{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T06:54:27Z","timestamp":1776927267772,"version":"3.51.2"},"reference-count":27,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2014,9,2]],"date-time":"2014-09-02T00:00:00Z","timestamp":1409616000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this study, we investigate the keys to obtain a sensitive ammonia sensor  with high air stability by using a low-cost polythiophene diode with a vertical channel  and a porous top electrode. Poly(3-hexylthiophene) (P3HT) and air-stable  poly(5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene) (PQT-12) are both evaluated as the active sensing layer. Two-dimensional current simulation reveals that the proposed device exhibits numerous connected vertical nanometer junctions (VNJ). Due to the de-doping reaction between ammonia molecules and the bulk current flowing through the vertical channel, both PQT-12 and P3HT VNJ-diodes exhibit detection limits of 50-ppb ammonia. The P3HT VNJ-diode, however, becomes unstable after being stored in air for two days.  On the contrary, the PQT-12 VNJ-diode keeps an almost unchanged response to 50-ppb ammonia after being stored in air for 25 days. The improved storage lifetime of an  organic-semiconductor-based gas sensor in air is successfully demonstrated.<\/jats:p>","DOI":"10.3390\/s140916287","type":"journal-article","created":{"date-parts":[[2014,9,2]],"date-time":"2014-09-02T10:12:38Z","timestamp":1409652758000},"page":"16287-16295","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Achieving a Good Life Time in a Vertical-Organic-Diode  Gas Sensor"],"prefix":"10.3390","volume":"14","author":[{"given":"Ming-Zhi","family":"Dai","sequence":"first","affiliation":[{"name":"Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan"}]},{"given":"Yen-Ho","family":"Chen","sequence":"additional","affiliation":[{"name":"Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan"}]},{"given":"Ming-Yen","family":"Chuang","sequence":"additional","affiliation":[{"name":"Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan"}]},{"given":"Hsiao-Wen","family":"Zan","sequence":"additional","affiliation":[{"name":"Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan"}]},{"given":"Hsin-Fei","family":"Meng","sequence":"additional","affiliation":[{"name":"Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan"}]}],"member":"1968","published-online":{"date-parts":[[2014,9,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1016\/j.snb.2004.11.054","article-title":"Ammonia sensors and their applications\u2014A review","volume":"107","author":"Timmer","year":"2005","journal-title":"Sens. Actuators B Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2871","DOI":"10.1039\/b517953j","article-title":"Polymer sensors for nitroaromatic explosives detection","volume":"16","author":"Toal","year":"2006","journal-title":"J. Mater. Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1016\/j.jiec.2011.02.012","article-title":"Characteristics of the TiO2\/SnO2 thick film semiconductor gas sensor to determine fish freshness","volume":"17","author":"Jung","year":"2011","journal-title":"J. Ind. Eng. Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1002\/adma.201103334","article-title":"Organic thin-film transistors for chemical and biological sensing","volume":"24","author":"Lin","year":"2012","journal-title":"Adv. Mater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"797","DOI":"10.1557\/mrs2010.509","article-title":"Nanomaterials for cross-reactive sensor arrays","volume":"35","author":"Tisch","year":"2010","journal-title":"MRS Bull."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1080\/10408347.2011.521729","article-title":"Breath ammonia analysis: Clinical application and measurement","volume":"41","author":"Hibbard","year":"2011","journal-title":"Crit. Rev. Anal. Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"310","DOI":"10.1007\/s00216-005-0150-2","article-title":"Nanoscale organic and polymeric field-effect transistors as chemical sensors","volume":"384","author":"Wang","year":"2006","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"3859","DOI":"10.1002\/adma.200901136","article-title":"Reliability of organic field-effect transistors","volume":"21","author":"Sirringhaus","year":"2009","journal-title":"Adv. Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5088","DOI":"10.1063\/1.1691190","article-title":"Influence of moisture on device characteristics of polythiophene-based field-effect transistors","volume":"95","author":"Hoshino","year":"2004","journal-title":"J. Appl. Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"6416","DOI":"10.1002\/adma.201301337","article-title":"A novel thermally reversible soluble-insoluble conjugated polymer with semi-fluorinated alkyl chains: Enhanced transistor performance by fluorophobic self-organization and orthogonal hydrophobic patterning","volume":"25","author":"Jeong","year":"2013","journal-title":"Adv. Mater."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.orgel.2011.10.010","article-title":"Air stable complementary polymer circuits fabricated in ambient condition by inkjet printing","volume":"13","author":"Chen","year":"2012","journal-title":"Org. Electron."