Ses üstü sayesinde mikro ve nanokristal sentezi

The application of ultrasound can facilitate reactions in milder conditions. In this thesis, two different inorganic materials with interesting properties were synthesized by the ultrasonic irradiation. The first chapter presents an introduction to the basic concepts of sonochemistry. The factors affecting the cavitational effect are discussed. The second chapter provides a fast and simple method for the synthesis of lanthanide doped(Yb3+(20%)/Er3+(2%) or Yb3+(20%)/Tm3+(2%)) upconverting NaYF4 crystals by the application of ultrasonic waves. The optimized reaction conditions yields the synthesis of ß-NaYF4 microparticles and ?-NaYF4 nanoparticles at T< 80°C in aqueous phase. The crystal structure was determined by the X-ray diffraction and morphology was investigated with scanning electron microscopy. Upconverting crystals were excited with a continuous wave laser diode in the near infrared region. In Chapter 3, a one step, simple route was developed for the aqueous phase synthesis of CdS quantum dots with ultrasound irradiation. As the precursor, bulk CdO with Na2S or elemental sulfur was utilized. 2-Mercaptopropionic Acid (2-MPA) or Poly(Acrylic Acid) PAA (5100g/mol) were used as the capping agent. The influence of the reaction conditions on the size and fluorescence was investigated. 2-MPA showed higher fluorescence intensity and narrower FWHM than PAA coated samples at any investigated temperature. Samples synthesized at T=70°C showed better crystallinity and higher quantum yield (38% with respect to Rhodamine B dye). The narrowest emission bandwidth and smallest size was obtained when elemental sulfur was utilized as the precursor.