Elegant Explorations of Ionic Liquids in the Expeditious Synthesis of Fe3O4 Nanoparticles

Introduction

Transition metal nanoparticles are critical for a wide range of potential applications in science and industry, including sensors and catalysts.^1-5 Several physical and chemical approaches were used to form metal oxide nanoparticles of Ru, Rh, Ir, Mn, Fe, Zn, Cu, and Co.^6-11 Magnetite NPs,an important family of nanoparticles, has been extensively used as a catalyst,¹²adsorbent,¹³ and sensor.¹⁴As a result, regulated synthesis, as well as the generation of stabilized metal nanoparticles, is critical.¹⁵ To develop new methods an era of green synthesis approach is gaining great attention in upcoming research and development on materials science and technology. Ionic liquids (ILs) have been increasingly used and researched in recent years as reaction media, for catalysis,¹⁶ biocompatible protein stabilization,¹⁷ surfactant,¹⁸ environmentally friendly chemical processes,¹⁹ micro-extraction technique,²⁰ electrochemical non-enzymatic detection of sulfite in food samples,²¹ dye-sensitized solar cells,²² in biomedical and pharmaceutical applications²³ and so on. Furthermore because of their particular physical and chemical properties, they can be used to synthesize nanoparticles²⁴ and to form colloidal nanocrystals (NCs).²⁵Because their electrostatic stability, ILs have the potential to be used in the synthesis of inorganic nanomaterials²⁶ and nanoflakes.²⁷ Metal oxide nanoparticles are protected from electrostatic charge by the strong polarity, high dielectric constant, and supramolecular network of ionic liquids,according to the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory. As a result, imidazolium ionic liquids ILs were utilized as an electrostatic stabilizer, reaction solvent and capping agent for various nano-materials to regulate their size or shape. Metal Nanoparticles (MNPs) in ILs were synthesized using various methods. ^28-29 ILs were employed to effectively control metal oxide nanoparticle shape, avoid inter-particle aggregation, and optimize particle production. The easiest and most efficient way to create metal oxide nanoparticles at the desired level is with Room-temperature ionic liquids (RTILs) assistance. Ionic liquids have the ability to stabilize metal oxide nanoparticles.^{30, 31, 32, 33}. According to Dupontet al³⁴, imidazolium cations present in ILs form a protective layer that stabilizes NP surfaces by providing steric and electronic protection against aggregation. Herein, we describe a smart and aptly developed incorporation of ILs (1-Propyl-3-methylimidazolium bromide [C₃mim][Br], 1-Butyl-3-methylimidazolium bromide [C₄mim][Br] and 1-Hexyl-3-methylimidazolium bromide [C₆mim][Br]) and unconventional methods of synthesis offers additional value to be drawn from the broad matrix ofavailable property combinations. These supramolecular liquids therefore facilitate new and rapid universal manufacturing techniques that provide solutions to the presentcomplications associated with nano-manufacturing, and beyond that will open completely new horizons and possibilities forcontrolling the growth and assembly of nanostructures.

Experimental section

Materials

1-methyl imidazole, 1-propyl bromide, 1-butyl bromide, 1-hexyl bromide purchased from Sigma Aldrich, FeSO₄.7H₂O, FeCl₃.6H₂O and NaOH purchased fromAvra Chemicals. All chemicals and solvents were obtained from commercial sources and were used without further purification.

Methods

FT-IR

FT-IR spectrum of synthesized metal oxide NPs was observed by Perkin Elmer-Spectrum RX-IFTIR,

XRD

Crystallite diffraction peaks of synthesized metal NPs was observed by Powder X-ray Diffractometer (X’Pert Pro, PANalytical Netherlands),

FE-SEM

Morphology of the synthesized metal oxide NPs was studied by Field Emission Scanning Electron Microscope (SU 8010 Series, Hitachi, Japan).

