Journal of Science: Advanced Materials and Devices (2018) 107e112 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Size-dependent magnetic responsiveness of magnetite nanoparticles synthesised by co-precipitation and solvothermal methods Thanh Quang Bui*, Suong Nu-Cam Ton, Anh Trong Duong, Hoa Thai Tran Department of Chemistry, College of Sciences, Hue University, Viet Nam a r t i c l e i n f o a b s t r a c t Article history: Received 11 October 2017 Received in revised form 31 October 2017 Accepted November 2017 Available online 14 November 2017 The dependence of the magnetic responsiveness on magnetite nanoparticle size has been studied Monodisperse magnetite nanoparticles of 10 nm diameter were prepared by an ultrasonically enhanced co-precipitation procedure A carboxyl-functionalised solvothermal approach was applied to synthesise magnetite nanoparticles with an average size of 30 nm The particle sizes and their distribution have been determined by analysing TEM images and considering nanoparticle formation mechanisms The magnetic characterisation revealed an inverse dependence between the magnetite nanoparticle size and its ability to respond to external magnetic fields, which was explained by the decrease of magnetic dipoles inside the tailing-away crystal of the magnetite nanoparticles Negligible hysteresis with a small value of Oe was found for the 10 nm nanoparticles, while the larger value of 80 Oe was determined for the 30 nm nanoparticles © 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Fe3O4 Magnetite nanoparticles Co-precipitation Solvothermal Magnetic responsiveness-particle size relationship Introduction Nanostructured magnetic particles have been of great scientific and technological interest over the past decades because of their unique properties and highly potential applications Magnetite, well-known as the most strongly magnetic mineral in nature, has attracted diverse researches and applications such as magnetic recording technology, pigments, catalysis, photocatalysis, biomedical uses, and environmental processes [1] due to their high biological compatibility, room-temperature superparamagnetism, low toxicity, and easy preparation [2] In biological applications, magnetite nanoparticles have been considered as an ideal candidate for the development of hyperthermal therapies, localising hyperthermia by converting magnetic energy to heat at micro-scale based on their excellent magnetic field responsiveness [3] However, the ability of their response to an external magnetic field technically depends on the magnetic structure of the material, which originates from crystalline particle size [4,5] Many preparation methods of magnetite nanoparticles have been developed and reported in varied research works, such as coprecipitation, hydrothermal synthesis, solvothermal synthesis, sonochemical synthesis, and micro-emulsion [5,6] * Corresponding author 77 Nguyen Hue, Hue, Viet Nam E-mail addresses: thanh.qt.bui@gmail.com, thanh.qt.bui@husc.edu.vn (T.Q Bui) Peer review under responsibility of Vietnam National University, Hanoi Co-precipitation is the simplest and most efficient synthesis route to obtain the magnetic particles, based on the implementation of reaction (3) in aqueous solutions [7] In co-precipitation, a stoichiometric mixture of ferrous and ferric precursors in aqueous medium is used as an iron source, which yields superparamagnetic nanoparticles after adding an alkaline solution However, the size distribution of as-prepared nanoparticles by co-precipitation is relatively broad if insufficient assisting controls provided due to the presence of both nucleation and particle growth throughout the synthesis process [8] Precursor agent / Reducing agent (1) Reducing agent ỵ Fe3ỵ / Fe2ỵ ỵ By products (2) Fe2ỵ ỵ Fe3ỵ þ 8OHÀ / Fe3 O4 þ 4H2 O (3) Solvothermal method is one of the most popular methods for synthesising high-quality magnetite nanoparticles, based on the implementation of reaction (3) in non-aqueous organic solvents In