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Abstract

Multi-phase metal oxides nanocomposites (NCs) have attracted considerable attention due to their extraordinary properties and novel applications over monometallic ones. Hence, trimetallic oxides nanoparticles (NPs) are preferred because of their immensely improved optical, catalytic, and biological properties, but few materials have been reported. Besides, glycine is an excellent structure-directing agent for NPs production with tailored physicochemical properties. Thus, in this work, a novel tri-phase CuO–Fe₂O₃–MgO (1:1:1) NCs was prepared via a sol-gel method in the presence of glycine as a fuel. The obtained NCs were characterized by Fourier transmission infrared, X-ray diffraction (XRD), Scanning electron micrographs, and UV-Vis. The XRD analysis emphasized the formation of NCs with monoclinic CuO, cubic MgO, hexagonal Fe₂O₃, and tetragonal CuFe₂O₄ crystals. The average crystallite size (D) was in the order of 10th of nm as computed by Scherrer method, with ternary phase seemingly affect the straightforward influence of glycine fuel concentration on the final crystallite sizes. UV-Vis analysis indicates two optical energy bandgaps which increased as glycine concentration increase. The antibacterial test against Staphylococcus aureus and Escherichia coli bacteria revealed comparable activity to that of Azithromycin standard drug, which increased with glycine concentration increase. The glycine-based tailored structural, optical, and biological properties of such trimetallic NCs making them of considerable candidate for certain applications development, possibly electronics and antibiotics; a case that encourage further investigations.

Keywords

nanocomposite optical antibacterial sol-gel

Introduction

Metal oxide nanocomposites (NCs) have attracted great attention in recent years due to their unique properties such as optical, electrical, mechanical, photocatalytic, thermal, and structural.^1–3 They could be of two, three or more oxides present in a nanometer scale and might be involved in many applications, including solar cell, battery materials, UV detectors, gas sensors, photovoltaic devices, and fuel cells.^4–7 By combining different metal oxides, various properties of individuals could be improved and a new track of research for biological, optoelectronics, thermal, and electrical applications could open up.^5,8–10 Adding a new phase to a composite material can alter its electronic properties. Metal oxide NCs can be prepared through several routes, like hydrothermal,¹⁰ co-precipitation,¹¹ self-combustion,¹² ultrasonic-assisted method,¹³ etc. Among these, sol-gel method¹⁴ is popular one to fabricate metal oxide NCs. It is a low cost, fast, and facile to carry out with less expensive devices.

The metal oxide CuO is a p-type semiconductor with optical bandgap of 1.22 eV. It possesses great optical, structural, and electrical properties and, additionally, being nontoxic and uncostly prepared. It is involved in several applications such as supercapacitor, superconductor, catalysis, gas sensing, and photocatalytic activity.^12,15–21 MgO is nontoxic and inexpensive as well, demonstrating a wider optical bandgap of 7.3 eV, high surface reactivity, high adsorption capacity, and unique physicochemical properties.^1,2,22–24 Fe₂O₃ is a n-type semiconductor metal oxide with energy bandgap of 2.1 eV. It is chemically stable, naturally abundant, benefit several applications, and most importantly it is cheap and safe material.^25–27

Globally, bacteria induced diseases are one of the leading causes of human illness. Food contaminated with bacteria like Staphylococcus aureus (S. aureus) or Escherichia coli (E. coli) can cause serious diseases.²⁸ Over the last two decades, many of the antibiotics utilized to cure infectious diseases have failed to work due to bacterial resistance.²⁹ To outdo this problem, the preparation of new inorganic antibacterial agents is critical for fighting bacteria resistance. Several articles have reported that metal oxide NCs possess promising antibacterial potential due to their large surface areas and generation of charged radicals that inhibit bacterial growth.^11,30–33

