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Abstract

In this research work Mg_0.45Mn_0.55-xNi_xFe₂O₄ ferrite particles of varying compositions (x=0.05, x=0.15, x=0.25, x=0.45 and x=0.55) were synthesized using cost effectual co-precipitation route. The synthesized ferrite particles were characterized by collection of techniques. XRD analysis confirmed the formation of cubic spinel structure of the ferrite particles. SEM and AFM analyses illustrated the morphology and size distribution of obtained ferrite particles. FT-IR study exposed that the absence of any additional peak related to second phase. VSM results indicated magnetic analyses such as saturation magnetization (M_S), Coercivity (H_C) and Remanence (Mr) of ferrite particles. The major objective of the present investigation is to synthesize MgMnNiFe₂O₄ ferrite particles on cotton fabrics in order to obtain finished fabrics; it is very significant in biological applications. The antibacterial activities of the ferrite particles coated cotton fabrics were tested against selected Gram positive and Gram negative bacteria which showed tremendous results via formation of inhibition zones. The fabricated ferrite particles on cotton fabrics showed great durability evidenced by their antibacterial activities even after 20 washing cycles. Hence, the functionalized cotton fabrics could be used as potential antibacterial agent.

Introduction

Ferrite particles are relatively new materials which have a more effectual interaction with biological systems due to their high proportion of surface to volume ratio in comparison with bulk ones. This characteristic has ready them appropriate to be used in many medical and biological applications 1. Magnetic ferrite particles of iron oxides (Fe₃O₄ and Fe₂O₃) are now extensively used throughout the medicine, drug delivery, superparamagnetism, antimicrobial, non-toxicity, biocompatibility, biodegradability, chemical inertness properties 23. Recently, it is investigated that nanoferrite particle can be applied in biomedical field due to its antibacterial properties 4. Natural textile fibers are more susceptible to microbial stabbing than the man-made fibers. Microbial enlargement on fabrics and other textile products becomes evident as surface changes, discoloration, and unpleasant odors 5. In recent years, the medical textile fabrics were subjected to antimicrobial finishes to avoid the possibility of infections arising owing to the presence of microorganisms. Since there is an incidence of emerging of antibiotic resistance among the bacterial strains, there is a need to discover new antimicrobial compounds with diverse chemical structures and mechanisms of action. In the present study dealt with the loading of the prepared ferrite particles on cotton fabrics by pad-dry- cure technique. Accordingly, the antimicrobial activities of the particles loaded cotton fabrics against elected clinically pathogenic bacteria along with wash durability were evaluated.

Materials And Methods

Materials

The starting materials for the preparation of these series were NaOH pellets (>99%, Merck, Mumbai, India), magnesium sulfate MgSO₄.7H₂O (>99%, Merck), manganese sulfate MnSO₄.H₂O (>98.5%, Merck), and nickel sulfate NiSO₄.6H₂O (>99%, Merck).

Glassware and Apparatus

All glass wares such as measuring cylinders, test tubes, conical flasks, and beakers etc. were purchased from Borosil, India.

Synthesis of Magnetic Nanoferrite particles

Fine particles were synthesized by chemical co-precipitation method 6. The separate solutions of Mg-Mn-Ni compounds (with total concentration of 0.1M) and Fe₂O₄ (0.2M) were prepared in 100 mL of deionized water and heated at 80°C with constant magnetic stirring until a clear solution was obtained. After stirring, the pH value was around 7. Precipitates were washed five times with demineralized water and three times with acetone. The precipitate was then calcined at 500°C for 5 hours to obtain nanoferrite particles.

