Aerosol assisted processing of hierarchically organized functional nanoparticles

Abstract

Global warming, climate change and natural resources depletion forces tremendous technological and scientific research activities for the development of next generation of materials able to address both the energy and environmental problems. This implies an exciting progress in the field of nanoscience and nanotechnology, particularly regarding the control synthesis of nanoscaled materials that might have a great potential for use in solid-state functional materials and devices, like phosphors, sensors, photovoltaics, catalysts, drug delivery carriers etc. The feasibility of the dispersion phase-aerosol route for the generation of innovative nanomaterials having advanced optical properties for solving energy/environmental problems is here presented. Particularly, the opportunities of the hot wall aerosol processing, provided by high heating and cooling rates, short residence time and high surface reaction, is demonstrated for the synthesis of spherical three-dimensional (3D), hierarchically organized nanostructured particles with uniformly distributed components and phases. The particles composite inner structure, representing an assembly of nanosized primary particles, opens the possibility for particle surface modification and functionalization emphasizing their application in photovoltaics, energy transfer and bioimaging. The diverse levels of structural, morphological and timctional complexity are explored by means of appropriate selection of different precursor solutions, either true or colloid, surface modification and proper selection of rare-earth based dopants for the generation of either photocatalytic titanium (IV) oxide or Yb3+, Er3+, codoped yttrium(III) oxide-based phosphor particles. Their advanced optical properties as the consequence of the particle nanostructure uature are proved by using various characterization techniques like x-ray powder diffraction (XRPD), scanning electron microscopy (SEM, FE-SEM), analytical and high-resolution transmission electron microscopy (TEMIHR-TEM) in combination with energy dispersive x-ray analysis (EDAX), selected area electron diffraction (SAED) and nanotomography. The optical properties and surface structure were analyzed by UV-Vis diffusive reflectance (UV-Vis DRS), Fourier transform infrared (FTIR) spectroscopy and by fluorescence measurements in the near infrared region. The obtained results offer ageneral route for the synthesis of nanomaterials with tunable structure, morphology and optical properties.