Facile Synthesis of Nanocomposite ZnO and Red Betel (Piper crocatum Ruiz & Pav)

Green synthesis of zinc oxide nanoparticles is one of the most widely conducted research nowadays. The need for a facile and environmental synthesis method for nanomaterial is something interesting to develop. Red betel, which is a typical Indonesian herbal plant and abundant to find, has a phytochemicals property that potential application for bioreductors and capping agents. In this study, experiments were carried out with the aim of green synthesize nanocomposite ZnO-red betel leaves and studying their properties. The obtained powder was characterized with Fourier-Transform Infrared Spectroscopy, Scanning Electron Microscope, and Energy Dispersive X-ray Spectroscopy. The results showed that the obtained sample is ZnO nanoparticles with uneven surfaces with diameter < 100 nm.


Introduction
Nanotechnology has been researched extensively since 21 st century focusing on the manipulation of incredibly small particles known as nanoparticles, nanocrystals, and nanocomposites.Nanocomposites, a category of materials comprising two or more constituents, with at least one at the nanometer scale, stand apart from conventional composites.Their diminutive size offers multiple benefits, including heightened physical sensitivity and improved chemical reactivity.Some common types of nanocomposites are polymer nanocomposites, ceramic nanocomposites, and metal matrix nanocomposites.Nanocomposites have been applied in various fields such as architecture, construction, telecommunications, and biomedicine [1,2].The development and application of nanocomposites, integrating both metal oxides and biological compounds, hold promising potential across diverse fields.
Various methods like sol-gel, microwave, and precipitation have been employed for nanocomposite synthesis.However, these techniques carry adverse environmental consequences, prompting the need for an eco-friendly alternative known as green synthesis [2].Green synthesis is widely favored due to its environmentally friendly, cost-effective nature, and often utilizing plant components as agents for nanoparticle formation.Stabilizers are crucial in this process to prevent nanoparticle agglomeration, which can take the form of surfactants, polymer molecules, or polymer molecules bonded to nanoparticles [2,3,4].
Several researches about ZnO nanoparticle green synthesis have been utilizing several parts of plants, such as orange peel, lychee peel, and ginger root [2,5,6].From the previous researches, ZnO is known as a metal oxide that has strong beneficial properties, such as good antibacterial and antidiabetic activity, biocompatibility, and wide band gap [6,7].This prodigious properties has led to ZnO nanoparticle application in solar cell, dye removal, nanogenerator, biosensor, etc [7].
Indonesia, a country rich in biodiversity, holds significant potential for developing various bioreduction agents, catalysts, stabilizers, and buffers for green synthesis.Among the natural materials with potential as bioreductors is the Piperaceae family, specifically the red betel (Piper crocatum Ruiz & Pav).Red betel contains a lot of phytochemical components such as phenolic compounds, terpene, fand flavonoid [8].It also has rich heritage in traditional medicine, where it has been utilized for a wide range of purposes.These include managing conditions like high blood pressure, liver inflammation, prostate inflammation, breast cancer, joint discomfort, regulating blood sugar, cosmetic applications, addressing heart issues, treating bone tuberculosis and acting as an antiseptic to combat skin or wound infections, including those caused by Candida albicans [9].
ZnO-red betel leaves nanocomposite was expected to combine their good properties without eliminating red betel's leaf function as reductor and capping agent.This combination has potential application, mainly in biomedicine, dye-removal, and sunscreen.In this study, we synthesized ZnO-red betel leaf nanocomposite using a green approach that involved utilization of red betel leaf.The characterization of the ZnO nanoparticles employed several techniques such as fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS).These characterizations were performed to observe the presence of functional groups and covalent bonds in the sample, examine the morphology of the sample, and analyze the elements present in the sample.

