rus
Issue #2/2024
A.B.Golik, A.A.Nagdalian, A.V.Blinov, R.Sh.Zakaeva, P.S.Leontev, M.A.Taravanov, Z.A.Rekhman, A.S.Askerova
STUDY OF THE PROCESS OF FORMATION OF COPPER OXIDE NANOPARTICLES STABILIZED BY GLYCERYL COCOATE
STUDY OF THE PROCESS OF FORMATION OF COPPER OXIDE NANOPARTICLES STABILIZED BY GLYCERYL COCOATE
In this work, samples of nanoscale copper oxide stabilised with glyceryl cocoate were prepared by chemical precipitation in aqueous medium. Scanning electron microscopy microstructure studies showed that the copper oxide sample is represented by irregularly shaped agglomerates of size from 1 to 30 μm, which consist of nanoparticles diameters from 5 to 50 nm. Phase composition studies showed that the obtained sample is copper (II) oxide with monoclinic-beta crystal lattice, in this case the space group corresponds to C2/c. As a result of computer quantum-chemical modelling of interaction between glyceryl cocoate and copper oxide, it was found that the presented compound is energetically favourable (∆E = 1714.492 kcal/mol) and the interaction occurs via the carboxylate anion. This compound possesses a chemical rigidity value η ≥ 0.050 eV, indicating its stability. Interaction between glyceryl cocoate and copper oxide was found to occur through the carboxyl group by IR spectroscopy. During optimisation of the synthesis technique, it was found that the optimal parameters for obtaining CuO nanoparticles with an average hydrodynamic radius of less than 200 nm are temperatures in the rage of 95 to 100 °C, mass of copper acetate from 3 to 4 grams and concentration of stabiliser PEG-7 from 1–3%.
Теги: chemical deposition copper oxide ir-spectroscopy nanoparticles stabiliser ик-спектроскопия наночастицы оксид меди стабилизатор химическое осаждение
INTRODUCTION
Nowadays, microcrystalline copper (II) oxide (CuO) is widely used in various industries [1, 2]. For example, in ceramic industry, copper oxide is used as a pigment to produce blue, red and green, and sometimes grey, pink or black glazes [3]. Electrodes made of copper oxide were part of the early type of batteries known as Edison – Lalande cells. Copper oxide was also used in lithium-type batteries [4–6]. Copper oxide is used in pyrotechnic industry as a dye of moderate blue colour in blue flame compositions, in welding with copper alloys, as a food additive in animal feeds, in laboratories to detect reducing properties of substances and to produce other copper salts [7–9].
Copper oxide nanoparticles with antimicrobial, semiconducting, photocatalytic, magnetic and optical properties are of great interest [10]. In addition, nanoscale CuO has high surface activity and thermal stability [11]. Copper oxide nanoparticles have found their application in various fields of science and technology [12, 13]. Nanoscale CuO is used in transistors, diodes, liquid crystal displays, batteries and solar cells [14]. In addition, in energy industry, copper oxide nanoparticles are applied as a catalyst in processes related to hydrogen production. In medicine, CuO nanoparticles are used to make antibacterial coatings used in prostheses and implants to prevent infections and tissue contamination [15].
To improve the above mentioned properties, copper oxide nanoparticles are stabilised with non-ionogenic surfactants (surfactants). Non-ionogenic surfactants are chemical compounds with surface-active properties that do not dissociate into ions in aqueous solutions [16]. Nonionogenic surfactants include such substances as neonol, nonoxynol-9, pluronics, polysorbates (Tween-20, Tween-80 and others), synthanol (OS-20, Brij 35, Ukanil), Triton X-100 and so on.
Non-ionogenic surfactants have the widest application as good detergents [17]. They are also used in various industrial applications. For example, in textile industry, non-ionogenic surfactants are used as additives to prevent static electrification of synthetic fibres, and non-ionogenic surfactants with 20–22 ethylene oxide groups are used to ensure even dyeing of fabrics. In the petroleum industry, they are used as hydrophobisers of reservoir rocks and as demulsifiers of oil-water emulsions. In addition, non-ionogenic surfactants with several oxyethyl groups are used as effective agents for preparing emulsions of mineral oils [18, 19].
For example, polysorbates are used in medicinal preparations for oral and topical use. They are also often used in the cosmetic industry as emulsifiers and solubilisers, for dissolving essential oils in water-based products. In addition, the use of polysorbates is relevant in biotechnology, food industry and other areas [20].
