Design and Processing of Photoresponsive Hierarchical Nanomaterials using Innovative Synthesis Routes

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

Production potential of the soil and the basic elements of productivity of the most widely spred sessil types in the u. N.P. „Đerdap”

This paper is on the results of the soil and its production potential in the types of forests of sessile oaks (Quercus petraea) in the area of the National Park „Đerdap” in the community units of Zlatica, Đerdap, Štrbačko korito, Desna reka and Kožica. There are the most widely spread types of the sprout forests of the sessile oaks in the research area, deep deluvium, luvisoil, eutric cambsoils, and a great number of subtypes of acid brown soil. Considering the fact that the production potential of the defined types of soil depends on the depth, skeleton and other physical characteristics which determine acception, keeping and moving of water and this means that the production value of the studied soils is in the direct correlation with physical-geographical conditions of the environment. Taking into account that solum is well developed and the low contents of skeleton, all the studied soil in the most widely spread types of sessile oaks in the area of N.P. „Đerdap”, are very productive natural habitats. The exception is acid brown soil, which characteristics vary as well as their production potential. Apart from a good production potential of the studied soils within this paper, sessile forests in the researched areas irrationally use production potential of the habitat. In the research area in the last 20 years, the processes of devitalizing and the appearance of decaying of sessile oaks are expressed. In the sessile forests of Serbia, there are forests of the production and protection character, and the structure of the sessile forests at global level is characterized by not normal state with domination of middle aged and in great extent mature withering ingredients, what is the main cause of insufficiently used good potential of the soil

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

The development of microstructure and crystal phases during sintering of multiphase materials based on ZnO and their correlation with the nonlinear current-voltage properties

Rad predstavlja nastavak dosadašnjih istraživanja iz oblasti višekomponentnih materijala na bazi ZnO - Bi2O3 - MO, koji poseduju veliku nelinearnost strujno-naponske karakteristike. Nelinearno ponašanje sistema, koje se opisuje izrazom: J=C•Kα gde je J-gustina struje, K-električno polje, α-koeficijent nelinearnosti definisan kao d(logJ)/d(logK), C-konstanta, javlja se dodavanjem cink oksidu jona sa većim jonskim radijusom od radijusa katjona osnovne faze, koji obrazuju intergranularni sloj na granici zrna. Dodavanje oksida prelaznih metala, kao što su oksidi kobalta ili mangana, omogućuje značajan porast koeficijenta nelinearnosti, dok oksidi nikla ili hroma povećavaju stabilnost strujno-naponske karakteristike. Mikrostruktura višekomponentnih sistema na bazi ZnO sa malim sadržajem aditiva obrazuje se u procesu reakcionog sinterovanja sa tečnom fazom. Na njeno formiranje utiču uslovi sinterovanja: temperatura, obzirom na termički aktivirane procese koji se dešavaju tokom sinterovanja višekomponentnih sistema (difuzija, obrazovanje tečne faze) i termički aktivirane hemijske reakcije izmedju polaznih oksida (obrazovanje pirohlora, spinela, polimorfne transformacije Bi2O3, supstitucija rešetke ZnO); zatim vreme sinterovanja i brzina hladjenja, izbor aditiva i si. U višekomponentnim sistemima na bazi ZnO razvoj faza, odnosno mikrostrukture, odvija se kroz nekoliko paralelnih procesa koji se interferiraju. Pri tome je proces sinterovanja dominirajući za obrazovanje faze-zma ZnO, dok je obrazovanje faza intergranularnog sloja rezultat reagovanja polaznih komponenti u čvrstoj i tečnoj fazi. Termički aktivirano difuziono kretanje unutrašnjih defekata cink oksida i katjona aditiva utiču na formiranje Čvrstih rastvora na bazi osnovnih konstituenata. Nelinearnost strujno-naponske karakteristike, koja je evidentna kod višekomponentnih sistema na bazi ZnO sa malim sadržajem aditiva, direktno je korelisana rezultujućom mikrostrukturom. Polazeći od mehanizama formiranja nelinearnog efekta, kao i od mehanizama formiranja mikrostrukture, nestehiometrija faze ZnO i hernija granice zrna ZnO, fazni sastav intergranularnog sloja i homogenost mikrostrukture predstavljaju polazne hipoteze na kojima se baziraju istraživanja u ovoj oblasti i u najvećoj rneri oni opredeljuju naredne istraživačke pravce..

Aerosol synthesis of phosphor based on Eu3+ activated gadolinium oxide matrices

Poster presented at the Seventh International Conference on Ceramic Processing Science, Inuyama, Japan, May 15-18, 200

Aerosol synthesis of phosphor based on Eu3+ activated gadolinium oxide matrices

Poster presented at the Seventh International Conference on Ceramic Processing Science, Inuyama, Japan, May 15-18, 200

Synthesis of hierarchically structured Y2O3:Eu3*@ Ag nanocomposites with plasmon enhanced luminesencence via ultrasonic spray pyrolysis

Y2O3:Eu3+@Ag nanocomposites have been successfully synthesized by ultrasonic spray pyrolysis (USP) and examined to reveal effects of surface plasmon resonance, associated to silver nanoparticles, to the luminescence efficiency of Y2O3: Eu3+ red-emitting phosphors. Various Ag concentrations (1, 2.5 and 5 wt. %) and heat-treatment regimes (as prepared, 2h, 12h) were applied to understand how size and distribution of the Ag nanoparticles affect the luminescence efficiency. Samples were characterized by TEM, XRPD and STEM to evaluate crystal structure and distribution of Eu3+ in Y2O3 matrix. In terms of Y, O and Eu ions, uniform distribution was observed in the particles interior, while the Ag is present at the particles surface showing that USP is feasible for synthesis of hierarchically organized Y2O3:Eu3+@Ag. In the case of higher Ag concentration, a deviation from uniform and finely distributed Ag nanoparticles on Y2O3:Eu3+ surface was detected having detrimental effect to the plasmon enhanced luminescence. Regardless from silver concentrations, all heat treated samples exhibited superior luminescence with respect to asprepared ones, while decrease of luminescence efficiency was detected with the increase of Ag concentration. The most intense red luminescence at 612 nm which is due Eu3+ 5D0→7F2 transition was observed in Y2O3:Eu3+@Ag system for sample with 1wt% Ag, annealed for 12 hours

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

Kinetics of nanocrystalline phase transformations in spray pyrolysed ZnO particles

The thermal behavior of ZnO powder obtained by ultrasonic spray pyrolysis of nitrate solution (c=0.8mol/dm3, D0=2.695µm, Tmax=6000C, FG=1.2dm3/min) was investigated using non-isothermal differential scanning calorimetry (DSC, heating rates 5, 10, 15, 20O/min). The exothermic heat effects at the temperature range from 350 to 5000C were linked to particles structural data obtained by XRD, SEM and TEM analysis. Produced particles are characterized by uniform submicronic size (D=800nm, BET=4.94m2/g), high phase purity and granular or circular “open” surface due to the presence of primary crystallites (d= 20nm). Observed structural changes during heating of this powder were attributed to simultaneous processes of nucleation and growth of primary crystallites inside the produced particles

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