1. INTRODUCTION

Modern materials science includes an important field known as nanotechnology. It is involved in the fabrication and development of many nanoparticles with sizes ranging from 1 to 100 nm. In modern research, nanotechnology plays an important role, including applications in pharmacy, health, biomedical sciences (Bukhari et al., 2021), electronics, food, pharmaceuticals (Peddi et al., 2021), chemistry, the chemical industry, cosmetics, and the energy sciences, mechanics, space technology, and environmental health, (Hassan et al., 2019). Due to their potential as a cheap alternative instead of costly noble metals nanoparticles are used as catalysts in many industrial chemical processes. Lots of interest has been paid to the fabrication of nanoparticles from inexpensive and plentiful metals found on Earth (Shamsuddin & Raja Nordin, 2019).

As the bulk material scale decreases to the nanoscale, its physicochemical properties change. The optical, electrical, and magnetic properties of nanosized particles differ from those of the same material's bulk version.(Thamer et al., 2018).

Metal nanoparticles have many applications due to their unique optical, electrical, mechanical, magnetic, and chemical properties. Nanoparticles have been produced via chemical, physical and biological methods. Even though the majority of approaches produce nanoparticles that are clean and well-defined, these approaches are either very expensive or have the potential to be harmful to the natural environment (Altikatoglu et al., 2017).

Copper oxide nanoparticles (CuO NPs) are a type of semiconducting material (Rehman et al., 2022) that has recently been gaining lots of interest due to their unique electrical, optical, and catalytic properties. They have been used in lithium-ion electrode materials, sensors, photovoltaic devices, catalysis, biomedicine, and so on (Manasa et al., 2021).

CuO is a p-type semiconductor material that has a direct bulk bandgap of 1.2 eV and a refractive index of 2.63 (Horti et al., 2020). It has the space group C2/c and crystallizes in the monoclinic phase (No. 15). CuO-NPs are widely used in gas sensors, batteries, biosensors, giant magnetoresistance materials, catalysts, superconductors, solar cells (Taran et al., 2021), high-temperature superconductors magnetic storage media, catalysis (Gawande et al., 2016), (Kwak & Kim, 2005), and photocatalysis for water purification environment (Sone et al., 2020). The sol-gel approach (Othman et al., 2013), microwave irradiations (Elazab, 2018), thermal decomposition (Salavati-Niasari & Davar, 2009), an electrochemical method (Velusamy et al., 2018), and an alkoxide-supported technique have also been utilized in the fabrication of CuO-NPs (Grigore et al., 2016).

Even though most approaches produce clean, well-defined nanoparticles, they are either costly or harmful to the environment. Moreover, due to the use of toxic substances, high contaminants, and excessive energy consumption in produced NPs, these approaches have been drawn while biosynthesized CuO-NPs are considered a safe fabrication method. Especially in medical applications, the use of gregarious and single cells microorganisms such as actinomycetes, fungi, bacterium, plants, or algal during the green CuO-NPs synthesis is preferred (Hassan et al., 2019).

Recently systems are extensively spread along co-logical boundaries (Rehman et al., 2022)

making them conveniently accessible and well-controlled. The utilization of physical and chemical techniques has significantly decreased due to the green products of nanoparticles (Shanan et al., 2018). The CuO nanoparticles in this research study were produced by an environmentally friendly process known as green synthesis.

The fabricated CuO nanoparticles were characterized using a variety of characterization methods including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction diffractometer (XRD), Field Emission Scanning Electron Microscope (FESEM, and UV-visible spectroscopy.

2. MATERIALS AND METHODS

2.1 Materials Required:

Copper (II) nitrate trihydrate Cu (NO₃)₂.3H₂O and sodium hydroxide (NaOH) was purchased from Sigma Aldrich Company and used as received.

2.2 Preparation of Ferulago ANGULATE [ Schltdl.] BOISS Leaf extracT:

Fresh Leaves of Ferulago angulate [ Schltdl.] BOISS (Figure 1a) was collected in April 2021 from Gara Mountain in the Kurdistan region- of Iraq. To remove any dirt particles, the leaves were washed and rinsed 3 times with distilled water, then dried in the shadow at room temperature for one month. Using a 500 W combined grinder, the dried leaves were ground into powder. Then 50 g of dried ferulago angulata leaf powder contained in 500 ml of distilled water was boiled at 70 C^◦ for 20 minutes.

