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*Corresponding author: 
  Email: tibebu.alemu@ambou.edu.et, +251909117127 https://dx.doi.org/10.4314/eajbcs.v6i1.4S 
 

 

 
The Effect of CuO Nanoparticle Variation on the Green Synthesized ZnO/CuO Nanocomposites 

for Antibacterial Activities 
 

Bulti Abdisa Kerayu1, Hundessa Alemu1, Gemechis Fikadu1, Asefa Keneni2, Tibebu Alemu1,3* 

  
 

1Department of Chemistry, College of Natural and Computational Sciences, Ambo University, Ambo, 
Ethiopia 
2Department of Biology, College of Natural and Computational Sciences, Ambo University, Ambo, 
Ethiopia 
3School of Graduate Studies, Ambo University, Ambo, Ethiopia 
 

KEYWORDS:  
Orange peel extract;  

ZnO/CuO nanocomposites; 

Antibacterial activity;  

Surface characterization;  

Green synthesis;  

UV-Vis spectroscopy 

 

 

 

 

 

 

ABSTRACT 
Plant extracts play critical role in synthesizing nanomaterials for a wide range of 
applications in human health and managing environmental pollutions. The present work 
focuses on varying CuO NP’s concentration in ZnO/CuO nanocomposites (NC) 
synthesized with orange peel extracts (ZnO/CuO WE NC) for its antibacterial activities. 
The concentration of CuO with respect to ZnO NP fixed in 10:10, 10:20, 10:30, and 10:40. 
The as-synthesized NC is characterized using UV-Vis, FTIR, XRD, and SEM 
spectroscopes. Accordingly, the UV-Vis result reveals that the absorption spectra range 
from 312-328 nm confirming the incorporation of extract to provide strong absorption 
peaks along with the increasing concentration of CuO in the nanocomposite while it 
energy band gap of ZnO/CuO WE NC was narrowed from 3.97 to 3.78 eV. FTIR analysis 
revealed that the stretching vibration of Zn-O and Cu-O are observed around 480 cm-1 and 
600 cm-1, respectively in all ratios of WE NC. XRD indicated that the formation of 
hexagonal wurtzite structure and the crystallite size recorded in 24.12 to 3.17 nm. The 
SEM image showed the morphology of 10:20, 10:30, and 10:40 are aggregated, smooth, 
polished, and smaller size compared to 10:10 ZnO/CuO WE NC. The antibacterial 
activities of 10:10, 10:20, 10:30, and 10:40 ZnO/CuO WE NC were remarkable especially, 
10:40 ZnO/CuO WE NC provided strong activity against P. aeruginosa. Thus, the as-
synthesized 10:40 ZnO/CuO WE NC is so profound to combat bacterial infectious 
diseases.

INTRODUCTION 

Nanotechnology is a rapidly evolving science 
field focused on the design, synthesis, and 
manipulation of materials (nanomaterials) at the 
nanometric scale (1–100 nm) with wide-ranging 
applications (Singh et al., 2015). Among 

nanomaterials, metal oxide nanoparticles (NPs) 
have garnered significant attention because of 
their unique phyisicochemical properties, 
including high surface area, chemical stability, 
and antimicrobial efficacy (Mihindukulasuriya 
and Lim, 2014; Benelmekki, 2015; Khan et al., 
2019; Kumari et al., 2023). The growing 

East African Journal of Biophysical and Computational Sciences 
Journal homepage : https://journals.hu.edu.et/hu-journals/index.php/eajbcs 

  