According to literature,^34,35 amino acids can serve as useful facilitator in term of nanoparticles (NPs) synthesis. They provide strong bonding with particles due to their zwitterionic nature expressed in their amine and carboxyl groups protonation-deprotonation as the pH changed. Adding of such surfactant to metal oxide solution decreases crystal growth and, according to the agent type as well as the synthesis conditions, crystallization rate, and growth direction could be fabricated, thus allowing production of target NPs sizes and shapes. Glycine, as the simplest stable amino acid, have been applied as a capping agent in the synthesis of iron oxide magnetic NPs,^35,36 which proven possible NPs controlled morphology. However, different amino acids could induce different morphology.³⁷

In this study, glycine was applied as a structure-directing agent for obtaining a tri-phase CuO–Fe₂O₃–MgO NCs, and the effect of its concentrations on the end-properties of the synthesized NCs were investigated. Therefore, the structural, morphological, and optical properties as well as the biological activity against both Gram-positive and Gram-negative bacteria were studied.

Materials and methods

Materials

Iron (III) nitrate nonahydrate (Fe(NO₃)_3·9H₂O; 97%) and magnesium (II) nitrate hexahydrate (Mg(NO₃)_2·6H₂O; 97%) were obtained from BDH Chemical Ltd (Pool, England, UK). Copper (II) nitrate hexahydrate (Cu(NO₃)_2·6H₂O; 98%) and glycine (≥98.5%) were procured from Sigma–Aldrich (Darmstadt, Germany). Sodium hydroxide (NaOH, 98%) was bought from Fisher Chemical (Loughborough, UK). All materials were used as received unless otherwise stated; and double distilled water was used wherever needed.

Preparation glycine-mediated tri-phase CuO–Fe₂O₃–MgO nanocomposite

Metal oxides NPs were obtained using sol-gel methods.³⁸ Therefore, salts solutions (0.7 M) of each Fe(NO₃)_3·9H₂O (4.24 g), Cu(NO₃)_2·6H₂O (2.54 g), and Mg(NO₃)_2·6H₂O (2.69 g) were separately prepared in 15 ml distilled water, then mixed with stirring for 30 min at room temperature (termed solution I, SI). Subsequently, 20 ml of 1.0 M glycine solution (SII) and 15 ml of 6 M NaOH (SIII) were poured into SI, followed by heating at 90°C for about 60 min during which precipitate of CuO–Fe₂O₃–MgO started to form. The obtained dry mass was further calcined at 800°C for 90 min and termed G1. NCs G1.5 and G2 were prepared similarly as G1 using 1.5 and 2.0 M of glycine solution (SII), respectively. A schematic illustration for the experimental process is given in Figure 1.

Figure 1.

Schematic presentation of CuO–Fe2O3–MgO NCs synthesis, characterization, and application.

Characterization techniques

The X-ray diffraction (XRD) patterns of G1, G1.5, and G2 were recorded using an XD-2 X-ray diffractometer (Beijing Purkinje General Instrument Co., Ltd, Beijing, China), with CuKα1 radiation of λ = 1.54 Å, in a 2θ range of 10–80 and scanning rate of 0.02 min⁻¹. Scanning electron micrographs (SEM) were imaged in a JSM-6360 LV scanning electron microscope (Jeol Ltd, Tokyo, Japan). Vibration spectra were analyzed using a Nicolet iS10 Fourier transmission infrared (FTIR) spectrometer from Thermo Scientific (Madison, WI, USA) which equipped with an attenuated total reflection (ATR, diamond crystal) accessory, over the range of 650–4000 cm⁻¹, with 32 scans per spectrum and 4 cm⁻¹ scanning resolution at room temperature. UV-Vis spectrophotometer (Hitachi-U3900; Tokyo, Japan) was used for recording electronic spectra over the range of 200–800 nm at room temperature.

