Synthesis and characterisation of copper (II) oxide nanoparticles for application in antimicrobial coatings

Abstract

The addition of nanoparticles to coatings is a widely employed strategy to enhance resin properties without compromising performance. Copper oxides are commonly used as additives in formulations, replacing organometallics, which are prohibited due to their biocidal and antifouling activities. This study focuses on synthesizing copper (II) oxide nanoparticles through co-precipitation for application in antimicrobial coatings. The synthesis process involved co-precipitation using copper sulphate (CuSO₄.5H₂O) as a precursor and NaOH as an alkaline agent. Characterization of the obtained nanoparticles was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). These analyses confirmed the formation of CuO nanorods with an average size of approximately 73 nm in length and 16 nm in width. Antimicrobial testing was conducted against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus. The results revealed noteworthy antimicrobial activity, particularly against Staphylococcus aureus and Bacillus cereus. Consequently, the findings suggest that copper (II) oxide nanoparticles have the potential to serve as additives, enhancing the biocidal properties of resins as coatings and other applications.

Keywords:
copper (II) oxide; nanoparticles; antibacterial; synthesis

1. Introduction

Nanotechnology has become a focal point in contemporary research, finding applications across diverse sectors, such as bioengineering, pharmaceuticals, agriculture, metallurgy, and materials science (Tomar and Singh, 2023). Inorganic nanoparticles, particularly those made of silver and copper, have gained significant attention for their versatility, high biological activity, and the ease with which their oxides can be obtained (Mohammad and Shyam, 2023; Rivera-Mendoza et al., 2024).

The emergence of new infectious diseases poses a significant challenge to global public health, particularly with mutations in bacterial strains that are resistant to current antibiotics. This is a strong motivation in the search for new antibacterial agents with improved stability and broad inhibitory spectra against multidrug-resistant bacteria (Andualem et al., 2020). Generally, studies associated with antimicrobial activity of inorganic nanoparticles with potential applications in the health sector use Escherichia coli and Staphylococcus aureus as target bacteria because they cause serious illnesses to human health (Flores-Rábago et al., 2023). However, more robust assays should include a greater range of microorganisms to better assess the spectrum of antimicrobial activity (Ahamed et al. 2014).

The copper oxide nanoparticle has high thermal stability and as copper is a transition metal, its oxides have activities that are applicable as a catalyst through oxidation-reduction reactions (Ackerman et al., 2017; Benhadria et al., 2022). These oxides have replaced the toxic organometallic compounds present in coatings, primarily because of their improved biocidal, antifouling, and lower toxicity activities (M El Saeed et al., 2016; Kaningini et al., 2023). In addition to the recognized antimicrobial activities of copper oxide nanoparticles, their potential role as antitumor agents, as well as their antioxidant, antidiabetic, and antiparasitic activities, make them promising candidates for various bio-medical applications (Crisan et al., 2022; Naz et al., 2023; Ivanova et al., 2024).

Copper oxide nanoparticles have been effectively used as antimicrobial agents for the inhibition of both gram-positive and gram-negative bacteria due to their highly ionic chemical characteristics (Ren et al., 2009; Borkow, 2015; Rangel et al., 2020). Copper oxide presents itself in two forms: copper I oxide (Cu₂O) is less stable than copper (II) oxide (CuO) at room temperature, as CuO has a monoclinic crystalline structure, which is more appropriate for biocidal applications (Ananth et al., 2015).

The synthesis of copper (II) oxide nanoparticles can be carried out through several routes, with the chemical reduction of copper salts being the most widely used (Khatoon et al., 2023; Rifani et al., 2023). In this study, the synthesis method by co-precipitation via reduction was selected for its reaction rates at low temperatures, low cost, and generation of easily treated waste.

This study aimed to use a simple and easy synthesis method to physically and chemically characterise CuO nanoparticles, with the ultimate goal of utilizing them as additives in resins for antimicrobial coatings.

