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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kirillov V. L., Balaev D. A., Semenov S. V., Shaikhutdinov K. A., Martyanov O. N.
Заглавие : Size control in the formation of magnetite nanoparticles in the presence of citrate ions
Коллективы : Siberian Branch of the Russian Academy of Sciences
Место публикации : Mater. Chem. Phys.: Elsevier Science, 2014. - Vol. 145, Is. 1-2. - P.75-81. - ISSN 0254-0584, DOI 10.1016/j.matchemphys.2014.01.036. - ISSN 1879-3312
Примечания : Cited References: 46. - This work was supported by the Interdisciplinary Integration Project no. 45 of the Siberian Branch of the Russian Academy of Sciences for 2012-2014.
Предметные рубрики: OLEIC-ACID
CATALYST
HYPERTHERMIA
PARTICLES
OXIDATION
REMOVAL
CO
Ключевые слова (''Своб.индексиров.''): magnetic materials--magnetic properties--precipitation--electron paramagnetic resonance
Аннотация: A one-pot synthesis method for the controllable growth of magnetite nanoparticles directly during the process of co-precipitation using citrate ions was developed. The effects of the concentration of citrate ions and the solution pH on the characteristics of magnetite particles with sizes in the range of 4-10 nm synthesized by the method of co-precipitation were studied. The results showed that the specified concentration of citrate ions allowed the preparation of magnetite particles with a definite size that exhibited superparamagnetic behaviour in a particular temperature range. As the concentration ratio of citrate to iron ions was increased from 0 to 0.11, the average size of the prepared magnetite particles decreased from 10.5 to 4.4 nm. As a result, the superparamagnetic blocking temperature decreased from 300 to 20 K, the saturation magnetisation decreased from 50 to 20 emu g(-1), and the average magnetic moment decreased from 8000 mu(B) to 340 mu(B) (at T = 300 K). The obtained experimental data proved that the size effects of the magnetite nanoparticles can be attributed to the capping of the magnetite surface by adsorbed citrate ions. Thus, the suggested approach allows magnetite nanoparticles to be prepared with an optimum particle size around superparamagnetic threshold that prevents their irreversible agglomeration and simultaneously allows them to be removed from a solution at an acceptable rate. (C) 2014 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ji H., Huang Z., Xia Z., Xie Y, Molokeev M. S., Atuchin V. V.
Заглавие : Facile solution-precipitation assisted synthesis and luminescence property of greenish-yellow emitting Ca6Ba(PO4)4O:Eu2+ phosphor
Место публикации : Mater. Res. Bull.: Elsevier, 2016. - Vol. 75. - P.233-238. - ISSN 00255408 (ISSN), DOI 10.1016/j.materresbull.2015.11.055
Примечания : Cited References: 22. - This work was partly supported by the National Natural Science Foundations of China (grant nos. 51272242, 51472222, 51511130035), the Research Fund for the Doctoral Program of Higher Education of China (grant no. 20130022110006), and the Russian Foundation for Basic Research (grant no. 15-52-53080 GFEN_a). VVA was partly supported by the Ministry of Education and Science of the Russian Federation
Предметные рубрики: SOLID-SOLUTION PHOSPHORS
PHOTOLUMINESCENCE PROPERTIES
VIBRATIONAL PROPERTIES
ENERGY-TRANSFER
DIODES
Ключевые слова (''Своб.индексиров.''): optical materials--luminescence--optical properties--crystal structure--phosphors
Аннотация: Greenish-yellow emitting microcrystalline Ca6Ba(PO4)4O:Eu2+ phosphor was successfully prepared by a solution-precipitation assisted high temperature reaction method. Phase structure, morphology and/or luminescence properties of the precursor and the as-prepared phosphors were characterized. The phase-pure Ca6Ba(PO4)4O:Eu2+ phosphors were obtained with smooth grain surface and particle size of 2–8 μm. Ca6Ba(PO4)4O:Eu2+ exhibits bright greenish-yellow color emission with its maximum at 540 nm upon UV-blue light excitation. The maximum position of the broad emission band is independent on the calcination temperature. The emission intensity increases with increasing calcination temperature due to improved crystallinity. Besides, the presence of two Eu2+ emission centers in the Ca6Ba(PO4)4O crystal lattice was confirmed and the coordination effects are considered concerning the roles of isolated O atoms and those from the PO4 tetrahedra.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Martyanov O. N.
