Temperature Conditions Of Synthesis Research Articles

Solvothermal synthesis of rhombic shape GdF<sub>3</sub>:Tb<sup>3+</sup> nanoparticles for biomedical applications

Purpose of the study. In this work, we have investigated the mechanism of structure formation of GdF3:Tb3+(15 %) nanocrystals synthesized by solvothermal synthesis in the temperature range from RT to 200 °C with a step of 50 °C.Materials and methods. Nanocrystals of GdF3:Tb3+(15 %) were synthesized by the solvothermal method using a high-pressure reactor (autoclave) designed for temperatures up to 250 °C. The structure, size and morphology were determined by transmission electron microscopy (TEM), the type of crystal lattice and the size of crystallites of nanoparticles were studied by X-ray diffraction (XRD), hydrodynamic size of nanoparticles, particle size distribution, ζ-potential, agglomeration of nanoparticles in colloidal solutions were determined by dynamic light scattering (DLS), the chemical composition of the nanocrystals surface was studied by Fourier-t ransform infra-red spectroscopy (FT-IR), the nanoparticles ability to absorb UV radiation was analyzed by UV-visible spectroscopy (UV-vis) and X-ray excited optical luminescence (XEOL).Results. With an increase in the temperature of the synthesis reaction, a structural change in the crystallites phase occurs from hexagonal to orthorhombic. At low temperatures, agglomerated particles consisting of hexagonal nanocrystals are formed, while at a temperature higher than the boiling point of the solvent, monodisperse rhombic- shaped nanoparticles with orthorhombic phase are formed. At mild temperatures, agglomerated particles with different morphology and with mixed hexagonal and orthorhombic phases are formed. Based on the analysis of X-ray spectrum, it was found that the size of GdF3:Tb3+(15 %) nanocrystals varies from 10 to 50 nm for different synthesis temperature conditions (T = RT, 50 °C, 100 °C, 150 °C, 200 °C). The hydrodynamic size of nanoparticles decreases with increasing synthesis temperature. All GdF3:Tb3+(15 %) nanocrystals obtained at different temperatures are transparent to visible light and absorb UV radiation. Absorption in the UV region increases with an increase in the size of particle crystallites. Upon X-ray irradiation of the colloidal GdF3:Tb3+(15 %) solution, X-ray excited optical luminescence spectra showed emission peaks at 490 nm, 543 nm, 585 nm and 620 nm.Conclusion. The mechanism of structure formation of rhombic‑ shaped GdF3:Tb3+(15 %) nanocrystals has been investigated. These monodisperse rhombic- shaped nanoparticles can be used for X-ray induced photodynamic therapy (X-PDT) of superficial, solid and deep-seated tumors.

Facile synthesis of a binder-free 3D Ni/NiO microwire network with a nanostructured fiber surface for a negative electrode in Li-ion battery

Binder-free Ni/NiO microwire hybrid network with a nanostructured surface is synthesized by employing a facile and low-cost method, involving one-pot synthesis of Ni microwires, followed by their partial oxidation in air atmosphere. A combination of imaging, diffraction, thermodynamic and electrochemical methods has been applied to reveal the impact of the synthesis conditions on the energy storage performance of the Ni/NiO microwire networks. The thermal conditions for the synthesis have been optimized by means of thermogravimetric (TGA/DSC) analysis, where an appropriate temperature (T = 400 °C) for obtaining a low-defect NiO phase has been determined. The performed electrochemical characterisation of the materials has shown that setting a low temperature for the synthesis enables high reversible capacity and better cycling stability of the binder-free materials. When the Ni/NiO network structures are deposited by a conventional slurry-based technology, involving polymer binder and conductive additive, the high capacity and cycling stability of the anodes are preserved, independent of the temperature conditions of synthesis. Electrochemical impedance spectroscopy is applied to support the interpretation of our results.