Antibacterial test

In vitro antibacterial activity of CuO–Fe₂O₃–MgO NCs at concentration of 100, 200, and 400 mg/ml was carried out using the disc-diffusion method,^39,40 against Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli) in reference to Azithromycin (AzM) as standard drug. Bacteria of the species S. aureus and E. coli were kind gift from Al-Jarfi medical Lab (Thamar, Yemen). The bacteria were cultured and swapped in Mueller Hinton agar medium, and discs having 6 mm diameter were prepared by punching Whatman filter paper. Solutions of various concentrations of NCs were fabricated singly. After that, paper discs were immersed in the test NCs solutions and positioned on the plates where bacteria lie. Simultaneously, discs for AzM (positive control) and DW (negative control) were also prepared and treated similarly as NCs. The plates were incubated for 20 h at 35–37°C. The susceptibility of bacteria to NCs was determined by measuring the zone of inhibition (ZOI) in millimeter.⁴¹

Results and discussion

Structural properties

FTIR analysis

The synthesized trimetallic oxides NCs were characterized for their structure and composition using FTIR technique. The spectra of the fabricated three groups (G1, G1.5, and G2) are gathered in Figure 2. As can be seen, the broad band centered at about 3450 cm⁻¹ is assignable for O–H stretching vibrations, for which the bending mode can be observed at 1643 cm⁻¹, indicating metal–hydroxide structure.⁴² The presence of OH groups on the sample surface is due to a common sorption event of water molecules from the atmosphere.³¹ According to literature, the strong band around 1350–1500 cm⁻¹ is associated with carbonate ions weakly attached to the sample surface.^31,43 Bands for oxygen–metal-oxygen (O–M–O) and metal-oxygen (M–O) are commonly traced in the region 430–1004 cm⁻¹.^1,13 Thus, the peak at 582–596 cm⁻¹ is for Fe–O and Cu–O and 435 cm⁻¹ for Mg–O. Overton stretching bands for metal oxides (M–O) were at higher frequencies; thus, the ones on the range 1004–864 cm⁻¹ can be related to such overtone bands as reported elsewhere.⁴⁴ Meanwhile, no traceable bands for organic impurity in the FTIR spectra that possibly sourced by glycine fragments, few weak bands in the finger print region may indicate negligible quantity of carbons which could be of carbonate type, with no evidence of aliphatic fragments observed at 3000–2750 cm⁻¹.

Figure 2.

FTIR spectra of CuO–Fe₂O₃–MgO NCs (G1, G1.5, and G2) synthesized at various glycine concentrations.

XRD analysis

The XRD patterns of CuO–Fe₂O₃–MgO NCs, fabricated at various concentrations of glycine, have displayed four identifiable phases for CuO, Fe₂O₃, MgO, and CuFe₂O₄ oxides as shown in Figure 3. The diffraction peaks were matched with JCPDS files of CuO (74–1021), Fe₂O₃ (76–1821), MgO (45–0946), and CuFe₂O₄ (72–1174) with monoclinic, hexagonal, cubic, and tetragonal crystals, respectively, indicating the polycrystalline nature of the synthesized materials. The average crystallite size (D, nm) of G1, G1.5, and G2 samples were computed by Scherrer’s law and Bragg’s law as expressed by equations (1) and (2)^45,46

D = \frac{0.9 λ}{β \cos θ}

(1)

n λ = 2 d s i n θ

(2)

where D is the size of crystalline domain, λ (0.154 nm) is the incident radiation wavelength, θ is the diffraction angle, 𝛽 is the full–width at half maximum, d-spacing Å is the inter-atomic spacing, and n is the order of reflection. The dislocation density (δ) was evaluated by the relation given in equation (3).¹³ The averaged values of crystallite size and dislocation density for the prepared oxides NCs are tabulated in Table 1

δ = \frac{1}{D^{2}}

(3)

Figure 3.

XRD patterns of CuO–Fe₂O₃–MgO nanocomposites at different glycine concentrations.

Table 1.

Structural parameters of CuO–Fe₂O₃–MgO nanocomposites determined from XRD analysis.