Заглавие : Probing flocculant-induced asphaltene precipitation via NMR imaging: from model toluene-asphaltene systems to natural crude oils
Коллективы : Russian Science Foundation [15-19-00119]
Место публикации : Appl. Magn. Reson.: Springer, 2016. - Vol. 47, Is. 2. - P.223-235. - ISSN 0937-9347, DOI 10.1007/s00723-015-0741-9. - ISSN 1613-7507(eISSN)
Примечания : Cited References:46. - This research was performed with the financial support of Russian Science Foundation (project no. 15-19-00119).
Предметные рубрики: PETROLEUM ASPHALTENES
MOLECULAR-DYNAMICS
AGGREGATION
MICROSCOPY
SCATTERING
RESONANCE
SEDIMENTATION
ASSOCIATION
CALORIMETRY
RELAXATION
Аннотация: An nuclear magnetic resonance (NMR) imaging approach for studying flocculant-induced asphaltene precipitation processes is introduced in this report. Unlike commonly accepted techniques, which primarily measure aggregation processes on the submicron scale (the level of asphaltene molecules and their aggregates), NMR imaging demonstrates the capability to obtain new useful information about bulk system behavior on the macro scale. To reveal the capabilities of the method, the model toluene-asphaltene system and two samples of natural crude oils with different chemical composition and physical properties (such as asphaltene content and density) were employed for experiments. The process of colloidal suspension formation and two different patterns of its evolution were observed depending on both the asphaltene content and the flocculant concentration. In the first pattern, the flocculant-induced precipitation leads to the slow uniform compacting of the suspension and descent of the sedimentation front, whereas the second pattern is characterized by sediment accumulation and the upwards drift of the front. It was found that the behavior of the precipitated asphaltenes in the model system correlates well with those observed in natural crude oils. The results achieved in this work are in agreement with the data obtained previously via other techniques. Thus, NMR imaging proved to be an efficient method for probing flocculant-induced precipitation in crude oils.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ji H., Wang L., Cho Y., Hirosaki N., Molokeev M. S., Xia Z., Huang Z., Xie R.-J.
Заглавие : New Y2BaAl4SiO12:Ce3+ yellow microcrystal-glass powder phosphor with high thermal emission stability
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2016. - Vol. 4, Is. 41. - P.9872-9878. - ISSN 20507534 (ISSN), DOI 10.1039/c6tc03422e
Примечания : Cited References: 32. - This study was partially supported by the National Natural Science Foundation of China (Grant No. 51272259, 51572232 and 51561135015). R. X. was also partially supported by the JSPS KAKENHI (No. 15K06448). M. M. and Z. X. were also partially supported by the Russian Foundation for Basic Research (No. 15-52-53080). H. J. thanks the China Scholarship Council (CSC) for scholarship support.
Ключевые слова (''Своб.индексиров.''): aluminum--crystal structure--crystallization--glass--laser applications--light emission--microcrystals--phosphors--precipitation (chemical)--quenching--silicon--silicon oxides--single crystals--structural design--crystalline nature--crystallization behavior--emission intensity--microcrystal glass--morphology structures--phase formation behavior--structure analysis--temperature increase--cerium
Аннотация: To decrease the rare earth element usage and synthesis cost of Y3Al5O12:Ce phosphor, the Y2BaAl4SiO12 compound is developed as a new host for Ce3+ employing the solid solution design strategy. The design uses polyhedron substitution where YO8/AlO4 are partially replaced by BaO8/SiO4, respectively. Structure analysis of Y2BaAl4SiO12 proves that it successfully preserves the garnet structure, crystallizing in the cubic Iad space group with a = b = c = 12.00680(5) Å. Barium (Ba) atoms occupy the Y site and silicon (Si) atoms occupy the Al site in the AlO4 tetrahedrons. An expanded study on Y2MAl4SiO12 (M = Ba, Ca, Mg, Sr) series shows a cation size (of M)-dependent phase formation behavior. The lattice stability can be related with the M type in the M–Si pair and substitution level of M–Si for Y–Al. Doping Ce3+ into Y2BaAl4SiO12 yields bright yellow photoluminescence peaking at around 537 nm upon excitation by 460 nm light. The emission intensity is quite stable against thermal quenching whereas the peak wavelength shows a slight red-shift as the ambient temperature increases. The crystallization behavior of Y2BaAl4SiO12 is suggested as melt-assisted precipitation/growth based on cathodoluminescence analysis. The highly crystalline nature of the microcrystals explains the stable emission against thermal quenching. This study may provide an inspiring insight into preparing phosphor with new morphology-structure of “microcrystal-glass powder phosphor”, which distinguishes it from conventional “ceramic powder phosphor” or “single-crystal phosphor”.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Falaleev O. V., Martyanov O. N.