Research article 



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34 
 

challenge of antibiotic resistance necessitates an 
alternative antimicrobial strategies, and metal 
oxide NPs have emerged as promising 
candidates due to its stability and broad-
spectrum activity (Sawai, 2003; Shi et al., 
2014). For example, zinc oxide (ZnO) and 
copper oxide (CuO) NPs exhibited antibacterial 
effects through multiple mechanisms, including 
reactive oxygen species (ROS) generation, 
membrane disruption, and ion release leading to 
bacterial cell death (Mantecca et al., 2015). 
ZnO, an n-type semiconductor with a wide band 
gap (3.37 eV), offers excellent stability and 
biocompatibility, making it suitable for 
biomedical and environmental applications 
(Sirelkhatim et al., 2015; Bekru et al., 2022). In 
contrast, CuO, a p-type semiconductor with a 
narrow band gap, demonstrates strong 
antibacterial and antifungal properties due to its 
ability to generate ROS (Yulizar et al., 2018; 
Naseem and Durrani, 2021). The integration of 
ZnO and CuO in to nanocomposites (NCs) 
enhances charge separation, reduces electron-
hole recombination, and improves visible-light 
absorption, thereby augmenting their 
antibacterial effectiveness (Bekru et al., 2022). 

Scholars have developed various synthesization 
techniques of NPs, among which green methods 
have emerged as a promising approach that 
leverages plant-derived biomolecules. These 
synthesis methods offer several advantages over 
conventional or widely accepted approaches, 
including sustainability, reduced toxicity and 
controlled particle morphology (Abid et al., 
2022; Kumar et al., 2023). Example, ZnO NPs 
synthesized using orange peel extract effectively 
inhibited E. coli and S. aureus under ambient 
conditions (Thi et al., 2020). In similar case, 
ZnO/CuO NCs have been prepared using 

Zingiber officinale extract demonstrated strong 
antibacterial effect against both gram positive 
and gram negative bacterial (Takele et al., 
2023). In addition, Gao et al., (2020) reported 
that biogenic ZnO NPs enhanced the shelf-life 
of fresh strawberries, highlighting their potential 
in food preservation (Luque et al., 2018; Gao et 
al., 2020). Recently, Alemu et al. (2023) 
developed ZnO/CuO NCs in orange peel extract 
and recorded outstanding inhibition of gram-
positive bacteria growth. Although the 
aforementioned and other studies demonstrated 
exceptional antibacterial performance upon CuO 
NPs incorporation, the optimal concentration for 
maximum antibacterial effect or efficacy was 
not clearly determined yet. Therefore, a 
systematic investigation into the effect of CuO 
NPs concentration in the NCs on bacterial 
growth inhibition remains unexamined. This 
research aims to address the gap observed 
through optimizing the CuO NP content in 
ZnO/CuO NCs synthesized using orange peel 
extract and concomitantly assessed their 
antibacterial effectiveness against selected 
bacterial strains. The findings will contribute to 
the growing field of green nanotechnology by 
providing scientific insights into the synthesis, 
optimization, and antibacterial applications of 
ZnO/CuO NCs, thereby promoting sustainable 
and effective antimicrobial solutions. 

MATERIALS AND METHODS 

Materials 

Zinc nitrate hexahydrate (Zn (NO3)2.6H2O, 
purity: 99%, India), Zinc acetate dihydrate 
(Zn(CH3COO)2.2H2O, purity: 98%, India), 
Copper (II) nitrate trihydrate (Cu(NO3)2.3H2O, 
UNI-CHEM Chemical Reagents, purity: 99%, 
India), sodium hydroxide (NaOH, Ran chem 



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35 
 

Industry and Trading, purity: 99.5%, Germany), 
Absolute Ethanol (CH3CH2OH, Purity: 99.99%, 
India) analytical grades were used for this study. 
Pseudomonas aeruginosa (Gram-negative) and 
Staphylococcus aureus (Gram-positive) bacteria 
were Isolated, cultured and tested in biology 
laboratory, Ambo University, Ethiopia. 

