Comparative investigation on the structural, morphological, optical, andmagnetic properties of CoFe2O4 nanoparticles
K. Kombaiaha, J. Judith Vijayaa,⁎, L. John Kennedyb, M. Bououdinac, R. Jothi Ramalingamd,Hamad A. Al-Lohedand
a Catalysis and Nanomaterials Research Laboratory, Department of Chemistry, Loyola College, Chennai 34, Indiab Materials Division, School of Advanced Sciences, Vellore Institute of Technology, (VIT) University, Chennai Campus, Chennai 127, Indiac Department of Physics, College of Science, University of Bahrain, PO Box 32038, Bahraind Surfactant Research Chair, Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
Herein, we report a sustainable production of magnetic cobalt ferrite nanoparticles by conventional (CHM) andmicrowave heating (MHM) method. Hibiscus rosa-sinensis extract was used as both reducing and stabilizingagent. Using plant extracts to synthesize nanoparticles has been considered as an eco-friendly method, since itavoids noxious chemicals. The plethora of plant extract mediated nanoparticles were compared by techniques,such as XRD, Rietveld, FT-IR, SEM, EDX, UV-Visible DRS, PL and VSM were carried out to analyze andunderstand their crystallite size, functional groups, morphology, optical and magnetic properties. The crystal-line structure of cobalt ferrite nanoparticles revealed the cubic structure and the microwave heating ofnanoparticles showed smaller crystallite size compared to the conventional heating, which was then confirmedby XRD analysis. To analyze the presence of functional groups and the phytochemical involvement of the plantextract was confirmed by FT-IR studies. Spherical morphology with less than 100 nm sized particles wasconfirmed by SEM and EDX analysis confirm the existence of Co, O, and Fe elements present in the samples.UV-Visible DRS studies were carried out to calculate the band gap of the as-synthesized nanoparticles,estimated from the Kubelka-Munk function, as 2.06, and 1.87 eV for CHM and MHM, respectively.Photoluminescence emission spectrum of the nanoparticles showed two different bands at 494 and 620 nm,which explores the optical properties of the nanoparticles, due to the quantum confinement effect. VSM analysisshowed better ferromagnetic behavior, which can be used for magnetic applications.
1. Introduction
In recent years, research on the nanoparticles is of great interest,because they act as a bridge between the bulk materials and atomic ormolecular structures. It often possesses unique optical properties asthey are small enough to confine their electrons and produce quantumeffects [1–6]. Metal ferrites are important in modern clay materialscience, because of their potential applications in electronic gadgets.Now-a-days ferrites are the very important attention of energy storageand photocatalytic application of antibacterial and anticancer applica-tions [7–10]. Also, it has high permeability and stability in terms oftemperature of operation and longevity. Metal ferrites are the com-pounds with a general formula of MFe2O4, where M is a divalent metalion, eg; (Ni, Co, Mn, Zn etc.). Ferrites crystallize in three differentcrystal types: spinel, garnet, and magnetoplumbite [11,12] Due to theferromagnetic property as well as the high electrochemical stability,
cobalt ferrite is found to be more malleable and therefore it is animportant spinel compound. Cobalt ferrite has an inverse spinelstructure i.e, ferric ions are present at the tetrahedral sites and bothferric, and cobalt ions are present at the octahedral sites. It is expectedthat CoFe2O4 can be used as an electro catalyst apart from its electricand magnetic applications, due to its conducting nature [13]. However,it exhibits good electrochemical properties and hence used as amaterial for hybrid supercapacitors and Li-ion batteries [14]. Cobaltferrite is chosen in the present study, because of its large magneticpermeability, relatively low magnetic loss, high cut-off frequency, highsaturation magnetization, high curve temperature, temperature stabi-lity, low coercivity and biodegradability [15,16]. The special attentionis given to spinel type of ferrites, which can be synthesized by a sol-gel,conventional, mechanical, hydrothermal, self-propagating combustion,thermolysis, wet chemical co-precipitation, micro emulsion, microwavesynthesis etc [17,18].
