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Nanopipette exploring nanoworld
TAKAMITOMOHIDE,Park Bae Ho,Kawai Tomoji 나노기술연구협의회 2014 Nano Convergence Vol.1 No.17
Nanopipettes, with tip orifices on the order of tens to hundreds of nanometers, have been utilized in the fields of analytical chemistry and nanophysiology. Nanopipettes make nanofabrication possible at liquid/solid interfaces. Moreover, they are utilized in time-resolved measurements and for imaging biological materials, e.g., living cells, by using techniques such as scanning ion-conductance microscopy and scanning electrochemical microscopy. We have successfully fabricated ion-selective nanopipettes that can be used to identify targeted ions such as sodium and potassium in- and outside of living cells. In this review, we discuss the extent of utilization of nanopipettes in investigating the nanoworld. In addition, we discuss the potential applications of future nanopipettes.
Resistive-Switching Memory Effects of NiO Nanowire/Metal Junctions
Oka, Keisuke,Yanagida, Takeshi,Nagashima, Kazuki,Kawai, Tomoji,Kim, Jin-Soo,Park, Bae Ho American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.19
<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-19/ja101742f/production/images/medium/ja-2010-01742f_0003.gif'> <P>We have demonstrated the construction of highly stable resistive switching (RS) junctions with a metal/NiO nanowire/metal structure and used them to elucidate the crucial role of redox events in the nanoscale bipolar RS. The presented approaches utilizing oxide nanowire/metal junctions offer an important system and platform for investigating nanoscale RS mechanisms of various oxide materials.</P></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja101742f'>ACS Electronic Supporting Info</A></P>
Ion Current Oscillation in Glass Nanopipettes
Deng, Xiao Long,Takami, Tomohide,Son, Jong Wan,Kawai, Tomoji,Park, Bae Ho American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.28
<P>Ion currents detected by glass nanopipettes in solutions depended on the diameters of pipettes and ion species in the solutions. The ion current oscillation with frequency of 2.7 mHz was observed using the pipet with inner diameter of 50 nm in 0.1 M KCl solution. However, nonoscillatory currents were observed using the same pipet in 0.1 M KOH and HCl solutions or using pipettes with inner diameters of 15 nm, 500 nm, and 0.7 mm in 0.1 M KCl solution. Oscillation of the double layer thickness due to the change of ion concentration in the nanopipette perturbs the path of the ion current through the bulk layer, which results in the nonlinear current oscillation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-28/jp3014755/production/images/medium/jp-2012-014755_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp3014755'>ACS Electronic Supporting Info</A></P>
Naoya Mizutani,Tomohiro Iwasaki,Satoru Watano,Takeshi Yanagida,Tomoji Kawai 한국물리학회 2010 Current Applied Physics Vol.10 No.3
The size of magnetite nanoparticles was controlled by means of coexistence effects of anions in the starting solution of organic solvent-free hydrothermal synthesis via coprecipitation. As the coexisting anions,lactate ion, which forms relatively stable complex with ferric ion, and sulfate ion were used. The hydrothermal synthesis was carried out at various concentrations of lactate and sulfate ions. The obtained magnetite nanoparticles were characterized by a scanning electron microscope, transmission electron microscope, powder X-ray diffractometer, dynamic light scattering particle size analyzer and superconducting quantum interference device. The formation mechanism of magnetite nanoparticles in this system was investigated based on the experimental results. The coexisting anions remarkably influenced both formation of crystalline nuclei and dispersion stabilization of formed precipitates. The particle size depended strongly on the concentration of lactate and sulfate ions. It has been clarified that lactate ion has the effect to decrease the particle size and sulfate ion promotes the particle growth. By adjusting the concentration of lactate and sulfate ions properly as the operating factor, we could control successfully the particle size from 9.5 to 38.6 nm in median size.
