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

Facile synthesis of hydrophilic polymer-capped upconverting NaYF4:Yb,Er particles

Over the last decade, solvothermal decomposition of organometallic compounds has been indicated as one of the most convenient method for the synthesis of monodisperse lanthanide doped upconverting fluorides. Due to their hydrophobic nature such particles could not be used for a conjugation of the molecular targeting agents which is necessary for optical imaging of biological tissues. In this work, hydrophilic NaYF4:Yb,Er (17 mol% Yb; 3mol% Er) nanoparticles were synthesized by facile one-pot hydrothermal synthesis performed with a help of chitosan (CS) and poly(acrylic acid) (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. The obtained results implied that particle size, shape and surface characteristics are dependent on the polymer choice. Although both powders crystallize in the same crystal arrangement (cubic, Fm-3m) more intense red emission, assigned to the Er3+ 4F9/2 → 4I15/2 electronic transitions, characterize spherical NaYF4:Yb,Er@CS particles. To asses a biological safety of their use, viability of the human gingival fibroblasts (HFG) was additionally tested by a colorimetric MTT assay

Facile synthesis of hydrophilic polymer-capped upconverting NaYF4:Yb,Er particles

Over the last decade, solvothermal decomposition of organometallic compounds has been indicated as one of the most convenient method for the synthesis of monodisperse lanthanide doped upconverting fluorides. Due to their hydrophobic nature such particles could not be used for a conjugation of the molecular targeting agents which is necessary for optical imaging of biological tissues. In this work, hydrophilic NaYF4:Yb,Er (17 mol% Yb; 3mol% Er) nanoparticles were synthesized by facile one-pot hydrothermal synthesis performed with a help of chitosan (CS) and poly(acrylic acid) (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. The obtained results implied that particle size, shape and surface characteristics are dependent on the polymer choice. Although both powders crystallize in the same crystal arrangement (cubic, Fm-3m) more intense red emission, assigned to the Er3+ 4F9/2 → 4I15/2 electronic transitions, characterize spherical NaYF4:Yb,Er@CS particles. To asses a biological safety of their use, viability of the human gingival fibroblasts (HFG) was additionally tested by a colorimetric MTT assay

Facile synthesis of hydrophilic polymer-capped upconverting NaYF4:Yb,Er particles

Over the last decade, solvothermal decomposition of organometallic compounds has been indicated as one of the most convenient method for the synthesis of monodisperse lanthanide doped upconverting fluorides. Due to their hydrophobic nature such particles could not be used for a conjugation of the molecular targeting agents which is necessary for optical imaging of biological tissues. In this work, hydrophilic NaYF4:Yb,Er (17 mol% Yb; 3mol% Er) nanoparticles were synthesized by facile one-pot hydrothermal synthesis performed with a help of chitosan (CS) and poly(acrylic acid) (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. The obtained results implied that particle size, shape and surface characteristics are dependent on the polymer choice. Although both powders crystallize in the same crystal arrangement (cubic, Fm-3m) more intense red emission, assigned to the Er3+ 4F9/2 → 4I15/2 electronic transitions, characterize spherical NaYF4:Yb,Er@CS particles. To asses a biological safety of their use, viability of the human gingival fibroblasts (HFG) was additionally tested by a colorimetric MTT assay

Effects of different polymers and solvents on crystallization of theNaYF4:Yb/Er phase

Up-converting NaYF4:Yb,Er nanoparticles were obtained by polymer-assisted solvothermal synthesis using a common solution of hydrated RE nitrates in ethanol or ethylene glycol. It was shown that polymer choice (polyacrylic acid—PAA, polyvinylpyrrolidone—PVP and chitosan—CS) controls the size and shape of NaYF4:Yb,Er nanoparticles, while the solvent type and pH value affect their crystallinity. Consequently, the spherical nanoparticles of a cubic (α) phase, the average size of which ranged from 60 to 140 nm, were obtained either when PVP/ethanol or PVP/ethylene glycol were used solely during synthesis, whereas NaOH addition induced hexagonal (β) phase nucleation. The formation of the hierarchically organized spherical aggregates and nanofoils was observed when CS and PAA were used during synthesis, respectively. The average crystallite size, microstrain, doping level, lattice parameters, as well as, the presence of the certain ligands on the particle surface were determined and correlated with the intensity of visible-light emission observed under 980 nm laser-diode excitation.This is the peer-reviewed version of the article: Vukovic, M., Dinic, I., Nikolic, M.G., Marinkovic, B.A., Costa, A.M.L.M., Radulovic, K., Milosevic, O., Mancic, L., 2019. Effects of different polymers and solvents on crystallization of theNaYF4:Yb/Er phase. Bull Mater Sci 43, 2. [https://doi.org/10.1007/s12034-019-1975-1

Facile synthesis of hydrophilic polymer-capped upconverting NaYF4:Yb,Er particles

