Synthesis and Characterization of the Chitosan Silver Nanoparticle-Reinforced Borassus flabellifer Trichome- and Prosopis juliflora Wood-Based Nanocomposite for Environmental Application

Department of Information Technology, VR Siddhartha Engineering College, Kanuru, Vijayawada, Andhra Pradesh 520007, India Department of Information Technology, Gudlavalleru Engineering College, Gudlavaleru, Andhra Pradesh 521356, India Department of ECE, Institute of Aeronautical Engineering, Dundigal, 500043 Telangana, India Department of Computer Science, Kombolcha Institute of Technology, Wollo University, P.O. Box 208, Ethiopia


Introduction
Wood is a wide natural reusable material which is important in different industries making the researchers to work on it [1]. The naturally existing porous wood acts as a good carrier to build a functional composite that is still rarely used. Nanotechnology is a promising area to enhance the efficiency and effectiveness towards different bioremediation processes. Its improved reactivity and increased surface area to volume ratio had great impact when compared with those bulk materials [2]. The physical characteristic of chitosan is its flexibility, and studies regarding its properties have been performed and the outcome is very positive [3]. This latest material has its durability, biodegradability, biocompatibility, nontoxicity, and adsorption in pharmaceuticals, agriculture, forestry, skincare products, and food and water treatment applications. Still, it is emerging as an innovator in textiles, health care and pharmaceuticals [4].
In India, the palmyra tree is the official tree of Tamil Nadu. In tradition, it is called askarpaha, a celestial tree, nudged and extremely cherished by the people, and considered a god [5]. Borassus flabellifer includes innumerable essential constituents, gums, fats, albuminoids, carbohydrates were investigated [6]. Silver nanoparticles are considered to have a strong and wide range of therapeutic applications, and even low concentration of silver nanoparticles has been found, in some cases, to possess strong potential to treat a variety of diseases [7]. A nanocomposite is one of the unusual composite materials that are shown to possess a capability of being used as a biometric sensor as well as in numerous treatment protocols. Silver nanoparticle (AgNP) incorporation has a great impact on the water purification process due to its stability, chemical catalytic ability, low toxicity to humans, and effective antimicrobial property [8].
The present investigation strongly focused on the preparation and characterization of the Borassus flabellifer trichome and Prosopis juliflora wood, silver nanoparticles (AgNPs), and chitosan with different proportions by UVvisible spectroscopic analysis, FTIR analysis, and SEM analysis.

Materials and Methodology
2.1. Chemicals and Samples. From Sigma-Aldrich Chemical Company, USA, the required fine chemicals like silver nitrate were purchased and all other requirements are of first-class analytical grade.

Preparation of Chitosan Solution (Ch).
The purified chitosan was significantly obtained by performing alkaline deacetylation of chitin from crab shells. The mixture was obtained by dissolving 1 gram of chitosan in 100 ml of 0.25 N hydrochloric acid.

Preparation of the Borassus flabellifer
Trichome-Chitosan Biocomposite (TC-Ch). In 50 ml double distilled water, 1 g of Borassus flabellifer trichome and 1% chitosan (Ch) were mixed to this solution [9]. The pH of the solutions was adjusted to 7.0, and the resultant materials were used for further use. It was denoted as TC-Ch [10].

Preparation of Silver Nanoparticle (AgNP) Solution.
Silver nanoparticles were prepared by using a modified method of Turkevich. In brief, 30 ml of 1 mM silver nitrate solution was boiled and kept in a magnetic stirrer. Once it starts to boil, add 3 ml of 10 mM trisodium citrate in the ratio of one drop per second and wait till it change into brown color. Finally, it is denoted as AgNPs [11].
2.5. Preparation of the Wood Sample (W). The wood pieces were collected from Prosopis juliflora, and the hardwood of the plant was finely powdered. The obtained finely powdered wood sample was collected, and it is denoted as W [12].

Incorporation of AgNPs and W into the TC-Ch
Biocomposites (TC-Ch-AgNPs-W). The prepared TC-Ch biocomposite was soaked in solution having 0.01% of AgNPs and wood sample for about 24 hrs. Silver nanoparticle-(AgNP-) and wood-integrated TC-Ch was taken and dried at 37°C [13]. The obtained material was expressed as TC-Ch-Ag-W.

UV-Visible Spectrometric Analysis.
A UV-visible spectrum was obtained for different samples observed using a UV-visible spectrophotometry analysis for authentication of availability of the desired/formed molecule. The deionized water was used as a blank.
2.9. FTIR Analysis. IR provides significant data on the rotational and vibrational motion of the specific molecules, and it improves the effective identification and characterizations of the obtained composite interactions evaluated under FTIR to observe structural conformation [15]. All the required measurements were carried out in the range of 400 to 4000 cm −1 .

Morphology
Observation. The morphological experiment was performed for TC-Ch-AgNPs and TC-Ch-AgNPs-W by using a JEOL JSM-7401F scanning electron microscope.