Effect of different synthesis temperature on the bleeding performance of polycarboxylate superplasticizer

In this paper, polycarboxylate superplasticizers were synthesized by free radical solution polymerization under different synthesis temperature conditions. The bleeding performance of polycarboxylate superplasticizers under different synthesis temperature conditions was discussed by paste test and concrete test, and the structure of polycarboxylate superplasticizers was characterized by infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The results show that the bleeding and slump retention performance of polycarboxylate superplasticizer can be effectively improved by properly increasing the synthesis temperature, and the better synthesis temperature was 55 °C. With the temperature increase, the molecular weight of polycarboxylate superplasticizers increases first and then decreases. The infrared spectra of polycarboxylate superplasticizers synthesized at different temperatures were not significantly different.

Analysis of nanomaterials based on indium and zinc oxides by high resolution continuum source atomic absorption spectrometry

The properties of nanostructured materials based on zinc and indium oxides can be modified by adding alloying elements to obtain the necessary electrical or optical properties. For example, the specificity of the chemical properties of ZnO and In 2 O 3 for the determination of toxic gases is achieved by immobilizing Au, Ag, etc. nanoparticles on their surface. Control of the material composition plays an important role in determining the dependence between the dopant content and functional properties of the materials. The study is aimed at the development of a methodical approach to the multi-element determination of catalytic dopants (Ag, Au) and matrix elements in nanostructured tin and indium oxides atomic using continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS). The matrix of the synthesized nanostructured materials (NM) is formed by the corresponding oxide with possible oxygen deficiency occurred due to the temperature conditions of synthesis (300 – 700°C), and the content of additives (Ag, Au) being varied from 1 to 3 % wt. Pyrolysis and atomization conditions for sequential multi-element atomic absorption analysis are determined. The most suitable pyrolysis temperatures upon HR CS GFAAS determinations of Ag and Au (for both In and Zn oxides), are 1000, 1600, 1200 and 900°C, respectively. The most suitable atomization temperatures for ETAA-NIS determinations of Ag, Au (for indium oxide based NM, Au (for zinc oxide based NM), In, and Zn are 1800, 2200, 2100, 2200, and 1500°C, respectively. The accuracy of analyte determination reached 1 – 4 % rel. The correctness of the results was proved by inductively coupled plasma mass spectrometry. The developed method provides control of the composition of synthesized nanostructured materials for their more efficient use in photovoltaics, as well as in production of chemical sensors for detection of harmful compounds like CO, NO 2 , NH 3 .

Investigation of disorder in carbon encapsulated core-shell Fe/Fe3C nanoparticles synthesized by one-step pyrolysis

Fe/Fe3C (core) - graphite (shell) nanoparticles embedded in micron sized amorphous carbon globules were synthesized by pyrolysis route in a closed reactor. A large number of such nanoparticles were observed to be distributed in the inner section of each globule covered by amorphous carbon in the outer regions. The distribution of nanoparticles varies according to the reaction-temperature-profile of the furnace during the synthesis process. These particles catalyze the formation of the graphitic coating on their surface, due to metastable nature of Fe3C. The globules which contain smaller catalyst particles were found to contain defective- and less amount of graphitic carbon and large amount of amorphous carbon. We observed that for low synthesis temperature conditions the globules contain a thicker shell of amorphous carbon (without any catalyst particle). Furthermore, the amount of disorder in the graphitic layer is determined by the number and size of the (Fe/Fe3C) catalyst particles and reaction-temperature. The disorder in the graphitic layer on the particles can be potentially important for the catalytic behaviour of these particles.

Thermal degradation kinetics of poly(propylene succinate) prepared with the use of natural origin monomers

Linear bio-based polyester polyols were prepared with the use of succinic acid and 1,3-propanediol (both with natural origin). Tetraisopropyl orthotitanate (TPT) was used as a catalyst. In order to determine the effect of various synthesis temperature conditions on the thermal degradation kinetics, nine sequences of temperature conditions were used during two-step polycondensation reaction. Thermogravimetric analysis was conducted with the use of DSC-TG/QMS method (differential scanning calorimetry-coupled with thermogravimetry and quadrupole mass spectrometry). The results indicated high thermal stability of the obtained materials. They undergo a one-step thermal decomposition with the temperature of maximum rate of weight loss at ca. 405 °C. Moreover, the thermal degradation kinetics was determined with the use of Ozawa, Flynn and Wall as well as Kissinger methods. The highest thermal degradation activation energy was equal to 196.4 kJ/mol.