Thus, copper oxide nanoparticles stabilised by non-ionogenic surfactants are a unique material used in many fields of industry and medicine. That is why obtaining stabilised CuO nanoparticles is one of the key tasks of modern science.
In view of actual application of this material, the aim of this work was the synthesis of copper (II) oxide nanoparticles and study of the stabilisation process of CuO nanoparticles by non-ionogenic surfactants.
RESEARCH METHODS
CuO nanoparticle (NP) samples were obtained by chemical deposition of water-soluble divalent copper salt. Alkali solution (NaOH) was used as a precipitant and glyceryl cocoate (PEG-7) was used as a stabiliser.
In the first step, an aqueous solution consisting of CH₃COOCOCu and glyceryl cocoate was prepared, then the obtained mixture was heated under constant stirring and NaOH solution was added. The resulting sol was kept for 10 minutes under constant stirring. Then copper oxide powder was obtained from the synthesised sol by centrifugation and drying in a desiccator.
To study phase composition and microstructure, the samples were studied by X-ray phase analysis on X-ray diffractometer “PANalytical Empyrean”, and scanning electron microscopy on MIRA-LMH of Tescan company.
Quantum-chemical modelling of interaction of copper oxide with PEG-7 was carried out in QChem software using the IQmol molecular editor [21, 22], using the following construction parameters: calculation – Energy, method – HF, basis: 6-31G, convergence – 5, force field - Ghemical.
The samples were also studied by infrared spectroscopy on a Fourier 1201 infrared spectrometer.
The obtained samples of nanosized copper (II) oxide were studied by the dynamic light scattering method on the Photocor-Complex unit. Statistica 10.0 software packages was used to process the experimental data and to automate calculations for detection of gross errors, estimation of dispersions, determination of the coefficients adequacy and derived equations.
Optimisation of methodology for the synthesis of nanosized copper (II) oxide was carried out. Preliminary experiments allowed us to identify factors that have a significant influence on the process of synthesis of nanosized copper (II) oxide:
mass concentration of PEG-7 relative to the mass of the obtained oxide, %;
mass of СН₃СООCu, grams;
temperature, T.
The output parameter is R – average hydrodynamic radius of nanoparticles, nm.
An orthogonal plan of 9 experiments in threefold repetition was applied to study the three factors at their variation at three levels [24]. The levels of variation of the main parameters are shown in Table 1.
To study mutual influence of all factors with a minimum number of experiments, we used the planning matrix obtained by the method of Greek-Latin squares and presented in Table 2.
RESULTS
To study the process of preparing of nanosized copper (II) oxide we study influence of technological parameters on the average hydrodynamic radius of particles by constructing ternary dependences. Fig.1 shows the ternary surface of dependence of the average hydrodynamic radius of copper (II) oxide nanoparticles on the variable parameters.
At the first stage, samples of nanosized copper oxide were made and their microstructure was studied using a scanning electron microscope, and these measurement results are presented in Fig.2.
At the next stage we studied the phase composition of obtained samples, the results are presented in Fig.3.
The next step was quantum chemical modelling of the interaction of CuO with PEG-7 and the results are presented in Table 3 and Fig.4.
To confirm the data obtained by quantum-chemical modelling, the samples were studied by IR spectroscopy. The results are presented in Fig.5.
DISCUSSION
When analysing the obtained SEM micrographs, it is revealed that the copper oxide sample is an irregularly shaped aggregates of size from 1 to 30 μm, which consist of nanoparticles with a diameter of 5 to 50 nm.
According to the results of analysis of the diffractogram obtained during X-ray phase analysis it can be established that the obtained sample is copper (II) oxide with monoclinic-beta crystal lattice, in this case the space group corresponds to C2/c. The diffractogram shows low intensity of the peaks, as well as their broadening, which indicates that the particles of the obtained copper (II) oxide are in the nanocrystalline state.
From the results of calculation of the model of interaction of copper oxide with PEG-7, it can be concluded that the chemical rigidity of PEG-7 molecule decreases when interacting with the copper ion, which indicates some decrease in the activation energy, and hence the stability of the system. It is also found that the presented compound is energetically favourable (∆E = 1714.492 kcal/mol), the interaction occurs via carboxylate anion. This compound has a chemical rigidity value η ≥ 0.050 eV, which indicates its stability.