Sample	Oxides	hkl	2θ°	d-space (Å)	FWHM (degree)	Scherrer crystallite size (D, nm)	Scherrer average (D, nm)	Average dislocation δ × 10⁻⁴ (nm⁻²)
G1	CuO	110	32.721	2.7346	0.115	72.00141	60.425	2.738
		−111	35.740	2.5102	0.185	45.12186
		111	38.979	2.3088	0.192	43.89385
		−202	48.883	1.8617	0.153	57.03576
		112	51.698	1.7788	0.105	84.07214
	Fe₂O₃	008	31.684	2.8217	0.140	58.98988	46.551	4.615
		107	33.477	2.6224	0.181	45.83643
		11-4	35.740	2.5102	0.185	45.12186
		202	38.119	2.3589	0.216	38.9146
		203	38.979	2.3088	0.192	43.89385
	MgO	200	43.075	2.0982	0.178	47.98302	76.808	1.695
	MgO	220	62.556	1.4836	0.088	105.6229	76.808	1.695
	CuFe₂O₄	202	29.721	3.0035	0.229	35.89465	53.302	3.519
		004	41.317	2.1833	0.170	49.94485
		303	45.244	2.0026	0.129	66.71892
		501	56.930	1.6161	0.149	60.64822
G1.5	CuO	110	32.723	2.7344	0.372	22.25862	32.044	9.738
		−111	36.000	2.4927	0.223	37.4604
		111	39.241	2.2931	0.191	44.15947
		−202	49.081	1.8546	0.155	56.3441
		112	51.504	1.7729	0.192	45.93938
	Fe₂O₃	008	31.961	2.7979	0.161	51.33087	43.259	5.353
		107	34.460	2.6005	0.181	45.95656
		11-4	36.00	2.4927	0.223	37.4604
		202	38.361	2.3445	0.225	37.38534
		203	39.241	2.2939	0.191	44.15947
	MgO	111	37.077	2.4227	0.105	79.80573	103.404	9.352
		200	42.765	2.1127	0.067	127.3419
		220	62.159	1.4921	0.090	103.0597
	CuFe₂O₄	202	30.051	2.9712	0.203	40.5231	63.255	2.499
		004	41.608	2.1687	0.142	59.85057
		303	45.425	1.9950	0.478	18.0176
		501	56.544	1.6262	0.067	134.6296
G2	CuO	110	32.349	2.7652	0.209	39.58053	37.883	6.968
		−111	36.004	2.4924	0.223	37.46083
		111	39.240	2.2940	0.266	31.70839
		−202	48.877	1.8619	0.180	48.47925
		112	51.464	1.7742	0.274	32.18569
	Fe₂O₃	008	32.349	2.7652	0.209	38.02648	35.338	8.008
		107	34.521	2.5960	0.070	35.63794
		11-4	36.004	2.4924	0.223	29.87632
		202	38.439	2.3399	0.263	44.14932
		203	39.240	2.2940	0.266	29.00297
	MgO	111	37.164	2.4172	0.126	66.52171	56.761	3.104
		200	42.979	2.1027	0.181	47.17216
		220	62.267	1.4898	0.164	56.58926
	CuFe₂O₄	202	30.588	2.9203	0.096	85.79822	56.696	3.111
		004	41.560	2.1711	0.201	42.27577
		303	45.484	1.9925	0.265	32.50668
		501	56.161	1.6364	0.136	66.20636

It is clear that the averaged D of Fe₂O₃, CuFe₂O₄, CuO, and MgO were unsystematically changed with increasing of glycine concentration. This is due to the contribution of ternary phase (CuO, MgO, and Fe₂O₃ oxides) in aggregation process as a consequence of the ionic radii differences between Cu (0.073 nm),⁴⁷ Mg (0.059 nm),⁴⁸ and Fe (0.064 nm),⁴⁹ as well as the effect of electronegativity of metals Cu (1.90), Mg (1.31), and Fe (1.83) in production of metal oxide molecules. It is obvious that with increasing in glycine fuel–mediating synthesis have resulted in crystalline size decrease, the case that supposedly due to spacer abundance in the media, leading to large number of nuclei for crystal growth.

