Sıvı kristal mezofazları kullanarak mezogözenekli metal sülfür ve metal selenür ince film sentezi ve karakterizasyonu

In this thesis, synthesis of the mesoporous CdS and CdSe by using of liquidcrystalline templating (LCT) approach has been investigated. In the first part ofthe thesis, the thermal and structural behavior of the [Cd(H2O)4](NO3)2/surfactant(P85 = ((PEO)26(PPO)40(PEO)26)) binary lyotropic liquid crystalline (LLC)systems have been investigated towards synthesis of the mesoporous cadmiumsulfide, CdS, or cadmium selenide (CdSe) directly from the mesostructured CdS(or CdSe) thin films. However, the mesostructured CdS/P85 films (at low saltconcentrations), which were obtained by reacting [Cd(H2O)4](NO3)2/P85 LLCthin films under H2S atmosphere, are not stable to calcination process and alwaysproduced bulk CdO and CdS domains over the thin films. More metal ioncontaining [Cd(H2O)4](NO3)2-C12EO10-CTAB mesostructured films produced vastamount of HNO3 under the H2S atmosphere and caused decomposition of CdSback to their nitrates.To overcome above problems, a polymerizing agent, such as titania or silicaprecursors have been added to salt/surfactant LLC mesophase. Both titania andsilica overcame the collapse of the mesophase by rigidifying the structure intomesostructured solid and also by providing stability for a thermal removal ofnitrates from the medium. For this investigation, both [Cd(H2O)4](NO3)2 and[Zn(H2O)6](NO3)2 salts and P123 ((PEO)20(PPO)70(PEO)20) and C12EO10-CTABcouple have been used.Well-ordered mesostructured Cd(II) titania films have been obtained up to15.0 Cd(II)/P123 mole ratio for a 60 mole ratio of Ti(IV)/P123 by spin or dipcoating of a mixture of 1-butanol-[Cd(H2O)4](NO3)2-P123-HNO3-Ti(OC4H9)4.Exposing the mesostructured Cd(II)-TiO2 films to H2Se under a N2 atmospheregave stable CdSe nanoparticles in the channels of the mesostructured rigid titaniawalls up to 25 mole % Cd(II)/Ti(IV). To further increase the metal ion (Cd(II) andZn(II)) content in the structure, the C12EO10-CTAB-salt mesophase has beenemployed. The two surfactant-salt systems, in the presence of a titania precursor,produced sponge like mesoporous CdTiO3 and Zn2TiO4 films up to a mole percentof 57 and 86, respectively, upon calcination. Exposing the mesoporous CdTiO3 toH2S or H2Se atmosphere at RT produced homogeneously distributed CdS or CdSenanocrystallites on the nanocrystalline TiO2 pore walls, respectively. The reactionof mesoporous Zn2TiO4 with H2Se produced stable ZnSe nanocrystallites on thenanocrystalline TiO2 pore walls. The conversion of titania from CdTiO3 to ananatase and brookite phase under H2S and H2Se atmosphere, respectively, andfrom Zn2TiO4 to a rutile phase under H2Se were observed for the first time.Adding a silica precursor to the two surfactants (C12EO10-CTAB)-saltmesophase produced mesostructured salted-silica, and its calcination producedsponge-like mesoporous silica-metal oxide (dumped meso-SiO2-CdO and meso-SiO2-ZnO) thin films. Up to ~100 % and ~50 % surface coverage could beachieved by CdO and ZnO as nano-islands over the SiO2 pore walls. Exposing themesoporous SiO2-CdO and SiO2-ZnO thin film precursors to H2S and H2Se at RTenabled the synthesis of mesoporous SiO2-CdS, SiO2-CdSe, SiO2-ZnS, and SiO2-ZnSe thin films. The MS or MSe nanoflakes could homogenously cover the porewalls of mesoporous silica by retaining the pore morphology of the MOprecursors. The H2S and H2Se reactions are slow and can be monitored using UVviVis absorption spectroscopy and EDS to elucidate the reaction mechanism andkinetics. These data showed that the reaction starts from the top surface of the MOdomains and proceeds until Si-O-M bond break. Finally, the SiO2 walls wereremoved from the meso-SiO2-CdS and meso-SiO2-CdSe films through etching ina dilute HF solution to produce mesoporous CdS (meso-CdS) and mesoporousCdSe (meso-CdSe). Surface of the meso-CdS has been modified using PEI(polyethyleneimine) and photoluminescent meso-CdS were obtained.Keywords: Mesoporous CdS, Mesoporous CdSe, Liquid Crystal Templating,Evaporation Induced Self-Assembly, Mesoporous Titania, Mesoporous Silica