CC BY
9
-□ □-
Методами фотометри та електро-нног мжроскотг визначен функцп роз-подту частинок магнетиту, стабШзо-ваних поверхнево-активною речовиною, за розмiрами, i гх комплексний показник заломлення. За допомогою вимiрювання коефщента пропускання виконаний ана-лiз процесу седиментацп наночастинок в лШдо-магнетитових суспензiях рiзного складу i концентраци. За тимчасовим залежностям коефщента пропускання розрахований ефективний середнш рад^ ус наночастинок. Щ частинки синтезо-ваш як компонент бiологiчно-активних та харчових добавок
Ключевi слова: магнетит, фотоме-трiя, електронна мшроскотя, розмiр частинок, сттк1сть, лШдо-магнетито-
ва суспензiя
□-□
Методами фотометрии и электронной микроскопии определены функции распределения частиц магнетита, стабилизированных поверхностно-активным веществом, по размерам, и их комплексный показатель преломления. С помощью измерения коэффициента пропускания выполнен анализ процесса седиментации наночастиц в липидо-магнетитовых суспензиях различного состава и концентрации. По временным зависимостям коэффициента пропускания рассчитан эффективный средний радиус наночастиц. Эти частицы синтезированы как компонент биологиче-ски-активнъж и пищевых добавок
Ключевые слова: магнетит, фотометрия, электронная микроскопия, размер частиц, устойчивость, липидо-магнети-
товая суспензия -□ □-
UDC 539.215.2:535.203.4
|DOI: 10.15587/1729-4061.2016.76105
THE STUDY OF NANOPARTICLES OF MAGNITITE OF THE LIPID-MAGNETITE SUSPENSIONS BY METHODS OF PHOTOMETRY AND ELECTRONIC MICROSCOPY
A. Alexandrov
Candidate of Chemistry Sciences, Associate Professor, Head of Department* E-mail: alexandrov_a_v@inbox.ru I. Tsykhanovska Candidate of Chemistry Sciences, Associate Professor* E-mail: cikhanovskaja@rambler.ru T. G o n t a r Senior Lecturer* E-mail: taty-gontar@mail.ru N. Kokodiy Doctor of Technical Sciences, Professor Department of Theoretical Physics Natsionalny Pharmaceutical University Pushkinskaya str., 53, Kharkiv, Ukraine, 61002 E-mail: kokodiy.n.g@gmail.com N. Dotsenko PhD, Assistant
Department of mechanization and electrification of
agricultural production Mykolayiv State Agrarian University Paris Commune str., 9, Nikolaev, Ukraine, 54010 Е-mail: gorbenkonatalija@rambler.ru *Department of Food and Chemical Technology Ukrainian Engineering-Pedagogical Academy Universitetskaya str., 16, Kharkiv, Ukraine, 61003
1. Introduction
At present, an important task facing food industry is expanding the range of products with improved nutritional value and long-term shelf life as well as saving scarce raw materials [1].
For normal functioning, a human organism must receive nutrients and energy in the amount adequate to the consumption. Lately, a lot of attention in nutrition is paid to lipids (animal fats and oils) - products with high nutritious and energy indices.
Nutritional properties (quality) of lipids are essentially influenced by their chemical transformations under the influence of temperature, water and other ingredients [2].
The presence of products of chemical and thermal transformations in lipids (fats, oils) significantly decreases their nutritional, energy and organoleptic indices and complicates their technological processing and assimilation [3, 4].
So, solution of the problem of chemical transformations (mostly oxidation) of lipids is very important - because these products are responsible for spoiling and reducing the shelf life of fats, oils and fat-containing food products and for decrease in their nutritional value and physiological safety [2-5].
Magnetite - double oxide of two- and trivalent iron (Fe0-Fe203) was studied as the antioxidant [6].
Given the positive influence of magnetite itself on a human organism [7] and the use of Fe304 as a source of assimilated iron [8], it is possible to use it in foods with the purpose
©
of enriching the body with Fe (II) and creation of the antianemic group of products (for treatment and prevention).
The entire set of the received data allows recommending Fe304 as a food supplement of the comprehensive action in lipid-magnetite suspensions (LMS), in which lipids form the dispersion medium (oils, melted animal fats, fat and oil composition) [4-6, 9].
Therefore, creation of the LMS which are stable in time, analysis of the process of their sedimentation, determining the size of the stabilized particles of magnetite Fe304, the functions of distribution by the size and their comprehensive index of refraction is a relevant and important task.
2. Literature review and problem statement
Because many of physical and chemical properties of nanoparticles, unlike voluminous materials, greatly depend on their size, the interest in the methods of measuring the nanoparticles dimensions in suspensions (solutions) has been considerably increasing lately; as a consequence, it is necessary to develop a set of methods of analysis for the measurement of parameters of nanoparticles.
In addition, to improve the quality indices of the products made of various materials (alloys, graphite products, plastics, pharmaceuticals, cosmetic products, food products, etc.) in the process of their obtaining, the use of nanopowders is becoming wider now. So, one of the promising directions of modern science is the development of nanotechnologies -the set of methods of obtaining and using nanoparticles [10].
Nanomaterials are divided into "nanostructured" materials and nanodispersions (nanosuspensions). Nanodisper-sions consist of dispersion medium (vacuum, gas, liquid or a solid body), in which nanoparticles, isolated from one another, are distributed [11]. The linear sizes of nanoparticles (from 1 to 100 nm) have one order of magnitude; normally, nanoparticles have the spheroid form. By virtue of their unique properties (for example, magnetic, bacteriostatic, germicidal, such as in magnetite) and their size, nanoparti-cles require careful studying. There are more than 20 ways of obtaining nanoparticles [11] and they can be conditionally divided into four groups:
- molecular clusters are obtained by chemical reactions in a solution or in gas phase;
- gas-phase clusters are obtained by condensation in the gas phase through initial vaporization;
- solid clusters appear as a result of solid-state chemical reactions or implanting ions;
- colloidal clusters are obtained by nucleation from solutions and melts or through the sol-gel transformations.
The processes, as a result of which nanostructures are formed, include crystallization, re-crystallization, phase transformations, high mechanical loads and intensive plastic deformation, full or partial crystallization of amorphous structures [10, 11]. The characteristics of the obtained product - granu-lometric composition and the shape of particles, the content of impurities and the magnitude of specific surface can vary in a fairly wide range depending on the method of obtaining.