http://dx.doi.org/10.1016/j.ceramint.2017.03.069Received 13 February 2017; Received in revised form 10 March 2017; Accepted 11 March 2017
Among the above mentioned techniques, microwave and conven-tional methods are used for the synthesis of cobalt ferrite nanoparti-cles. In microwave method, sample absorbs the microwave energy andconverting it into heat energy. Since microwave synthesis is a branch ofgreen chemistry, it is said to be eco-friendly, pollution-free and it offershigh yield with simplicity in processing and handling. Recently, it hasalso gained much attention in the field of drug discovery and in well-known cyclization reactions for heterocyclic ring formation and inother important reactions, such as nucleophilic substitution andhetero-Diels-Alder reaction [19]. In addition, this method is said tobe highly efficient, less time consuming, inexpensive and high rate ofsintering [20,21]. Microwave irradiation method does not require hightemperature and pressure and thus it enables large-scale synthesis as itreduces the thermal gradient effects. The efficiency of the microwavemethod depends on the ability of the material to produce heat byabsorbing microwave radiation. This is based on the dipole rotationand ionic conduction mechanisms. By the direct absorption of theseradiations, the polar reactants with high microwave coefficient can beexcited. Dielectric heating leads to the increase in the rate of reaction,due to their differences in the solvent and the reactant dielectricconstants. High reaction temperatures can be achieved by usingsuitable metal precursors with large microwave absorption cross-sections relative to the solvent. The rapid energy transfer to thereactants results in an instantaneous internal temperature rise. As aresult, the activation energy is decreased and the rate of the reactionincreases. Therefore, the reaction temperature, pressure and time canbe controlled easily. This creates highly supersaturated solutions by therapid decomposition of precursors. Nucleation and growth in thesesupersaturated solutions can lead to the formation of their respectivenanocrystalline products. Higher the supersaturation, smaller will bethe critical size for nucleation. Thus, in microwave method, when thereactions are controlled, the nanocrystals with good monodispersityand crystallinity are formed [22].
The important challenge for the green chemistry is the innovationof new technologies for catalyst separation and recycling to replace theconventional procedures. Recently, the search for the environmentallybenign chemical process or methodologies has received much attentionfrom chemists, because they are essential for the conservation of theglobal eco system. The use of biological organisms, such as, microorganisms, plant extract or plant biomass, which could be an alter-native to chemical and physical methods for the production ofnanoparticles in an eco-friendly manner. In addition, without the useof toxic chemicals or the need for high pressures, energy andtemperatures, the use of plants can be easily scaled up for large-scalesynthesis. Plant extracts are used as both reducing and capping agentsfor the synthesis of nanoparticles. The plant extract plays the dual roleof a fuel with a coordinating action, thus occupying the metal ions inthe amylose helix of the extract through the transparent sites. It alsoimpedes the separation of the metal oxides. An interesting topic of thisresearch field is the non-polluting and controlled synthesis of oxidematerials, which involves the natural compounds of low cost as rawmaterials and also as active ingredients for the nanosized metal oxideparticles [23,24].
H. rosa-sinensis is known for its medicinal value as it has strongpolyphenols, flavonoids, and anthocyanins. H. rosa-sinensis is amember of Malvaceae family and is an evergreen herbaceous plant.The leaves are alternate, ovate and lanceolate. They have often toothedor lobed margin [25]. The use of plants for the synthesis of nanopar-ticles is efficient and proves to be a cost effective and eco-friendlyalternative method to chemical and physical synthesis. In addition tothat the use of plants can be easily scaled up for the large scalesynthesis without the use of toxic chemicals or there is no need for highpressure, energy, and temperature. Also, nanoparticles present a highersurface area to volume ratio with a decrease in size, distribution, andmorphology of the particles. Here, we present a systematic study on thesynthesis of cobalt ferrites using H. rosa-sinensis plant extract by
microwave and conventional method and the characterization wasaccomplished using various techniques like XRD, FTIR, SEM, EDAX,UV-VIS-DRS, and VSM.
2. Experimental section
2.1. Materials
The precursors Co(NO3)2·6H2O, (Merck) and Fe(NO3)3·9H2O,(Merck) were used as the oxidizing agents. Both the chemicals wereused without any additional refinement, due to the analytical grade. H.rosa-sinensis plant extract was used as the reducing agent. All thesolutions were prepared using deionized water.
2.2. Preparation of the plant extract
H. rosa-sinensis extract was prepared by using 15 g portion ofcrops, which were thoroughly washed and was used in this presentstudy instead of toxic organic compounds. The leaves were finely cutand mixed with 50 ml of deionized water. It was stirred thoroughly for1 h using a magnetic stirrer at room temperature to form a homo-geneous solution. The homogeneous solution was filtered and used asan extract.