Synthesis of imidazolium ionic liquids

Through a water condenser, a stirred mixture of 1-methyl imidazole (30mmol, 2.46g) and an alkyl halide (30mmol, (propyl bromide, 03.68g), (butyl bromide, 4.1106g), (hexyl bromide, 4.65g)) was slowly added to the molten tetrabutylammonium bromide (TBAB). The reaction mass was extracted with ethylmethyl ketone (50 ml x 5) after the reaction mixture had finished adding all the ingredients. The reaction mass quickly split into two immiscible phases after being added to. These phases were then separated using a separating funnel. In order to get tetrabutylammonium bromide for reusing, the ethylmethyl ketone was distilled off after the ionic liquid phase had been transported to a vacuum oven for drying.³⁵

Scheme 1: Synthesis of 1-alkyl-3-methylimidazolium bromides Click here to View Scheme

Synthesis of Magnetite (Fe₃O₄) nanoparticles using ionic liquid

The magnetite nanoparticles were prepared via the chemical co-precipitation method by the following 0.11 g of FeSO₄.7H₂O and 0.22 g of FeCl₃. 6H₂O, with the molar ratio of ferric ion to ferrous ion in the solution of 2:1, were dissolved in 30ml of deionized water. Then 4mmol IL and 1N NaOH were added to the solution under vigorous stirring at 80℃. The solution color changed from yellow-orange to black rapidly. The magnetite nanoparticles were filtered and thoroughly washed with deionized water several times. Finally, Fe₃O₄ samples were dried in oven at 150℃ for 2 h.

Scheme 2: Synthesis of Fe3O4 nanoparticles using ionic liquid. Click here to View Scheme

Results and discussion

Our investigations began with the synthesis, characterization of ionic liquids, and iron oxide nano-particles using modern analytical characterization methods such as X-ray, scanning electron microscopy, and FT-IR. The results obtained for the characterization of the iron oxide nano-particles are discussed briefly in the following sections.

Optimization of reaction parameters

In this study, certain imidazolium ionic liquids were used in order to synthesize iron metal oxide nanoparticles.

Table 1: optimization of reaction parameters.

NPs	Entry	NaOH  (M)	FeSO4. 7H2O (g)	FeCl3. 6H2O (g)	IL (mmol)	Temp. (ºC)	Yield (g)	% Practical Yield
Fe3O4	Without ILs
	1	1M	0.11	0.22	0	80	0.08	87.9
	1-Propyl-3-methylimidazolium bromide [C3mim][Br]
	2	1M	0.11	0.22	1	80	0.072	79.1
	3	1M	0.11	0.22	2	80	0.078	85.7
	4	1M	0.11	0.22	4	80	0.081	89.0
	5	1M	0.11	0.22	6	80	0.068	74.7
	1-Butyl-3-methylimidazolium bromide [C4mim][Br]
	6	1M	0.11	0.22	1	80	0.068	74.7
	7	1M	0.11	0.22	2	80	0.0789	86.7
	8	1M	0.11	0.22	4	80	0.089	97.8
	9	1M	0.11	0.22	6	80	0.078	85.7
	1-Hexyl-3-methylimidazolium bromide [C6mim][Br]
	10	1M	0.11	0.22	1	80	0.0659	72.4
	11	1M	0.11	0.22	2	80	0.072	79.1
	12	1M	0.11	0.22	4	80	0.0841	92.4
	13	1M	0.11	0.22	6	80	0.0831	91.3

 

The closure scrutiny of Table 1 reveals that the concentration of ionic liquid plays a subtle role in the synthesis of metal oxide nanoparticles. The experimental data in hand envisaged that the practical yield of the resulting nanoparticles is to be increased up to 4mmol concentration of IL but there is no significant impact after 4mmol was found. Therefore, 4mmol IL concentration is chosen for metal oxide nanoparticle synthesis.

Table 2: Effect of Temperature on the yield of the reaction

NPs	Entry	NaOH (M)	FeSO4.7H2O (g)	FeCl3.6H2O (g)	IL (mmol)	Temp. (ºC)	Yield (g)	% Practical Yield
Fe3O4	Without ILs
	1	1M	0.11	0.22	0	30	0.05	54.9
	2	1M	0.11	0.22	0	40	0.052	57.1
	3	1M	0.11	0.22	0	60	0.062	68.1
	4	1M	0.11	0.22	0	80	0.08	87.9
	5	1M	0.11	0.22	0	100	0.078	85.7
	1-Propyl-3-methylimidazolium bromide [C3mim][Br]
	6	1M	0.11	0.22	1	30	0.038	41.7
	7	1M	0.11	0.22	1	40	0.057	62.6
	8	1M	0.11	0.22	1	60	0.068	74.7
	9	1M	0.11	0.22	1	80	0.072	79.1
	10	1M	0.11	0.22	1	100	0.072	79.1
	1-Butyl-3-methylimidazolium bromide [C4mim][Br]
	11	1M	0.11	0.22	1	30	0.045	49.4
	12	1M	0.11	0.22	1	40	0.052	57.1
	13	1M	0.11	0.22	1	60	0.062	68.1
	14	1M	0.11	0.22	1	80	0.068	74.7
	15	1M	0.11	0.22	1	100	0.067	73.6
	1-Hexyl-3-methylimidazolium bromide [C6mim][Br]
	16	1M	0.11	0.22	1	30	0.043	47.2
	17	1M	0.11	0.22	1	40	0.049	53.8
	18	1M	0.11	0.22	1	60	0.052	57.1
	19	1M	0.11	0.22	1	80	0.0659	72.4
	20	1M	0.11	0.22	1	100	0.0659	72.4

