Influence of Anionic Surfactant on Stability of Nanoparticles in Aqueous Solutions published by Ural Federal University eISSN 2411-1414 chimicatechnoacta.ru ARTICLE 2023, vol. 10(3), No. 202310302 DOI: 10.15826/chimtech.2023.10.3.02 1 of 8 Influence of anionic surfactant on stability of nanoparticles in aqueous solutions Dmitry O. Zelentsov a , Yuliya Yu. Petrova a * , Alexander V. Korobkin a, Anastasia A. Ivanova b , Alexey N. Cheremisin b , Ivan I. Shanenkov c , Alexander Ya. Pak d , Yuliya G. Mateyshina e a: Institute of Natural and Technical Sciences, Surgut State University, Surgut 628408, Russia b: Skoltech Center for Petroleum Science and Engineering, Skoltech, Moscow 121205, Russia c: Institute of Environmental and Agricultural Biology, Tyumen State University, Tyumen 625003, Russia d: School of Energy and Power Engineering, Tomsk Polytechnic University, Tomsk 634050, Russia e: Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia * Corresponding author: petrova_juju@surgu.ru This paper belongs to the RKFM'23 Special Issue: https://chem.conf.nstu.ru/. Guest Editors: Prof. N. Uvarov and Prof. E. Aubakirov. Abstract Dispersion and aggregation of nanoparticles in aqueous solutions are im- portant factors for safe and effective application of nanoparticles, for in- stance, in the oil industry. As conventional oil reserves are depleted, it is necessary to advance chemical enhanced oil recovery (cEOR) techniques to develop unconventional oil reservoirs. Nanoparticles modified by sur- factants can be a promising reagent in cEOR. These nanomaterials can re- duce interfacial tension and change the wettability of reservoir rock, which leads to an increase in oil recovery. However, the application of na- noparticles is limited by their substantial aggregation in aqueous solu- tions. The purpose of this work is to select nanoparticles for obtaining sta- ble sols in water in the presence of an anionic surfactant and to optimize the conditions (pH) for further modifying the nanoparticles with the ani- onic surfactant. Sodium dodecyl sulfate (SDS) is used as an anionic surfac- tant. The aggregation of oxide and carbon nanoparticles in water and ani- onic surfactant solutions was studied by laser diffraction, dynamic and electrophoretic light scattering methods. Most of the studied nanoparticles in water form aggregates with bi-, three- and polymodal particle size distri- butions. TiO2 nanoparticles obtained by plasma dynamic synthesis form the most stable sols in anionic surfactant solutions. The range of 5–7 pH is de- fined as optimal for their modification with surfactants. The stability of car- bon nanoparticles in aqueous solutions increases significantly in the pres- ence of a surfactant. The obtained results form the basis for further research on the modification of marked nanoparticles in surfactant solutions. Keywords nanoparticles anionic surfactant titan oxide carbon nanoparticles aggregation Received: 09.07.23 Revised: 24.07.23 Accepted: 24.07.23 Available online: 27.07.23 Key findings ● TiO2 nanoparticles form the most stable sols in anionic surfactant solutions. ● 5–7 pH is optimal for modification of TiO2 with sodium dodecyl sulfate. ● Carbon nanoparticles are significantly more stable in anionic surfactant solutions. © 2023, the Authors. This article is published in open access under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction With the increased attention toward nanotechnology and its innovative use for different industries including, but not limited to, food, biomedical, electronics, materials, etc., the application of nanotechnology or nanoparticles in the oil and gas industry is a subject undergoing intensive study by major oil companies, which is reflected in the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0009-0007-6153-8380 https://orcid.org/0000-0003-3702-2249 https://orcid.org/0000-0003-2323-6297 https://orcid.org/0000-0002-3580-9120 https://orcid.org/0000-0001-7499-5846 https://orcid.org/0000-0001-8447-1309 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.02&domain=pdf&date_stamp=2023-07-27 https://journals.urfu.ru/index.php/chimtech/rt/suppFiles/6960/0 Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 2 of 8 DOI: 10.15826/chimtech.2023.10.3.02 huge amount of funds invested in the research and devel- opment of nanotechnology. Nanotechnology has been re- cently investigated extensively for different applications in the oil and gas industry, such