2. Materials and methods

2.1 Synthesis method

Copper oxide nanoparticles were prepared using a chemical co-precipitation method with NaOH (Exodo Cientifica, Sumaré, Brazil) as an alkaline reagent, following a modified procedure inspired by Rangel et al. (2020). The precursor solution was 100 mL of 0.1 mol/L copper sulphate (CuSO₄.5H₂O), purchased from Synth (Diadema, Brazil), dissolved in distilled water, contained in a three-necked flask with a rounded bottom, and subjected to constant magnetic stirring. The temperature was raised and maintained at 50 °C. Then, a previously prepared alkaline solution (1.0 mol/L NaOH) was added drop by drop until a volume ratio of 1:1 was obtained. Constant stirring was maintained throughout the experiment, reaching a pH of 14 upon complete addition. The colour of the solution gradually changed from blue to black, indicating the formation of a significant amount of black precipitate. These conditions were maintained for more than 30 min. Following this, the solution with the precipitate was vacuum filtered and washed with distilled water at room temperature. After washing, the precipitate obtained was dried in a vacuum oven (Nova Etica model 440D, Vargem Grande, Brazil) for 3 h at 115 °C, followed by a 3-h treatment in a muffle furnace (EDG Equipamentos model EDG300, São Carlos, Brazil) at 300 °C (Figure 1).

Figure 1
Flowchart of the method used to obtain CuO nanoparticles.

2.2 Characterization

The sample was characterized by X-ray diffraction (XRD) analysis to evaluate the crystalline phases, at the LACOR (Corrosion, Protection and Recycling of Materials Laboratory at UFRGS). The equipment used was a Panalytical Aeris device with copper Kα radiation (λ = 1.54 Å), in the 2θ range of 5°–80°, and at an angular step of 0.02°.

The chemical properties were investigated by Fourier transform infrared spectroscopy (FTIR). Utilizing a Perkin Elmer Spectrum IR Version 10.7.2, the spectrum was obtained by the ATR method in the region between 4000 and 400 cm^-1, with 8 scans and a resolution of 4 cm^-1. Thermogravimetric analysis (TGA) was employed for measuring the mass variation according to temperature. A thermal analyser TA Instruments model Q50 TGA was used, with the samples evaluated in the range from 40 to 940 °C at a heating rate of 20 °C/min under a flowing nitrogen atmosphere of 90 mL/min, utilizing a ceramic sample holder.

The morphology of the material was analyzed at LAPROM (Mineral Processing Laboratory at UFRGS), through scanning electron microscopy (SEM) using a Tescan Vega 3 (Brno, Czeck Republic), with an Oxford EDS detector (Bristol, UK). The samples were pre-coated with gold and the images were obtained at an accelerating voltage of 30 kV.

Transmission electron microscopy (TEM) was performed at the LabMic (High Resolution Microscopy Multiuser Laboratory at UFG). The samples were dispersed in 99.9% ethyl alcohol using an ultrasonic cleaner. An aliquot of the sample was deposited on the copper grid (specifications: copper grid covered with 400 mesh carbon). After drying, the samples were analyzed using a TEM JEOL model JEM-2100 (Tokyo, Japan), equipped with a Thermo Scientific EDS detector (Waltham, MA, USA) operating at 200 kV.

2.3 Antimicrobial activity

The antimicrobial activity was tested at ICTA (Food Science and Technology Institute at UFRGS) using the zone inhibition assay on agar plates (Zehetmeyer et al., 2017). Suspensions of the strains Staphylococcus aureus ATCC1901, Bacillus cereus ATCC9634, Pseudomonas aeruginosa ATCC15442, or Escherichia coli ATCC8739 were prepared in sterile saline from the biomass grown for 24 h at 37 °C on Brain Heart Infusion agar plates (BHI, Oxoid, Basingstoke, UK). These suspensions were adjusted to approximately 10⁷ CFU/mL and spread over fresh BHI agar plates with sterile swabs. Approximately 0.5 g of the sample was placed on BHI plates previously inoculated with the strains. The plates were incubated for 24 h at 37 °C and the assay was carried out in duplicate. The commercial antibiotics ceftibufen (CFB), ciprofloxacin (CIP), cefaclor (CFC), and ampicillin (AMP) were used as positive controls. The antimicrobial activity was evidenced by the presence of clear zones (no growth or survival of microorganisms) around the CuO nanoparticles. The results of the sizes of the inhibition zones were presented as mean ± SD and were statistically evaluated using Analysis of Variance (ANOVA) and the means were compared using the Tukey test.

