{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,21]],"date-time":"2026-10-21T08:42:17Z","timestamp":1792572137040,"version":"4.5.0"},"reference-count":51,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2021,12,19]],"date-time":"2021-12-19T00:00:00Z","timestamp":1639872000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2021R1A6A1A03038785"],"award-info":[{"award-number":["2021R1A6A1A03038785"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>This paper compared the effects of A. indica plant proteins over chemical methods in the morphology of zinc oxide nanoparticles (ZnO NPs) prepared by a co-precipitation method, and ethanol sensing performance of prepared thin films deposited over a fluorene-doped tin oxide (FTO) bind glass substrate using spray pyrolysis technique. The average crystallite sizes and diameters of the grain-sized cluster ZnO NPs were 25 and (701.79 \u00b1 176.21) nm for an undoped sample and 20 and (489.99 \u00b1 112.96) nm for A. india dye-doped sample. The fourier transform infrared spectroscopy (FTIR) analysis confirmed the formation of the Zn\u2013O bond at 450 cm\u22121, and also showed the presence of plant proteins due to A. indica dye extracts. ZnO NPs films exhibited good response (up to 51 and 72% for without and with A. indica dye-doped extracts, respectively) toward ethanol vapors with quick response-recovery characteristics at a temperature of 250 \u00b0C for undoped and 225 \u00b0C for A. indica dye-doped ZnO thin films. The interaction of A. indica dye extracts helps to decrease the operating temperature and increased the response and recovery rates of the sensor, which may be due to an increase in the specific surface area, resulting in adsorption of more oxygen and hence high response results.<\/jats:p>","DOI":"10.3390\/molecules26247685","type":"journal-article","created":{"date-parts":[[2021,12,20]],"date-time":"2021-12-20T02:50:18Z","timestamp":1639968618000},"page":"7685","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":48,"title":["Study on the Synthesis of ZnO Nanoparticles Using Azadirachta indica Extracts for the Fabrication of a Gas Sensor"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9528-280X","authenticated-orcid":false,"given":"Tirtha Raj","family":"Acharya","sequence":"first","affiliation":[{"name":"Plasma Bioscience Research Center, Applied Plasma Medicine Center, Department of Electrical and Biological Physics, Kwangwoon University, Seoul 01897, Korea"},{"name":"Department of Physics, Saint Xavier\u2019s College, Tribhuvan University, Maitighar, Kathmandu 44600, Nepal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4467-0490","authenticated-orcid":false,"given":"Pradeep","family":"Lamichhane","sequence":"additional","affiliation":[{"name":"Plasma Bioscience Research Center, Applied Plasma Medicine Center, Department of Electrical and Biological Physics, Kwangwoon University, Seoul 01897, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0340-3844","authenticated-orcid":false,"given":"Rizwan","family":"Wahab","sequence":"additional","affiliation":[{"name":"Chair for DNA Research, Department of Zoology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7174-2912","authenticated-orcid":false,"given":"Dinesh Kumar","family":"Chaudhary","sequence":"additional","affiliation":[{"name":"Department of Physics, Amrit Campus, Tribhuvan University, Kathmandu 44600, Nepal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2557-8699","authenticated-orcid":false,"given":"Bhanu","family":"Shrestha","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, Kwangwoon University, Seoul 01897, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5369-9076","authenticated-orcid":false,"given":"Leela Pradhan","family":"Joshi","sequence":"additional","affiliation":[{"name":"Department of Physics, Amrit Campus, Tribhuvan University, Kathmandu 44600, Nepal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4965-5046","authenticated-orcid":false,"given":"Nagendra Kumar","family":"Kaushik","sequence":"additional","affiliation":[{"name":"Plasma Bioscience Research Center, Applied Plasma Medicine Center, Department of Electrical and Biological Physics, Kwangwoon University, Seoul 01897, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5385-1878","authenticated-orcid":false,"given":"Eun Ha","family":"Choi","sequence":"additional","affiliation":[{"name":"Plasma Bioscience Research Center, Applied Plasma Medicine Center, Department of Electrical and Biological Physics, Kwangwoon University, Seoul 01897, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3654","DOI":"10.1063\/1.1738932","article-title":"Fabrication and Ethanol Sensing Characteristics of ZnO Nanowire Gas Sensors","volume":"84","author":"Wan","year":"2004","journal-title":"Appl. Phys. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1016\/j.snb.2009.04.052","article-title":"Ethanol Gas Sensor Based on Al-Doped ZnO Nanomaterial with Many Gas Diffusing Channels","volume":"140","author":"Yang","year":"2009","journal-title":"Sens. Actuators B Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1016\/j.mseb.2004.12.061","article-title":"Development of a Novel Gas Sensor Based on Oxide Thick Films","volume":"118","author":"Arshak","year":"2005","journal-title":"Mater. Sci. Eng. B"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"75003","DOI":"10.1088\/0022-3727\/47\/7\/075003","article-title":"Enhanced Gas-Sensing Properties of ZnO Nanorods Encapsulated in an Fe-Doped ZnO Shell","volume":"47","author":"Khayatian","year":"2014","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"12036","DOI":"10.1088\/1742-6596\/1706\/1\/012036","article-title":"Study on Influence of Fe Doping into ZnO Film for Ethanol Sensing","volume":"1706","author":"Chaudhary","year":"2020","journal-title":"Proc. J. Phys. Conf. Ser."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Ajmal, H.M.S., Khan, F., Huda, N.U., Lee, S., Nam, K., Kim, H.Y., Eom, T.-H., and Kim, S.D. (2019). High-Performance Flexible Ultraviolet Photodetectors with Ni\/Cu-Codoped ZnO Nanorods Grown on PET Substrates. Nanomaterials, 9.","DOI":"10.3390\/nano9081067"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Ajmal, H.M.S., Khan, F., Nam, K., Kim, H.Y., and Kim, S.D. (2020). Ultraviolet Photodetection Based on High-Performance Co-Plus-Ni Doped ZnO Nanorods Grown by Hydrothermal Method on Transparent Plastic Substrate. Nanomaterials, 10.","DOI":"10.3390\/nano10061225"},{"key":"ref_8","first-page":"1","article-title":"Biosynthesis of Zinc Oxide Nanoparticles Using Ixora coccinea Leaf Extract\u2014A Green Approach","volume":"5","author":"Yedurkar","year":"2016","journal-title":"Open J. Synth. Theory Appl."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"146840","DOI":"10.1016\/j.apsusc.2020.146840","article-title":"Enhanced Hole Selecting Behavior of WO3 Interlayers for Efficient Indoor Organic Photovoltaics with High Fill-Factor","volume":"527","author":"Kim","year":"2020","journal-title":"Appl. Surf. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"45026","DOI":"10.1088\/1361-6595\/ab7f4d","article-title":"Sustainable Nitrogen Fixation from Synergistic Effect of Photo-Electrochemical Water Splitting and Atmospheric Pressure N2 Plasma","volume":"29","author":"Lamichhane","year":"2020","journal-title":"Plasma Sources Sci. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1038\/nmat1284","article-title":"Repeated Temperature Modulation Epitaxy for P-Type Doping and Light-Emitting Diode Based on ZnO","volume":"4","author":"Tsukazaki","year":"2005","journal-title":"Nat. Mater."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/1752-153X-7-136","article-title":"Hydrothermal Synthesis of Zinc Oxide Nanoparticles Using Rice as Soft Biotemplate","volume":"7","author":"Ramimoghadam","year":"2013","journal-title":"Chem. Cent. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"474","DOI":"10.1364\/OL.39.000474","article-title":"Enhanced Optical Limiting in Polystyrene--ZnO Nanotop Composite Films","volume":"39","author":"Haripadmam","year":"2014","journal-title":"Opt. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1774","DOI":"10.3762\/bjnano.5.188","article-title":"The Surface Properties of Nanoparticles Determine the Agglomeration State and the Size of the Particles under Physiological Conditions","volume":"5","author":"Bantz","year":"2014","journal-title":"Beilstein J. Nanotechnol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1016\/S1748-0132(07)70113-5","article-title":"Catalytic Activity of Au Nanoparticles","volume":"2","author":"Janssens","year":"2007","journal-title":"Nano Today"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"933","DOI":"10.1002\/smll.200801206","article-title":"Thermal and Electrical Conductivity of Size-Tuned Bismuth Telluride Nanoparticles","volume":"5","author":"Dirmyer","year":"2009","journal-title":"Small"},{"key":"ref_17","first-page":"638","article-title":"Restriction of Particle Size and Lattice Strain through X-ray Diffraction Peak Broadening Analysis of ZnO Nanoparticles","volume":"49","author":"Ihsan","year":"2015","journal-title":"Adv. Phys. Theor. Appl."},{"key":"ref_18","first-page":"251","article-title":"Thermoluminescence and Optical Absorption Spectra Of Zns: Mn Nanoparticles","volume":"6","author":"Sharma","year":"2009","journal-title":"Chalcogenide Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"15","DOI":"10.21315\/jps2021.32.2.2","article-title":"Green Synthesis of Zinc Oxide Nanoparticles Using Ixora Coccinea Leaf Extract for Ethanol Vapour Sensing","volume":"32","author":"Joshi","year":"2021","journal-title":"J. Phys. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/j.jphotobiol.2018.04.036","article-title":"A Review on Bio-Synthesized Zinc Oxide Nanoparticles Using Plant Extracts as Reductants and Stabilizing Agents","volume":"183","author":"Basnet","year":"2018","journal-title":"J. Photochem. Photobiol. B Biol."},{"key":"ref_21","first-page":"466","article-title":"Chemical investigation of Azadirachta indica leaf (m azadirachta)","volume":"45","author":"Basak","year":"1968","journal-title":"J. Indian Chem. Soc."},{"key":"ref_22","first-page":"1336","article-title":"Biological Activities and Medicinal Properties of Neem (Azadirachta indica)","volume":"82","author":"Biswas","year":"2002","journal-title":"Curr. Sci."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.mssp.2014.12.053","article-title":"Biosynthesis of Zinc Oxide Nanoparticles from Azadirachta indica for Antibacterial and Photocatalytic Applications","volume":"32","author":"Bhuyan","year":"2015","journal-title":"Mater. Sci. Semicond. Process."},{"key":"ref_24","first-page":"75","article-title":"Synthesis of ZnO Nanoparticles and Investigation of the Ionic Template Effect on Their Size and Shape","volume":"1","author":"Nejati","year":"2011","journal-title":"Int. Nano Lett."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1007\/s40145-015-0142-4","article-title":"Annealing Effects on the Structural and Optical Properties of ZnO Nanoparticles with PVA and CA as Chelating Agents","volume":"4","author":"Mallika","year":"2015","journal-title":"J. Adv. Ceram."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1016\/j.apsusc.2015.03.176","article-title":"Green Synthesis, Characterization and Antimicrobial Activities of Zinc Oxide Nanoparticles from the Leaf Extract of Azadirachta indica (L.)","volume":"345","author":"Elumalai","year":"2015","journal-title":"Appl. Surf. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"6588","DOI":"10.1039\/D0GC01348J","article-title":"In Situ Plasma-Assisted Synthesis of Polydopamine-Functionalized Gold Nanoparticles for Biomedical Applications","volume":"22","author":"Nguyen","year":"2020","journal-title":"Green Chem."},{"key":"ref_28","first-page":"470","article-title":"ZnO Films Prepared by Modified Sol-Gel Technique","volume":"49","author":"Gayen","year":"2011","journal-title":"Indian J. Pure Appl. Phys."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3577","DOI":"10.1002\/pssc.200672164","article-title":"Photoluminesence and FTIR Study of ZnO Nanoparticles: The Impurity and Defect Perspective","volume":"3","author":"Xiong","year":"2006","journal-title":"Phys. Status Solidi C"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2065","DOI":"10.1007\/s11164-018-03717-9","article-title":"Synthesis of Zinc Oxide Nanoparticles (ZnO NPs) Using Pure Bioflavonoid Rutin and Their Biomedical Applications: Antibacterial, Antioxidant and Cytotoxic Activities","volume":"45","author":"Bharathi","year":"2019","journal-title":"Res. Chem. Intermed."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3265","DOI":"10.1016\/j.matlet.2006.11.089","article-title":"Preparation and Characterization of ZnO Nanoparticles by a Novel Sol--Gel Route","volume":"61","author":"Vafaee","year":"2007","journal-title":"Mater. Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2811","DOI":"10.1016\/j.ceramint.2012.09.050","article-title":"Optical and Photocatalytic Properties of La-Doped ZnO Nanoparticles Prepared via Precipitation and Mechanical Milling Method","volume":"39","author":"Suwanboon","year":"2013","journal-title":"Ceram. Int."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1016\/j.tibtech.2013.01.003","article-title":"The Greener Synthesis of Nanoparticles","volume":"31","author":"Kharissova","year":"2013","journal-title":"Trends Biotechnol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1938","DOI":"10.1016\/S0021-9258(18)96650-0","article-title":"Constitutive Inorganic Pyrophosphatase of Escherichia coli I. Purification and Catalytic Properties","volume":"241","author":"Josse","year":"1966","journal-title":"J. Biol. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.tsf.2005.04.006","article-title":"Indium Tin Oxide Thin Film Gas Sensors for Detection of Ethanol Vapours","volume":"490","author":"Vaishnav","year":"2005","journal-title":"Thin Solid Film."