The industries of different countries use a variety of nanoparticles of different chemical composition, but their application does not always yield desirable results, which is mostly due to the unawareness of their true size, defining which is a fairly complicated problem. So, for example, the use of the same nanoparticles that are different in size (be-
cause of various production technologies or application of different methods of defining their size), leads to obtaining finished products with different properties.
Next, we will list the most common methods of defining the size of nanoparticles [10-28]:
- electronic microscopy (based on the analysis of the sample using a beam of accelerated electrons) [10-16];
- transilluminating electronic microscopy (transillumination of the sample with a beam of electrons with determining the size and internal structure of the particles) [10, 11];
- scanning (raster) electronic microscopy (scanning the sample surface with a beam of electrons with simultaneous registration of secondary electrons and obtaining a 3-D image) [10, 12];
- scanning probe microscopy (analysis of relief of the sample surface with the use of a probe) [10, 13];
- scanning tunnel microscopy (analysis of relief of the current-conducting surfaces by registering the magnitude of tunnel current that occurs between the tip of the probe and the surface of the sample) [10, 14];
- atomic-power microscopy (analysis of relief and mechanical properties of the surfaces by registering the magnitude of van der Waals forces occurring between the tip of the probe and the surface of the sample) [10, 15];
- light scattering (the method of statistical dispersion of light) (determining the size of the particles by the intensity of scattered light) [10, 16];
- photon correlation (the method of dynamic dispersion of light) (determining the size of the particles by the coefficient of diffusion that is defined by the intensity and frequency characteristics of scattered light) [10, 16];
- small-angular scattering (X-rays and neutrons) (assessment of the size of the particles by the angular dependence of intensity of diffuse scattering (in the field of small angles)) [10, 17];
- diffraction methods (X-ray diffractometry - electronic - neurography) (diffraction of radiation on the crystal lattice of the sample with obtaining diffractogram and estimation of the size of crystals by the magnitude of expansion of diffraction maxima) [10-18];
- sedimentation (determining the size of the particles by the rate of their sedimentation); adsorption method (BET - theory of Brunauer, Emmet and Teller) (determining the specific surface (the size of the particles) of the sample by measuring the magnitude of the low-temperature adsorption of inert gases (nitrogen)) [10, 18].
The researchers measured the size of the particles of iron by various methods. Table 1 shows to what extent the obtained results may vary [10].
Таble 1
Results of determining the size of Fe particles, obtained by different methods
Method of analysis Size of particles, nm
Scanning electronic microscopy 50-80
Transilluminating electronic microscopy 300-1000
X-ray diffractometry 20
Small-angular diffraction: neurography 24-64
Low-temperature adsorption (BET) 60
Static light scattering 50-8000
Dynamic light scattering 70
The generally accepted way of determining the size of nanoparticles is their studying using transilluminating electronic microscopes. But, for example, titanium nitride, TiN, produced by NaBond Technologies Co, Ltd, HONG KONG [12], is impossible to categorize based on its results, although the size of its particles does not exceed 100 nm. Besides, the nanoparticles are prone to formation of conglomerates. These data are presented in the works [13, 14]. A comprehensive idea of the disparsity of powder is given by knowing the totality of such characteristics as the size of the particles, their total specific surface and morphology. There are many methods of determining the size of the particles, which use different physical principles such as laser diffraction of light stream on the particles, sedimentation of the particles by weight in dispersion medium.
A significant contribution to studying the size, geometry and morphology of particles is made by the method of determining their specific surface as well as scanning electronic microscopy [10, 15, 16]. In this case, though not always equal by the principles of research, the methods give similar results, which was shown in the paper [15] when assessing the ultra-thin tungsten powder by the methods mentioned above.
The difficulty of determining the size of the powder particles lies in the fact that they are prone to agglomeration [10, 15].
Other methods for determining the size of the nanopow-der particles are also used, but, as their analysis showed, none of them gives the exact size of nanoparticles [10]. So, in the papers [17], the kinetics of sedimentation processes and the stability of suspensions with supermagnetic nanoparticles of ferrum oxide were analyzed by the methods of sedimentation and nuclear magnetic resonance (NMR). The disadvantage of this method is inaccuracy (in case of sedimentation) and the use of expensive equipment (NMR). Lack of accuracy is observed in determining the stability of magnetite suspension in the complex method (viscosimetry+sedimentation) [18]. In the fluorescent method, there are some restrictions due to the limited capabilities of standard fluorescent devices. The disadvantage of the laser methods [19] is dependence of the measurement results on the condition of the surface of the particles in suspension. The differential capacity of the system differential motion analyzer (DMA) [20, 21] and the accuracy of measurement vary depending on temperature and pressure. The disadvantages of the optical method of "measuring indicatrix of the scattered particles of light" [22-24] are the complexity of measurement of the form of indicatrix of scattering and the necessity to know the refraction index. Besides, the method cannot be applied to measure the size of the nanoparticles because the width of the first petal of indicatrix becomes very large, larger than 90°, and the accuracy of measurement is significantly reduced. The disadvantages of the method of "dynamic scattering of light" [25] is the complexity of experimental equipment that should give the possibility to measure very small intensities of scattered light and the inability to measure the size of the microparticles. In the article [26], the methods of spectro-photometry and scanning electronic microscopy were proposed for studying the extaction and morphological characteristics of magnetite particles in aqueous suspensions. The disadvantage is the fact that these methods are unacceptable for lipid suspensions. In the optic method of determining the concentration and size of the particles of magnetite by using the fluctuations of transparency, the research is based on the hydrogen suspensions of magnetite, which is why it is
not suitable for lipid-magnetite suspensions [27]. With the spectrophotometric [28] method, it is difficult to process the data, although the method has high accuracy.
That is why, researchers of the sizes and morphological characteristics of nanoparticles who have been working with ultra-thin particles for years, state "for an objective evaluation of the properties and the morphology of nanopowders, development of the set of methods of analysis is necessary".
Besides, in the literary sources [10-28] we have not found any facts of using the methods of photometry and electronic microscopy for studying morphological characteristics and optical properties of magnetite nanoparticles in LMS, based on the processing attenuation spectrum and e-microphotography of Fe3O4 nanoparticles (histogram): of the sizes, of the functions of distribution of Fe3O4 particles by size and of their comprehensive index of refraction.
Therefore, using the methods of photometry and electronic microscopy, the process of sedimentation of LMS of different composition and concentrations was studied; the sizes of the stabilized particles of magnetite Fe3O4, the functions of distribution by size and their comprehensive index of refraction were defined.