Methodology
Methodology that was used in this experiment is referred to Thi et al. work, but has several modification [2].First of all, the plant preparation was done by maceration method [10].Initially, red betel leaves were washed two times with tap water and once with aqua dm to remove the dirt.Then, 6 grams of red betel was boiled in 150 mL aqua dm for 8 minutes.The solution obtained was cooled until reached room temperature.Afterwards, it was filtered using Whatmann no.1 filter paper to remove the remaining leaf pieces.
Next step is synthesizing ZnO-red betel nanocomposites.4.46 grams of Zn(NO3).H2O was mixed in 150 mL red betel that was prepared before for an hour.The solution then was heated for an hour at 60 o C. NaOH was used to add the pH of solution until it reached pH 7. The sample then was centrifugated for 15 minutes at 3500 rpm to separate the supernatant liquid and pellet.Then, the pellet was washed by aqua dm several times and then dried for 90 minutes in 220 o C. The products were characterized further as explained in the next section.
Characterization was done to study the characteristics of ZnO-red betel nanocomposite.FTIR study was done by Bruker FTIR Spectrophotometer and the range of scanning was set from 4000 to 500 cm - 1 .SEM and EDS characterization were done using SU 3500 Hitachi.SEM analysis was done with 15000 to 50000 magnifications to study the morphology of sample.Meanwhile, EDS was used to analyze elements component in the sample.

Result and Discussion
Figure 1.FTIR spectra of ZnO-red betel nanocomposite.
FTIR spectrum of ZnO-red betel nanocomposite is showed in Figure 1.It reveals several significant fingerprints.Firstly, a prominent band at 3427 cm -1 is attributed to OH group vibrations, primarily due to the adsorption of water molecules [11].Additionally, the peaks at 911 cm -1 are associated with internally bonded C-H stretching, as reported in reference [12].Furthermore, the vibrational stretching occurring in the range of 400-750 cm -1 signifies the presence of ZnO [11].In the current research study, the infrared spectra demonstrated a distinctive zinc oxide absorption band with a stretching mode observed between 500 cm −1 to 590 cm −1 .This particular band corresponds to the E2 form of hexagonal ZnO wurtzite crystal lattice structure [13].Moreover, bands within the range of 3000-3650 cm −1 are attributed to the reversible dissociative absorption of hydrogen on both Zn and O sites, as well as a band at 1600 cm −1 , signifying N-H bending vibrations of amine or amide groups.Vijayalakshmi's study suggests that the peaks observed at 1400 and 1629 cm⁻¹ are associated with the stretching vibrations of symmetric and asymmetric C=O bands [14].Sachin's research similarly asserts that these frequencies, specifically 1400 and 1629 cm⁻¹, signify the primary and secondary amines present in proteins or enzymes, as well as the C-OH stretching of phenolic compounds in the extract [5].  Figure 2 shows morphology of green synthesized ZnO-red betel nanocomposites analyzed by SEM.It reveals that the majority of particles exhibit a spherical shape with an irregular surface.Upon zooming in at a magnification of 15,000 times, it becomes apparent that there is clustering of particles, hindering their separation.Qualitative analysis done using ImageJ at 50,000 times magnification image reveals that the particles size distribution in the sample is not homogenous.They are 98.58 nm in average of particle size.Apart from agglomeration and inhomogenous particle size, the images indicate that particles maintain a consistent form, and the uniformity of nanoparticles is crucial for their various functions [6].The efficacy of nanoparticles in combating infections strongly correlates with their structure [5].Specifically, spherical nanoparticles display significant antibacterial capabilities due to their ability to readily infiltrate pathogen cell walls [5].According to Sachin et al, the structure of ZnO NPs shows promise as effective agents for eliminating dyes from wastewater [5].Element analysis was done via EDS characterization and the results can be seen in Figure 3 and Table 1.The data shows that ZnO metal oxide was formed with Zn and O at 65.43% and 34.57% atomic weight respectively.Their weight % is 11.45% for O and 88.55% for Zn.Meanwhile, two unlabeled-small peaks indicate the existence of C and Si.These elements came from the red betel leaves extract.It confirms that ZnO-red betel nanocomposite was successfully synthesized by green synthesis route.This result agreed with Faisal result which use ginger root extracts in the green synthesis process [6].

Conclusion
The green synthesis method has effectively produced the ZnO-red betel nanocomposite.It is offering a straightforward, cost-effective, and environmentally conscious approach.This nanocomposite possesses a reduced particle size and displays a rounded, spherical form with an uneven surface.Further characterization can be conducted to investigate the crystal structure and antibacterial activity of the nanocomposite.

Figure 2 .
Figure 2. SEM image of ZnO-red betel nanocomposite with a) 15,000 and b) 50,000 times magnification.

Table 1 .
List of elements in the sample.