3. Results

XRD analysis indicated the formation of copper (II) oxide, evident from the characteristic peaks of the mono-clinic crystal structure at around 35° and 38° in the 2θ position (Figure 2). These peaks correspond to the [110] and [111] crystallographic planes, in agreement with JCPDS Standard no. 01-080-0076. The size of the synthesized particles was estimated using the Scherrer equation (Fatimah et al., 2022), using the data referring to the peak of greatest intensity (35°) as a reference. The obtained value was estimated as 36 nm.

Figure 2
XRD analysis of CuO nanoparticles.

The FTIR spectrum (Figure 3) indicates the presence of the –OH bond, as observed in the 3436.11 cm^-1 and 1628.04 cm^-1 bands, which can be attributed to water due to the absorption of humidity from the environment. The bands at 596.4 cm^-1 and 535.7 cm^-1 indicate the stretching of the Cu-O bond.

Figure 3
FTIR spectrum of CuO nanoparticles.

The TGA and DTG thermograms (Figure 4) showed that the CuO nanoparticles present high thermal stability. Low mass loss was observed up to around 700 °C, followed by a DTG degradation peak at approximately 900 °C. This peak is attributed to the conversion of CuO into Cu₂O, which is the most stable phase of copper oxide in this temperature range. This phase presented 89.28% residue, which was predominantly Cu₂O, as inferred from its red color.

Figure 4
TGA and DTG thermograms of CuO nanoparticles.

SEM analysis enabled the observation of small micrometer-scale particles alongside the presence of agglomerates (around 5 μm wide), as observed at two different magnitudes (Figures 5a and 5b). These agglomerates may have formed because of moisture absorbed during sample preparation, as suggested by the analysis of FTIR.

Figure 5
Micrographs of CuO nanoparticles.

TEM analysis confirms the agglomeration of the particles shown in the SEM images but allowing to determine the morphology of the rods. From the TEM images (Figure 6), using ImageJ software, 200 particle width and length measurements were made. Statistical analysis was performed with mean, standard deviation and histogram with normal distribution in the Origin software. The CuO particles were 73 ± 51 nm length and 16 ± 6 nm width.

Figure 6
Micrographs of CuO nanoparticles from TEM 500 nm (a), 100 nm (b).

The distribution of the sample length and width measurements is compatible with the Gaussian distribution (Figure 7). The length measures between 13 nm and 344 nm, but most go up to 100 nm. The width is between 4nm and 54nm and most are between 10 and 20 nm. Therefore, as it has dimensions smaller than 100 nm, we can classify the particle as nanorods.

Figure 7
Size distribution analysis of the synthesized CuO nanoparticles.

In the antimicrobial tests, inhibition was observed around the nanoparticles in all strains of bacteria tested, namely Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus (Table 1).

Table 1
Inhibition diameter (mm) of the positive controls and the CuO nanoparticles in the tested microorganisms. Results expressed as means ± SD.

Microorganism	Positive control	Inhibition diameter (mm)
		Positive control	CuO nanoparticle
Escherichia coli	CFB	22.05 ± 0.23*	27.81 ± 2.88 *
Pseudomonas aeruginosa	CIP	45.15 ± 0.47**	36.27 ± 0.78 **
Staphylococcus aureus	CFC	8.46 ± 0.51**	31.73 ± 0.45**
Bacillus cereus	AMP	9.50 ± 0.63**	22.89 ± 2.32**

• Comparison of means between positive control and nanoparticles of CuO * Tukey Test (p<0.05) ** Tukey Test (p < 0.01). CFB, ceftibufen; CIP, ciprofloxacin; CFC, cefaclor; AMP, ampicillin.

