The Feasibility of Soft Chemical Routes in the Processing of Hierarchically Organized Functional Nanoparticles

Global warming, climate change and natural resources depletion forces tremendous technological and scientifical research activities for the development of next generation of material 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 hierarchically organised nanoscaled particles that might have a great potential for use in solid-state functional materials and devices, like phosphors, sensors, photovoltaics, catalysts, drug delivery carriers, etc. Among the diversity of the soft chemical approaches for nanomaterials processing, synthesis through dispersion phase (aerosol) enables generation of ultrafme, either single or complex powders with controlled stoichiometry, chemical and phase content provided by high heating and cooling rates, short residence time and high surface reaction and is here 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. When one-dimensional (1D) nanomaterials are considered, the hydrothermal method (HT) is shown to be one of the simplest techniques for their obtaining. With the help of various analyzing technique like XRPD, SEMIEDS, FE-SEM, TEM, HR-TEM, STEM, nanotomography, UV-Vis diffusive reflectance (UV-Vis DRS), Fourier transform infrared (FTIR) spectroscopy and luminescence measurements, the opportunities of both methods for the synthesis of novel functional materials based on Gd20 3:Eu, Y203:Eu,Yb,Er,Ho,Tm, (Y1-xGdx)203:Eu, Y3Als012:Ce, NaYF4, Ti02 etc. for solving energy/environmental problems will be reviewed. The obtained results offer a general route for the synthesis of hierarchical nanomaterials with tunable structure, morphology and optical properties

Optically active nanomaterials for environmental remediation

In recent years optically active nanomaterials have opened up a number of frontiers, especially in life science and environmental protection. Novel hybrid nanomaterials based on wide band gap oxides (TiO2) and Ln3+ doped rare earth compounds (down- and up-conversion luminescence materials) obtained through innovative processing will be presented from the viewpoint of their potential application for light harvesting and photocatalysis

Hydrothermal synthesis of optically active rare earth fluorides

Hydrothermal method has great interest in recent years for synthesis of nano- and micro- crystals of upconverting rare earth (RE) fluorides, with controlled morphology and high purity, under high temperatures and pressures. Some surfactants (ethylenediaminetetraacetic acid (EDTA), polyvinylpyrrolidone (PVP), oleic acid (OA)) along with different type of solvents are added in order to control size, morphology and crystalline phases of particles. In this work Yb3+/Er3+ co-doped YF3 and NaYF4 fine powders were synthesized using the hydro/solvo thermal method in the present of EDTA as a complexing agent. Effect of the processing parameters on the particles crystal structure, morphology and optical properties were estimated on the basis of X-ray diffractometry (XRPD), scanning electron microscopy (SEM) and photoluminescence measurement. It was shown that in terms of increased concentration of RE ions in aqueous solvent media the hexagonal β-NaYF4:Yb3+/Er3+ phase with the most efficient green emission were synthesized. On the other side, the occurrence of cubic α-NaYF4:Yb3+/Er3+ and orthorhombic YF3:Yb3+/Er3+ were observed with a decrease of the RE ions when ethanol is used as a solvent. All of the samples provide intense green emission after been excited with infrared light (λ = 978 nm), which is assigned to the Er3+ (2H11/2, 4S3/2) → 4I15/2 electronic transitions

The feasibility of aerosol route in the optically active nanoparticles processing

Among the diversity of the soft chemical approaches for nanomaterials processing, synthesis through dispersion phase (aerosol) enables generation of ultrafine, either single or complex powders with controlled stoichiometry, chemical and phase content provided by high heating and cooling rates, short residence time and high surface reaction. This may favors to the formation of either amorphous, nanocrystalline or metastable phases that might have a huge impact in the processing of advanced functional materials having novel and unique structures and properties. 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 functional 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 a range of up-conversion phosphor particles. With the help of various analyzing techniques like XRPD, SEM/EDS, FE-SEM, TEM, HR-TEM, STEM, nanotomography, UV-Vis diffusive reflectance (UV-Vis DRS), Fourier transform infrared (FTIR) spectroscopy and luminescence measurements, the synthesis of novel functional materials based on Y2O3:Eu,Yb,Er, NaYF4 and TiO2 for solving energy/environmental problems will be presented. The obtained results offer a general route for the synthesis of nanomaterials with tunable structure, morphology and optical properties