Result and Discussion
From the present investigation, Prosopis juliflora wood (W), Borassus flabellifer trichome (TC), silver nanoparticles (AgNPs), and chitosan (Ch) with incorporation of TC-AgNP, TC-W, TC-Ch, TC-Ch-AgNP, and TC-Ch-AgNP-W composites have been prepared by a modified method of the available literature and were systematically partially characterized by UV spectroscopy, FTIR spectroscopy, and SEM analysis, and the obtained results were interpreted with the available literature.
The UV-visible spectroscopy analysis for TC, W, Ch, and AgNPs is represented in Figure 1 with the absorptive peak at 282 nm, 285 nm, 320 nm, and 400 nm in the UV region.
The UV-visible spectroscopy analysis was performed for TC-W, TC-Ch, and TC-AgNPs and is represented in Figure 2. Here, Borassus flabellifer trichomes (TC) act as a base for Ch, W, and AgNPs. From the obtained results, the absorptive peak was observed at 280 nmin in all three different compositions [17].
The biocomposites TC-Ch-AgNPs and TC-Ch-AGNPs-W were subjected to UV-visible spectroscopy analysis to determine the optical property which is represented in Figure 3. It indicated that TC-Ch-AgNPs is not showing any absorptive peak and TC-Ch-AGNPs-W exhibits a peak at 300 nm [18].
From Figure 3, it represents that when four different components (TC, Ch, AgNPs, and W) were mixed, the interaction between one and other molecules with the 1 : 1 ratio has been successfully achieved to form a single bionanomaterial [19]. From the above results, the absorptive peak confirmed that TC acts as a base for the incorporation of Ch, AgNPs, and W. The FTIR spectroscopic analysis was performed, and the characteristic peak was obtained in the range between 4000 and 500 cm −1 . The obtained results are presented in Figures 4-6, and they were interpreted with the available literature [20]. For the chief functional groups for chitosan, a characteristic peak was obtained at 3500 to 3300 cm −1 and was attributed to the O-H group of vibrational spreads. Figure 4 shows the FTIR spectroscopy analysis for TC, W, Ch, and AgNPs. The C-H bending vibration of the alkyl group and the N-  3 Journal of Nanomaterials [21]. The 1400-600 cm -1 area has a peculiar pattern of absorption in this region, which is often called a region of fingerprinting because the fingerprints of an individual are unique. Carboxylic acids, amines, and compounds are responsible for hydroxy replacements.
The characteristic FTIR analysis exhibits the TC peak as the parameter went up in 3500 cm -1 , the chitosan molecule shifted to 3000 cm -1 , and a simple O-H stretching vibration was observed, attributable to the NH stretching of the main functional group. Figure 5 shows the FTIR spectroscopy analysis for TC-W, TC-Ch, and TC-AgNPs. The presence of absorption peaks at 1750 to 1.5 to 3.5H to 15.5 cm -1 was triggered by the stretching of the N-protonated amino group and alkyl-group bending from 17.5 to 18.5 cm to 19.5 ppm. When the remaining amide groups have a bond stretching intensity of intermolecular bonds, the groups have an N-H vibration at a frequency of 1663.5 cm -1 , and when intermolecular bonds are involved, it is at 1500 cm -1 . The amide I peak at 1429.9 cm -1 , IH2N deformation, 1451.1 cm -1 , and 14.2 cm -1 NH 2 is given a lifetime of 79 μs which is long [22]. The absorption peak occurs at 1405-680 cm -1 due to the asymmetric vibration of the C-O-C bonds in the chitosan matrix and is interpreted as a glucosyl group due to the glucose rings.
For all three samples, TC-AgNPs, TC-W, and TC-Ch, the characteristic FTIR analysis shows the most similar peak with minor alteration. The three peaks at 3500 to 3000 cm -1 were expressed having the main functional group of chitosan, which are due to the O-H group of stretching vibrations. The N-H bending vibration of the protonated amino group and C-H bending express the alkyl groups that are responsible for the peaks at 1750 to 1500 cm -1 . At 1663.5 cm -1 and 1500 cm -1 and 1659.5 cm -1 , respectively, the existing amide frequencies consist of the remaining acetamido groups' -C-O bond stretch and the N-H bending vibrations of the -NH 2 groups. -NH 2 deformation is responsible for the peaks at 1429.9 cm -1 , 1451.1 cm -1 , 1418.2 cm -1 , and 1419.1 cm -1 .
The characteristic FTIR analysis ( Figure 6) shows that TC-Ch-AgNPs and TC-Ch-AGNPs-W show most similar peaks with slight modification. The changes were observed that TC-Ch-AgNPs peak was sharp compared then TC-Ch-AgNPs peak, and it was expressed that there was a formation of strong peak with a précised functional group at the peak which represented the above proportions.

Conclusion
The present investigation of UV and FTIR characteristic peaks was obtained for TC, Ch, W, TC-AgNPs, TC-W, TC-Ch, TC-Ch-AgNPs, and TC-Ch-AGNPs-W. The UV spectroscopic results expressed a significant peak confirming the presence of molecules. From the FTIR graph, the different functional groups were observed, and it was confirmed that the improved and strong peak was in TC-Ch-AGNPs-W. The SEM images for TC-Ch-AgNPs and TC-Ch-AGNPs-W improved the surface area scanning electron microscopic investigation. It shows the incorporation of Ch and AgNPs to W and TC. The morphograph exhibits fibrous nature with an improved surface area. From the prepared materials, it may have a great impact on the different applications. In addition, it also may offer different bioremediation processes with ecofriendly nature.

Data Availability
The data used to support the findings of this study are included within the article. Should further data or information be required, these are available from the corresponding author upon request.