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Research

Palladium Single Nanowire Growth and Sensor and Hydrogen Sensor

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Palladium (Pd) has been widely used in hydrogen sensing and storage areas. Pd nanowire and arrays have been successfully utilized in high performance hydrogen sensors. By using electrochemical deposition, we are able to fabricate Pd single nanowires with sub-100 nm diameters inside PMMA nanochannels between Au electrodes. These nanowires can be subsequently integraged into sensor devices which are capable of 2-5 ppm hydrogen sensing yet with extremely low power consumption ~ 100 nW.

Nanowire growth


    

Figure: (a) A Pd nanowire with 150 nm diameter and 7 μm length. (b) A Pd nanowire with 80 nm diameter and 3 μm length.

Different nanowire structures


   

 

Figure: SEM images of Pd nanowire with (a) a grainy structure, (b) a plain structure, and (c) a hairy structure.

Hydrogen sensing:

We successfully integrated Pd single nanowires into hydrogen sensors and they are capable of sensing 2-5 ppm hydrogen in pure nitrogen gas under room temperature. These sensors showed good sensitivity, fast response time as well as reproducibility. The power consumption for these nanowires is on the order of a few hundred of nW.

 

Figure: A hydrogen sensing signal from Pd single nanowire. The resistance change of the nanowire results in a voltage signal change which can be recorded. Hydrogen with concentrations from 1000 ppm (0.1%) to 2 ppm (0.0002%) is detected periodically.

 

Patents

  1. Minhee Yun, Nosang Myung, and Richard Vasquez, “Controllable growth of individually addressable nanowires” NPO40221, Patent filed 06/12/03, non-provisional filed Minhee Yun and Nosang Myng, “In-situ Nanowire-based Gas Sensor Array” U.S. provisional patent, NPO-30900 (2003)

Article

  1. Minhee Yun, Nosang Myung, and Richard Vasquez, “In Situ Electrochemical Deposition of Microscopic Wires, NASA Tech Brief, p58, June (2005)

Papers

  1. Yushi Hu, David Perello, Usman Mushtaq, Minhee Yun, "Single Palladium Nanowire via Electrophoresis Deposition used as Ultra Sensitive Hydrogen Sensor", IEEE Transactions on Nanotechnology, 2008, in print
  2. Yushi Hu, "Single Palladium Nanowire: Synthesis Via Electrophoresis Deposition and Hydrogen Sensing", Master Thesis, University of Pittsburgh, 2008
  3. Yushi Hu, Usman Mushtaq, Minhee Yun, Palladium Nanowire-Based Gas Sensor for environmental Monitoring, The Mascaro Sustainability Initiative (MSI), 2007
  4. Minhee Yun, Nosang Myung, Richard Vasquez, “Nanowire Growth for Sensor Array”, Proc. of Nanotechnologies, SPIE 5220, 37(2003)
  5. Minhee Yun, Nosang Myung, and Richard Vasquez, “Electrochemically-Grown Wires for Individually Addressable Sensor Arrays”, Nano Letters, 4(3), 419(2004)
  6. Kumaran Ramanathan, Mangesh Bangar, Minhee Yun, Wilfred Chen, Ashok Mulchandani and Nosang V. Myung, “Individually Addressable Conducting Polymer Nanowires Array”, Nano Letters, 4(7), 1237(2004)
  7. Mangesh A. Bangar, Kumaran Ramanathan, Minhee Yun, Choonsup Lee, CarlosHangarter, Nosang V. Myung, “Controlled Growth of Single Palladium Nanowire between Microfabricated Electrodes”, Chemistry of Materials, 16, 4955(2004)
  8. K. Ramanathan, M. Bangar, M. Yun, W. Chen, A. Mulchandani, N. V. Myung, “Bio-receptor embedded single conducting polymer nanowire”, J. Am.
    Chem. Soc., 127, 496 (2005)
  9. Yeonho Im, Choonsup Lee, Richard P. Vasquez, Mangesh A. Bangar, Nosang V. Myung, Eric J. Menke, Reginald Penner, Minhee Yun*,
    “Investigation of a Single Pd nanowire for Use as a Hydrogen Sensor”, Small,
    2 (3), 356 (2006)

 

