Open access peer-reviewed chapter

Synthesis and Characterization of NanoBismuth Ferrites Ceramics

Written By

Sheela Devi, Venus Dillu and Mekonnen Tefera Kebede

Submitted: 08 March 2022 Reviewed: 01 April 2022 Published: 09 July 2022

DOI: 10.5772/intechopen.104777

From the Edited Volume

Smart and Advanced Ceramic Materials and Applications

Edited by Mohsen Mhadhbi

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Multiferroic nanomaterials bear draw attention plenty consideration on account of the mixture of two or more determinants, in the way that ferroelectricity, ferromagnetism, and ferroelasticity, giving an expansive range of professional, depressed capacity, environmentally intimate request. Nano-bismuth ferrite (BiFeO3, BFO) exhibits two together (anti) ferromagnetic and ferroelectric real estate at room temperature. Therefore, it bears risk a very influential part fashionable the multiferroic foundation. This review focuses ahead of the progress of nano-BFO objects, containing unification, facial characteristics, structures, and potential uses of multiferroic order accompanying novel functions. Hopes and danger happen all investigated and made clear. We hope that this review will be a part of a review and encourage more research workers to win accompanying nano-BFO results.


  • Nano bismuth ferrites ceramics
  • properties
  • characterization
  • multifunctional device

1. Introduction

Nanomaterials are materials with length scales ranging from 1 to 100 nm. The properties of materials change dramatically on the nanoscale when compared to their bulk counterparts. The physiochemical properties of these materials are very sensitive to size and shape, resulting in properties that are completely different when studied in bulk materials. Because of their high surface-to-volume ratio, nanomaterials have a distinct set of properties. At both normal and high temperatures, nano-ceramic materials exhibit excellent refractory properties, chemical resistance, mechanical resistance, and hardness [1] BiFeO3, BFO is an exciting one-phase application that has focused on multidisciplinary device applications due to its unique properties, including Currie high temperature of ferroelectricity (TC = 1103 k), high Neel temperature for antiferromagnetism (TN = 643 k), lead-free piezoelectricity, and impressive photoelectric performance in the visible area [1, 2]. These features make BiFeO3 a promising candidate, especially in ferroelectrics, magnetic, piezoelectrics, Photovoltaic devices, and photocatalytic function. In addition, the combination of these structures has the potential to provide the next generation of electrical appliances with a wide range of functions. The BiFeO3 investigation began in the 1950s. In the Ramesh group (24) in 2003, the discovery of a large polarization of fossils, 15 times larger than previously obtained by large samples (6.1 μC/cm2), combined with the strong ferromagnetism seen in small BiFeO3 films, and increased studies. In this field and several other investigations in bulk, a thin film and forms with a BiFeO3 structure have been made since then. Although BFO has a spiral spin formation with a periodicity of 62 nm as a single type of G-type antiferromagnetic material, this combination of the soft magnetoelectric liner makes it difficult to use for many functional devices [3]. These days, it has been found that BFO nanoparticles exhibit strong ferromagnetism due to their magnitude of less than 62 nm [4]. As a result, the successful development of magnetoelectric integration in nanosized BFO has played a significant role in microelectronic devices [5, 6, 7]. The importance of the semiconductor circuit combined science and technology have resulted in the feature size of microelectronic devices being reduced to nanoscale magnitude. BFO material features nanoscale novels different from most of their counterparts and films. Knowing the impact of BFO on the nanoscale is essential in promoting the development of new electronic devices. The controlled integration of nano-BFO nanostructures such as nanowires, nanotubes, nano-powders, and arrays has made great effort due to size-dependent effects in structure and limited size. Some gains have been made in classifying buildings. In addition, BFO nanostructures are gaining considerable attention in heterostructures and domain classification [8, 9]. This paper provides an overview of recent developments in the integration, segregation of actors, visual structures, and the potential use of the nanosized BFO. Other issues that need to be addressed in future research are also highlighted.


2. Nanoparticles

Nanoparticles are particles with dimensions ranging from 1 to 100 nm that have features not discovered in the bulk material of the likely structure [10].

2.1 Synthesis methods

BFO nanoparticles Synthesis is one of the fascinating areas of study because of its technological relevance [11]. Due to the extensive development of nano-BFOs, further research is needed to determine the best ways to make high-quality BFO nanoparticles in purity, shape, size, size distribution, stability, and particle morphology [12]. Currently, the synthesis of BFO nanoparticles has been reported using several methods such as solid-state [13], ferrite precursor [14], hydrothermal [15], sol-gel [16], and co-precipitation [17]. To date, however, there is no established method for nano BFO synthesis, and all of these synthetic methods have their advantages and disadvantages. To date, two different methods have been developed to integrate nano-BFO; another way of going down, which means to combine nanoparticles from atoms or molecules by assembling smaller ones into larger ones; another way of going up and down, which means splitting, recording, or filming a thin film or bulk material into nano sizes like significant cuts into smaller ones. The “bottom-up “method has several integration techniques: co-precipitation, thermal decomposition, hydrothermal, sol-gel, solvothermal, flame spray pyrolysis, sonochemical, vapor deposition, and microwave-assisted microemulsion, and polyol routes, the first four of which are very crowded. Although mechanical grinding and pulsed laser ablation are the most widely accepted “top-down” methods combined. Among these synthetic methods, modified polyol, sonochemical, and microwave irradiation are the most widely used methods in the modern era in synthesizing a variety of nano BFO. These integration methods have several advantages: short reaction time, soft reaction conditions, high yield, and improved selected and clean reaction compared to the other combination methods mentioned above [18]. Wu et al. so far have reported a few of these integration lines [19]. Many of these artificial lines are easily found in books; therefore, in this section, we introduce the most widely used nano BFO integration lines, address their advantages, barrier differences, and summarize current developments.

