Role of capping agent on structure, composition and optical properties of ZnO nano-thin films for antibacterial activities

Abstract

In this study, rice extract mediated Zinc Oxide nano thin films were successfully synthesized from Zinc precursors through an eco-friendly, sustainable, and economical method. The synthesized ZnO nano thin films were thoroughly characterized using various analytical and spectroscopic techniques. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the synthesized samples with a hexagonal wurtzite crystal structure. The undoped ZnO nano thin films predominantly exhibited the (101) plane, while the rice extract mediated ZnO nano thin films showed a preferred orientation along the (002) plane. The average crystallite size of the sample was estimated to be around 50 nm by XRD analysis. Scanning electron microscopy represent the needle-like structures with improved uniformity on addition 1.5 g rice extract mediated- ZnO thin films. Energy dispersive X-ray analysis proceeds composition of elements presents in the samples. Ultra violet visible spectroscopic measurements showed the shift in value of band gap in between 3.03 and 2.98 eV. Antibacterial studies against Escherichia coli demonstrated a gradual improvement in activity with increasing rice content, with ZOI of 13.33 ± 0.33 mm at 1.5 g mediated thin film. Similarly, enhanced inhibition was observed against Staphylococcus aureus, with the 1.5 g sample showing ZOI of 16.67 ± 0.88 mm.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1038/s41598-026-57467-5.

Introduction

A synthesis approach that utilizes natural materials as biotemplates to fabricate micro and nanoscale materials exhibiting structural and morphologies features analogous to those of the original biological template is known as biomorphic mineralization¹. Such studies continue to expand, contributing significantly to the emergence of a new interdisciplinary field focused on the synthesis, self-assembly, and processing of structurally organized inorganic materials². The use of biotemplates offers several advantages, including low cost, economic feasibility, environmental friendliness, and renewability^3,4. The application of metal oxides thin films synthesized using such biotemplates has garnered increasing attention due to their enhanced structural, optical, and catalytic properties derived from the biological morphology. Among these materials, zinc oxide (ZnO) nano thin films have attracted exceptional interest because of their unique physical and chemical characteristics, along with their versatile applications in numerous technological and industrial fields^5,6. Zinc oxide (ZnO) is a versatile, environmentally kind, and biocompatible semiconductor that has attracted considerable research interest for its outstanding optical and electrical properties. Its wide band gap of 3.37 eV and high exciton binding energy of 60 meV make it an ideal material for the wide range of applications⁷. ZnO and ZnO based materials hold significant potential in the field of nanomedicine, where precise interaction and targeted treatment at the molecular level are essential.

The bio-inspired synthesis of ZnO nano thin films has been successfully accomplished using environmentally sustainable and eco-friendly approaches. Numerous studies have explored the use of natural materials as green templates or reducing agents for ZnO nano thin films preparation^8,9. The biological sources such as silk, albumen, orange juice, pea starch, and peptide structures, more others act as capping agent. These natural systems not only reduce the environmental impact but also enable controlled morphology and enhanced functional properties of the material. Rice, an abundant agricultural resource, can serve as a non-metallic bio precursor for synthesizing functional materials. Its primary component, starch, is a versatile biopolymer composed of linear amylose and branched amylopectin chains derived from glucose units. Therefore, employing rice as a soft bio-template offers a promising and sustainable approach for the synthesis of zinc oxide nano thin films. In recent years, numerous physical and chemical approaches have been employed for the synthesis of ZnO, such as thermal evaporation, pulsed laser deposition (PLD), ion implantation, reactive electron beam evaporation, thermal decomposition, and the sol-gel process. Antimicrobial agents, originating from either natural or synthetic sources, act by restricting microbial growth. Many heavy metals and metal oxides, even at very low concentrations, exhibit strong toxicity toward microorganism¹⁰. These inorganic materials exert their antibacterial effects through multiple mechanisms, including binding to intracellular proteins and disrupting their functions, generating reactive oxygen species (ROS), and causing direct damage to microbial cell membranes. Zinc oxide (ZnO), copper oxide (CuO), magnesium oxide (MgO), and titanium dioxide (TiO₂) are among the most widely utilized inorganic materials for developing antimicrobial coatings¹¹. Zinc oxide (ZnO) exhibits strong antibacterial properties, largely attributed to its capacity to generate reactive oxygen species that impair microbial cell components. Additionally, the controlled release of Zn²⁺ ions de-stabilizes bacterial membranes and interrupts essential metabolic functions, ultimately causing cell death. ZnO is effective against a wide range of microorganisms, including both gram-positive and gram-negative bacteria. ZnO nanoparticles synthesized via a green method using Saccharomyces cerevisiae which exhibited spherical morphology confirmed through SEM analysis. The biogenic ZnO NPs showed strong antibacterial activity (higher against S. aureus) and achieved 83% photocatalytic degradation of Eriochrome Black T under UV light, highlighting their potential in wastewater treatment¹². Green-synthesized ZnO nanoparticles synthesized using ginger extract showed tunable morphology (nanoflakes to flower-like structures), and band gap (3.09–3.38 eV) depending on extract concentration, with optimal surface area at 10 mL. The prepared ZnO NPs demonstrated enhanced photocatalytic degradation of methylene blue (up to 83%) under acidic conditions, indicating their potential for treating acidic wastewater and industrial effluents¹³. Green synthesis of ZnO nanoparticles using Ganoderma lucidum extract produced pure wurtzite-phase nanostructures (~ 3.24 eV band gap) with varied hexagonal morphologies (discs, rods, pyramids). The biosynthesized ZnO NPs significantly enhanced plant growth of Lepidium sativum, demonstrating their potential application as an eco-friendly nano fertilizer¹³. Green-synthesized ZnO nanoparticles using Lupinus albus and Lupinus pilosus extracts exhibited good crystallinity and were stabilized by phytochemicals such as phenols and alkaloids. The ZnO NPs showed effective antibacterial activity and moderate photocatalytic degradation of methylene blue (47–61%), indicating their potential for environmental and biomedical applications¹⁴.