2.3. Synthesis of CoFe2O4 nanoparticles by conventional heatingmethod
Cobalt nitrate (Co(NO3)2·6H2O) and ferric nitrate (Fe(NO3)3·9H2O)in the molar ratio of 1:2 are dissolved separately in the double distilledwater and then kept under stirring to obtain a homogeneous clearsolution. The extract of H. rosa-sinensis plant was then added slowly indrops to the above solution under vigorous stirring for several hours atroom temperature until a clear solution is obtained. It is then kept in anhot air oven at 180 °C for 3 h for drying. The obtained powder wasground using a mortar and pestle and then kept for sintering at1000 °C for 3 h in the muffle furnace. The final powder obtained waswashed with ethanol and labeled as CHM.
2.4. Synthesis of CoFe2O4 nanoparticles by microwave heatingmethod
The clear solution containing the metal nitrates and plant extractafter vigorous stirring (as mentioned in the earlier section) was taken ina silica crucible and irradiated at a frequency of 2.54 GHz at 850 Woutput power for 15 min using a domestic microwave oven. At first, thesolution starts to boil in order to undergo dehydration and later theevolution of enormous amount of gasses is observed, because of thedecomposition. The point of spontaneous combustion, where theburning of the solution has started followed by vaporization hasresulted in the formation of a solid, which in turn confirms thecompletion of the reaction. The obtained powder was ground in amortar pestle, washed with ethanol followed by drying in a hot air ovenat 100 °C for 1 h. Final powder obtained was then labeled as MHM.
2.5. Characterizations
X-ray diffraction (XRD) was performed to detect the structuralphases using high- resolution Rigaku Ultima IV. Rietveld refinementwas operated by PDXL program for the calculation of lattice para-meters. Fourier transform infrared spectroscopy (FTIR) was studiedusing Perkin-Elmer infrared spectrophotometer in the range 4000–400 cm−1. Scanning electron microscopy (SEM) measurements werecarried out using a VEGA 3 TESCAN, USA. Energy-dispersive X-rayspectroscopy (EDX) was carried out by Brucker Nano, GmbH, Berlin,Germany. The UV–Visible diffuse reflectance spectra of the sampleswere obtained using Cary100 UV–Visible spectrophotometer. The
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photoluminescence properties were studied using Varian Cary EclipseFluorescence spectrophotometer. Magnetization measurements werecarried out using a vibrating sample magnetometer (PMCMicroMag3900 with 1 T magnet).
3. Results and discussion
3.1. XRD analysis
XRD analysis was carried out to attain indisputable informationabout the crystalline structure of the as-prepared CoFe2O4 nanoparti-cles. It is the most useful non-destructive analytical technique tomeasure the crystallinity of the samples. Fig. 1a and b shows the X-ray diffraction pattern acquired by the sample prepared by conven-tional (CHM) and microwave heating (MHM) method. Both themethods depend upon the synthesis temperature and the reactiontime. The obtained peaks of the CoFe2O4 nanoparticles are at 2θ=30.20°, 35.54°, 37.10°, 43.11°, 53.57°, 56.97°, 62.69°, 70.94°, 74.14°,75.20°, and 78.96°, which satisfied the Joint Committee PowderDiffraction Standard Data (22-1086). The non-existence of extra peaksin the diffractogram of nanoparticles prepared by both the methodssuggests that the samples are highly pure and single crystalline innature. Also, among all the peaks, the nanoparticles have speciallyadapted along (311) plane, which is later used to calculate the crystal-
lite size of the nanoparticles as per Scherrer formula [26],
D kλ βcosθ[ = / ] (1)
Where D, k, λ, β and θ are crystallite size, Scherrer constant,wavelength of X-ray, Full width half maximum of (311) plane andBragg diffraction angle respectively. The calculated average crystallitesize values are found to be 56 nm and 43 nm for CHM and MHMrespectively. The reflection peaks obtained in CHM becomes strong andsharp, due to the calcination temperature, which leads to the increasein crystallite size with an increase in the temperature. The increasedtemperature led to a drastic increase in the crystallite size. Hence, anincrease in the size of the crystallites takes place owing to solid-statediffusion to form CoFe2O4. The increase in the lattice parameter andthe reduction in microstrain are due to the improved crystallite growthat the grain boundaries that reduce the defects and overall linebroadening during annealing. [27]. In CHM, there is a consumptionof high energy and time. The sharp intense peak in CHM indicates thatthe materials are highly crystalline in nature and the particle size isimproved. This result satisfies the Ostwald and coalescence technique[28]. Even though, it forms higher crystallinity with single phaseformation and it requires higher calcination temperature, during thesynthesis. But, the nanoparticles prepared by MHM showed singlephase crystalline nature and smaller crystallite size compared to CHM.This can be explained on the premise of bulk heating of the materials,which was kept inside the microwave oven. It could have ultimatelycaused molecular agitation and friction, due to the uniform distributionof the temperature with dipole amendment of the polar molecules [29].
