Hybrid luminescent materials based on semiconductor nanocrystals and doped functional organic stabilizers

         The project focuses on the creation and study of new fluorescent hybrid materials consisting of doped semiconductor nanocrystals and functional organic shell. Such materials are promising for the imaging of biological objects , the development of lasers and electroluminescent devices. In these materials, semiconductor nanocrystals provide high efficiency absorption of the exciting light impurity atoms in them - necessary luminescence wavelength of minimum absorption in the blood and tissues and the relaxation time of the luminescence significantly exceeding the relaxation time of the luminescence of biological tissues. The organic stabilizer nanocrystals provides stability in biological environments and comprises functional groups that enable chemical attachment to the protein for subsequent selective securing of the entire structure at a given cell type.
    First : The method of synthesis of functionalized polyethylene glycol ligands on a polymeric support. Developed methods for the synthesis of nanocrystals CdSe, alloyed elements I and III , as a promising new laser media ; a study of the resulting nanoparticles complex methods.
  Studies have shown that alloying with silver nanoparticles CdSe, unlike copper, enhances the luminescence quantum yield. At low doping levels (<1 % Ag / Cd) in the luminescence spectra in addition to the interband luminescence ( MZL ) arises wide wavelength band with a maximum at 1.85 eV. She is excited by radiation with lower energy than MZL . The position and the relative luminescence intensity of the new band is not detected depending on the size of the nanocrystals . At high doping level (up to 18 % Ag / Cd) there is another wavelength band luminescence , which can be excited by light with less energy than MZL . The influence of the precursor on the morphology of silver nanocrystals. Varying the nature of the precursor and the amount of silver , even at a constant temperature of synthesis can be controlled compact size ( spherical , oval ) nanocrystals in the range of 3 to 12 nm to obtain branched or nanocrystals ( multipody ) with long legs 150 nm at a diameter of 3 feet - 4 nm. For prolonged storage sols nanocrystals CdSe (Ag) is their aging. It manifests itself in an increase in non-uniform intensity over the spectrum relative to the intensity of the wavelength band MZL low doping level , and conversely, a decrease in the wavelength band intensity relative intensity MZL at high doping level . It is shown that simultaneous administration of indium and silver slows aging sols doped nanoparticles. Discover the unique double peak MZL arising from CdSe nanocrystals with erbium doping showed that both peaks arise from the same excited state. Getting a double peak MZL possible only on branched nanocrystals . Getting a double peak MZL possible when replacing erbium zinc and even cadmium. Confirmed hypothesis of the origin of the second peak MZL by recombination of an exciton in the leg multipoda .

KEYWORDS
Nanocrystalline semiconductors , quantum dots CdSe, doping , luminescence, multipody PEG ligands .