From the literature survey, it is evident that various natural sources have been widely employed as green synthesis agents. However, to the best of our knowledge, only a limited number of studies have reported the use of rice (Oryza sativa) as a green capping agent. Therefore, the novelty of the present work lies in utilizing rice as a natural capping agent to enhance the antibacterial activity. In this present work, the rice extract mediated ZnO nano-thin films were fabricated by simple SILAR technique. The synthesized samples were analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX) to determine their structural, morphological, and compositional characteristics, respectively. Additionally, UV-Visible spectroscopy was employed to investigate their optical properties. Furthermore, the antibacterial efficacy of the prepared samples was evaluated using the disc diffusion method to assess their ability to inhibit bacterial growth.

Materials and methods

Materials

Analytical grade Zinc Chloride (ZnCl₂) and Sodium Hydroxide (NaOH) were procured from Sigma-Aldrich, while commercially available rice grains were used as a natural capping agent.

Method

Preparation of rice extract

The 0.5 g, 1.5 g and 3 g of rice grains were washed and soaked in distilled water separately for one hour. Then, each concentration of soaked rice was grinded separately using mortar and pestle to make slurry. The obtained slurry was transferred into beaker containing 50 ml of distilled water and heated upto 80 °C for 15 min and allowed to settle in room temperature. The boiled extract was filtered and 10 ml of filtered rice extract utilized as capping agent. This 10 ml of capping agent has been added to anionic solution, then, the general SILAR technique is employed. This method is carried out for each concentration of rice to obtain rice extract mediated ZnO thin films were obtained.

Preparation of pure ZnO nano thin films

The microscopic glass slides were used as substrate with dimension of 7.5 × 2.5 cm and thickness of 1 mm for the preparation of thin films. The glass substrates were cleaned using chromic acid to remove organic contaminants and enhance surface wettability, followed by thorough rinsing with distilled water. Subsequently, ultrasonication in ethanol was performed to eliminate residual impurities, and the substrates were dried prior to SILAR deposition to ensure uniform film growth and good adhesion¹¹. The pristine ZnO thin films were successfully synthesized via the SILAR technique. The deposition bath comprised 0.1 M of ZnCl₂ and NaOH solutions, prepared in 100 mL of distilled water, serving as cationic and anionic precursors, respectively. The pH of the cationic solution was carefully adjusted to 9.0 ± 0.1 and maintained under optimized conditions throughout the deposition process to ensure controlled growth of the films. In the first dipping step, the glass substrates were immersed in the zinc bath maintained at ~ 35°C for one minute, allowing ion adsorption on the substrate surface. The substrates were then immersed in boiled water maintained at 90–95 °C for hydrogenation. Then, the dried substrate is immersed in anionic solution, followed by rinsing in boiling water and drying for 30 s. The process was repeated for 25 number of cycles to obtain pristine ZnO nano thin films¹⁵. The general dipping process through SILAR method is illustrated in Fig. 1.