Заглавие : New insight into the wax precipitation process: in situ NMR imaging study in a cold finger cell
Место публикации : Energy Fuels: American Chemical Society, 2016. - Vol. 30, Is. 11. - P.9003-9013. - ISSN 08870624 (ISSN), DOI 10.1021/acs.energyfuels.6b01535
Примечания : Cited References: 69. - This research was performed with the financial support of the Russian Science Foundation (Project No. 15-19-00119).
Ключевые слова (''Своб.индексиров.''): cells--crude oil--cytology--deposits--diffusion--gelation--magnetic resonance imaging--ostwald ripening--phase separation--polymer blends--deposit formation--deposit structures--diffusion controlled growth--dominant mechanism--lower temperatures--morphology and dynamics--phase-separation process--temperature regimes--image processing
Аннотация: A cold finger cell intended for the wax deposition measurements was fabricated and integrated into an NMR imaging probe for the noninvasive study of wax precipitation processes in situ. The cell was first tested with a model system; then, a series of experiments with different thermal gradients applied to the cell were performed for a waxy crude oil. NMR imaging of the operating cell revealed the formation of a deposit with the morphology and dynamics strongly correlating with the temperature regime. At higher temperatures of cold finger, the incipient wax gel ages uniformly, giving rise to the hard and thin inner layer of deposit accompanied by a branched loosely consolidated outer layer. Conversely, the lower temperatures facilitate formation of a thick deposit which no longer ages uniformly and slow down the diffusion-controlled growth of the branched deposit structure. The results obtained are consistent with the majority of the data previously reported. Thus, gelation of the wax at temperatures below the cloud point and subsequent thermal-driven diffusion processes are considered to be the dominant mechanisms of the deposit formation. The counter diffusion and Ostwald ripening aging concepts were found to be relevant in the case of the cold finger study and account for the phenomena observed in this work. The information obtained via NMR imaging is highly complementary to the results obtained by other techniques that can aid in understanding the essential processes behind the wax precipitation phenomena. The approach developed can be effectively extended to study any thermal-driven phase separation process. © 2016 American Chemical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivantsov R. D., Evsevskaya N., Saikova S., Linok E., Yurkin G. Yu., Edelman I. S.
Заглавие : Synthesis and characterization of Dy3Fe5O12 nanoparticles fabricated with the anion resin exchange precipitation method
Место публикации : Mater. Sci. Eng. B: Elsevier, 2017. - Vol. 226. - P.171-176. - ISSN 09215107 (ISSN), DOI 10.1016/j.mseb.2017.09.016
Примечания : Cited References: 49. - The work was supported partly by the Grant of the President of the Russian Federation – Russia no. NSh-7559.2016.2, and by the Russian Foundation for Basic Research – Russia (RFBR): grant. No. 16-33-00043.