Afterward, the solution was gradually cool down to reach room temperature. It should be noted that after the boiling process, the color of the solution changed to light orange color (Figure 1 b).

Figure 1: (a) Ferulago angulate [ Schltdl.] BOISS fresh Leaf and, (b): Ferulago angulate [ Schltdl.] BOISS extract.

Afterward, the solution mixture was filtered using Whatman filter paper No. 2 paper, and then the filtrate was concentrated by rotary evaporation for 15 minutes at room temperature. Then the extract was stored at 4°C for the synthesis of copper oxide nanoparticles.

2.3Phytochemical tests of Ferulago angulate [ Schltdl.] BOISS Leaf extracT:

As shown in Figure 2, the plant extracts were tested for preliminary phytochemical screening.

Flavonoid test:

Concentrate H₂SO₄ test

The presence of flavonoids was shown by the production of an orange color after a few drops of concentration H₂SO₄ was added to 1 ml of extraction (Nafeesa et al, 2017) (Tyagi, 2017).

Lead acetate test:

To 1 ml of each extract, a few drops of a lead acetate solution containing 10% were added. The yellow precipitate indicates flavonoids (Singh & Kumar, 2017).

Carbohydrate test:

Molish's test (general test)

A test tube was filled with 1 ml of extract, and 5 drops of alcoholic α—naphthol, and was vigorously shaken before 1 ml of concentrated H₂SO₄ was slowly added to the tube wall to create a violet ring. This proved that there were carbs present (Lakshmibai et al., 2015) (Sivaranjani, 2021).

Alkaloid test:

Wagner’s test:

Each extract was acidified and given 2 Wagner's reagent drops (1.25gm of iodine with 2gm KI and distilled water to create a final size of 100ml). Alkaloids are present when brown and reddish precipitate forms along the test tube's sides (Kardong et al., 2013).

Tannin test:

Ferric chloride test:

Braymer's testing for tannins involves placing 1 ml of each extract in a test tube, adding 3 ml of distilled water, boiling it, and then adding 1 ml of 1% ferric chloride. If blue-green, brownish-green, or bluish-black stains develop, tannins are present. (Uma et al., 2017)(Kardong et al., 2013)(Giri et al., 2016)

Saponin test:

Foam test:

A little quantity of extract should be dissolved in 3ml of distilled water after being forcefully shaken and left for 1 minute, semi-permanent substances, such as foam, can detect saponins (Banso, 2009).

Aqueous mercury chloride (Hg₂Cl₂) test:

Aqueous mercury chloride was used as a reagent in the saponin test, which used (5%) aqueous mercury chloride. Each extract and the reagent were mixed in a1 ml of distilled water. The formation of a white precipitate is a sign that saponin is present (Harborne, 1973).

Proteins and amino acid test:

Ninhydrin test (free amino acid test)

After adding 1 ml of the 1% ninhydrin reagent to the extract and heating it for 10 minutes in a water bath, the color of the amino acids (purple) was revealed (Melkamu & Bitew, 2021).

Proteins test (Biuret test)

2 ml of extract were combined with 5 drops of copper sulfate solution, 1 ml of ethanol, and then pellets of potassium hydroxide. The ethanolic layer became pink, indicating the presence of peptide bonds (Tyagi, 2017).

Phenolic test:

Lead acetate test

A white phenol precipitate was created by mixing 5 ml of distilled water with 1 ml of each extract and 3 ml of 10 % lead acetate (Naik & Sellappan, 2019), (Kardong et al., 2013).

Ferric chloride test:

Adding a few drops of a 5 percent solution of ferric chloride to 1 ml of each extract. The existence of phenols was indicated by blue-black or dark green color (Naik & Sellappan, 2019).

Figure 2: Phytochemical Test of Ferulago angulate [ Schltdl.] BOISS Leaf extract. F: Flavonoid, A: Alkolid, C: Carbohydrate, S: Saponin, P: Protein, AA: Amino Acid, Ph: Phenol, T: Tannin.