Fig. 1.

Schematic representation of rice capped ZnO nano thin films synthesized via SILAR method.

Preparation of rice extract mediated- ZnO nano thin films

The rice extract is prepared as mentioned in Sect. 2.2.1. Then, the 10 ml of capping agent is added to Zinc solution, the solution is stirred to obtain homogeneous mixture. The deposition bath comprised, 0.1 M of ZnCl₂ (rice extract capped) and NaOH solutions, prepared in 100 mL of distilled water, serving as cationic and anionic precursors, respectively. In the first dipping step, the glass substrates were immersed in the zinc bath maintained at ~ 35 °C for one minute, allowing ion adsorption on the substrate surface. The substrates were then immersed in boiled water maintained at 90–95 °C for hydrogenation. Then, the dried substrate is immersed in anionic solution, followed by rinsing in boiling water and drying for 30 s. The process was repeated for 25 number of cycles to obtain rice mediated ZnO nano thin films.

Characterization

Structural identification was recorded using XRD (Brucker D8 X-ray diffractometer) with Cu Kα1 wavelength exposure 1.546 Ǻ in the 2θ range 30 and 60 with step increment 0.02°. The elemental composition and concentration of the samples were examined using Energy dispersive X-ray (EDX) spectroscopy in conjunction with a Scanning Electron Microscope ((INPECT-F Model, 30 kV). The percentage of transmittance in the samples were studied using Shimadzu Ultra Violet visible 1800 in the wavelength range 200 nm and 1000 nm.

Results and discussion

Film thickness

The growth rate and deposition behavior of pristine ZnO and rice extract mediated ZnO nano thin films on microscopic glass substrates were influenced by key parameters such as film thickness and surface morphology. The method of weight difference is used to find out thickness of the deposited films using the given Eq. (1),

1

Here, W₁, W₂, A and ρ are weight of the substrate before and after deposition, Area of the substrate and density of the ZnO¹⁶. The relationship between film thickness, and deposition time, for pure ZnO and rice extract mediated ZnO films on glass substrates is illustrated in Fig. 2.

Fig. 2.

Variation of film thickness with respect to time for pristine ZnO and rice capped ZnO nano thin films.

Xray diffraction

The structure, phase composition, and crystalline arrangement of the ZnO and rice extract capped ZnO nano-thin films were analyzed using X-ray diffraction (XRD). The XRD patterns of pure ZnO and rice extract-mediated ZnO films prepared with varying concentrations of the capping agent (rice) are presented in Fig. 3. The diffraction peaks of all samples closely matched those of pure ZnO, which can be indexed to the hexagonal wurtzite structure. The formation of single-phase hexagonal ZnO was confirmed by comparing the obtained diffraction data with the standard JCPDS card No. 36-1451¹⁷. The characteristic diffraction peaks appeared at 2θ values of 31.82°, 35.36°, 36.32°, 47.6°, and 56.7°, corresponding to the lattice planes (100), (002), (101), (102), and (110) respectively. The sharp and intense diffraction peaks indicate the high crystallinity of the synthesized films, with all samples exhibiting the typical wurtzite structure of ZnO. Table 1 displays the crystallographic information about ZnO in detail. No additional peaks related to the rice extract capping agent were observed, even at higher concentrations, suggesting that the rice components did not introduce any secondary crystalline phase¹⁸. Therefore, the use of rice as a biotemplates can facilitate the synthesis of highly pure ZnO particles. This observation aligns with earlier findings reported by Ramimoghadam et al., where uncooked rice acted as an effective capping template through the Ostwald ripening mechanism, controlling the crystal growth rate beyond a certain concentration. It is noted that from the XRD profile, the interplanar spacing d_hkl is calculated using Bragg’s relation Eq. (2)

Fig. 3.

X-ray diffraction pattern of pristine ZnO and rice capped ZnO nano thin at various concentration.

Table 1.

Crystallographic data of Zinc oxide showing lattice parameters, space group, and unit cell details of the hexagonal wurtzite structure.

