Abstract: The mean force between two highly like-charged macroions in the presence of monovalent counterions and added multivalent salt, within solvents of varying dielectric constants has been studied using Monte Carlo simulations. Without additional salt, the mean force is strongly repulsive at all macroion separations in solvents with a dielectric constant ϵ_r ≥ 30. However, in solvents having ϵ_r ≤ 30, the macroions experience effective attraction, indicating that attractive interactions between highly charged macroions can occur even without multivalent salt in nonpolar solvents with low dielectric constants. At a multivalent counterion-to-macroion charge ratio of β = 0.075, the mean force becomes attractive at short separations in solvents with ϵ_r = 54 containing 1:3 salt, as well as in all solvents with 1:5 salt, while still exhibiting significant repulsion at longer separations. In contrast, for solvents with 1:3 salt and dielectric constants ϵ_r = 68 and ϵ_r = 78.4, the mean force turns attractive at a higher salt concentration, around β = 0.225. The shift of the mean force to an attractive state at short separations signifies charge inversion on the macroion surface when a sufficient amount of salt is present. At a stoichiometric ratio of multivalent counterions, long-range repulsion vanishes, and attraction becomes significant. However, with excess salt, the strength of the attractive mean force diminishes. Additionally, the attractive force at a given salt concentration increases as the dielectric constant decreases and is stronger in systems with 1:5 salt than in those with 1:3 salt.

Abstract: Chalcone derivatives with intriguing optical and electrochemical properties have been synthesized and systematically studied for their potential as anticancer agents. This article, insights strategically synthesis followed by their spectroscopic, computational, electrochemical, and biological studies of 3-(naphthalen-3-yl)-1-phenylprop-2-en-1-one (3NPEO). The absorption and emission bands witness 320-370 nm and 375–462 nm respectively. The solvatochromic effect was investigated in different solvents of various polarities with significant Stokes shifts (50–87 nm) indicating intramolecular charge transfer (ICT) in the excited state. Molar absorptivity (1.7–4.26 × 10⁴ M⁻¹ cm⁻¹) and fluorescence quantum yields (0.368–0.917) were determined, along with nonlinear optical properties in solution. Cyclic voltammeter is employed to analyze Electrochemical parameters, while quantum chemical calculations (DFT) by B3LYP/G(d,p) in chloroform confirmed promising results with experimental data. Molecular docking and dynamics simulations revealed strong interactions with the progesterone receptor enzyme, supported by structure-activity relationship (SAR) analyses. In vitro cytotoxicity assays on the MDAMB-231 cell line demonstrated moderate tumor cell inhibitory activity, with apoptosis studies confirming early and late apoptosis induction. These results suggest that the title compound holds promise as a potential anticancer agent.

Abstract: We have recently shown that the sphere-in-contact model can be used as an educational and research tool in various contexts, such as the visualization of carbon structures (e.g. graphene, carbon nanotubes, carbon nanocones and graphite), heterogeneous catalysts, metal nanoparticles and organic molecules. In this study we present how it can be used to model the adsorbate structure of a monoatomic elements on the hexagonal close-packed surface of HCP and FCC metals to study long range ordering phenomena of monoatomic adsorbates on metals. We have used atoms of varying radius and colour to represent the metal surface atoms and the adsorbate atoms. The study reveals that many surface configurations are possible for a fixed adsorbate coverage (θ) by the movement of the adsorbate atoms in response to surface adsorbate-adsorbate repulsions. The movement of the particles (e.g. particle diffusion) can be seen directly in the model and this is caused by the user intervention. This has great educational but also research value as one can directly see how the adsorbate atoms reorder on the surface of a metal. We calculate the repulsive interaction energy of adsorbates using the sphere-in-contact model and are able to identify which surface adsorbed configuration is the lowest energy one. We find that this model will be useful in the rational design of catalytic materials and materials coatings with new technological applications where long range ordering of surface adsorbates is essential.

Abstract:

We describe an experiment in which we employ a radiofrequency sensor to measure pH changes in a liquid solution. The experiment is novel in a few ways. First, the sensor does not have contact with the liquid, but rather detects the change from the outside of a PVC pipe. Second, the change is detected using a Linear Discriminant Analysis model using values from an inverse Fourier transform of the frequency data as its features. We believe this to be the first use of Fourier anaylsis in contactless pH measurement using radio frequencies.

