Robert Pazik

Precursor and solvent effects in the nonhydrolytic synthesis of complex oxide nanoparticles for bioimaging applications by the ether elimination (Bradley) reaction.

Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol-gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu(3+). They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu-doped BaTiO(3) particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes.

Visualization of custom-tailored iron oxide nanoparticles chemistry, uptake, and toxicity

Nanoparticles of iron oxide generated by wearing of vehicles have been modelled with a tailored solution of size-uniform engineered magnetite particles produced by the Bradley reaction, a solvothermal metal-organic approach rendering hydrophilic particles. The latter does not bear any pronounced surface charge in analogy with that originating from anthropogenic sources in the environment. Physicochemical properties of the nanoparticles were thoroughly characterized by a wide range of methods, including XPD, TEM, SEM, DLS and spectroscopic techniques. The magnetite nanoparticles were found to be sensitive for transformation into maghemite under ambient conditions. This process was clearly revealed by Raman spectroscopy for high surface energy magnetite particles containing minor impurities of the hydromaghemite phase and was followed by quantitative measurements with EXAFS spectroscopy. In order to assess the toxicological effects of the produced nanoparticles in humans, with and without surface modification with ATP (a model of bio-corona formed in alveolar liquid), a pathway of potential uptake and clearance was modelled with a sequence of in vitro studies using A549 lung epithelial cells, lymphocyte 221-B cells, and 293T embryonal kidney cells, respectively. Raman microscopy unambiguously showed that magnetite nanoparticles are internalized within the A549 cells after 24 h co-incubation, and that the ATP ligand is retained on the nanoparticles throughout the uptake process. The toxicity of the nanoparticles was estimated using confocal fluorescence microscopy and indicated no principal difference for unmodified and modified particles, but revealed considerably different biochemical responses. The IL-8 cytokine response was found to be significantly lower for the magnetite nanoparticles compared to TiO(2), while an enhancement of ROS was observed, which was further increased for the ATP-modified nanoparticles, implicating involvement of the ATP signalling pathway in the epithelium.

Synthesis, Structure, and Optical Properties of LiEu(PO3)4 Nanoparticles

A wet chemical approach was employed for the preparation of LiEu(PO(3))(4) nanoparticles. XRD, Raman spectroscopy, TEM, SAED, and IR measurements were used in order to determine the crystal structure and morphology of the obtained product. Complete optical studies including absorption, excitation, emission, and kinetic measurements were performed. At least two components of the (5)D(0) → (7)F(0) transition were found, indicating the existence of more than one crystallographic position of the Eu(3+) ions. Asymmetry parameter R as well as the covalence of the Eu-O bond were found to decrease with the grain growth.

Crystal Structure and Morphology Evolution in the LaXO3, X = Al, Ga, In Nano-Oxide Series. Consequences for the Synthesis of Luminescent Phosphors

The LaXO(3):Tb(3+) (X = Al(3+), Ga(3+), In(3+)) perovskite nanoparticles were obtained using the nonhydrolytic treatment (Bradley reaction) of the molecular precursors of the La(O(i)Pr)(3), Al(O(i)Pr)(3), Ga(O(i)Pr)(3), In(5)O(O(i)Pr)(13), and Tb(acac)(3), respectively. It was shown that crystal structure and morphology evolution in the LaXO(3), X = Al, Ga, In nano-oxide series depended on the size and chemical properties of the X-metal atom. Formation of the LaInO(3):Tb(3+) nanoparticles is distinctly less thermodynamically demanding on contrary to the LaAlO(3):Tb(3+) and LaGaO(3):Tb(3+) since it provided crystalline product directly in the solution synthesis at 202 °C, which is the lowest reported synthesis temperature for this compound up-to-date. This behavior was ascribed to the effects directly connected with the dopant substitution (exchange of bigger La(3+) cation with smaller Tb(3+)) as well as reduction of the particle size. The size effects are mostly reflected in the expansion of the cell volume, changes of the cell parameters as well as shifting and broadening of the Raman bands. Indirectly, size reduction has also an effect on the luminescence properties through the higher probability of presence of surface and net defects as well as heterogeneous distribution of the Tb(3+) ions caused by high surface-to-volume ratio. The prepared nanophosphors show basically green emission with exception of white-green in case of the LaInO(3):Tb(3+). Strong emission quenching was found in the latter case being most likely a consequence of the nonradiative energy transfer between Tb(3+) and In(3+) as well as the presence of defects. In comparison to the Pechinis method, the LaXO(3) nanoparticles required significantly lower annealing temperature (700 °C) necessary for complete crystallization. Generally the resulting particles are distinctly smaller (5 to 25 nm) and less agglomerated (50-100 nm) depending on the reaction conditions as well as thermal treatment. For the first time, it was shown that the LaGaO(3):Tb(3+) nanopowder has crystallized in the high-temperature rhombohedral R3c phase.

Synthesis, structure and luminescence properties of KEu0.01Gd0.19Yb0.8(WO4)2 powder

Abstract The synthesis of co-doped KEu 0.01 Gd 0.19 Yb 0.8 (WO 4 ) 2 was achieved by a modified Pechini method at 750 °C. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. The Scherrers formula was used to confirm the grain sizes visualized by TEM technique. The grain sizes of about 100 nm of monoclinic KGW were successfully obtained by this methodology. In order to study spectroscopic properties of the prepared system the emission spectra were measured. The effective down- and up-conversion processes in non-resonant system were investigated.