as drilling fluids and en- hanced oil recovery, in addition to other applications in- cluding cementing and well stimulation [1]. As conventional oil reserves are gradually depleted, oil producers are increasingly seeking to develop oil reservoirs that have already been discovered. Developing oil reser- voirs characterized by high temperatures and ultra-low permeability is becoming a major challenge. This can be handled by using chemical enhanced oil recovery (cEOR) techniques. They receive a great deal of attention because they allow controlling the properties at the oil-fluid and oil- rock interfaces. Nanotechnology applications in cEOR are studied by researchers around the world [2–5]. First of all, nanoparticles (NPts) can adsorb on reservoir rock and change its wettability from oil-wet to water-wet [6–7]. Also, nanoparticles can adsorb at the oil-fluid interface and reduce the interfacial tension, which also leads to an in- crease in oil displacement [8]. A limitation in the application of NPts is their low sta- bility in liquid systems and tendency to aggregation [9]. At high mineralization and high temperatures, aggregation of nanoparticles may increase even more. Flooding a reservoir with fluids containing large aggregates of NPts may lead to clogging of small reservoir pores, which will have a nega- tive effect on the overall oil recovery [10]. To prevent excessive aggregation of NPts, they are modified with surfactants. The modification is carried out by two methods: in-situ (physical adsorption) and ex-situ (chemical grafting) [11]. The obtained nano-surfactant composites acquire greater surface activity, and their sta- bility in aqueous systems is improved [12]. Fluids with modified NPts were shown to displace oil more effectively [13]. Adsorbed surfactant molecules can prevent excessive aggregation of NPts, but the opposite effect is also possi- ble [14]. It was noted that dispersions with smaller aggre- gates of nanoparticles are more effective in reducing the interfacial tension [13, 15], and the efficiency in the wet- tability alteration of modified NPts is higher than that of unmodified ones or surfactant solutions without NPts [16– 17]. In the work [18] it was shown that modified SiO2 NPts reduced the adsorption of surfactants on the rock. Modifi- cation conditions, such as the type of nanoparticles and a surfactant, the ratio of their concentrations, pH and min- eralization, can significantly affect the efficiency of mod- ified nanoparticles in oil displacement [19–23]. In this work, we selected nanoparticles that form the most stable dispersions or sols in water and anionic surfac- tant solutions. Also, for the selected nanoparticles we stud- ied the effect of pH on their aggregation in surfactant solu- tion to choose the optimal conditions for further modifying NPts with the surfactant. 2. Materials and Methods 2.1. Materials The following silica and titanium oxide NPts (Sigma-Al- drich) were used in this work: SiO2 and TiO2-SA; β-Bi2O3 NPts obtained by thermal decomposition of BiC2H4(OH) [24]; graphite-like carbon nanoparticles (C-NPts) obtained by plasma treatment of asphaltenes [25]; and NPts obtained by plasma dynamic synthesis [26]: titanium oxides (TiO2 – particles containing magnelli-phase with a wide size distri- bution from 1 nm to 50 μm, TiO2-BK – fine particles up to 1 μm in size), aluminum oxide and a mixture of iron oxides. Sodium dodecyl sulfate (SDS, PanReac) was used as an ani- onic surfactant. Sodium hydroxide (LenReactiv, >99%), phosphoric acid (Component-Reaktiv, >99%), and phos- phate buffer solutions prepared from disodium hydrogen phosphate (Merck, >99.9%) and sodium dihydrogen phos- phate 2-hydrate (Merck, >99.9%) were used to adjust pH. 2.2. Nanoparticle characterization The physical–chemical characterization was done using the X-ray fluorescence (vacuum 8–12 Pa, energy-dispersive an- alyzer EDX-8000, Shimadzu), FT-IR (ATR and transmission mode, Spectrum 100 Series, Perkin Elmer) and TGA/DSC analysis. The TGA/DSC analysis of the nanoparticles was performed with a Mettler Toledo TGA/DSC 3+ Star System, at a heating rate of 20 ℃/min, under nitrogen atmosphere with a flow rate of 50 mL/min. 2.3. Size distribution of nanoparticle aggregates by laser diffraction The particle size was evaluated with a SALD-2300 (Shi- madzu) analyzer for selection of oxide nanoparticles and study of surfactant influence on carbon nanoparticle aggre- gation. The oxide nanoparticles (~2 mg) were dispersed in 10 ml of distilled water. Before each measurement, the nanofluid sample was sonicated using a probe type soni- cator at a frequency of 35 kHz for 10 min. 0.5 ml of the dis- persion was taken and placed in a SALD-2300 (Shimadzu) analyzer cuvette filled with 9.5 ml of distilled water or 5, 10, or 50 mmol/L SDS solution, a stirrer was turned on, and par- ticle size measurements were performed for 1 h. To study the size distribution of C-NPts aggregates, 0.01% dispersions were prepared in water or 5 and 50 mmol/L SDS solutions. 