Green Synthesis of Zinc Oxide Particles Using Cladophora glomerata L. (Kütz) Extract: Comparative Study of Crystal Structure, Surface Chemistry, and Antimicrobial Efficacy with Different Zinc Precursors

Abstract

This study examined the eco-friendly synthesis of zinc oxide (ZnO) nanoparticles using Cladophora glomerata extracts as reducing and stabilizing agents, comparing zinc acetate and zinc chloride precursors for biomedical and environmental applications. Zinc acetate-synthesized ZnO nanoparticles showed a significant absorption peak around 320–330 nm, indicating stable, quasi-spherical ZnO nanoparticles with a narrow size distribution, primarily around 100 nm. Zeta potential measurements revealed a value of −25 mV for these particles, suggesting moderate colloidal stability. XRD analysis confirmed a highly crystalline hexagonal wurtzite structure for zinc acetate-derived ZnO, and SEM images supported a proper microstructure with approximately 2 µm particle size. FTIR analysis indicated higher-quality ZnO from zinc acetate due to the absence of moisture and hydroxyl groups. Conversely, zinc chloride-derived ZnO particles displayed a broader absorption spectrum around 370 nm, indicative of significant aggregation. Their narrower zeta potential distribution around +10 mV suggested diminished colloidal stability and a heightened aggregation tendency. While a peak around 100 nm was observed, many particles exceeded 1000 nm, reaching up to 10,000 nm. XRD results showed that zinc chloride adversely affected crystallinity, and SEM analysis indicated smaller particles (approx. 1 µm). FTIR analysis demonstrated that zinc chloride samples retained hydroxyl groups. Both zinc acetate- and zinc chloride-derived ZnO nanoparticles produced notable inhibitory zones against Gram-positive (L. monocytogenes, S. aureus) and specific Gram-negative bacteria (E. coli, K. pneumoniae). Zinc acetate-derived ZnO showed a 21 mm inhibitory zone against P. vulgaris, while zinc chloride-derived ZnO showed a 10.1 mm inhibitory zone against C. albicans. Notably, zinc chloride-derived ZnO exhibited broad-spectrum antimicrobial activity. MIC readings indicated that zinc acetate-derived ZnO had better antibacterial properties at lower concentrations, such as 3.125 µg/mL against L. monocytogenes. These findings emphasize that the precursor material selection critically influences particle characteristics, including optical properties, surface charge, and colloidal stability.

1. Introduction

Due to its unique physicochemical properties, zinc oxide (ZnO) has become a significant material in various fields such as biomedicine, agriculture, food safety, and environmental sustainability. Its low toxicity, biocompatibility, and cost-effectiveness make it highly valuable for drug delivery, antimicrobial treatments, and cancer therapy applications [1]. Particularly in cancer treatment, ZnO can deliver chemotherapeutic drugs directly to tumor cells, reducing side effects and enhancing treatment efficacy. Additionally, its antibacterial properties enable it to combat multidrug-resistant bacteria, making it useful in agriculture, food safety, and industry. ZnO also contributes to technological advancements by being utilized in catalysis, optoelectronic devices, and orthopedic implants, where its ability to modify surfaces without compromising mechanical strength is a significant advantage.

However, using ZnO is challenging, as concerns about potential toxicity and environmental impacts persist. Studies indicate that high doses or prolonged exposure can harm various bodily systems, including the neurological and lymphatic systems [2]. Furthermore, its stability in different environments can influence its effectiveness, necessitating further research to optimize its application and minimize risks. While ZnO offers numerous benefits across multiple domains, balancing its advantages with addressing potential health and ecological concerns remains critical for its continued development and safe use.

The biosynthesis of ZnO using plant and algae extracts represents a green and eco-friendly approach that leverages the reducing and stabilizing properties of phytochemicals present in plants. Plant extracts are rich in a variety of phytochemicals, such as flavonoids, polyphenols, terpenoids, and proteins, which can effectively reduce metal ions to their respective nanoparticles [3]. The use of plant extracts not only minimizes the need for toxic chemicals but also enhances the biocompatibility and stability of the synthesized nanoparticles.

