3.1. Structural Study
3.1.1.XRD (X-Ray Diffraction) Analysis
The XRD pattern of α-Fe2O3 synthesized with the help of the hydrothermal method was analysed Fig.1..The XRD pattern was in good agreement with that of the hematite phase of iron oxide (JCPDS Card no. #33-0664) with no additional or impurity peaks. The diffraction peaks can be indexed to the rhombohedral (hexagonal) structures of hematite with the lattice parameters a=b= 0.5034; and c=13.768 Ǻ. The sharpen peaks with high FWHM values can be attributed to crystalline structures corresponding to pure α-Fe2O3 nanoparticles. The calculated crystallite size was found to be ~ 70.44 nm by using Debye-Scherrer formula (Patterson 1939).
![](data:image/png;base64,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)
Where D is the average crystallite size, k is the Scherer’s constant, λ is the wavelength of radiation for Cu Kα, θ is diffracted angle, and β is FWHM of diffracted peaks. The physical parameters such as lattice strain and crystallite size are evaluated with X-ray peak broadening analysis. It can be clearly seen from equation (1) that the crystallite size (D) of nanoparticles is inversely proportional to the peak broadening (β) of the diffracted peaks. The Scherrer plot of Fe2O3 nanoparticles are shown in Fig.2 (a) with a linear relationship between y- co-ordinate as cos θ and x-co-ordinate as1/β. The crystallite size and lattice strain in the sample was also calculated by using the Williamson-Hall(W-H) method (Ilyas et al., 2019). Equation (2) is a representation of the W-H method, which gives a relationship between crystallite size (D) and lattice strain (ɛ)
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAWAAAAAaCAYAAACJr4ZfAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAdgSURBVHhe7ZiBUSs5DEBpgRpogR4ogRpogQ7ogA6ogApogAbogB5y9zjejUZne53Nwt5P9GY8ya5lW5Il2cnVoSiKotiFKsBFURQ7UQW4KIpiJ6oAF0VR7EQV4KIoip0YFuDPz8/D4+Pj4fr6+nB1dXW4ubk5PD8/f/deFvgC2z8+Pr7fbMPr6+uXf+/u7r7f/Bf2YGbdh4eHzfX7E3h6evryIXtUFFtybN6/vb0dVSOHBZiEJrDf39+/npmYQvzy8vL1vAcYqF7oQqN4/aRO2H9/f//99LfTvteNjSIA6JL7RjAvNo1sIAiQcx96MAd65PVjQ2a2oLc41c+sT9uSLQowduFj/cR87k1xmeS8B+Lh9vb23zhpXXq4VPF+hmF1YAELi3AL3jqBZrG48KnRJB3JQ8Kg19a3IObD5jwva6ILm5H7PCBmihWbBdiTNzuiHr3CyTyevMgaJLGAEFAWK/rWFNNT9t4DfK/4aYGv8Lv75V7iZ+ONA6u4LMw34wHIH+KEeCA2iGPio1Uf6J+Jm24BJgCZnIkiJPaoUPwUS7dv9LUIbwnFtOVIClurmFAIeZc3ZIYlv7rpLfJJjM7o17rBGUi9/hFr/cua6Njy2Z5YfNGvBfuJzjkPivOmlffEQM5r4of4yHUJOeJqKb+6BdgC46I8m7g5WHlWERrKZ0UpoJwU9POZAxp5EpN+C6nK08d7iv+IUdFZg4dQaz79E4sJNmL7WtC/VwiAPtbMMvgnF2/8O/LF2tvomuKpfu5jnoP32O6hwGeMIT4ZYx/ftQtfOFbYt/gOX/CdFhPF4orsCOKOsepTnDejvM9YB8inDDGf8zIzVYBN1lawkgAEpwoY1LEQMYYg9obmfFEGRZ0bOeR1AEnTWjujnPPyfab1YL1ev/6hGJCYrNnahFmYI/qxB2tGvwF25xN4qQCzHv0092WGNQUYP3po6LMI9mC7MsaHz6PY4JN+5IVxvmMcvkGOg591hHWRIWZHKJd9XJwno7zPWAdaOWQOjvJrqgADk1hsYwEg0HNBQIb3wDjmyUFugphkJGUMcMaZZBoy29YUiRbMExM2on9IagrCqWtqY/ZlxvUi+DLfzpYKMOivngw2KTNqozXYd2MIkM++4nnkP/p6sQHaGvFd9EuWm7XPFu0ozhfiopf3GWLCy0GGmCVuRgf8dAEWTwcTYCkwDfp8CnhTdiy3HozmuVdMRuuAOo+S+RhGc7mWxVfZrPsMjPHQ8uDq4VrC2NYYfRYLVYb+JZnMMb5lz7Nu+imCrhwsPd+NYgO0NTJ6p736csl+x/FZnD/s9UycE4vI9eLWGjGKm6MLcH6/tAB9yHjTldb8vMMgk008SZac4lreIvk+03rQ11tT/e33YKIg58NmCe1jTnQfjWe9qDNj4+1Q9AVztiBo6Kf1AqjF0h5EKL7ZFtZrzYHd9DGGYpzpxQZoa2T0Tp+4Zp4vo89bfi7OD/Z6Js6Jm1HuWCNG8bVJAW7dwAxW5JDJ13Dnaf3niSyJ5tV+tliYKCbYqTBXbyPUP/ZbSNE9Hzgj4t8KzDH6yaKNgu9bPtHvPV/4P+tMoEVm5fXPqCGD7tg+ugFHcmyAtkZG7/SJv8LyXzoRdGI92ox+xZ8PMbEU5+TPUjyYA8Rdj6MLsEUm/nfLs0ENKGaCINcyyOD3hpTXyQnkc+8/UvVtHQZr0bYWrpftwl6Slb6ZG5P+VBZ/RBtzMbZYQZaN5L+KIlHHYw4KWApMIQZYOzfWxAa+K8O70byzsREZvWNNcY97e+WY1kWhOE9GeQ8zxRescaM60F0lJotFknckbkx65XhP0hOwjImJ7U89g5j5kIm3GIxmLIbRKKQ5KZ2HceqELPOyfu82uBaTrzWnhRM7cr99NHTSF8ihZ7SL8fknN8/YRMubx5z6n/5coIF1mBfZWGzwGTahA601dom4Z2tAp2g/OqmPuuKvuMdLscEz88aY8120nzl5F+3WV6yPP3kG1laetTPI5rlAe1p+cp0MejNXbwwto27RZmGN3hj69KtYKLAps+Vc7MloTM+XjMts6f9ML+95JveYG5nYiMcs7zzZ3shiAcZ4FOc7yjNpBidQNJBBthUUjGM8MhaYCIY5h+tmgwC93MgoOzpl1oLjmD8mMbhubPpFv+XmBmGjAaVs9in+xD58GX1goqpPLELipvcaY/B9y7e/gTpEsIt36oh/YtCOYiOOo+Gb/A6ftN5FiJ8og/9ZN++9eMjm/lEBYH7syGA/Y7JOQAzQMsgyppVrrMFamV7RNA5bObTlXPiTMTn2egUYOeQZl9nS/xnmaM1tHWy11nrEact3kcUC3AqKS4LNbzl3DyicSxtaFMXpbJH3HAS5iGcWC3DrJLskOIU5+fJJ/9v8X/Qoikvg1HzjsjRTwBcL8FIFvwT8iZx/Ov0mbGbr52ZRFD/D2rxn3OztuVuA/Y+lkv4f2IS9/jtl3br5FsXvc2zeUy+P+degW4CLoiiKn6UKcFEUxU5UAS6KotiJKsBFURS7cDj8BTpWsV2I8KbLAAAAAElFTkSuQmCC)
The W-H plot of the nanoparticles is shown in Fig.2 (b) with a linear relationship between y- co-ordinate as βcosθ and x-co-ordinate as 4sinθ. The value of lattice strain was extracted from the intercept of the linear fit and found to be 0.77x10-3 whereas the crystallite size was estimated from the slope of the linear fit made to the plot and found to be ~74.5 nm.