2.4. Zeta-potential and size distribution of NPts by dynamic light scattering Zeta-potential (ζ) and size distribution of NPts in the nanofluid were measured using a particle size analyser (Litesizer 500, Anton Paar) which works on the principle of dynamic light scattering (DLS) to study the influence of pH on the aggregation of β-Bi2O3 and TiO2 NPts in 5 mmol/L SDS solutions. The solutions were prepared using a phos- phate buffer for pH 4.5–9.0, 3.3∙10–4–3.3 mol/L H3PO4 for https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 3 of 8 DOI: 10.15826/chimtech.2023.10.3.02 pH<4.0, and 0.25–25 mmol/L NaOH for pH>9.0. Thus, 0.025% dispersion of NPts was mixed with a buffer solu- tion (H3PO4 or NaOH) and 25 mmol/L SDS in a volume ratio of 2:2:1. The mixture was stirred, and the DLS measure- ments were performed. 2.5. Interfacial tension (IFT) measurements IFT measurements between n-hexane and different aqueous solutions of nanopaticles were conducted using the spin- ning drop method (SDT, Kruss, Germany) as it is more con- venient and accurate for measuring IFT below 20 mN∙m−1 [27]. Here, a drop of liquid with lower density (n-hexane) was placed inside the denser fluid (surfactant or surfac- tant–nanoparticle solutions) in a horizontal tube. Then, the tube was rotated, and the drop deformed into an elongated shape. The samples were assumed to be equilibrated when the measured IFT values remained unchanged (2%) for 30 min [28]. At the equilibrium point, the balance between surface tension and centrifugal forces defined the shape of the droplet. At a high angular velocity ω (max.15,000 rpm), the droplet shape becomes very close to a cylinder. In this case, the IFT values were calculated using the Vonnegut ex- pression (Equation 1). 𝜎 = ∆𝜌𝜔2𝑅3 4 , (1) where Δρ is the density difference between light and heavy phases (n-hexane and surfactant–nanoparticles formula- tions, measured with an areometer), and R is the shape ra- dius. To avoid the influence of impurities on the results, be- fore and after each experiment, the tube was cleaned with acetone and water and then dried with air. 3. Results and Discussion 3.1. Nanoparticle characterization TiO2 and carbon NPts were measured by X-ray fluorescence (XRF), and the results are listed in Table 1. TiO2 NPts obtained by plasma dynamic synthesis contain impurities of iron, silicon, aluminum, calcium, etc., and car- bon NPts obtained by plasma treatment of asphaltenes con- tain impurities of sulfur. The FTIR spectrum of TiO2 NPts recorded in attenuated total reflection (ATR) mode, shown in Figure 1a, provided additional information about the TiO2 structure. It can be observed that the strong band in the range of 480 to 660 cm–1 was assigned to Ti–O stretching bands [29]. FTIR ab- sorption spectra of TiO2 NPts contain the band (wide peak or shoulder) at approximately around 3500 cm–1 (stretch- ing) which stipulates the presence of hydroxyl groups. The 1635 cm–1 absorption band may be related to hydroxyl (bending) representing the water as moisture in the sam- ple. The transmission IR spectra of C-NPts samples synthe- sized in plasma are presented in Figure 1b. The band at 1600 cm–1 is due to C=C stretching of the aromatic ring. The wide band at 3300–3650 cm–1 can be observed in the spec- tra due to OH groups. The differential thermal analysis of TiO2 NPts obtained by plasma dynamic synthesis (Figure 2) showed that up to 600 °C, the studied sample was thermally stable (TGA). Upon further increase in temperature above 600 °C in an inert medium, an increase in the sample mass was ob- served (DTA, maxima at 650 and 850 °C), which can be explained by the formation of nitrides of iron and calcium impurities. At the same time, the wide exothermic peak observed at about 400–650 °C was attributed to the phase transformation from anatase to rutile (DSC). 