Analysis of IR spectra of glyceryl cocoate showed presence of bond deformation vibrations bands: at 593 and 673 cm–1 – characteristic of the O-H-group, as well as at 815, 952, 1155 cm–1, characteristic of the CH3-group and at 1343 cm–1, characteristic of the O-H-group. Presence of strain vibrations band at 1414 cm–1 corresponds to vibrations for the H-C-H group and also presence of a band at 1563 cm–1 indicates the C-C group. In addition, valence vibration bands at 2887, 2923, 2970, 3466 cm–1 are present which are characteristic of C-H group. Also at 1754 cm–1 the strain vibrations band characteristic of RCOO-group was detected.
The analysis of IR spectra of copper oxide nanoparticles stabilised with glyceryl cocoate showed presence of bond deformation vibrations bands: at 593 and 673 cm–1 – characteristic of the O-H-group, as well as at 815, 952, 1155 cm–1, characteristic of the CH3-group and at 1343 cm–1, characteristic of the O-H-group. Presence of the strain vibrations band at 1414 cm–1 corresponds to vibrations for the H-C-H group and also the band at 1563 cm–1 indicates the C-C group. In addition, valence vibrational bands at 2887, 2923, 2970, 3466 cm–1 are present which are characteristic of C-H group.
Thus, due to presence in the sample of glyceryl cocoate at 1754 cm–1 of the deformation vibrations band characteristic of the RCOO-group and a drop in intensity of this band in the sample of nanosized copper oxide stabilised by glyceryl cocoate, it can be concluded that stabilisation occurs through the carboxyl group. The results obtained from the analysis of IR spectra do not contradict the data obtained from quantum chemical modelling.
The analysis of ternary surface and surface cross-sectional isolines showed that the copper acetate weight and PEG-7 stabiliser concentration have a significant effect on the average hydrodynamic radius of CuO nanoparticles. Thus, analysing the ternary and cross-sectional isolines surfaces, we can conclude that for the synthesis of CuO nanoparticles with an average hydrodynamic radius of less than 200 nm, the optimal synthesis parameters are temperature in the range of 95 to 100 °C, the mass of copper acetate from 3 to 4 g and the concentration of PEG-7 stabiliser from 1 to 3%.
CONCLUSIONS
Thus, the analysis of the obtained SEM micrographs revealed that the sample of copper oxide is an irregularly shaped aggregates of size from 1 to 30 μm, which consist of nanoparticles with a diameter of 5 to 50 nm. Examination of the samples by X-ray diffraction showed that the obtained nanoscale copper oxide has an amorphous structure. When analysing the data obtained by modelling the interaction between glyceryl cocoate molecule and copper oxide, it was found that the presented compound is energetically advantageous (∆E = 1714.492 kcal/mol). The interaction takes place through carboxylate anion. This compound possesses a chemical rigidity value η ≥ 0.050 eV, which indicates its stability. By comparing two IR spectra, it was found that interaction between glyceryl cocoate and copper oxide occurs through the carboxyl group. Analysing the data obtained in the course of optimisation of methodology for the synthesis of copper oxide nanoparticles, we can conclude that for the synthesis of CuO nanoparticles with an average hydrodynamic radius of less than 200 nm, the optimal synthesis parameters are temperature in the range of 95 to 100 °C, the mass of copper acetate from 3 to 4 g and of stabiliser concentration PEG-7 from 1–3%.
ACKNOWLEDGMENTS
This work was supported by the grant of the Russian Science Foundation No. 23-76-10046, https://rscf.ru/en/project/23-76-10046/
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Nowadays, microcrystalline copper (II) oxide (CuO) is widely used in various industries [1, 2]. For example, in ceramic industry, copper oxide is used as a pigment to produce blue, red and green, and sometimes grey, pink or black glazes [3]. Electrodes made of copper oxide were part of the early type of batteries known as Edison – Lalande cells. Copper oxide was also used in lithium-type batteries [4–6]. Copper oxide is used in pyrotechnic industry as a dye of moderate blue colour in blue flame compositions, in welding with copper alloys, as a food additive in animal feeds, in laboratories to detect reducing properties of substances and to produce other copper salts [7–9].
Copper oxide nanoparticles with antimicrobial, semiconducting, photocatalytic, magnetic and optical properties are of great interest [10]. In addition, nanoscale CuO has high surface activity and thermal stability [11]. Copper oxide nanoparticles have found their application in various fields of science and technology [12, 13]. Nanoscale CuO is used in transistors, diodes, liquid crystal displays, batteries and solar cells [14]. In addition, in energy industry, copper oxide nanoparticles are applied as a catalyst in processes related to hydrogen production. In medicine, CuO nanoparticles are used to make antibacterial coatings used in prostheses and implants to prevent infections and tissue contamination [15].