Effect of the sodium hydrocarboaluminate preparation method on the properties of the products of its hydrolysis

Sodium hydrocarboaluminate samples are prepared using various methods. The temperature conditions of synthesis have a significant effect on the susceptibility of sodium hydrocarboaluminate to hydrolysis and the phase composition of hydrolysis products. The chemical reactivity of the hydrolysis products depends on the redox properties of their surface.

Formation of one-dimensional nanostructured WO x /W composites

The synthesis of nanowhiskers (NW) of WOx/W composites has been performed on a nickel substrate in flow of WO2(OH)2 vapor and CO and Ar gases at temperatures of 850–1000°C. Individual and bundled NWs grow in the form of nanorods at an angle to the substrate surface. Their length (5–30 µm) and diameter (100–300 nm) depend on the synthesis temperature conditions. The presence of an oxide film WOx of variable stoichiometric composition (x = 2.72–3) on the surface of tungsten NWs has been revealed using transmission and atomic force microscopy (TEM and AFM): the thickness of the oxide layer reaches 5 nm.

Facile fabrication of morphology-tunable SnOx nanostructures by catalyst-free growth

Nanorods (NRs) with square-cross-sections, sword-like NRs, and nanowires (NWs) of SnOx were synthesized by catalyst-free thermal evaporation of Sn powder in the presence of O2 gas. The effects of synthesis temperature on the morphology and photoluminescence are presented. Although it is possible that different growth mechanisms occurs simultaneously in this narrow temperature zone, predominant morphologies clearly appeared as 1-dimensional (1D) NRs, sword-like NRs, and NWs at 900°C, 925°C, and 950°C, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicate the morphological evolution of various SnOx nanostructures depending on synthesis temperature conditions. The structural properties of these SnOx have been examined by TEM, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) spectrum of the nanostructures showed two emission bands centered at approximately 440nm (blue) and 620nm (orange) originating from structural defects and surface oxygen vacancies in the case of the blue emission and grain/point defects in the case of the orange emission.

Lumino-magnetic YAG:Ce nanophosphors: novel synthesis routes for efficient luminescence and magnetic properties

Multifunctional lumino-magnetic YAG:Ce nanophosphors for LEDs and spintronics devices.

Synthesis of the lead, arsenic, and bismuth chalcogenides with liquid encapsulation

The possibility of synthesis of the lead, arsenic, and bismuth chalcogenides with liquid encapsulation has been investigated. The conditions and results of the synthesis of PbSe, PbS, PbTe, Bi2Te3, and As2Te3, as well as solid solutions in the systems PbSe-CdSe and Bi2Te3-Bi2Se3 are reported. The obtained materials have been used for fabrication of thin-film photodetectors and interference filters for infrared radiation. Recommendations concerning the choice of fluxes for liquid encapsulation and the temperature conditions of synthesis are given.

Investigation of supramolecular organization of polyetherisocyanatesiloxanes

The characteristics of the supramolecular organization of polyetherisocyanatesiloxanes are inferred from measurements of the temperature dependence of the dielectric loss tangent. It is shown that the mutual influence of macromolecular components on the formation of interpenetrating polymer network depends on the prescription and temperature conditions of synthesis.

Study of the cation distribution in the surface layer and bulk of substituted iron garnet films

A comparative analysis has been carried out of the physical-chemical state of the surface and bulk of single-crystal films of the iron garnet Y2.6Sm0.4Fe3.7Ga1.3O12 on substrates consisting of a gadolinium-gallium garnet single crystal. To carry out this study, we used the method of simultaneous γ-ray, x-ray, and electron Mosbauer spectroscopy, which made it possible to simultaneously extract information from the surface layers and the bulk of the sample. This method was applied using a precision system for the motion for the Mossbauer source. It is shown that the parameters of the hyperfine interactions in the surface layer and in the bulk of the film differ, and that these differences increase towards the surface. This result is explained by the fact that the surface layer is formed as the substrate, together with the synthesized film, is removed from the flux and, consequently, the temperature conditions of synthesis of the bulk and of the surface layer are different.