Khodair et al. have studied the effect of glycine on the crystallite size (D) of MgO NPs³⁸ and reported that the NPs increased as the glycine concentration increased. The increase in the D was attributed to the small δ value due to the inverse relation between δ and D. According to the X-Ray diffraction data, an increase in the glycine concentration leads to the variation in the crystal lattice parameters and a decrease in the crystallites size as shown in Table 1. This result leads to the existence of additional distortions and vacancies in the structure.

SEM analysis

The surface texture of CuO–Fe₂O₃–MgO nanocomposite annealed at 800°C is displayed in Figure 4. It can be seen that the particles were almost in spherical shape ad agglomerated into visible dense structure. Meanwhile, particles in the nano range still observable, analyzed SEM image scale is hardly describing the nano structure. Nevertheless, the homogeneity of the surface may indicate advanced distribution facilitated by the glycine-media during the sol-gel production of multi-phase oxides which, in turn, could be reflected in the properties of the calcined final powders. Moreover, NCs produced at lower glycine concentration resulted in a more aggregate texture, as seen for G1 compared to G2. The result revealed concentration-dependent particle sizes of the synthesized NCs with countable particles in the order 100th nm.

Figure 4.

SEM image of glycine-mediated synthesized CuO–Fe₂O₃–MgO nanocomposite G1, G1.5, and G2.

Optical properties

Electronic spectra

Figure 5(a) displays the optical absorption spectra of CuO–Fe₂O₃–MgO NCs prepared at various glycine-mediated concentrations of 1, 1.5, and 2 M. All the spectra demonstrated the presence of at least two peaks (at about 300 and 370 nm), of which the ones at 373, 363, and 305 nm where the clearer peaks in G1, G1.5, and G2, respectively. The absorption was found to decrease as the wavelength increased, and that might be a result of internal electric fields or distortion of lattice due to strain. Moreover, the improved absorption spectra in the visible region could suggest photocatalytic activity enhancement toward certain pollutants, a property that previously noticed.³¹

Figure 5.

(a) Absorbance and (b) absorption coefficient (𝛼) vs. wavelength for of CuO–Fe₂O₃–MgO NCs at different glycine concentrations.

The absorption coefficient (α) was evaluated using equation (4),⁵⁰ where A is the absorbance and t is the thickness

α (λ) = \frac{2.303 A}{t}

(4)

The variation of absorption coefficient for the three NCs with incident wavelength is shown in Figure 5(b). It was observed that the absorption coefficient exponentially decreased as the wavelength increased, a behavior that might be caused by distortion of lattice as a result of charge carrier’s inelastic scattering driven by phonons.

Extinction coefficient, refractive index, and optical conductivity

The extinction coefficient (k), refractive index (n), and optical conductivity (σ_opt) were evaluated using the relations given in equation (5)–(7), respectively,^51,52 and their values were depicted in Figure 6(a)–(c)

k = \frac{α λ}{4 π}

(5)

n = \frac{1}{T_{s}} + \sqrt{\frac{1}{T_{s} - 1}}

(6)

σ_{o p t} = \frac{α n c}{4 π}

(7)

where 𝛼λ were defined above, k is the extension coefficient, n is the refractive index, T_s is the transmittance, σ_opt is the optical conductivity, and c is the speed of light (3 × 10⁸ m/s).

Figure 6.

(a) Extinction coefficient (k) and (b) refractive index (n) vs. wavelength (nm), and (c) optical conductivity (σ) vs. photon energy for CuO–Fe₂O₃–MgO NCs.

Extinction coefficient (k) is an essential optical constant that could express the fraction of light lost per unit distance in the testing material medium.⁵¹ As shown in Figure 6(a), the extinction coefficient (k) increase in the visible region which specify good optical properties of the prepared tri-phase metal oxides at this region. The refractive index (n) gives information regarding ions polarization, phase velocity of light and local field inside the optical material. In Figure 6(b), the n was noticeably increased at the short lower wavelength, while decreased as the incident light approaching the UV region.