3. The aim and the tasks of the study
The aim of the work is to study the process of sedimentation of lipid-magnetite suspensions of different composition and concentration by the methods of photometry and electronic microscopy, to determine the size of the stabilized particles of magnetite Fe3O4, the functions of distribution by size and their comprehensive index of refraction.
To achieve the goal, the following tasks were set:
- analysis of dependence of the light transmission factor by lipid-magnetite suspension (LMS) on the wavelength and the time of exposure of the LMS at different wavelengths of light and assessment of the suspension stability over time;
- determining the size of the magnetite particles, stabilized by the surface active substance (monoacylglycerol), using the methods of electronic microscopy and photometry as well as distribution of particles by size f(r), their indices of refraction (n) and absorption (k), the concentration N; analysis of changes in the concentration of magnetite particles in the LMS in time;
- determining and analysis of the spectra of transmission of the diluted LMS of different composition and concentration;
- determining the kinetic dependency of the transmission factor for the suspensions with different concentration of magnetite and the mean effective radius of the particles.
4. Materials and methods of studying sedimentation resistance of lipid-magnetite suspensions
4. 1. Studied substances and equipment used in the experiment
While obtaining the suspensions, ultra-thin magnetite (with the particle size of 30-60 nm) was used, which was synthesized according to the well-known method of co-sedimentation of salts of two- and trivalent ferrum in alkaline medium [29].
In the study we used the sunflower refined deodorized oil in accordance with DSTU 4492:2005; non-refined corn
oil DSTU GOST 8808-2003 "Corn oil. Technical specifications (GOST 8808-2000. IDT)"; non-refined soybean oil DSTU 4534:2006 "Soybean oil. Technical conditions"; pork fat in accordance with GOST 25292-82; beef fat GOST 1288-41; salomas unrefined for margarine industry TU 9145-181-00334534-96, TU 15.4-13304871-005:2005; substitute of milk fat "Violia-milk fat 3" TU15.4-13304871-005:2005, GOST P 53796-2010; confectionery fat «Shortening» TU U-15.4-00373758:022-2006; PAR (monoacyl-glycerol) Dimodan HP.
In Fig. 1, the following lipids are presented: oils (soybean, corn, sunflower); salomas, beef, pork and confectionery fats "Violia-milk fat 3" and "Shortening".
Table 1
Results of measurement of the transmission factor (T, %) depending on the wavelength of light (X, nm) over time for the soy-magnetite suspension
Transmission factor T, % AT, %
X, nm Exposure time of suspension t, hours
0 0,5 1,0 24,0 48,0
210 25 25,6 26,3 26,9 27,5 10,0
250 23 24,1 25,2 26,7 27,2 18,3
300 26 26,5 27,3 28,5 29,9 15,0
350 28,2 29,7 31,4 32,9 34,4 21,9
400 29 30,6 31,9 33,8 35,7 23,1
450 33,1 34,4 35,7 37,3 39,5 19,3
500 31,5 33,8 34,5 35,6 38 20,6
550 30,5 32,6 33,3 34,5 36,8 20,6
600 48,6 50,7 52,8 58,2 63,5 30,7
650 54,6 55,8 58,4 63,5 68,7 25,8
700 57,8 59,6 62,5 66,7 71,3 23,4
750 58,5 60,3 64,6 68,3 72 23,1
800 61,2 62,9 66,5 70,3 74,6 21,9
850 64,5 66,2 68,6 72,5 76,1 18,0
900 69,6 70,9 73,4 76,3 80 14,9
950 71,6 72,3 73,9 76,9 80,9 13,0
1000 71,9 72,5 73,7 77 81, 2 12,9
Fig. 1. The studied lipids
Lipid-magnetite suspensions (LMS) were received by the technology [7]. The LMS with magnetite, obtained by this way, as a dispersion phase, have vegetable or animal fats as dispersion medium.
The study of stability and concentration of the suspensions, morphological features of the particles was carried out using spectrophotometry (spectrometer Specol 11) or PE-5400 UV (TOV "Ecochim") and eletronic microscopy (transmission electronic microscope (TEM) JSM-820 (JEOL).
4. 2. Methods of determining stability, disper-sity of lipid-magnetite suspensions of different composition, concentration, as well as the sizes, functions of distribution of Fe3O4 particles by size and their comprehensive index of refraction
The method is based on the analysis of attenuation spectrum of suspension with the nanoparticles. It is possible to get acquainted with the method of determining the stability, dispersity of lipid-mag-netite suspensions of different composition, concentration, as well as the size, function of distribution of Fe3O4 particles by size and their comprehensive index of refraction in the paper [30-35].
5. Results of studying sedimentation and aggregation stability of morphological characteristics of LMS
The results of measurement of the transmission factor (T, %) depending on the wavelength of light (X, nm) over time (the ratio Fe3O4:SAS= =0,05:0,70 mass %; the concentration of suspension 29,25 mg/l) are shown in Table 1 and in Fig. 2, 3.
e
o
'S 30
Si £
210 400 600 800 950 650
15 20 25 30 35 40
Exposure time of suspension t, year.
Fig. 2. Dependence of the transmission factor (T, %) on the wavelength of light X (nm) over time for the soy-magnetite suspension (SMS)
e
«
£
-0
0,5 -1 24 48
500 600 700
Wavelength, X, nm
Fig. 3. Dependence of the transmission factor (T, %) on exposure time of the soy-magnetite suspension (t, hours) at the different wavelengths of light (X - from 210 to 1000 nm)
90
80
70
60
o50
20
10
0
0
5
10
45
50
90
80
70
60
50
n 40
30
20
10
0
200
300
400
800
900
1000
A typical view of experimental dependence a(A) for the soy-magnetite suspension is presented in Table 2 and in Fig. 4. In this case, ai and A were determined by formulas (11), (12) n0=1,48 - index of refraction of dispersion medium (soybean oil), determined experimentally.