Over the last decade, solvothermal decomposition of organometallic compounds has been indicated as one of the most convenient method for the synthesis of monodisperse lanthanide doped upconverting fluorides. Due to their hydrophobic nature such particles could not be used for a conjugation of the molecular targeting agents which is necessary for optical imaging of biological tissues. In this work, hydrophilic NaYF4:Yb,Er (17 mol% Yb; 3mol% Er) nanoparticles were synthesized by facile one-pot hydrothermal synthesis performed with a help of chitosan (CS) and poly(acrylic acid) (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. The obtained results implied that particle size, shape and surface characteristics are dependent on the polymer choice. Although both powders crystallize in the same crystal arrangement (cubic, Fm-3m) more intense red emission, assigned to the Er3+ 4F9/2 → 4I15/2 electronic transitions, characterize spherical NaYF4:Yb,Er@CS particles. To asses a biological safety of their use, viability of the human gingival fibroblasts (HFG) was additionally tested by a colorimetric MTT assay

Microstructural and Optical Properties of MgAl2O4 Spinel: Effects of Mechanical Activation, Y2O3 and Graphene Additions

Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl2O4 was produced by a solid-state reaction between MgO and α-Al2O3 powders. Mechanical activation for 30 min in a planetary ball mill was used to increase the reactivity of powders. Yttrium oxide and graphene were added to prevent abnormal grain growth during sintering. Samples were sintered by hot pressing under vacuum at 1450 °C. Phase composition and microstructure of sintered specimens were characterized by X-ray powder diffraction and scanning electron microscopy. Rietveld analysis revealed 100% pure spinel phase in all sintered specimens, and a decrease in crystallite size with the addition of yttria or graphene. Density measurements indicated that the mechanically activated specimen reached 99.6% relative density. Furthermore, the highest solar absorbance and highest spectral selectivity as a function of temperature were detected for the mechanically activated specimen with graphene addition. Mechanical activation is an efficient method to improve densification of MgAl2O4 prepared from mixed oxide powders, while additives improve microstructure and optical properties

β-NaYF4:Yb,Tm@TiO2-Acac core-shell structure for efficient photocatalysis

Novel hybrid core shell structure with extensive absorption was synthesized by a two-step wet chemical route. Up-converting β-NaYF4:Yb,Tm core was obtained through EDTA assisted hydrothermal process, while the shell of anatase TiO2-Acetylacetonate charge transfer complex (TiO2-Acac) was formed over these via sol-gel method. Tetracycline was used to investigate photocatalytic efficiency of obtained structure under irradiation of reduced power Vis and NIR spectra. Owing to the fact that 1D2→3F4 and 1G4→3H6 emission of Tm3+ matches well with the absorption edge of TiO2-Acac, radiation-reabsorption and FRET processes improve the overall generation of reactive oxygen species and degradation of tetracycline. Beside it, formation of tetracycline intermediates immediately after the addition of this novel hybrid core-shell structures, making them a promising material for water purification through the synergy of catalytic and photocatalytic processes

β-NaYF4:Yb,Tm@TiO2-Acac core-shell structure for efficient photocatalysis

Novel hybrid core shell structure with extensive absorption was synthesized by a two-step wet chemical route. Up-converting β-NaYF4:Yb,Tm core was obtained through EDTA assisted hydrothermal process, while the shell of anatase TiO2-Acetylacetonate charge transfer complex (TiO2-Acac) was formed over these via sol-gel method. Tetracycline was used to investigate photocatalytic efficiency of obtained structure under irradiation of reduced power Vis and NIR spectra. Owing to the fact that 1D2→3F4 and 1G4→3H6 emission of Tm3+ matches well with the absorption edge of TiO2-Acac, radiation-reabsorption and FRET processes improve the overall generation of reactive oxygen species and degradation of tetracycline. Beside it, formation of tetracycline intermediates immediately after the addition of this novel hybrid core-shell structures, making them a promising material for water purification through the synergy of catalytic and photocatalytic processes

Morphological and structural characterization of spinel MgAl2O4

Magnesium aluminate has spinel structure and very good mechanical, chemical, and thermal properties. Owing to these properties, it has a wide range of applications including refractory ceramics, optically transparent ceramic windows and armors. Its low dielectric permeability and low loss tangent enable its using for integrated electronic devices, as well. Furthermore, as a porous ceramic, magnesium aluminate has important application as humidity sensor, catalyst and filter for waste water purification. In this paper, synthesis and characterization of MgAl2O4 was performed. Stochiometric ratio of MgO and Al2O3powders was mixed and calcined within the temperatures range 1500-1800 oC to produce pure spinel phase. Thereafter pellets were crushed and treated in planetary ball mill for 60 minutes to obtained fine grain. All powders, calcined and milled, were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature denser samples but more fragile have been synthesized. Milling for 1 hour leads to crumble of bigger particles and getting finer, single phase powders. XRPD and Raman spectroscopy showed disorder in crystal structure after milling