An up-converting HAP@β-TCP nanocomposite activated with Er3+/Yb3+ ion pairs for bio-related applications

A HAP@β-TCP nanocomposite doped with Er3+/Yb3+ ion pairs was prepared using Pechini’s technique. The structural properties and morphology of the particles were studied by means of XRD, TEM, and DLS techniques. The cytotoxicity of the developed product was tested on canine osteosarcoma (D17) and murine macrophage (J774.E) cells. Determination of metronidazole release from the HAP@β-TCP nanocomposite was carried out using dynamic dialysis and ultracentrifugation techniques. Thorough analysis of the up-conversion properties of the prepared system was carried out, showing that the GRR depends strongly on the sample temperature induced by the optical density of excitation, and the particle size. Relatively short decay times and the behaviour of the GRR pointed towards the enhanced contribution of non-radiative processes feeding the red emission.

Preferential site substitution of Eu3+ ions in Ca10(PO4)6Cl2 nanoparticles obtained using a microwave stimulated wet chemistry technique

The Eu3+ doped Ca10(PO4)6Cl2 nanocrystalline powders were synthesized using a microwave stimulated technique. Additional post heat treatment in the temperature range 800–1100 °C was applied in order to improve the crystallinity of the final product and eliminate the residual amorphous phase. Detailed structural characterization was performed by X-ray diffraction (XRD), Raman and infrared (IR) spectroscopy, transmission electron microscopy (TEM) and X-ray fluorescence (EDX). The optical properties of the Ca10(PO4)6Cl2 samples doped with different Eu3+ concentrations (0.5–5 mol%) were determined by measuring excitation, emission spectra and luminescence. TEM images confirmed the nanoscale nature of the final product with a primary particle size of about 60 nm and a hydrodynamic size of 200 nm when the product was dispersed in Milli-Q purified water (MQ) without further stabilization. The analysis of the 5D0 → 7F0 transition points out that for low concentration Ca(II) (A) site is preferentially substituted whereas increase of Eu3+ above 2 mol% results in domination of the Eu3+ cations located at Ca(I) (B) site. Increase of annealing temperature leads to an increase of the 5D0 → 7F0 intensity associated with the Eu3+ at A site. Preferential site substitution can be solved by analysis of the optical properties of the Eu3+ ion. The Judd–Ofelt parameters were calculated using simplified formalisms. The mechanism of concentration quenching process was identified as a dipole–dipole interaction.

Multifunctional nanocrystalline calcium phosphates loaded with Tetracycline antibiotic combined with human adipose derived mesenchymal stromal stem cells (hASCs).

Osteoconductive drug delivery system composed of nanocrystalline calcium phosphates (Ca10(PO4)6(OH)2/β-Ca3(PO4)2) co-doped with Yb(3+)/Er(3+) ions loaded with Tetracycline antibiotic (TC) was developed. Their effect on human adipose derived mesenchymal stromal stem cells (hASCs) as a potential reconstructive biomaterial for bone tissue regeneration was studied. The XRD and TEM measurements were used in order to determine the crystal structure and morphology of the final products. The characteristics of nanocomposites with the TC and hASCs as potential regenerative materials as well as the antimicrobial activity of the nanoparticles against: Staphylococcus aureus ATCC 25923 as a model of the Gram-positive bacteria, Escherichia coli ATCC 8739 of the Gram-negative bacteria, were shown. These combinations can be a promising material for theranostic due to its regenerative, antimicrobial and fluorescent properties.

Effect of lithium substitution on the charge compensation, structural and luminescence properties of nanocrystalline Ca10(PO4)6F2 activated with Eu3+ ions

Eu3+ and Li+ ion co-doped fluorapatite (Ca10(PO4)6F2) nanocrystals were fabricated using a microwave stimulated hydrothermal technique followed by heat treatment at 500 °C. The concentration of Eu3+ ions was set to be 1 mol% and that of the Li+ ions was in the range of 0.5–5 mol% to investigate the site occupancy preference and charge compensation co-doping. The structural and morphological properties of the obtained samples were determined by using XRD (X-ray powder diffraction) and TEM (transmission electron microscopy) techniques as well as IR (infrared) and micro-Raman spectroscopy. The particle size was verified and calculated by the Rietveld method being in the range of 70–95 nm. The luminescence properties (the emission, excitation spectra and emission kinetics) of the Eu3+ ion-doped fluorapatite depending on the co-dopant (Li+ ions) were recorded. Significantly, fluorescence quenching by OH− groups was eliminated by F- ions and the luminescence intensity was enhanced by co-doping with Li+ ions. The simplified Judd–Ofelt (J–O) theory has been performed to explain a detailed analysis of the luminescence spectra.

Up-conversion emission and in vitro cytotoxicity characterization of blue emitting, biocompatible SrTiO3 nanoparticles activated with Tm3+ and Yb3+ ions

Functional SrTiO3 nanoparticles activated with a broad concentration range of Tm3+ and Yb3+ ions were obtained utilizing the citric route. The effect of the sintering temperature and optically active co-dopant concentration on the structural and up-conversion emission properties was studied by using XRD (X-ray powder diffraction) and spectroscopic techniques (emission, power dependence, emission kinetics). The particle size was verified by the TEM technique being in the range of 20–90 nm depending on the annealing temperature. It was shown that cross-relaxations contribute to depopulation of both 1G4 and 3H4 levels, whereas some of them populate the 3H4 level. These processes are strongly dependent on the concentration of Tm3+ and are responsible for the specific interplay between blue and NIR emissions. Extraordinary short decays were recorded due to the relatively high concentrations of rare earths, structural features of the host matrix, extended surface area and contribution of the non-radiative processes. The cytotoxic activity of the nanoparticles to J774.E murine macrophages and U2OS human osteosarcoma cells was assessed showing that SrTiO3:Tm3+/Yb3+ nanoparticles are biocompatible and can be potentially used in further bio-related applications such as active implant layers or injectable medical cement ingredients.