{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T15:25:14Z","timestamp":1775834714938,"version":"3.50.1"},"reference-count":27,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2023,6,16]],"date-time":"2023-06-16T00:00:00Z","timestamp":1686873600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this study, we utilized a sapphire substrate with a matrix protrusion structure as a template. We employed a ZnO gel as a precursor and deposited it onto the substrate using the spin coating method. After undergoing six cycles of deposition and baking, a ZnO seed layer with a thickness of 170 nm was formed. Subsequently, we used a hydrothermal method to grow ZnO nanorods (NRs) on the aforementioned ZnO seed layer for different durations. ZnO NRs exhibited a uniform outward growth rate in various directions, resulting in a hexagonal and floral morphology when observed from above. This morphology was particularly evident in ZnO NRs synthesized for 30 and 45 min. Due to the protrusion structure of ZnO seed layer, the resulting ZnO nanorods (NRs) displayed a floral and matrix morphology on the protrusion ZnO seed layer. To further enhance their properties, we utilized Al nanomaterial to decorate the ZnO nanoflower matrix (NFM) using a deposition method. Subsequently, we fabricated devices using both undecorated and Al-decorated ZnO NFMs and deposited an upper electrode using an interdigital mask. We then compared the gas-sensing performance of these two types of sensors towards CO and H2 gases. The research findings indicate that sensors based on Al-decorated ZnO NFM exhibit superior gas-sensing properties compared to undecorated ZnO NFM for both CO and H2 gases. These Al-decorated sensors demonstrate faster response times and higher response rates during the sensing processes.<\/jats:p>","DOI":"10.3390\/s23125629","type":"journal-article","created":{"date-parts":[[2023,6,16]],"date-time":"2023-06-16T02:54:33Z","timestamp":1686884073000},"page":"5629","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Synthesis of ZnO Nanoflower Arrays on a Protrusion Sapphire Substrate and Application of Al-Decorated ZnO Nanoflower Matrix in Gas Sensors"],"prefix":"10.3390","volume":"23","author":[{"given":"Xin","family":"Zhao","sequence":"first","affiliation":[{"name":"School of Information Engineering, Shanghai Zhongqiao Vocational and Technical University, Shanghai 201514, China"}]},{"given":"Jang-Cheng","family":"Jheng","sequence":"additional","affiliation":[{"name":"Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung 402, Taiwan"}]},{"given":"Ni-Ni","family":"Chou","sequence":"additional","affiliation":[{"name":"Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 811, Taiwan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6278-2077","authenticated-orcid":false,"given":"Fang-Hsing","family":"Wang","sequence":"additional","affiliation":[{"name":"Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung 402, Taiwan"}]},{"given":"Cheng-Fu","family":"Yang","sequence":"additional","affiliation":[{"name":"Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 811, Taiwan"},{"name":"Department of Aeronautical Engineering, Chaoyang University of Technology, Taichung 413, Taiwan"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"213105","DOI":"10.1063\/1.1929872","article-title":"Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorod film","volume":"86","author":"Kim","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"102904","DOI":"10.1063\/1.2185247","article-title":"Highly sensitive gas sensor based on integrated titania nanosponge arrays","volume":"88","author":"Zuruzi","year":"2006","journal-title":"Appl. Phys. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"163123","DOI":"10.1063\/1.2106006","article-title":"Semiconductor gas sensor based on tin oxide nanorods prepared by plasma-enhanced chemical vapor deposition with postplasma treatment","volume":"87","author":"Huang","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"10881","DOI":"10.1021\/jp1016938","article-title":"ZnO Nanostructures for Gas Sensing: Interaction of NO2, NO, O, and N with the ZnO(1010) Surface","volume":"114","author":"Spencer","year":"2010","journal-title":"J. Phys. Chem. C"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"5629","DOI":"10.1039\/C7RA13702H","article-title":"C2H5OH and NO2 sensing properties of ZnO nanostructures: Correlation between crystal size, defect level and sensing performance","volume":"8","author":"Quy","year":"2018","journal-title":"RSC Adv."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"4063","DOI":"10.1007\/s10904-020-01553-2","article-title":"High Performance CO Gas Sensor Based on ZnO Nanoparticles","volume":"30","author":"Hjiri","year":"2020","journal-title":"J. Inorg. Organomet. Polym. Mater."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"7794","DOI":"10.1016\/j.apsusc.2009.04.180","article-title":"The gas response enhancement from ZnO film for H2 gas detection","volume":"255","author":"Abdullah","year":"2009","journal-title":"Appl. Surf. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1098","DOI":"10.1016\/j.physe.2010.11.029","article-title":"Zinc oxide nanowires on carbon microfiber as flexible gas sensor, Low-dimensional Systems and Nanostructures","volume":"44","author":"Tonezzer","year":"2012","journal-title":"Phys. E"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3841","DOI":"10.1039\/b504094a","article-title":"Single-crystalline Sb-doped SnO2 nanowires: Synthesis and gas sensor application","volume":"30","author":"Wan","year":"2005","journal-title":"Chem. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"611","DOI":"10.1007\/s00339-007-4076-8","article-title":"A two-step hydrothermally grown ZnO microtube array for CO gas sensing","volume":"88","author":"Wang","year":"2007","journal-title":"Appl. Phys. A"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"4995","DOI":"10.1088\/0957-4484\/17\/19\/037","article-title":"Hydrothermally grown oriented ZnO nanorod arrays for gas sensing applications","volume":"17","author":"Wang","year":"2006","journal-title":"Nanotechnology"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1900","DOI":"10.1021\/jp065963k","article-title":"Size Dependence of Gas Sensitivity of ZnO Nanorods","volume":"111","author":"Liao","year":"2006","journal-title":"J. Phys. Chem. C"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Zhao, X., Wang, C.S., Chou, N.N., Wang, F.H., and Yang, C.F. (2023). Synthesis of ZnO Nanoflower Arrays on Patterned Cavity Substrate and Their Application in Methylene Blue Degradation. Materials, 16.","DOI":"10.3390\/ma16072647"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"154177","DOI":"10.1016\/j.jallcom.2020.154177","article-title":"Cu-doped ZnO nanorods based QCM sensor for hazardous gases","volume":"826","author":"Alev","year":"2020","journal-title":"J. Alloy. Compd."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"e202200090","DOI":"10.1002\/tcr.202200090","article-title":"Noble Metal-Decorated Nanostructured Zinc Oxide: Strategies to Advance Chemiresistive Hydrogen Gas Sensing","volume":"22","author":"Mohammad","year":"2022","journal-title":"Chem. Record"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"154570","DOI":"10.1016\/j.apsusc.2022.154570","article-title":"Transition metal decorated ZnO monolayer for CO and NO sensing: A DFT + U study with vdW correction","volume":"604","author":"Lalmuanchhana","year":"2022","journal-title":"Appl. Surf. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"137693","DOI":"10.1016\/j.tsf.2019.137693","article-title":"Effect of Pd-decoration on the sensing properties of ZnO nanostructures","volume":"693","author":"Dilova","year":"2020","journal-title":"Thin Solid Film."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"115603","DOI":"10.1088\/0957-4484\/18\/11\/115603","article-title":"Growth of aligned ZnO nanorods and nanopencils on ZnO\/Si in aqueous solution: Growth mechanism and structural and optical properties","volume":"18","author":"Ahsanulhaq","year":"2007","journal-title":"Nanotechnology"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/j.matlet.2018.01.137","article-title":"Photoluminescence study of interstitial oxygen defects in ZnO nanostructures","volume":"218","author":"Lv","year":"2018","journal-title":"Mater. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Tseng, H.W., Wang, C.S., Wang, F.H., Liu, H.W., and Yang, C.F. (2022). A novel synthesis of ZnO nanoflower arrays using lift-off technique with different thicknesses of Al sacrificial layers on a patterned sapphire substrate. Nanomaterials, 12.","DOI":"10.3390\/nano12040612"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"G110","DOI":"10.1149\/1.1346616","article-title":"Defect Photoluminescence of Undoping ZnO Films and Its Dependence on Annealing Conditions","volume":"148","author":"Lin","year":"2001","journal-title":"J. Electrochem. Soc."},{"key":"ref_22","first-page":"44","article-title":"Effect of Synthesis Time on Synthesis and Photoluminescence Properties of ZnO Nanorods","volume":"2","author":"Yang","year":"2022","journal-title":"Appl. Funct. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"4977","DOI":"10.1016\/j.jeurceramsoc.2021.03.031","article-title":"Defect engineering of ZnO: Review on oxygen and zinc vacancies","volume":"41","author":"Gurylev","year":"2021","journal-title":"J. Eur. Ceram. Soc."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1016\/j.apsusc.2018.08.170","article-title":"Oxygen vacancy enhancement promoting strong green emission through surface modification in ZnO thin film","volume":"462","author":"Purbayanto","year":"2018","journal-title":"Appl. Surf. Sci."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"203101","DOI":"10.1063\/1.2203932","article-title":"Ultrasensitive and highly selective gas sensors using three-dimensional tungsten oxide nanowire networks","volume":"88","author":"Ponzoni","year":"2006","journal-title":"Appl. Phys. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1111\/j.1151-2916.1976.tb09374.x","article-title":"Dependence of electricalconductivity of ZnO, degree of sensing","volume":"59","author":"Takata","year":"1976","journal-title":"J. Am. Ceram. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/j.snb.2005.09.008","article-title":"Nano-crystalline Cu-doped ZnO thin film gas sensor for CO","volume":"115","author":"Gong","year":"2006","journal-title":"Sens. Actuators B Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/12\/5629\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:56:08Z","timestamp":1760126168000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/12\/5629"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,16]]},"references-count":27,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2023,6]]}},"alternative-id":["s23125629"],"URL":"https:\/\/doi.org\/10.3390\/s23125629","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,6,16]]}}}