Abstract: One of the most challenging issues in catalytic water dissociation hydrogen production technology is understanding the activation mechanism of water. To gain insights into this process, a first-principles molecular dynamics method was used to simulate the catalytic dissociation of H2O on 88 alloy catalysts. The study's results revealed that a larger red shift of the center of the v1 and v3 modes of adsorbed H2O corresponds to a lower dissociation temperature. The resonance absorption of heat from water molecules by the frontier electron promotes the dissociation reaction. Comparing the frontier orbitals of precursors and intermediate states shows that the number of involved frontier orbitals significantly influences the catalytic reaction.

Abstract:

Conical intersections (CIs) are the most efficient channels of photodeactivation and energy transfer, while femtosecond spectroscopy is the main experimental tool delivering information on molecular CI-driven photoinduced processes. In this work, we undertake comprehensive ab initio investigation of the CI-mediated internal conversion in fulvene by simulating evolutions of electronic populations, bond lengths and angles, and time-resolved transient absorption (TA) pump-probe (PP) spectra. TA PP spectra are evaluated on-the-fly, by combining the symmetrical quasi-classical/Meyer-Miller-Stock-Thoss (SQC/MMST) dynamics and the doorway-window representation of spectroscopic signals. We show that the simulated time-resolved TA PP spectra reveal not only the population dynamics but also the key nuclear motions as well as mode-mode couplings. We also demonstrate that TA PP signals are not only experimental observables: They can also be considered as information-rich purely theoretical observables, which deliver more information on the CI-driven dynamics than conventional electronic populations. This information can be extracted by the appropriate theoretical analyses of time-resolved TA PP signals.

Abstract: In this work, we have studied the main decomposition reactions on the ground state of nitromethane (CH3NO2) with the CASPT2 approach. The energetics of the main elementary reactions of the title molecule have been analyzed on the basis of Gibbs free energies obtained from standard expressions of Statistical Thermodynamics. In addition, it is described a mapping method (orthogonalized 3D-representation) for the potential energy surfaces (PESs) by defining an orthonormal basis consisting of two Rn orthonormal vectors (n, internal degrees of freedom) that allows to obtain a set of ordered points in the plane (vector subspace) spanned by such a basis. Geometries and harmonic frequencies of all species and orthogonalized 3D-representations of the PESs have been computed with the CASPT2 approach. It is found that all of the analyzed kinetically controlled reactions of nitromethane are endergonic. For such a class of reactions, the dissociation of nitromethane into CH3 and NO2 is the process with lower acctivation energy barrier (G), that is, the C-N bond cleavage is the most favorable process. In contrast, there exists a dynamically controlled process that evolves through a roaming reaction mechanism and is an exergonic reaction at high temperatures: CH3NO2 [CH3NO2]* [CH3ONO]* CH3O + NO. The above assertions are supported by CASPT2 mappings of the potential energy surfaces (PESs) and semiclassical trajectories obtained by "on-the fly" CASSCF molecular dynamics calculations.

Abstract: A non-linear (non-additive) increase in stability of hexamers follows an increase in the total number of (i) aad (a double proton acceptor) plus add (a double proton donor) waters commonly linked with anticooperativity and (ii) the total number of intermolecularly delocalized electrons (intermolNdeloc) in the 3D space occupied by a hexamer. Subsequently, we obtained nearly a perfect linear correlation between increase in the cluster stability and intermolNdeloc. Individual water molecules that act as either aad or add: (i) delocalize the largest number of electrons throughout a cluster; (ii) are involved in the strongest attractive, hence energy-stabilizing intermolecular interaction with the remaining five waters; (iii) have the most significant quantum component of the intermolecular interaction energy and (iv) relative to six non-interacting water molecules, stabilize a hexamer the most, as quantified by a purposely derived mol-FAMSEC energy term. Clearly, the all-body approach used in the unified, molecular-wide and electron density (MOWeD)-based concept of chemical bonding contradicts the commonly accepted view that aad and add water molecules are involved in anticooperativity in 3D water hexamers. Consequently, we propose here a general definition of cooperativity that should be applicable to any n-membered molecular clusters, namely: the quantifiable, physics- and quantum-based cooperativity phenomenon is synonymous with the intermolecular all-body delocalization of electrons leading to the increase in stability of individual molecules on an n-membered cluster formation.