 

In the next,effect of temperature on the magnitude of the reaction has been advanced by performing certain experiments and the experimental data is tabulated in Table 2. The data obtained manifests that 80℃is the most suitable condition of temperature to facilitate the synthesis of Fe₃O₄ NPs.

FT-IR analysis of Fe₃O₄ NPs:

FT-IR spectroscopy was used to identify the NPs generated through Co-precipitation employing Fe²⁺/Fe³⁺precursors in an ionic liquid. In fig.1 (d) the major phase of the synthesized particles, magnetite, was validated at low frequencies by a prominent absorption band that was centered between 480 and 620 cm^-1, with the peak assigned to the vibration and torsional modes of the Fe-O bonds. Broad peaks in the spectrum that appeared around 1636 and 3474 cm^-1were attributed, respectively, to H₂O’s stretching and bending vibrations of the -OH bond. Due to the aliphatic C-H of the methylene in the ionic liquid, there are stretching vibrations at 2850-2920 cm^-1.^36-37

Figure 1: FT-IR spectrum of Fe3O4 NPs, fig (a) Fe3O4 NPs synthesized without ionic liquid, fig (b)with [C3mim][Br] ionic liquid, fig (c) with [C4mim][Br] ionic liquid and fig (d)with [C6mim][Br]ionic liquid. Click here to View Figure

XRD analysis of Fe₃O₄ NPs:

The crystalline structure of the produced Fe₃O₄ NPs has been confirmed by the XRD investigation. Diffraction peaks at 30.49, 35.85, 43.52, 57.45, and 63.07 were matched to 220, 311, 400,422,511 and 440 planes respectively, in the Fe₃O₄XRD pattern shown in Figure 2 [fig.b] The JCPDS Card 01-071-6336 (Joint Committee on Powder Diffraction Standards) and the diffraction peaks are in good agreement, which amply demonstrates that the produced Fe₃O₄ NPs are crystalline in nature.³⁸The Debye Scherrer equation was used to get the average crystallite size.

D = Kλ / β Cos θ

Where, D is average particle size (nm), K is constant as equal to 0.94, λ is wavelength of X-ray radiation. β- is full-width at half maximum (FWHM) of peak in radians and θ is diffraction angle (degree).  The calculated average crystallite size of green synthesized Fe₃O₄ NPs is found to be in the range of 11-13 nm.

Figure 2: XRD spectrum of Fe3O4 NPs, fig (a)Fe3O4 NPs synthesized without ionic liquid, fig (b)with [C3mim][Br] ionic liquid, fig (c)with [C4mim][Br] ionic liquid, fig (d)with [C6mim] Br] ionic liquid. Click here to View Figure

Morphology ofFe₃O₄ nanoparticles

Figure 3 shows SEM pictures of metal oxide nanoparticles made with various imidazolium ionic solutions. Fe₃O₄ nanoparticles are all sphere-like formations, as can be seen. While Fe₃O₄ nanoparticles prepared with imidazolium ionic liquid exhibit very moderate dispersion (Figs. 3b, 3c, and 3d), those prepared without ionic liquid exhibit significant agglomeration (Fig. 3a). Therefore, [C₆mim][Br], one of the three imidazolium ionic liquids used in the study, could offer both steric and electrostatic stability. It reduces the possibility of close particle interactions producing big particle sizes.³⁹

Figure 3: FE-SEM images of Fe3O4 nanoparticles. Click here to View Figure

Conclusion

In conclusion, we have shown a simple and efficient co-precipitation technique for the one step production of Fe₃O₄ NPs utilizing imidazolium ionic liquid. Our findings show that employing ionic liquid during synthesis resulted in lower particle sizes than doing so without.