S. No	Parameters	Value
1	Mineral name	Zincite
2	Compound name	Zinc oxide
3	Chemical formula	ZnO
4	Crystal system	Hexagonal
5	Space group	P63mc
6	Phases	Stochiometric; ZnO
		Non Stochiometric; ZnO2
7	Space group number	186
8	Lattice parameter (a)	3.2498
9	Lattice parameter (b)	3.2498
10	Lattice parameter (c)	5.2066
11	Alpha (°)	90
12	Beta (°)	90
13	Gamma (°)	120
14	Volume (Å)3	47.62

2

where λ is wavelength of X-rays, d is the lattice spacing, n is the order number, θ is the Bragg’s diffraction angle¹⁹. The factor ‘d’ with its relation to (hkl) plane, the dimension of the unit cell. The crystallite size and dislocation density of the ZnO, rice extract ZnO nano-thin films was calculated by following Debye Scherrer formula using FWHM data observed from x-ray diffraction profile mentioned in Eqs. (3) & (4) and displayed in Table 2. Crystallite size represents the average size of crystalline domains formed on the surface of the substrate.

Table 2.

Structural parameters calculated for Pure and rice extract mediated ZnO at different concentration.

Samples	Concentration	2θ	d spacing	Crystallite size (nm)	Dislocation density	Volume
ZnO	–	36.2	2.47	16.38	0.00037	47.32
Rice capped ZnO-1	0.5 g	36.2	2.46	40.24	0.00061	47.29
Rice capped ZnO-2	1.5 g	36.3	2.45	20.7	0.00023	47.32
Rice capped ZnO-3	3 g	36.3	2.43	51.5	0.00037	47.31

3

Where λ, β, and θ indicates the wavelength, FWHM and diffraction pattern of the prepared sample. Dislocation density represents the concentration of dislocation lines distributed within a crystal per unit volume. The volume of a unit cell represents the spatial region enclosed by the fundamental repeating structural unit of a crystal. The volume of unit cell is calculated using the Eq. 5.

4

5

Thus, the XRD pattern confirms the successful formation of a highly crystalline, phase-pure material with no detectable impurities.

Scanning electron microscopy

Scanning Electron Microscopy (SEM) is an analytical technique that employs a focused beam of electrons to scan the surface of a specimen, generating high-resolution images that reveal detailed surface morphology and microstructural features²⁰. Figure 4a,b shows SEM images of ZnO and 1.5 g of rice- extract mediated ZnO samples, revealing significant morphological evolution with modification. The pure ZnO (Fig. 4a) exhibits agglomerated, irregular granular structures, whereas the rice mediated ZnO nano thin films (Fig. 4b) displays well-defined needle-like structures with improved uniformity. This transformation indicates that the incorporation of the rice extract promotes anisotropic growth and enhances surface area, which is beneficial for functional applications²¹. The corresponding EDX spectra displayed in Fig. 5a,b presents the EDX spectra confirming the elemental composition of the samples. The spectra reveal the presence of Zn and O as dominant elements, indicating the successful formation of ZnO, while other spectra show an additional C signal attributed to carbon molecules from rice extract²². The inset table indicates the atomic (%) and weight (%) of ZnO and rice extract mediated ZnO nano thin films obtained from EDX analysis, respectively.

Fig. 4.

(a, b) SEM photographs of pure ZnO and rice (1.5 g) extract mediated ZnO nano thin films.

Fig. 5.

(a, b) EDX spectra of pure ZnO and rice (1.5 g) extract mediated ZnO nano thin films.

UV-Visible spectroscopy

The optical absorbance of pure ZnO and rice-extract mediated ZnO nano thin films are examined through UV-Visible spectroscopy displayed in Fig. 6a. The optical transmittance was measured in the wavelength range of 200–800 nm to understand the influence of the rice extract on the optical behavior of the ZnO thin films, shown in Fig. 6b²². As shown in the transmittance spectra, the rice extract (3 g) mediated ZnO thin film exhibits comparatively lower transmittance throughout the visible and near-infrared regions. This reduced transparency can be attributed to the higher density of surface defects and possible scattering centres present in the pristine ZnO film²³. A sharp increase in transmittance is observed around 350–450 nm, indicating the optical transition region of ZnO. The presence of organic compounds in the rice extract likely acts as a natural stabilizer and growth-directing agent, facilitating the formation of smaller and more uniformly distributed nano thin films, which leads to reduced light scattering²⁴. Direct band gap is calculated for the prepared rice capped ZnO thin films by utilizing the Eqs. (6) & (7) from the absorbance spectra.

Fig. 6.

UV-visible spectroscopy (a) Absorbance (b) Transmittance (c) Tauc plot.

6

7

8

Here t (1 cm), and T represents the thickness and transmittance (%) of prepared thin films.