Table 2
Results of calculation of Ai and ai of the suspension
io(nm) - Ti (%); Ti (u. sh.) Ai, ^m ln Ti ai, m 1
210 - 25,0; 0,25 0,142 1,65 165
250 - 23,0; 0,23 0,169 1,47 147
300 - 26,0; 0,26 0,203 1,31 131
350 - 28,2; 0,282 0,236 1,18 118
400 - 29,0; 0,29 0,27 1,045 104,5
450 - 33,1; 0,331 0,304 0,93 93
500 - 31,5; 0,315 0,34 0,82 82
550 - 30,5; 0,305 0,374 0,72 72
600 - 48,6; 0,486 0,408 0,66 66
650 - 54,6: 0,546 0,142 0,61 61
700 - 57,8; 0,578 0,169 0,57 57
750 - 58,5; 0,585 0,203 0,536 53,6
800 - 61,2; 0,612 0,236 0,5 50
850 - 64,5; 0,645 0,27 0,465 46,5
900 - 69,6; 0,696 0,304 0,442 44,2
950 - 71,6; 0,716 0,34 0,414 41,4
1000 - 71,9; 0,719 0,374 0,395 39,5
m
0,14
0,24
0,64
0,74
0,34 0,44 0,54
Wavelength, jam
Fig. 4. Dependence of the attenuation factor of light (a, m-1) in the soy-magnetite suspension on the wavelength (A, ^m)
The theoretical curve was built up by approximation of experimental data of the dependence of attenuation factor on the wavelength.
Using the equation:
Mean radius of the particles r and the parameters n, k, and N were determined. For this purpose, the function was built:
S(r, n, k, N) = J [Nnr2Q(r, n, k, a;) -a; j,
i=0
where Ai is the wavelength, at which the attenuation factor ai was measured.
The values of parameters r, n, k, N, at which function S (r, n, k , N) has a minimum, were determined by the method of the least squares. The calculation of minimization function was performed using the Mathcad software program.
An additional control of the views of graphs with the experimental points ai and curve a (r, n, N, k, A), which must pass near these points, was carried out (Fig. 4). The value of function S (r, n, k, N), which also depends on the initial approximations and must be minimal, was controlled.
For the studied soy-magnetite suspension, the following values were obtained r=38 nm, n=1,48, k=0,01, N=1,43x x1012 m-3.
The values of indices of refraction and absorption correlate satisfactorily with the reference data for magnetite: in the range of wavelengths from 0,4 to 0,8 |_im, its refraction index changes from 1,9 to 1,7, and the rate of absorption - from 0,1 to 0,01.
The obtained data were used in the MathCAD program for determining the parameters P and |i in the function of distribution of particles by size.
Fig. 5 shows the graph of normed function of distribution of particles f(r) by size.
For comparison, Fig. 6 shows the histogram of distribution of the particles of magnetite in the soy-magnetite suspension (SMS) by size, obtained as a result of processing the observations with the use of the electronic microscope, which shows that the results of both methods are consistent with one another.
Fig. 7 shows the image of the particles made in the course of electronic and microscopic observations.
As one can see in the given transmission microscope - TMM (Fig. 7), aggregation of the particles occurs with formation of clusters. Grouping of the particles in clusters provides the circuit of magnetic flux and can be explained by the absence of external magnetic field when conducting the electronic and microscopic studies [35]. In this case, it can be clearly seen that the clusters consist of small particles; the boundaries of each particle are clearly visible.
Knowing the size of the particles, their concentration in the suspension was also found. Table 3 and Fig. 8 display results of the study of changes in the quantity (concentration) of particles per 1 cm3 of the suspension during 45 days.
♦ai = f (Ai)
—Theoretical curve
Table 3
a(N, r, m, A) = Nnr2Q(r, m, A),
where r is the radius of the particle, m=n-iK, n is the index of refraction, k is the absorption index, A is the wavelength in the medium that surrounds the particle, Q is the factor of attenuation efficiency.
Quantity of particles per 1 cm3 of the soy-magnetite suspension
Quantity of magnetite partit cles per 1cm3 of suspension Exposure time of SMS, t, h
0 0,5 1,0 24,0 48,0 1080,0
1,43-1012 1,424012 1,404012 1,34-1012 1,23-1012 1.191012
f(r)
S N .2
500 400 300 200 100 0
f(r)
0
10 20 30 40 50 60 70 80
Radius of particles, r,nm
Fig. 5. Distribution of particles of magnetite in the soy-magnetite suspension (SMS) by size, measured by optical method
f(r)
500 s 50
esle
ll 44000
330 200 100
• 0 Q
0 20 26 28 29 32 36 38 40 45 46 49 55 60 65 79
Radius! oO pprticlee, r, nm
Fig. 6. Histogram of distribution of the particles of magnetite in the soy-magnetite suspension (SMS), obtained as a result of processing observations using the electronic microscope
° O
s N 2 ' «
JO
Fig. 7. Electronic microphotograph of the particles of magnetite in SMS
By the experimental data, given in Table 3 and in Fig. 8, it is possible to tell sedimentation stability and dispersity of LMS (by the example of SMS).
The experimental data on the dependence of transmission factor (T, %) on the wavelength of light (A,, nm) for the soy-magnetite suspensions (SMS) of different composition and with different concentration of Fe(tot.) are shown in Tables 4, 5 and Fig. 9, 10.
Transmission spectra of diluted suspensions (concentration of 4,85 mg/1) are shown in Fig. 9.
The assessment of the aggregation stability was carried out using the kinetic measurements.
Fig. 10 shows kinetic dependences of the transmission factor for suspensions with different concentration of magnetite (Fetot) and the SMS without stabilizer (mono-acylglycerol). The efficiency of the applied method of stabilization may be evaluated by comparing the kinetics of sedimentation to the case of the soy-magnetite suspension of equal concentration, in which there was no a surface active substance (stabilizer). Existence of different fractions of magnetite particles and the intensity of their aggregation determines the non-linear law of change in the transmission coefficient for magnetite suspensions without a stabilizer or with high content of magnetite.
Approximating the obtained dependences by straight lines and extrapolating them to achieving T=100 %, it is possible to estimate the average effective radius of the particles. Table 6 and Fig. 11 present the temporary dependences of the transmission factor of the studied suspensions at the wavelength of 600 nm. The obtained values of sedimentation time and effective mean radius are given in Table 7.
By the data of Table 7, it is possible to estimate the effective radius of particles in the LMS of different concentration as well as the aggregation stability of suspensions.
N=f(r)
■N=f(r )
Exposure time of suspension, t, year.