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Chabinyc, M.L., Street, R.A., and Northrup, J.E. (2007). Effects of molecular oxygen and ozone on polythiophene-based thin-film transistors. Appl. Phys. Lett., 90.","DOI":"10.1063\/1.2715445"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1153","DOI":"10.1002\/elan.200603527","article-title":"Electrochemically functionalized single-walled carbon nanotube gas sensor","volume":"18","author":"Zhang","year":"2006","journal-title":"Electroanalysis"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1016\/j.snb.2008.08.024","article-title":"Pt- and Pd-nanoclusters functionalized carbon nanotubes networked films for sub-ppm gas sensors","volume":"135","author":"Penza","year":"2008","journal-title":"Sens. Actuators B Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"7392","DOI":"10.1039\/c3an01209c","article-title":"Enhancing the sensitivity of chemiresistor gas sensors based on pristine carbon nanotubes to detect low-ppb ammonia concentrations in the environment","volume":"138","author":"Rigoni","year":"2013","journal-title":"Analyst"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/j.matlet.2013.02.117","article-title":"Porous spheres-like ZnO nanostructure as sensitive gas sensors for acetone detection","volume":"100","author":"Li","year":"2013","journal-title":"Mater. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Chen, G., Paronyan, T.M., Pigos, E.M., and Harutyunyan, A.R. (2012). Enhanced gas sensing in pristine carbon nanotubes under continuous ultraviolet light illumination. Sci. Rep., 2.","DOI":"10.1038\/srep00343"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"360","DOI":"10.1016\/j.snb.2012.09.081","article-title":"A high-sensitivity room-temperature hydrogen gas sensor based on oblique and vertical ZnO nanorod arrays","volume":"176","author":"Hassan","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3110","DOI":"10.1021\/ac303100k","article-title":"Highly sensitive ammonia sensor with organic vertical nanojunctions for noninvasive detection of hepatic injury","volume":"85","author":"Dai","year":"2013","journal-title":"Anal. Chem."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Vieira, S.M.C., Beecher, P., Haneef, I., Udrea, F., Milne, W.I., Namboothiry, M.A.G., Carroll, D.L., Park, J., and Maeng, S. (2007). Use of nanocomposites to increase electrical \u201cgain\u201d in chemical sensors. Appl. Phys. Lett., 91.","DOI":"10.1063\/1.2811716"},{"key":"ref_21","unstructured":"The P3HT VNJ-diode characteristics simulation is made based on the device structure shown in Figure 1b. The thicknesses P3HT and Al are 42.5 and 40 nm, respectively. The opening diameter is 200 nm. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of P3HT are 5.1 and 3.0 eV. The work functions of ITO and Al are 5.0 and 4.3 eV. The hole mobility and electron mobility in P3HT are 1 \u00d7 10\u22127 and 1 \u00d7 10\u221210 cm2\/V\u00b7s."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.snb.2010.02.019","article-title":"The response characteristics of a gas sensor based on poly-3-hexylithiophene thin-film transistors","volume":"146","author":"Jeong","year":"2010","journal-title":"Sens. Actuators B Chem."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"951","DOI":"10.1088\/0022-3727\/31\/8\/005","article-title":"Compensation behaviour of electrically conductive polythiophene and polypyrrole","volume":"31","author":"Mohammad","year":"1998","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1109\/JSEN.2007.913137","article-title":"Breath ammonia sensor based on conducting polymer nanojunctions","volume":"8","author":"Aguilar","year":"2008","journal-title":"IEEE Sens. J."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"293","DOI":"10.1016\/0021-9673(95)00470-X","article-title":"Langmuirian behaviour of smelly volatile organic compounds on air sampling with solid adsorbents","volume":"723","author":"Comes","year":"1996","journal-title":"J. Chromatogr. A"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3378","DOI":"10.1021\/ja039772w","article-title":"High-performance semiconducting polythiophenes for organic thin-film transistors","volume":"126","author":"Ong","year":"2004","journal-title":"J. Am. Chem. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1141","DOI":"10.1002\/adma.200401660","article-title":"Structurally ordered polythiophene nanoparticles for high-performance organic thin-film transistors","volume":"17","author":"Ong","year":"2005","journal-title":"Adv. Mater."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/14\/9\/16287\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:15:30Z","timestamp":1760217330000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/14\/9\/16287"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,9,2]]},"references-count":27,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2014,9]]}},"alternative-id":["s140916287"],"URL":"https:\/\/doi.org\/10.3390\/s140916287","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,9,2]]}}}