Several key parameters influence the stabilization of zinc oxide (ZnO) during synthesis. The zinc precursor’s concentration directly affects the nanoparticles’ size and morphology, as higher concentrations may lead to larger particles or irregular shapes [4]. Additionally, the pH and temperature of the reaction environment play critical roles in controlling nucleation and growth processes. For instance, acidic or alkaline conditions can alter the reaction kinetics, while elevated temperatures may accelerate particle formation. Reaction time is another crucial factor, as longer durations can enhance crystallinity but may also increase particle size. Optimizing these parameters—precursor concentration, pH, temperature, and reaction time—is essential to achieve stable, well-defined ZnO with desired properties [5]. Once synthesized, ZnO is characterized using advanced analytical techniques to confirm their structure and properties. UV–Vis spectroscopy is employed to verify the formation of ZnO by detecting its characteristic surface plasmon resonance. X-ray diffraction (XRD) analysis reveals the nanoparticles’ crystalline structure and phase purity. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) provide detailed insights into particle morphology, size distribution, and surface features. Fourier transform infrared spectroscopy (FTIR) identifies functional groups in the stabilizing agents (e.g., plant extracts) and confirms their interaction with the ZnO surface. Together, these techniques ensure a comprehensive evaluation of the nanoparticles’ physicochemical characteristics, ensuring their suitability for targeted applications.

Different types of plants such as aloe vera, green tea, and medicinal herbs (e.g., neem, basil) serve as natural reducing and stabilizing agents in ZnO nanoparticle synthesis [6]. Aloe vera’s phytochemicals enhance nanoparticle stability and antimicrobial activity, while green tea’s polyphenols boost antibacterial efficacy for food and biomedical applications. Medicinal herbs provide sustainable, natural compounds that facilitate zinc ion reduction and nanoparticle stabilization, highlighting their versatility in green synthesis.

Both micro- and macroalgae present unique benefits in the biosynthesis of ZnO [7,8]. Microalgae are typically easier to culture in controlled environments, while macroalgae can provide higher yields of biomass and bioactive compounds. Microalgae, such as Spirogyra, have been widely studied for their role in the biosynthesis of ZnO. The biosynthesis of ZnO using micro- and macroalgae represents a sustainable and eco-friendly approach to nanoparticle production. Spirulina platensis is known for its nutritional value, Spirulina has also been explored for ZnO production [9]. The biosynthesis occurs through the interaction of zinc salts with the algal extract, forming nanoparticles with potential applications in antimicrobial and drug delivery systems. Nannochloropsis spp. microalgae are used for the green synthesis of ZnO. The biosynthesis process involves the utilization of cell extracts that promote the conversion of zinc ions into ZnO, which exhibits unique optical and antibacterial properties [10]. These examples illustrate the diverse potential of microalgae in the eco-friendly biosynthesis of ZnO, highlighting their role in sustainable nanotechnology.

The synthesis of zinc oxide (ZnO) using plant extracts is influenced by the choice of plant species, which significantly impacts the nanoparticles’ properties and applications [11]. A literature review reveals that different kinds of zinc precursors can be employed for the synthesis of ZnO particles. In fact, zinc acetate and zinc chloride which have been concentrated as important initial materials for the synthesis of oxides, can be effectively employed for the successful synthesis of ZnO. Different plants produce ZnO with varying sizes, shapes, and morphologies due to the unique phytochemicals in their extracts, which regulate nucleation and growth processes. The stability of the nanoparticles is also affected by plant-specific stabilizing agents like polysaccharides and proteins, which control dispersion and agglomeration [12]. Optical properties, such as UV absorption and photoluminescence, differ based on the plant’s phytochemical profile, altering their suitability for photonic or photoprotective uses. Antimicrobial efficacy also varies, with certain plant extracts enhancing antibacterial or antifungal activity through bioactive compounds. Additionally, the chemical composition and surface charge (zeta potential) of ZnO depend on the plant source, which influences its reactivity, biocompatibility, and performance in catalysis, drug delivery, or environmental remediation [13]. Thus, selecting the appropriate plant species is critical for tailoring ZnO to specific applications.