2.1.1 Sol: gel

The Sol-Gel method is an easy, popular, and kind of way to go up and down to prepare the nanoparticle. In some cases, modification of precursors usually requires metal salts or metal alkoxide solutions in nanostructures that undergo hydrolysis and condensation polymerization processes to form gels. After being released, the cells turn the jelly cells into something intended to be suppressed. Important processing features of the sol-gel process are the amount of water in the solution, the pH value of the solution, and its temperature. Blending of BFO nanoparticles by sol-gel process, Bi (NO3)3.5H2O and Fe (NO3)3.9H2O are widely used as raw materials [3, 20, 21]. As mentioned below, there are three main sol-gel processes for synthesizing BFO nanoparticle materials. Traditional technique

The most straightforward process begins by combining iron nitrate with natural solvent (2-MOE or EG) to produce a precisely reddish-black solution and stir at 70-80°C in a hot plate for several hours to obtain a soft gel. Then dry the soft gel obtained by heating to a high temperature (120-160°C) [22, 23, 24, 25]. Acid assisted sol: Gel technique

Utilizing this process, acid is added to the solution structure. Tartaric acid (C4H6O6) is a commonly used acid synthesizing BFO nanoparticles [26, 27, 28, 29]. By combining iron nitrate with natural solvents (2-MOE or EG), followed by tartaric acid (1: 1 molar ratio iron nitrate), raw material is synthesized using a tartaric acid-assisted sol-gel method. With constant stirring at 60-80°C, until the transparent sol transforms into a brown gel, other recruited acetic acids [23, 30] could also be used to make BFO nanoparticles. The preliminary preparation is similar to the tartaric acid sol-gel method in that the first precursor is made by combining iron nitrate with an organic solvent, but this time the solvent is NH3.H2O before adding acetic acid to the precursor, it is added to adjust the pH of the solution to. The solution is then shaken and stirred at 70°C in a hot magnetic plate to form a sol. The brown gel should then be dried at around 120°C for xerogel powder. In the precursor process, acetic acid acts as an unidenttate-binding agent, and organic solvent (ethylene glycol) acts as a polar-soluble solvent. During heating, Fe ions are octahedrally mixed with condensate acetic ions after adding acetic acid and ethylene glycol. At temperatures of 70°C, this is accompanied by acetate ligands and ethylene glycol. At 120°C, +the resulting esters initiate the formation of Fe-O-Bi bonds [30]. The aqueous-based sol: Gel technique

The latter method is a water-based route where no natural solvent is involved in the precursor mixing. The metal nitrate precursor system dissolves in dilute nitric acid, followed by tartaric or acetic acid [31, 32, 33, 34]. Using this line, the metal complex was created by adding acid to the aqueous metal nitrate precursor, and BFO nanoparticles began to form in the calculation after decomposition. Then after any of the routes as mentioned above, the dried gel powder is ground and heated over 400°C for pyrolysis to remove organic impurities and additional calcining around 500-600°C to obtain final nanoparticles [24, 35, 36]. In one study, after final immersion, the samples were repeatedly washed with distilled water, filtered, and dried at 80°C [36]. The sintering temperature is considered an appropriate strategy to monitor the size of BFO nanoparticles. Nanoparticle sizes can vary from less than 15 nm to more than 100 nm by incorporating sintering as low as 350–650°C [31, 34, 37]. In terms of lines (ii and iii), it proves that chelating acids (tartaric acid and citric acid) play an essential role in synthesizing nanoparticles, phases, and morphology. Using a precursor in water, it has been shown that the precipitation temperature of citric acid is less than 100oC than that of the preceding tartaric acid, taking temperatures into BFO nanoparticles that use as much citric acid as possible 350°C [34].

On the other hand, when citric acid was used as an irrigation agent and the calculation temperature was set at 600°C, it was also found that impurities such as Bi2O3 and Bi2Fe4O9 form BFO nanoparticles. On the other hand, the chelating agent of ethylene diamine tetraacetic acid (EDTA) in an aqueous precursor contributes to creating pure-phase BFO nanoparticles called the generation of heterometallic polynuclear complexes in solution [38, 39]. The addition of acrylamide and bisacrylamide monomers has also been beneficial in controlling the specific BFO size by providing a framework for the growth of nanoparticles and adjusting the size of the gel pores, respectively. However, the overgrowth of bisacrylamide may result from particles with no homogeneities and irregular shapes and contaminants [39]. The contaminants were obtained from BFO nanoparticles found in natural solvents (method (i) above) using citric acid as a chelating agent. This is due to a diametric of the citric complex and additional carbonaceous substances, which are pollutants usually created at high temperatures during the automatic combustion process [35, 40]. In comparison, tartaric acid creates bonds and iron ions with two groups of carboxyl and hydroxyl that contribute to a stable polynuclear complex. Esterification gel between metal complex and ethylene glycol [40]. The addition of acid chelating agents often influences the size of the nanoparticles. It is reported that the particle sizes of BFO nanoparticles found in citric acid at 350°C and tartaric acid at 450°C are as small as 4 nm and 12 nm, respectively [34]. The advantages of sol-gel synthesis techniques are easily accessible, energy saving, cost, and performance at low temperatures. The soluble temperature range in the sol-gel range is between 25°C and 200°C, and it is possible to combine a nano BFO with smaller size distribution and a controlled environment. These benefits and their flexibility in nano BFO synthesis make the sol-gel method very attractive. Other advantages of the sol-gel process include the necessary reagents that are simple compounds, producing nanoparticles, no special equipment required, dopants can be easily incorporated into the final product, there is little chance of assembling the particles, and the same grain structure. In addition, it is one of the most popular composite methods for controlling the formation of nanoparticles, microstructure, purity, and stability by adjusting various parameters such as sol concentration, vibration rate, and annealing temperature [41]. In addition, the combination of nanoparticles, films, and coating is the first commercial element of the sol-gel process [16]. The sol-gel synthesis method can synthesize various nanoparticles at a specified temperature range.

2.1.2 Hydrothermal

Hydrothermal is the most common chemical route to nanostructures and particularly nanoparticles metal oxide synthesis. Related to the sol-gel method, it begins with the preparation of a precursor. However, the crystallization phase occurs throughout a hydrothermal process instead of a high-temperature annealing treatment. Final nanoparticles are formed after washing, filtering, and final drying processes. Precursor preparation