Optical conductivity σ_opt is one of the basic properties of the material which depends on the 𝛼, n, k, and c. Figure 6(c) illustrates the changes in σ_opt as a function of photon energy (eV) for all the prepared NCs. It possesses a maximum value in high energy regions which appoint that the prepared products can be utilized in optical applications.

Optical energy gap (E_g)

The electronic data of the synthesized CuO–Fe₂O₃–MgO NCs can be employed to determine bandgap energy (E_g) as well. The E_g values for the direct transition can be computed via Tauc’s equation (8)^6,51

α h v = A {(h v - E_{g})}^{n}

(8)

where 𝛼hν are the absorption coefficient, plank constant and photon frequency, respectively, A is constant and E_g is the optical bandgap. Thus, the E_g values of the synthesized CuO–Fe₂O₃–MgO NCs (G1, G1.5, and G2) were computed and illustrated in Figure 7 and Table 2. The E_g values lie between CuO (1.2 eV), Fe₂O₃ (2.2 eV), and MgO (7.2 eV). For each sample, two energy bandgap (E_g) were record. The first (E_g1) can be attributed to Fe₂O₃ and CuO NPs while the second (E_g2) can be ascribed to the existence of MgO NPs.¹ In comparison to individual oxides NPs reported in literature,^19,25,31,38 the CuO–Fe₂O₃–MgO NCs absorbance is significantly higher in the visible region as a result of such composition process.

Figure 7.

Optical band gap plots for CuO–Fe₂O₃–MgO NCs at different glycine concentrations.

Table 2.

Optical energy measurements of prepared samples.

Samples	Energy band gap, E_g (eV)
Samples	E_g1	E_g2
G1	2.48	2.71
G1.5	2.68	2.97
G2	2.74	3.07

Generally, the E_g values increase as fuel (glycine) concentration increase because of the decrease in the crystallite size which emphasized the nanosized nature of the synthesized NCs. Also, these results confirmed the existence quantum confinement of the fabricated samples. The optical results indicated that the CuO–Fe₂O₃–MgO NCs are convenient substances for many applications such as optoelectronics photocatalysis and thermoelectric.^1,6

Antibacterial activity

The antibacterial activity of the synthesized NCs at various concentrations was assessed in term of zone of inhibition (mm) of disk diffusion assay against S. aureus and E. coli bacteria and in reference to AzM and DW as positive and negative controls. The resulting ZOI are summarized in Table 3 and selected plate images of experimental Petri dishes were given in Figure 8. It can be seen that the NCs are more active against S. aureus (Gram-positive) than E. coli (Gram-negative) and their antibacterial activity increases with concentration increase. This result may reflect the fact that Gram-positive bacteria are less susceptible to antibacterial drugs than Gram-negative ones as a result of their difference in cell wall structures.⁵³ The activity might be either from direct contact with cells or from subordinate products corroding bacteria. Furthermore, a synergistic effect between CuO–Fe₂O₃–MgO nanomaterials and (i) metal ions, (ii) reactive oxygen species, and (iii) NPs shape could be one possible mechanism. Hence, a reasonable antibacterial action of these ions is their ability to produce dense metal ions such as Mg⁺², Cu⁺², and Fe⁺², being able to interact with bacteria cell membranes and, thus introducing them as potential antibacterial agents. It has been shown that mutual interactions of positive Mg⁺², Cu⁺², and Fe⁺² ions with negative charge of the cell membrane may lead to penetration of positive ions through the membrane and responses with sulfhydryl groups in the membrane. As a result of this weakness, the cells of microbe cannot grow, leading to its death.

Table 3.

Antibacterial activity of CuO–Fe₂O₃–MgO nanocomposites at different concentrations.

Sample	Bacteria	Zone of inhibition (ZOI; diameter in mm) at various concentrations
		Concentration (mg/ml)			Azithromycin (control)
		100 mg/ml	200 mg/ml	400 mg/ml	Azithromycin (control)
G1	S. aureus	18	20	22	31
G1	E. coli	16	18	20	28
G1.5	S. aureus	17	19	22	31
G1.5	E. coli	14	13	16	28
G2	S. aureus	23	26	28	31
G2	E. coli	19	22	24	28

Figure 8.