Fig. 8. Change of concentration of magnetite particles in the soy-magnetite suspension over time
Fe3O4 -Soybean oil(CO) -Monoacylglycerol (ma) _Fe3O4+MA+CO
200 300 400 500 600 700 800 900 1000
Wavelengths of light (X,nm)
Fig. 9. Dependence of transmission factor (T, %) on the wavelength of light (A, nm) for the soy-magnetite suspensions (SMS) of different composition
Table 4
Dependence of transmission factor (T, %) on the wavelength of light (X, nm) for the soy-magnetite suspensions (SMS) of different composition (the concentration of suspensions is 4,85 mg/l)
Wavelength of light (X, nm) Fe3Ü4 Monoacylglycerol Soy bean oil (SO) Fe3O4+MA Fe3O4+CO MA+CO Fe3O4+MA+CO
200 13 9 5 9 7 10 10
205 22 9 6 11 9 12 10
225 24 10 6 14 13 16 12
230 23 22 9 20 18 19 14
250 25 28 16 26 23 25 20
275 26 31 27 29 27 28 30
300 28 34 30 35 31 32 33
310 29 37 33 39 35 36 36
350 27 42 38 43 39 39 37
360 28 46 42 40 36 44 38
375 27 51 47 44 40 48 42
400 29 56 52 50 48 52 43
450 26 71 65 47 46 54 44
490 25 77 73 43 44 62 42
500 24 80 76 42 43 66 41
540 23 84 80 41 42 71 40
550 34 86 82 47 49 78 45
600 50 89 85 56 58 82 57
650 60 90 86 64 66 85 67
700 65 91 87 72 70 87 72
750 68 92 88 78 76 90 73
800 70 92 89 82 80 92 74
850 71 92 90 82 80 92 75
900 72 92 90 81 79 92 75
950 72 92 90 80 79 91 75
1000 72 92 90 80 79 91 75
Table 5
Dependence of transmission factor (T, %) on the wavelength of light (X, nm) for the soy-magnetite suspensions (SMS) of different concentration
Transmission factor T, %
Wavelength of light X, nm Concentration of Fetot in suspension, mg/l
4, 85 mg/l 9,75 mg/l 19,5 mg/l 38,9 mg/l
200 25 16 12 10
205 26 17 13 10
225 28 19 15 12
230 31 24 17 14
250 33 28 19 16
275 35 30 21 19
300 37 32 24 21
310 40 36 27 24
350 43 39 30 27
360 46 42 33 30
375 48 45 36 33
400 52 49 39 36
450 53 50 40 37
490 50 48 38 35
500 46 45 37 33
540 45 44 36 32
550 48 46 37 35
600 57 55 48 47
650 67 63 59 53
700 76 72 64 56
750 81 75 69 59
800 84 77 73 65
850 86 79 75 68
900 86 80 77 68
950 86 80 77 68
1000 86 80 77 68
i-T
4, 85 mg/l 9,75 mg/l -19,5 mg/l -38,9 mg/l
Wavelength, X, nm
Fig. 10. Dependence of transmission factor (T, %) on the wavelength of light (A, m) for the soy-magnetite suspensions (SMS) of different concentrations
100 90 80 70 60 50 40 30 20 10 0
- 4, 85 mg/l
- 9,75 mg/l 19,5 mg/l
-38,9 mg/l -4, 85 mg/l
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000
Exposure time of LMS, x, c Fig. 11. Temporary dependences of transmission factor (T, %) on the wavelength of 600 nm for the soy-magnetite suspensions (SMS) of different concentrations
Тable 6
Temporary dependences of transmission factor (T, %) of the soy-magnetite suspensions (SMS) of different concentrations on the wavelength of light (A=600 nm)
Transmission factor T, %
Exposure time of suspension t, h. Concentration of Fetot in suspension, mg/l
4,85 mg/l 9,75 mg/l 19,5 mg/l 38,9 mg/l 4,85 mg/l without SAS
0 67 63 59 53 58
1800 68,4 64,8 61,3 56,9 72,7
3600 69,2 66 63,2 64,5 82,7
6000 71,7 67,3 66,9 68,9 89,8
Таble 7
Results of calculation of sedimentation time tsed and mean effective radius of the particles reff at different concentration of suspension
Parameter Concentration of Fetot., mg/l
4,85 9,75 19,5 38,9
tsed, time 454 228 168 147
reff, nm 76 92 146 168
6. Discussion of results of studying stability of LMS
Synthetic magnetite (Fe3O4) is ultra-thin black powder, the size of the particles is of the order 30 nm, non-toxic, possesses useful properties: bactericidal, bacteriostatic, demonstrates antioxidant activeness; has beneficial effect on a human organism; is a source of easily assimilated iron [6-9]. That is why Fe3O4 may be proposed as a dispersion phase in the lipid constituents of biologically active and food supplements.
The obtained various lipid-magnetite suspensions, in which refined deodorized sunflower oil, unrefined corn oil, unrefined soybean oil, beef fat, pork fat, unrefined salomas for margarine industry, milk fat substitute "Violia-Molfat 3" and confectionary fat "Shortening" were used as dispersion medium.
Using the methods of photometry and electronic microscopy, the assessment of sedimentary stability of the lipid-magnetite suspensions was carried out, the sizes of particles of magnetite with SAS, the functions of distribution of the particles of magnetite Fe304 by size were determined, their comprehensive index of refraction and their concentration in suspensions, for example, the diameter of the particles in the soy-magnetite suspension equals 76 nm.
Analysis of Fig. 2 and Table 1 shows that in the course of time (0-48,0 hours) and with an increase in the wavelength (210-1000 nm), we observed a gradual increase in the transmission factor from 25 % (210 nm) to 71,9 % (1000 nm) at 0 hours of suspension exposure; from 27,5 % (210 nm) to 81,2 % (1000 nm) at the maximum exposure time of suspension (48 hours).
From Table 1 and Fig. 3 it is also visible that the largest change in the transmission factor (AT, %) with the course of time is observed at wavelengths 600 and 650 nm (30,7 and 25,8 %), respectively. At other wavelengths, AT was equal to approximately 18,4 %. Therefore, taking into account the accuracy of the photometric diagnostic method for determining stability of the suspension, it is better to recommend the wavelengths at which the accuracy of determining will be higher, i. e., 600-650 nm; then AT starts to fall gradually. The kinetic studies were also carried out at the wavelength of light of 600 nm.
It was experimentally found that all studied lipid-magnetite suspensions are rather stable over time. Various ratios of components of the lipid-magnetite suspensions were studied, in this case, the best results of stability were demonstrated by the suspensions in which the ratio of Fe304:SAS=0,02 g:0,35 g or 0, 04 of mass %:0,70 mass % and 0,025 %:0,35 g or 0,05 mass %:0,70 mass %. Since the study relied on the medical and biological requirements, the suspensions with the ratio of Fe304:SAS=0,025 g:0,35 g or 0,05 mass %:0,70 mas % were selected.