Polyaniline nanowires Single Nanowire Growth and Sensor

We are working to improve the quality of conducting Polyaniline (PANI) nanowires. They are fabricated individually in ~100 nm wide channels between gold electrodes using electrodeposition. This method has the benefit of controllability, reproducibility, versatiliy – since various materials can be utilized with the same process, addressability, and economical efficiency. Our grown nanowires are 100~150 nm wide and 1~5 um long with PANI. Their electrical conductivities are much higher – in the range of 4.20*103 3.33*10^4 S/cm. This is much better than the reported 2.13*10^3 S/cm of 220 um diameter micro PANI fibers. We are also investigating mechanical properties of PANI nanowires. After functionalization, the primary application for these NW’s is in high sensitive bio sensors.

Figure: The PANI nanowire on multiple electrodes. They are 139.6 nm wide, 118nm thick and 4 um long.

Figure: The concept design of the single PANI nanowire biosensor. It has multiple fuctionalized nanowire on FET structure and assembled system with microfluidic channel, data accumulation and analyzing system.

Figure: The Atomic Force Microscope (AFM) image of PANI nanowire

 

CNT devices

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Our CNT research centers on the development of new devices, as well as working towards better consistency required for nanotubes to be an acceptable commercial semiconductor alternative. We are working to differentiate contact and barrier characteristics of different metal contacts by holding as many fabrication parameters constant. The devices are fabricated utilizing T-CVD grown single wall nanotubes of long length (up to almost a centimeter, if desired). The ultimate goal is a fundamental understanding of mesoscopic contacts to CNT and other similar nanostructures. This project is performed in conjunction with Prof. Young Hee Lee’s CNT group at SKKU in Korea and Prof. Moon Kim’s group at UT Dallas.

Figure: AFM image of simple device with Hf electrodes separated by channel lengths ranging from 200 to 2 microns. The CNT is marked by black dots.

Using Micro and Nano structured Materials to Understand and Optimize Microbial Fuel Cell Performance

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Microbial fuel cells (MFC) are devices that convert chemical energy to electrical energy using the enzymatic reactions of microorganisms. Typically dual chamber MFCs consist of a bio-anode and a cathode separated by a cation exchange membrane.

MFCs typically generate lower efficiencies (conversion and potential efficiency) and energy production (current density) when compared to other types of fuel cells. However, the fact that MFCs operate at ambient temperature and pressure and could potentially be scaled to fit multiple environmental and medical applications shows technological promise.

To address the problem of low current production and efficiencies, many researchers have tried to improve MFC energy production by using anodes that have electrochemical catalysts deposited on the surface. For example Platinum (Pt) compounds such as Pt-polymer or Pt-metal alloys have been used to try to improve efficiencies because Pt is one of the most widely used and efficient electrochemical catalysts. Unfortunately the high costs of the catalysts and the understanding of its role within the bio-anode of MFCs are barriers to further development.

Figure: 1)microbial oxidation of the substrate (fuel), 2)electron transfer from the microbe to the anode, 3)elctron transfer through the circuit including external resistance, 4)proton diffusion from the anode compartment to the cathode compartment 5)oxygen supply and reduction at the cathode (cathode reaction), 6)oxygen diffusion into the anode compartment through the membrane.

 

Figure: SEM and AFM pictures of elements of biofuel cell

Figure: Current density when different types of electrodes are installed only on the anode (carbon paper electrode on the cathode in all the cases). Case 1 is for a carbon paper electrode without Pt,
case 2 is for a Pt- black electrode(150 nm), case 3 is for an e-beam Pt electrode (100 nm), and case 4 is for a commercial Pt electrode (250 nm).

 

Figure: Current density for cases 5 and 6. In case 5, the e-beam Pt electrode is installed on the anode while the carbon paper electrode is installed on the cathode prior to reaching 45 h.
In case 6, the commercial Pt electrode is installed on the anode while the carbon paper electrode is installed on the cathode prior to reaching 45 h. At 45 h, the carbon paper on the cathode is replaced with an e-beam Pt electrode (case 5) and a commercial Pt electrode (case 6).


Figure: The mass-specific current density that represents the current density per unit Pt thickness.
This figure was produced after dividing the current density in Figure 4 by the corresponding Pt thickness.