Selected plate images of antibacterial tests of CuO–Fe₂O₃–MgO NCs for (from top to bottom) G1, G1.5, and G2 at concentrations of 100, 200, and 400 mg/ml (discs termed 1, 2, and 3, respectively; 4 and 5 discs are for azithromycin antibiotics (positive control) and distilled water (negative control)) against Staphylococcus aureus (left column images) and Escherichia coli (right column images). The histograms illustrate the zone of inhibition in mm.

The observed general trend in the antibacterial activity and the predicted particle size were to increase with glycine fuel concentration increase, that is G1 > G1.5 > G2, supporting the fact that the smaller the particles, the easier the interaction and thus penetration into inside the cell, which subsequently could cause the cell death.

A comparison of inhibition zones of the synthesized NCs with other NCs from literature^40,54–59 is summarized in Table 4. As can be seen, the prepared novel tri-phase metal oxide CuO–Fe₂O₃–MgO NCs are well positioned or even have superior activity than the tabulated multi-oxides–based materials. Interestingly, all reported lower activity against E. coli (Gram-negative bacteria) than S. aureus (Gram-positive bacteria). However, bioactivity of NCs could be a result of many factors including chemical composition, morphology, particle size, NCs concentration, and exposure time. Hence, three mechanisms were commonly act individually or simultaneously, those are the direct attachment with microorganism surface, the metal ions release and penetration into cell, and the formation of reactive oxygen species (ROS). As a result, the cell functionality may be interrupted or evenly lost leading to cell death.

Table 4.

A comparison of antibacterial analysis of CuO–Fe₂O₃–MgO NCs with other NCs.

Metal oxide nanocomposites	Inhibition zone (mm)
Metal oxide nanocomposites	S. aureus	E. coli	Ref
CdS–ZnO	22	14	48
NiO–CeO₂–ZnO	14	11	49
ZnO–V₂O₅–WO₃	18	—	33
CuO–CeO₂–ZnO	14	10	51
CdO–NiO–ZnO	—	16	50
CdO–ZnO–MgO	20	23	52
gC₃N₄–BiFeO₃–CuO₂	18	17	51
CuO–Fe₂O₃–MgO	28	24	Present work

Conclusion

The trimetallic oxide CuO–Fe₂O₃–MgO NCs were synthesized for the first time using the sol-gel technique and under different concentrations of amino acid glycine as a NPs–facilitating and shape–directing agent. Analysis indicates the decrease in particle size and increase in optical energy bandgap with glycine concentration increase. This NCs has a comparable antibacterial activity to its alike multi-phase oxides, more active against S. aureus than E. coli. Such introductory results making them one potential candidate for advanced applications, possibly to benefit catalytic, electronics and bactericidal fields. These findings could support the used approach for synthesis of multi-phase oxides NPs where specific particle sizes are required, by controlling, beside other conditions, the glycine concentration.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors are grateful to the Deanship of Scientific Research, King Saud University, for the support through the Vice Deanship of Scientific Research Chairs, Engineer Abdullah Bugshan Research Chair for Dental and Oral Rehabilitation.

ORCID iD

Abdel-Basit Al-Odayni

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Synthesis of glycine-mediated CuO–Fe 2 O 3 –MgO nanocomposites: Structural,optical,and antibacterial properties

Abstract

Keywords

Introduction

Materials and methods

Materials

Preparation glycine-mediated tri-phase CuO–Fe2O3–MgO nanocomposite

Characterization techniques

Antibacterial test

Results and discussion

Structural properties

FTIR analysis

XRD analysis

SEM analysis

Optical properties

Electronic spectra

Extinction coefficient, refractive index, and optical conductivity

Optical energy gap (E g )

Antibacterial activity

Conclusion

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

References

Preparation glycine-mediated tri-phase CuO–Fe₂O₃–MgO nanocomposite

Optical energy gap (E_g)