Based on the analysis of the experimental points Oj=f(Ai) (Table 2) and the theoretical curve a=f(r, n, N, k, A), which was built up by approximation of the experimental data of the dependence of attenuation factor on the length of wave which passes near these points (Fig. 4), the following values for the soy-magnetite suspension (SMS) were obtained: r=38 nm,
200
300
400
800
900
1000
n=1.48, k=0.01, N=1,43x1012 m-3. In this case, the value of function S (r, n, k, N), which also depends on the initial approximations and should be minimal, was also controlled.
It should be noted that the values of the indices of refraction (n) and absorption (k) correlate satisfactorily with the reference data for magnetite; in the range of wavelengths from 0,4 to 0,9 ^m the index of refraction changes from 1,9 to 1,7, and the absorption index - from 0,1 to 0,01.
The obtained results were used in the MathCAD program to calculate minimization function and to determine parameters P and ^ in the function of distribution of particles by diameter. Fig. 5 shows the graph of the normed function of particles distribution f(r) by size that correlates well with the histogram (Fig. 6), received as a result of processing the TMM data of the SMS sample images (Fig. 7). The number of particles in the sample for determining the average values was not less than 500. The established function is symmetric and rather narrow, which indicates the system of the synthesized nanoparticles as homogeneous with a low degree of polydispersity. The established order of the average size of the particles is <d>~38 nm.
The concentration (the number of particles in 1 cm3) of suspension was determined, which, for example during preparation, is N=1,43-1012 cm-3.
The decrease in the number of particles of magnetite with SAS in 1 cm3 of the soy-magnetite suspension was established: within 48 hours, the concentration in 1 cm3 decreased by 20 % - from 1,434012 to 1,191012 cm-3 (Table 3).
Analysis of Table 3 and Fig. 8 demonstrates that the number of particles in a layer of suspension decreases by 0,7 % within 0,5 hours, within 1,0 hour - by 2,1 %; within 24 hours - by 6,7 %, within 48 hours - by 16,5 % and in 45 days - by 20.0 %. The obtained data indicate partial homogeneity of the particles of magnetite - the largest particles settle within the first 24 hours.
The analysis of the sedimentation process in suspensions of different composition and concentration was carried out by measuring the transmission factor.
The optical transmission spectra were studied for the soy-magnetite suspensions (SMS) of different concentrations.
To determine the contribution of individual components of the solution to the resulting spectrum, the suspensions of magnetite without a stabilizer were prepared. The obtained optical transmission spectra are given in Tables 4, 5 and in Fig. 9, 10. In UV-Spectra (Fig. 9), there are weak transition strips n^rc* at 200-210 nm, which are characteristic for the saturated acyl radicals (monoacylglycerol - MA), and the stronger transition strips rc^rc * at 210-230 nm, which are characteristic for the a, P-unsaturated acyls (soybean oil - SO). In the spectrum of magnetite, broad absorption strips are observed in the area of 490 and 540 nm, associated with lattice fluctuations of Fe-O - links in tetra- and octahedral positions of Fe3O4. By comparing these curves of dependence of the transmission factor on the wavelength for the SMS, the special features of the spectrum, characteristic for magnetite, monoacylglycerol and soybean oil, can be seen.
The comparison of the transmission spectra of suspensions with different degrees of dilution (Fig. 10) shows chemical identity of the samples. The evaluation of aggregate stability was carried out using the kinetic measurements. In Table 6 and Fig. 11, the dependence of kinetic transmission factor for suspensions with different concentration of magnetite (Fetot) and the SMS without a stabilizer (monoacylglycerol) is shown. Analysis of Fig. 11
shows a nonlinear law of changing the transmission factor for magnetite suspensions without a stabilizer or with high content of magnetite (38,9 mg/l), which can be explained by existence of different fractions of the particles of magnetite and their aggregation. In the UV-area of the spectrum, at low concentrations there is a direct proportionality between the transmission factor and the concentration of (Fe3ar), i. e., absorbing centers of Fe3O4.
The calculation of the effective mean radius (Table 7) for SMS with the concentration of 38,9 mg/l gives a lowered value, which, probably, is predetermined by the constraints of linear approximation, as the dependence T(t) in this case is nonlinear. One can make an assumption that an increase in the concentration to 38,9 mg/l results in significant decrease in the aggregation stability.
The average radius of the particles of magnetite in the lipid suspension without a stabilizer is possible to be estimated reliably in this way, the linear extrapolation of the curve allows receiving (reff)=400 nm. Visually, the SMS demonstrated high aggregation stability with the total sedimentation time equal to several tens of hours.
The estimation of the effective mean radius of the particles from the kinetics of sedimentation gives the value of 76-168 nm, and the dependence (reff) on C(Fe(ov.)) has a linear character up to the concentration of 38.9 mg/l. The process of sedimentation in the case of high concentrations and pure magnetite, which is not stabilized by monoacylglycerol, has a distinctly expressed nonlinear character, which is connected with the intensive aggregation of the particles and different sedimentation rate for various fractions.
7. Conclusions
1. We conducted evaluation of sedimentation and aggregate stability of the lipid-magnetite suspensions (in which the dispersion medium was created by corn, sunflower, soybean oil, beef and pork fats, confectionery fats, salomas). All suspensions are stable enough over time. The best results for stability were demonstrated by suspensions, in which the ratio Fe3O4:SAS=0,02 g:0,35 g or 0,04 mass %:0,70 mass % and 0,025:0,35g or 0,05 mass %:0,70 mass %. The size of the particles of magnetite with SAS was determined. Diameter of the particles is 76 nm. It was found that over time (0-48.0 h) and with increasing the length of the wave (210-1000 nm), a gradual increase in the coefficient of transmission is observed, from 25 % (210 nm) to 71.9 % (1000 nm) at 0 hours of suspension exposure; from 27.5 % (210 nm) to 81.2 % (1000 nm) at the maximum exposure time of suspension (48 hours).
2. We determined concentration of the particles of magnetite, stabilized by a surface active substance - the concentration (the number of particles in 1 cm3) during preparation of suspension is equal to N=1,43-1012 cm-3. The reduction in the number of particles of magnetite with SAS per 1 cm3 of the soy-magnetite suspension was revealed: in 48 hours, the concentration per 1 cm3 decreased by 20 % - from 1,43-1012 to 1,191012 cm-3. The following values for the soy-magnetite suspension (SMS) were defined: r=38 nm, n=1,48, k=0,01.
The established distribution function is symmetric and rather narrow, which indicates that the system of the synthesized nanoparticles is homogeneous with a low degree of polydis-persity. The defined order of the average size of the particles is <r>~38 nm.