3.1.2. Scanning Electron Diffraction (SEM) Analysis
The surface morphology and particle size of the Fe2O3 nanoparticles and α-Fe2O3@C20H38O11 NC nanocomposite was determined with the help of scanning electron microscopy (SEM) analysis. Fig.3(a, b) represents the SEM images of the as-synthesized Fe2O3 nanoparticles and α-Fe2O3@C20H38O11 NC nanocomposite, respectively. It was observed that the pristine Fe2O3nanoparticles were highly dense and uniform with high crystallinity and spherical shape. It was clear from Fig.3(a) that the Fe2O3 nanoparticles formed were softly agglomerated. However, when Fe2O3 nanoparticles were mixed with cellulose, the morphology of the particles changed its shape, and the agglomeration was reduced drastically as shown in Fig.3(b). The average particle size for Fe2O3 nanoparticles is about ~180±30 nm whereas the particle size was found to decrease in the case of α-Fe2O3@C20H38O11 NC nanocomposite to about ~60± 15 nm. This drastic diminution in particle size because cellulose as a solvent endorses self-assembly process. This non-classical process of grain modification trims down the agglomeration of Fe2O3 nanoparticles due to high surface energy. Modified nanoparticles are exceedingly recitalist towards the surface activity because of increased surface volume ratio. The EDX-pattern of α-Fe2O3@C20H38O11 NC nanocomposite is in good agreement of the stoichiometric presence of the expected elements in the sample Fig.3(c).
3.2. Antibacterial screening
α-Fe2O3@C20H38O11 NC nanocomposite and Cellulose were subjected to antibacterial activity against Klebsiella pneumoniae and Staphylococcus aureus; both gram-negative and gram-positive bacteria. In this study, the zone of inhibition analyzed for both organisms α-Fe2O3@C20H38O11 NC nanocomposite synthesized using the hydrothermal method exhibited significant activity against Klebsiella pneumoniae (11mm) Staphylococcus aureus (13mm), whereas cellulose paste poses no antimicrobial activity against both the bacteria. Synthesized α-Fe2O3@C20H38O11 NC nanocomposite exhibited promising antimicrobial activity due to proper dispersal of Iron nanoparticles in cellulose, and its synergistic effect and results were tabulated along with figures Fig. 4. (Table 1). ROS factors should be responsible for the potent antibacterial effect of synthesized nanomaterials (Abdal Dayem et al. 2017; Das et al. 2017). ROS amount of α-Fe2O3@C20H38O11 NC nanocomposite associates with the size, shape, and chemistry of synthesized nanocomposite materials. ROS response of metal nanoparticles is a key factor in modulating cellular signalling involved in bacterial cell death, and proliferation.
3.3. Ascorbic acid analysis during storage in tomato (Solanum lycopersicum) fruit
The ascorbic acid content in tomato (Solanum lycopersicum) fruit was analyzed under the effect of two different concentrations of α-Fe2O3@C20H38O11 NC nanocomposite (5%, &3%). All samples were kept at two different storage temperatures: room temperature (25±2 ºC) and refrigerator temperature (4 ℃) for day 0, day 4, day 8, day 12, and day 16. The content of ascorbic acid (vitamin C) in tomatoes fruit samples used in this study was about 28 mg/100 g (Stevens 1974). Recent studies reported that ascorbic acid content in whole mature-red fresh tomatoes was 13 and 26% higher than in mature pink and mature light pink tomatoes, respectively (Chomchalow et al. 2002). Storage study revealed that Fig. 5 with increasing storage time decline in vitamin C content in tomato fruit was higher at room temperatures (25±2 ºC) in uncoated tomato sample UC1. Almost 50% vitamin C content declined, and 8% loss of moisture was observed on 8th day of storage at room temperature in sample UC1; after 10th day of storage sample UC1 was spoiled and vitamin C analysis was not performed after this. In coated tomato samples UC1A (5% concentration of α-Fe2O3@C20H38O11 NC nanocomposite) 47% decline in vitamin C content on 12th day of storage at room temperature after that UC1A sample was spoiled. In coated tomato samples UC1B (3% concentration of α-Fe2O3@C20H38O11 NC nanocomposite) vitamin C loss in tomato was lower than UC1A and UC1; decline in vitamin C content was 36% at 16th day of storage at room temperature.
