Networks of nanomembranes and tubular structures of GaN and TiO2 for memristive systems and biomedical applications
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StatusThe thesis was presented on the 18 January, 2023Approved by NCAA on the 24 February, 2023 Abstract – 1.52 Mb / in romanian – 1.51 Mb / in englishThesisCZU 621.315.592
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Keywords
Nanotechnology, GaN, TiO2, nanotubes, nanomembranes, nanoengines, aeromaterials, memristors, sensors, interaction with proteins.Summary
Dissertation structure: The dissertation was realized at Technical University of Moldova, Chisinau, 2022. It is written in Romanian language and consists of introduction, 4 chapters, general conclusions and recommendations, and bibliography (278 references). The content of the dissertation is exposed on 146 pages of basic text, contains 110 figures and 8 tables. The obtained results were published in 23 scientific papers, including 9 articles in international journals, 2 articles in national journals and 12 publications at national and international conferences.
Field of study: Nanotechnologies and new multifunctional materials.
Aim of the work: Elaboration of technological conditions for fabrication of low dimensional structures based on GaN, TiO2 and Ga2O3 with unique properties and demonstration of their applications in electronics, biomedicine and environment fields.
Objectives: Elaboration of nanotube structures based on titanium dioxide and gallium nitride and their investigation as micro- and nanoengines in aqueous medium controlled by external light sources. Photocatalytic study of the TiO2 nanotubes for degradation of organic compounds. Elaboration and investigation of memristive circuits based on GaN ultrathin membranes fabricated by Surface Charge Lithography approach. Determination of technological conditions for fabrication of aeromaterials like aero-GaN and aero-Ga2O3 and their physico-chemical characterization using different techniques. Investigation of the interaction between ZnO and GaN nanoparticles with proteins and their cytotoxicity on the cells.
Novelty and scientific originality: TiO2 nanotubes with gradual decrease of their internal diameter, an important parameter for their use as micro- or nanoengines, including the Cargo effect in the case of networks of nanotubes, or for improving the efficiency of organic compound degradation, were fabricated. GaN tubular structures with the thickness of the tube walls of a few nanometers with complex internal architecture were fabricated, and their use as microengines was demonstrated. The memristive effect on GaN ultrathin membranes in different configurations was studied, and the habituation or dishabituation mechanisms of electrical stimuli was investigated, an identical process being observed in biological synapses. Aeromaterials based on GaN and Ga2O3 were fabricated, and their physico-chemical investigation was performed. The possibilities to use them as pressure sensors or shielding materials for high frequency radiation (GHz and THz) were identified. The interaction of GaN or ZnO nanoparticles with proteins was investigated using different techniques, as well as the cytotoxicity of the formed complexes upon living cells was explored.
The solved scientific problem: Manufacturing technology development of GaN and TiO2 tubular structures by a cost-effective technique, GaN and Ga2O3 aeromaterials fabrication and their use in applications like biomedicine, environment or electronics.
Theoretical significance and practical value of the work: This work presents practical applications of GaN ultrathin membranes, GaN and TiO2 micro and nanotubes, and new aeromaterials based on GaN and Ga2O3 materials, like memristors, microengines or shielding materials in a broad frequency range. The physical model based on trap induced space charge limited current was elaborated for describing the memristive behaviour in GaN membranes. A physical model was elaborated for pressure sensors based on aero-GaN, which takes into consideration both the piezoresistive property of the material and the dynamics of the microtetrapods during the pressure change.
Oficial Reviewers
- Mihail Caraman
doctor habilitat, professor, Moldova State University - Leonid Culiuc
doctor habilitat, professor, Institute of Applied Physics of the - Eduard Monaico
doctor, associate professor (docent)
Council's Members
- Dumitru Ţiuleanu, president
doctor habilitat, professor, Technical University of Moldova - Sergiu Railean , secretary
doctor, associate professor (docent) - Emil Rusu,
doctor habilitat, associate professor (docent), Institute of the Electronic Engineering and Nanotechnologies
Theses