3.2. Selection of nanoparticles The next stage of our work was the selection of nanoparti- cles that form stable sols in SDS solutions. At this stage, we studied the aggregation of oxide nanoparticles by laser dif- fraction. SiO2 NPts formed large aggregates both in water and in SDS solutions (Figure S1). Thus, the modal size of SiO2 ag- gregates in water in 30 min was ~100 μm. Addition of SiO2 NPts in SDS solutions led to the formation of smaller aggre- gates (60~70 μm), which are still large for use in low-per- meability reservoirs. Smaller particle sizes were observed for TiO2-SA NPts (Figure S2). In water, the nanoparticles mainly form an ag- gregate fraction with sizes of ~32 μm in 30 min (Figure S2, a). In 10 and 50 mmol/L surfactant solutions TiO2-SA ag- gregation increases, forming aggregates ~127 and ~71 μm (Figure S2, c and d), respectively. And only 5 mmol/L SDS solution has a stabilizing effect, and the bulk of the aggre- gates form a fraction with a size of ~4 μm (Figure S2, b). This phenomenon can be explained by the fact that in 5 mmol/L solution the surfactant is only partially adsorbed on the surface of NPts and thus prevents further aggrega- tion of the particles. In 10 mmol/L solution, SDS (or its mi- celles) is completely adsorbed, or close to it, on the surface of NPts, forming a monolayer of surfactant molecules. This leads to a sharp increase in the hydrophobicity of the NPts, which, in turn, leads to an increase in aggregation. And in 50 mmol/L solution, SDS micelles continue to adsorb, form- ing a bilayer of surfactant molecules. The surface of NPts becomes more hydrophilic, and the size of the aggregates decreases. The following is a discussion of nanoparticles of iron, aluminum and titanium oxides obtained by the plasma dy- namic synthesis. It should be understood that these nano- particles are not homogeneous and are a mixture of differ- ent oxides. Thus, Fe2O3 includes a mixture of magnetite, hematite and ε-Fe2O3. Al2O3 includes γ-Al2O3 and spinel phases. TiO2 consists not only of rutile and anatase, but also of magnelli phases – non-stoichiometric titanium oxides. The heterogeneous composition can affect the obtained re- sults of particle size distributions. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 4 of 8 DOI: 10.15826/chimtech.2023.10.3.02 Table 1 The results of XRF analysis of TiO2 and carbon NPts. Figure 1 FTIR spectra of TiO2 NPts (a) and C-NPts (b): ATR (a), transmission mode (KBr pellet) (b). Figure 2 TGA (black), DSC (red) and DTA (blue) curves of TiO2 NPts (N2, 20 °C/min). Thus, Fe2O3 NPts in water, 5 and 50 mmol/L SDS solu- tions have low stability (Figure S3). This affects the non- equilibrium particle size distributions and sedimentation in 30 min, which prevents further observations. At the same time, in 10 mmol/L SDS solution (Figure S3, c), the disper- sions had a stable bimodal size distribution with modal di- ameters of 0.16 and 2.29 μm. Al2O3 NPts in both water and SDS solutions form aggre- gates with similar wide polymodal size distributions rang- ing from 20 nm to 160 μm (Figure S4). This suggests a weak or absent interaction between the NPts and the sur- factants. In all cases, Al2O3 NPts as well as Fe2O3 NPts showed low stability and precipitated in 30 min of meas- urements. The system of TiO2 particles in water was variable and tended to equilibrium throughout the entire measurement (Figure 3). In one hour, two fractions of particles with modal diameters of 0.4 and 24.9 μm were formed. The IFT measurements showed (Table 2) that TiO2 NPts effectively reduce the interfacial tension at the n-hexane-water inter- face by two times. However, in SDS solutions, the stabiliza- tion of NPts was observed during the entire hour of meas- urements. Practically monomodal size distributions with a modal diameter of ~0.4 μm are formed. With increasing SDS concentration, the fraction of aggregates with sizes of 1~10 μm slightly increases, which is probably also related to some increase in hydrophobicity of NPts due to higher adsorption of surfactant. β-Bi2O3 NPts in water form large aggregates ~90 µm (Figure S5). However, in SDS solutions as well as for TiO2 the stabilization of NPts occurs. The aggregates are formed mainly with bimodal size distributions with fractions of ~0.18 and ~6.94 μm. The aggregation of nanoparticles depends on both their type and method of synthesis. Different synthesis methods produce nanoparticles not only with different dispersions, but also with different surface properties. For example, the number of hydroxyl –OH groups on the particle surface may differ, which can have a critical impact on the adsorp- tion of surfactants on NPts. Apparently, TiO2 and β-Bi2O3 particles have a higher affinity for SDS than other parti- cles. Also, these nanoparticles simultaneously showed small aggregates (up to 0.18 μm) in SDS solutions and high stability. Therefore, TiO2 and β-Bi2O3 nanoparticles were selected for further studies on the effect of pH on their aggregation. 