Preparation of Orange peel extract 

Orange peels were collected from the market of 
Ambo town, Oromia region, Ethiopia. After 
thoroughly washing and rinsing with deionized 
(DI) water, the fruit was peeled, air dried for 12 
hours and about 4 kg taken which was ready for 
extraction process. The dried peel was then 
ground into a moderately fine powder. 
Afterward, 1 gm of the powder was placed in 
different glass containers with 50 mL of DI 
water in each container and was stirred for 3 hrs. 
Once macerated, each mixture was placed in a 
water bath for 60 min at 60 ºC. Finally, the 
mixture was filtered, and the resulting extract 
was stored (Figure 1) in a refrigerator of 4 ºC 
(Manokari et al., 2016). 

Figure 1: Orange fruits peel purchased from 
Ambo market for extraction process  

Synthesization of ZnO/CuO nanocomposite 
(NC) with Orange Peel extract (WE) 

The ZnO/CuO NC in orange peel extract 
(ZnO/CuO WE) was prepared via mixing 2 g of 
each Zn (NO3)2.6H2O and Zn (CH3COO)2.2H2O 
dissolved separately in 42.5 mL of orange peel 
extracts. This mixture was then continuously 

stirred for 60 min once placed in a water bath at 
60 ºC. Subsequently, the mixture was dried at 
150 ºC and then heated for 1 hr at 400 ºC. The 
organic substances in orange peel extract 
supposed to act as ligating agents as shown in 
Alemu et al., (2023). The hydroxyl aromatic 
ring groups in the extract could form complex 
molecules with Zn2+ and Cu2+ ions. Through, 
the process of nucleation and shaping followed 
by calcination at 400 ˚C, it was resulted in the 
formation of ZnO/CuO NC (Çolak and 
Karaköse, 2016). The concentration of 
ZnO/CuO WE varied from 10:10, 10:20, 10:30 
and 10:40 ppm in the ratio of ZnO:CuO NP via 
changing the concentration of only CuO NP to 
study its effect on the antibacterial activity 
(Singh et al., 2018).(J. Singh et al.,  2018). 

Reaction mechanism in the synthetization of 
ZnO/CuO WE NC  

Figure 2 display the possible reaction 
mechanism during the synthesis process of 
ZnO/CuO NC using orange peel extract 
(ligation process takes place between the 
functional groups of the orange peel and the 
respective precursors). The phytochemicals 
components in orange peel extracts could act as 
ligand agents and forms complex compounds 
between OH group of the organic molecules and 
Zn2+ and Cu2+ ions. The corresponding 
nanoparticles are formed and stabilized through 
a nucleation process, while the mixture of 
organic components decomposes upon 
calcination, reducing the ions and resulting in 
the formation of ZnO/CuO nanocomposites (Thi 
et al., 2020). Lastly, Zn0 and Cu0 gets oxidized 
to mixture of ZnO/CuO NC upon calcination 
(Ahmed et al., 2022) while the presence of 
organic components are used as capping agent 



East Afr. J. Biophys. Comput. Sci. (2025), Vol. 6, No. 1, 33-45 
 

36 
 

to prevent the NPs agglomerations (Veisi et al., 
2021).  

 

 

Figure 2: Proposed mechanism for the formation of functionalized ZnO/CuO WE NC. 

Characterization of ZnO/CuO WE NC 

The surface characterizations of ZnO/CuO WE 
NC were studied using X-ray diffraction (XRD) 
(SHIMADZU Corporation (Japan), XRD-7000 
X-RAY DIFFRACTOMETER) for crystalline 
structure study. Fourier transform infrared 
(FTIR) (IS 50 ABX, Germany) was used to 
reveal functional group of NC. Whereas, UV-
Vis spectrophotometer (OPTIZEN TOP, 
KOREA) was used to investigate the chemical 
properties and its energy band gap while the 
morphology of ZnO/CuO WE NC was 
characterized by scanning electron microscope 
(SEM) (EVO18, CARL ZEISS). 

