Milán Szőri

Carbodiimide formation critically enhances the thermal stability of 4,4’‐methylenediphenyl diisocyanate (MDI)‐based polyurethane systems, yet the chemorheological mechanisms governing polycarbodiimide gelation remain poorly resolved. In this study, the carbodiimidization of a 10 wt.% MDI solution in ortho‐dichlorobenzene (ODCB), catalyzed by 3‐methyl‐1‐phenyl‐2‐phospholene‐1‐oxide (MPPO), is investigated with emphasis on the emergence of a clear yellowish organogel prior to curing. Gel formation is characterized by cone–plate rotational viscometry using a two‐step protocol in controlled shear rate mode (300 and 30 s ⁻¹ ) over 338–353 K (65°C–80°C). Raw viscosity data are treated with Hampel filtering and Savitzky–Golay smoothing to reduce experimental noise. The evolution of shear viscosity is analyzed through time‐ and temperature‐dependent representations, and rheokinetic modeling is performed using empirical first‐ and fractional‐order nonlinear regressions. The cross‐linking process follows an apparent rheokinetic order of 1.35, while the apparent activation energies of gelation are E _k = 41.1 ± 4.3 kJ mol ⁻¹ and E _t = 42.4 ± 1.9 kJ mol ⁻¹ , depending on the derivation methodology, which correspond to the energy of carbodiimide bond formation. Inspection on different definitions of gel time are also examined based on the divergence of viscosity. Complementary FTIR, Raman, and DMA measurements provided additional chemical and viscoelastic characterization of the obtained organogel. These results provide a quantitative kinetic framework for describing gelation in industrial polycarbodiimide systems.

Voltage-sensitive dyes (VSDs) are fluorescent molecules that detect changes in the membrane potential, making them invaluable for studying electrical activity in neurons, cardiac cells, and other excitable tissues. They are widely used in neuroscience and physiology to visualize and measure real-time voltage dynamics in cellular networks and whole tissues. VSDs exhibit a high sensitivity to their surrounding environment, which leads to notable solvation relaxation and a substantial Stokes shift upon excitation. Accurate prediction of their fluorescence spectra requires an advanced solvation model that captures these dynamic effects. In this work, we extend the Similarity Transformed Equation-of-Motion Domain-Based Local Pair Natural Orbital Coupled Cluster with Singles and Doubles (STEOM-DLPNO-CCSD) method, a computationally efficient approach for vertical excitation energies, to predict fluorescence spectra for VSDs. While the default perturbative solvation correction at the Hartree-Fock level has proven effective for some excited state calculations, it fails to account for the electron correlation effects that are crucial for accurate fluorescence spectra predictions. To address this, we incorporate a time-dependent density functional theory-based perturbative solvation correction, which improves the accuracy of the methods by better capturing the necessary correlation effects. The methodology is validated through studies of two carefully selected VSDs, (E)-3-(4-(2-(6-(dibutylamino)naphthalen-2-yl)vinyl)pyridin-1-ium-1-yl)propane-1-sulfonate (di-4-ANEPPS) and 4-((E)-4-((E)-4-(diethylamino)-2-methoxystyryl)styryl)-2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)benzenesulfonate (sRhoVR-1). The developed quantum chemical protocol allows for accurate prediction of fluorescence maxima for dyes with a predominant excited state and can accommodate computational constraints without greatly compromising precision. However, the study also highlights the need for further improvements for the prediction of peak intensity, suggesting that explicit solvent models or hybrid quantum mechanics/molecular mechanics (QM/MM) approaches could be valuable for future work. The proposed method provides a powerful tool for the design of VSDs optimized for specific environments and applications.

This study investigates how phospholipid headgroups influence passive membrane penetration and structural impact of four nitrogen-, sulfur-, and oxygen-containing heterocycles (NSO-HETs)—N-methyl-2-pyrrolidone (PIR), 1,4-dioxane (DIOX), oxane (OXA), and phenol (PHE). Using all-atom molecular dynamics simulations combined with Accelerated Weight Histogram free energy calculations, the passive transport of NSO-HETs across DPPC, DPPE, DPPA, and DPPG bilayers was characterized. DPPG showed the highest membrane affinity, increasing permeability (logP_memb/bulk) by 27–64% compared to DPPE, associated with the lowest permeability and tightest lipid packing. Free energy barriers are also decreased in DPPG relative to DPPE; PIR’s central barrier dropped from 19.2 kJ/mol (DPPE) to 16.6 kJ/mol (DPPG), while DIOX’s barrier decreased from 7.2 to 5.2 kJ/mol. OXA exhibited the lowest central barriers (1.2–2.2 kJ/mol) and uniquely accumulated at higher concentrations in the bilayer center than in bulk water, with free energy ranging from −3.4 to −5.9 kJ/mol. PHE and OXA caused significant bilayer thinning (up to 11%) and reduced lipid tail order, especially in DPPE and DPPA. Concentration effects were most pronounced in DPPE, where high solute loading disrupted lipid order and altered free energy profiles. These results highlight the crucial role of headgroup identity in modulating NSO-HET membrane permeability and structural changes.