To improve the above mentioned properties, copper oxide nanoparticles are stabilised with non-ionogenic surfactants (surfactants). Non-ionogenic surfactants are chemical compounds with surface-active properties that do not dissociate into ions in aqueous solutions [16]. Nonionogenic surfactants include such substances as neonol, nonoxynol-9, pluronics, polysorbates (Tween-20, Tween-80 and others), synthanol (OS-20, Brij 35, Ukanil), Triton X-100 and so on.
Non-ionogenic surfactants have the widest application as good detergents [17]. They are also used in various industrial applications. For example, in textile industry, non-ionogenic surfactants are used as additives to prevent static electrification of synthetic fibres, and non-ionogenic surfactants with 20–22 ethylene oxide groups are used to ensure even dyeing of fabrics. In the petroleum industry, they are used as hydrophobisers of reservoir rocks and as demulsifiers of oil-water emulsions. In addition, non-ionogenic surfactants with several oxyethyl groups are used as effective agents for preparing emulsions of mineral oils [18, 19].
For example, polysorbates are used in medicinal preparations for oral and topical use. They are also often used in the cosmetic industry as emulsifiers and solubilisers, for dissolving essential oils in water-based products. In addition, the use of polysorbates is relevant in biotechnology, food industry and other areas [20].
Thus, copper oxide nanoparticles stabilised by non-ionogenic surfactants are a unique material used in many fields of industry and medicine. That is why obtaining stabilised CuO nanoparticles is one of the key tasks of modern science.
In view of actual application of this material, the aim of this work was the synthesis of copper (II) oxide nanoparticles and study of the stabilisation process of CuO nanoparticles by non-ionogenic surfactants.
RESEARCH METHODS
CuO nanoparticle (NP) samples were obtained by chemical deposition of water-soluble divalent copper salt. Alkali solution (NaOH) was used as a precipitant and glyceryl cocoate (PEG-7) was used as a stabiliser.
In the first step, an aqueous solution consisting of CH₃COOCOCu and glyceryl cocoate was prepared, then the obtained mixture was heated under constant stirring and NaOH solution was added. The resulting sol was kept for 10 minutes under constant stirring. Then copper oxide powder was obtained from the synthesised sol by centrifugation and drying in a desiccator.
To study phase composition and microstructure, the samples were studied by X-ray phase analysis on X-ray diffractometer “PANalytical Empyrean”, and scanning electron microscopy on MIRA-LMH of Tescan company.
Quantum-chemical modelling of interaction of copper oxide with PEG-7 was carried out in QChem software using the IQmol molecular editor [21, 22], using the following construction parameters: calculation – Energy, method – HF, basis: 6-31G, convergence – 5, force field - Ghemical.
The samples were also studied by infrared spectroscopy on a Fourier 1201 infrared spectrometer.
The obtained samples of nanosized copper (II) oxide were studied by the dynamic light scattering method on the Photocor-Complex unit. Statistica 10.0 software packages was used to process the experimental data and to automate calculations for detection of gross errors, estimation of dispersions, determination of the coefficients adequacy and derived equations.
Optimisation of methodology for the synthesis of nanosized copper (II) oxide was carried out. Preliminary experiments allowed us to identify factors that have a significant influence on the process of synthesis of nanosized copper (II) oxide:
mass concentration of PEG-7 relative to the mass of the obtained oxide, %;
mass of СН₃СООCu, grams;
temperature, T.
The output parameter is R – average hydrodynamic radius of nanoparticles, nm.
An orthogonal plan of 9 experiments in threefold repetition was applied to study the three factors at their variation at three levels [24]. The levels of variation of the main parameters are shown in Table 1.
To study mutual influence of all factors with a minimum number of experiments, we used the planning matrix obtained by the method of Greek-Latin squares and presented in Table 2.
RESULTS
To study the process of preparing of nanosized copper (II) oxide we study influence of technological parameters on the average hydrodynamic radius of particles by constructing ternary dependences. Fig.1 shows the ternary surface of dependence of the average hydrodynamic radius of copper (II) oxide nanoparticles on the variable parameters.
At the first stage, samples of nanosized copper oxide were made and their microstructure was studied using a scanning electron microscope, and these measurement results are presented in Fig.2.
At the next stage we studied the phase composition of obtained samples, the results are presented in Fig.3.
The next step was quantum chemical modelling of the interaction of CuO with PEG-7 and the results are presented in Table 3 and Fig.4.
To confirm the data obtained by quantum-chemical modelling, the samples were studied by IR spectroscopy. The results are presented in Fig.5.