Ключевые слова (''Своб.индексиров.''): dy3fe5o12 nanoparticles--anion resin exchange precipitation method--magnetic circular dichroism
Аннотация: Dysprosium-iron garnet (DyIG) nanoparticles were synthesized with the new modification of the anion resin exchange precipitation method. Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy showed nanoparticles to be of the garnet structure with an excellent crystallinity. Magnetic properties were studied by using QUANTUM Design MPMS-XL system and the visible magnetic circular dichroism (MCD). Nanoparticles magnetic properties were close to those of bulk DyIG crystals. Dependence of the nanoparticles magnetization (M) on the external magnetic field (H) is described by a narrow hysteresis loop in relatively low fields and the strong linear M increase with the further H increase. The visible MCD of DyIG was studied in this work for the first time. The MCD spectra consisted of several peaks associated with electron transitions in iron and dysprosium ions located in different spectral intervals. Dependences of the MCD peak intensities on temperature and magnetic field were studied.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Martyanov O. N.
Заглавие : Reversibility of asphaltene aggregation as revealed by magnetic resonance imaging in situ
Место публикации : Energy Fuels: American Chemical Society, 2017. - Vol. 31, Is. 10. - P.10639-10647. - ISSN 08870624 (ISSN), DOI 10.1021/acs.energyfuels.7b01755
Примечания : Cited References: 56. - This research was performed on the equipment of Krasnoyarsk Regional Research Equipment Centre of Siberian Branch of Russian Academy of Sciences with the financial support of Russian Science Foundation (Project No. 15-19-00119).
Ключевые слова (''Своб.индексиров.''): aggregates--crude oil--flocculation--heavy oil production--magnetic resonance imaging--asphaltene aggregates--asphaltene aggregation--asphaltene precipitation--equilibrium compositions--flocculant concentrations--inhomogeneous distribution--mechanical stirring--multi-component systems--asphaltenes
Аннотация: Aggregation of asphaltenes followed by precipitation presents severe problems for existing technologies in the production, recovery, and processing of heavy oils. Better understanding of asphaltene behavior behind the processes of their precipitation and dissolution is vital to address this issue. While investigating the inhomogeneity of different oil systems, the reversibility of the asphaltene aggregation process initiated by flocculant in either asphaltene solution in toluene or crude heavy oil was revealed and investigated using magnetic resonance imaging methods. It was found that the inhomogeneous distribution of the flocculant initiates local spatial-selective asphaltene aggregation registered in a thin layer around the flocculant/oil sample interface. The local excess of flocculant concentration over the threshold of asphaltene precipitation onset is a driving force of this process. As the flocculant diffuses into the volume of the sample, a decrease of the asphaltene flocculated area is observed until it disappears when the equilibrium composition throughout the whole volume of the system is achieved. Depending on the overall flocculant concentration, the asphaltene aggregation may not be reversible and could be followed by subsequent precipitation of the asphaltene aggregates. The similarity of the phenomena observed for the model asphaltene solutions and crude heavy oil samples was established. Partial mechanical stirring of the multicomponent system comprising flocculant and oil or asphaltene solution does not prevent the formation of the local zones with increased concentration of asphaltene aggregates; those sizes evolve depending on the flocculant concentration. The results obtained in this work are consistent with the generally accepted concept of asphaltene precipitation reversibility depending on the system composition and are compatible with the observations obtained by other methods. The approach presented can provide deeper insight into the asphaltene precipitation reversibility issue and can facilitate the understanding of asphaltene behavior in heavy oils.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Jiang C., Brik M. G., Li L., Li L., Peng J., Wu J., Molokeev M. S., Wong K. -L., Peng M.
Заглавие : The electronic and optical properties of a narrow-band red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 12. - P.3016-3025. - ISSN 20507534 (ISSN), DOI 10.1039/c7tc05098d
Примечания : Cited References: 55. - We acknowledge the financial support received from the Program for Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_17R38), the Key Program of Guangzhou Scientific Research Special Project (Grant No. 201607020009), the National Natural Science Foundation of China (Grant No. 51672085, 51322208, 3160440), and the Fundamental Research Funds for the Central Universities. M. G. Brik acknowledges the supports received from the Recruitment Program of High-end Foreign Experts (Grant No. GDW20145200225), the Programme for the Foreign Experts offered by Chongqing University of Posts and Telecommunications, Ministry of Education and Research of Estonia, (Project PUT430) and European Regional Development Fund (Project TK141), and the Guest Professorship at Kyoto University (Prof. S. Tanabe laboratory). The first-principles calculations were carried out using the resources provided by the Wroclaw centre for Networking and Supercomputing (http://wcss.pl; Grant No. WCSS#10117290).