Antibacterial Activities 

The antibacterial activities of the synthesized 
ZnO/CuO WE were done using two human 
pathogenic bacteria strains i.e., Staphylococcus 
aureus (Gram-positive) and Pseudomonas 
aeruginosa (Gram-negative). The agar well 
diffusion method was used for the evaluation of 
the antibacterial activity of as-synthesized 
ZnO/CuO WE NC. Muller Hinton (MH) Agar 
plates were prepared, sterilized, and solidified. 
After solidification, 106 colony forming units 
(CFU) of bacterial cultures were swamped on 
solidified MH Agar plates. Five wells were cut 
out in the agar layer of the plate using an 
aluminum bore of 2 mm diameter for the 



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37 
 

synthesized ZnO/CuO WE NC (Perez-Gavilan 
et al., 2021) with different concentration (10:10, 
10:20, 10:30, and 10:40 for ZnO:CuO). Then, 
50 l of each of the synthesized NC, positive 
control (Cloxacillin), and negative control 
(DMSO) was dropped into the wells using a 
micropipette and then incubated at 37 ◦C for 18 
hrs. At the end of the incubation period, the 
antibacterial activities of the synthesized NC 
were checked by observing and measuring the 
zone of inhibition.  

RESULTS AND DISCUSSION 

Characterization of Nanocomposite  

UV-Vis spectroscopic analysis: The UV-Vis 
spectra of the 10:10, 10:20, 10:30, and 10:40 
ZnO/CuO WE NC is shown in Figure 3. The 
absorption peaks of the as-synthesized NC were 
found at the interval of 320-334 nm which fall 
under visible region and its sharp absorption 

feature indicates that each ratio of ZnO:CuO NC 
is monodispersed in nature. The UV-Vis spectra 
signify that the strong absorption peaks (Figure 
3(a)) has formed in the visible region, which 
ascribed the presence of biomolecules from the 
orange peel extract (Dey et al., 2021). These 
characteristic absorbance peaks for each 
ZnO:CuO ratio indicate the successful 
formation of NCs with adsorbed biomolecules. 
The results indicate that the synthesized 
ZnO:CuO WE NCs achieved optimal reduction 
for tested ratio whereas 10:20 ZnO:CuO WE 
NC exhibited highest absorbance at longer 
wavelength comparing to the remaining 
components. This spectral shift is attributed to 
the formation of smaller particle sizes 
comparing to 10:10, 10:30 and 10:40 ZnO:CuO 
WE NCs as a result of the quantum confinement 
effect (Matinise et al., 2017). In addition, the 
10:20 ZnO:CuO WE NC possesses the lowest 
energy band gap (Table 1) suggesting enhanced 
electron mobility.  

 
Figure 3: UV-Vis spectra (a), Tauc plot for the energy bandgap determination for ZnO/CuO 

(10:10, 10:20, 10:30 and 10:40). 



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38 
 

The band gap energy of the synthesized NPs 
was determined using equation (Eq. 1) below. 

௚ܧ = ℎܿ
ൗߣ                                                               (1) 

Where, h = Planck’s constant (6.63 x 10-34 m2 
kg s-1), c = speed of light (3.00 x 108 ms-1), λ = 
Absorption wavelength in UV region (330 nm). 

The energy band gap values for the synthesized 
ZnO/CuO WE NCs, as presented in Table 1, 
were calculated to be 3.97 eV, 3.78 eV, 3.85 eV, 
and 3.83 eV for the 10:10, 10:20, 10:30, and 
10:40 ratios, respectively. These results indicate 
that as the ZnO:CuO ratio changes from 10:10 

to 10:20, the band gap energy decreases (Eq. 1), 
suggesting that the 10:20 ZnO/CuO WE NC 
exhibits the most effective visible light 
absorption. This finding aligns with the results 
obtained from the Tauc plot. Furthermore, the 
experimental results are consistent with 
theoretical values, which typically range from 
3.02 to 1.47 eV. However, the observed band 
gap values are slightly higher than those 
reported by Qamar et al. (2017). The UV-Vis 
absorption spectrum of the synthesized NPs 
shows absorption at lower wavelengths (312–
328 nm) for all NCs. Therefore, UV-Vis 
spectroscopy characterization further confirms 
the successful formation of ZnO/CuO WE NCs 
in the expected absorption range. 

