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

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.

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.

The white cotton fabrics were hack into necessary size, washed with demineralized water and sterilized. The sterilized cotton fabrics were dried and permitted to embed with ferrite particles by immersing them in Erlenmeyer flask (300 mL) containing ferrite particles (1000 ppm) under constant stirring for 24 hours at 150 rpm. After one day the ferrite particles treated on fabrics were dried using laboratory padder and allowed to dry at 80 °C for 5 minutes in hot air oven. The well dispersed cotton fabrics were developed at 160 °C for 4 minutes for curing and stored at room temperature 89.

To study the antibacterial activities of ferrite particles treated on cotton fabrics, agar based diffusion method was performed 89. Ferrite particles treated on cotton fabrics (10 mm × 10 mm) were used. The selected Gram positive (Staphylococcus aureus, Bacillus subtilis, Streptococcus sp.) and Gram negative (Escherichia coli, Proteus mirablis, Klebsiella pneumonia) bacterial pathogens were inoculated in sterile nutrient broth and incubated at 40 °C for 24 hours. The plates were incubated for 24 hours at 40 °C and then zone of inhibition around the fabrics was recorded.

The ferrite particles treated on cotton fabrics were evaluated for their antibacterial activities before and after washing. Ferrite particles coated and uncoated fabrics have taken separately in 3000 mL sterile Schott Duran flasks and added with 1 mL of overnight grown bacterial suspension. After complete dispersion cotton fabrics were transferred to nutrient broth and incubated in rotary shaker at 150 rpm. After 24 hours incubation, 1 mL of broth from both the treated and untreated on fabrics was collected serially diluted (up to 10^-7 dilution) and spread plated on nutrient agar (NA) plates. After one day incubation, the NA plates were examined for the enlargement of bacterial colonies. From that the percentage reduction of each bacterium was calculated using the formulae: PR = (100(B-A)) / B, …(1)

where PR is the Percentage reduction (%); B is the total number of bacteria recovered from untreated on fabrics; A is the total number of bacteria recovered from nanoferrite particles treated on fabrics. The wash durability of ferrite particles treated on cotton fabrics was evaluated after 5, 10 and 15 wash cycles using neutral soap (5% Hiclean, HiMedia) at 40 ± 2°C for 45 minutes with a material to liquid ratio of 1:50. After 45 minutes the fabrics were rinsed, dried and this procedure was repeated up to 15 wash cycles.

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.

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).

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.

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.

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.

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.

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.

The surface morphology of MgMnNiFe₂O₄ ferrite particles treated and untreated on cotton fabrics were studied using electron microscopy.

The treated and untreated on fabrics were analyzed using FESEM equipped with EDS as shown in Figure 6 (a, b & c) and Figure 7 (a, b & c). The SEM images of unloaded cotton fabric showed smooth surface whereas Mg_0.45Mn_0.55-xNi_xFe₂O₄ (x=0.40) nanoferrite particles loaded cotton fabric showed rough surface [Figure 6 and Figure 7].

Similar to this present finding, Balakumaran et al. 17 have observed well dispersed silver ferrite particles in silver ferrite particles coated fabrics. The EDS spectrum of ferrite particles coated fabric showed strong peaks at ferrite region, confirming the successful immobilization of ferrite particles into cotton fabrics [Figure 7].

Disc diffusion technique was used to study the antibacterial activities of ferrite particles against pathogens at different concentrations like 25 µg/ml, 50 µg/ml, 75 µg/ml and 100 µg/ml by measuring the zone of inhibition. The prepared ferrite particles showed greater inhibitory activity against all the experimental strains with 50 µg/ml and above concentrations are shown in Figure 8 and Table 4. Above all, the pathogenic strain, Staphylococcus aureus was found to be more vulnerable to the synthesized nanoferrite particles. Next to Staphylococcus aureus, the ferrite particles inhibited the growth of Enterococcus aerogenes, Escherichia coli and Proteus mirabilis in a vital manner. The ferrite particles were found to be least toxic towards Klebsiella pneumoniae and Pseudomonas fluorescens. Thus indicating that the biologically synthesized ferrite particles were found to be possessing better antibacterial activities towards all the human pathogenic bacteria tested.