Instrumentation for Characterization

X- ray diffraction patterns were taken on X pert diffractometer using the Cu-Ka radiation at room temperature to investigate quality and structural behavior of the prepared ferrite particles. Morphological studies and chemical analyses were analyzed using FEI QUANTA 250 (SEM; Japan) with EDS. The topographical studies were taken using also with 130614 TOPOGRAPHY 045 atomic force microscopy (AFM; Bruker). Spectra analyses performed by Fourier transform infrared spectroscopy (FT-IR; PerkinElmer, MKS Technology of Productivity, Methuen, MA). Magnetic studies of the nanoferrite particles were performed using VSM (Vibrating Sample Magnetometer, Lakeshore, model 7404) with a maximum magnetic field of 20000 (G) and parameters like specific saturation magnetization (Ms), coercivity (Hc) and remanence (Mr) were evaluated.

Results

Results and Discussion-Characterization Studies For Nanoferrite Particles XRD

XRD Patterns were analyzed and indexed using powder X Software and used to characterize the crystallinity of ferrite particles. The diffraction patterns confirmed the formation of cubic spinel structure of the prepared ferrite particles. The strongest reflection comes from the (311) plane denoted the spinel phase Figure 1. The values of crystallite size D were measured by measuring FWHM of most intense peak (311) employing Scherrer’s formula as follows: D_avg=Kl/B Cosq, …(2) where K=0.89, the wave length of Cu-Ka radiation. The X-ray density (ρ_x-ray), measured density (ρ_m) and porosity (P) were also calculated using the following formulas 10. The lattice parameter values as deduced from the X-ray data are given in Table 1. From these calculated values we observed that the lattice constant (a) initially decreases and then increases with the increase in x = 0.15 and decreased from 8.332 Å to 8.223 Å. This increase could be also attributed to the substitution of the small sized Ni cation for the large sized Mn cation. Similarly average crystallite size (D_avg) decreases and then increases with the increase in x = 0.15 content as 14.25 nm to 9.50 nm. It was in good agreement with several other studies where larger metal ions have been substituted with relatively smaller metal ions 11.

Table 1. Average crystallite size and Lattice parameters of the ferrite particles

Compositions (x)	D _avg (nm)	a (Å)	ρ x-ray (X-ray density)	ρ _m ( measured density)	Porosity (%)
0.05	9.52	8.415	5.85	4.41	23.98
0.15	14.25	8.433	5.81	4.38	24.63
0.25	11.39	8.432	5.82	4.39	24.65
0.45	9.50	8.422	5.84	4.40	24.66

X-ray diffraction patterns gave the information of crystalline region only. The morphological studies of SEM and AFM explained the complete picture of ferrite particles. The SEM images analyzed the surface morphology, and grain size for the prepared samples is shown in Figure 2a. It was observed that the image was uniformly distributed and less agglomerated, homogenous spherical particles.

The EDS patterns getting for all the samples which have been given the elemental% and atomic% compositions and the elements detected in all the samples were O, Fe, Ni, Cu, Mg, Mn (Figure 2b).

Figure 1. The indexed XRD patterns of the Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles Figure 2a. SEM micrographs for Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles Figure 2b. EDS patterns for Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles AFM

The morphology of the prepared ferrite particles was analyzed by atomic force microscopy and found to have spherical shape and size of 20 nm to50 nm well in agreement with SEM data and exhibited a spherical shape of ferrite particles as observed using noncontact mode AFM, and the two dimensional view ^{2D view} of all the ferrite particles reveals uniform size and shape as indicated in Figure 3.

Figure 3. AFM topographic images of Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles Spectral Measurements

The FTIR spectra for ferrite particles are shown in Figure 4. It provides valuable information regarding the nature of the functional group attached to the metal ions. The significant peaks were recorded in the range of 4000 cm^-1 to 400 cm^-1.