A comprehensive literature review conducted using PubMed, Scopus, and Web of Science revealed no studies on the green synthesis of ZnO nanoparticles using Cladophora glomerata extract with zinc acetate or zinc chloride as precursors. While other algal species, such as Spirulina platensis and Sargassum muticum, have been explored for ZnO synthesis [8,9], the use of C. glomerata, a widely available macroalga, remains unreported. This study addresses this gap by evaluating the impact of these precursors on ZnO properties and antimicrobial efficacy.

2. Material and Methods

2.1. Material

The Cladophora glomerata used in the experiments was obtained from Karkamış Dam Lake in Şanliurfa, Turkey. Deionized water (D.I. 2H₂O) was used for all experiments. Zinc nitrate hexahydrate [Zn(NO₃)₂·6H₂O] and zinc acetate [Zn(CH₃CO₂)₂·2H₂O] were purchased from Sigma-Aldrich (Taufkirchen, Germany). After collecting from nature, C. glomerata samples were washed with tap and deionized water and dried. The dried samples were then ground into a fine powder to ensure maximum surface area for the extraction process, which was carried out using a solvent extraction method with deionized water at controlled temperatures. The extract was then filtered to remove any particulate matter, and the resulting solution was concentrated through evaporation to obtain a more potent extract suitable for further analysis.

2.2. Method

We directly applied previous methods from ZnO synthesis studies [14]. Zinc acetate dihydrate (Zn(Ac)2·2H₂O) and zinc chloride (ZnCl₂) were selected as precursors due to their prevalent use in green synthesis and their distinct anionic properties, which influence nanoparticle characteristics [4,15]. Phytochemicals (e.g., polyphenols, polysaccharides) in the C. glomerata extract act as reducing agents to convert Zn²⁺ to Zn⁰ clusters, followed by oxidation to ZnO, and also serve as capping/stabilizing agents. For the extract preparation, 10 g dry algae powder (Cladophora glomerata) was boiled in 100 mL deionized water for 60 min at 100 °C. After that, the extract was cooled to room temperature and filtered using filter paper (Whatman No. 1) to remove large temperatures. The extract was saved in a refrigerator at 4 °C for subsequent experiments. Stoichiometrically, 5.0 g Zn(Ac)₂·2H₂O (22.7 mmol Zn²⁺) or 3.1 g ZnCl₂ (22.7 mmol Zn²⁺) was reacted with 50 mL of C. glomerata extract (equivalent to 5 g dry algae powder). To begin, 5 g Zn(Ac)2·2H₂O was mixed in 50 mL of the extract under vigorous stirring at 100 °C until the solvent (H₂O) was removed entirely, and then, it was annealed at 400 °C for 30 min. Finally, a ZnO sample was obtained in powder form. For the number 2 samples, ZnCl₂ (anhydrous) was used as a precursor. All other processes are the same.