solvothermal approaches, a mixture of suitable basic source, stabiliser, viscous solvent, reducing agent, and ferric salt as raw precursors, is heated to a specific temperature to create the required conditions for reaction (1) to initiate This leads to the next stage of partially reducing ferric as described in reaction (2) to obtain ferrous source for the formation of the magnetite nanoparticles https://doi.org/10.1016/j.jsamd.2017.11.002 2468-2179/© 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) 108 T.Q Bui et al / Journal of Science: Advanced Materials and Devices (2018) 107e112 following the reaction (3) Besides, by the utilisation of appropriate precursor agents, the synthesised magnetite nanoparticle sizes are efficiently tunable To the best of our knowledge, there have been several researches in the literature emphasising on the particle sizemagnetic properties However, they were commonly neither comparisons between samples synthesised from different routes [3,9], nor attention to differences between samples from the two most popular approaches [10], nor sufficient discussions on specific magnetic behaviours [11,12] Therefore, a distinguishable observation of the size-dependent magnetic responsiveness of magnetite nanoparticles synthesised from the two most popular approaches would be a significant contribution to the application-oriented investigations of nano-sized magnetic materials in general and magnetite nanomaterials in particular In this study, 10 nm magnetite nanoparticles were prepared by an enhanced procedure of co-precipitation based on ultrasonic assistance [13,14] Whilst, 30 nm magnetite nanoparticles were synthesised by a carboxyl-functionalised solvothermal approach [15] The magnetic responsiveness of the materials was derived from a room-temperature magnetic analysis The particle sizes and their distribution were evaluated by a data integrating investigation from various characterisations However, the represented dedication also disregarded the influence of agglomeration and aggregation states since these are natural trends of magnetite nanomaterials [16] and there are very few studies from the literature supporting the respective influence on the obtained coercivity Table summarizes the differences in synthesis procedure of M-01 and M-02 samples, respectively In addition, 3.5 g of as-prepared M-01 precipitates and 1.5 g trisodium citrate dihydrate were mixed with 100 mL deoxygenated distilled water for h with the aid of ultrasonic irradiation to create citrate-capped magnetite suspensions for band-gap energy analysing purpose 2.3 Characterisation The crystal structure of the final products was characterised by X-ray diffraction (XRD, D8-Advance-Bruker, Germany) equipped with Cu Ka radiation (l ¼ 1.5406 Å), and the mean crystalline size of the nanoparticles was calculated by Scherrer's equation using XRD data [17,18] The morphology of the synthesised products were observed by a transmission electron microscopy (TEM, Jeol-1010, Japan) The magnetic properties were investigated through collected magnetisation-hysteresis (M-H) curves using a vibrating sample magnetometer (VSM, PPMS-6000, USA) at room temperature The molecular structure of the citrate-capped magnetites were characterised with an infrared spectrometer (IR, Shimadzu IRPrestige-21, Japan) The ultraviolet-visible absorption spectra (UVVis spectrometer, Jasco V-660, Japan) were recorded for deriving the band gap analysis of the nanoparticles from as-prepared suspensions Results and discussion Experimental 3.1 Surface modification characterisation 2.1 Chemicals and reacting conditions Both samples of magnetite nanoparticles and citrate-capped magnetite nanoparticles from M-01 experiment were firstly characterised by IR spectroscopy (Fig 1) to demonstrate the capping role of citrate on the surface of magnetite to form as-prepared suspended solutions Two main absorption bands FeeO, at 565.14 cmÀ1, 397.34 cmÀ1 in magnetite spectra (see Fig 1a) and at 569.00 cmÀ1, 385.76 cmÀ1 