The most popular hydrothermal synthesis process used for the preparation of BFO nanoparticles is the mineralizer-assisted route, in which mineralizers such as KOH (NaOH) [7, 19, 42, 43] or KNO3 [19, 44] are used for the preparation of precursors. This process allows the precursor to be conveniently prepared before hydrothermal synthesis by resolving the metal nitrates in purified water and KOH solution [45]. The aqueous precursor is produced by metal nitrates immersed in dilute nitric acid more generally than others. The method is then applied to the KOH solution for precipitation of Fe3+ and Bi3+. Precipitates are purified and cleaned to extract NO3− and K+ ions by pure water. The washed precipitates are then combined with KOH or NaOH solutions and additional KNO3 under continuous agitation [19, 44, 46]. In addition to these processes, the precursor scheme for the alteration of nanoparticles can often involve other additives, such as triethanolamine (TEA) [43] or sodium lauryl sulfate (SDS). In specific, the addition of TEA is observed to create a Fe-TEA complex that inhibits Fe hydroxide precipitation and may minimize synthesis to a maximum of 130oC [43]. Without the presence of the mineralizer, hydrothermal approaches may also be modified [45]. In hydrothermal synthesis of BiFeO3, the precursor of BiFeO3 is frequently synthesized by dissolving the metal sources, Bi and Fe nitrates (Bi(NO3)3.5H2O and Fe(NO3)3.9H2O, in deionized (DI) water or citric acid. The metal and citric acid molar ratio is equal to 1:1 ratio. Then, NH3 solution is added to neutralize the unreacted citric acid and change the pH to~9 [45]. Using this updated mineralizer-free method, the dried powder is eventually calcined at 350°C for 6 hr. to extract the final nanoparticles, which is an extremely phase-pure BFO with an average particle size of 55 nm. Hydrothermal reaction

The solution would be placed in a hydrothermal Teflon linear autoclave at 150°C-220°C for 5–20 hours [19, 47] until the precursor was collected. The autoclave would then be naturally cooled to room temperature, the precipitate collected filtered, and cleaned with deionized water (and 10% acetic acid) to eliminate any soluble salts. Finally, the nanoparticles are obtained by drying the wet samples at 70-160°C for a few hours [19, 44]. A dissolution-crystallization process is assumed to be a synthesis of the BFO Phase by the hydrothermal method. First, Bi3+ and Fe3+ ions are converted into Fe (OH)3 and Bi (OH)3 hydroxides and later, under hydrothermal conditions, dissolved in a precursor of alkaline mineralizer (KOH, NaOH, LiOH). When the concentration of ions in the alkaline solution reaches the saturation stage, the BFO phase begins to nucleate, followed by crystal formation, and precipitates the supersaturated hydrothermal fluid [19, 48, 49]. BFO particle size and morphology rely on nucleation and crystal growth rates, which are in turn influenced by the degree of supersaturation. The subsequent strong nucleation but low growth rate and smaller particle size would be a high supersaturated precursor with high KOH content and high pH value [42, 49]. The substance’s phase and morphologies are greatly influenced by the addition of water during the hydrothermal reaction Han et al. [49] and Chen et al. [19]. Analysis of the BFO hydrothermal synthesis method for the KOH concentration mineralizer, the reaction temperature, and the reaction time was performed. The precursors are held at175-225°C and 200-220°C respectively, for six hours, and produce phase-pure BFO powders using 8 M and 4 M KOH, respectively. Different raw materials and different hydrothermal equipment and conditions can contribute to the observed deviation from nominally optimal conditions (i.e., KOH concentrations). Han noticed that minor α-Bi2O3 could be generated while using a 4 M KOH solution. Scientists have noticed that metal nitrates, under some circumstances, combine with hydroxide ions to form the iron hydroxide phase.


At a lower concentration of potassium hydroxide, the alpha-Bi2O3 phase can stay in the precursor, although it can be reduced into Bi3+ at a higher concentration of potassium hydroxide:


Reaction temperature has a significant effect on the reaction. At lower temperatures, alpha-Bi2O3 is produced as the key product. By raising the temperature of the solution from 150–175°C, the dissolution of alpha-Bi2O3 is significantly improved. The BFO process stays the same at the temperature of 225°C [49]. A related result was stated by Chen et al. [19]. Although increasing the pH, reaction time, and temperature will improve the solubility of alpha-Bi2O3, leading to pure BFO phases. Secondary phases such as the secondary precipitate of excess potassium hydroxide precipitation at a shift in acidic pH may occur when excessive reaction time is at high pH. As OH- ion concentration is becoming higher, particle agglomeration can be expected [19, 49]. Yang et al. figure out the second phase of Bi2Fe4O9 forms at a shallow concentration of KOH. Since Bi3+ has a greater affinity with OH than Fe3+, a low OH-concentration in the hydrothermal reaction solution would lead to more Fe3+ ions being dehydrated Bi2Fe4O9 instead of bismuth ferrite. As a consequence of an increase of potassium hydroxide concentration, the percentage of Bi3+ and Fe3+ becomes balanced, and then the BFO phase is formed [50]. When utilizing heavy alkaline NaOH instead of weak KOH for hydrothermal synthesis, both the recipes produce stoichiometric materials. At a pH = 14, a limited quantity of H2O2 can assist the reduction reaction [42], whereas a milder acidic solution will afford a crude substance with recorded nonstoichiometric Bi12Fe0.63O18.945 [42]. Thus, it relies on the techniques used to achieve synthesize the latest phases. Researchers have managed to obtain pure BFO nanoparticles at 200oC by using 7 mol/L KOH and 12 mol/L KOH; however, incorporating NaOH and LiNO3 would either interrupt Bi2Fe4O9 and Bi12(Bi0.5Fe0.5)O19.5phase development or slow it down in the final product no matter the concentration of these reagents [19]. By utilizing potassium nitrate nanoparticles, much smaller nanoparticles of the potassium nitrate content are made. This study suggests that alkali ions (K+, Na+, and Li+) from mineralizer play a significant role in the development of rhombohedral, orthorhombic, and cubic pure bismuth ferrite BFO precipitates, respectively, [51] since the NO3 will raise the supersaturation of the heat transfer solution and intensify the nucleation of the BFO, thus decreasing particle size [52]. Cationic radii for mineralizers also influence the size and morphology of nanoparticles. Hojamberdiev et al. concluded that mineralizers steadily decrease the total particle size before they hit the critical stage. The particle size decreased to exceedingly small amounts [19, 42, 48, 53, 54]; on top of these problems, particle size frequently reaches the limit of 100 nm [19, 53, 54], which compromises the efficiency of the substance. In comparison, the hydrothermal process is expensive and difficult relative to the sol-gel process.