Ferulago angulata, (Schlecht.) Boiss., also known as "Chavil" or "Chavir" in Persian, is described in the literature as a folk medicine, a food additive, particularly when used with dairy products, and an aromatic plant that is produced in the Kurdistan region of Iraq (Fig 3). The aerial parts of Ferulago angulata have shown in previous phytochemical screening studies for bioactive compounds to be a rich source of flavonoids, phenols, coumarins such as pyranocoumarins and furanocoumarins, monoterpene hydrocarbons such as α-Pinene, myrcene, α-Phellandrene, trans-β-Ocimene, oxygenated monoterpenes such as thymol, sesquiterpenes, and sesquiterpene lactones(Jiménez et al., 2000)(Mabry & Moubasher, 1990)(Doganca et al., 1991)(Khalighi-Sigaroodi et al., 2006)(M. Naseri, 2013)(Javidnia & Khoshneviszadeh, 2006). Moreover, findings from ethnobotanical studies showed that Ferulago angulata is used as a medicine for headaches, spleen, and snake bites (Monfared et al., 2006)(Shahabi et al., 2007), in addition to being an anti-diabetic, tonic, sedative, aphrodisiac, and anti-hemorrhoids (Hosseini et al., 2012). Our results are in agreement with many research groups(Hosseini et al., 2012)(Azarbani et al., 2014)(Golfakhrabadi et al., 2016)(Karimian et al., 2014), who confirmed the presence of phenolic and flavonoid compounds, tannins, alkaloids, carbohydrates, saponin, amino acids, and proteins as shown in Fig.2 as these aromatic compounds contain hydroxyl groups that are adjacent to an aromatic ring can play an important role as capping and reducing agent for CuO-NPs

α- Pinene

Myrcene

Hesperetin

Xanthotoxin

Isoimperatorin

Oxypeucedanin

β-sitosterol linoleate

Figure 3: Ferulago angulate (picture of the author) and chemical structures of common secondary metabolites.

2.4 PREPARATION OF COPPER OXIDE NANOPARTICLES:

CuO nanoparticles were synthesized by reducing copper (II) nitrate trihydrate (Cu(NO3)2.3H2O), using fresh leaves extracted from the Ferulago angulate plant (Kiflom Gebremedhn et al., 2019).

1 ml of Cu (NO₃)₂.3H₂O was dissolved in 50 ml of distilled water and then the solution was magnetically stirred for 5 minutes at room temperature. To synthesize CuO NPs, 1M sodium hydroxide (NaOH) was added to 20 ml of distilled water and stirred magnetically for 15 minutes at room temperature.

After combining the two solutions, 25 ml of Ferulago Angulate (Schltdl.) BOISS leaves extract was added to the mixing dropwise. Consequently, the mixture was stirred and heated at the temperature of 70°C for 2 hours duration until a colloidal solution was formed.

During the heating process solution's color changes from green to brown indicating the presence of CuO nanoparticles.

The mixture's pH was adjusted to 12±0.02 using

(a 3505-pH meter JANEWAY).

The brown-colored solution mixture was then calcined in a 300 °C furnace for 2 hours, crushed using a ceramic mortar and pestle to produce CuO NPs, and then kept in airtight containers for further characterization and investigations.

.2.5 CHARACTERIZATION OF COPPER OXIDE NANOPARTICLES:

The UV-Vis spectrophotometer (JANEWAY 6850), with A scanning wavelength range of (200-1100nm) was used to study the optical properties.

The analysis was performed by transferring 1 ml of sample powder into a quartz cell and analyzed at room temperature using distilled water as a reference solvent. The optical band gaps were calculated by using Tauc's plot (Maku et al., 2018) as shown below

(αհν)^1/γ=A(հν-Eg) (1)

where α is the absorption coefficient, hν photon energy, A is the absorption constant, Eg is the optical band gap energy, and γ is a factor that equals ½ for direct transmission and 2 for indirect transmission, depending on the nature of the electron transition (Mohammed, 2021).