4. Discussion

The nanoparticles produced by the co-precipitation method using a CuSO₄ precursor solution and a NaOH reducing solution comply with methodological expectations, as corroborated by previous results from crystallographic analysis and scanning electron microscopy. Selvaraj (2022) conducted a similar chemical synthesis, utilizing a copper chloride (CuCl₂) as the precursor solution and NaOH as a reducing solution, with the addition of Poly(ethylene glycol) 600 (PEG 600) as a stabilizing agent. XRD analysis indicated a prominent localized peak around 39°, corresponding to particles with a size of approximately 36 nm according to Scherrer’s equation.

Likewise, FTIR results were similar to those obtained by Phiwdang et al. (2013) and Selvaraj (2022) in the synthesis of CuO nanoparticles using CuCl₂ as a precursor solution. However, it is worth mentioning that in the present study, the reaction was carried out with an excess of reducing solution to ensure complete consumption of the precursor solution. This is in accordance with the methodology proposed by Rangel et al. (2020), albeit with a slight change in oven temperature (from 80 to 115 °C). In addition, a muffle calcination step at 300 °C for 3 h was included to obtain smaller particles, as higher temperatures tend to stabilize the crystallinity of the copper (II) oxide. The use of the muffle furnace at 300 °C did not degrade the obtained nanoparticles, as demonstrated by TGA, which is rarely mentioned in nanoparticle characterization analyses.

In this study, the TGA methodology was based on the protocol from Rangel et al. (2020), who also noticed the phase change from copper (II) oxide to copper (I) oxide. They observed an increase in mass loss above 800 °C, with a degradation peak around 900 °C for both nanoparticles obtained with CuCl₂ and CuSO₄ precursor solutions, aligning with the results of the present study.

The SEM images showed a good dispersion of CuO nanoparticles, despite the presence of agglomerates, consistent with the results obtained by Phiwdang et al. (2013). Khatoon et al. (2023), who utilized copper nitrate (Cu(NO₃)₂) as a precursor solution in varying concentrations with different reducing agents, described the presence of agglomerates only when the concentration of the precursor solution was above 0.1 mol/L, regardless of which reducing agent was used. It appears that the co-precipitation method leads to the formation of these agglomerated particles, irrespective of the salt used in the precursor solution. However, the SEM micrographs from this work indicate a small number of agglomerates, rendering their application in coatings feasible.

The results obtained from transmission electron microscopy images (TEM) corroborate the XRD results, which indicate that the synthesized particle is on a nanometric scale. However, according to Hassanzadeh-Tabrizi (2023), it is common for the size measured by the XRD peak to be smaller than that observed in the transmission electron microscopy images. As the calculation using the Scherrer equation does not consider information about the size distribution of the crystallite, making the TEM technique with images in dark field mode more suitable for measuring the average particle size. The results obtained were similar to those presented by Kumar and Chowdhury (2017) and Qamar et al., (2020) that synthesized CuO particles were in a monoclinic rod-shaped pattern with an average width of 10nm and 60nm respectively. However, in both studies, the lengths were greater than that found in this study.

It is important that coatings containing an antimicrobial additive are effective against a broad spectrum of microorganisms. Therefore, tests using gram-positive and gram-negative bacteria are essential for evaluating the quality of biocidal formulations. Gram-positive bacteria have a thicker peptidoglycan layer compared to gram-negative bacteria, but gram-negative bacteria have lipopolysaccharides, lipoproteins, and phospholipids, which externally surround the cell wall (Zhou et al. 2022). In this study, the gram-positive bacteria S. aureus and B. cereus, as well as the gram-negative bacteria E. coli and P. aeruginosa, were tested. These species were chosen because of their importance in human health and ease of laboratory cultivation under controlled conditions.

The biocidal activity of CuO nanoparticles can be attributed to mechanisms such as the release of metallic Cu²⁺ ions, the direct association of nanoparticles with bacteria, and the generation of free radicals, which may be isolated or combined causing bacterial death (Khatoon et al., 2023). The results presented in Table 1 show that while the positive control exhibited relatively better inhibition against P. aeruginosa, the copper (II) nanoparticles exhibited superior inhibition against other microorganisms compared to the positive controls. It is important to consider that the positive controls are commercial antibiotics, serving as antimicrobial standards.

