Mezo yapılı silika film içerisinde cd1-xznxs nanokristallerinin katı çözeltileri

ABSTRACTSOLID-SOLUTION OF Cd1-xZnxS NANOCRYSTALS IN THECHANNELS OF MESOSTRUCTURED SILICAYAŞAR AKDOĞANM.S. in ChemistrySupervisor: Assoc. Prof. Dr. Ömer DAĞJANUARY 2006Mesostructured silica can be used as a reaction medium to produce solid-solution of Cd1-xZnxS nanocrystals as thin films. These films were synthesized fromoligo(ethylene oxide) non-ionic surfactant (CH3(CH2)11(OCH2CH2)10OH, (C12EO10)),cadmium and zinc nitrate salts ([Cd(H2O)4](NO3)2 and [Zn(H2O)6](NO3)2), water,and tetramethylorthosilicate (TMOS, as silica source) mixtures using a liquidcrystalline templating (LCT) approach and metal containing liquid crystalline (MLC)mesophase. Metal ion to surfactant mole ratio was 1.0 which determines the stabilityand structure of the mesostructured silica. The mesostructured silica film has a 3Dhexagonal structure with oriented channels. The silica pore size can be controlled bycontrolling ageing temperature and time. The pore diameter of the silica channels thataged at room temperature (RT) for two days is 4.7 nm and the one aged at 2500 C for30 minutes is 3.3 nm.Cd(II) and Zn(II) incorporated film samples can be reacted at RT under H2Satmosphere to produce zinc blend, Cd1-xZnxS nanocrystals (nano-Cd1-xZnxS-meso-SiO2) in the channels of the mesostructured silica. The band gaps of the nano-Cd1-xZnxS-meso-SiO2 vary between 2.6 eV for CdS and 4.1 eV for ZnS. The Cd (II) richnanoparticles are larger (4.4 nm) than Zn (II) rich nanoparticles (3.1 nm). The silicawall thickness that can be controlled by ageing at different temperatures confines thegrowth of the Cd1-xZnxS nanocrystals in the pores. By controlling the size of the silicachannel between 4.7 and 3.3 nm, one can control the band-gap of the CdSnanocrystals between 2.6 and 2.8 eV.Keywords: Mesostructured silica, non-ionic surfactant, mesopores, ageing, Metalcontaining Liquid Crystals, solid solution of Cd1-xZnxS, nanoparticle, semiconductor,band-gap.ii