Tuning the gas sensing performance of single PEDOT nanowire devices

Hangarter, Carlos M.,Hernandez, Sandra C.,He, Xueing,Chartuprayoon, Nicha,Choa, Yong Ho,Myung, Nosang V. Royal Society of Chemistry 2011 The Analyst Vol.136 No.11

<P>This paper reports the synthesis and dopant dependent electrical and sensing properties of single poly(ethylenedioxythiophene) (PEDOT) nanowire sensors. Dopant type (<I>i.e.</I> polystyrenesulfonate (PSS<SUP>−</SUP>) and perchlorate (ClO<SUB>4</SUB><SUP>−</SUP>)) and solvent (<I>i.e.</I> acetonitrile and 1 : 1 water–acetonitrile mixture) were adjusted to change the conjugation length and hydrophilicity of nanowires which resulted in change of the electrical properties and sensing performance. Temperature dependent coefficient of resistance (TCR) indicated that the electrical properties are greatly dependent on dopants and electrolyte where greater disorder was found in PSS<SUP>−</SUP> doped PEDOT nanowires compared to ClO<SUB>4</SUB><SUP>−</SUP> doped nanowires. Upon exposure to different analytes including water vapor and volatile organic compounds, these nanowire devices displayed substantially different sensing characteristics. ClO<SUB>4</SUB><SUP>−</SUP> doped PEDOT nanowires from an acetonitrile bath show superior sensing responses toward less electronegative analytes and followed a power law dependence on the analyte concentration at high partial pressures. These tunable sensing properties were attributed to variation in the conjugation lengths, dopant type and concentration of the wires which may be attributed to two distinct sensing mechanisms: swelling within the bulk of the nanowire and work function modulation of Schottky barrier junction between nanowire and electrodes.</P> <P>Graphic Abstract</P><P>A “tailored-made”-made single PEDOT nanowire gas sensor which displays unique gas sensing behavior due to doping and structural differences arising from electropolymerization conditions. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0an01000f'> </P>

Nanopeapods by Galvanic Displacement Reaction

Hangarter, Carlos M.,Lee, Young‐,In,Hernandez, Sandra C.,Choa, Yong‐,ho,Myung, Nosang V. WILEY‐VCH Verlag 2010 Angewandte Chemie Vol.122 No.39

<P><B>Eine universelle Strategie</B>: Durch galvanische Verdrängung wurden mehrsegmentige Nanodrähte bei Raumtemperatur in Nanoschoten überführt (siehe Schema). Abhängig vom Redoxpotential des Verdrängungsvorgangs ließen sich verschiedenste Materialien erzeugen, z. B. Halbleiter/Metall‐, p/n‐, Metall/Metall‐ und ferromagnetische/nichtmagnetische Komposite.</P>

Electrodeposition of Magnetic and Hybrid Organic/Magnetic Nanowires

Carlos Hangarter,Youngwoo Rheem,Bongyoung Yoo,Nosang Myung 한국표면공학회 2008 한국표면공학회 학술발표회 초록집 Vol.2008 No.-

Site-Specific Magnetic Assembly of Nanowires for Sensor Arrays Fabrication

Rheem, Y.,Hangarter, C.M.,Eui-Hyeok Yang,Deok-Yong Park,Myung, N.V.,Bongyoung Yoo IEEE 2008 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.7 No.3

<P>The effect of variation in local magnetic field on magnetic assembly of 30 and 200 nm diameter Ni nanowires synthesized by template directed electrodeposition was investigated with different materials (Ni-Ni and Ni-Au) and shapes of electrodes. Ni-Au paired electrodes improved confinement of the assembled Ni nanowires across the electrode gap because of the narrower distribution of magnetic field around the gap between the two electrodes. Simulation results indicated a local magnetic field strength at the electrode tip increased by a factor of 2.5 with the use of a needle-shape electrode as compared to rectangular- shape electrode. The resistance of nanowire interconnects increased as the applied voltage was raised, and under the same applied voltage, the increase in resistance is further enhanced at lower temperatures because of higher current density.</P>

Magnetically Assembled Multisegmented Nanowires and Their Applications

Bangar, Mangesh A.,Hangarter, Carlos M.,Yoo, Bongyoung,Rheem, Youngwoo,Chen, Wilfred,Mulchandani, Ashok,Myung, Nosang V. WILEY-VCH Verlag 2009 Electroanalysis Vol.21 No.1

<P>Here we report a cost effective and versatile way of synthesizing and assembling multi-functional (e.g., gold-polypyrrole-nickel-gold) nanowires. Multisegmented nanowires were synthesized using electrodeposition method for precise control over segment dimensions for proper expression of material functionality. The nanowires were integrated on microfabricated electrodes using magnetic dipole interactions between the ferromagnetic segment in the nanowire and the ferromagnetic electrodes. The electrical properties of multisegmented nanowires showed semiconducting behavior with the activation energy of ca. 0.27 eV for the conducting polymer segment of the nanowire. These nanowire devices showed response towards light and exposure to ammonia, demonstrating their potential use as photonic device and gas sensor, respectively.</P>