in the one of citrate-capped magnetite (see Fig 1b), are observed corresponding to the intrinsic stretching vibrations of metaloxygen at tetrahedral site (Fetetra-O) and at octahedral site (FeoctaO), respectively [19e21] The shifts between the corresponding spectra suggest a partial cleavage of these metal-oxygen bonds on the surface of the magnetite nanoparticles forming (citrate) COOeFe bonds Also, high-intense peaks appearing at 3442.94 cmÀ1 and 1622.13 cmÀ1 in Fig 1b are assigned to the stretching vibrating modes of OeH and C]O, accordingly, in the capping-citrate molecules Also, a medium-intense peak at 1394.53 cmÀ1 in Fig 1b is inferred from the existence of CeH bending vibration in the molecule In addition, two weak peaks observed at 3429.83 cmÀ1 and 1627.92 cmÀ1 in Fig 1a could be referred to eOH vibrations of absorbed moisture on the surface of the magnetite nanoparticles [22e24] Ferrous chloride tetrahydrate (FeCl2$4H2O), ferric chloride hexahydrate (FeCl3$6H2O), hydrochloric acid (HCl, 37%), ammonia solution (NH3, 28%), ethylene glycol (C2H6O2), trisodium citrate dihydrate (Na3C6H5O7$2H2O), urea (NH2CONH2) were of analytical grade, purchased from Xilong Chemical Co., Ltd All chemicals were used without further purification In all experiments, reactant solutions were deoxygenated by Nitrogen bubbling for 30 before use Ultrasonic condition (Cole-Parmer-8892, USA) was deployed with 42 KHz, 100 W 2.2 Preparation of magnetite nanoparticles Magnetite nanoparticles were synthesised by co-precipitation and solvothermal methods following two procedures, notated as M-01 and M-02, respectively In the co-precipitation procedure (M-01 experiment), 1.5 mmol FeCl2$4H2O and 3.0 mmol FeCl3$6H2O were dissolved in 50 mL deoxygenated distilled water Under ultrasonic irradiation, 10 mL ammonia was rapidly introduced into the as-prepared iron precursor solutions at 40 C, bubbling with N2 The black precipitates were isolated from the solutions by magnetic decantation and washed by deoxygenated distilled water several times, then dried in an oven at 70 C In the solvothermal procedure (M-02 experiment), 7.2 mmol FeCl3$6H2O, 0.6 mmol Na3C6H5O7$2H2O, and 60 mmol NH2CONH2 were completely dissolved in 60 mL ethylene glycol with the aid of ultrasound and vigorous mechanical stirring The solution was sealed in a Teflon lined stainless-steel autoclave and then heated at 200 C for h After being cooled down to room temperature, the black sediments were separated by magnetic decantation and washed by deoxygenated ethanol and distilled water several times, then dried in an oven at 70 C 3.2 Morphology and particle size characterisation The TEM images shown in Fig reveal the observed morphology and sized distribution of the as-prepared Table Procedural differences of M-01 and M-02 samples Sample Synthesis method Assistance Surfactant M-01 M-02 Co-precipitation Solvothermal Ultrasonic irradiation None None Trisodium citrate T.Q Bui et al / Journal of Science: Advanced Materials and Devices (2018) 107e112 109 Fig IR spectra of (a) magnetite nanoparticles, and (b) citrate-capped magnetite nanoparticles Fig UV-Vis spectra of (a) sodium citrate solution, (b) M-02 suspension, and (c) M-01 suspension Fig TEM images of (aeb) M-01 sample and (ced) M-02 sample nanoparticles M-01 sample (Fig 2aeb) appears to have homogenously spherical nanoparticles with an average diameter of 10 nm, in form of nanoparticle agglomerates While M-02 sample (Fig 2ced) possesses a unidentifiable morphology and seemingly compacted clusters of particles with a broad size distribution, ranging from tens to hundreds nanometre in diameter Closer examinations on the TEM images of M-02 sample indicate that it might contain smaller nanocrystals with an average size ca 30 nm The analysis of UV-Vis spectra shown in Fig could provide a further confirmation of the size-observed differences As seen in Fig 3a, there is no pronounced peak in the spectrum of the sodium citrate solution Whilst, a steady increase of absorbance in M-02 