Publications

Abstract Amino acid ionic liquids have garnered significant attention for their potential in electrochemical energy storage due to their wide electrochemical stability windows and inherent safety. The performance of ChGly as an electrolyte for supercapacitors has been compared to that of highly efficient conventional ionic liquids. However, a thorough understanding of the microstructural characteristics responsible for the enhanced properties of ChGly aqueous solutions remains largely unexplored. In this study, ab initio molecular dynamics simulations were employed to investigate the energetic, structural, transport and spectroscopic properties of ChGly-based pure and aqueous electrolytes. A comprehensive analysis of the cation-anion and water-ion hydrogen bonding was conducted for both electrolyte systems. Structural features were examined using radial and spatial distribution functions, while the vibrational power spectra were analyzed to identify significant differences in intermolecular interactions between pure and aqueous electrolytes, stemming from modified solvation shell structures. The findings presented in this work shed light on crucial structural and spectroscopic distinctions between pure and aqueous ChGly electrolytes, providing valuable insights for further advancements in the field.

Abstract <jats:p> Ionic liquids (ILs) are a unique class of electrolytes, which characteristics make them suitable for use in solar cells, supercapacitors, and fuel cells<jats:sup>1</jats:sup>. Due to the appealing properties such as good electrochemical stability, low vapour pressure, high concentration of ions and the lack of solvent, they have been under intense study since the early 2000s. Although numerous theoretical<jats:sup>2,3</jats:sup>, computational<jats:sup>4,5</jats:sup>, and experimental studies<jats:sup>6,7</jats:sup> have shed light on the interfacial properties of ILs, which differ noticeably from the aqueous electrolytes, multiple open questions remain. One such problem is how the interfacial capacitance is affected by the ambient temperature, as studies have shown both positive and negative temperature dependences<jats:sup>8,9</jats:sup>. Understanding the temperature dependence of interfacial capacitance is crucial as it is relevant for the description of energy storage and is one of the few quantities, which can be estimated both experimentally and computationally.</jats:p> <jats:p>In this study, we combine the density functional theory (DFT) calculations with molecular dynamics (MD) simulations of graphene (Gr) | EMImBF<jats:sub>4</jats:sub> IL interface to explain the effect of temperature on capacitance. MD simulations allow us to investigate the probable distribution of ions near the electrode’s surface and relate the changes of ILs structure to the capacitance using the interfacial bilayer model (IBL). We show that the increase of temperature affects the capacitance near the potential of zero charge by attenuating the overscreening without a notable change in the IL interfacial structure. The characteristic peaks and plateaus in the capacitance potential dependence are explained through the concepts of IL layering and saturation of the second IL layer described in the IBL. Using the DFT calculations, we estimate the impact of the quantum capacitance of Gr on the total interfacial capacitance and its temperature dependence. By accounting for the limiting quantum capacitance, the total interfacial capacitance was significantly altered in the case of the Gr electrode, as the effect of the temperature was dampened, and a V-shaped capacitance curve was obtained.</jats:p> <jats:p>Acknowledgements:</jats:p> <jats:p>This work was supported by the Estonian Research Council grant PSG249 and by the EU through the European Regional Development Fund under project TK141 (2014-2020.4.01.15-0011). The financial support from FCT/MCTES through the Portuguese national funds, project No. UID/QUI/50006/2021 (LAQV@REQUIMTE) is also acknowledged.</jats:p> <jats:p>References:</jats:p> <jats:p>1 D. R. MacFarlane, N. Tachikawa, M. Forsyth, J. M. Pringle, P. C. Howlett, G. D. Elliott, J. H. Davis, M. Watanabe, P. Simon and C. A. Angell, <jats:italic>Energy Environ. Sci.</jats:italic>, 2014, <jats:bold>7</jats:bold>, 232–250.</jats:p> <jats:p>2 A. A. Kornyshev, <jats:italic>J. Phys. Chem. B</jats:italic>, 2007, <jats:bold>111</jats:bold>, 5545–5557.</jats:p> <jats:p>3 Z. A. H. Goodwin and A. A. Kornyshev, <jats:italic>Electrochem. Commun.</jats:italic>, 2017, <jats:bold>82</jats:bold>, 129–133.</jats:p> <jats:p>4 M. Salanne, <jats:italic>Phys. Chem. Chem. Phys.</jats:italic>, 2015, <jats:bold>17</jats:bold>, 14270–14279.</jats:p> <jats:p>5 I. V. Voroshylova, H. Ers, V. Koverga, B. Docampo-Álvarez, P. Pikma, V. B. Ivaništšev and M. N. D. S. Cordeiro, <jats:italic>Electrochim. Acta</jats:italic>, 2021, <jats:bold>379</jats:bold>, 138148.</jats:p> <jats:p>6 L. Siinor, K. Lust and E. Lust, <jats:italic>J. Electrochem. Soc.</jats:italic>, 2010, <jats:bold>157</jats:bold>, F83.</jats:p> <jats:p>7 V. Lockett, M. Horne, R. Sedev, T. Rodopoulos and J. Ralston, <jats:italic>Phys. Chem. Chem. Phys.</jats:italic>, 2010, <jats:bold>12</jats:bold>, 12499–12512.</jats:p> <jats:p>8 F. Silva, C. Gomes, M. Figueiredo, R. Costa, A. Martins and C. M. Pereira, <jats:italic>J. Electroanal. Chem.</jats:italic>, 2008, <jats:bold>622</jats:bold>, 153–160.</jats:p> <jats:p>9 M. Drüschler, N. Borisenko, J. Wallauer, C. Winter, B. Huber, F. Endres and B. Roling, <jats:italic>Phys. Chem. Chem. Phys.</jats:italic>, 2012, <jats:bold>14</jats:bold>, 5090–5099. </jats:p>