Template-Directed Electrodeposition of Iron-Palladium Nanowires and Their Electrical Transport and Sensing Properties

Herná,ndez, S. C.,Hangarter, Carlos,Kim, Jong Ryoul,Choa, Yong-Ho,Myung, N. V. The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.14

<P>Template-directed electrodeposition was utilized to fabricate FexPd1-x nanowires where the dimension was controlled by template pore size (i.e., 30 and 200 nm) whereas the composition was tuned by varying the Fe+2/Pd+2 metal ion ratio in ammonium chloride baths at fixed deposition current density of 5 mA cm(-2). A wide range of composition (i.e., Pd-rich, near equiatomic, and Fe-rich) were successfully fabricated and their magnetic properties were examined. Additionally, single nanowire was also integrated on to microfabricated gold electrodes by magnetic alignment, followed by post-annealing in a reducing environment to make good electrical contacts. Assembled single nanowire was utilized to determine their electrical transport properties including temperature-dependent resistance (TCR) and magnetoresistance (MR). Additionally, the feasibility of FexPd1-x nanowire based hydrogen sensor was examined at room temperature. (c) 2017 The Electrochemical Society.</P>

Magneto-Transport Studies of Single Ferromagnetic Nanowire

Y. Rheem,B.-Y. Yoo,C. Hangarter,W. P. Beyermann,N. V. Myung 한국자기학회 2007 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Root Gravitropic Response of Phytochrome Mutant ( phyAB) in Arabidopsis

Soon Hwa Woo(우순화),Seung-Eun Oh(오승은),Jong Sik Kim(김종식),Jack L. Mullen,Roger P. Hangarter,Soon Young Kim(김순영) 한국생명과학회 2008 생명과학회지 Vol.18 No.2

Arabidopsis의 피토크롬 2중 돌연변이형 (phyAB)은 야생형 (WT)과 비교하여 뿌리의 굴중성 반응이 지연되었다. 중력 자극을 받은 지 8시간 후에 돌연변이체의 굴중성 반응은 야생형의 48%를 나타내었다. 지연된 반응은 중력자극을 준 후 1.5 시간 뒤에 나타났다. 12시간 동안 야생형과 돌연변이형의 뿌리 절편에서 에틸렌 생성을 측정하였다. 돌연변이형의 에틸렌 생성은 12시간이 경과한 후에 야생형의 40% 정도로 감소되었다. 이러한 결과는 피토크롬이 에틸렌 생성과 연관되어 있음을 제시하고 있다. 일반적으로 에틸렌은 식물의 뿌리나 줄기를 억제한다. 본 연구에서는 에틸렌 전구체인 1-aminocycloprpane-1-carboxylic acid (ACC)를 처리하여 뿌리의 생장을 측정하였다. 야생형은 ACC 존재하에 뿌리 생장이 억제되었으나, 돌연변이형은 야생형만큼 억제를 나타내지 않았다. 이 결과를 확인하기 위하여 ACC 존재 하에 굴중성 반응을 측정한 결과, 야생형은 ACC가 없는 경우와 비교하여 37.4%의 억제를 나타냈으나, 돌연변이형은 ACC가 없는 경우와 비교하여 6.6%만을 억제하였다. 이 결과는 피토크롬이 에틸렌 생성을 통하여 뿌리 굴중성 반응을 조절한다는 것을 제시한다. Phytochrome double mutant (phyAB) showed the delayed root gravitropic response compared to the wild type (WT) in Arabidopsis. After 8 hr of gravistimulation, the gravitropic response of mutant showed 48% of the WT. The delayed response started at 1.5 hr after gravistimulation. And we measured the ethylene production in the root segments of WT and mutant for 12 hr. Ethylene production of mutant decreased about 40% of the WT at 12 hr. This result suggested that the phytochrome might be linked with ethylene production in some way. Generally, ethylene inhibits the growth of plant organs including roots. We measured the root growth rate in the presence of ACC (1-aminocyclopropane-1-carboxylic acid), a precursor of ethylene. And WT showed the inhibition of root growth with ACC, but mutant did not show the inhibition as WT did. To confirm the relationship between the ethylene and gravitropic response, we measured the gravitropic response with ACC. In the presence of 10-6 M ACC, WT showed the 37.4% inhibition compared to the control (no ACC), whereas mutant showed the only 6.6% inhibition of control (no ACC). This research suggested the relationship between phytochrome and gravitropic response through an ethylene production.