suspension spectrum (see Fig 3b), for wavelengths drifting from 900 nm to 250 nm, could be related to the negligibly narrow band gap of original semi-metallic materials (< 0.1 eV) [25] Hence, M-02 nanoparticles absorbed continuously the increasing optical-energy, leading to a smooth change appearing on the plot However, a significantly noticeable peak, centred at the wavelength of 470 nm in the spectrum of M-01 suspension (Fig 3c), infers to the presence of a determined band gap which causes valence electrons to only absorbed a specific energy package in overcoming the respective insulated barrier This could be the effect of the band-gap stretching due to the decrease of the nanoparticle size In addition, the band gap of M-02 nanoparticles is 2.64 eV, which was calculated by Planck's formula [26] Fig illustrates and explains the band-gap stretching phenomenon by particle size tailing-off Bulk-sized particles of originally conductive materials, with an enormous number of available states for occupation, will absorb photon packages according to a wide continuous spectrum of wavelength However, by decreasing the number of atoms inside a particle as the consequence of reducing the particle size, the density of states inside the particle tends to be discrete Hence, the valence electrons could majorly be excited by absorbing a specific wavelength than otherwise, whose energies seem either too small that likely appear in far-infrared region or too high that likely fall into X-rays region This leads to a specific peak appearing in the UV-Vis spectrum (250 nme900 nm) of M-01 suspension, and a steady increase of absorption in the UV-Vis spectrum of M-02 considerably bulk-particle suspension The XRD patterns shown in Fig reflect the crystal structure of the synthesised nanoparticle samples, M-01 (Fig 5a) and M-02 (Fig 5b) The recorded XRD patterns show a good consistency with the standard data of magnetite crystal (Fe3O4, JCPDS 00-0011111) without any extra noticeable peaks Five pronounced characteristic peaks could be clearly identified correspondingly to (200), (311), (400), (511), and (440) crystalline planes of magnetite crystalline structrure The interplanar spacings, calculated and referenced as shown in Table 2, indicate that all samples possess the inverse cubic spinel structure of magnetite with over 99 % being consistent with the referenced data The average grain sizes of the magnetite nanoparticles in M-01 and M-02 samples were calculated from Scherrer's equation with full-width at halfmaximum values of the corresponding strongest peaks (311) as nm and 28 nm, respectively In addition, the XRD patterns of M01 sample appearing with lower intensity and more broaden reflections could be referred to the decrease of grain size of the Fig Illustration of band gap stretching phenomenon by particle size tailing-off 110 T.Q Bui et al / Journal of Science: Advanced Materials and Devices (2018) 107e112 Fig XRD patterns and identified lattice indices of (a) M-01 and (b) M-02 samples Table Comparison of the interplanar spacings of M-01 and M-02 samples to the standard XRD data of magnetite (Fe3O4, JCPDS 00-001-1111) hkl 200 311 400 511 440 M-01 M-02 d (Å) Completeness (%) d (Å) Completeness (%) 2.955 2.521 2.096 1.603 1.479 99.59 99.56 99.86 99.26 100.00 2.953 2.519 2.090 1.610 1.475 99.53 99.49 99.57 99.69 99.73 Standard data 2.967 2.532 2.099 1.615 1.479 Fig Particle formation mechanisms of (a) M-01 nanoparticles and (b) M-02 nanocluster nanoparticles, leading to X-rays being more strongly and widely diffracted than the one obtained from M-02 sample [27] The considerable inconsistency in the obtained results from M02 size measurements, between TEM images and XRD analysis, could be explained by the formation mechanism of the magnetite nanocluster structures, schematically illustrated in Fig 6b [15] Due to slow formation of the magnetite nanonuclei, the citrate molecules were adsorbed on the surface of the crystallites covalently resulting in electrostatically repelling