3. In the UV-Spectra, there are weak transition strips n^rc * at 200-210 nm, which are characteristic for the saturated acyl radicals (monoacylglycerol - MA) and the stronger transition strips rc^rc* at 210-230 nm, which are characteristic for the a, P-unsaturated acyls (soybean oil - SB). In the spectrum of magnetite, broad strips of absorption are observed in the area of 490 and 540 nm, associated with lattice fluctuations of the Fe-O-links in tetra- and octahedral positions of Fe3O4. By comparing these curves of dependence of the transmission factor on the wavelength for SMS, the special features of the spectrum, characteristic for magnetite, monoacylglycerol and oil (lipid), can be seen. A comparison of the transmission spectra of suspensions with different degrees of dilution shows chemical identity of the samples.
4. Analysis of the kinetic dependencies of coefficient of transmission for LMS shows a nonlinear law of change in
the coefficient of transmission for suspensions without a stabilizer or with high content of magnetite (38.9 mg/l), which can be explained by existence of different fractions of the particles of magnetite and their aggragation. In the UV area of the spectrum, at low concentrations, there is direct proportionality between the transmission coefficient and the concentration Fe(ov), i. e., absorbing centers of Fe3O4. The estimate of effective mean radius of the particles from the kinetics of sedimentation gives value of 76-168 nm, in this case, up to the concentration of 38.9 mg/l, the dependence (reff) on C(Fe(ov.) ) has linear character. The process of sedimentation in the case of high concentrations and pure magnetite, which is not stabilized by monoacylglycer-ol, displays vividly expressed nonlinear character associated with intensive aggregation of the particles and different rates of sedimentation for various fractions.
References
1. Skurihin, I. M. VsYo o pische s tochki zreniya himika [Text] / I. M. Skurihin. - Moscow: Vyissh.shk., 1991. - P. 33-40.
2. Tyutyunnikov, B. N. Himiya zhirov; 3rd edition [Text] / B. N. Tyutyunnikov. - Moscow: Kolos, 1992. - 448 p.
3. Roginskiy, V. A. Kinetika okisleniya efirov polinenasyischennyih zhirnyih kislot, ingibirovannogo zameschennyimi fenolami [Text] / V. A. Roginskiy // Kinetika i kataliz. - 1990. - Vol. 31, Issue 3. - P. 546-552.
4. Demydov, I. M. Vplyv stupenya nenasychenosti oliy na sklad vtorynnykh produktiv yikh okysnenya [Text]: tez. dop. Mizhn. nauk.-tekhn. konf. / I. M. Demydov, A. V. Hryhorova // Tekhnichni nauky: stan, dosyahnennya i per-spektyvy rozvytku m»yasnoyi, oliye-zhyrovoyi ta molochnoyi haluzey, 2012. - P. 42-43.
5. Demidov, I. N. Opredelenie srokov hraneniya zhirov i zhirovyih produktov uskorennyim metodom [Text]: tez. dop. VII Mezhd. konf. / I. N. Demidov, D. V. Nevmivaka // Maslozhirovaya otrasl: tehnologii i ryinok, 2014. - P. 27-28.
6. Denysova, A. Yu. Doslidzhennya vplyvu zhyro-mahnetytovoyi suspenziyi na termin zberihannya tvarynnykh zhyriv [Text]: tez. dop. Mizhnar. nauk.-prakt. konf. / A. Yu. Denysova, Y. V. Tsykhanovskaya, O. B. Skorodumova, Ya. M. Honcharenko, H. O. Pryymak,
I. V. Shevchenko // Prohresyvna tekhnika ta tekhnolohiyi kharchovykh vyrobnytstv, restorannoho ta hotel'noho hospodarstv i torhivli. Ekonomichna stratehiya i perspektyvy rozvytku sfery torhivli ta posluh. - 2013. - Part 1. - P. 71-72.
7. Ilyuha, N. G. Tehnologiya proizvodstva i pokazateli kachestva pischevoy dobavki na osnove magnetita [Text] / N. G. Ilyuha, Z. V. Barsova, V. A. Kovalenko, I. V. Tsihanovskaya // Eastern-European Journal of Enterprise Technologies. - 2010. - Vol. 6, Issue 10 (48). - P. 32-35. - Available at: http://journals.uran.ua/eejet/article/view/5847/5271
8. Tsihanovskaya, I. V. Izuchenie rastvorimosti magnetita v usloviyah, imitiruyuschih pischevaritelnyie protsessyi zheludochno-kishechnogo trakta [Text] / I. V. Tsihanovskaya, A. Yu. Denisova, O. B. Skorodumova, E. Ya. Levitin, V. A. Kovalenko, A. V. Aleksandrov, Z. V. Barsova // Eastern-European Journal of Enterprise Technologies. - 2012. - Vol. 6, Issue 6 (60). -P. 29-31. - Available at: http://journals.uran.ua/eejet/article/view/5547/4988
9. Tsykhanovs'ka, I. V. Doslidzhennya protsesiv okysnyuval'nykh ta termichnykh peretvorenn' v systemi: oliya - lipido - mahnetytova suspenziya [Text]: zb. nauk. pr. / I. V. Tsykhanovs'ka, Z. V. Barsova, I. M. Demydov, L. F. Pavlots'ka // Prohresyvna tekhnika ta tekhnolohiyi kharchovykh vyrobnytstv restorannoho hospodarstva i torhivli. - 2015. - Vol. 1 (21). - P. 353-362.
10. Krushenko, G. G. Problemyi opredeleniya razmerov nanochastits [Text] / G. G. Krushenko, S. N. Reshetnikova // Vestnik Sibirskogo gosudarstvennogo aerokosmicheskogo universiteta imeni akademika M. F. Reshetneva. - 2011. - Vol. 2. - P. 167-170.
11. Suzdalev, I. P. Nanotehnologiya: fiziko-himiya nanoklasterov, nanostruktur i nanomaterialov [Text] / I. P. Suzdalev. - Moscow: KomKniga, 2006. - 365 p.
12. Kecskes, L. J. Characterization of a nanosized iron powder by comparative methods [Text] / L. J. Kecskes, R. H. Woodman,
S. F. Trevino, B. R. Klotz, S. G. Hirsch, B. L. Gersten // KONA. - 2003. - Vol. 21. - P. 143-149. doi: 10.14356/kona.2003017
13. NaBond Technologies Co [Electronic resource]. - Available at: http://www.nabond.com/TiN_nanopowder.html
14. Egorova, E. M. Stabilnyie nanochastitsyi serebra v vodnih dispersiyah, poluchennyih iz mitsellyarnyih rastvorov [Text] / E. M. Egorova et. al. // Zhurnal prikladnoy himii. - 2002. - Vol. 75, Issue 10. - P. 1620-1625.