2.3. Characterization

Results of [16] were used to determine the biochemical content of C. glomerata. The properties of the obtained zinc oxide (ZnO) samples were meticulously characterized to explore their structural, morphological, electrical, and optical characteristics using a series of advanced analytical techniques. Specifically, the structural attributes, such as the crystal phase and crystallite size, were thoroughly analyzed using X-ray diffraction (XRD) with a Bruker AXS D8 diffractometer (Bruker AXS, Karlruhe, Germany). UV–Vis spectroscopy of synthesized ZnO NPs was measured using a Shimadzu UV1800 spectrophotometer (Shimadzu Corp., Kyoto, Japan). Dynamic light scattering (DLS) was applied to evaluate the size distribution of the prepared nanoparticles. The surface charges were measured using Zeta potential analyzer (Malvern Nano ZS90, Malvern Pananaltical, Malvern, UK). The samples were carefully visualized using field emission-scanning electron microscopy (FE-SEM) (ZEISS GEMINI 500, ZEISS, Oberkochen, Germany) employing a Zeiss Ultra Plus Gemini instrument, which offered high-resolution imaging of the particle surfaces. FTIR analysis was conducted to determine the Zn-O bonds and any organic molecules or impurities attached to the particle surface during synthesis. Additionally, the optical properties, including the ultraviolet–visible absorption spectra and the optical band gap energy, were precisely determined using a UV–visible spectrophotometer (Rayleigh UV-2601, Beijing Rayleigh Analytical Instrument Co., Ltd., Beijing, China). Beyond these comprehensive characterizations, the antimicrobial activity of ZnO was also investigated to assess its effectiveness against microbial organisms, highlighting its potential in biomedical applications.

2.4. Antimicrobial Activity

2.4.1. Preparation of Culture Media

Müller Hinton Agar (MHA) and Müller Hinton Broth (MHB) were prepared as follows: MHA contained 2.0 g/L meat extract, 17.5 g/L casein hydrolysate, 1.5 g/L starch, and 17.0 g/L agar, while MHB was composed of 2.0 g/L meat extract, 17.5 g/L casein hydrolysate, and 1.5 g/L starch. Both media were sterilized by autoclaving at 121 °C for 15 min and cooled to approximately 50 °C before use.

2.4.2. Antimicrobial Activity Assays

Antimicrobial efficacy was assessed using the agar well diffusion method. Vancomycin (10 µg) was used as a positive control due to its established efficacy against Gram-positive bacteria, providing a benchmark for ZnO nanoparticle activity. Briefly, 100 µL of standardized bacterial suspensions were spread on MHA plates. Wells (6 mm diameter) were punched into the agar, and 50 µL of test samples were added to each well. Plates were incubated at 35 °C for 24 h, after which inhibition zones were measured to determine antimicrobial activity [17]. For the agar well diffusion assay, 50 µL of ZnO nanoparticle suspensions (100 µg/mL) were added to 6 mm wells in MHA plates seeded with 100 µL of standardized bacterial suspensions. A single concentration was used to screen for antimicrobial activity, with dose-response relationships further evaluated using the MIC assay.

2.4.3. Minimum Inhibitory Concentration (MIC) Determination

MIC values were determined using the broth microdilution method in 96-well plates. [18]. For the agar well diffusion assay, 50 µL of ZnO nanoparticle suspensions (100 µg/mL) were added to 6 mm wells in MHA plates seeded with 100 µL of standardized bacterial suspensions. A single concentration was used to screen for antimicrobial activity, with dose-response relationships further evaluated using the MIC assay. Serial twofold dilutions of test samples were prepared in MHB across wells 1–12 of the plate. A bacterial suspension (100 µL, McFarland 0.5) was added to each well, and plates were incubated at 37 °C for 24 h. Negative controls (wells containing only MHB and bacteria) and sterility controls (MHB without bacteria) were included. Following incubation, 20 µL of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) solution was added to each well. After 1 h of incubation at 37 °C, colorimetric changes were assessed: purple wells indicated bacterial growth, while clear wells signified inhibition. The MIC was defined as the lowest concentration of the test sample that prevented visible growth (no color change).