},{"key":"ref_36","first-page":"1","article-title":"Synthesis and Characterization of Nanocrystalline Zinc Oxide Thin Films for Ethanol Vapor Sensor","volume":"6","author":"Bhasha","year":"2015","journal-title":"J. Nanomed. Nanotechnol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"130671","DOI":"10.1016\/j.matlet.2021.130671","article-title":"Green Synthesis of ZnO and Ag-Doped ZnO Nanoparticles Using Azadirachta indica Leaves: Characterization and Their Potential Antibacterial, Antidiabetic, and Wound-Healing Activities","volume":"305","author":"Iqbal","year":"2021","journal-title":"Mater. Lett."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"440","DOI":"10.1023\/A:1012741510960","article-title":"Nature of Gas Sensitivity in Nanocrystalline Metal Oxides","volume":"74","author":"Rumyantseva","year":"2001","journal-title":"Russ. J. Appl. Chem."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/0169-4332(93)90363-G","article-title":"Fundamentals of Gas-Surface Interactions on Metal Oxides","volume":"72","author":"Henrich","year":"1993","journal-title":"Appl. Surf. Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"289","DOI":"10.4028\/www.scientific.net\/AMR.55-57.289","article-title":"Effect of Platinum Impregnation on ZnO Tetrapods for Ethanol Sensor","volume":"55","author":"Hongsith","year":"2008","journal-title":"Adv. Mater. Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"32101","DOI":"10.1063\/1.2752541","article-title":"Surface-Depletion Controlled Gas Sensing of ZnO Nanorods Grown at Room Temperature","volume":"91","author":"Li","year":"2007","journal-title":"Appl. Phys. Lett."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/j.snb.2007.05.028","article-title":"The Nature of Processes Controlling the Kinetics of Indium Oxide-Based Thin Film Gas Sensor Response","volume":"128","author":"Korotcenkov","year":"2007","journal-title":"Sens. Actuators B Chem."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"845","DOI":"10.1246\/cl.1989.845","article-title":"Role of Additives on Alcohol Sensing by Semiconductor Gas Sensor","volume":"18","author":"Matsushima","year":"1989","journal-title":"Chem. Lett."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"104","DOI":"10.1016\/S0254-0584(99)00193-5","article-title":"Lanthanum Doped SnO2 and ZnO Thin Films Sensitive to Ethanol and Humidity","volume":"63","author":"Stambolova","year":"2000","journal-title":"Mater. Chem. Phys."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1420","DOI":"10.3390\/s6101420","article-title":"ZnO: Al Thin Film Gas Sensor for Detection of Ethanol Vapor","volume":"6","author":"Chou","year":"2006","journal-title":"Sensors"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1016\/0250-6874(89)87026-X","article-title":"Surface Processes in the Detection of Reducing Gases with SnO2-Based Devices","volume":"18","author":"Kohl","year":"1989","journal-title":"Sens. Actuators"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s42452-020-2813-1","article-title":"Green Synthesis and Characterization of Zinc Oxide Nanoparticles Using Eucalyptus globulus Labill. Leaf Extract and Zinc Nitrate Hexahydrate Salt","volume":"2","author":"Barzinjy","year":"2020","journal-title":"SN Appl. Sci."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"2226","DOI":"10.1016\/j.physb.2010.02.016","article-title":"Physical Properties of ZnO Thin Films Deposited at Various Substrate Temperatures Using Spray Pyrolysis","volume":"405","author":"Rao","year":"2010","journal-title":"Phys. B Condens. Matter"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1007\/s10971-009-1959-5","article-title":"Preparation of ZnO Nanoparticles by a Surfactant-Assisted Complex Sol--Gel Method Using Zinc Nitrate","volume":"51","author":"Zhang","year":"2009","journal-title":"J. Sol-Gel Sci. Technol."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"354","DOI":"10.1016\/j.matlet.2011.11.004","article-title":"ZnO Thin Films Preparation by Spray Pyrolysis and Electrical Characterization","volume":"68","author":"Goyal","year":"2012","journal-title":"Mater. Lett."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1016\/j.msec.2012.01.032","article-title":"Influence of Sn Doping on ZnO Sensing Properties for Ethanol and Acetone","volume":"32","author":"Li","year":"2012","journal-title":"Mater. Sci. Eng. C"}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/26\/24\/7685\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:52:07Z","timestamp":1760169127000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/26\/24\/7685"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,12,19]]},"references-count":51,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2021,12]]}},"alternative-id":["molecules26247685"],"URL":"https:\/\/doi.org\/10.3390\/molecules26247685","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,12,19]]}}}