2.1.3 Microwave-hydrothermal synthesis

Microwave-hydrothermal (MH) synthesis is a modified synthesis method based on the hydrolysis technique. The starting materialis very equivalent to the hydrothermal synthesis starting material, but Na2CO3 is frequently utlized as the mineralizer in conjunction with KOH [2, 3] to gained perovskite BiFeO3 crystals. After transferring the starting material into a Teflon autoclave, it is placed in a microwave oven for the hydrothermal reaction, which is heated at 160-230°C for 30–60 minutes [2, 3, 51, 52]. The particle size produced by MH techniques could be as minimal as 10-50 nm [2] that is smaller than the average particle size produced by hydrothermal process. Furthermore, MH has been utilized to create bismuth ferrite nanotubes with an average size of 50–200 nm and a low bandgap of 2.1 eV [3].

2.1.4 Auto-combustion synthesis

In this process, Bi(NO3)3.5H2O and Fe(NO3)3.9H2O are frequentlyutilized as the oxidizer, whereas glycine (C2H5NO2), sucrose (C12H22O11), ethylene glycol (C2H6O2), ethanolamine (C2H7NO), citric acid (C6H8O7.6H2O), urea (CON2H4), stearic acid (C18H36O2), etc. may be utlized as fuels. To begin, the metal nitrates are dissolved in dilute HNO3 [55] or distilled water [56] to form an aqueous solution, and then the fuels are added to the solution while constantly stirring. Then, the resulting starting material is moved to a container that can be heated to between 80 and 200 degrees Celsius [55, 56] to form a densify gel-like product. Then, the gels are heated in a furnace to above 300°C to initiate the auto combustion reaction, which produces the final bismuth ferrite nanomaterials [55]. The combustion reactions with glycine and sucrose as fuels are demonstrated below, where bismuth ferrite as the only solid metal oxide product and carbon dioxide, water and dinitrogen simply illuminated during or after the reaction.


Nevertheless, because secondary phases are frequently constructed with bismuth ferrite, the procedure would be much more complicated. Despite this, Farhadi et al. [57]. Later conducted a study by Yang et al. [55] utilized sucrose (C12H22O11) to acquire phase-pure nanoscale BFO powders. The influence of fuel composition on the resulting bismuth ferrite phases discovered that glycine (C2H5NO2) or ethanolamine (C2H7NO) performs better. Throughout overall, the perovskite bismuth ferrite phase is acquired with some secondary phases, making control over the combustion process for phase pure bismuth ferrite difficult.


3. Characterization of BFO nanoparticle

To understand and evaluate the potential impacts and harmful effects of nanoparticles (NPS), proper knowledge of their physic-chemical properties is required. This can only be achieved using appropriate techniques to provide all the necessary information about the interested nanoparticles (NPS). Several nanoparticles (NPS) measurement techniques vary in sensitivity and quality information about the sample. The most commonly utilizedmethods including x-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), superconducting quantum interference device (SQUID), Fourier transforms infrared (FT-IR) spectroscopy, energy-dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy (MS), and thermogravimetric analysis (TGA)Several papers have reviewed some of the techniques for the manifestation of ferrite nanoparticles [58, 59, 60, 61], as well as the size-dependent functional properties and possible use of BFO nanoparticles are discussed in this section.

3.1 X-ray diffraction (XRD)

X-ray diffraction (XRD) is one of the most widely used techniques to differentiate NPs. Typically; XRD provides crystal structure, time-related nature, lattice parameters, and crystal letter size. The following parameter is expected to benefit from Scherrer statistics to extend the most robust XRD size for specific tests. The advantage of XRD techniques, routinely performed on powder-type samples, is usually followed by drying its corresponding colloidal solutions, resulting in common mathematical values with a measure of volume. The consistency of these particles can be determined by comparing the position and strength concerning the peaks and conduct of the guidelines provided by the International Center for Diffraction Data (ICDD, formerly known as the Joint Diversity Guidelines Committee, JCPDS) database. However, it is probably not suitable for non-manufactured materials, and XRD peaks expanded with particles with a size less than 3 nm. Upadhyay et al. found the standard crystallite size of the magnetite NPs using the X-ray line extension and noticed staying at a selection of the number 9–53 nm [62]. The pensiveness of the XRD peaks is caused by particle size/crystallite and lattice types {other than metal extensions [42]. XRD-based size is usually significant compared to so-called magnetic size because of the sub domain names that exist in particles where they always coincide if you look at the same direction and if the particle is a single domain. In contrast, the limited TEM size was more prominent than computer-generated XRD models with larger particles; assuming the particle size is greater than 50 nm, more than one or more crystal boundaries are in their region. XRD cannot distinguish between two parameters; hence, some models’ actual (TEM) size can be very noticeable compared to the 50–55 nm determined by the Scherrer formula. Dai and his colleagues set up a very small Au NP that was expected to improve significantly by following ⟨111⟩ (instead compared to ⟨220⟩ one) while the top-to-front analogy was the largest XRD size [43]. Similarly, Li and peers found that when preparing copper telluride nanostructures of different types (i.e., cubes, vessels, and rods), the total stiffness between the associated XRD peaks differed in the number of growing particles [44, 63].