DISCUSSION
When analysing the obtained SEM micrographs, it is revealed that the copper oxide sample is an irregularly shaped aggregates of size from 1 to 30 μm, which consist of nanoparticles with a diameter of 5 to 50 nm.
According to the results of analysis of the diffractogram obtained during X-ray phase analysis it can be established that the obtained sample is copper (II) oxide with monoclinic-beta crystal lattice, in this case the space group corresponds to C2/c. The diffractogram shows low intensity of the peaks, as well as their broadening, which indicates that the particles of the obtained copper (II) oxide are in the nanocrystalline state.
From the results of calculation of the model of interaction of copper oxide with PEG-7, it can be concluded that the chemical rigidity of PEG-7 molecule decreases when interacting with the copper ion, which indicates some decrease in the activation energy, and hence the stability of the system. It is also found that the presented compound is energetically favourable (∆E = 1714.492 kcal/mol), the interaction occurs via carboxylate anion. This compound has a chemical rigidity value η ≥ 0.050 eV, which indicates its stability.
Analysis of IR spectra of glyceryl cocoate showed presence of bond deformation vibrations bands: at 593 and 673 cm–1 – characteristic of the O-H-group, as well as at 815, 952, 1155 cm–1, characteristic of the CH3-group and at 1343 cm–1, characteristic of the O-H-group. Presence of strain vibrations band at 1414 cm–1 corresponds to vibrations for the H-C-H group and also presence of a band at 1563 cm–1 indicates the C-C group. In addition, valence vibration bands at 2887, 2923, 2970, 3466 cm–1 are present which are characteristic of C-H group. Also at 1754 cm–1 the strain vibrations band characteristic of RCOO-group was detected.
The analysis of IR spectra of copper oxide nanoparticles stabilised with glyceryl cocoate showed presence of bond deformation vibrations bands: at 593 and 673 cm–1 – characteristic of the O-H-group, as well as at 815, 952, 1155 cm–1, characteristic of the CH3-group and at 1343 cm–1, characteristic of the O-H-group. Presence of the strain vibrations band at 1414 cm–1 corresponds to vibrations for the H-C-H group and also the band at 1563 cm–1 indicates the C-C group. In addition, valence vibrational bands at 2887, 2923, 2970, 3466 cm–1 are present which are characteristic of C-H group.
Thus, due to presence in the sample of glyceryl cocoate at 1754 cm–1 of the deformation vibrations band characteristic of the RCOO-group and a drop in intensity of this band in the sample of nanosized copper oxide stabilised by glyceryl cocoate, it can be concluded that stabilisation occurs through the carboxyl group. The results obtained from the analysis of IR spectra do not contradict the data obtained from quantum chemical modelling.
The analysis of ternary surface and surface cross-sectional isolines showed that the copper acetate weight and PEG-7 stabiliser concentration have a significant effect on the average hydrodynamic radius of CuO nanoparticles. Thus, analysing the ternary and cross-sectional isolines surfaces, we can conclude that for the synthesis of CuO nanoparticles with an average hydrodynamic radius of less than 200 nm, the optimal synthesis parameters are temperature in the range of 95 to 100 °C, the mass of copper acetate from 3 to 4 g and the concentration of PEG-7 stabiliser from 1 to 3%.
CONCLUSIONS
Thus, the analysis of the obtained SEM micrographs revealed that the sample of copper oxide is an irregularly shaped aggregates of size from 1 to 30 μm, which consist of nanoparticles with a diameter of 5 to 50 nm. Examination of the samples by X-ray diffraction showed that the obtained nanoscale copper oxide has an amorphous structure. When analysing the data obtained by modelling the interaction between glyceryl cocoate molecule and copper oxide, it was found that the presented compound is energetically advantageous (∆E = 1714.492 kcal/mol). The interaction takes place through carboxylate anion. This compound possesses a chemical rigidity value η ≥ 0.050 eV, which indicates its stability. By comparing two IR spectra, it was found that interaction between glyceryl cocoate and copper oxide occurs through the carboxyl group. Analysing the data obtained in the course of optimisation of methodology for the synthesis of copper oxide nanoparticles, we can conclude that for the synthesis of CuO nanoparticles with an average hydrodynamic radius of less than 200 nm, the optimal synthesis parameters are temperature in the range of 95 to 100 °C, the mass of copper acetate from 3 to 4 g and of stabiliser concentration PEG-7 from 1–3%.
ACKNOWLEDGMENTS
This work was supported by the grant of the Russian Science Foundation No. 23-76-10046, https://rscf.ru/en/project/23-76-10046/
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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