Conflict of Interest

The authors declare that there is no conflict of interest related to this article.

Acknowledgement

The authors are thankful to the Principal of Arts and Science College, Bhalod and Bhusawal Arts, Science and P.O. Nahata Commerce College, Bhusawal, for the facility given for the present research work.

References

1. Verma, C.; Ebenso, E. E.; Quraishi, M. A. J. Mol. Liq.2018, doi:10.1016/j.molliq.2018.12.063
   CrossRef
2. Ojha, N. K.; Zyryanov, G. V.; Majee, A., Charushin, V. N.; Chupakhin, O. N.; Santra, S. Coord. Chem. Rev.2017, 353, 1-57, doi:10.1016/j.ccr.2017.10.004
   CrossRef
3. Migowski, P.; Dupont, J.  A. Eur. J.2006, 13(1), 32–39. doi:10.1002/chem.200601438 
   CrossRef
4. Cheng, T.; Zhang, D.; Li, H.; Liu, G. Green Chem.2014, 16(7), 3401-3427. doi:10.1039/c4gc00458b 
   CrossRef
5. Bhirud, S.; Sarode, C. H.; Gupta, G. R.; Chaudhari, G. R. Curr. Nanomater.2023, DOI: 10.2174/2405461508666230508124607
   CrossRef
6. Christian Vollmer, C.; Redel, E.; Shandi, K. A.; Thomann, R.; Manyar, H.; Hardacre, C.; Janiak, C. Chem. Eur. J.2010, 16, 3849 -3858
   CrossRef
7. Bussamara, R.; Melo, W. W. M.; Scholten, J. D.; Migowski, P.; Marin, G.; Zapata,. Machado, J.M.G. Teixeira, S.R.; Novakb, M. A.; Dupont, J. Dalton Trans.2013, 42, 14473-14479
   CrossRef
8. Sharma, R. K.; Dutta, S.; Sharma, S.; Zboril, R.; Varma, R. S.; Gawande, M. B. Green Chem.2016, 18(11), 3184-3209. doi:10.1039/c6gc00864j 
   CrossRef
9. Rajiv Gandhi, R.; Gowri, S.; Suresh, J.; Sundrarajan, M. J. Mater. Sci. Technol.2013, 29(6), 533-538. doi:10.1016/j.jmst.2013.03.007
   CrossRef
10. Amaliyah, S.; Pangesti, D. P.; Masruri, M.; Sabarudin, A.; Sumitro, S. B. Heliyon2020, 6(8), e04636. doi:10.1016/j.heliyon.2020.e04636 
    CrossRef
11. Scariot, M.; Silva, D. O.; Scholten, J. D. ; Machado, G.; Teixeira, S. R.; Novak, M. A. ; Ebeling, G.; Dupont, J. Angew. Chem. Int. Ed.2008, 47, 9075-9078, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, doi: 10.1002/anie.200804200 n
    CrossRef
12. Khalifeh, R.; Naseri, V.; Rajabzadeh, M.;ChemistrySelect2020, 5(37), 11453-11462. doi:10.1002/slct.202003133 
    CrossRef
13. Venkateswarlu, S.; Yoon, M.; Kim, M. J. Chemosphere2022, 286, 131673, doi:10.1016/j.chemosphere.2021.131673 
    CrossRef
14. Mollarasouli, F.; Zor, E.; Ozcelikay, G.; Ozkan, S. A. Talanta2021, 226, 122108. doi:10.1016/j.talanta.2021.122108 
    CrossRef
15.   Sundrarajan, M.; Ramalakshmi,M. E-J Chem.2012, 9(3), 1070-1076
    CrossRef
16. Sood, K.; Saini, Y.; Thakur, K. K.;Mater. Today: Proc.2021, 81,2, 739-744, doi: org/10.1016/j.matpr.2021.04.225
    CrossRef
17. Reslan, M.; Kayser, V. 2018,10(3), 781–793. doi:10.1007/s12551-018-0407-6 
    CrossRef
18. Seoud, O. A. E.; Keppeler, N.; Malek, N. I.; Galgano, P. D.  Polymers2021, 13, 1100. https://doi.org/10.3390/polym13071100
    CrossRef