forces between the neighbouring nanocrystals This not only promoted the hydrophilic ability of the magnetite nanoparticles, but also induced electrostatic surfactants from the negatively charged citrate molecules covering the surface of the nanoparticles In contrast, the surface tension nature of nanomaterials together with magnetic forces caused the nanoparticle agglomeration toward the reduction of their surface energy As the consequence of the unbalance between the strong surface tension and the weaker electrostatic repulsion, the magnetite nanoparticles spontaneously agglomerated to form the ultimate subunit-nanostructures Therefore, the discrete nanocrystals, of ca 28 nm in average size as calculated by Scherrer's equation from the XRD data, represent the primary structure, irrespective of the larger clusters, with size ranging from several tens to hundreds nanometres observed in the TEM images, exhibit the secondary structure of the magnetite material The reasonable correspondence of M-01 particle sizes, deduced from XRD data and recognised from TEM images, could be explained by the procedure of initiating the reaction environment and by the original properties of ultrasound in liquid mediums [28,29], schematically illustrated in Fig 6a First, by pouring the ammonia rapidly into the iron precursor solution, the medium state promptly reached to the solubility threshold and swiftly overcame the condensational growing process, also known as Ostwald ripening process [30], leading to a homogeneous mass nucleation [31] with uniformly sized monodispersed nanoparticles as the resulting products Besides, the mechanical ultrasonic interactions in the liquid medium could physically interfere down to the surface of the nano-scaled crystallites, holding them separatedly suspended in the reaction medium [14] As a result, the products appeared as discrete mono-sized-distributed nanoparticles, leading to the correspondence between the particle sizes extracted from the both TEM and XRD characterisations In addition, the lower bound on XRD-calculated particle size, in comparison with the one from TEM images, could be explained by inhomogeneous strain and crystal lattice imperfections on the surface of the nanoparticles [32] 3.3 Magnetic characterisation Fig represents the room-temperature M-H curves of the asprepared magnetite samples, measured by cycling the external magnetic field between À11000 Oe and 11000 Oe M-01 (Fig 7a), and M-02 (Fig 7b) exhibit soft magnetic behaviour with relatively high saturation magnetisation (Ms) values of 57.7 emu$gÀ1 and 67.7 emu$gÀ1, respectively Whilst, the obtained hysteresis values are considerably distinguishable, with negligible Oe and 80 Oe, respectively, referring to the coercivity values of M-01 sample and M-02 sample The relatively high coercivity value of M-02 sample is inferred from the over-threshold particle size of superparamagnetism, ca 25 nm, of magnetite material [33] Such over-sized particles perform as multi-domain crystalline granules [5], whose magnetic moments resisting each other from the proper response to an external magnetic field (Fig 8b) Whilst, a negligible coercivity value (weak magnetic reluctance) indicates the retained superparamagnetic property of M-01 sample after the completion of the synthesis process The observed features could be explained by the T.Q Bui et al / Journal of Science: Advanced Materials and Devices (2018) 107e112 111 UV-Vis spectroscopy, in which, TEM images reveal the morphology, XRD data infers the estimated grain size, and UV-Vis spectra further confirm the difference of nanoparticle sizes by band-gap stretching phenomenon observation References Fig Room-temperature M-H curves of (a) M-01 sample, and (b) M-02 sample Fig External-magnetic field responsiveness of (a) a single domain M-01 nanoparticle and (b) a multi-domain M-02 nanoparticle fact that the as-prepared tiny and discrete magnetite nanoparticles contain quasi-mono magnetons, single magnetic dipoles, which freely alter