Particularly noteworthy is the result obtained for S. aureus and B. cereus, where the inhibition by the studied nanoparticles was two to three times greater than that of the standard antibiotic. Such results are highly promising, reflecting results close to or even surpassing those achieved with antibiotics. Results similar to those of Mohammed et al. (2022), where copper oxide nanoparticles decorated with carbon NPs had greater antimicrobial activity against S. aureus as compared with E. coli.

The notable difference in the biocidal efficacy of CuO NPs between gram-positive and gram-negative bacteria is attributed to the structural organization of their cell walls and membranes, which serve as protective barriers, granting bacteria resistance to external conditions. Gram-negative bacteria, with their more complex structure, possess a barrier that restricts the entry to only macromolecules. In contrast, gram-positive bacteria have a higher number of pores, allowing easier penetration of foreign molecules, which results in cell membrane damage and ultimately, cell death. (Wang et al., 2017; Niu and Zhang, 2023). Interestingly, nanorods can induce mechanical puncture of S. aureus. While top-flat nanorods deform the cell envelope, showing a bacteriostatic rate of 29%, top-sharp nanorods puncture S. aureus, reaching a bactericidal effect of 98% (Ye et al., 2022).

The results obtained by Selvaraj (2022) and Mohammad and Shyam (2023) showed improved biocidal performance of CuO nanoparticles against bacteria of the Bacillus genus (Bacillus subtilis). Moreover, CuO nanoparticles obtained by synthesis with plant leaf extract showed satisfactory results against gram-positive and gram-negative bacteria when tested at different concentrations (Andualem et al., 2020). These studies reinforce the valued antibacterial properties of CuO nanoparticles against a wide spectrum of microorganisms.

Studies literature indicate that nanoparticles attack bacteria through various mechanisms. It is not possible to determine a predominant method, since all cause some damage to the microorganism’s cell, whether to the cellular structure, microbial metabolic processes, or even genetic expression, leading to bacterial cell death (Khatoon et al., 2024 and Yu et al., 2024). As shown in Figure 8 (Khatoon et al., 2023), the bactericidal mechanisms of CuO nanoparticles proposed in literature are:

Figure 8
Possible antibacterial mechanism involved in the presence of Cu NPs proposed by Khatoon et al. 2023.

• • Damage to the cell membrane: through diffusion, nanoparticles and Cu²⁺ ions enter the cell. Copper is highly toxic to the bacterial cell, causing rupture of the cell membrane with extravasation of cytoplasmic contents and consequently cell death.

• • Release of Cu²⁺ ions: The negative charge present on the bacterial cell membrane facilitates the association with extracellular particles and metal ions (Cu²⁺) through electrostatic interactions. This leads to the denaturation of bacterial cell membrane proteins, causing irreversible damage to intracellular structures, ultimately resulting in the disintegration of the bacteria.

• • Inside the cell there is interaction with mitochondrial respiratory enzymes, which causes the generation of excess reactive oxygen species (ROS), which are highly reactive free radicals and can break chemical bonds of molecules that are fundamental to the functioning of the microorganism.

Due to their high oxidizing power, ROS can generate oxidative stress, causing destruction of proteins and enzymes, changes in the cell’s ionic character, inducing DNA fragmentation through oxidation, rupture of the cytoplasm and causing cell death (Wang et al. 2017 and Khatoon et al., 2023). According to Tamayo et al. (2016), the antibacterial characteristic of copper-based compounds supports their application in several areas, such as polymeric nanocomposites in the manufacture of hospital devices, the textile industry, packaging, and coatings.