3. Results and Discussion

Figure 1 shows the experimental results obtained from the characterization of zinc particles synthesized using C. glomerata algal extract with either zinc acetate (Zn-Ac) or zinc chloride (ZnCl) as precursors. The analysis encompassed absorbance spectroscopy, zeta potential measurements, and dynamic light scattering (DLS) for particle size distribution. UV–Vis absorbance spectra revealed distinct profiles for particles synthesized with different precursors. For particles derived from the Zn-Ac precursor, a prominent absorption peak was observed at approximately 320–330 nm. This peak is characteristic of zinc oxide (ZnO) nanoparticles, often associated with exciton absorption near the band edge [19]. ZnCl precursor exhibited a broader absorption profile with a higher intensity around 370 nm. The differences in peak position and intensity suggest variations in the electronic structure, average particle size, and/or morphology influenced by the precursor type. Particles synthesized with the Zn-Ac precursor displayed a broad zeta potential distribution with a prominent peak centered around −25 mV. This negative zeta potential indicates moderate colloidal stability, likely due to the adsorption of negatively charged biomolecules from the algal extract onto the particle surface [20]. ZnCl precursor showed a narrower zeta potential distribution with a peak observed around +10 mV. This positive zeta potential, being closer to neutrality, suggests lower colloidal stability and a higher propensity for aggregation. For particles synthesized with the Zn-Ac precursor, the size distribution showed a primary peak around 100 nm, with a broader distribution extending up to approximately 1000 nm. This indicates a relatively uniform population of nanoparticles, albeit with some larger aggregates. ZnCl precursor was considerably broader and notably shifted toward larger sizes. While a peak around 100 nm was discernible, a substantial population of particles extended well beyond 1000 nm, reaching up to 10,000 nm. This indicates extensive aggregation and a highly polydisperse sample, consistent with its lower absolute zeta potential and reduced colloidal stability [21].

Figure 2 shows the XRD spectra of the synthesized ZnO by employing zinc acetate and zinc chloride. It is interestingly seen that the use of zinc acetate results in the production of well-crystallized material, while the utilization of zinc chloride leads to the suppression of crystallinity [15]. Herein, the obtained XRD spectrum related to zinc acetate is in good agreement with JCPDS No. 00-001-1136 1136 with a hexagonal crystal structure. Accordingly, it is seen that the main diffractions are attributed to (002) and (101) planes in the 2θ of 34.5 and 36.4. Furthermore, the crystal structure obtained is hexagonal, while the correlated space group is P63mc. The lattice parameters of the hexagonal crystal structure of the introduced XRD pattern are 3.24, 3.24, and 5.17 Å. Given that the crystallinity of the synthesized oxides plays a vital role in their professional applications, one can expect that for the proper synthesis of ZnO, the consumption of zinc acetate may be more concentrated than that of zinc chloride. The findings suggest that optimizing the synthesis conditions, particularly the choice of precursor, can significantly enhance the material properties of ZnO, thereby improving their efficacy in various biomedical applications. This optimization impacts the structural integrity of the nanoparticles and influences their optical and electrical properties, which are crucial for applications in drug delivery, photodetection, and catalysis.

Figure 3a shows the SEM microstructures of the synthesized materials. Utilizing zinc acetate leads to the formation of ZnO with an approximate particle size of 2 μm. In addition, it is easily concluded that the produced ZnO powder possesses proper microstructure with a narrow particle size distribution. A literature review reveals that synthesizing uniform microstructure has been concentrated by many researchers because of their excellent optical properties [22,23,24]. In other words, the preparation of non-uniform microstructures as well as agglomeration of particles lead to the suppression of their optical characteristics. The EDX characterization shows that the synthesized production mainly consists of Zn and O elements (see Figure 3b). Meanwhile, Figure 3c demonstrates that using zinc chloride leads to the formation of smaller particle size (about 1 μm). At the same time, the EDX analysis shows that the synthesized product possesses a similar chemical composition (see Figure 3d).

