Synthesis and characterization of PVP/PbI2 nanocomposites

The composite organic/inorganic sols and composites containing PbI2 nanoparticles have been synthesized and studied by spectroscopic methods and TEM analysis. Prepared sols and nanocomposites contain small PbI2 nanoparticles. TEM analysis and optical spectroscopy showed that prepared PbI2 nanoparticles have size similar to 4 nm. The shift of the main absorption band relative to the bulk material of PbI2 indicates the quantum confinement effect. Obtained composites are characterized high transparency in visible spectral range and the absence of their big aggregates. Prepared sols and coatings showed luminescence dependence on the excitation wavelength in a wide range of VIS spectrum 570-610 nm due to active radiative recombination of excitons associated with the capture of excitation at the surface centers where Pb ions are located. An experimental dependence of the luminescence lifetime on the size of the synthesized nanoparticles was obtained. The growth of PbI2 nanoparticles size from 3.9 to 4.4 nm shifts the emission band into the long-wave region and reduces the luminescence lifetime from 3.5 to 2.3 ns. PbI2/PVP ratio and the size of PbI2 nanocrystals play the important role in spectral and luminescence properties of these nanocomposites.