9

Here, A and t indicate the absorbance and thickness of the prepared thin films. The Tauc plots shown in Fig. 6c were used to estimate the optical band gap, which decreases from 3.03 to 2.95, 2.91 and 2.85 for pure ZnO to each concentration of rice extract mediated ZnO thin films, respectively. The R² value and fitted Equation is given in the Table 3. This gradual decrease suggests modification in the electronic structure, likely due to defect regulation and interaction with capping agents. It can be related to the dislocation density, where dislocation density is the measure of crystallographic defects. As the dislocation density increases on addition of rice extract, the band gap decreases. This clearly indicates that increase in crystallographic defects, reduces the band gap of the prepared thinfilms²⁵. The band gap of the material is obtained by extending the linear portion of the graph to intersect the hν (X-axis). The decrease in band gap energy with higher capping agent concentration suggests that the rice biomolecules effectively change the nucleation and growth of ZnO nano thin films²⁶. Figure 7a–c illustrates the optical properties of pure and capped ZnO samples at different concentrations. Figure 7a depicts the absorption coefficient (α), which decreases with increasing wavelength, confirming strong absorption in the lower wavelength (UV-visible) region calculated using Eq. (9). The absorption coefficient shows strong absorption in the UV region with a sharp absorption edge around 300–380 nm, confirming the direct bandgap nature of ZnO. The absorption increases with dopant concentration, with the 3 g sample exhibiting high value, indicating enhanced photon absorption due to defect-induced electronic transitions. Refractive index (n) is one of the basic properties of semiconductors which is calculated by Swanepoel method displayed in Eq. (10). The variation in refractive index (n) with wavelength, is presented in Fig. 7b, shows an increasing trend with increasing wavelength in the UV region for all samples, indicating normal dispersion behavior. Notably, the refractive index increases with increasing concentration, due to modifications in electronic structure and lattice distortion caused by incorporation of capping agent.

Table 3.

Fitted equation from UV analysis.

Parameter	Pure ZnO	0.5 g rice extract capped ZnO	1.5 g rice extract capped ZnO	3 g rice extract capped ZnO
R2	0.88	0.87	0.88	0.89
Fitted equation	−4.03 + 1.23x	−3.64 + 1.24x	−2.89 + 0.92x	−2.50 + 0.84x

Fig. 7.

Optical constants (a) Absorption coefficient (α) (b) Refractive index (n) (c) Extinction coefficient (k).

10

The extinction coefficient (k) states that the portion of light related to scattering and absorption in the medium of penetration and calculated by absorption coefficient method using the Eq. (11).

11

Similarly, the extinction coefficient (k) shown in Fig. 7c follows a gradual decrease with increasing wavelength after 400 nm, consistent with reduced optical losses at higher wavelengths. The higher k values for rice mediated ZnO samples further indicate increased light-matter interaction due to structural and compositional modifications [27]. Moreover, the organic constituents in the rice extract increases defect states, particularly oxygen vacancies, thereby minimizing localized electronic states within the band gap. This results in improved optical transparency and a slight widening of the band gap.

Antibacterial activity

The disc diffusion method is a standardized antimicrobial test that measures zones of inhibition by placing discs impregnated with agents over an agar plate that has been infected with bacteria displayed in Fig. 8. The disc diffusion method was used to evaluate the antibacterial activity of pure ZnO nano thin films, rice extract-capped ZnO. By using two bacteria such as Escherichia coli (E. coli) as Gram-negative bacteria and Staphylococcus aureus (S. aureus) as Gram-positive bacteria, the antibacterial activity was carried out. The bacterial culture was maintained at a concentration of 10⁸ CFU/mL and uniformly spread on nutrient agar plates. Sterile discs with a diameter of 90 mm were used, onto which ZnO nanoparticles were applied at a concentration of 30 µg/mL. The experiments were performed in triplicate to ensure the reliability and reproducibility of the results^22,23. This improvement of antibacterial property in rice mediated ZnO nano thin films reflects the role of rice extract containing phytochemicals. The functional groups such as polyphenols, proteins, and carbohydrates present in rice extract may act synergistically with ZnO, promoting enhanced ROS formation and stronger binding interactions with bacterial cell walls. For E. coli, the pristine ZnO sample exhibited a moderate zone of inhibition (ZOI) of 11 ± 2.08 mm, confirming its inherent antibacterial activity. A slight change in activity was observed for the 0.5 g of rice mediated ZnO sample with ZOI of 11.67 ± 0.33 mm. With increasing concentration to 1.5 g of rice, the antibacterial performance was improved, as evidenced by the ZOI of 13.33 ± 0.33 mm suggesting that an increase in loading enhances antibacterial efficiency, likely due to the availability of more active sites. A moderate inhibition was recorded for the 3 g sample with ZOI of 12.6 ± 1.86 mm, but increased antibacterial efficiency than pure ZnO thin films. A comparable analysis was carried out for S. aureus, where it shows slight variation in magnitude of ZOI. The ZnO sample showed a ZOI of 12.33 ± 0.33 mm, while the 0.5 g sample exhibited improved activity with ZOI of 13.33 ± 0.33 mm. The 1.5 g sample demonstrated the better antibacterial effect than the other samples, with a maximum inhibition zone of 16.67 ± 0.88 mm. However, a slight decline was noted at higher concentration (3 g), where the inhibition zone decreased to 14.67 ± 0.33 mm^24,25. The consistent high inhibition zone observed for rice mediated thin films indicates that the capped films have stable properties, which is important for achieving reliable and repeatable biological results. The detailed Mean, standard deviation (SD), and standard error (SE) is analysed for the both antibacterial assays and tabulated in Tables 4 and 5 for three number of replicates. Therefore, the results confirm rice extract-capped ZnO as a high potential in antibacterial activity with stronger inhibition performance than pure ZnO highlighting its real-world applications in field of biomedical and antimicrobial.

