Browsing by Author "Fang, Yueh-Yuan"

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Electrical properties of single and multiple poly(3,4-ethylenedioxythiophene) nanowires for sensing nitric oxide gas
(2009-04-27)
Lu, Hui-Hsin
;
Lin, Chia-Yu
;
Hsiao, Tzu-Chien
;
Fang, Yueh-Yuan
;
Ho, Kuo-Chuan
The electrical properties of conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), nanowires were studied to develop nitric oxide (NO) gas sensors with low working temperatures. A nanowire with a diameter of 300 nm was fabricated using dip-pen nanolithography (DPN) across a 55 mu m gap between a pair of electrodes. The electrical properties of single or multiple PEDOT nanowires were examined by plotting the current-voltage (I-V) curves in the range -3 V to +3 V at temperatures between 298 K and 393 K. The conductance of parallel wires was normalized with respect to the dimensions of the fabricated nanowires. The single nanowire exhibited nonlinear conductance associated with hysteresis but multiple wires did not. The currents increased with the temperature and the I-V characteristics were consistent with the power lawG(T)alpha T(alpha) with alpha similar to 5.14 and 5.43. The responses to NO were highly linear and reproducible, indicating that sensing using PEDOT nanowires was reliable with a minimal concentration of NO of 10 ppm. (c) 2009 Elsevier B.V. All rights reserved.
Monitoring Biomolecular Interaction with 1-D Plasmonic Nanostructure by Using Dark Field Microscopy
(2009)
Lu, Hui-Hisn
;
Lin, Chii-Wann
;
Fang, Yueh-Yuan
;
Hsiao, Tzu-Chien
;
Hsu, Su-Ming
This study presents an imaging technique combining multi-functional dark field microscopy (DFM) with spectroscopy to image the nanostructures of different formats of optical disks and identify their optical properties by absorption spectra. The resolution of this DFM system is determined using one-dimension nanostructure with lengths from 160 nm to 600 nm. The pattern sizes are confirmed by atomic force microscopy (AFM). The results show that DFM resolution is about 160 nm with the current setup, and the resulting DFM image size appears to be slightly larger than a AFM image. We then deposited a 50 nm gold film on top of these nanostructures and measured their absorption spectra to identify the relationship between surface plasmon resonance (SPR) spectra and one-dimensional nanostructures. The immobilization of streptavidin on the surface of the gold-coated nanostructure causes changes in the absorption spectrum ranging from 450nm to 650nm.
NO Gas Sensor of PEDOT: PSS Nanowires by Using Direct Patterning DPN
(2008)
Lu, Hui-Hisn
;
Lin, Chia-Yu
;
Fang, Yueh-Yuan
;
Hsiao, Tzu-Chien
;
Ho, Kuo-Chuan
Nitric oxide (NO) detection is a critical issue for environmental safety and medical diagnosis due reasons with regard to the toxic properties for human body and metabolic index for respiratory disease, respectively. Development of gas sensor with high sensitivity is very important because the concentration of NO gas in the environment and respiratory tract is extremely low, therefore not readily detectable. The material with nanostructure can improve the sensitivity of sensor owning to surface effect and size effect. Herein, we developed a new type of gaseous nanosensor assembled by 34 nanowires of conducting polymer, PEDOT: PSS. The nanowires were fabricated by dip pen nanolithography (DPN) with the length of 55 um and diameter of 300 nm between golden wires. The NO gas measurement is based on chemiresistor based methods. The result of dynamic measurement of NO gas at 100 ppm shows repeatability and stability; the recovery time is 10.4 minutes. Moreover, the lowest concentration of NO gas in static measurement is 10ppm at 80 C, which also shows the ability sensing at low temperature.