Design and Processing of Photoresponsive Hierarchical Nanomaterials using Innovative Synthesis Routes

Abstract

Tremendous technological development and aroused energy and environmental problems forced the demand for novel materials with better functionalities. Hierarchical structures, having well defined compositional, phase and morphological features, organized as the assemblage of primary units with high surface-to-volume ratio, play an important role in advanced materials design. Especially, the building of complex hierarchical structures exhibiting tailored inorganic/organic and metal oxide/metal hybrid interfaces might be of special importance for the creation of advanced nanostructured materials having either improved or novel characteristics that bridges various scientific areas for the future diverse technological applications in catalysis, optics, energy, life science etc. Applying the bottom-up building blocks approaches in a dispersed system, it is possible to create the hierarchical structures having different morphologies, starting from aqueous, organic or colloidal precursor solutions. The hydrothermal/solvothermal method, featured by the superheated solvents and the autogenic pressure in closed system, is shown to be one of the simplest techniques for the synthesis of lD hierarchical structure in a controlled manner. Moreover, the hot wall aerosol processing, provided by high heating and cooling rates, short residence time and high surface reaction, refers to the synthesis of spherical three-dimensional (3D) nanostructured particles with uniformly distributed components and phases. The particle's composite inner structure, representing an assembly of nanosized primary units, opens the possibility for particle surface modification and functionalization. Due to exceptional optical properties emphasizing their application for light harvesting and photocatalytic applications, the examples from some wide band gap oxides including hierarchically organized hybrid Ti02 and ZnO nanoparticles as well as both down and up-conversion energy-saving luminescent materials with improved efficiency for photonic and biological applications (Y203:Eu,YblEr/TlHm, Y203:Eu@Ag, (Yl-xGdx)203:Eu, (NaYF4:Yb/Er)@ EDTAIPEGIPVPIPLGA), are considered. Employing a variety ofanalytical techniques, like XRPD, FE-SEM, analytical and high resolution transmission electron microscopy (TEM, HR-TEM), scanning tunneling electron microscopy (STEM), nanotomography, UV-Vis diffusive reflectance (UV-Vis DRS), Fourier transform infrared (FTIR) and Raman spectroscopy, photocatalytic and fluorescence measurements, to determine the new materials structures, the opportunities of the aerosol and hydro(solvo) thermal routes for the synthesis of novel hierarchically and hybrid assembled structures and nanocomposites are explored. The obtained results offer possible routes for the synthesis of hierarchically structured nanomaterials with tunable structure, morphology and functional properties and better understanding the structure-property relationship.