3.2 Scanning electron microscopy (SEM)

Scanning electron microscopy (SEM) is a commonly used technique for a high-resolution image of the surface that may separate nanoscale objects. SEM uses electrons in thinking; a bright microscope uses clear light. Mazzaglia et al. blended field-emission SEM (FE-SEM) and XPS standards for analyzing supramolecular colloidal systems in Au NPs/amphiphilic cyclodextrin. Both methods provide essential information about the morphology and nature of the interaction of (Ethylhexyl carbon string) SC6NH2 and (thiohexadecyl carbon chain) SC16NH2 with Au NPs in the silicon region [19]. Sinclair and colleagues even suggested that SEM and NanoSIMS could help find Au NPs in cells. SEM testing has highlighted its superiority overNanoSIMS when reviewing inanimate NPs in complex biological systems. NanoSIMS delivers low localization of approximately 50 nm, as long as SEM can receive resolutions up to 1 nm. The particles tested have been Raman-active Au-core NPs, and NanoSIMS results in slightly unreadable images in a few cases due to its limited efficiency. Despite this, NanoSIMS introduces new isolation power between isotopes and may or may not be appropriate for Au NPs status [45]. High-resolution SEM (HRSEM) when it comes to rendering Au NPs to cells and cells. The easy appearance of metal NPs is guaranteed by this strategy and by preparing the test quickly and easily. Then again, in biological examples, the requirement to reduce the recycling of materials may form the appropriate metal layer; for this reason, it increases the risk of radiation damage when it comes to specimens. The advantage of HRSEM, when compared to other photographic methods, is the ability to lower precision and analyze the views of nanometric elements with their broader perspective. It makes it possible to review the specific spatial plan of the NPS and assess the functional relationship between them. The study results praised HRSEM’s potential as a moderately advanced tool to effectively highlight points that enhance Au NPs transmission through the epidermis buffer. It can be observed on a powerful and versatile device to capture better the interactions between biological systems and metallic nanostructures [46]. SEM size and AFM are compared to the same set of NPs, i.e., SiO2 and Au NPs in mica or silicon substrates. For example, AFM information has enabled the magnitude of the nano object to sub-nanometric accuracy, yet the dimensions of the sides (corresponding to the X and Y axes) have significant errors due to tip/sample flexibility. Compared to AFM, SEM cannot provide any metrological information about the length of this NPS; but even then, modern SEM can provide the correct measurements for their back weight. The size of the circular SiO2 NPs using both techniques yielded very similar results, showing consistent consistency and resistance of both metals [64]. SEM can be managed by looking at the transmission mode, that is, by using a method that is perceived as transfer to an electron scanning microscope (T-SEM) (see Figure 1). The most advanced NP tests can be taken by finding the full facts and studying NP practices if you look at the transmission mode. By Rades et al., A combination of different techniques such as SEM, T-SEM, EDX, and Auger microscopy (SAM) scanning is an excellent way to assess the depth of morphological and chemical properties specific. Silica and titania NPS. While acknowledging that, methods such as SAXS, DLS, XPS, XRD, and BET may be appropriate to define NPs ensembles, except for particles alone. T-SEM enables rapid analysis of NP form, although its lateral quality is limited to NP magnitude up to 5–10 nm. TEM offers excellent high-quality images, but T-SEM can be easily integrated with EDX to assess NP size and much-needed structure [47] quickly.

Figure 1.

Picture of an SEM/EDS technique running when you look at the transmission setting using the Zeiss single-unit transmission install(PE: Primary electrons; SE1: Secondary electrons emitted during the point of the effect regarding the PEregarding the sample; TE: Transmitted electrons; BF: Bright field; DF: Dark field; E-T; Everhart-Thornley detector). Reprinted with authorization from Ref. [47]. Copyright Royal Society of Chemistry 2014.

3.3 Transmission electron microscopy (TEM)

Transmission Electron Microscopy is a straightforward notification process for monitoring atomic and molecular alignment. TEM is an effective investigation into the size and shape of nanoparticles. Jewelry and particle measurements can be found in the TEM test. TEM is a microscopy method that uses a link between a continuous electron beam current (i.e., power is usually within the range of 60 to 159 keV) as well as a small test. As soon as the electron beam reaches the test, the electron element is sent, although sleep is transmitted flexibly or in elastically. The size of the connection depends on various problems, such as size, test density, and initial structure. The final image was made using information obtained by transmitting electrons. TEM is the most common method for measuring nanoparticle size and composition as it provides precise images for testing and more accurate testing of nanoparticle homogeneity. However, a few limitations should be considered fixed whenever production of this method is produced, such as the problem of measuring a few particles or unreliable images due to the impact of the stand. Whenever examples are surprisingly similar, alternatives that determine the sheer number of nanoparticles can provide more reliable results, such as the SAXS of the most potent formula and the Scherrer [48], or the XRD presentations and the Scherrer formula. Nanoparticle structures almost certainly depend not only on their size and shape but also on something else, such as particle lengths. For example, whenever two metal nanoparticles are helped to bring it closer, their few plasmons change their plasmonic arrangement and change their color. Later, TEM features have been is used to describe the nanoparticle collection of various biomedical systems, including hearing and diagnosis, when based on the presence of a biomarker or analyst [49, 50]; treatment, in which the collection results in the therapeutic development of the nanoparticle effects [51]; and (iii) photographs, in which the collection shows the development of a response mark [52]. In order to obtain reliable results, additional procedures should be taken to suspend testing if it is considered that an inadequate code of conduct may result in test modification or artifact production [55]. The primary control of nanoparticle-setting settings has been achieved for many years now, and it has been successful} NP installs can lead to NP dinner directors. Subsequent construction of various nanocrystals results in new multidisciplinary structures that include features of specific emerging barriers and an increase in recent and attractive structures [56]. TEM-elements are among the mechanisms used to introduce assorted superlattice nanocomposites, which are usually isostructural in a wide range of atomic crystal systems [57]. These brand new triangular compounds are created by various NPs (e.g., quantum dots, metals, and magnetic NPS), and their final field} and structure can be handled by creating a colloid circuit [57] or a direct link to DNA [55].

3.4 Superconducting quantum interference device magnetometry

Superconducting quantum interference device magnetometry (SQUID) is a tool for calculating the magnetic fields of nanoscale objects. Nanomaterials, in some cases, exhibit properties that are different from those in the plural form due to their small size and awareness of local conditions. As the material decreases in size, it progresses from multiple domains to a single domain and eventually to a superparamagnetic state. Standard SQUID measurements produce features such as magnetization filtration (MS), magnetization remanence (Mr.), and inhibitory temperature (Tb). On the side of NPs, the magnetic response of particular molecules can be tested by SQUID. A magnetic scanner that incorporates nanoSQUID features that have already been created recently made about a sharp quartz apex. NanoSQUID is considered the most inspiring investigation into nanoscale magnetic imaging and spectroscopy. The nanoSQUID sensor requires a Josephson subcutaneous micron coating, provided by two Dayem nano bridges (nano-constriction of the superconducting film), made of electron beam lithography {focused ion beam (FIB) with the same length and width and compliance length. The main SQUID requirement developed to obtain a magnetic NPS is a small SQUID area. Loop sizes should prefer the NPS integrated [58] to achieve the most fantastic merging feature. About magnetic resonance | microscopy or magneto-optic spin recognition, nanoSQUID provides the advantage of the exact magnitude of the magnetic field in small spin paths. In addition to its inefficient construction with the step of nanopatterning alone, Dayem nanoSQUID bridges can withstand the magnetic field used inside the SQUID loop plane [59]. The test set of the nanoSQUID is shown in Figure 2.

Figure 2.

