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Keywords: nanoparticles

Colloidal protection of magnetite hydrosols with polysaccharides

https://doi.org/10.58224/2619-0575-2025-8-3-2
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Abstract
This article investigates the stabilization of aqueous dispersions of magnetic Fe₃O₄ nanoparticles using polysaccharide stabilizers. The effect of electrolyte coagulants and polysaccharide stabilizers on the stability of magnetite hydrosols and their stability at physiological pH with and without the addition of polysaccharides is stud-ied. The results demonstrate the effectiveness of nonionic polysaccharides, such as hydroxypropyl methylcellulose and hydroxyethylcellulose, in stabilizing magnetic nanoparticles from electrolyte coagulation and over time, which is important for their application in medicine.
Objectives. To obtain and characterize magnetite hydrosols and to study their stabilization with polysaccharides over time and with the addition of non-indifferent and indifferent electrolytes.
Methods. Hydrosol coagulation was studied photometrically. The size of hydrosol nanoparticles was determined using dynamic light scattering.
Results. Nonionic polysaccharides, such as hydroxyethyl cellulose and hydroxypropyl methylcellulose, are promising for stabilizing aqueous dispersions (hydrosols) of Fe3O4 magnetic nanoparticles.
Conclusions. The coagulation threshold of magnetite hydrosol with a non-differentiated electrolyte, sodium hy-droxide, is 20,5 times lower than the coagulation threshold of magnetite hydrosol with an indifferent electrolyte, sodium chloride. Hydroxyethyl cellulose and hydroxypropyl methylcellulose exhibited the greatest protection of magnetite hydrosol from coagulation with sodium chloride. Hydroxypropyl methylcellulose exhibited the greatest protection of magnetite hydrosol from coagulation with sodium hydroxide. Sols containing hydroxypropyl methyl-cellulose exhibit the greatest stability over time at pH 7.4 (the pH of blood), created by the addition of a phosphate-buffered saline mixture.
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Adsorption of kappa-carrageenan on the surface of chitosan and its sulfuric acid salt and stabilization of chitosan-sulfate nanoparticles by it

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 5-18 p.
Abstract
Objectives: to investigate the adsorption of k-carrageenan on the surface of chitosan at pH 7.4 and chitosan treated with dilute sulfuric acid solution (pH 2.5-2.7). To develop a method for obtaining the sol of the chitosan sulfate salt - chitosan sulfate (CX) and to investigate its stability in time depending on the use of various acids as precursors, and its increase with the addition of different concentrations of k–carrageenan.
Methods. To determine the viscosity of polymer solutions, their molecular weight and to study the adsorption of k-carrageenan on CX, the method of capillary viscometry was used. The assessment of the stability of the zones over time was carried out photometrically.
Results. The adsorption of k-carrageenan on chitosan and CX has been studied: experimental isotherms of k-carrageenan adsorption have been constructed.on the surfaces of chitosan and CX, the constants of the Langmuir equation are calculated and complete theoretical adsorption isotherms are constructed using them. A method for obtaining a CX hydrosol with a positive particle charge has been developed. The stability of CX sols in time both without additives and with additives of k-carrageenan in time has been studied.
Conclusions. The adsorption of k-carrageenan on chitosan and CX is monomolecular. The adsorption equilibrium constant is greater with the adsorption of k-carrageenan on the surface of CX, and the maximum adsorption value is greater with the adsorption on the surface of chitosan. Of the acids used as precursors, the sol obtained using citric acid has the greatest stability. With an additional additive to the sols of the protective colloid - k-carrageenan to sols obtained using hydrochloric acid and citric acid, the sol obtained with the use of hydrochloric acid and carrageenan additives in the range of 0.04-0.06% has the greatest aggregate stability.
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ANALYSIS OF MAGNETITE IN THE FE3O4/C NANOCOMPOSITE

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 30-41 p.
Abstract
This paper presents the magnetite study results of a Fe3O4/C nanocomposite obtained with air pyrolysis of a heterogeneous system which includes iron dichloride tetrahydrate – the source of magnetite nanoparticles (NPs) – and polyacrylonitrile (PAN) – the source of a carbon shell for nanoparticles protection from issues like aggregation. Methods such as Mössbauer spectroscopy and X-ray diffraction analysis are used for studying and determine the magnetite NP formation way. There are two types of NPs in the system studied: ferrimagnetic and superparamagnetic ones, the difference between which is clearly watched when taking Mössbauer spectra – sextets and doublets relatively. All magnetite NPs are established to be formed according to the reaction chain the inter-mediate elements of which is ferrous carbonate well-known for its decomposition into magnetite upon heating: FeCl2 → FeCO3 → Fe3O4. This transformation occurs in the temperature range from 200 oC to 400 oC above which an ability of the carbon shell to protect NPs is gradually reduced that leads to agglomeration and oxidation to hematite α-Fe2O3.
To study the magnetite obtained, size distribution of magnetite crystallites and the degree of nonstoichiometry are estimated. According to various calculations, the average crystallite size is 9-10 nm.
To preserve the NP properties, storage methods are important to be chosen properly, thence Mössbauer spec-troscopy of the Fe3O4/C nanocomposite is carried out after keeping it in air at room temperature for 1 year.
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