3.2. Refinement of XRD analysis
Fig. 2a and b shows the Rietveld refinement plots of cobalt ferritenanoparticles. The data which are plotted in the upper field indicatesthe observed intensities, whereas, the difference between observedintensities and the calculated intensities are shown in the lower field asred color. Measured parameters, such as lattice parameter and fittingparameters including Rp, Rwp, Re and χ2 are shown in Table 1. Theseparameters are used to check the fitting quality of the experimentaldata. The lattice parameter values listed in Table 1 are in goodagreement with the JCPDS No. 22-1086. The increase in latticeparameter and decrease in microstrain in CHM are attributed to theimprovement of crystal growth in the grain boundaries, which reducesthe defects present in the sample during calcination temperature [30].Value of goodness of fit (χ2) should not be less than one. But, in ourcase, the value of χ2 lies in the range of around 1.57 and 1.30 for CHMand MHM respectively, which is almost good in agreement with the
Fig. 1. XRD pattern of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
Fig. 2. XRD pattern refinements using the Rietveld method of (a) CoFe2O4-CHM and (b) CoFe2O4- MHM nanoparticles.
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refinement of the data. The deviation in the χ2 value for both thesamples might be due to the difference in the observed and calculatedvalues. The value of discrepancy factor is closer to MHM, which showedthat the parameters were refined better than that of CHM andsimultaneously give the goodness of fit. The decrease in Rwp valuesfrom 27.87% for CHM to 26.46% for MHM corresponds to thevariation in the crystallite size of the nanoparticles that decreases from56 to 43 nm. On the other hand, Rexp value increases with an increasein the lattice parameter in CHM and decreases with a decrease in latticeparameter in MHM [31].
3.3. FT-IR analysis
FT-IR analysis was carried out to categorize the various functionalgroups of CoFe2O4 prepared by CHM and MHM. In the FT-IRspectrum (Fig. 3a and b), due to the energy of radiation, eachcomposition attained some vibrational bands at certain wave numbersand thereafter showing it as absorption. FT-IR spectrum exists indifferent vibrational region, such as 400 cm−1, 600 cm−1, 1600 cm−1,2900 cm−1and 3400 cm−1 respectively. The bands observed between500 and 600 cm−1 are assigned to the intrinsic stretching vibration attetrahedral sites, whereas the band at 350–450 cm−1 is attributed tothe stretching vibration at octahedral sites. The bands around 427 cm−1
and 437 cm−1 corresponds to Co-O bond. The peaks at 597 cm−1 and599 cm−1 are strongly attributed to the Fe-O bond in the as-preparedsamples [32]. The peaks at 2917 cm−1 and 2937 cm−1 are attributed toC-H stretching vibration present in the sample [33]. The broadstretching at 3438 cm−1and 3452 cm−1 indicates the mode of bindingthrough OH group present in the samples [34]. This can be attributedto the water molecule adsorbed on the surface of the nanoparticles. It isobserved that the normal mode of vibration of the tetrahedral site ishigher than that at octahedral site, which is due to the shorter bondlength of tetrahedral than the octahedral. In case of ferrites, Waldron[35] has reported that the bond distance of Fe-O at tetrahedral site(1.89 Å) is smaller than the bond distance at octahedral site (1.99 Å),which suggest that Fe3+ ions have greater covalent bonding character attetrahedral site than that at octahedral site. We believe that the
difference between the present tetrahedral and octahedral is due tothe different bond lengths at the octahedral and tetrahedral sites assuggested by Waldron [35]. The results obtained in FT-IR areconsistent with the results obtained from XRD. The organic com-pounds present in the homogeneous solution mixture were removed bycalcination in CHM and metal-oxygen bands only remained. But in thecase of MHM, the organic compounds were removed without anyadditional calcination. Because, in the microwave process, the pre-cursors produce high temperature and form single crystalline structurewithin shorter reaction time.
