synthesized at the position without plasma irradiation due to the shielding by the ring electrode.

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

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

(Invited) Controlled Functionalization of Carbon Nanotubes with Nanoparticles Using Gas-Liquid Interfacial Discharge Plasmas

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Characterization of pulse-driven gas-liquid interfacial discharge plasmas and application to synthesis of gold nanoparticle-DNA encapsulated carbon nanotubes

Gas-liquid interfacial discharge plasmas are generated between ionic liquid and stainless steel electrodes, where a pulse power source is used to operate the discharges. The temporal evolution of the plasma is investigated as well as the spatial distribution of the plasma. The positive pulse discharge plasma can not be detected by a double Langmuir probe, which is attributed to the fast diffusion of the plasma toward the chamber wall due to its high positive potential. On the other hand, the negative pulse discharge plasma parameters can be measured and the density decreases with increasing the distance away from the ionic liquid electrode. The plasma is mostly an after-glow discharge plasma since the plasma density gradually decreases after the discharge in a long period. In addition, we synthesize gold nanoparticle-DNA encapsulated single-walled carbon nanotubes by superimposing a DC voltage to the pulse voltage.

Structural and reactive kinetics in gas–liquid interfacial plasmas

Basic physical and chemical processes in novel gas–liquid interfacial plasmas applicable to nano-bio conjugates creation are investigated, where the boundary between ionic liquids (ILs) and gas phase discharge plasmas plays a key role. First the electrostatic potential is found to be formed at the plasma–liquid interface, and the precise potential and density structures are clearly measured. Then gas–liquid discharge kinetics, namely the dynamic behaviors of ions and electrons, are clarified in gas pressures ranging from atmospheric to low pressures owing to the unique properties of the ILs. Finally kinetics of interface reactions such as IL dissociation promoted by the plasma irradiation through the electric field just above the IL are explored, which enables us to create innovative conjugates of carbon nanotubes and nanoparticles.

Plasma-synthesized single-walled carbon nanotubes and their applications

Plasma-based nanotechnology is a rapidly developing area of research ranging from physics of gaseous and liquid plasmas to material science, surface science and nanofabrication. In our case, nanoscopic plasma processing is performed to grow single-walled carbon nanotubes (SWNTs) with controlled chirality distribution and to further develop SWNT-based materials with new functions corresponding to electronic and biomedical applications. Since SWNTs are furnished with hollow inner spaces, it is very interesting to inject various kinds of atoms and molecules into their nanospaces based on plasma nanotechnology. The encapsulation of alkali-metal atoms, halogen atoms, fullerene or azafullerene molecules inside the carbon nanotubes is realized using ionic plasmas of positive and negative ions such as alkali–fullerene, alkali–halogen, and pair or quasipair ion plasmas. Furthermore, an electrolyte solution plasma with DNA negative ions is prepared in order to encapsulate DNA molecules into the nanotubes. It is found that the electronic and optical properties of various encapsulated SWNTs are significantly changed compared with those of pristine ones. As a result, a number of interesting transport phenomena such as air-stable n- and p-type behaviour, p–n junction characteristic, and photoinduced electron transfer are observed. Finally, the creation of an emerging SWNTs-based nanobioelectronics system is challenged. Specifically, the bottom-up electric-field-assisted reactive ion etching is proposed to control the chirality of SWNTs, unexplored SWNT properties of magnetism and superconductivity are aimed at being pioneered, and innovative biomedical-nanoengineering with encapsulated SWNTs of higher-order structure are expected to be developed by applying advanced gas–liquid interfacial plasmas.

Nano-Bio Fusion Science Opened and Created with Plasmas

Recent years have brought about a rapid rise in research on applications in biological and medical fields including cell and tissue inactivation, sterilization and disinfection, blood coagulation, therapy, surgery, pharmaceuticals, biosensing, and biochips by exploiting low-pressure, atmospheric-pressure, and solution plasma processes. Many of the basic constituent materials of biological organisms are nanometer-scale in size, thus presenting the possibility of a growing field of science and technology focused on a fusion between “bio” and “nano” mechanisms; we are now in the germinal stage of a new era of next-generation applied research in the biological and medical applications of nanocarbons typified by fullerenes and carbon nanotubes. In this context, the authors have proposed and implemented research utilizing nanoscopic processes in advanced gas, liquid, and gas-liquid interfacial plasmas, directed toward the creation of synthetic materials and devices composed of nanocarbons, nanoparticles, and biomolecules. This research is positioned to advance the establishment of nano-bio fusion science opened and created with plasmas to construct next-generation nanobio and medical systems relating to nanobio-electronics devices, intracellular nanoengineering, and nanomedicine.

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.