Romana Cerc Korošec

A nonionic type V deep eutectic solvent (DES) combining hydrophobic (−)-menthol and hydrophilic resorcinol was prepared and investigated as a solvent for amphiphilic caffeine. Differential scanning calorimetry and thermogravimetric analysis were first used to determine the eutectic composition and characterize its thermal behavior. The menthol-to-resorcinol molar ratio of 2:1 was subsequently selected for physicochemical investigation. Clear homogeneous solutions containing up to 0.701 mol·kg⁻¹ caffeine were prepared, corresponding to 136 g of caffeine per kilogram of DES. Density, speed of sound, and viscosity were measured over the temperature range from 293.15 to 313.15 K. These data were used to evaluate the thermal expansion, volumetric and acoustic properties, intermolecular free length, and concentration and temperature dependences of viscous flow. The viscosity results were further analyzed using the Arrhenius, Jones–Dole, and Eyring–Feakins approaches and compared with the behavior of caffeine in water, ethylene glycol, and methyl salicylate. DFT calculations and molecular electrostatic potential surfaces were used to examine the local organization of the DES and the possible incorporation of caffeine through interactions with both its polar and less-polar regions. The combined experimental and computational approach provides a molecular and thermodynamic basis for evaluating this DES as a caffeine-solubilizing and delivery medium.

The rational design of ionic liquids (ILs) is often hindered when promising candidates, such as carboxy-functionalized imidazolium chlorides, exhibit properties like extreme viscosity that preclude direct experimental measurement. In this study, we synthesized a series of these ILs and addressed this “experimental gap” with a combined computational strategy. For the few liquids accessible to measurement, we obtained density, viscosity, and conductivity data. For the majority, we turned to atomistic modeling and machine learning. Symmetry-adapted perturbation theory (SAPT2) energy decomposition uncovered the dominance of electrostatic interactions in governing viscosity, an insight obscured by total binding energies from DFT. In addition, a recently developed machine learning model, named IonIL-IM-D1, predicted the density of [C₂COOHeim][Cl] with an error of less than 1% upon validation, though experimental verification for the solid candidates was not possible. This predictive framework was extended to propose and evaluate new IL candidates, offering a complementary strategy for exploring macroscopic behavior when direct experimental measurements are not feasible.

Three novel coordination compounds were synthesized by performing the reactions between Co(NO3)2∙6H2O and 2-(hydroxymethyl)pyridine (2hmp) at ambient temperature: [Co(2hmp)3](NO3)2 (1), [Co(2hmp)3](NO3)2∙CH3COCH3 (2) and [Co(2hmp)2(OH2)2](NO3)2 (3). When leaving product 3 in its mother liquid in a closed vessel for prolonged time, the crystals of [Co(NO2)(2PyCOO)2(OH2)] (4) also formed by a series of redox processes (2PyCOO = 2-pyridinecarboxylate). All four products were structurally characterized by means of X-ray single-crystal diffraction, revealing a hexa-coordinated cobalt centre in the mononuclear coordination species and the chelating-N,O binding mode of 2hmp ligand. Furthermore, the determined crystal structures were also evaluated by Hirshfeld surface analysis. The thermal and electrochemical behaviour of products 1, 3 and 4, was also studied by TG-DSC-MS and cyclic voltammetry, respectively. For all investigated compounds, the thermal decomposition in the air atmosphere is complex and occurs in at least three overlapped steps, yielding Co2O3 as the solid residue. The thermal stability of the compounds is related to the redox stability obtained by cyclic voltammetry, showing compound 4 being most thermally stable. On the other hand, CV measurements confirmed the oxidation state of central cobalt ion as expected by the previous structural study.

Fire-retardant intumescent coatings offer an effective means of enhancing the fire resistance of combustible substrates such as wood. These coatings have a complex chemical composition and, when exposed to temperatures above 200 °C, undergo an intumescent reaction accompanied by the release of non-flammable gases, forming an expanded, charred layer with low thermal conductivity. This provides thermal insulation and acts as a physical barrier against heat, oxygen, and flammable volatiles. In this study, the applicability of several thermoanalytical techniques for evaluating the performance of three different intumescent coatings applied to spruce wood was investigated. Simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that coating No. 3 was the most efficient, initiating substrate protection at the lowest temperature and reducing the combustion enthalpy by approximately 50% compared to uncoated wood. DSC-microscopy visualization enabled direct observation of the intumescent expansion, degradation of the carbonized protective layer, and delayed thermal decomposition of coated wood. Furthermore, a comparison between TGA-MS and TGA-IST16-GC-MS demonstrated the superiority of chromatographic separation for identifying evolved gaseous products. While TGA-MS is effective for detecting small gaseous species (e.g., H₂O, CO₂, formaldehyde), TGA-IST16-GC-MS enables the deconvolution of many degradation products evolving simultaneously, allowing for distinction between flame-retardant-related species, polymer backbone fragments, nitrogen-rich heterocycles, and small oxygenated molecules in the most effective coating.

12th Socratic Lectures symposium took place online on January 11, 2025. It featured five plenary lectures, 12 scientific sessions, a poster session and a newly introduced session called “The student zone”. As we received more than 40 papers, The Proceedings of the 12th Socratic Lectures is organized in three parts. Part I contains mainly papers from the medical fields, Part II contains mainly papers from the natural and social sciences and Part III contains standard operating procedures of a pipeline for assessment of extracellular particles and related publications. The pipeline was designed within the preparatory project Nanostructurome. Socratic lectures present an important meeting point for the participants of various projects and for the publication of scientific results, opinions, repositories, and any kind of documents that are useful in the management of the projects. But in the first place, the 12th Socratic lectures are a meeting point for scientists, artists and friends from many different fields.