3.4. SEM analysis
Fig. 4a and b showed the SEM images of MHM and CHMnanoparticles. The nanoparticles prepared by MHM were in agglom-erated form, due to the force of attraction bringing them togetherduring the synthesis. The size, shape and morphology of all theparticles are almost uniformly distributed in MHM. The size of theMHM nanoparticles is spherical in shape and found to be in the rangeof 15–20 nm. Whereas, CHM nanoparticles had an irregular sphericalshape and size in the range of 50–75 nm. The irregularity in CHM isdue to the higher calcination temperature given during the synthesis.During the calcination, the surfaces of small size nanoparticles weremelted and aggregated to form bigger nanoparticles in order to reducethe interfacial energy of the individual nanoparticles. Also, the calcina-tion temperature enhanced the coalescence process, which resulted inan increase in the average size of the nanoparticles. Similar results havebeen reported previously in ferrite systems with higher calcinationtemperatures [36]. The agglomeration present in the samples is due tothe interaction between the magnetic nanoparticles. The morphologyshowed some areas as agglomerated, some regions spherical in shapeand some particles are detached from other particles. This can beexplained on the basis of Ostwald ripening [37].
3.5. EDX analysis
The elemental composition was analyzed by energy dispersive X-ray(EDAX) analysis (Fig. 5a and b). The obtained results indicate thatthere are three peaks corresponding to cobalt, two peaks correspondingto ferrites and one peak to oxygen, which in turn confirmed theformation of cobalt ferrite nanoparticles. EDX images did not show anysignificant difference in the prepared samples. The elemental reportconfirms only Co, Fe, and O present in the sample without any otherelements. The estimated composition present in the samples is wellmatched with the nominal compositions. Thus, the results mentionedin the table confirmed the formation of single phase cobalt ferritenanoparticles.
3.6. UV–Visible DRS studies
The diffuse reflectance spectra are used to study the band gap ofCoFe2O4 nanoparticles through UV-Visible diffusion reflectance spec-troscopy (Fig. 6a and b). Usually, optical properties depend upon fewfactors like band gap, grain size, lattice parameter, oxygen deficiency,and surface roughness [31]. To identify the band gap energies of thesamples, [F(R)hv]2 against hv is plotted, where F(R) is kubelka-Munkfunction F(R) =(1−R)2/2 R [38] and R is reflectance in UV–Vis spectra.By extrapolating [F(R) hv]2=0, the value of band gap energy obtained is
Table 1Lattice parameter, crystallite size and fit parameter values of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
Sample code Crystallite size (nm) Microstrain (%) Lattice parameters (Å) Rwp (%) Refinements Rp (%) factors Re (%) S χ2
Fig. 3. FT-IR spectra of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
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2.06 and 1.87 eV for CHM and MHM respectively. Generally, thestructure of ferrites has two bands namely O-2p orbital at the valenceband and Fe-3d orbital at the conduction band respectively. The bandgap energy between O-2p and Fe-3d for MHM sample is lesser thanthat of CHM sample. Because, when we increase the calcination
temperature in CHM, the band gap between O-2p and Fe-3d increases.This revealed that the concentration of oxygen vacancy decreases.Simultaneously, the absorption band is shifted to lower wavelength andthe band gap increases in CHM. Therefore, the amount of energyrequired to excite an electron from O-2p to Fe-3d increases. Also, when
Fig. 4. SEM image of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
Fig. 5. EDX spectra of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
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we kept the samples for calcination, the fermi level is shifted toconduction band and the band gap energy was increased [39].
3.7. Photoluminescence studies
Fig. 7a and b demonstrates the PL spectra of cobalt ferritenanoparticles measured at room temperature under the excitationwavelength of 325 nm. It is the important technique used to study theoptical properties of the materials. Both the methods consist of twopronounced emission bands located in the visible region, which is goodin agreement with DRS studies. The emission band located in thevisible region is mainly due to the structural defects, such as vacancieslike interstitial-vacancy within the band gap during the particle growth[40]. The emission at 494 nm corresponds to green emission. The peakemitted at 620 nm is attributed to yellow emission of the as-preparednanoparticles. It is evident from the results that both the samples havebetter enhancement in the luminous intensities. Also, there is no shiftin the position of the absorption peak. The direct transition betweenthe valence and conduction band causes the enhancement in theintensity of the samples [41].