Above all, the pathogenic strain, Staphylococcus aureus was found to be more vulnerable to the synthesized nanoferrite particles. Next to Staphylococcus aureus, the nanoparticles inhibited the growth of Enterococcus aerogenes, Escherichia coli and Proteus mirabilis in a vital manner. The nanoferrite particles were found to be least toxic towards Klebsiella pneumoniae and Pseudomonas fluorescens. Thus indicating that the biologically synthesized ferrite particles were found to be possessing better antibacterial activities towards all the human pathogenic bacteria tested.

The main plan of the study is to test whether the ferrite particles could report antimicrobial activities to cotton fabrics or not. About 150 ppm of ferrite particles was coated in each cotton fabric using pad-dry-cure method and the fabrics were assessed for their antibacterial activities using typical procedure. In agar diffusion technique nanoferrite particles treated on cotton fabrics exhibited remarkable antibacterial activities against six different human pathogenic bacteria. Thus, it is evident that the present research shows better antibacterial activities as inhibition zone was found to be higher than previous reports 1718. The possible system for antibacterial activities of ferrite particles treated on cotton fabrics was probably owing to the formation of chemical bond among the functional groups of ferrite particles and the functional groups of the textile substrates and also the physical adsorption of the prepared particles on the surface of the fabrics 19. It is obvious from the Table 4 that antibacterial activity of the zone of inhibition = 100 µg/ml is found to be higher against both Gram positive and negative bacteria than those of other concentrations. However lesser activity is recorded on Pseudomonas fluorescens.

The responses of antibacterial activities are depicted in Figure 8a. Hence this laboratory is found to report antibacterial property of a few chosen bimetallic ferrite particles at definite ratios (for ex., x=0.40). The smaller fine ferrite particles have the greater surface area to volume ratio. This enhances their biological and chemical activity by raising the contact area of the bimetal with a microorganism. The use of nanoscale bimetals allows achieving hundred time decreased concentration and at the same time increase in antimicrobial properties.

The antibacterial properties of ferrite particles treated on cotton fabrics were evaluated against selected Gram positive and Gram negative bacteria. The antibacterial efficiency of the prepared nanoferrite particles treated on cotton fabrics was studied using agar diffusion assay and the results were shown in Figure 9. The nanoferrite particles treated on fabrics displayed good antibacterial activities with a clear zone of inhibition around the cotton fabrics against all the tested pathogens; however the untreated (control) on fabrics did not show any inhibition zone.

These results specify that an increase in nanoferrite particles concentration generates strong antibacterial activity toward the tested pathogens. It shows that the antibacterial activity of the nanomaterials increased with increase in surface-to-volume ratio owing to the decrease in size of nanoferrite particles. Furthermore preceding studies have indicated that the smaller ferrite particle size, the greater the efficacy in inhibiting the growth of bacteria than other’s reports 202122. Conversely the prepared ferrite particles were formerly reported to act both as bactericidal agent and also bacteriostatic agent possibly thereby limiting their biomedical use.

Further investigations are required for substantial increase of antibacterial characteristics of ferrite particles by modulating the molar ratios of them considering their applied use in pharmaco- therapeutic industry and nanodrug delivery system.

The antibacterial activities of ferrite particles loaded on cotton fabrics were carried out before and after numerous wash cycles. The prepared ferrite particles treacted on cotton fabrics depicted tremendous laundering stability with pronounced antibacterial activities even after 15 wash cycles. The percentage of inhibition of bacteria was found to be decreased with increasing of wash cycles from 5 to 15 Table 5.

In the present investigation we observed more reduction of bacterial colonies irrespective of the concentration of ferrite particles content of the fabrics than that of others. In an earlier studies 2324 they observed nearly 50% loss of antibacterial activities after 20 wash cycles whereas we observed that after 15 cycles and this present study suggested the use of binder or cross linker to improve the durability of the fabrics. The reduction of bacterial colonies irrespective of the concentration of ferrite particles on fabrics is much higher than that of the other reports 2324.

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.