Table 1: The energy band gap calculated from UV-vis data for ZnO/CuO WE NC. 

Ration of ZnO/CuO WE NC Wavelength (ૃܠ܉ܕ) in nm The energy band gap (Ebg) in eV 
10:10  312  3.97  
10:20  328  3.78 
10:30  322 3.85 
10:40  324 3.83 
 

FT-IR Spectroscopic Analysis: FT-IR spectra 
of the prepared ZnO/CuO WE NC were 
recorded to determine its functional groups in 
the range of 4000–400 cm−1 (Figure 4). 
According to the results, the spectra of all ratios 
in ZnO/CuO WE NC demonstrated the 
absorption band exhibited at 3200-3500 cm-1 
represents the stretching vibrations of –OH 
group of adsorbed H2O molecule on the surface 
of NCs (Nuisin et al., 2022). On the other hand, 
the stretching vibrations observed at 1105, 1391, 
1590 and 1606 cm-1 show C-O stretching, C-H 
bending, C=O and  C=C bonds (Berra et al., 
2018), respectively in all combination. In 
addition, the intense absorption peaks observed 

at 609, 715, and 973 cm⁻¹ correspond to the 
stretching vibrations of Zn–O, Cu–O, and Zn–
O–Cu bonds within the nanocomposites (Li et 
al., 2022). The intensity of these peaks 
increased with the rise in CuO concentration, 
while the nature of the functional groups 
remained unchanged, confirming that the 
composition of the nanocomposites remained 
consistent across different CuO concentrations. 



East Afr. J. Biophys. Comput. Sci. (2025), Vol. 6, No. 1, 33-45 
 

39 
 

 

Figure 4: FTIR spectra of synthesized 
ZnO/CuO WE NC.  

X-Ray Diffraction (XRD) Analysis: The XRD 
patterns of ZnO/CuO WE NCs are shown in 
Figure 5, covering the 2θ range of 10–80°. The 
diffraction peaks for ZnO/CuO WE NCs with 
different concentrations were observed at 2θ = 
35.90°, 36.76°, 42.40°, and 42.51°, 
corresponding to the lattice planes (002), (101), 
(012), and (012), respectively. These peaks 
confirm the hexagonal crystalline phase of the 
ZnO/CuO WE NCs, agreed with the JCPDS 
card No. 36-1451. Additionally, a slight shift in 
the 2θ positions of certain peaks was observed. 
This shift may be attributed to variations in CuO 
concentration during the preparation of the 

samples using orange peel extract, which could 
influence the crystallographic structure of the 
NCs. The average crystalline size of ZnO/CuO-
WE NCs for each ratio is calculated using 
Debye-Scherrer's equation.  

 

Figure 5: XRD patterns of the as-synthesized 

ZnO/CuO WE NC.  

Accordingly, the average crystalline size (Dp) of 
10:10, 10:20, 10:30 and 10:40 ZnO/CuO WE 
NC were 24.12, 16.33, 6.64 and 3.17 nm (Table 
2). The result confirmed that the size of the NCs 
has decreased as the increasing concentration of 
CuO within the composites. In the current study, 
the presence of different functional groups 
including C–O, C=O, and O–H in the plant 
extract contribute to stabilizing particles while 
an increase amount of CuO increase the crystal 
growth of ZnO/CuO WE NC. 

