Marcin Runowski

Synthesis and Organic Surface Modification of Luminescent, Lanthanide-Doped Core/Shell Nanomaterials (LnF3@SiO2@NH2@Organic Acid) for Potential Bioapplications: Spectroscopic, Structural, and in Vitro Cytotoxicity Evaluation

A facile coprecipitation reaction between Ce(3+), Gd(3+), Tb(3+), and F(-) ions, in the presence of glycerine as a capping agent, led to the formation of ultrafine, nanocrystalline CeF3:Tb(3+) 5%, Gd(3+) 5% (LnF3). The as-prepared fluoride nanoparticles were successfully coated with an amine modified silica shell. Subsequently, the obtained LnF3@SiO2@NH2 nanostructures were conjugated with 4-ethoxybenzoic acid in order to prove the possibility of organic modification and obtain a new functional nanomaterial. All of the nanophosphors synthesized exhibited intense green luminescence under UV light irradiation. Based on TEM (transmission electron microscopy) measurements, the diameters of the cores (≈12 nm) and core/shell particles (≈50 nm) were determined. To evaluate the cytotoxic activity of the nanomaterials obtained, their effect on human erythrocytes was investigated. LnF3 nanoparticles were bound to the erythrocyte membrane, without inducing any cytotoxic effects. After coating with silica, the nanoparticles revealed significant cytotoxicity. However, further functionalization of the nanomaterial with -NH2 groups as well as conjugation with 4-ethoxybenzoic acid entailed a decrease in cytotoxicity of the core/shell nanoparticles.

Magnetic and luminescent hybrid nanomaterial based on Fe3O4 nanocrystals and GdPO4:Eu3+ nanoneedles

A bifunctional hybrid nanomaterial, which can show magnetic and luminescent properties, was obtained. A magnetic phase was synthesized as a core/shell type composite. Nanocrystalline magnetite, Fe3O4 was used as the core and was encapsulated in a silica shell. The luminescent phase was GdPO4 doped with Eu3+ ions, as the emitter. The investigated materials were synthesized using a coprecipitation method. Encapsulated Fe3O4 was “trapped” in a nano-scaffold composed of GdPO4 crystalline nanoneedles. When an external magnetic field was applied, this hybrid composite was attracted in one direction. Also, the luminescent phase can move simultaneously with magnetite due to a “trapping” effect. The structure and morphology of the obtained nanocomposites were examined with the use of transmission electron microscopy and X-ray powder diffraction. Spectroscopic properties of the Eu3+-doped nanomaterials were studied by measuring their excitation and emission spectra as well as their luminescence decay times.Graphical Abstract

Eu3+ and Tb3+ doped LaPO4 nanorods, modified with a luminescent organic compound, exhibiting tunable multicolour emission

Co-precipitation reaction followed by hydrothermal treatment were used to synthesise Eu3+ or Tb3+ doped LaPO4 nanorods, of 5–10 nm in width and 50–100 nm in length. Surface modification of the as-prepared nanoparticles with a selected luminescent organic compound resulted in formation of hybrid inorganic–organic nanomaterials. The products obtained exhibited tunable multicolour luminescence, dependent on the surface modification and applied excitation wavelength. The colour of their emission can be altered from red-orange to yellow-green. Powder X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) confirmed the structure and morphology of the products synthesized. Successful surface modification of the nanophosphors was evidenced by analytical and spectroscopic techniques such as dynamic light scattering (DLS) – providing size distribution histograms and zeta potentials of the nanoparticles; IR spectroscopy and elemental analysis which proved the presence of an organic phase in the structure; spectrofluorometry (excitation/emission spectra and luminescence decay curves) which confirmed the formation of hybrid, surface modified nanomaterials revealing tunable multicolour emission.

Spectroscopic, structural and in vitro cytotoxicity evaluation of luminescent, lanthanide doped core@shell nanomaterials GdVO4:Eu3+5%@SiO2@NH2

The luminescent GdVO4:Eu(3+)5%@SiO2@NH2 core@shell nanomaterials were obtained via co-precipitation method, followed by hydrolysis and co-condensation of silane derivatives: tetraethyl orthosilicate and 3-aminopropyltriethoxysilane. Their effect on human erythrocytes sedimentation and on proliferation of human lung microvascular endothelial cells was examined and discussed. The luminescent nanoparticles were synthesized in the presence of polyacrylic acid or glycerin in order to minimalize the agglomeration and excessive growth of nanostructures. Surface coating with amine functionalized silica shell improved their biocompatibility, facilitated further organic conjugation and protected the internal core. Magnetic measurements revealed an enhanced T1-relaxivity for the synthesized GdVO4:Eu(3+)5% nanostructures. Structure, morphology and average grain size of the obtained nanomaterials were determined by X-ray diffraction, transmission electron microscopy and dynamic light scattering analysis. The qualitative elemental composition of the nanomaterials was established using energy-dispersive X-ray spectroscopy. The spectroscopic characteristic of red emitting core@shell nanophosphors was completed by measuring luminescence spectra and decays. The emission spectra revealed characteristic bands of Eu(3+) ions related to the transitions (5)D0-(7)F0,1,2,3,4 and (5)D1-(7)F1. The luminescence lifetimes consisted of two components, associated with the presence of Eu(3+) ions located at the surface of the crystallites and in the bulk.