following the applied external magnetic fields, and instantaneously respond to the magnetic alternatives (Fig 8a) In brief, the decrease of the particle size leads to the decrease of the number of containing magnetic dipoles; and the latter in turn leads to the reduction of the magnetic reluctance caused by the internal coupling interactions between the magnetic moments Conclusion This study showed the dependence of the magnetic responsiveness on particle size of magnetite nanoparticles synthesised by co-precipitation and solvothermal methods, and revealed that the magnetic responsiveness increases with the decrease of the particle size The negligible hysteresis of Oe correlates to the particle size of ca 10 nm; whereas, the magnetite nanoparticles with ca 30 nm in diameter exhibit higher magnetic reluctance, indicated by a larger coercivity value of 80 Oe The determination of nanoparticle size could be performed by an integrated analysis of TEM, XRD, and , M.A Ramazanov, F Hajiyeva, [1] H Shirinova, L Di Palma, F Sarasini, J Tirillo D Sannino, M Polichetti, A Galluzzi, Synthesis and characterization of magnetic nanocomposites for environmental remediation, Chem Eng Trans 47 (2016) 103e108, https://doi.org/10.3303/CET1647018 [2] F Fajaroh, H Setyawan, W Widiyastuti, S Winardi, Synthesis of magnetite nanoparticles by surfactant-free electrochemical method in an aqueous system, Adv Powder Technol 23 (2012) 328e333, https://doi.org/10.1016/ j.apt.2011.04.007 [3] W Wang, B Tang, B Ju, S Zhang, Size-controlled synthesis of waterdispersible superparamagnetic Fe3O4 nanoclusters and their magnetic responsiveness, R Soc Chem (2015) 75292e75299, https://doi.org/ 10.1039/c5ra14354c [4] R.J Harrison, R.E Dunin-Borkowski, A Putnis, Direct imaging of nanoscale magnetic interactions in minerals, Proc Natl Acad Sci U S A 99 (2002) 16556e16561, https://doi.org/10.1073/pnas.262514499 [5] A Akbarzadeh, M Samiei, S Davaran, Magnetic nanoparticles: preparation, physical properties, and applications in biomedicine, Nanoscale Res Lett (2012) 1e13, https://doi.org/10.1186/1556-276X-7-144 [6] X Liu, Z Zhong, Y Tang, B Liang, Review on the synthesis and applications of Fe3O4 nanomaterials, J Nanomater 2013 (2013) 1e7, https://doi.org/10.1155/ 2013/902538 [7] M.C Mascolo, Y Pei, T.A Ring, Room temperature Co-Precipitation synthesis of magnetite nanoparticles in a large ph window with different bases, Mater Basel (2013) 5549e5567, https://doi.org/10.3390/ma6125549 [8] A.J Giustini, A.A Petryk, S.M Cassim, J.A Tate, I Baker, P.J Hoopes, Magnetic nanoparticle hyperthermia in cancer treatment, Nano Life (2010), https:// doi.org/10.1142/S1793984410000067.MAGNETIC [9] J Sung Lee, J Myung Cha, H Young Yoon, J.-K Lee, Y Keun Kim, Magnetic multi-granule nanoclusters: a model system that exhibits universal size effect of magnetic coercivity, Sci Rep (2015) 12135, https://doi.org/10.1038/ srep12135 , F.C Fonseca, M.P Morales, Static and dynamic magnetic [10] G.F Goya, T.S Berquo properties of spherical magnetite nanoparticles, J Appl Phys 94 (2003) 3520e3528, https://doi.org/10.1063/1.1599959 [11] M.L Rivas-S anchez, L.M Alva-Valdivia, J Arenas-Alatorre, J Urrutia-Fucugauchi, M Perrin, A Goguitchaichvili, M Ruiz-Sandoval, M.A Ramos Molina, Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties, Earth, Planets Sp 61 (2009) 151e160, https://doi.org/ 10.1186/BF03352895 [12] J Ge, Y Hu, M Biasini, W.P Beyermann, Y Yin, Superparamagnetic magnetite colloidal nanocrystal clusters, Angew Chem Int Ed 46 (2007) 4342e4345, https://doi.org/10.1002/anie.200700197 [13] T.Q Bui, H.T Tran, Utrasonically assisted co-precipitation synthesis of magnetite and silica coated by microemulsion method, J Sci Technol 51 (2013) 200e204 [14] T.Q Bui, S.N.C Ton, Study of enhancing co-precipitation method in synthesis of magnetite nanoparticles with ultrasonic-based assistance, Hue Univ J Sci 126 (2017) 29e36, https://doi.org/10.26459/hueuni-jns.v126i1C.4216 [15] C Cheng, Y Wen, X Xu, H Gu, Tunable synthesis of carboxyl-functionalized magnetite nanocrystal clusters with uniform size, J Mater Chem 19 (2009) 8782e8788, https://doi.org/10.1039/b910832g [16] P Vikesland, R Rebodos, J.