Abstract: The Second Law of Thermodynamics states that entropy increases in a spontaneous process in an isothermal and isolated system and characterizes the direction of evolution. Real systems are not isolated. Here we suggest the description of progress in non-isolated and influenced by external fields systems. One of these fields is temperature field. In this case only entropy is not enough, and we suggest using a new function Ls, which is analogous to the Lagrangian in classical mechanics. Instead of mechanical kinetic energy, Ls includes the product ST, and the system always evolves towards the increase of this modified Lagrangian Ls. The system reaches an equilibrium when the gradient of a total potential force is balanced by the gradients of entropic and thermal forces. For isolated systems the description is reduced to Second Law and Clausius inequality. It has several advantages in comparison to Onsager’s non-equilibrium thermodynamics. This approach does not need a gradient of chemical potential, and easily explains the basic aspects of Soret thermodiffusion and thermoelectric Peltier-Seebeck and Thomson (Lord Kelvin) phenomena in non-isothermal and non-isolated systems. Inside the black hole balance of gravitational and entropic forces may lead to a steady state or the black hole evaporation.

Abstract:

The Second Law of Thermodynamics states that entropy S increases in a spontaneous process in an ideal isothermal and isolated system, which characterizes the direction of evolution. Real systems are not isolated. They are influenced by external forces and fields. One of these fields is the temperature field. Here we suggest the description of progress in non-isolated and influenced by external fields system. In this case, only entropy is not enough, and we suggest using a new function Ls, which is analogous to the Lagrangian in classical mechanics. As before, it includes total potential energy but instead of mechanical kinetic energy, Ls includes the product ST, and the system always evolves towards increasing this modified Lagrangian. It reaches an equilibrium when the gradient of a total potential force is balanced by both the gradients of entropic and thermal forces. For isolated systems the description is reduced to Second Law and Clausius inequality. Our approach does not need a gradient of chemical potential, and it has several advantages compared to Onsager’s non-equilibrium thermodynamics. It easily explains the basic aspects of diffusion, Dufour effect and Soret thermodiffusion. The combination of electric, thermal, and entropic forces explains thermoelectric phenomena in non-isothermal and non-isolated systems, including Peltier-Seebeck and Thomson (Lord Kelvin) effects. Gravitational and entropic forces together inside a black hole may lead to a steady state or the black hole evaporation. They are also involved in influenced by Sun atmospheric processes.

Abstract: A simple and easily applicable analytical method for the simultaneous determination of Cd2+, Pb2+, Zn2+, Cu2+, and Cl- applying a modified with saffron-conjugated silver nanoparticles (AgNPs@Sa) is being presented. The modified CPE was then used for the simultaneous determination of Cd2+, Pb2+, Zn2+, and Cu2+ as well as chloride ions in soil and plants. The comparative analysis demonstrated a significant enhancement in the applicability of the modified electrode through the incorporation of silver nanoparticles (AgNPs) at the carbon paste electrode (CPE) surface, leading to the development of a poly-Sa-CPE. This newly proposed method offers notably superior qualitative performance compared to other metal nanoparticle-based modifications reported in the literature. The accordingly modified electrode was successfully applied in the development of a chloride ion. A novel sensor, is being proposed, that makes possible the determination of heavy metals and chorides in the same solution, in soil and plant samples. The enhanced sensitivity and selectivity of the poly-Sa-CPE system highlights its potential as a more effective alternative for heavy metal and chloride analysis, further demonstrating its advantages in electrochemical applications.

Abstract:

The total quantity and energy delivered through a gas grid is calculated using simple formulas that sum the increments measured at regular time intervals. These calculations are described in international standards (e.g., ISO 15112 and EN 1776) and guidelines (e.g., OIML R140). Currently, in the evaluation of the associated measurement uncertainty, the measurement results that enter into the calculation are assumed to be mutually independent. This assumption leads to underrating of the measurement uncertainty. There is a growing concern among transmission and distribution system operators that this assumption and the obtained values for the measurement uncertainty are not fit for purpose when fluctuations in gas quantity and quality increase, which occurs when injecting renewable energy gases such as hydrogen and biomethane. In a project in the European Partnership for Metrology programme, "Metrology for the hydrogen supply chain", the underlying assumptions of these uncertainty evaluations are revisited and reworked to be more adequate. The dependence of measurement results coming from, e.g., the same flow meter and gas chromatograph will be assessed for correlations, as well as other effects, such as the effect of the chosen mathematical approximation of the totalisation integral, and fluctuations in flow rate and gas quality. % The poster presentation gives an impression of the models being developed, the first findings and the magnitudes of the effects concerned. In this paper, an outline is given for the improvements that can be made in the measurement models to make them more responsive to the error structure of the measurement data, temporal effects in these data, and the fluctuations in gas quality and gas quantity.