Using an FTIR spectrophotometer (IRAffinity-1-SHAMADZO) with a wave number resolution of 1 cm^-1 in the range( 4000-500) cm^-1 in the transmittance mode, the functional groups of the extract and nanoparticles were identified. Also, it was used to identify the bioactive chemicals accountable for copper ion reduction and capping ( Gopalakrishnan et al., 2012; Mohamed, 2020; Renuga et al., 2020; Saif et al., 2016).

Using Cu(K) radiation (wavelength: 1.5406 Å) and operating at 40 kV and 40 mA at room temperature, an X-ray diffractometer (XRD) (ray diffraction system X-Pert Pro) revealed the crystal structure of NPs with a scanning range angles between 10 and 80 degrees. The average crystal size was calculated using the Debye-Scherrer formula. (Raj & Lawerence, 2018)

(2) where D is the size of the particle, k is a constant equal to 0.94, λ is the X-ray source's wavelength equal to (0.1541 nm), and β is the full width at half maximum (FWHM)(Salim, 2016).

The interplanar distance of CuO NPs for the preferred orientation peaks was measured using Bragg’s law (Dowsett et al., 2021)(Humphreys, 2013) as follows:

n λ=2dsinθ

(3)

The dislocation density (δ) and strain (ε) were determined by Equations (4) and (5), respectively(Abdulqudos & Abdulrahman, 2022).

(4)

(5)

Field-Emission Scanning electron microscopy (SEM-TESCAN VEGA 3 ) was utilized to investigate the nanoparticles' morphology. The average size of the fabricated CuO NPs was measured using FESEM along with energy-dispersive X-ray (EDX) for compositional analysis.

2.6 NPs Formation Mechanism:

The Biosynthesis of plant-mediated nanoparticles is divided into three phases: reduction, growth, and stabilization. Metal ions are recovered from their salt precursors by the interaction of plant metabolites; biomolecules that possess reduction capabilities, making this phase the most important. Nucleation of the reduced metal atoms occurs when the metal ions are reduced from their mono/divalent oxidation states to zero valent states. Further biological reduction of metal ions occurs during the growth phase when the metal atoms which have been separated begin to recombine to create metal nanoparticles. Although widespread nucleation has the potential to aggregate newly synthesized nanoparticles, changing their morphologies, the growth phase increases in the enhanced thermodynamic steadiness of nanoparticles. Nanoparticle stabilization is the last phase in the biosynthesis process. Capping the nanoparticles with plant metabolites gives them the most stable and steady morphology of nanoparticles. Nanoparticle stabilization is the last phase in the biosynthesis process. Capping the nanoparticles with plant metabolites gives them the most stable and steady morphology. Green synthesis, the formation NPs mechanism which used plants, is shown in Figure 4 (Barzinjy et al., 2020; Barzinjy & Azeez, 2020)

Figure (4): mechanism NPs fabrication

3. RESULTS AND DISCUSSION

3.1 Visual Observation:

The primary indication that CuO NPs were synthesized was the color change of the reaction mixture. Immediately after Ferulago angulates [Schltdl.] BOISS was added to the colorless 1 M Cu (NO₃)₂.3H₂O solution, and the color of the solution began to change to pale turquoise.

The solution's color changed from pale turquoise to pine green and finally to pale yellow when it came into contact with the NaOH solution. The appearance of these color changes, which are brought on by the excitation of surface plasmon resonance in the metal oxide nanoparticles, is an indication that CuO NPs have been fabricated (Kiflom Gebremedhn et al., 2019; Berra et al., 2018). Also, the color change can be related to the oscillation modes of conduction electrons and incident electromagnetic radiation (Berra et al.,2018) which is an indication of CuO Ns formation.

In contrast, the leaf extract of Ferulago angulates [Schltdl.] BOISS and the Cu (NO3)₂.3H2O solution remained unchanged in color (Figure 1 b).