-Y Bottero, J Rose, A Masion, Aggregation and sedimentation of magnetite nanoparticle clusters, Environ Sci Nano (2016) 567e577, https://doi.org/10.1039/C5EN00155B €ße und der inneren Struktur von Kolloid[17] P Scherrer, Bestimmung der Gro €ntgenstrahlen, Nachrichten von Der Gesellschaft Der teilchen mittels Ro €ttingen, Math Kl (1918) 98e100 http://eudml.org/ Wissenschaften Zu Go doc/59018 [18] A.L Patterson, The Scherrer formula for X-ray particle size determination, Phys Rev 56 (1939) 978e981, https://doi.org/10.1103/PhysRev.56.978 [19] E Karao, A Baykal, H Erdemi, L Alpsoy, H Sozeri, Synthesis and characterization of DL-thioctic acid (DLTA)eFe3O4 nanocomposite, J Alloys Compd 509 (2011) 9218e9225, https://doi.org/10.1016/j.jallcom.2011.06.118 [20] B Unal, M.S Toprak, Z Durmus, H Sozeri, A Baykal, Synthesis, structural and conductivity characterization of alginic acid-Fe3O4 nanocomposite, J Nanopart Res 12 (2010) 3039e3048, https://doi.org/10.1007/s11051-010-9898-1 [21] B Unal, Z Durmus, H Kavas, A Baykal, M.S Toprak, Synthesis, conductivity and dielectric characterization of salicylic acid-Fe3O4 nanocomposite, Mater Chem Phys 123 (2010) 184e190, https://doi.org/10.1016/j.matchemphys 2010.03.080 [22] V.A Hiremath, A Venkataraman, Dielectric, electrical and infrared studies of g-Fe2O3 prepared by combustion method, 26 (2003) 391e396 doi:https:// doi.org/10.1007/BF02711182 [23] B Maddah, J Shamsi, Extraction and preconcentration of trace amounts of diazinon and fenitrothion from environmental water by magnetite 112 [24] [25] [26] [27] T.Q Bui et al / Journal of Science: Advanced Materials and Devices (2018) 107e112 octadecylsilane nanoparticles, J Chromatogr A 1256 (2012) 40e45, https:// doi.org/10.1016/j.chroma.2012.07.085 F.A Miller, C.H Wilkins, Infrared spectra and characteristic frequencies of inorganic ions, Anal Chem 24 (1952) 1253e1294, https://doi.org/10.1021/ ac60068a007 L Blaney, Magnetite (Fe3O4): properties, synthesis, and applications, Lehigh Rev 15 (2007) 5e55, https://doi.org/10.1016/j.ceramint.2011.11.027 M.A Hegazy, A.M.A El-hameed, Characterization of CdSe-nanocrystals used in semiconductors for aerospace applications: production and optical properties, NRIAG J Astron Geophys (2014) 82e87, https://doi.org/10.1016/ j.nrjag.2014.05.002 A.K Singh, Advanced X-ray Techniques in Research and Industry, IOS Press, 2005 [28] K.S Suslick, Ultrasound in synthesis, in: Mod Synth Methods 1986, Urbana, 1986, pp 1e60, https://doi.org/10.1007/978-3-642-82805-8_1 [29] H Xu, B.W Zeiger, K.S Suslick, Sonochemical synthesis of nanomaterials, Chem Soc Rev 42 (2013) 2555e2567, https://doi.org/10.1039/c2cs35282f [30] G Cao, Nanostructures & Nanomaterials: Synthesis, Properties & Application, first ed., Imperial College Press, London, 2004 [31] W McCabe, J Smith, P Harriott, Unit Operations of Chemical Engineering, fifth ed., McGraw-Hill, New York, 1993 [32] Z Zhang, F Zhou, E.J Lavernia, On the analysis of grain size in bulk nanocrystalline materials via X-ray diffraction, Metall Mater Trans a-Physical Metall Mater Sci 34A (2003) 1349e1355, https://doi.org/10.1007/s11661-003-0246-2 € Ozdemir, € [33] D.J Dunlop, O Rock Magnetism: Fundamentals and Frontiers, first ed., Cambridge University Press, Cambridge, 1997 ... moments Conclusion This study showed the dependence of the magnetic responsiveness on particle size of magnetite nanoparticles synthesised by co- precipitation and solvothermal methods, and revealed... secondary structure of the magnetite material The reasonable correspondence of M-01 particle sizes, deduced from XRD data and recognised from TEM images, could be explained by the procedure of. .. synthesis of magnetite and silica coated by microemulsion method, J Sci Technol 51 (2013) 200e204 [14] T.Q Bui, S.N.C Ton, Study of enhancing co- precipitation method in synthesis of magnetite nanoparticles