Scheme of the experimental setup for the NP magnetization dimensions. The difference of the crucial current is acquired by averaging the changing current activities assessed simply by using a time-of-flight method. The quality of the essentialcurrentmeasurementsis mostly about 1 component in 104. The feedback circuit permits the rise of the robust linear variety of the sensor. The image shows the owner, the sample, andthe multiturn feedback coil. Reprinted with authorization from Ref. [59]. Copyright 2013 springer.

3.5 Vibrating sample magnetometry (VSM)

Vibrating test magnetometry (VSM) has become an additional feature that can be used to report that MH will hinder magnetic nanomaterials and get parameters like Ms. the magnetic field, temperature, and duration. Fabris and his colleagues made NP magnets controlled by the rainfall system in the presence of tetramethylammonium hydroxide. All tested samples were superparamagnetic, evidenced by zero compulsions and zero residues regarding the magnetization loop. Saturation magnetization retains the purpose of the NP size line [60]. Kumari et al. define the concept of reversible curves in the first order, which is the setting of hysteresis barriers from the main loop. Curve reversal order (FORC) works well in determining domain size, composition, and interaction on a magnetic field. It is an effective technique to obtain a semi-quantitative measure of the sufficient size of a magnetic particle. Under certain circumstances, the FOC may facilitate the disclosure of the existence of secondary magnetic experiments, thus assisting in the formation of more accurate characters for magnetic structures. VSM magnetometry was eventually used} to obtain such FOC measurements [61]. For further work, FeCo NPs used a framework of long anisotropic chains that had been prepared with a sputter-based gas cooling process, and VSM tested its magnetic properties. Deep interactions involving exchanges between NPs were confirmed in a chain-like sample, while well-dispersed samples revealed a completely different magnetic effect. ZFC/FC curves and time-dependent magnetic field measurements were assisted to obtain data regarding the thermal stability of the tested NPs [65]. In addition to the entire structures of the hysteresis loop of magnetic media, there has been a growing desire for the balance of remanence curves. Remanence measurement determines only the irreversible part of magnetization and, for that reason, makes it possible for the transformation events to be removed from the hysteresis scale, which includes the retractable object. Two primary reversal curves create isothermal remanence and a DC demagnetization curve. The previous one is being evaluated following the use and completion of a field with all magnetic resonance samples. The DC demagnetization curve is calculated based on the state of focus using the increasing fields of magnetic removal. VSM scales can detect these remanence curves and provide an accurate distribution of the neglected field of building materials [66].

3.6 X-ray photoelectron spectroscopy (XPS)

X-ray photoelectron spectroscopy (XPS) is one of the most widely investigated research methods for further chemical reactions, it is also used to classify nanoscale objects. What is clear from physical thought is the effect of electrical images [67]. XPS is an effective quantitative process for determining elements’ electronic structure, primary structure, and oxidation conditions in a matter. It can also test the ligand exchange interactions with local NP operations and key structures/shells and operate under very high vacuum conditions. Nag and colleagues have published a review paper outlining the role of XPS as a fun way to study the internal heterostructures of NPs. For example, it was used to investigate the structure of a crystal structure dependent on the environment of the metal chalcogen NPs of various sizes [67]. It can also distinguish between core/shell and homogeneous alloy structures and identify ligand binding modes such as trioctylphosphine oxide (TOPO) on the surface of metal chalcogenide NPs. For example, if a TOPO bond is preferable to the surface of the metal, then a portion of the excess chalcogenide may be easily oxygenated in the air. In contrast to microscopy techniques, such as TEM, which uses side-by-side alignment to determine elements in a straight line to the test electron column, XPS investigates the formation of an object aligned with an electron line. Concerning the core-shell NPs, shard has published a text that reports the precise way to translate XPS data for those types of particles. It involves a straightforward approach to turning XPS firmness into an overlay layer, ideal for round NPs. As an additional benefit of XPS, the author mentions that it provides in-depth information, such as the size of NPs (at a depth of 10 nm from the top), and does not seriously damage the samples. Two barriers to XPS analysis are sample preparation (i.e., solid dry form is required without contamination) in addition to the information definition.

3.7 Fourier transform infrared spectroscopy (FTIR)

Fourier transform infrared spectroscopy (FTIR) measures the absorption of electromagnetic radiation in the infrared medium (4000–400 cm−1). When a molecule absorbs infrared radiation, the moment of the dipole is somehow altered, and the molecule becomes an active IR. The recorded spectrum contains energy-related bands, bonds, and specific functional groups that provide molecular structures and interactions. Feliu and colleagues used the combined in situ ATR-FTIR and defaulting electrochemical mass spectroscopy to investigate the effect of Pt nanostructures during ethanol oxidation (DEMS). These methods assisted in the electrochemical analysis of adsorbates and the detection of flexible reaction products. Their findings support previous findings, showing that the decomposition products selected were related to the above structures, the formation of Coads in the (100) domains, and the formation of acetaldehyde/acetic acid in 111 domains. One study used carbon-backed NPs (3–8 nm in size) to obtain CO oxidation and a catalytic process was performed with DRIFTS and quadrupole mass spectrometry (QMS). According to the QMS results, FTIR ratings of adsorbed CO verified Coad and Oad variations in different test phases. While changes in the distribution of CO over different types of Pt sites were also observed. Overall, DRIFTS was considered an essential tool for assessing the local structure of Pt NPs in situ. Shukla et al. published a paper on FTIR oleylamine research. The anterior ligand is bound to FePt NPs in both monodentate and bidentate forms, while oleylamine is bound to FePt and the NH2 group is substantial. In addition, Au/Ag bimetallic NPs are dodecanetiol-soluble and dissolved insoluble solvents incorporated into water/toluene via a two-phase synthetic route [43]. The most important finding from the XPS and FTIR ratings was that Ag atoms were enriched on the outer edge of the hybrid clusters compared to Au atoms. ATR-FTIR was used in another study to assess the effect of Ag NP content on photocatalytic degradation of oxalic acid advertised in TiO2 NPs. Various Ag NP values ​​were tested, and it was found that inserting only a tiny amount (2 percent) significantly improved the photocatalytic performance of TiO2 NPs. NP composite films’ location and chemical structure/composition were observed using AFM and XPS. Tzitzios et al. created hexagonal Ni NPs with a diameter of 13–25 nm by reducing nickel stearate in the presence of PEG, oleic acid, and oleylamine. The presence of different groups on the surface of NPs, such as HCvCH- setting in OAC and OAm, was indicted by the FTIR spectra, and the mechanisms for ligand binding in the NP area were also investigated. Haram and its allies have used the hot-shot method to make copper zinc tin sulpho-selenide (CZTSxSe1-x) nanocrystals. For incorporation, the precursors were dispersed in OAm and heated to T > 200°C. OAm advertising on particle surfaces is reflected in FTIR ratings. Feature belts are derived from components present in the OAm molecule and effectively interact with NPs. The number of NP organic ligands is determined [67].