Figure (5): Steps for Copper Oxide Nanoparticles Preparation where (a) Cu (NO₃)₂.3H₂O, (b)NaOH, (c) Cu (NO₃)₂.3H₂O and NaOH mixture, (d) Ferulago angulate [ Schltdl.] BOISS Leaves Extract, (e,f) Cu(NO₃)₂.3H₂O, NaOH and, Ferulago angulate [ Schltdl.] BOISS Leaves Extract mixture and, (g,h) CuO NPs

3.2 Phytochemical analysis of Ferulago angulate [ Schltdl.] BOISS leaf extract:

Standard test methods were used to analyze the chemical components of an aqueous leaf extract of Ferulago angulate (Schltdl.) BOISS to verify the presence of active phytochemicals (Schltdl.).

Tannins, alkaloids, flavonoids, phenols, and anthocyanins were found, based on the results of the phytochemical analysis. (Table.1) (Nafeesa et al, 2017; Tyagi, 2017).

Table 1: Phytochemical analysis

Plant Metabolite	Ferulago angulate [ Schltdl.] BOISS leaf extract results
Flavonoid	+
Carbohydrate	+
Alkaloid	+
Tannin	+
Saponin	+
Proteins and amino acid	+
Phenolic	+

3.3 Fourier Transform Infrared (FTIR) Analysis:

FTIR spectra were utilized to study the structure, identification, functional groups, and chemical composition of CuO nanoparticles. Spectra of the solid phase obtained by FTIR were collected between 4000 and 500 cm^-1 and compared with the standard FTIR spectra( Gopalakrishnan et al., 2012; Mohamed, 2020; Renuga et al., 2020; Saif et al., 2016).

Figure (6) shows the FTIR spectra of the Ferulago angulate (Schltdl.) BOISS leaf extract, and Table 3 (provides a list of the functional groups that correspond to those spectra).

Figure (6): shows the FTIR spectrum of a leaf extract from Ferulago angulate (Schltdl.) BOISS

Table 2. The functional groups exist in the Ferulago angulate [ Schltdl.] BOISS leaf extract

pH	Wavenumber (cm^-1)	Functional Groups
8	3344.57	N-H aliphatic primary amine
	2353.15	O=C=O carbon dioxide
	1786.08	C=O conjugated acid halide
	1624.06	N-H amine
	1342.46	O-H phenol
	829.39	C=C alkene
	779.24	C-H Alkynes
	609.5	C-Br stretching
10	1543.05	N-O nitro compound
	1342.46	O-H phenol
	829.39	C=C alkene
	779.24	C-H Alkynes
	609.5	C-Br stretching
	568.36	Cu-O Vibrations
	532.35	Cu-O Vibrations
12	1786.08	C=O acid halide
	1342.46	O-H phenol
	829.39	C-H Alkyne
	609.5	C-Br stretching
	568.36	Cu-O Vibrations
	532.35	Cu-O Vibrations
13	3344.57	N-H primary aliphatic amine
	2434.3	N-H primary amine
	1624.06	C-Br stretching
	1342.46	O-H phenol
	829.39	C=C alkene
	779.24	C-H Alkynes
	609.5	C-Br stretching
	568.36	Cu-O Vibrations
	532.35	Cu-O Vibrations

Figure (7) shows the FTIR spectrum of CuO NPs synthesized at different pH values and Table (3) lists their functional groups.

Figure (7) shows weak CuO vibration peaks at 532.35 cm^-1, demonstrating copper oxide nanoparticle production. After synthesizing nanoparticles, polyphenol absorption peaks at 3251.98, 1631.78, 983.69, 894.97, and 586.36 cm^-1 indicate that Ferulago angulate [Schltdl.] BOISS extract leaves are reduces and stabilize copper oxide NPs(Berra et al., 2018).

Table 3. The functional groups exist in the CuO NPs formed at different pH

Wavenumber (cm^-1)	Functional Group
3251.98	O-H bond of the Hydroxyl Groups (Alcohol)
1631.78	C=C conjugated Alkene
983.69	C=C Alkene
894.97	C=C Alkene
586.36	C-X Chloride

At different pH values copper oxide nanoparticles synthesis have similar functional groups but different peak intensities and frequencies. After the synthesis of CuO NPs, the Ferulago angulata [Schltdl.] BOISS extract's C=C stretching vibration observed at 1631.78 cm⁻¹ reduces and shifts to 1624.06 cm^-1.