 

  



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40 
 

Table 2: Crystalline size determination for ZnO/CuO-WE nanocomposites. 
Nanocomposite 2θ θ cosθ FWMH in rad size/nm Aver/nm 
CuO/ZnO (10:10) 32.3 16.15 0.96053 0.3548 0.00603 23.95119 24.12 

34.1 17.05 0.95604 0.3705 0.00629 23.04399 
36.71 18.355 0.94909 0.3392 0.00576 25.35469 

CuO/ZnO (10:20) 27.46 13.73 0.97142 0.54702 0.00929 15.36071 16.33 
36.71 18.355 0.94909 0.52469 0.00892 16.39122 
42.44 21.22 0.93219 0.50779 0.00863 17.24380 

CuO/ZnO (10:30) 18.58 9.29 0.98688 1.4827 0.02521 6.713731 6.64 
24.69 12.345 0.97685 1.2446 0.02116 6.713731 
35.20  17.6 0.95319 1.3191 0.02242 6.491789 

CuO/ZnO (10:40) 22.97 11.485 0.9799 2.6707 0.04541 3.118995 3.17 
33.46 16.73 0.95767 2.6707 0.04541 3.191395 
35.95 17.975 0.95119 2.6707 0.04541 3.213137 

 
Analysis of Surface Morphology: The morphology of 10:10, 10:20, 10:30, and 10:40 for ZnO/CuO 
WE NC was studied using SEM (Figure 6). The SEM image of 10:10 ZnO/CuO WE NC indicates that 
the crystal formed has cluster and flake-like structure while the particles are agglomerated in nature.  

 

Figure 6: SEM images of ZnO/CuO WE NC (a) 10:10, (b) 10:20, (c) 10:30, and (d) 10:40 in 
ZnO:CuO ratio. 

(a

(d(c) 

(b



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41 
 

The images of the 10:20 and 10:30 ZnO/CuO 
WE NCs exhibit aggregated, smooth, and 
polished surfaces with smaller particle sizes 
compared to 10:10 ZnO/CuO WE NC. Notably, 
the 10:40 ZnO/CuO WE NC displays a finer 
distribution of smaller particles with a porous-
like structure. These findings confirm that the 
grain size and overall morphology of the 
synthesized NCs are strongly influenced by the 
CuO NP concentration under identical reaction 
conditions. Furthermore, the crystal sizes of 
10:10, 10:20, 10:30, and 10:40 ZnO/CuO WE 
NCs increased, as determined using the Scherrer 
equation. The images clearly reveal 
microstructural heterogeneities and distinct 
morphological differences among the 
synthesized NCs, highlighting the effect of CuO 
content on their structural properties. 

Study of Antibacterial Activity  

For each synthesized nanomaterial, the zone of 
inhibition (ZOI) values was recorded as shown 
in Table 3. The antibacterial effect of 
nanomaterials against both bacteria compared 
with control samples, the diameter of ZOI 
varied at the different concentration levels of 
NCs. The three trials of antibacterial activities 
of 10:10, 10:20, 10:30, 10:40 ZnO/CuO WE NC 
were measured and showed a good response 
against S. aureus with an average maximum 
ZOI of 17.33, 21.66, 25.33 and 28.66 mm while 
its activity against P. aeruginosa was shown 
relatively higher ZOI of 21.00, 25.66, 28.33 and 
30.66 mm after 18 hrs incubation times. This 
indicates that 10:10, 10:20, 10:30, and 10:40 
ZnO/CuO WE NC in particular 10:40 ZnO/CuO 
WE NC are more effective for P. aeruginosa 
than S. aureus bacterial strain. 

Table 3: Antibacterial activity of NC applied to two human pathogenic bacteria.  