Abstract: Methods for creating endofullerenes have been steadily improving since their discovery allowing for new types of endofullerenes to be created in larger numbers. When a molecule is trapped in a fullerene, the fullerene creates a harmonic trapping potential leaving most of the fundamental properties of the internal molecule intact. The fullerene cage does create a preferred axis for the internal molecule similar to studies of the alignment of molecules in the presence of an external electric field. We explore the alignment of AlF and N2 inside of C60. The interaction between the internal molecule and the fullerene cage is calculated using ab initio electronic structure methods. This interaction is then used to calculate the spectroscopic properties of the internal molecule. The internal molecules are found to be strongly aligned despite all spectroscopic constants calculated being relatively unaffected by the fullerene cage.

Abstract: Continuing the investigation already started (See Farcaş, A.-A.; Bende, A. PCCP 2024, 26, 14937), the light absorption and charge-transfer properties of the dopamine (DA), dopamine zwitterion (called as dopamine-semi-quinone or DsQ) and dopamine-o-quinone (DoQ) adsorbed on the graphene nanoparticle surface have been investigated using the ground state and linear-response time-dependent density functional theories, considering the B97X-D3BJ/def2-TZVPP level of theory. In terms of the strength of molecular adsorption on the surface, the DsQ form has 50 % higher binding energy than that for the DA or DoQ cases (-20.24 kcal/mol vs. -30.41 kcal/mol). The results obtained for electronically excited states and UV-Vis absorption spectra show that the photochemical behavior of DsQ is more similar to DA than that observed for DoQ. Of the three systems analyzed, the DsQ-based complex showed the most active CT phenomenon, both in terms of the number of CT-like states and the amount of charge transferred. Of the first thirty electronically excited states computed for the DsQ case, eleven are purely CT-type and nine are mixed CT and localized (or Frenkel) excitations. By varying the adsorption distance between the molecule and the surface vertically, the amount of charge transfer obtained for DA decreases significantly as the distance increases, for DoQ it remains stable, while for DsQ there are states for which little change is observed, while for others there is a significant change. Furthermore, the mechanistic compilation of the electron orbital diagrams of the individual components cannot describe in detail the nature of the excitations inside the complex.

Abstract: Recently, oriented external electric fields (OEEFs) have earned much attention due to the possibility of tuning the properties of electronic systems. From a theoretical perspective, one can resort to electronic structure calculations to understand how the direction and strength of OEEFs affect the properties of electronic systems. However, for multi-reference (MR) systems, calculations employing the popular Kohn-Sham density functional theory with the traditional semilocal and hybrid exchange-correlation energy functionals can yield erroneous results. Owing to its decent compromise between accuracy and efficiency for MR systems at the nanoscale (i.e., MR nanosystems), in this study, thermally-assisted-occupation density functional theory (TAO-DFT) is adopted to explore the electronic properties of n-acenes (n = 2--10), containing n linearly fused benzene rings, in OEEFs, where the OEEFs of various electric field strengths are applied along the long axes of n-acenes. According to our TAO-DFT calculations, the ground states of n-acenes in OEEFs are singlets for all the cases examined. The effect of OEEFs is shown to be significant on the vertical ionization potentials and vertical electron affinities of ground-state n-acenes with odd-number fused benzene rings. Moreover, the MR character of ground-state n-acenes in OEEFs increases with the increase of the acene length and/or the electric field strength.

Abstract: After an introductory reminder of safety concerns pertaining to early rechargeable battery technologies, this review discusses current understandings and challenges of sodium-ion batteries. Sodium-ion technology is now being marketed by industrial promoters who are advocating its workable capacity, use of readily accessible and cheaper key cell components. Often claimed to be safer than lithium-ion cells, currently only limited scientific-sound safety assessment of sodium-ion cells has been performed. However, the predicted sodium-ion development roadmap reveals that significant variants of sodium-ion batteries will potentially enter the market in the near future. With recent experiences of lithium-ion battery failures, sodium-ion battery safety management will constitute a key aspect of successful market penetration. As such this review discusses the safety issues of sodium-ion batteries presenting a twofold innovative perspective: i) in terms of comparison with the parent lithium-ion technology making use of the same working principle and similar flammable non-aqueous solvent basis and ii) anticipating the arrival of innovative sub-chemistries at least partially inspired from successive generations of lithium-ion cells. The authors do hope that the analysis provided will assist the concerned stakeholders in the quest for safe marketing of sodium-ion batteries.