4. Properties in BFO nanoparticles

4.1 Ferroelectric

Ferroelectricity electricity is usually expected to disappear in smaller sizes due to a decrease in the relative length of the dipoles [66, 67]. Exact measurement of ferroelectricity in 0-D nanostructures and identification of proper ferroelectric size - the result is a difficult task. To begin with, making electronic contact with a single nanoparticle can only be done using scanning test methods, and no report has ever published the ferroelectric hysteresis characteristics of a single nanoparticle according to our knowledge. The problem is exacerbated by the small size and leaky nature of BFO nanoparticles due to the reduced bandgap and switching voltages that are likely to be very close to the dielectric cracking [46]. Vasudevan et al. [57] investigated the ferroelectric characterization of BFO nanoparticle clusters prepared for automatic firing methods using band excitation piezoresponse spectroscopy (BEPS) and piezoresponse force microscopy (PFM) (larger than 50 nm). They confirmed the ferroelectricity of nanoparticles by obtaining a symmetric piezoresponse loop with a compliant 8 V voltage of a single batch distributed in the LSMO/STO substrate (Figure 3 (a)). In addition, they found the properties of the ferroelectric domain (Figure 3 (b) and (c) within groups of particles, similar to those found in small BFO ​​films [61]. There is often a direct link between ferroelectricity and lattice strain (using a known strain-polarization coupling). This means that a detailed structural investigation into each area’s lattice parameter or removal can provide important information. Selbach et al. [31] A systematic study of the relationship between nanoparticle size and BFO lattice parameter illustrates this point. As shown in Figure 3, these researchers found that nanoparticles more prominent than 30 nm have lattice limits than a BFO mass. In contrast, at less than 30 nm, the lattice parameter of BFO nanoparticles extends from the mass and approaches the cubic (i.e., paraelectric) perovskite structure. There is a decrease in the rhombohedral deviation of the cell unit (i.e., a decrease in c/a). When the rhombohedral angle reaches 60o, it equals the unit, indicating a fine cubic perovskite [31]. A significant dc size of 9 1 nm of ferroelectricity was obtained using the empirical model to match tetragonality based on BFO size [31]. Automatic polarization determined by removing Bi3+ and Fe3+ cations at 13 nm nanoparticles was 75% of the total volume. This makes BFO nanoparticles an exciting class for many materials because they can have both a strong magnetic field (discussed below) and sufficient ferroelectric polarization for novel applications [31].

Figure 3.

(a) Piezoresponseand phase hysteresis loops of a solitary BiFeO3 nanoparticle. Out-of-plane PFM amplitude (b) and phase (c) pictures of a nanoparticle cluster, pre, and post-putting on +10 V, 5 s pulse towards the center of this cluster. Insets in (b) and (c) demonstrate the PFM amplitude and phase pre applying the bias; correspondingly, the above assessment had been performed.

4.2 Photocatalytic

Compared to BFO thin films, which typically have a bandgap of 2.7 eV [22], BFO nanoparticles prepared chemically have a bandgap as low as 1.8–2.3 eV. As a result, they are appealing for use in photocatalysis. Nanosized BFO particles have demonstrated improved photocatalytic performance, which can be applied to the degradation of organic pollutants such as dye compounds of Methyl orange (MO), Methylene Blue (MB), Congo Red (CR), or Rhodamine B. (RhB). Geo et al. [22], for example, confirmed that BFO nanoparticles, in addition to responding to UV light, have excellent MO degradation ability when exposed to visible light (Figure 4(a)).As shown in Figure 4(b), Geo et al. discovered that Gd-doped BFO nanoparticles could improve their photocatalytic properties by increasing RhB degradation rates from 79 percent for BFO to 94 percent Bi0.9Gd0.1FeO3 [26]. Using BFO as a photocatalytic agent is its photostability, affecting photocatalytic efficiency under visible light. It is investigated the nonphotostability of BFO nanoparticles by studying RhB dye decolorization at pH 2, 4, and 6, 7, as shown in Figure 4(c). They discovered that photo corrosion occurs in the RhB dye solution due to the dissolution of Fe from the Fe-O bond, resulting in nonphoto stability. This photo corrosion can be explained as an offshoot of the BFO band offset concerning the RhB dye, in which holes can be injected from the RhB dye into the BFO valence band. As shown in Figure 4, replacing the BFO nanoparticles in the RhB solution at regular intervals can achieve a much higher decolorization rate, which can even exceed TiO2 (d). As a result, BFO nanoparticles are extremely promising for visible-light-driven photochemistry. Compared to small BFO ​​films, typically with a 2.7 eV bandgap [22], BFO nanoparticles are chemically modified with a band as low as 1.8–2.3 eV [22, 54]. As a result, they requested use in photocatalysis. Nanosized BFO particles have shown improved photocatalytic activity, which can be used in the decomposition of organic pollutants such as compounds of Methyl orange (MO), Methylene Blue (MB), Congo Red (CR), or Rhodamine B (RhB). Geo et al. [22], for example, confirmed that BFO nanoparticles, in addition to UV radiation, have excellent potential for MO degradation when exposed to visible light (Figure 4 (a)). As shown in Figure 4 (b), Geo et al. found that Gd-doped BFO nanoparticles can enhance their photocatalytic properties by increasing the rate of RhB degradation from 79 percent in BFO to 94 percent in Bi0.9Gd0.1FeO3 [26]. As a result, there is strong pressure to develop alternatives. Due to the p-n junction built into the p-type BFO interface and the n-TiO2 type, the presence of BFO nanoparticles improves the image degradation performance under visible light while preventing the reunification of electron-generated electrons. As shown in Figure 4 (a), the efficiency of the depletion of TiO2 nanofibers in MB is only 3% after 150 minutes, but this performance can be achieved to nearly 100% when 5 mol% and 10 mol% BiFeO3 nanoparticles are incorporated in TiO2 nanofibers [64]. Moreover, boosting the density of BFO nanoparticles has a negative impact on photocatalytic activity because they can obscure active sites of TiO2 and inhibit electron transfer to the BFO / TiO optical connector. Correspondingly, under visible light, the performance of BFO / TiO2 nanotubes image conversion can be increased from 0.7 percent for pure TiO2 nanotubes to 3.2 percent for BFO/TiO2 composite nanotubes [50], which can be seen in Figure 4 (b). Other abnormalities which have been encountered to improve photocatalytic function include BFO-graphene and nanohybrid [52]. The improved magnetic performance and optical illumination of the BFO nanoparticles described above make them excellent candidates for advanced development and application.