The O=H bending vibrations at 1342.6 cm^-1 are correlated with the decrease in peak intensity and the increase in frequency that results from the synthesis of CuO NPs. In addition, two peaks observed at 532.35 cm^-1 and 568.36 cm^-1 may be ascribed to

Cu-O vibrations, respectively, which agree with previous

works done by other researchers (Saif et al., 2016; Aminuzzaman et al., 2017; Vishveshvar et al., 2018; (Rehman et al., 2022).

As pH increases, aqueous extract peaks shift. Thus, biomolecules and nanoparticles of various sizes and shapes are affected by the solution's pH. This reveals that copper ions initially attach to the biomolecules' surfaces (Oza et al., 2020)

3.4 Structural Analysis:

An X-ray diffractometer with XRD patterns ranging from 10^oto 80^o was used to confirm the crystalline phase of the produced CuO NPs.

Figure 8 shows typical XRD patterns for created copper oxide nanoparticles. The spectra reveal a monoclinic cupric oxide (CuO) and Cu₂O combination. The peaks observed at 2theta values of 32.45°, 35.75°, 35.9°, 36.45°, 39.55°, 48.6°, and 56.95°, respectively correspond to the reflection from crystal planes of (110), (002), (-111), (111), (200), (20-2), and (021) of CuO monoclinic phase. Those planes match the (CPDS Card No. 10200, 10199, ICSD Card No.01-074-1021,01-078-0428, and Card No.0011639). The peaks at 2θ ° values of 29.85°, 36.95°, and 42.85° match the planes (110), (111), and (200) of cubic Cu₂O crystalline structure (ICDD Card No. 00-003-0898).

Figure (8): XRD patterns of CuO NPs for different pH.

Figure (8) shows that CuO (110) preferred orientation peak intensity increase with increasing pH values from 8 to 12.

Due to the nanocrystal structure of the CuO NPs, the position, height, and width of the diffraction peaks are all controlled by this property. The potential of grain coalescence has a role in the decrease in FWHM that occurs with an increase in pH.

The highly crystalline nature of nanoparticles is demonstrated by the sharp and narrow diffraction peaks.

The observed, standard, and calculated values of some XRD parameters for CuO thin films for the preferential orientation plane (110) using equations (2,3,4,5) are shown in Tables 4 and 5.

Table 4. The observed and standard values of XRD data for CuO NPs

pH	Observed 2q (º)	Standard 2q (º)	Observed d (nm)	Standard d (nm)
10	32.3	32.54	2.768	2.748
12	33.05	32.54	2.7148	2.748
13	32.45	32.54	2.759	2.748

Table 5 Calculated values of the structural parameters of CuO NPs at different PH values

Ph	2q(º)	β	D(nm)	e(´10^-7)	ẟ(´10^-8)
10	32.3	0.24	33.60	1.03	8.85
12	33.05	0.19	42.09	0.823	5.64
13	32.45	0.19	42.02	0.824	5.66

The X-ray diffraction technique verified the presence of nanoparticles with sizes in the ranges of (33-42) nm. However, the grain sizes estimated by Scherrer’s equation were smaller than those observed in the SEM analysis (see Table 5 and Fig.8). This discrepancy can be due to the limitations of Scherrer’s equation for the calculation of crystallite size. Although the CuO crystals grow larger due to annealing, recrystallization, and agglomeration of tiny crystallites, Scherrer’s equation is not capable of estimating these large values (crystallite size saturation).

3.5 Morphological Analysis:

Biosynthesized CuO NPs of various surface morphologies and compositional analyses are shown in Figure (9,10) at various pH values.Figures9 and10 respectively show the SEM and EDX images of the biosynthesized CuO NPs at different pH values.