5. Conclusions

In the present study, copper (II) oxide nanoparticles synthesized via co-precipitation of CuSO4 and NaOH were analyzed by XRD, FTIR, SEM,TEM, TGA, and antimicrobial activity assays. XRD and FTIR analyses confirmed the formation of CuO, with thermal stability at temperatures below 800 °C confirmed by TGA results. The particle size was around 36 nm, as determined using the Scherrer equation. However, according to TEM images, they are in rods and have an average length of 73 nm, an average width of 16 nm, and the presence of some clusters was observed via SEM and TEM. The CuO nanoparticles showed antibacterial activity, especially against gram-positive bacteria (S. aureus and B. cereus), with comparatively modest inhibition against gram-negative bacteria (E. coli and P. aeruginosa). Possibly, because the cellular structure of gram-positive bacteria is simpler, the bactericidal action of the nanoparticle also occurs intracellularly, where it has more mechanisms to destroy the bacterial cell. Therefore, the methodology used proved effective in synthesizing CuO nanoparticles for potential applications as additives in biocidal polymer coating formulations.

Acknowledgments

This work was supported by the Brazilian agencies CNPq, CAPES, FAPERGS and performed at LAPOL,LACOR LaBacVet, ICTA and LAPROM of Universidade Federal do Rio Grande do Sul (UFRGS) and LabMic of Universidade Federal de Goiás (UFG).

