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Identifier 000452057
Title Printable gas sensors based on transition metal vanadate nanostructures
Alternative Title Εκτυπώσιμοι αισθητήρες αερίων βασισμένοι σε νανοδομές βαναδίων μετάλλων μετάπτωσης
Author Μοσχογιαννάκη, Μαριλένα
Thesis advisor Ρεμεδιάκης, Ιωάννης
Reviewer Κιοσέογλου, Γεώργιος
Παπάζογλου, Δημήτριος
Κανδήλα, Μαρία
Μαρνέλλος, Γεώργιος
Στούμπος, Κωνσταντίνος
Σωτηρόπουλος, Σωτήριος
Abstract Although the first metal oxide gas sensor was developed 60 years ago, the need for air quality monitoring has become more and more important due to the current high levels of air pollution caused by human activities. Low air quality causes more deaths annually than HIV/AIDS and malaria combined, while simultaneously the World Health Organization (WHO) declares that 9 out of 10 people world-wide live in places where air quality exceeds WHO guideline limits. At the same time, gas sensors should meet some criteria such as cost efficiency, low energy consumption, low dimensions (miniaturization), stretchability and flexibility combined with good performance in order to be applied in a variety of daily life applications. Furthermore, the development of advanced ternary and quaternary metal oxides paves the way to finding potential candidates for novel real-life air monitoring applications due to the fact that their properties may exceed those of the well-established materials. Although these materials have already been studied in a variety of electrochemical applications, they are not known as gas sensors and their exact sensing mechanism and interactions between the gas molecules and materials’ surface are not yet discovered. Therefore, finding an effective way for gas monitoring is undoubtedly of high priority in the field of environmental and health protection. In this dissertation, focus was given on the low-cost synthesis, deeply structural- morphological - optical characterization and environmental applications of advanced ternary and quaternary metal oxides, belonging to the category of Transition Metal Vanadates (TMVs). To be more specific, polymorphs of Transition Metal Vanadium Oxides were synthesized by two synthetic procedures, a polyol process at room-temperature and a solvothermal process at 150oC. The transition metal vanadates synthesized had the formula of MxV2O5+x, M= Co (cobalt), Ni (nickel), Co-Ni (cobalt-nickel) and Zn (zinc) and x=1-3. The synthetic parameters changed were molar ratio, additive reducing agent while reaction and optimized configurations were found. Pure materials, highly crystallized and with porous nanostructures were obtained, while it was observed that the triclinic for x=1, monoclinic for x=2 and orthorhombic for x=3 structures were the most favorable. A plethora of characterization techniques were used such as X-Ray Diffractometry, Scanning and Transition Electron Microscopy, Electron Dispersive and UV-Vis Spectroscopy, Raman and (operando) FT-IR Spectroscopy and Kelvin Probe. A variety of deposition techniques (spin coating, direct ink writing, screen printing and drop casting) were used in order to transform the above-mentioned materials (powders) into sensing layers. The final devices (including glass and flexible PET substrates or Pt, Pd and Au electrodes) were studied towards a variety of environmental gases such as hydrogen, ozone, carbon monoxide, nitrogen dioxide and VOCs, at room, low and higher operating temperatures, and under different humidity environments. The most promising materials (Cobalt Vanadate polymorphs) were characterized explicitly and plausible gas sensing mechanisms are proposed based on operando Diffused Reflectance Infrared Fourier Transformed technique (DRIFTS) and operando Kelvin Probe, finding the exact gas reactions taken place on sensors’ surface and their band structure model.
Language English
Subject Cobalt vanadates
Environmental sensors
Low cost printable techniques
Έυκαμπτοι αισθητήρες
Οξείδια κοβαλτίου-βαναδίου
Περιβαλλοντικοί αισθητήρες
Issue date 2022-11-23
Collection   School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/0/2/a/metadata-dlib-1669277042-217374-1223.tkl Bookmark and Share
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