Whereas vitamin C content in tomato fruit stored at refrigeration temperature (4 ℃) was lower than tomato fruit stored at room temperatures (25±2 ºC) Fig. 6. In uncoated tomato sample UC2 (held at refrigeration temperature 4 oC) the vitamin C content declined by 43% and 7% loss of moisture at 16th day of storage. In coated tomato samples UC2A (5% concentration of α-Fe2O3@C20H38O11 NC nanocomposite) 29% decline in vitamin C content at 16th day of storage and in coated tomato samples UC2B (3% concentration of α-Fe2O3@C20H38O11 NC nanocomposite) vitamin C loss in tomato was lower as compared to UC2A, UC1A, UC2 and UC1; decline in vitamin C content was just 11% at 16th day of storage at refrigeration temperature. The study revealed that 3% coating of synthesized α-Fe2O3@C20H38O11 NC nanocomposite was able to keep tomato fruits fresh after 16 days of storage under refrigeration temperature. Tomatoes are sensitive to chilling conditions and urged storage temperature for tomato fruits varies with the ripening and maturity stage. Tomato fruits and other vegetables/fruits show a continuing loss in ascorbic acid content with long storage duration and increased temperature (Heinze 1974; Watada and Tran 1987). Bruising is a widespread problem occur at several stages of post-harvest handling and marketing of vegetables/fruits (Hussein et al. 2019; Opara and Pathare 2014; Sablani et al. 2006). Vitamin C degradation or chemical composition alteration may be due to microbial contamination or damage to the tissue.
Present storage study revealed that on uncoated tomato fruits, duration and temperatures variations influence on vitamin C content was significant (p>0.05) compared to the synthesized α-Fe2O3@C20H38O11 NC nanocomposite coated tomato fruits samples. Recent researches shown that vitamin C content in damaged tomato tissue was 15 to 16% lower than unbruised or undamaged tissue (Hussein et al. 2018; Ismail et al. 1993). These results indicated that α-Fe2O3@C20H38O11 NC nanocomposite coating significantly affected the chemical composition of surface tissues of tomato fruit and 3% α-Fe2O3@C20H38O11 NC nanocomposite was more effective in maintaining the quality of tomato after 16 days of storage under refrigeration temperature as well as at room temperature. Therefore, it is possible to increase the storage life of vegetables/fruits under natural conditions without adding and pesticide or hazard chemicals.
3.4. Fourier Transform Infrared radiation (FTIR) spectroscopy
FTIR analysis was done to determine the functional groups present in α-Fe2O3@C20H38O11 NC nanocomposite. Sharp peaks observed at 2973 cm-1 and 2876cm-1shown the presence of –CHO vibration or alkane stretching and peak observed at 1375 cm-1 were due to –CH2bending (Huang et al. 2012). A small peak at 3461 cm-1exposed the presence of –OH group of alcohol (Mohammad et al. 2017). The Fe–O stretching was present on 540 cm-1and a sharp peak was observed at 1050 cm-1due to C-O bonds of secondary metabolites present in biodegradable cellulose polymer (Shandilya et al. 2020) Fig. 7(a). Same well-defined sharp peaks of C-O stretching were observed at 1022 cm-1, 1029 cm-1 in the FTIR spectrum of stored tomato samples (tomato dry fruit pulp) UC1, UC1A and UC1B samples kept at room temperature (25 °C) Fig. 7(b) and (tomato dry fruit pulp) UC2, UC2A and UC2B samples kept at refrigerator conditions (4 °C) Fig. 7(c) respectively.