Figure (9): SEM photographs of CuO NPs for different pH of a) 8, b) 10, c) 12, and (d)13

Figure 9a (pH=8) shows the sheet-like morphology with an average sheet size in the range of 376.77 nm and is covered by tiny crystallites (NPs) of an average size of 17.64 nm. In Figure 9b (pH=10), a rough sheet-over-sheet morphology with an overall average size of 541.64 nm was observed. These sheets also are formed due to the agglomeration of tiny crystallites or nanoparticles with an average size of 22.48 nm. Figure 9c (pH =12), shows the non-uniform distribution of agglomerated tiny crystallites or nanoparticles with an average size of 35.43nm. At pH 13 (Figure 9d), irregular grain-shaped morphology was observed. The average grain size was measured to be 486.61nm, also a closer look indicates that these grains are covered by tiny crystallites or NPs of average size in the range of 17.07nm. The morphological study indicates that the pH variation has a prominent effect on the size and shape of the fabricated CuO NPs.

Figure (10): The elemental composition of CuO NPs using EDX analysis with different pH of (a)pH=8, (b)pH=10 (c) pH=12, and (d) pH=13.

Figures 10 (a,b,c, and d) show the EDX images of CuO biosynthesized at pH values of 8, 10, 12, and 13, respectively.

Figure 10 (a,b,c, and d) show the EDX images of CuO biosynthesized at pH values of 8,10, 12, and 13, respectively. In all EDX images, oxygen-richness (oxygen domination) was observed for the synthesized CuO samples. The EDX results also show that with increasing pH value from 8 to 12 a reduction in oxygen percentage from 76.8% to 61.8% and an increment in Cu percentage from 23.2% to 38.16 % was observed. Based on these results one should expect the energy bandgap reduction due to the reduction in the oxygen incorporation and increment in Cu incorporation which is in agreement with the the band gap values measurement shown in Section 3.6.2 (see Fig. 13 and Table 6).

Even though increasing the pH value resulted in increasing the Cu percentage which lead to band gap reduction but at the same time it also resulted in the reduction of the grain size which can cause band gap increment.

(Fishman et al., 2016);(Ben Amor et al., 2022),(Oza et al., 2020).

3.6 Optical properties of the CuO NPs:

The energy bandgap was studied using absorption spectra

(Dhineshbabu & Vetumperumal, 2016).

The UV–Vis examination of pure Ferulago angulate [ Schltdl.] BOISS plant extract showed a strong absorbance peak below the wavelength of 424.53nm as shown in Figure 11.

Figure (11): The absorbance spectra of pure Ferulago angulate [ Schltdl.] BOISS plant extract.

Two methods, one visual observation of color change is used to identify the type of nanoparticles that have been targeted for synthesis from a certain plant pattern (section 3.1), and the other UV–Vis analysis can be used to identify the type of nanoparticles that have been targeted for synthesis from a certain plant.

3.6.1 Optimization of pH of the Mixture of Ferulago angulate [ Schltdl.] BOISS Extract and the Precursor:

The pH value of the solution affects the bioreduction of the copper nitrate solution. The precursor and extract had pH values that were different from one another. The intensity of their peak and the redshift of their respective max values were optimized for the CuO NPs produced at various pH values (8, 10, 12, and 13). All the pH shows sharp absorption edges presenting good quality copper oxide semiconductor material as shown in Figure (12). At pH = 8, the optimum result for the synthesis of CuO NPs was shown in Figure (10).

Fig(12): The absorbance spectra of CuO NPs formed at pH (a) 8, (b) 10, (c) 12, and (d) 13.

For pH 8 to 12, the plasmon resonance was stronger. When compared to pH = 8, the peak at pH = 12 was weaker but still strong. The reduction in the particle size might be responsible for the highest blue shift in the surface plasmon resonance peak, which occurred around the maximum value when pH was equal to 10(Suresh et al., 2014).

3.6.2 Energy band gap calculations:

The electronic and optical properties of materials can change when the sample size is reduced to 10 nm or less. This phenomenon is known as the quantum confinement effect. The quantum confinement effect can be observed when the size of the particle is smaller than the wavelength of the electron (Bohr radius). In NPs when quantum confinement occurs this will lead to a transition from continuous to discrete energy levels. However, when the dimensions of the material are increased (greater than Bohr radius) the transition to a discrete energy level will not occur. For this reason, the quantum confinement effect leads to bandgap widening as the particle size reduces which is mostly observed for NPs semiconductor compounds in groups I-VI, II-V, III-V, and IV-VI (Kamarulzaman et al., 2015).