Nanocomposites Test organism Zone of inhibition (mm) 
Trial-1 Trial-2 Trial-3 Average Cloxacillin 

10:10 ZnO/CuO WE NC S. aureus 14 13 25 17.33 35 
P. aeroginosa 22 27 14 21.00 35 

10:20 ZnO/CuO WE NC S. aurous 19 22 24 21.66 35 
P. aeroginosa 27 20 30 25.66 35 

10:30 ZnO/CuO WE NC S. aurous 25 26 25 25.33 35 
P. aeroginosa 30 30 25 28.33 35 

10:40 ZnO/CuO WE NC S. aurous 29 30 27 28.66 35 
P. aeroginosa 30 35 27 30.66 35 

 

This suggests that Gram-negative bacteria 
exhibited higher susceptibility to the 
synthesized 10:40 ZnO/CuO WE NC, as their 
loosely structured cell membranes provide less 
protection against external attacks. Figure 7 and 
8 confirm the formation of larger inhibition 
zones for bacterial strains, represented as 1 
(10:10), 2 (10:20), 3 (10:30), and 4 (10:40) 

ZnO/CuO WE NC, against Gram-positive and 
Gram-negative bacteria, respectively. The 
highest concentration (sample 4) demonstrated 
the most effective zone of inhibition (ZOI) 
compared to the others. Therefore, the 
antibacterial effectiveness of the nanomaterials 
increases with the CuO NP concentration in the 



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42 
 

ZnO/CuO WE NC synthesized using orange 
peel extracts (Wang et al., 2017). 

 

 

Figure 7: The antibacterial activity of ZnO/CuO WE NC against S. aureus bacteria. 

 

Figure 8: The antibacterial activity of ZnO/CuO WE NC against P. aeroginosa bacteria 

The results of this study indicated that the 
antibacterial activities of 10:10, 10:20, 10:30, 
and 10:40 ZnO/CuO WE NC is CuO NP 
concentration dependent. The negative control 
(DMSO) did not show any ZOI whereas the 
positive control (Cloxacillin) showed the 
highest ZOI. Based on the results of the current 
study, it was evident that the ZOI of samples 
(Figure 7 and 8) showed that the synthesized 
compounds significantly inhibited the selected 
bacterial probably by generating ROS species 
that can easily penetrate the bacterial wall 
particularly when the ratio of ZnO to CuO WE 

changed from 10:10 to 10:40. The ROS 
generated by NC provides better contact 
environment with bacteria (Khan et al., 2016; 
Kumar et al., 2017). Therefore, this study 
provides valuable insights into overcoming 
bacterial resistance to standard antibiotic drugs 
and offers a potential solution to serious health-
related issues. The synthesized nanocomposite 
(NC) could serve as a viable alternative to 
antibiotic-resistant drugs due to its cost-
effectiveness, non-toxic nature, and sustainable 
production from renewable and environmentally 



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43 
 

friendly materials (Chinemerem Nwobodo et 
al., 2022). 

CONCLUSION  

In this work, we have studied the effect of CuO 
NP concentration variation of ZnO/CuO NC 
prepared with orange peel extract for the study 
of antibacterial activities. The as-synthesized 
materials were characterized by SEM, XRD, 
FTIR, and UV-VIS for the investigation of its 
morphology, crystal structure, functional group, 
and energy band gap. The XRD study confirms 
the formation of hexagonal wurtzite structure 
and the crystallite size of 24.12 - 3.17 nm, the 
vibrational stretching band was found around 
480-600 cm-1 reveal that the WE NC possesses 
the metal-oxygen bonds, and SEM image signify 
that each ratio of ZnO/CuO WE NC affects the 
grain size and anti-bacterial activity of 
ZnO/CuO WE NC. The characteristic 
absorption peak observed at 312-328 nm also 

supports the formation of 10:10, 10:20, 10:30, 
and 10:40 of ZnO/CuO WE NC with a very 
narrow energy gap with 3.97-3.78 eV. Among 
all WE NC with various ZnO:CuO NC ratio, 
10:40 ZnO/CuO WE NC exhibited better 
antibacterial activity against both human 
pathogens particularly to P. aeroginosa bacteria.  

Declaration of interest 

The authors declare no conflict of interest. 

Acknowledgements 

The author would like to forward heartfelt 
gratitude to Ambo University for providing the 
essential facilities and support that contributed 
to the successful completion of this research. 

 

 

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