The prominent broad peak of C-O was associated with the cellulose and pectin compounds in tomato fruits (Skolik et al. 2019a; Skolik et al. 2019b). FTIR study revealed out the primary and secondary metabolites functional groups present in tomato fruit after kept them under storage study. Sharp peaks were observed at 1223 cm-1, 1231 cm-1 is due to C–OH bending vibrations(Doodran) and associated with monoterpenes (Ord et al. 2016), secondary metabolites comprising potentially volatile organic chemicals (VOCs) during ripening (Buttery et al. 1988; Skolik et al. 2019a). The peak at 1402 cm-1 vibration band related to the other alkane, polysaccharides and 1611 cm-1, 1604 cm-1may simply be a broad, vibration band related to ketones, monoterpenes representative of VOCs present at the ripen phase of tomato fruits(Rodríguez et al. 2013). The advent of strong and broad intensity band at649cm-1, 664cm-1was confirmed the presence of Fe–O starching in all tomato samples including controls(Święch et al. 2018). Merged peaks were observed at 2163 cm-1, 2178 cm-1of C-C alkynes and 2618 cm-1, 2174 cm-1ofC-H aldehydes secondary metabolites of tomato (Doodran). Vibrant merged peaks were analysed at 3372 cm-1, 3379 cm-1, 3297 cm-1,3335 cm-1, 3215 cm-1, and 3230 cm-1 represent the O-H stretching of carboxylic acid. FTIR spectra revealed that ripened tomatoes kept under α-Fe2O3@C20H38O11 NC nanocomposite storage study have increased amount of glycerol-lipids, primary phenolic compounds, cellulose, pectin and other carbohydrates moieties of VOCs.
3.5 Fe and Zn micronutrients contents
Concentrations of Fe and Zn micronutrients analysed in UC1, UC1A and UC1B samples (25 °C) and UC2, UC2A and UC2B samples (4 °C) Fig. 8(a, b) (Table 2) taken as a mean of three measurements. The highest Fe concentrations were observed in controls of tomatoesUC1 sample 21.8 mg/kg on 8th day (after that sample spoiled) and UC2 sample 20.9 mg/kg on 16th day respectively. Study revealed that there were no penetrations of Fe nanoparticles through α-Fe2O3@C20H38O11 NC nanocomposite coating in tomato fruits during 16 days of storage. Fe content was decreased during storage; on 10th day when UC1A sample was observed Fe content was 18.4 mg/kg and on 16th day in UC1B sample Fe content was 16.52 mg/kg. Tomato samples kept in 4°C for storage study have stable Fe concentration i.e. in UC2A sample 20.5 mg/kg and in UC2B sample 20.7 mg/kg. On the other hands, there were fluctuations in Zn concentration. Lowest Zn concentrations were observed in controls of tomatoes 20.4 mg/kg and 21.4 mg/kg UC1 and UC2 samples respectively. Zn content was increased during storage; on 10th day in UC1A sample 24.7 mg/kg and on 16th day in UC1B sample Zn content was 22.4 mg/kg. Tomato samples kept in 4 °C for storage study have also increase in Zn concentration i.e. in UC2A sample22.4 mg/kg and in UC2B sample 22.5 mg/kg on 16th day of storage. 20 cultivars of S. lycopersicum L. and 10 wild relatives were analysed for mineral (Na, K, Ca, Mg)and trace elements (Cu, Fe, Zn, Mn) content (Fernández-Ruiz et al. 2011). Heavy metal contents, oil and micronutrients were analysed in tomato seeds and (Lycopersicon esculentum) fruits from Turkish resources; 1.98 -2.41 mg/kg Fe content and 64.8-78.4 mg/kg Zn content (dry weight basis) was found in different tomato samples (Demirbas 2010).