15. Pimenova, N. V. Poroshki volframa, poluchennyie razlichnyimi sposobami [Text] / N. V. Pimenova // Tehnologiya metallov. -2011. - Vol. 2. - P. 25-27.
16. Xu, R. Particle Characterization: Light Scattering Methods [Text] / R. Xu. - N.Y.: Kluwer Academic Publishers, 2001. - 410 p.
17. Mamani, J. B. Particokinetics: computational analysis of the superparamagnetic iron oxide nanoparticles deposition process [Text] / J. B. Mamani, T. T. Sibov, C. A. Caous, Jr. E. Amaro, L. F. Gamarra // International Journal of Nanomedicine. - 2012. - Vol. 2012:7. -P. 2699-2712. doi: 10.2147/ijn.s30074
18. Lou, W. On the Electromagnetic Scattering and Ab-sorption of Agglomerated Small Spherical Particles [Text] / W. Lou, T. T. Charalalampopoulos // Journal of Physics D: Applied Physics. - 1994. - Vol. 27, Issue 11. - P. 2258-2270. doi: 10.1088/00223727/27/11/004
19. Di Stasio, S. Feasibility of an Optical Experimental Method for the Sizing of Primary Spherules in Sub-Micron Agglomerates by Polarized Light Scattering [Text] / S. Di Stasio // Applied Physics B: Lasers and Optics. - 2000. - Vol. 70, Issue 4. - P. 635-643. doi: 10.1007/s003400050872
20. Mulholland, G. W. Measurement of 100 nm and 60 nm Particle Standards by Differential Mobility Analysis [Text] / G. W. Mulholland, M. K. Donnelly, Ch. R. Hadwood, S. R. Kukuck, V. A. Hackley, D. Y. H. Pui // Journal of Research of the National Institute of Standards and Technology. - 2006. - Vol. 111, Issue 4. - P. 257-312. doi: 10.6028/jres.111.022
21. Ivanov, L. A. Izmenenie svetovozvrascheniya ot steklyannyih mikrosharikov i progon kachestva sveto-vozvraschayuschih pokryitiy [Text] / L. A. Ivanov, D. V. Kizevetter, N. N. Kiselev et. al. // Opt. zhurn. - 2006. - Vol. 73, Issue 1. - P. 35-40.
22. Van de Hyulst, G. Rasseyanie sveta malyimi chastitsami [Text] / G. Van de Hyulst. - Moscow: IL, 1961. - 536 p.
23. Kerker, M. The scattering of light and other electromagnetic radiation [Text] / M. Kerker. - N.Y., London, Academic Press, 1969. -666 p.
24. Xu, R. Particle Characterization: Light Scattering Methods [Text] / R. Xu. - N.Y.: Kluwer Academic Publishers, 2001. - 410 p.
25. Papok, I. M. Using the dynamic light-scattering method for the analysis of a blood-serum model solution [Text] / I. M. Papok, G. P. Petrova, K. A. Anenkova, E. A. Papish // Moscow University Physics Bulletin. - 2012. - Vol. 67, Issue 5. - P. 452-456. doi: 10.3103/s0027134912050104
26. Sohrabi-Gilani, N. Extraction of ultratrace amounts of nelfinavir from biological samples and pharmaceutical formulations using surfactant-modified magnetite nanoparticles followed by spectrophotometric determination [Text] / N. Sohrabi-Gilani, S. Makani // Microchemical Journal. - 2016. - Vol. 129. - P. 332-338. doi: 10.1016/j.microc.2016.06.003
27. Sutorikhin, I. Issledovaniya kontsentratsii i razmerov chastits vodnoy vzvesi s pomoschyu opticheskogo metoda fluktuatsiy prozrachnosti [Text] / Sutorikhin, I., Bukaty, V., Zalaeva, U., & Akulova, O. // Izvestiya of Altai State University. - 2013. - Vol. 1, Issue 2. - P. 189-193. doi 10.14258/izvasu(2013)1.2-39
28. Ershov, A. E. Effects of Size Polydispersity on the Extinction Spectra of Colloidal Nanoparticle Aggregates [Text] / A. E. Ershov, I. L. Isaev, P. N. Semina, V. A. Markel, S. V. Karpov // Physical Review B. - 2012. - Vol. 85, Issue 4. doi: 10.1103/physrevb.85.045421
29. Patent. na korisnu model # 54284, MPK S 01 G 49/00. SposIb otrimannya magnetitu [Text] / Ilyuha M. G, Tsihanovska I. V., Barsova Z. V., TImofeEva V. P., Vedernikova I. O. - published: 10.11.2010. Byul. # 21. - 4 p.
30. Van de Hulst, H. Light Scattering by Small Particles [Text] / H. Van de Hulst. - N.Y.: J. Willey & Sons, 1957. - 536 p.
31. Voyutskiy, S. S. Kurs kolloidnoy himii; 2-e izd. [Text] / S. S. Voyutskiy. - Mosocw: Himiya, 1975. - 512 p.
32. Ivanov, L. A. Izmenenie svetovozvrascheniya ot steklyannyih mikrosharikov i progon kachestva svetovozvraschayuschih pokritiy [Text] / L. A. Ivanov, D. V. Kizevetter, N. N. Kiselev et. al. // Opt. zhurn. - 2006. - Vol. 73, Issue 1. - P. 35-40.
33. Kizevetter, D. V. Odnovremennoe izmerenie razmerov i skorosti dvizheniya chastits [Text] / D. V. Kizevetter, V. I. Malyugin // Zhurn. tehn. fiziki. - 2009. - Vol. 79, Issue 2. - P. 90-95.
34. Chekhun, V. Mahnitni nanostruktury v pukhlynnykh klitynakh [Text] / V. Chekhun, S. Horobets', O. Horobets', I. Dem»yanenko // Visn. NAN Ukrayiny. - 2011. - Vol. 11. - P. 13-20.
35. Alexandrov, A. Stability and morphological characteristics of lipid-magnetite suspensions [Text] / A. Alexandrov, I. Tsykhanovska, T. Gontar, N. Kokodiy, N. Dotsenko // Eureka: Life Sciences. - 2016. - Vol. 3 (3). - P. 14-25. doi: 10.21303/2504-5695.2016.00143