To study the surface chemistry of the synthesized compounds, FTIR analysis was used at room temperature (see Figure 4). A literature survey demonstrates that the bands at 416 and 490 cm^–1 are related to the tensile bond and the oxygen vacancies of ZnO, respectively [25]. Meanwhile, the peak at 540 cm⁻¹ originates from zinc-oxygen (Zn-O) stretching vibration mode. Herein, the mentioned firm peaks confirm the successful formation of the ZnO phase. In addition, the peaks at 1032 and 1632 cm⁻¹ correspond to the bending vibration of C–H and the bending vibration of water molecules, respectively. Finally, the chemisorbed hydroxyl (O–H) group on the synthesized ZnO is confirmed by the broad and strong band at 3438 cm⁻¹ [26]. Given that this band cannot be observed with the utilization of zinc acetate, one can expect that using zinc acetate results in higher quality of ZnO. In other words, the existence of moisture and hydroxyl groups on the surface of oxide materials weakens their optical behavior. As a matter of fact, it can be easily concluded that similar to what was explained for the XRD results, the explained synthesis approach was useful to produce well-crystallized ZnO using zinc acetate.

While this study focused on structural and morphological characterizations, future investigations could incorporate zeta potential and dynamic light scattering (DLS) analyses to evaluate the colloidal stability and dispersion behavior of ZnO nanoparticles in suspension, which are critical for optimizing their biomedical applications.

In this study, antimicrobial activities of C. glomerata extract and zinc acetate- and zinc chloride-derived ZnO nanoparticles were evaluated by testing on various microorganisms (

Table 1. Comparison of antimicrobial activity of C. glomerata extract and zinc oxide particles (acetate/chloride source).

Microorganism	C. glomerata Extract	Zinc Acetate–Precursored ZnO— Inhibition Zone (mm)	Zinc Chloride–Precursored ZnO—Inhibition Zone (mm)	Vancomycin (10 μg)
B. subtilis	-	14.5 ± 2.12	12.2 ± 4.1	8 ± 1.4
E. coli	-	14.5 ± 3.5	14 ± 3.1	-
E. aerogenes	-	10.5 ± 0.71	12.2 ± 2.11	-
K. pneumoniae	-	11.0 ± 1.41	13.8 ± 2.1	-
L. monocytogenes	-	18.5 ± 4.95	20.1 ± 3.9	-
P. vulgaris	-	21 ± 1.41 *	24.2 ± 2.5 *	-
S. aureus	-	11.5 ± 0.71	12.8 ± 4.9	12 ± 0.00
C. albicans	-	-	10.1 ± 2.5	-
C. parap	-	-	-	-

-: No inhibition. *: 6 mm hole diameter included in inhibition zones.

). C. glomerata extract failed to show an inhibitory effect on all microorganisms tested, suggesting that the antimicrobial potential of the extract might be limited. Vancomycin was selected as a control antibiotic due to its efficacy against Gram-positive bacteria, such as S. aureus and B. subtilis. Future studies could incorporate additional antibiotics, such as ampicillin or gentamicin, to provide broader benchmarking across Gram-negative and fungal strains. In contrast, zinc acetate- and zinc chloride-derived ZnO materials formed effective inhibitory zones against Gram-positive bacteria (L. monocytogenes, S. aureus) and some Gram-negative bacteria (E. coli, K. pneumoniae). For example, zinc acetate-derived ZnO exhibited a 21 mm inhibitory zone against P. vulgaris, and zinc chloride derived ZnO exhibited a 10.1 mm inhibitory zone against C. albicans [27]. Vancomycin was only effective against Gram-positive bacteria (S. aureus: 12 mm) and was ineffective against Gram-negative bacteria and fungi. Zinc chloride-derived ZnO stood out with its broad-spectrum antimicrobial activity, while all substances were useless on the C. parap fungal strain, indicating that the strain may be resistant. In general, ZnO materials offer promising potential for antimicrobial applications [28]. The agar well diffusion assay utilized a single concentration (100 µg/mL) to confirm antimicrobial activity, while the MIC assay provided detailed dose–response data. Future studies could incorporate multiple concentrations in the diffusion assay to further elucidate concentration-dependent effects.