19. Nasirpour, N.; Mohammadpourfard, M.; ZeinaliHeris, S. Chem. Eng. Res. Des.2020, doi: https://doi.org/10.1016/j.cherd.2020.06.006
    CrossRef
20. Marcinkowska, R.; Konieczna, K.; Marcinkowski, L.; Namiesnik, J.; Kloskowski, A. Trends Anal. Chem.2019, 119, 115614
    CrossRef
21. Manusha, P.; Senthilkumar, S. J. Mol. Liq.2020, 301,112412
    CrossRef
22. Tseng, S. K.; Wang, R. H.; Wu, J. L.; Jyothibasu, J. P.; Wang, T. L.; Chu, C. Y.; Lee, R. H.  Polymer 2020, 210, 123074, https://doi.org/10.1016/j.polymer.2020.123074
    CrossRef
23. Egorova, K. S.; Ananikov, V. P. J. Mol. Liq.2018, 272 271-300
    CrossRef
24. Safari, J.; Zarnegar, Z.New J. Chem.2014, 38, 358-365, DOI: 10.1039/c3nj01065a
    CrossRef
25. Kamysbayev, V.; Srivastava, V.; Ludwig, N. B.; Borkiewicz, O. J.; Zhang, H.; Ilavsky, J.; Lee, B.; Chapman, K. W.; Vaikuntanathan, S.; Talapin, D. V. ACS Nano2019, 13, 5760-5770, DOI: 10.1021/acsnano.9b01292
    CrossRef
26. Hammond, O. S.; Mudring, A. V. Chem. Commun. 2022, 58, 3865, doi: 10.1039/d1cc06543b
    CrossRef
27. Liu, X.; Duan, X.; Qin, Q.; Wangc, Q.; Zheng, W. Cryst. Eng. Comm.2013, 15, 3284-3287, DOI: 10.1039/c3ce00035d
    CrossRef
28. Zwara, J.; Gawron, M. P.;Luczak, J.; Pancielejko, A.; Lisowski, W.; Trykowski, G.; Medynska, A. Z.; Grabowska, E. Int. J. Hydrog. Energy 2019, 44, 26308e26321
    CrossRef
29. Mudhoo, A.; Kumar G. Biochem. Eng. J.2018, https://doi.org/10.1016/ j.bej.2018.07.018
    CrossRef
30. Faizan, M.; Ahmed, R.; Ali, H. M. J. Taiwan Inst. Chem. Eng. 2021,1-33
31. Wegner, S.; Janiak, C. Top. Curr. Chem. (Z)2017, 375, 65, doi: org/10.1007/s41061-017-0148-1
    CrossRef
32. Cao, H.; Hu, Y.; Xu, W.; Wang, Y.; Guo, X. J. Mol. Liq.2020, 319, 114354, doi.org/10.1016/j.molliq.2020.114354
    CrossRef
33. Zwara, J.; Paszkiewicz-Gawron, M.; Łuczak, J.; Pancielejko, A.; Lisowski, W.; Trykowski, G.; Zaleska-Medynska, A.; Grabowska, E.;Int. J. Hydrog. Energy2019,44, 26308-26321, https://doi.org/10.1016/ j.ijhydene.2019.08.094
    CrossRef
34. Dupont, J.; Fonseca, G. S.; Umpierre, A. P.; Fichtner, P. F. P.; Teixeira, S. R. Acc. Chem. Res.2011,44,1223-1231
    CrossRef
35. Gupta, G. R.; Chaudhari, G. R.; Tomar, P. A.; Waghulde, G. P.; Patil, K. J. Asian J Chem. 2012, 24(10), 4675-4678
36. Chaki, S. H.; Malek, T. J.; Chaudhary, M. D.; Tailor, J. P.; Deshpande, M. P.Adv. Nat. Sci: Nanosci. Nanotechnol.2015, 6, 035009, doi:10.1088/2043-6262/6/3/035009
    CrossRef
37. Petcharoena, K.; Sirivat, A.; Mater. Sci. and Eng. B 2012, 177, 421-427, doi:10.1016/j.mseb.2012.01.003
    CrossRef
38. Sun,X.; Xu, L.;Jiang, W.; Xuan, Y.; Lu, W.; Li, Z.; Yang, S.; Gu, Z.Environ. Sci. and Pollution Res.2020,Springer-Verlag GmbH Germany, https://doi.org/10.1007/s11356-020-10541-5
    CrossRef
39. Sun, K.; Sun, C.; Tang, S. Cryst. Eng. Comm.2015, DOI: 10.1039/C5CE02095F
    CrossRef

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