Ключевые слова (''Своб.индексиров.''): energy efficiency--gallium compounds--light emission--light emitting diodes--manganese--manganese compounds--optical properties--phosphors--precipitation (chemical)--quenching--rietveld refinement--sodium compounds
Аннотация: Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150-250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fm3m with the cell parameter a = 8.25320(4) Å. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti-Hirayama model, suggesting that the dipole-dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the red component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the red phosphor used in warm WLEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Evsevskaya N., Pikurova E., Saikova S. V., Nemtsev I. V.
Заглавие : Effect of the deposition conditions on the anion resin exchange precipitation of indium(III) hydroxide
Место публикации : ACS Omega. - 2020. - Vol. 5, Is. 9. - P.4542-4547. - ISSN 24701343 (ISSN), DOI 10.1021/acsomega.9b03877
Примечания : Cited References: 33. - This work was supported by the Deanship of Research at Jordan University of Science and Technology under grant number (213/2016)
Аннотация: A new patented method for the synthesis of nanosized powders of indium(III) hydroxide and oxide using the strong base anion exchange resin AV-17-8 as a precipitate agent was proposed. The effect of anions of the initial indium salt and the influence of the process duration, temperature, and counterions of resin such as hydroxide or carbonate on the yield of indium(III) hydroxide during the anion resin exchange precipitation were investigated by scanning electron microscopy, electrical conductivity measurement method, and atomic absorption analysis. Based on the obtained data, the mechanism of the anion resin exchange precipitation of indium(III) hydroxide was suggested. The products were characterized by X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, elemental analysis, Brunauer-Emmett-Teller, and transmission electron microscopy. It was found that impurity-free monophasic In2O3 powders with an average particle size of 10-15 nm and specific surface area of 62-73 m2/g were formed after heat treatment of as-prepared products at 400 °C.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Saikova S., Pavlikov A., Trofimova T., Mikhlin Y., Karpov D., Asanova A., Grigoriev Y., Volochaev M. N., Samoilo A., Zharkov S. M., Velikanov D. A.
Заглавие : Hybrid nanoparticles based on cobalt ferrite and gold: Preparation and characterization
Место публикации : Metals. - 2021. - Vol. 11, Is. 5. - Ст.705. - ISSN 20754701 (ISSN), DOI 10.3390/met11050705
Примечания : Cited References: 74
Аннотация: During the past few decades, hybrid nanoparticles (HNPs) based on a magnetic material and gold have attracted interest for applications in catalysis, diagnostics and nanomedicine. In this paper, magnetic CoFe2O4/Au HNPs with an average particle size of 20 nm, decorated with 2 nm gold clusters, were prepared using methionine as a reducer and an anchor between CoFe2O4 and gold. The methionine was used to grow the Au clusters to a solid gold shell (up to 10 gold deposition cycles). The obtained nanoparticles (NPs) were studied by X-Ray diffraction (XRD), transmis-sion electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, X-Ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy techniques. The TEM images of the obtained HNPs showed that the surface of cobalt ferrite was covered with gold nanoclusters, the size of which slightly increased with an increase in the number of gold deposition cycles (from 2.12 ± 0.15 nm after 1 cycle to 2.46 ± 0.13 nm after 10 cycles). The density of the Au clusters on the cobalt ferrite surface insignificantly decreased during repeated stages of gold deposition: 21.4 ± 2.7 Au NPs/CoFe2O4 NP after 1 cycle, 19.0 ± 1.2 after 6 cycles and 18.0 ± 1.4 after 10 cycles. The magnetic measurements showed that the obtained HNPs possessed typical ferrimagnetic behavior, which corresponds to that of CoFe2O4 nanoparticles. The toxicity evaluation of the synthesized HNPs on Chlorella vulgaris indicated that they can be applied to biomedical applications such as magnetic hyperthermia, photothermal therapy, drug delivery, bioimaging and biosensing.
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