Figure 4. FTIR spectra for Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles

The low-frequency peak (ʋ₂) attributed to the distribution of cations and anions on tetrahedral lattice sites, where as the high frequency peak (ʋ₁) was attributed to the distribution of cations and anions on octahedral sites 12. This was assigned to the octahedral metal atom stretching vibrations. From these we observed that Mg²⁺, Mn²⁺, and Fe³⁺ ions can occupy both octahedral and tetrahedral sites, and Ni²⁺ ions can occupy octahedral site. This is due to the atomic mass and ionic radii of the ions, Mg²⁺ (M = 24.30 amu; r = 0.72 Å), Mn²⁺ (M = 54.93801 amu; r = 0.89 Å), Ni²⁺ (M = 58.69 amu; r = 0.69 Å) and Fe³⁺ (M = 55.847 amu; r = 0.64 Å). Important FT-IR bands of the ferrite particles along with their possible assignments were shown on Table 2.

Table 2. Important FT-IR bands of the nanoferrite particles along with their possible assignments

Composition	Observed wave number	Transmittance/%
0.05	3,330.42	4
0.15	3,400.27	4
0.25	3,450.25	12
0.45	3,500.26	15

Magnetic Measurements

Magnetic properties of the prepared ferrite particles were studied by Vibrating Sample Magnetometer. In the cubic system, the magnetic order is mainly due to a super exchange interaction mechanism occurring amid the metal ions in the A and B sub lattices. Ferrite particles show low coercivity and low remanence proves that the particles are super paramagnetic behaviour 1314. Figure 5 shows the variation of magnetization M (emu/g) versus the applied magnetic field H (Oe) at room temperature for the prepared spinel nano ferrite particles Mn_0.45Mg_0.55−xNi_xFe₂O₄. All the curves appear to behave normally. The prepared samples exhibit a clear magnetic behaviour under applied magnetic field. It is evident from the results given in Table 3 that saturation magnetization, M_s and remanence, M_r increase from 8 emu/g to 23 emu/g and 1.40 emu/g to 3.02 emu/g, respectively, as Mn concentration decreased which can be explained on the basis of Neel’s theory 15.

Figure 5. Magnetic hysteresis curves for Mg0.45Mn0.55−xNixFe2O4 (0.00 ≤ x ≤ 0.55) ferrite particles

Table 3. The values of coercivity (Hc), remanent magnetization (Mr), saturation magnetization (Ms), and squareness ratio (Mr/Ms) of the prepared ferrite particles

Magnetic Parameters	Compositions (x)
	x=0.05	x=0.15	x=0.25	x=0.45
H _c ( Oe )	405	253	214	198
M _r (emu/g)	1.40	1.71	2.31	2.78
M _s (emu/g)	8	11	16	21
Squareness Ratio (R= M _r / M _s )	0.175	0.155	0.144	0.132

The decrement of squareness indicated that a significant amount of ferrite particles are still superparamagnetically fast relaxing at room temperature, when the external magnetic field is turned. The reduced values of the M_r/M_s ratio show powder ferrite behaviour, within the magnetization field, closer to the super paramagnetic one 16.

Conclusion

In the present research a simplistic approach was used to synthesize ferrite particles on cotton fabrics in order to obtain finished fabrics; it is very significant in biological applications. The results on the investigations of the nanoferrite particles demonstrate that these particles inhibited the growth of bacteria at very low concentrations. The influence of these ferrite particles and morphology of the nanostructure is significant for the antimicrobial activity of the prepared particles which is important for textile industries. Also these nanoferrite particles treated on fabrics showed tremendous laundering sturdiness as well distinct antibacterial activity even after 15 wash cycles. Thus, the application of these ferrite particles as antibacterial agent will be very precious for biomedical and industrial applications. This application can also be extended to produce ferrite particles embedded antiseptic dressing or bandage for medical purposes in the future.

Acknowledgement

The authors are thankful to Dr. K P Singh, Department of Zoology at University of Allahabad for useful discussion. Medical laboratory in-charge Dr. Patel, Green Cross Pathology and Molecular Laboratory, Paldi in Ahmedabad is acknowledged for skilled technical assistance. One of the authors Dr.S. R. Chitra gratefully acknowledges DST (Ref. no SERC no. 100/IFD/7194/2010-11 dated 12.10.10) and also UGC for the financial assistance received through the project.

Journal of Biotechnology and Biomedical Science