3.3. Influence of surfactant on carbon nanoparticle aggregation Carbon nanoparticles are of great interest because they are significantly more hydrophobic than oxide nanoparticles. C-NPts are poorly wetted by water, which makes it difficult to disperse them. The obtained values of interfacial tension in the aqueous dispersion of C-NPts (Table 2) confirm their hydrophobicity. In surfactant solutions, the particles dis- perse much better, which was proved experimentally (Fig- ure 4). Size distributions of NPts in all cases are polymodal with sizes from 0.18 to ~100 μm. Sample Element, wt.% Ti O Fe Si P Ca Al Hf C S Other TiO2 77.7 21.2 0.4 0.2 0.1 0.1 0.1 0.1 – – <0.1 a C-NPs – – – – 99.6 0.3 <0.1b a – Cr, Cu b – Ca, Si, V, Al, Fe, P, Ti, Ni, Cu, K https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 5 of 8 DOI: 10.15826/chimtech.2023.10.3.02 Table 2 Interfacial tension (IFT) measurements (between n-hexane and water dispersion). Sample IFT, mN/m water 37.77±0.03 TiO2 19.31±0.03 C-NPts 38.78±0.05 Figure 3 Size distribution of TiO2 NPts aggregates: in water (a), in 5 mmol/L SDS (b); in 10 mmol/L SDS (c); in 50 mmol/L SDS (d) (q3 – volume percentage, D – particle diameter). Figure 4 Size distribution of C-NPts aggregates: in water (1), in 5 mmol/L SDS (2), in 50 mmol/L SDS (3) (q3 – volume percentage, D – particle diameter). However, in water the fraction with the modal diameter of 21.8 μm prevails, while in the SDS solutions the content of particles with sizes smaller than 12.0 μm significantly increases. The median particle size in water was 17.9 μm, and in 5 and 50 mmol/L SDS solutions – 5.6 and 6.1 μm, respectively. The surfactant solution expectedly stabilizes the C-NPts in the aqueous system. The modification of C- NPts with surfactant is promising because, unlike oxide NPts, surfactant is adsorbed by orienting tails to the parti- cle surface. 3.4. Influence of pH on nanoparticle aggregation Hydroxyl groups and their amount on the surface of nano- particles can affect the adsorption of ionogenic surfactants. Thus, hydroxyl groups are protonated in acidic medium, which should increase the adsorption of anionic surfac- tants, while in an alkaline medium, on the contrary, they dissociate, and the adsorption should decrease. Therefore, the pH of the system can have a significant influence on the adsorption of surfactants. A study of the influence of pH on the aggregation of TiO2 NPts showed that the size of the aggregates significantly depended on the pH (Figure 5a). The size (median D) of the aggregates of TiO2 NPts in the water dispersion (without a buffer solution and SDS) was 196 nm. In the SDS solution (without buffer), the aggregate size increases ~1.6 times, which, as mentioned earlier, can be attributed to an in- crease in the hydrophobicity of the NPts surface due to sur- factant adsorption. The smallest aggregates (165~177 nm) are formed in solutions with pH from 5.0 to 6.5. In an acidic medium, there is a sharp increase in TiO2 aggregates up to ~900 nm, which seems to be due to the protonation of hy- droxyl groups on the surface of NPts and a significant in- crease in surfactant aggregation. At pH>7.0, the aggregate size also increases (up to 650 nm). In this case, in contrast with acidic media, this may be due, to an increase in the negative charge of SDS, which leads to an increase in its adsorption on the surface of TiO2 NPts in an alkaline me- dium. Thus, the pH range of 5.0–6.5 is optimal for obtaining stable TiO2 nano-sols. For TiO2-BK NPts, it can be noted that the aggregate size decreases to 850 nm in the 5 mmol/L SDS (without buffer) compared to 1000 nm in the aqueous dispersion (Figure 5b). In an acidic medium (pH<2), there is also a sharp en- largement of the aggregates up to 1360 nm. At pH>2, the size of the aggregates is in most cases even smaller (up to 750 nm) than in the solution without the added buffer. However, the minimum size of the aggregates is still 4.6 times