Interactions between per- and polyfluoroalkyl substances (PFASs) and small plastic particles (PPs) in the micro- and nanosize ranges raise serious concerns due to the possible joint harmful physiological effects of these emerging contaminants on the ecosystem. In this study, the adsorption of undecafluorohexanoic acid (UFHA), a C6 representative of PFASs, on amidine-functionalized polystyrene PP is investigated by using experimental and computer simulation methods. Electrophoretic light scattering measurements reveal that UFHA adsorbs strongly on oppositely charged PP leading to charge neutralization and overcharging at appropriate concentrations. Charged UFHA–PP adducts form stable colloids, while rapid aggregation was observed at the isoelectric point. Simulation results indicate that, at least at isoelectric conditions, a H-bond is formed between the oppositely charged groups of the PP and UFHA, providing an additional driving force, besides charge pairing, for this adsorption. This strong interaction results in an association of the PP chains and the majority of UFHA molecules, although some of the UFHA molecules can still stay isolated from these associates. It is found that the ionic strength applied in the solutions influences the adsorption process through charge screening of the PP surface, while it does not affect the charge neutralization conditions. Accordingly, the spatial distribution of the Na+ and Cl– ions is found to be largely uncorrelated with that of the polymeric chains and UFHA molecules at every salt concentration studied. The findings obtained provide new insights into the adsorption mechanism of UFHA onto a charged polystyrene surface and the features of the new interfaces formed, which play a key role in the joint migration and toxicity of these emerging contaminants.

Nuclear incidents release hazardous ⁹⁰Sr, posing risks to health. Seeking chelating agents capable of removing ⁹⁰Sr is critical for nuclear safety and development. In our work, the main goal was to develop a substantial yet straightforward method to support the design of viable, in vivo stable chelating agents for radiostrontium. To investigate, we implemented the highly accurate density functional theory (DFT)-based r²SCAN-3c composite method and isothermal titration calorimetry (ITC). Our methods were validated through the characterization of calcium (Ca²⁺) and strontium (Sr²⁺) chelation by ethylenediaminetetraacetic acid (EDTA). The chosen DFT model was able to approximate the literature value (ΔΔG _DFT of 15.4 kJ/mol for the ion exchange reaction from Ca-EDTA to Sr-EDTA, compared to the literature value of 11.0 kJ/mol), while the thermodynamic parameters obtained from the ITC study of calcium EDTA chelation were almost identical to those found in the literature. With the validated methods, strontium chelation by (7,16-bis-malonate)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-bis-malonic acid (Decorporol) was first synthesized and then examined. Our DFT calculations revealed that the exchange reaction from Ca²⁺ to Sr²⁺ with Decorporol has an exergonic (-14.1 kJ/mol) Gibbs free energy profile, which is also approved by the experimental Gibbs free energy change of -34.5 ± 1.1 kJ/mol obtained from the ITC measurements. Measurements at elevated temperatures and physiological conditions did not impact chelation significantly; therefore, in vivo application of the chelating agent is feasible.

A laser sensor system was developed to be employed in power plants and specifically engineered for high-particulate and high-temperature environments to be applicable for the online monitoring of hydrogen sulfide (H₂S) and carbon monoxide (CO) near the furnace water wall. The system was designed based on frequency division multiplexing (FDM) and tunable diode laser absorption spectroscopy (TDLAS). A corrosion-resistant Herriott multipass cell was designed to withstand temperatures of up to 120 °C while providing an 18 m optical path length. The sensor system exhibits measurement uncertainties below 1.5% and 2% under mechanical vibration testing and thermal cycling testing. Allan variance analysis revealed minimum detection limits of 111 ppb for H₂S and 116 ppb for CO, achievable at integration times of 178 and 144 s, respectively. Long-term field validation in a coal-fired boiler included multipoint sampling to assess the sensor system performance, simultaneously analyzing water-wall combustion dynamics and evaluating corrosion propensity.

Limona ketone, as a significant intermediate in the oxidation of limonene, plays a crucial role in environmental and human health impacts. In this article, we present a study on the reaction kinetics and mechanism of ozonolysis of limona ketone. The rate constant for the reaction between limona ketone and ozone was measured under standard conditions of 298 K and atmospheric pressure by the absolute rate method and was determined to be (1.2 ± 0.1) × 10^-16 cm³ molecule^-1 s^-1. The reaction products were probed online with a vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometer and utilized to elucidate the reaction mechanism with the aid of kinetics. The atmospheric lifetime of limona ketone was discussed with the present reaction rate constant of limona ketone with O₃, combined with the literature-reported rate constants for OH and NO₃ reaction. The present results show that in urban areas with elevated ozone levels, ozonolysis is the primary pathway for the degradation of limona ketone, and its low-volatility organic products could significantly contribute to the formation of secondary organic aerosols.

Carbon‐free fuels like ammonia (NH₃) and hydrogen (H₂) offer significant potential in combating global warming by reducing greenhouse gas emissions and moving toward zero carbon emissions. Over the past few years, our research has focused on understanding the combustion behavior of carbon‐neutral and carbon‐free fuels. In particular, we have explored the combustion characteristics of NH₃ when blended with various hydrocarbons and oxygenates. Our investigation revealed that carbon‐nitrogen cross‐chemistry plays a crucial role in shaping the combustion properties of NH₃‐hydrocarbon/oxygenate blends. Specifically, the chemistry of amino (NH₂) radicals is vital in influencing the low‐temperature reactivity of these blends. Understanding the interactions between carbon and nitrogen is essential for optimizing combustion processes and improving the emissions profile of NH₃‐based fuels. Recognizing the significance of this cross‐chemistry, we investigated the reaction kinetics of NH₂ radicals with formaldehyde (H₂CO) and acetaldehyde (CH₃CHO) using high‐level ab initio and transition state theory calculations. We computed the potential energy profiles of these reactions at the CCSD(T)/CBS//M06‐2X/aug‐cc‐pVTZ level of theory to analyze the reactivity of NH₂ radicals at various C─H bond sites. The newly derived rate constants have proven to be highly sensitive for modeling the low‐temperature oxidation of NH₃‐dual fuel blends, significantly enhancing the predictive accuracy of our previously published kinetic models. This work offers valuable insights into the role of NH₂ radicals, thereby advancing the development of NH₃‐dual fuel systems.