 

Papers

  1. Ho Il Park, Sung Kwon Cho, Minhee Yun. New bacterial communities of Aeromonas hydrophila consortia in a mediator-less microbial fuel cell. Applied Microbiology and Biotechnology (Submitted).
  2. Ho Il Park, Usman Mushtaq, Dave Perello, Innam Lee, Sung Kwon Cho, Alex Star, Minhee Yun. Effective and low cost platinum electrodes for microbial fuel cells deposited by electron beam evaporation. Energy & Fuels ,21, 2984- 2990, 2007.
  3. Chang In Seop, Hyunsoo Moon, Orianna Bretshger, Jae Kyung Jang, Ho Il Park, Kenneth H. Nealson, Byung Hong Kim. Electrochemically active bacteria (EAB) and mediator-less microbial fuel cells. Journal of Microbiology and Biotechnology, 16(2), 163-177, 2006.
  4. J. Wang, N. Myung, Minhee Yun, and H. Monbouquette, “Highly Sensitive Electroenzymatic Glucose Biosensor Fabricated with Porous Pt Black and Bundled Pt nanowire Electrodes", Journal of Electroanalytical Chemisry, 575, 139(2005).

Bolometer

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A bolometer can be used either as a detector for radiation or particles. In addition, bolometers are used to detect light in the far-infrared and mm-waves. In this research, we have fabricated and developed detectors using microelectromechanical system (MEMS) techniques for
HFI models. The use of MEMS techniques in this research has improved the fabrication process required for developing spider-web bolometer detectors. In order to produce detectors suitable for flight use, the fabrication process must give a high mechanical yield.

Figure: Single spider-web architecture with NTD Ge thermometer developed at JPL. Absorber metal thickness, diameter affect optical efficiency, internal time constant, and chip location affects
internal time constant. Moreover, lead thickness affects thermal conductivity, while support legs increase device strength.

 

Bolometer Array

Figure: A 153 Bolometer Array developed at JPL using MEMS technique. It has a 153 free-standing spider webs on a 4 inch Si wafer.

Papers

  1. Adam L. Woodcraft, Rashmi V. Sudiwala, Peter A. R. Ade, Matthew J. Griffin,Andrew E. Lange, James J. Bock, Minhee Yun, and Jeffrey W. Beeman, “Prediction the response of a submillimeter bolometer to cosmic rays”, Appl. Optics, 42(25), 5009(2003)
  2. Minhee Yun, James Bock, Henry Leduc, and Peter Day, “Fabrication of Antenna- Coupled Transition Edge Polarization-sensitive Bolometer Arrays, Nuclear Instruments and Methods in Physics Research, Section A (NIMA), 520, 487 (2004)
  3. Minhee Yun, Jamie Bock, Warren Holmes, and Andrew Lange, “Microfabrication of Silicon Nitride Micromesh Bolometric Detectors for the Planck, J. Vac. Sci. Tech,
    B22, 220(2004)
  4. C.L. Kuo, P. Ade, J.J. Bock, P. Day, A. Goldin, S. Golwala, M. Halpern, G. Hilton,
    W. Holmes, V. Hristov, K. Irwin, W.C. Jones, M. Kenyon, A.E. Lange, H.G. LeDuc, C.MacTavish, T. Montroy, C. B. Netterfield, P. Rossinot, J. Ruhl, A. Vayonakis, G.Wang, M. Yun, J. Zmuidzinas, “Antenna-Coupled TES Bolometers for The SPIDER Experiment”, Nuclear Instruments and Methods in Physics Research, Section A (NIMA), 559 (2), 608 (2006)
  5. Minhee Yun, James Bock, Mattew Keynon, Chao-Lin Kuo, Henry Leduc,Anthony Turner, and Moon J. Kim, “Fabrication of superconducting transition edge sensor based on Mo and Au bilayers", Nuclear Instruments and Methods in Physics Research, Section A (NIMA), 559 (2), 462 (2006)
  6. H.G. LeDuc, Matthew Kenyon, Peter K. Day, Minhee Yun and J.J. Bock, “Fabrication of antenna-coupled transition edge sensors for polarimeter applications", Nuclear Instruments and Methods in Physics Research Section A, 559(2), 459 (2006)

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