larger than that for TiO2 NPTs. β-Bi2O3 NPts formed very large aggregates >1200 nm (Figure 5, c). Moreover, in water (without a buffer), the ag- gregates had the smallest size (1210 nm), but in the SDS solution, aggregates of 1690 nm were formed. It is also re- markable that in all pH ranges except pH 3 larger aggre- gates were formed compared to the aqueous dispersion of β-Bi2O3 NPts. The obtained results are in agreement with the zeta-poten- tial measurements (Figure 6). The zeta-potential of TiO2 NPts confirms the stability of the nano-sol in the region of 4.5 to 7.5 pH. When the particle size is changed (TiO2-BK), the sol stabi- lizes in an alkaline environment (10–11 pH) in SDS solution. β- Bi2O3 NPts form stable sols in SDS solution at pH 2 and 10–12, which seems to be related to their ionization in strongly acidic and strongly alkaline media. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 6 of 8 DOI: 10.15826/chimtech.2023.10.3.02 Figure 5 Dependence of the median diameter of nanoparticle aggregates on pH in 5 mmol/L SDS: TiO2 (a); TiO2-BK (b); β-Bi2O3 (c) (red line – in SDS; blue line – in water). Figure 6 Zeta-potential measurements of TiO2 (1, black), TiO2-BK (2, red) and β-Bi2O3 (3, blue) NPts in pH-controlled solutions: dot lines – in 5 mmol/L SDS; dash lines – in water. 4. Limitations The stability of nanoparticles in aqueous systems remains extremely critical. Even the smallest nanoparticles in water are prone to aggregation. Preventing or mitigating this phe- nomenon would be a big step in research. 5. Conclusions In this work, the aggregation of oxide nanoparticles in wa- ter and sodium dodecyl sulfate solutions was studied by la- ser diffraction. TiO2 and β-Bi2O3, obtained by plasma dy- namic synthesis and by thermal decomposition of BiC2H4(OH), respectively, stabilized in anionic surfactant solutions better than other nanoparticles and formed the smallest aggregates. Therefore, these nanoparticles were chosen for further studies. In the study of aggregation of carbon nanoparticles, it was shown that they are well stabilized in sodium dodecyl sulfate solutions. These nanoparticles are of great interest for further research due to their different nature from oxide nanoparticles and poor study in chemical enhanced oil re- covery. The influence of pH on the nanoparticle aggregation was studied by evaluating the aggregate sizes and zeta-potential measured using dynamic light scattering. It was shown that among all the studied nanoparticles TiO2 formed aggregates of the smallest size, and for them it was possible to deter- mine the optimal pH range at which the most stable sols are formed (5.0–7.0 pH). TiO2 and carbon nanoparticles are the most promising for further research, in particular, for their modification with sodium dodecyl sulfate and further application in chemical enhanced oil recovery. ● Supplementary materials This manuscript contains supplementary materials, which are available on the corresponding online page. ● Funding The work was carried out within the framework of the state task of the ISSCM SB RAS (project №121032500065-5) and also was supported by the Russian Science Foundation (grant №22-13-20016), https://www.rscf.ru/en. ● Acknowledgments The authors are grateful to Pavel Vadimovich Povalyaev (Tomsk Polytechnic University) for the provided carbon na- noparticles and Yurii Mikhailovich Yukhin (ISSCM SB RAN) for the provided β-Bi2O3 nanoparticles. ● Author contributions Conceptualization: Yu.Yu.P., D.O.Z. Formal Analysis: D.O.Z, A.V.K. Funding acquisition: Y.G.M., Yu.Yu.P. Investigation: D.O.Z, A.V.K. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 https://www.rscf.ru/en Chimica Techno Acta 2023, vol. 10(3), No. 202310302 ARTICLE 7 of 8 DOI: 10.15826/chimtech.2023.10.3.02 Methodology: D.O.Z., Yu.Yu.P. Project administration: Yu.Yu.P., A.N.Ch. Resources: Yu.Yu.P., I.I.Sh., A.Ya.P. Supervision: Yu.Yu.P. Validation: A.V.K. Visualization: D.O.Z., A.V.K. Writing – original draft: D.O.Z., Yu.Yu.P. Writing – review & editing: A.A.I., Y.G.M. ● Conflict of interest The authors declare no conflict of interest. ● Additional information Authors IDs: Yuliya Yu. Petrova, Scopus ID 6603754153; Anastasia A. Ivanova, Scopus ID 57196971233; Alexey N. Cheremisin, Scopus ID 57193064808; Ivan I. Shanenkov, Scopus ID 55543055400; Alexander Ya. Pak, Scopus ID 37059570300; Yuliya G. Mateyshina, Scopus ID 6506782050. 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