3.8. VSM analysis
Fig. 8a and b shows the magnetic measurements for the samplesCHM and MHM, which was carried out at room temperature usingvibrating sample magnetometer (VSM). The as-determined parametersincluding saturation magnetization (Ms), coercivity (Hc), and reme-nant magnetization (Re) are listed in Table 2. The magnetic propertiesof the samples varied with the crystallite size and preparation methods.The variation of saturation magnetization and remanent magnetizationcan be attributed to the change in the degree of inversion in thenanoparticles. As we mentioned in earlier section, by Scherrer equa-tion, the decrease in the crystallite size observed in MHM leads to adecrease in saturation magnetization. This might be due to thestructural distortion that occurs on the surface of the nanoparticles.The smaller particle size of MHM increases the inert layer causingsaturation magnetization to decrease [42]. Also, the magnetic proper-ties of the nanoparticles depend upon the size of the nanoparticles. Asthe particle size decreases, the surface area increases and the surfaceenergy and surface tension are also high. This has resulted in theexchange in the cationic preference and then increase the anti-sitedefects, thus Ms decreases. As the particle size decreases, the coercivityalso decreases, which could be transformed from ferromagnetic tosuper paramagnetic nature [43]. The value of Ms and Hc increases withan increase in the calcination temperature. As the particle sizeincreases, surface to volume ratio decreases and it has resulted in theincrease in saturation magnetization. The energy required for themagnetization or demagnetization by the domain wall movement isvery low. As the number of domain wall increases with increase inparticle size in CHM, the wall movement contribution to the magne-tization or demagnetization is higher than that of single rotation. It isfound that the higher crystallinity makes the magnetization valuehigher. The material becomes hard and permanent magnet as thecoercivity increases in CHM and the sample MHM becomes softmagnetic, due to lower coercivity. Smaller size of the nanoparticles
Fig. 6. UV–Visible diffuse reflectance spectra of (a) CoFe2O4-CHM and (b) CoFe2O4-MHM nanoparticles.
Fig. 7. Photoluminescence studies of (a) CoFe2O4-CHM and (b) CoFe2O4-MHMnanoparticles.
Fig. 8. Magnetic hysteresis (M–H) loops of (a) CoFe2O4-CHM and (b) CoFe2O4-MHMNanoparticles.
Table 2Magnetization, remanence and coercivity of (a) CoFe2O4-CHM and (b) CoFe2O4-MHMnanoparticles.
Sample code Coercivity (Oe) Remanence(memu/g)
Saturationmagnetization (memu/g)
CHM 1575 26.96 56.43MHM 734 25.48 55.29
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turned into a single domain and thus resulted in the decrease in thesaturation magnetization [44]. Thus, we conclude that the existence ofminimum saturation magnetization has resulted from the smaller sizeof the nanoparticles. The decrease in Ms value depends upon themagnetic moment present on the surface of the nanoparticles. Also, theaim of using Hibiscus rosa-sinensis is to use it as a fuel with acoordinating action so that, we could attempt the synthesis as a greenchemistry route. The magnetic properties are also increased whencompared with hydrothermal synthesized CoFe2O4 using glycine as afuel [45] and comparable with the ones prepared using sesame [46]and Aloe vera [47].
4. Conclusions
In this green era, we have synthesized cobalt ferrite nanoparticlesby using natural plant extract as a capping agent for fabulous extent inan environmental protection. The method used for the synthesis wassimple, quicker, large scale production, and completely green synthesis.The XRD, FT-IR, and EDX studies confirm the formation of cobaltferrite nanoparticles. The crystallite size increased with an increase inthe temperature in CHM and decreased in MHM. The goodness of fit isgood in agreement with the theoretical value confirmed by Rietveldanalysis. The metal oxides present in the samples are confirmed by FT-IR analysis. The SEM images clearly indicate the spherical andagglomerated nanoparticles. The MHM nanoparticles showed smallerparticle size than CHM as shown in SEM images. The elements presentin the EDX analysis confirm the purity of the samples. UV-Visible DRSexplored the band gap of the nanoparticles which is closer to the bandgap of the bulk nanoparticles. The band gap value increases with anincrease in temperature in CHM. The photoluminescence spectrumconfirms the presence of defects in the samples. This techniqueprovides a way to synthesize nanoparticles by greener way in anordinary laboratory. The novelty of the present work can be extendedto other metal oxides and metal ferrite nanoparticles.
Acknowledgement
We thank Loyola College management for the infrastructuralfacility and the authors (R. J and HAA) also thank Deanship ofscientific Research, King saud university for funding through Vicedeanship of Scientific Research Chairs.
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