Optical Properties of Nanostructured Particles Synthesized by Spray Pyrolysis Route

Poster presented at the International Symposium on Advanced Complex Inorganic Nanomaterials (ACIN 2011), September 11-14, 2011 - Namur, Belgiu

Nanostructured Y2O3 Particles Doped with Europium Synthesized by Aerosol Route

Y2O3 doped with europium is a well known red phosphor material employed in modern high-resolution display devices such as plasma display panels (PDP) and field emission displays (FED). The incorporation of gadolinium in the yttria matrix may significantly contribute to the luminescent properties and x-ray absorption coefficient thus increasing the field of application in optoelectronic devices such as ceramic scintillators for computed tomography. In this work, the nanostructured particles of Y 2 O 3 doped with Eu 3+ were processed through the spray pyrolysis method. Synthesis was carried out with an ultrasonic aerosol device operating at 1.3 MHz in air atmosphere connected with a triple-zone tubular flow reactor (473-973-1173K). Particles were submitted t o post- thermal treatments at temperatures among 1273 and 1 573K for 12 hours in order to increase the crystallinity and uniform distribution of doped centers. Morphology, structure, crystallinity and chemical characteristics were studied by XRD, SEM-EDS, TEM-HRTEM and SAED. The particles obtained are spherical, having narrow size distributions, high compositional homogeneity and are in unagglomerated state. The effects of synthesis parameters were followed and discussed in terms of particle structure and morphology

Dense spherical rare earth oxide particles synthesis via spray pyrolysis of polimeric precursor solution

Poster presented at 12th Annual Conference of the Materials Research Society of Serbia - YUCOMAT 2010, Herceg Novi, Montenegro, September 6–10, 2010

The morphology, structure and luminescent properties of Gd2O3:Eu synthesized by aerosol route and high energy ball milling

Poster presented at the Seventh International Conference on Mechanochemistry and Mechanical Alloying - INCOME 2011, Herceg Novi, Montenegro, August 31 – September 3, 201

Dense spherical rare oxide particles synthesis via spray pyrolysis of polymeric precursor solution

Europium-doped (Y0.5Gd0.5)2O3 phosphor powder is synthesized via spray pyrolysis of polymeric precursor solution obtained by dissolving the stoichiometric amount of corresponding metal nitrates in ethylenediaminetetraacetic acid (EDTA) - ethylene glycol (EG) mixture. The 0.1M true stable solution is obtained after pH correction with NH4OH (final pH=8.7). Ultrasonically (1.3MHz) generated aerosol droplets are decomposed at 550 oC in argon atmosphere. Following the initial attempt for obtaining dense, nanostructured spherical particles of pure (Y0.5Gd0.5)2O3:Eu3+ phase, as-prepared dark-gray powder is additionally thermally treated for 12 h in air up to 1100 oC. The particle morphology is analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Phase identification is performed by X-ray powder diffraction (XRPD) based on which the structural refinement through Rietveld method was done. Particle chemical purity is confirmed through EDS analysis, while laser particle sizer is used for determination of the particle size distribution.Poster: [https://hdl.handle.net/21.15107/rcub_dais_220

Aerosol route in processing of nanostructured functional materials

The diversity and potentials of the aerosol route for making functional materials at the nano size level are reviewed. Among the methods currently used for nanophase processing, synthesis through dispersion phase (aerosol) enables generation of ultrafine, either single or complex powders with controlled stoichiometry, chemical and phase content provided by high surface reaction, high heating and cooling rates and short residence time. It represents a "bottom-up" chemical approach and provides control over a variety of important parameters for particle processing. This may favors to the formation of either amorphous, nanocrystalline or metastable phases implying a huge impact in the search for advanced functional materials having novel and unique structures and properties. Particularly, the opportunities of the hot wall aerosol synthesis, i.e. spray pyrolysis, for the generation of ultrafine spherical particles with uniformly distributed components, phases and nano-clustered inner structure and luminescence properties is demonstrated with various analyzing tecniques like XRPD, FE-SEM, HR-TEM, STEM and nanotomography. Following the initial attempts, a more detailed aspect of the several phosphor particles generation based on Gd2O3:Eu, Y2O3:Eu, (Y1-xGdx)2O3:Eu and Y3Al5O12:Ce is reviewed highlighting the research activities in the Institute of Technical Sciences of SASA, Serbia. © 2009 Hosokawa Powder Technology Foundation