Studies of the anisotropic growth of ZnO synthesized by an organometallic method and kinetic study of the concomitant gelation / Yinping Wang  

Public ISBD Titre : Studies of the anisotropic growth of ZnO synthesized by an organometallic method and kinetic study of the concomitant gelation Titre original : Etudes de la croissance anisotrope de ZnO synthétisés par une méthode organométallique et étude cinétique de la gélification concomitante Type de document : texte imprimé Auteurs : Yinping Wang, Auteur ; Kahn, Myrtil, Directeur de thèse ; Christophe Mingotaud, Directeur de thèse Langues : Anglais (eng) Tags : ZNO, ORGANOMETALLIC METHOD  ANISOTROPIC GROWTH  MECHANISM  GELIFICATION  KINETIC  DRIVING FORCES Résumé : "Nowadays, nanoscience is defined as the studies of structures (molecules) and devices, in which at least one characteristic size is between 1 nm and 100 nm. These nanomaterials act as a bridge between bulk materials and atomic structures, and show many changes in the properties of physical, chemical or biological properties due to the reduction of the size of these structures. Nano materials composed of metal oxides are such kind of interesting materials. Their characteristics are very interesting for the development of electronic, optical, sensor and other applications. For some metal oxides, oxygen deficit will produce vacancies, act as electron donors, and naturally induce the performance of n-type semiconductors. ZnO is a typical example. It has characters of wide band gap of about 3.4 ev, high electron hole interaction energy (60 meV), high electron mobility, visible and near ultraviolet luminescence. These electronic characteristics make it a good candidate for the development of light source and detector. Recent studies have shown ZnO can emit in ultraviolet, violet, green, yellow and even red according to the preparation conditions. These optical properties of ZnO are closely related to the morphology of the material. In the previous work, we first developed a mature synthesis method of ZnO nano materials with organometallic method. By changing different parameters (reaction medium, type of ligand or surfactant, temperature, incubation time, etc.), clear ZnO nano objects with different sizes, shapes and morphologies (isotropic and anisotropic) can be obtained. However, when primary amine is used as ligand, which is the factor controlling this anisotropic growth, the mechanism of anisotropic growth is not clear. The effects of secondary and tertiary amines on nano ZnO are not clear either. Therefore, this paper first studies the above two points. First, we use 2D-plot analysis and statistical analysis to extract particle size information from TEM images. The processed data showed the anisotropic growth mechanism is realized firstly through the orientated attachment process, then finally hindered by the gelation process induced by the interaction between Zn precursor and amino ligand. Second, ZnO NCs was synthesized by using amines with the same aliphatic chain length but different structures as surfactants (primary, secondary and tertiary amines). The interaction between these surfactants and ZnO NCs metal precursors in the whole synthesis process was revealed by the complementary analysis of NMR and DFT. The results show the morphology of ZnO NCs varies with the amine structure, which is due to the great difference of their kinetics on the surface of growing NCs. The interaction of multiple H bonds of primary amines on the surface of ZnO leads to the decrease of the mobility of these amines relative to secondary amines, and the secondary amines remain on the surface of NCs in all spatial dimensions. This thesis work also contains topic of gelation which is discovered during the synthesis of ZnO. It was found the gel formation was related to the formation of oligomers.[...]" Document : Thèse de Doctorat Etablissement_delivrance : Université Toulouse 3 Date_soutenance : 27/06/2022 Ecole_doctorale : Sciences de la matière (SdM) ( Toulouse) Domaine : Sciences et Génie des Matériaux En ligne : https://theses.hal.science/tel-03813573v1 Studies of the anisotropic growth of ZnO synthesized by an organometallic method and kinetic study of the concomitant gelation = Etudes de la croissance anisotrope de ZnO synthétisés par une méthode organométallique et étude cinétique de la gélification concomitante [texte imprimé] / Yinping Wang, Auteur ; Kahn, Myrtil, Directeur de thèse ; Christophe Mingotaud, Directeur de thèse . - [s.d.]. Langues : Anglais (eng) Tags : ZNO, ORGANOMETALLIC METHOD  ANISOTROPIC GROWTH  MECHANISM  GELIFICATION  KINETIC  DRIVING FORCES Résumé : "Nowadays, nanoscience is defined as the studies of structures (molecules) and devices, in which at least one characteristic size is between 1 nm and 100 nm. These nanomaterials act as a bridge between bulk materials and atomic structures, and show many changes in the properties of physical, chemical or biological properties due to the reduction of the size of these structures. Nano materials composed of metal oxides are such kind of interesting materials. Their characteristics are very interesting for the development of electronic, optical, sensor and other applications. For some metal oxides, oxygen deficit will produce vacancies, act as electron donors, and naturally induce the performance of n-type semiconductors. ZnO is a typical example. It has characters of wide band gap of about 3.4 ev, high electron hole interaction energy (60 meV), high electron mobility, visible and near ultraviolet luminescence. These electronic characteristics make it a good candidate for the development of light source and detector. Recent studies have shown ZnO can emit in ultraviolet, violet, green, yellow and even red according to the preparation conditions. These optical properties of ZnO are closely related to the morphology of the material. In the previous work, we first developed a mature synthesis method of ZnO nano materials with organometallic method. By changing different parameters (reaction medium, type of ligand or surfactant, temperature, incubation time, etc.), clear ZnO nano objects with different sizes, shapes and morphologies (isotropic and anisotropic) can be obtained. However, when primary amine is used as ligand, which is the factor controlling this anisotropic growth, the mechanism of anisotropic growth is not clear. The effects of secondary and tertiary amines on nano ZnO are not clear either. Therefore, this paper first studies the above two points. First, we use 2D-plot analysis and statistical analysis to extract particle size information from TEM images. The processed data showed the anisotropic growth mechanism is realized firstly through the orientated attachment process, then finally hindered by the gelation process induced by the interaction between Zn precursor and amino ligand. Second, ZnO NCs was synthesized by using amines with the same aliphatic chain length but different structures as surfactants (primary, secondary and tertiary amines). The interaction between these surfactants and ZnO NCs metal precursors in the whole synthesis process was revealed by the complementary analysis of NMR and DFT. The results show the morphology of ZnO NCs varies with the amine structure, which is due to the great difference of their kinetics on the surface of growing NCs. The interaction of multiple H bonds of primary amines on the surface of ZnO leads to the decrease of the mobility of these amines relative to secondary amines, and the secondary amines remain on the surface of NCs in all spatial dimensions. This thesis work also contains topic of gelation which is discovered during the synthesis of ZnO. It was found the gel formation was related to the formation of oligomers.[...]" Document : Thèse de Doctorat Etablissement_delivrance : Université Toulouse 3 Date_soutenance : 27/06/2022 Ecole_doctorale : Sciences de la matière (SdM) ( Toulouse) Domaine : Sciences et Génie des Matériaux En ligne : https://theses.hal.science/tel-03813573v1

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