References

• ACKERMAN, C. M.; LEE, S.; CHANG, C. J. Analytical methods for imaging metals in biology: from transition metal metabolism to transition metal signaling. Analytical Chemistry, v. 89, p.22-41, 2017.
• AHAMED, M. et al. Synthesis, characterization, and antimicrobial activity of copper oxide nanoparticles. Journal of Nanomaterials, v. 2014, p. 637858, 2014.
• ANANTH, A. et al. Copper oxide nanomaterials: synthesis, characterization and structure-specific antibacterial performance. Chemical Engineering Journal, v. 262, p. 179-188, 2015.
• ANDUALEM, W. W. et al. Synthesis of copper oxide nanoparticles using plant leaf extract of Catha edulis and its antibacterial activity. Journal of Nanotechnology, v. 2020, p. 1-10, 2020.
• BENHADRIA, N. et al. Catalytic reduction of methylene blue dye by copper oxide nanoparticles. Journal of Cluster Science, v. 33, p. 249-260, 2022.
• BORKOW, G. Using copper to improve the well-being of the skin. Current Chemical Biology, v. 8, p. 89-102, 2015.
• CRISAN, M. C.; TEODORA, M.; LUCIAN, M. Copper nanoparticles: synthesis and characterization, physiology, toxicity and antimicrobial applications. Applied Sciences, v. 12, p. 141, 2022.
• FATIMAH, S. et al. How to calculate crystallite size from X-Ray Diffraction (XRD) using Scherrer method. ASEAN Journal of Science and Engineering, v. 2, p. 65-76, 2021.
• FLORES-RÁBGO, K. M. et al. Antibacterial activity of biosynthesized copper oxide nanoparticles (CuONPs) using Ganoderma sessile. Antibiotics, v. 12, p. 1251, 2023.
• HASSANZADEH-TABRIZI, S. A. Precise calculation of crystallite size of nanomaterials: a review. Journal of Alloys and Compounds, v. 968, p. 171914, 2023.
• IVANOVA, I. A. et al. Copper and copper nanoparticles applications and their role against infections: a minireview. Processes, v. 12, p. 352, 2024.
• KANINGINI, A.G. et al. Antimicrobial, antioxidant, and cytotoxic properties of biosynthesized copper oxide nanoparticles (CuO-NPs) using Athrixia phylicoides DC. Heliyon, v. 9, p. e15265, 2023.
• KHATOON, U. T.; VELIDANDI, A.; NAGESWARA RAO, G. V. S. Copper oxide nanoparticles: synthesis via chemical reduction, characterization, antibacterial activity, and possible mechanism involved. Inorganic Chemistry Communications, v. 149, p. 110372, 2023.
• KHATOON, U. T.; VELIDANDI, A.; NAGESWARA RAO, G. V. S. Nano-sized copper particles: chemical synthesis, characterization, and their size and surface charge dependent antibacterial potential. Results in Chemistry, v. 7, p. 101258, 2024.
• KUMAR, K.; CHOWDHURY, A. Facile synthesis of CuO nanorods obtained without any template and/or surfactant. Ceramics International, v. 43, n. 16, p. 13943-13947, 2017.
• M EL SAEED, A. et al. Synthesis of cuprous oxide epoxy nanocomposite as an environmentally antimicrobial coating. International Journal of Biological Mac ro m o lec u les, v. 89, p. 190-197, 2016.
• MOHAMMED, S. A. A. et al. Copper oxide nanoparticle-decorated carbon nanoparticle composite colloidal preparation through laser ablation for antimicrobial and antiproliferative actions against breast cancer cell line, MCF-7. BioMed Research International, v. 2022, p. 9863616, 2022.
• MOHAMMAD, M. S.; SHYAM, P. Structural analysis of biogenic copper oxide nanoparticles, and their bio-activity assessment. BioNanoScience, v. 13, p. 2265-2275, 2023.
• NAZ, S. et al. Synthesis, biomedical applications, and toxicity of CuO nanoparticles. Applied Microbiology and Biotechnology, v. 107, p. 1039-1061, 2023.
• NIU, B.; ZHANG, G. Effects of different nanoparticles on microbes. Microorganisms, v. 11, n. 3, p. 542, 2023.
• PHIWDANG, K. et al. Synthesis of CuO nanoparticles by precipitation method using different precursors. Energy Procedia, v. 34, p. 740-745, 2013.
• QAMAR, H. et al. Green synthesis, characterization and antimicrobial activity of copper oxide nanomaterial derived from Momordica charantia. International Journal of Nanomedicine, v. 15, p. 2541-2553, 2020.
• RANGEL, W. M.; BOCA SANTA, R. A. A.; RIELLA, H. G. A facile method for synthesis of nanostructured copper (II) oxide by coprecipitation. Journal of Materials Research and Technology, v. 9, p. 994-1004, 2020.
• REN, G. et al. Characterisation of copper oxide nanoparticles for antimicrobial applications. International Journal of Antimicrobial Agents, v. 33, p. 587-590, 2009.
• RIFANI, N. D. et al. Synthesis, characterization, and antimicrobial properties of copper oxide nanoparticles produced by pulse laser ablation method in chitosan solution. Journal of Applied Research and Technology, v. 21, p. 196-204, 2023.
• RIVERA-MENDOZA, D. et al. Antimicrobial activity of green synthesized silver and copper oxide nanoparticles against the foodborne pathogen Campylobacter jejuni. Antibiotics, v. 13, p. 650, 2024.
• SELVARAJ, S. P. Enhanced surface morphology of copper oxide (CuO) nanoparticles and its antibacterial activities. Materials Today: proceedings, v. 50, p. 2865-2868, 2022.
• TAMAYO, L. et al. Copper-polymer nanocomposites: an excellent and cost-effective biocide for use on antibacterial surfaces. Materials Science & Engineering. C; Materials for Biological Applications, v. 69, p. 1391-1409, 2016.
• TOMAR, R.; SINGH, N.B. Overview of applications of nanotechnology. Materials Research Foundations, v. 148, p. 1-26, 2023.
• WANG, L.; HU, C.; SHAO, L. The antimicrobial activity of nanoparticles: present situation and prospects for the future. International Journal of Nanomedicine, v. 12, p. 1227-1249, 2017.
• YE, J. et al. Eco-friendly bacteria-killing by nanorods through mechano-puncture with top selectivity. Bioactive Materials, v. 15, p. 173-184, 2022.
• YU, J. et al. Application of antimicrobial properties of copper. Applied Organometallic Chemistry, v. 38, n. 7, 2024.
• ZEHETMEYER, G. et al. Biodegradable and antimicrobial films based on poly(butylene adipate-co-terephthalate) electrospun fibers. Polymer Bulletin, v. 74, p. 3243-3268, 2017.
• ZHOU, J. et al. Breaking down the cell wall: Still an attractive antibacterial strategy. Frontiers in Microbiology, v. 13, p. 952633, 2022.

Publication Dates

• Publication in this collection
  24 Feb 2025
• Date of issue
  Jan-Mar 2025

History

• Received
  08 Jan 2024
• Accepted
  21 Nov 2024