Fig. 8.

Antibacterial assays of (a, b) Pristine and rice extract (0.5,1.5 and 3 g) mediated ZnO against E. coli (c, d) Pristine and rice extract (0.5,1.5 and 3 g) mediated ZnO against S. aureus bacteria.

Table 4.

Zone of inhibition (mm) and other parameters of ZnO and rice mediated ZnO samples against E. coli.

E. coli
Sample	Zone of inhibition (Mean)	SD	SE
ZnO	11	1	0.58
0.5 g rice extract mediated ZnO	11.6	0.58	0.33
1.5 g rice extract mediated ZnO	13.3	0.58	0.33
3 g rice extract mediated ZnO	12.6	0.58	0.33

Table 5.

Zone of inhibition (mm) and other parameters of ZnO and rice mediated ZnO samples against S. aureus.

S. aureus
Sample	Zone of inhibition (Mean)	SD	SE
ZnO	12.3	0.58	0.33
0.5 g rice extract mediated ZnO	13.3	0.58	0.33
1.5 g rice extract mediated ZnO	16.6	1.53	0.88
3 g rice extract mediated ZnO	14.6	0.58	0.33

Conclusion

This work demonstrates the successful and eco-friendly synthesis of pristine and rice extract-capped ZnO nano thin films using zinc precursors. Structural analysis confirmed a hexagonal wurtzite phase with a rice extract-induced shift from the (101) to the (002) orientation and average crystallite size around 50 nm. The SEM analysis reveals that, the pure ZnO exhibits agglomerated and irregular granular morphology, while rice-mediated ZnO thin films showed well-defined needle-like structures with improved uniformity, indicating enhanced surface characteristics. The optical band gap was found to decrease with rice extract concentration, from 3.03 to 2.85 eV confirming the influence of capping on electronic properties. Antibacterial studies against Escherichia coli demonstrated a gradual improvement in activity with increasing rice content, with ZOI of 13.33 ± 0.33 mm at 1.5 g mediated thin film. Similarly, enhanced inhibition was observed against Staphylococcus aureus, with the 1.5 g sample showing ZOI of 16.67 ± 0.88 mm. These findings highlight the effectiveness of rice extract as a green capping agent for enhancing functional performance.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary Material 1 ^{(157.5KB, pdf)}

Author contributions

1. Ms. Ravi Renuka Devi (1st author): Formal analysis; Data curation; Resources; Software; Validation; Investigation; Writing—original draft. 2. Dr. Chelladurai Amutha (2nd author): Conceptualization; Data curation; Formal analysis; Methodology; Resources; Software; Visualization; Writing—original draft. 3. Dr. Gokul Paramasivam (3rd author): Software; Data curation; Data analysis. 4. Dr.Sethuramachandran Thanikaikarasan (Corresponding Author) : Conceptualization; Investigation; Methodology; Supervision; Visualization; Project adminstration—Writing—review & Editing. 5. Dr.Rajkumar Sivanraju (Corresponding Author): Validation; Visualization; Writing—review & Editing.

Data availability

Data availability all data generated or analyzed during the study are included in the submitted manuscript.

Declarations

Competing interests

The authors declare no competing interests.