Tauc's plot technique was used to calculate the energy bandgap (Eg) of biosynthesized CuO NPs using the equation (1).

The energy bandgap for biosynthesized CuO NPS was calculated by the plotting of (αhn)² versus photon energy (hn) for different parameters as shown in Fig.(13 ).

Sharp absorption h has been observed for all CuO fabricated at different pH values which represents a good quality CuO semiconductor material. It was observed that as the pH values increase the absorption edge shift toward lower energy photons.

Figure. (13): Plots of (αhυ)² versus hυ for different pH values.

The calculated energy gap (Eg) using the relationship (1) is listed in Table (6)

.Table 6. The variation of Eg with pH value

pH	Eg ( ± 0.02) eV
8	3.63
10	3.60
12	3.53
13	3.39

From Table (6), it can be seen that the energy gap increase with increased pH.

The band gap widening can be also attributed to the larger downward shift of the VB (Kamarulzaman et al., 2015).

Many reports show that CuO has both direct and indirect bandgap depending on the synthesis method. The CuO NPs band gap values reported in this study are in agreement with those reported in the literature (Usha et al., 2015);(Tripathi et al., 2020)

3.7 The impact of pH value on the shape, size, and crystallinity... of CuO NPs

The pH which determines the level of acidity and basicity of the reaction medium has been reported to have an important impact on the shape, size, purity as well as crystallinity of the synthesized CuO NPs extracted from plant materials which are in agreement with the observations in this study (See Figure 8 and Table 5). Moreover, it has been reported that the pH variation has a significant impact on the capping and stabilizing abilities of the NPs preparation process. During the nucleation and growth stage for NPs, the local surface can be caused by protonation and deprotonation of the molecular atom as a result of pH variation (Ben Amor et al., 2022). Also, in the alkaline pH environment, the NPs are distributed and formed as a cluster in the colloidal stage preventing aggregation.

Based on XRD results, the smaller FWHM(β) and higher intensity XRD peaks were observed for the CuO NPs grown at higher pH values of 12 and 13. The smaller FWHM(β) means a higher crystallinity. Also, the effect of pH on the morphology of the CuO NPs is discussed in section (3.5).

4. CONCLUSION

In this study, the CuO NPs were successfully prepared under different pH values using Ferulago angulate leaves from the Gara mountain (Southeast of Duhok city) in the Kurdistan region.

The XRD data reveals the polycrystalline nature of the CuO NPs with an average grain size in the range of (33-42) nm. UV-vis study showed a sharp absorption edge indicating good quality CuO semiconductor compound fabrication with an energy gap close to those of bulk CuO. As the pH value increased, there was a corresponding reduction in the energy band gap values. FTIR shows different absorption peaks reflecting its complex structure due to biomolecules. FESEM images indicated that pH variation has a prominent effect on the shape and size of the CuO NPs which completely altered the CuO morphology (different morphology under different pH values fabrication conditions). Results obtained from EDX spectra reveal the O-richness of the prepared CuO suitable for wide band gap applications. FESEM images showed different morphology under different pH values.

Author Contributions: Conceptualization, Raghad Y. Mohammed; methodology, Raghad Y. Mohammed; software, Saniya Sadullah Omar; validation, Raghad Y. Mohammed and Saniya Sadullah Omar; formal analysis, Raghad Y. Mohammed; investigation, Raghad Y. Mohammed; resources, Raghad Y. Mohammed; data curation, Saniya Sadullah Omar; writing—original draft preparation, Saniya Sadullah Omar; writing—review and editing, Raghad Y. Mohammed; visualization, Raghad Y. Mohammed and Saniya Sadullah Omar; supervision, Raghad Y. Mohammed; project administration, Raghad Y. Mohammed; funding acquisition, University of Duhok. All authors have read and agreed to the published version of the manuscript.

Funding: This work was sponsored by the Department of Physics, College of Science, University of Duhok. This research received no external funding.

Acknowledgments: The authors would like to acknowledge the Department of Physics, College of Science, University of Duhok.

Conflicts of Interest: The authors declare no conflict of interest.

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