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Such devices can be useful in designing non\u2010invasive ultrasensitive hand\u2010held sensors for diagnostic identification of volatile organic compounds (VOCs) in exhaled air, offering pain\u2010free and easier detection of long\u2010term diseases such as asthma. In the present work, WO<jats:sub>3<\/jats:sub> nanoblocks, with a high surface area and porosity, have been grown directly over transparent conducting oxide to minimize Ohmic resistance, facilitating smoother electron transfer and enhanced current response. Further modification with porous alumina (\u03b3\u2010Al<jats:sub>2<\/jats:sub>O<jats:sub>3<\/jats:sub>), by electrodeposition, resulted in the selective and ultrasensitive detection of NO<jats:sub>X<\/jats:sub> in simulated exhaled air. Crystal phase purity of as\u2010fabricated pristine as well modified samples is validated with X\u2010ray diffraction analysis. Morphological and microstructural analyses reveal the successful deposition of porous alumina over the surface of WO<jats:sub>3<\/jats:sub>. Improved surface area and porosity is presented by porous alumina in the modified WO<jats:sub>3<\/jats:sub> device, suggesting more active sites for the gas molecules to get adsorbed and diffuse through the pores. Oxygen vacancies, which are detrimental in the transport phenomenon in the presented sensors, have been studied using X\u2010ray photoelectron spectroscopic (XPS) analysis. Gas sensing studies have been performed by fabricating chemiresistor devices based on bare WO<jats:sub>3<\/jats:sub> and Al<jats:sub>2<\/jats:sub>O<jats:sub>3<\/jats:sub>\u2010modified WO<jats:sub>3<\/jats:sub>. The higher sensitivity for NO<jats:sub>X<\/jats:sub> gas in case of \u03b3\u2010Al<jats:sub>2<\/jats:sub>O<jats:sub>3<\/jats:sub>\u2010modified WO<jats:sub>3<\/jats:sub> based devices, as compared to bare WO<jats:sub>3<\/jats:sub>\u2010based devices, is attributed to the better surface area and charge transport kinetics. The presented device strategy offers crucial understanding in the design and development of non\u2010invasive, hand\u2010held devices for NO gas present in the human breath, with potential application in medical diagnostics.<\/jats:p>","DOI":"10.1002\/asia.201900699","type":"journal-article","created":{"date-parts":[[2019,8,17]],"date-time":"2019-08-17T00:39:23Z","timestamp":1566002363000},"page":"4673-4680","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Ultrasensitive NO<sub>X<\/sub> Detection in Simulated Exhaled Air: Enhanced Sensing via Alumina Modification of In\u2010Situ Grown WO<sub>3<\/sub> Nanoblocks"],"prefix":"10.1002","volume":"14","author":[{"given":"Suhaib","family":"Alam","sequence":"first","affiliation":[{"name":"Department of Chemistry Indian Institute of Technology  Guwahati Assam 781039 India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mohammad Shaad","family":"Ansari","sequence":"additional","affiliation":[{"name":"Department of Chemistry Indian Institute of Technology  Guwahati Assam 781039 India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Avishek","family":"Banik","sequence":"additional","affiliation":[{"name":"Department of Chemistry Indian Institute of Technology  Guwahati Assam 781039 India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rafat","family":"Ali","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Centre for Nanoscience Indian Institute of Technology  Kanpur U.P 208016 India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2478-8109","authenticated-orcid":false,"given":"Sandeep","family":"Verma","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Centre for Nanoscience Indian Institute of Technology  Kanpur U.P 208016 India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0970-6870","authenticated-orcid":false,"given":"Mohammad","family":"Qureshi","sequence":"additional","affiliation":[{"name":"Department of Chemistry Indian Institute of Technology  Guwahati Assam 781039 India"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2019,8,27]]},"reference":[{"key":"e_1_2_7_1_1","doi-asserted-by":"publisher","DOI":"10.1002\/adfm.201202729"},{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.1039\/C8TA08670B"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1021\/ac902695n"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2018.07.098"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2017.10.153"},{"key":"e_1_2_7_6_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.mattod.2014.08.017"},{"key":"e_1_2_7_7_1","doi-asserted-by":"publisher","DOI":"10.1021\/am402456s"},{"key":"e_1_2_7_8_1","doi-asserted-by":"publisher","DOI":"10.1088\/1752-7155\/2\/1\/017012"},{"key":"e_1_2_7_9_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.071057598"},{"key":"e_1_2_7_10_1","doi-asserted-by":"publisher","DOI":"10.1007\/s10832-012-9755-y"},{"key":"e_1_2_7_11_1","doi-asserted-by":"publisher","DOI":"10.1063\/1.3050524"},{"key":"e_1_2_7_12_1","doi-asserted-by":"publisher","DOI":"10.1038\/nnano.2009.235"},{"key":"e_1_2_7_13_1","doi-asserted-by":"publisher","DOI":"10.1084\/jem.189.10.1621"},{"key":"e_1_2_7_14_1","doi-asserted-by":"publisher","DOI":"10.2147\/MDER.S91201"},{"key":"e_1_2_7_15_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2014.11.147"},{"key":"e_1_2_7_16_1","doi-asserted-by":"publisher","DOI":"10.1164\/rccm.9120-11ST"},{"key":"e_1_2_7_17_1","doi-asserted-by":"publisher","DOI":"10.1080\/10408340600976499"},{"key":"e_1_2_7_18_1","doi-asserted-by":"publisher","DOI":"10.3390\/s16111815"},{"key":"e_1_2_7_19_1","doi-asserted-by":"publisher","DOI":"10.3390\/diagnostics8010012"},{"key":"e_1_2_7_20_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2013.05.090"},{"key":"e_1_2_7_21_1","doi-asserted-by":"publisher","DOI":"10.1021\/acssensors.8b00461"},{"key":"e_1_2_7_22_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.mseb.2017.12.036"},{"key":"e_1_2_7_23_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2018.07.002"},{"key":"e_1_2_7_24_1","doi-asserted-by":"publisher","DOI":"10.1021\/acsnano.6b01196"},{"key":"e_1_2_7_25_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.snb.2013.05.006"},{"key":"e_1_2_7_26_1","doi-asserted-by":"publisher","DOI":"10.1021\/acsami.5b12062"},{"key":"e_1_2_7_27_1","doi-asserted-by":"publisher","DOI":"10.1039\/c3ay40373d"},{"key":"e_1_2_7_28_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.materresbull.2018.02.006"},{"key":"e_1_2_7_29_1","doi-asserted-by":"publisher","DOI":"10.1109\/JSEN.2009.2036050"},{"key":"e_1_2_7_30_1","first-page":"237","volume":"94","author":"Chakraborty S.","year":"2008","journal-title":"Curr. 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