Nanosized complex fluorides based on Eu3+ doped Sr2LnF7 (Ln=La, Gd)

Abstract A simple co-precipitation approach taking place between Ln 3+ , Sr 2+ cations and F − anions, led to the formation of nanocrystalline Eu 3+ doped Sr 2 LnF 7 (Ln=La and Gd) complex fluorides. The reaction was carried out in the presence of polyethylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu 3+ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd 3+ ions to Eu 3+ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements were performed. Also FT-IR spectra of the products were recorded, revealing the presence of PEG molecules on the nanoparticles surface. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu 3+ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu 3+ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

Bifunctional luminescent and magnetic core/shell type nanostructures Fe3O4@CeF3:Tb3+/SiO2

Abstract A facile co-precipitation and microemulsion methods were applied to obtain core/shell type nanoparticles. Cerium fluoride doped with terbium(III) ions supplied intensive green luminescence of the system. Due to the presence of magnetite nanoparticles as cores, the product was highly sensitive to external magnetic field. Both sorts of nanostructures were encapsulated by silica shell. Such external layer of inert oxide can potentially increase the resistance of prepared nanostructures to thermal oxidation, aggressive agents, changing of pH or destructive radiation. Morphology of the product was examined using transmission electron microscopy (TEM). Formations of the core/shell type nanostructures were clearly seen in the TEM pictures. Powder X-ray diffraction (XRD) confirmed the structure of the products, their nanocrystallinity and amorphous nature of silica shell. Optical properties were investigated by measuring excitation and emission spectra. Such multifunctional luminescent and magnetic nanoparticles coated with easily functionalized silica shell could be applied in many field of science.

Synthesis, structural and spectroscopic studies on GdBO3:Yb3+/Tb3+@SiO2 core-shell nanostructures

Abstract The presented study concerned up-converting core/shell type nanomaterials based on lanthanide(III) ions, Ln(III), doped orthoborates. The system studied composed of the GdBO3 doped with Yb3+/Tb3+ luminescent core ensured an effective cooperative sensitization up-conversion, resulting in a bright green luminescence. The silica coating process was performed by a modified Stober method, which resulted in the formation of core-shell nanostructures, making them suitable for bioapplications. The nanophosphors and nanocomposites were obtained by various methods, such as co-precipitation in the presence of Triton X-100 and micelle synthesis with ethylenediaminetetraacetic acid (EDTA) as organic modifiers/surfactants. The synthesized nanomaterials were characterized with the use of powder X-ray diffraction (XRD), infrared light absorption with Fourier transform FT-IR spectra, transmission electron microscopy (TEM), up-conversion emission spectra under IR light, as well as excitation spectra, emission spectra and fluorescence lifetimes under UV light, and their photophysical properties were compared.

Multifunctional Optical Sensors for Nanomanometry & Nanothermometry: High-Pressure and Temperature Upconversion Luminescence of Lanthanide Doped Phosphates - LaPO4/YPO4:Yb3+-Tm3+

Upconversion luminescence of nano-sized Yb3+ and Tm3+ codoped rare earth phosphates, that is, LaPO4 and YPO4, has been investigated under high-pressure (HP, up to ∼25 GPa) and high-temperature (293-773 K) conditions. The pressure-dependent luminescence properties of the nanocrystals, that is, energy red shift of the band centroids, changes of the band ratios, shortening of upconversion lifetimes, and so forth, make the studied nanomaterials suitable for optical pressure sensing in nanomanometry. Furthermore, thanks to the large energy difference (∼1800 cm-1), the thermalized states of Tm3+ ions are spectrally well-separated, providing high-temperature resolution, required in optical nanothermometry. The temperature of the system containing such active nanomaterials can be determined on the basis of the thermally induced changes of the Tm3+ band ratio (3F2,3 → 3H6/3H4 → 3H6), observed in the emission spectra. The advantage of such upconverting optical sensors is the use of near-infrared light, which is highly penetrable for many materials. The investigated nanomanometers/nanothermometers have been successfully applied, as a proof-of-concept of a novel bimodal optical gauge, for the determination of the temperature of the heated system (473 K), which was simultaneously compressed under HP (1.5 and 5 GPa).

Nanocrystalline rare earth fluorides doped with Pr3+ ions

Abstract Praseodymium(III) doped CeF3, CeF3:Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, surfactant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subjected to a hydrothermal treatment, which led to the formation of crystalline nanoluminophores, composed of spherical (≈30 nm) and elongated (≈40–200 nm) nanostructures. Due to the presence of Pr3+ ions, the synthesized nanomaterials showed yellow luminescence under a blue light irradiation. The nanoluminophore based on the YF3 host revealed the most promising spectroscopic properties, i.e., bright and intensive emission, hence it was investigated in detail. The photophysical properties of the nanomaterials obtained were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and spectrofluorometry, i.e., measurements of excitation/emission spectra and luminescence decay curves.

Synthesis of luminescent KY3F10 nanopowder multi-doped with lanthanide ions by a co-precipitation method

Abstract A series of KY 3 F 10 nanophosphors doped with Gd 3+ , Ce 3+ and Eu 3+ ions were obtained with the use of a co-precipitation method. The resulting products were white precipitates, consisting of spherical particles with diameter about 150–200 nm, which was confirmed using transmission electron microscopy (TEM) technique. Powder X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) measurements confirmed appropriate structures of the nanoparticles obtained. Spectroscopic properties of the products were examined on the basis of the measured excitation/emission spectra and luminescence decay curves. The synthesized samples showed orange-red luminescence, characteristic for Eu 3+ ions. The reaction process was performed in required alkaline pH adjusted with the use of ethylenediaminetetraacetic acid (EDTA) and potassium hydroxide. The samples containing large amounts of Gd 3+ dopant ions exhibited a tendency to form products with different morphologies.