Abstract: General derivation of the well-known Ren-Otsuka relation, 1/α (dTo)/dx=-α/β (where To, x, α and β(>0) are the transformation temperature, the composition, as well as the composition and temperature coefficient of the critical shear constant, c’, respectively) for shape memory alloys, SMAs, is provided based on the similarity of interatomic potentials in the framework of dimensional analysis. A new dimensionless variable, to(x)=(To (x))/(Tm (x) ), describing the phonon softening (where Tm is the melting point) is introduced. The dimensionless values of the heat of transformation, H, and entropy, S as well as the elastic constants c’, c44, A=c44/c' are universal functions of to(x) and have the same constant values at to(0) within sub-classes of host SMAs having the same type of crystal symmetry change during martensitic transformation. The ratio of (dto)/dx and α has the same constant value for all members of a given sub-class and relative increase of c’ with increasing composition should be compensated by the same decrease of to. In the generalized Ren-Otsuka relation the anisotropy factor, A appears instead of c’ and α as well as β are the differences of the corresponding coefficients for the c44 and c’ elastic constants. The obtained linear relation between h and to rationalizes the observed empirical linear relations between the heat of transformation measured by DSC (QAM) and the martensite start temperature, Ms.

Abstract: The Coulomb coupling between transition densities of the pigments in photosynthetic pigment-protein complexes, termed excitonic coupling, is a key factor for the description of optical spectra and energy transfer. A challenging question is the quantification of the screening of the excitonic coupling by the optical polarizability of the environment. We use the equivalence between the sophisticated quantum chemical polarizable continuum (PCM) model and the simple electrostatic Poisson-TrEsp approach to analyze the distance and orientation dependence of the dielectric screening between chlorophylls in photosystem I trimers. On the basis of these calculations we find that the vacuum couplings Vmn(0) and the couplings in the dielectric medium Vmn=fmnVmn(0) are related by the empirical screening factor fmn=0.60+39.6θ(|κmn|−1.17)exp(−0.56Rmn/Å), where κmn is the usual orientational factor of the dipole-dipole coupling between the pigments, Rmn is the center-to-center distance, and the Heaviside-function θ(|κmn|−1.17) ensures that the exponential distance dependence only contributes for in-line type dipole geometries. We are confident that the present expression can be applied also to other pigment-protein complexes with chlorophyll or related pigments of similar shape. The variance between the Poisson-TrEsp and the approximate coupling values is found to decrease by a factor of 8 and 3-4 using the present expression, instead of an exponential distance dependent or constant screening factor, respectively, assumed previously in the literature.

Abstract: Carbon Quantum Dots (CQDs) have emerged as promising nanomaterials for enhancing the performance of supercapacitors, offering unique advantages such as high surface area, excellent electrical conductivity, and tunable surface chemistry. This review provides a comprehensive overview of recent advancements in the synthesis, characterization, and integration of CQDs into supercapacitor devices. Various synthesis methods, including chemical oxidation, hydrothermal/solvothermal methods, microwave-assisted synthesis, and pyrolysis, are discussed, highlighting their impact on the structural and electrochemical properties of CQDs. Characterization techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy are elucidated for assessing the morphology, crystallinity, and optical properties of CQDs. The integration of CQDs into supercapacitors, including their utilization in composite electrodes, binder-free electrodes, and doping strategies, is explored to enhance specific capacitance, energy density, power density, and cycle stability of the devices. Challenges and future perspectives in the field are outlined, emphasizing the need for scalable synthesis methods, enhanced electrochemical performance, and sustainable device engineering to realize the full potential of CQD-based supercapacitors for various energy storage applications. This review aims to provide insights into the current state of research and guide future endeavors towards developing high-performance and environmentally sustainable energy storage technologies.

Abstract: This paper focuses on determining the State of Charge (SOC) of lithium-ion batteries when operating and the influence the State of Health (SOH) has on SOC determination. The paper studies the effects of the discharge rate on the battery performance and how it modifies the evaluation of the SOC. The article also analyzes the effects of battery aging on the determination of SOC. The online determination of SOC in lithium-ion batteries uses the linear behavior of battery discharge and how the discharge rate modifies the battery voltage slope. The paper develops a simple algorithm that relates the SOC of the battery with the online battery voltage. The proposed measurement method uses a very short controlled discharge at a specific rate that avoids unexpected interferences with the current operation of the battery during charge or discharge. We conducted a simulation process to evaluate the evolution of the SOC in Li-ion batteries for different operating stages. Experimental tests validate the proposed methodology, showing a close agreement between theoretical values and experimental results with 98% accuracy. The paper also deals with the determination of the aging factor in lithium batteries as a critical parameter to calculate the SOC. The method determines the aging factor using specific simulation for this goal. The results are compared to values obtained in an experimental test within high agreement (>93%). The proposed model applies to almost any lithium battery and is validated for a wide range of Battery State of Health, up to 50%, within accurate prediction, higher than 90%.