Figure 4.

(a) Photocatalytic removal activities of methyl orange under UV-vis light irradiation and visible light irradiationutilizingBiFeO3 nanoparticles as well as bulk, [51] recreated with authorization from ref 104, copyright2007 WILEY-VCH Verlag GmbH & Co. kraal, Weinheim; (b) photocatalytic removal effectiveness of RhButilizingGd substituted BFO nanoparticle samples, [26] recreated with authorization from ref 26, copyright 2010 American Chemical Society (c) and (d) photo removal information of RhB utilizingBiFeO3 as photo reagent at different pH values under AM1.5 lighting; [65] (d)tests had been carried outwith the substitution of theBFO nanopowders at frequentperiods, into the dye answer, decolorization at pH = 2 reveals higher than 95% decolorization after 10 min, the inset demonstratesthe removal activities of RhB utilizingnanostructured (Degussa P25) TiO2, [65] recreated with authorization from ref 103, copyright 2012 Royal Society of Chemistry.

4.3 Magnetoelectric coupling

Magnetoelectric bonding (ME), which can detect coexistence with the same combination of ferroelectric and magnetic properties, maybe the most notable feature of nano-BFO-based materials. As a result, many researchers are focusing on the promise of merging the boundaries of magnetic and electrical order. Zhao et al. [3] were the first to demonstrate the electrical control of the antiferromagnetic domain structure in a single-phase BFO film, showing a solid interaction between the two types of structure at room temperature. They found that before and after electric cooling, the antiferromagnetic base structure was firmly attached to the ferroelectric base structure. Automatic polarization occurs near the axis. The angles 71o, 109o, and 180o show three distinct divisions as the rhombohedral axis changes. It was found that the interaction between the antiferromagnetic domain and the ferroelectric domains occurs only with a polarization of 71o and 109o, but not with a change of 180o ferroelectric polarization. This work is an essential first step for researchers interested in investigating ME nano-BFO compound materials. However, due to the slight spin canting, it is not easy to achieve the significant coefficient of magnetoelectric coupling magnetization. The acquisition of magnetic anisotropy in the optical connector of ferromagnetic-antiferromagnetic heterostructures allows for a more extraordinary animation of device applications. Thin-film heterostructures also benefit from the way magnetic anisotropy of the system can be constructed with epitaxy. As a result, researchers are keenly interested in combining ferromagnet-multiferroic exchange heterostructures for BFO sub-film, particularly oxide ferromagnet/BFO heterostructures and transition metal ferromagnet/BFO heterostructures. For oxide ferromagnet/BFO heterostructures, La0.7Sr0.3MnO3 (LSMO) is popular. It is found that different magnetic exchange effects were produced at different LSMO/ BFO sites because Fe3+ and Mn3+ or Mn4+ are ferromagnetic, competing with a wide range of antiferromagnetic order. Later, Wu et al. [19] used the LSMO/BFO system to demonstrate the electronic control of exchange bias. They found a reversible shift between the two biased regions by changing the ferroelectric polarization of the BFO. This is a significant step forward in controlling pornography by power control, and it is an essential step towards spintronic electronic control devices. However, due to the relative temperature dependence of the ferromagnet/BFO heterostructure exchange, achieving renewable electrical control of the magnetoelectric junction at room temperature remains difficult. The ferromagnet transition metal (Co0.9Fe0.1) ferromagnetic layer to form a heterojunction with the BFO to control the local magnetic field room temperature. Magnetic anisotropy was modified using an electric field in the aircraft. After an electrical switch was investigated, they found that the linear domains moved from left to right. The domains then recede after the use of a different electric field. At room temperature, the electric field can control the flexible wall of the electric field, as shown in this series of pictures. Most importantly, this work demonstrated the magnetoelectric in front of the electric field at room temperature.


5. Conclusions

In conclusion, the nano-BFO is a suitable multiferroic nanomaterial with a few unique features, including high polarization of residue, magnetoelectric composite at room temperature, and small bandgap. It also serves as a flexible platform for exploring new novel works. This review of the topic focuses on significant improvements made in the study of integrating nano-BFO-based materials, features, structures, and applications. Several operational strategies have been proposed. Proper substrate selection and morphotropic phase boundary formation have been widely used in the modification to improve ferroelectric efficiency and magnetic field. The impact of size on behavior on nano-BFOs is also a significant problem.

Efforts to achieve outstanding results have been made on fixed memory, piezoelectric sensors, and photodetectors. However, many challenges remain until those modern facilities are completed. First and foremost, it is essential to improve the efficiency of ferroelectric and magnetoelectric energy. The nano-BFO is highly fragmented. Is it possible to achieve high polarization of ferroelectric power? Will nano-BFO devices show a broad magnetoelectric response at room temperature? Second, should sufficient switching speed be required for systems based on ferroelectric or ferromagnetic switching? Most of the recorded speed of change and the durability of the switch does not meet the memories of the universe. As a result, there has been a long way to go to increase memory on nano-BFO-based devices. Third, the physiological processes under the influence of photovoltaic and photocatalytic activity in nano-BFO remain a mystery. BFO photocatalyst and photovoltaic devices are expanded only by exposing the visible structures. Several ideas have been suggested; however, there is much disagreement, and further research is needed. Fourth, only a few nano-material structures have been observed to reflect composite structures. Many nanomaterial systems should be built to investigate the potential for new applications. With this review, we hope to provide a current summary of the problems and opportunities that arise, which may inspire more researchers to pursue future nano-BFO production.


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Written By

Sheela Devi, Venus Dillu and Mekonnen Tefera Kebede

Submitted: 08 March 2022 Reviewed: 01 April 2022 Published: 09 July 2022