Magnetite nanoparticles (Fe₃O₄ NPs) performed by the co-precipitation and green synthesis processes

1 Introduction

Nanotechnology is the ability to measure, manipulate, and manufacture things of atomic or molecular scale, usually between 1 and 100 nm. The significant characteristic of nanomaterials is the primary reason for their extensive use in various fields such as mechanics, optics, electronics, biotechnology, microbiology, environmental cleanup, medicine, engineering, and material science [1]. The production methods of nanoparticles (NPs) involve chemical and biological synthesis [1,2]. The green method approach has significant benefits over conventional physicochemical synthesis, including the synthesis of NPs with precisely defined sizes and the use of biological metabolites that are both eco-friendly and cost-effective [3].

Green nanotechnology production processes operate under safe and environmentally friendly conditions, without the need for toxic chemicals [4]. Iron NPs have garnered significant interest due to their small particle size, surface characteristics, low toxicity, strong magnetism, and numerous applications in various scientific fields. These applications span a wide range of areas, including medicine, food, agriculture, cosmetics, paints, textiles, and wastewater treatment [4,5,6].

Stable iron-polyphenol complex NPs (Fe-P NPs) was produced using Eucalyptus leaf extract [7]. Similarly, Zhiqiang utilized three different plants, namely, Eucalyptus tereticornis, Melaleuca nesophila, and Rosmarinus officinalis, to create Fe–P NPs ranging in sizes from 50 to 80 nm [8]. Fe NPs of 60 nm were generated using the methanolic grape leaf extract [9]. It is important to point out that the objective of this work is not to show polyphenols as an invention that has not been cited before, but the novelty of this work is to characterize synthesized NPs using a plant type (Trigonella foenum-graecum), very rich in polyphenols, which makes it possible to obtain NPs products whose properties are researched in new optimal conditions. To the best of our knowledge, this is the first comparative study addressing the influence of Fe₃O₄ NP synthesis using different methods on physicochemical and morphological properties of the nanomaterial. The current investigation's objective is to refine magnetite NPs (Fe₃O₄ NPs) made by co-precipitation and green synthesis techniques. Here, we provide optimal conditions for the synthesis and the characterization of the NP-based fenugreek plant extract. Nanotechnology represents a new and enabling platform that promises to provide a broad range of novel uses and improved technologies for many applications. NP applications is gaining popularity in the worldwide scientific community. It is one of such promising technologies and has a consistent margin of progression compared to the well-known commercialized processes, which are considered to be technologically mature and therefore have very little space for major performance improvements. Products are relatively new, it is a low-cost process, and they are investigated worldwide. It has low-energy requirements, while operating at different temperature. The importance of this green process for the synthesis of NPs is manifested not only at the level of environmental protection by limiting the use of chemicals but also essentially by the use of reagents that make it possible to obtain NPs of very specific optical and structural properties.

2 Results and discussion

The structural characteristics of the synthesized NPs were studied using X-ray diffractometer, which is employed to determine the Fe₃O₄ NP structure phase. As shown in Figure 1, peaks at 30.1°, 35.7°, 43.3°, 53.9°, 57.5°, and 63.0° were visible in the X-ray diffraction (XRD) diffractogram of Fe₃O₄ NPs. These values correspond to miller indices of 220, 311, 400, 422, and 511, respectively. This diffraction pattern indicates that the Fe₃O₄ NPs have a spinel structure [10]. The X-ray diffraction pattern of obtained Fe₃O₄ NPs demonstrates distinct line broadening of the X-ray diffraction peaks, suggesting that the obtained powder were in the nanometric size. Different characteristic Bragg reflection pattern peaks were observed and assigned to the (220), (311), (400), (511), and (440); further, these patterns were also comparable to the standard magnetite XRD patterns (JCPDS card no. 01-075-1609) for Fe₃O₄ NPs synthesized by the green method (Figure 2a). In addition, these patterns were comparable to the standard magnetite XRD patterns (JCPDS card no. 01-075-0033) for Fe₃O₄ NPs synthesized by the coprecipitation method (Figure 2b). The wide-angle XRD pattern allowed for easy identification of peaks that corresponded to the pure cubic phase of the synthesized material, allowing for the observation of its purity. However, no other peaks (impurity peaks) were seen, which supported the successful synthesis of high-purity crystalline Fe₃O₄ NPs using T. foenum-graecum leaves extract. The size of the magnetite NPs was calculated by the Debye–Scherer equation (Eq. 1) using the more intense peak in the XRD graph. The NP size was found to be approximately 10 and 30 nm, respectively, from Fe₃O₄ NPs synthesized by the green and coprecipitation methods.

Figure 1

Green synthesis of Fe₃O₄ nanoparticles (Fe₃O₄ NPs2) using T. foenum-graecum.

Figure 2

X-ray diffraction of Fe₃O₄ NPs2 (a) and Fe₃O₄ NPs1 (b).

Figure 3 displays the Fourier-transform infrared spectroscopy (FTIR) spectrum of Fe₃O₄ NPs. The spectrum showed a broad band at 3,429 cm⁻¹, which indicates the presence of N–H and O–H stretching vibrations from protein amides and starch fiber. The absorption broad band at 1,566 and 1,644 cm⁻¹ implies the presence of carbonyl (C═O) stretching of amide I, while 1,456 cm⁻¹ shows the C–H vibration. The sharp band at 1,355 cm⁻¹ is due to the C–N stretching or the O–H bending vibration. The presence of Fe NPs can be confirmed by the strong absorption band at 561 cm⁻¹ [5].

Figure 3

Fourier transforms infrared spectrum of Fe₃O₄ NPs2 (a) and Fe₃O₄ NPs1 (b).

Scanning electron microscope (SEM) analysis revealed the great morphology of nanostructures. The microscopic analysis confirms the formation of iron oxide NPs, which was found to be spherical in shape (Figure 4). Some of Fe₃O₄ NPs were agglomerated, confirmed by the SEM image.

Figure 4

Scanning electronic microscopy image of Fe₃O₄ NPs2 (a) and Fe₃O₄ NPs1 (b).

The particle size quantification of Fe₃O₄ NPs stock suspension was determined by dynamic light scattering (DLS) using a Malvern (zetasizer nano-ZS) particle analyzer. The analysis demonstrated an average particle size of 6 and 43 nm in the 50 µg L⁻¹ stock, respectively, for Fe₃O₄ NPs synthesized by green and coprecipitation methods (Figure 5). The formation of agglomerates leads to a reduction of the total surface of particles [11].

Figure 5

DLS size distribution of Fe₃O₄ NPs2 (a) and Fe₃O₄ NPs1 (b).

3 Conclusion

We created Fe₃O₄ NPs using both co-precipitation techniques (Fe₃O₄ NPs1) and biological synthesis (Fe₃O₄ NPs2). Different properties, mostly related to the size of the particles, are revealed by the characterization of these NPs. NPs with a size of approximately 6 nm can be synthesized using the biological method. It is approximately 46 nm when using the chemical co-precipitation process. These results are very encouraging for an environmental perspective, as the biological synthesis allows for the production of high-quality NPs with a reduced chemical requirement.

Experimental