MIC values of compounds found to be effective against bacteria in the agar diffusion method were determined with the microdilution method using 96-well plates (see Figure 5). The agar well diffusion assay utilized a single concentration (100 µg/mL) to confirm antimicrobial activity, while the MIC assay provided detailed dose–response data.

Table 2. Minimum inhibitory concentration (MIC) and dose–response relationship according to bacterial strains.

Concentrations (ppm)	L. monocytogenes ATCC 19115	E. coli ATCC 25922	E. aerogenes ATCC 13048	P. vulgaris ATCC 8427	B. subtilis ATCC 29213	K. pneumonia ATCC 13883	S. aureus ATCC 25923
100	-	-	-	-	-	-	-
50	-	-	-	-	-	-	-
25	-	+	-	+	+	-	+
12.5	-	+	+	+	+	+	+
6.25	-	+	+	+	+	+	+
3125	-	+	+	+	+	+	+
1.56	+	+	+	+	+	+	+
0.78	+	+	+	+	+	+	+
0.39	+	+	+	+	+	+	+
0.19	+	+	+	+	+	+	+
0.09	+	+	+	+	+	+	+
0.045	+	+	+	+	+	+	+

gives the minimum inhibitory values (µgml⁻¹) of tested compounds against bacteria. Zinc acetate–precursored ZnO was effective against L. monocytogenes with a MIC = 3.125 (µg ml⁻¹); E. coli, P. vulgaris, B. subtilis, and S. aureus from the tested microorganisms with a MIC = 50 (µg ml⁻¹); and against K. pneumonia and E. aerogenes with a MIC = 25 (µg ml⁻¹). Findings suggest the substance may be effective at low concentrations through cell wall permeability or target molecule interaction. Still, its mechanism of action is limited or non-toxic at high doses [29]. Future studies could incorporate multiple concentrations in the diffusion assay to further elucidate concentration-dependent effects.

4. Conclusions

This investigation elucidates the practical, environmentally friendly synthesis of ZnO particles utilizing Cladophora glomerata extract as both a reducing and stabilizing agent while systematically comparing the impacts of zinc acetate and zinc chloride precursors. Results obtained from absorption studies showed that Zn-Ac-derived particles suggest the formation of relatively stable, quasi-spherical ZnO nanoparticles. In addition, ZnCl-derived particles indicated extensive aggregation and potentially anisotropic morphologies like rods, as suggested by previous research on zinc chloride precursors. Structural characterization conducted using XRD analysis has shown that ZnO synthesized from zinc acetate exhibited a highly crystallized hexagonal wurtzite structure with superior crystallinity, in contrast to ZnO produced from zinc chloride, which presented diminished crystallinity and reduced particle sizes. SEM and FTIR corroborated the successful formation of ZnO with negligible organic remnants; however, samples derived from zinc chloride were noted to retain hydroxyl groups, which may potentially alter their surface chemistry. Antimicrobial evaluations underscored the effectiveness of both ZnO variants against Gram-positive and Gram-negative bacterial strains, with nanoparticles synthesized from zinc chloride demonstrating an extended range of activity, particularly against Candida albicans. Nonetheless, neither precursor proved effective against C. parap, reflecting strain-specific resistance. The reduced MIC values associated with zinc acetate-derived ZnO indicate a heightened antibacterial efficacy at lower concentrations. These results show us that the promise of C. glomerata reduced ZnO synthesis for applications in biomedicine and environmental science while also highlighting the necessity for further refinement of precursor selection and synthesis conditions to bolster stability, mitigate toxicity, and delve into the mechanistic underpinnings of antimicrobial activity. The choice of precursor critically dictates the final particle properties, including optical characteristics, surface charge, and colloidal stability. The distinct chemical properties of zinc acetate and zinc chloride, coupled with their unique interactions with the reducing and capping agents present in the C. glomerata extract, leads to varying nucleation and growth pathways.