Nanoarrays of tethered lipid bilayer rafts on poly(vinyl alcohol) hydrogels
Lee, Bong Kuk,Lee, Hea Yeon,Kim, Pilnam,Suh, Kahp Y.,Kawai, Tomoji Royal Society of Chemistry 2009 Lab on a chip Vol.9 No.1
<P>Lipid rafts are cholesterol- and sphingolipid-rich domains that function as platforms for signal transduction and other cellular processes. Tethered lipid bilayers have been proposed as a promising model to describe the structure and function of cell membranes. We report a nano(submicro) array of tethered lipid bilayer raft membranes (tLBRMs) comprising a biosensing platform. Poly(vinyl alcohol) (PVA) hydrogel was directly patterned onto a solid substrate, using ultraviolet-nanoimprint lithography (UV-NIL), as an inert barrier to prevent biofouling. The robust structures of the nanopatterned PVA hydrogel were stable for up to three weeks in phosphate-buffered saline solution despite significant swelling (100% in height) by hydration. The PVA hydrogel strongly restricted the adhesion of vesicles, resulting in an array of highly selective hydrogel nanowells. tLBRMs were not formed by direct vesicle fusion, although raft vesicles containing poly(ethylene glycol) lipopolymer were selectively immobilized on gold substrates patterned with PVA hydrogel. The deposition of tLBRM nano(submicro) arrays was accomplished by a mixed, self-assembled monolayer-assisted vesicle fusion method. The monolayer was composed of a mixture of 2-mercaptoethanol and poly(ethylene glycol) lipopolymer, which promoted vesicle rupture. These results suggest that the fabrication of inert nanostructures and the site-selective modification of solid surfaces to induce vesicle rupture may be essential in the construction of tLBRM nano(submicro) arrays using stepwise self-assembly.</P> <P>Graphic Abstract</P><P>A nanoarray of tethered lipid bilayer raft membranes was constructed by site-selective self-assembly with a DSPE-PEG-PDP/ME mixed SAM and the model raft vesicle rupture in the nanoimprinted PVA nanowell. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b809732a'> </P>
베타에스트라다이올 측정을 위한 나노웰 기반 엡타머 바이오센서 어레이 시스템
김연석(Yeon Seok Kim),정호섭(Ho Sup Jung),이혜연(Hea Yeon Lee),Tomoji Kawai,구만복(Man Bock Gu) 대한환경공학회 2004 대한환경공학회 학술발표논문집 Vol.2004 No.12
Aptamer는 단백질, 펩타이드, 지질 등과 같은 생분자 또는 크기가 작은 유기, 무기화학물질 등 다양한 표적물질에 대해 특이적으로 결합할 수 있는 ssDNA나 RNA를 말한다. 이러한 Aptamer는 항원항체반응과 같은 개념의 바이오센서 시스템의 도입이 가능하며 저렴한 가격으로 인공적으로 대량 생산할 수 있고 고정화 기술이 단백질 고정화에 비해 비교적 간단하고 열애도 보다 안정할 수 잇는 등 여러 가지 장점을 가지고 있어 aptamer를 이용한 새로운 affinity sensing system 연구가 진행되고 있다. 특별히 환경바이오모니터링 분야에 있어서 기존의 생분자를 타겟으로 하는 의료진단용 바이오센서 기술이나 Immunosensor 기술 등은 환경독성물질에 대한 항체를 생산하지 못하는 등의 어려움이 있어 환경분야로의 적용이 많은 제약을 가지고 잇다. 그러나 aptamer 기반 biosensing 기술은 이러한 제약들을 극복할 것으로 기대되고 있으며 칩기반 측정 시스템의 구축은 환경독성물질 탐지에 있어서 그 효율성을 보다 증대할 수 있을 것으로 기대된다.
Spatial Nonuniformity in Resistive-Switching Memory Effects of NiO
Oka, Keisuke,Yanagida, Takeshi,Nagashima, Kazuki,Kanai, Masaki,Kawai, Tomoji,Kim, Jin-Soo,Park, Bae Ho American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.32
<P>Electrically driven resistance change phenomenon in metal/NiO/metal junctions, so-called resistive switching (RS), is a candidate for next-generation universal nonvolatile memories. However, the knowledge as to RS mechanisms is unfortunately far from comprehensive, especially the spatial switching location, which is crucial information to design reliable devices. In this communication, we demonstrate the identification of the spatial switching location of bipolar RS by introducing asymmetrically passivated planar NiO nanowire junctions. We have successfully identified that the bipolar RS in NiO occurs near the cathode rather than the anode. This trend can be interpreted in terms of an electrochemical redox model based on ion migration and p-type conduction.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-32/ja206063m/production/images/medium/ja-2011-06063m_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja206063m'>ACS Electronic Supporting Info</A></P>