Abstract This work describes the effect of potential and temperature on the grapheneionic liquid (EMImBF4) interfacial structure and properties with the focus on a novel phenomenon of ionic saturation. We apply classical molecular dynamics simulations to reproduce well-known phenomena of overscreening, mono -layer formation, and temperature-induced smearing of the interfacial structure. Using quantum density functional theory calculations, we show how quantum capacitance dampens the influence of temperature and improves the agreement with the experimental data. Using a bilayer model, we study characteristic features of capacitance-potential dependence and relate them to the changes in interfacial structure. These insights are of fundamental and practical importance for the application of similar interfaces in electrochemical energy storage and transformation devices such as capacitors and actuators. (C) 2022 The Authors. Published by Elsevier B.V.

Abstract Atorvastatin (ATV) is a statin member consumed in high quantities worldwide. In response to that, the occurrence of ATV in environmental waters has become a reality, highlighting the need of rapid and sensitive analytical devices for its monitoring. In this work, the first electrochemical molecularly imprinted polymer (MIP) sensor for the detection of ATV in water samples is presented. Computational studies were conducted based on quantum mechanical (QM) calculations and molecular dynamics (MD) simulations for rational selection of a suitable functional monomer and to study in detail the templatemonomer interaction, respectively. The sensor was prepared by electropolymerisation of the selected 4aminobenzoic acid (ABA) monomer with ATV, acting as template, on screen printed carbon electrode (SPCE). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were applied to characterise the modified electrode surfaces. The quantitative measurements were carried out with differential pulse voltammetry (DPV) in 0.1 M phosphate buffer (pH = 7). After investigation and optimisation of important experimental parameters, a linear working range down to 0.05 mmol L-1 was determined with a correlation coefficient of 0.9996 and a limit of detection (LOD) as low as 0.049 mmol L-1 (S/N = 3). High sensitivity and selectivity of the prepared sensor were demonstrated with the ability to recognise ATV molecules over its closer structural analogues. Moreover, the sensor was quickly and successfully applied in spiked water samples, proving its potential for future on-site monitoring of ATV in environmental waters.

Abstract A novel molecularly imprinted polymer (MIP) has been developed based on a simple and sustainable strategy for the selective determination of citalopram (CTL) using screen-printed carbon electrodes (SPCEs). The MIP layer was prepared by electrochemical in situ polymerization of the 3-amino-4 hydroxybenzoic acid (AHBA) functional monomer and CTL as a template molecule. To simulate the polymerization mixture and predict the most suitable ratio between the template and functional monomer, computational studies, namely molecular dynamics (MD) simulations, were carried out. During the experimental preparation process, essential parameters controlling the performance of the MIP sensor, including CTL:AHBA concentration, number of polymerization cycles, and square wave voltammetry (SWV) frequency were investigated and optimized. The electrochemical characteristics of the prepared MIP sensor were evaluated by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Based on the optimal conditions, a linear electrochemical response of the sensor was obtained by SWV measurements from 0.1 to 1.25 mu mol L-1 with a limit of detection (LOD) of 0.162 mu mol L-1 (S/N = 3). Moreover, the MIP sensor revealed excellent CTL selectivity against very close analogues, as well as high imprinting factor of 22. Its applicability in spiked river water samples demonstrated its potential for adequate monitoring of CTL. This sensor offers a facile strategy to achieve portability while expressing a willingness to care for the environment.

Abstract The development of carbon dioxide (CO2) scavengers is an acute problem nowadays because of the global warming problem. Many groups around the globe intensively develop new greenhouse gas scavengers. Room-temperature ionic liquids (RTILs) are seen as a proper starting point to synthesize more environmentally friendly and high-performance sorbents. Aprotic heterocyclic anions (AHA) represent excellent agents for carbon capture and storage technologies. In the present work, we investigate RTILs in which both the weakly coordinating cation and AHA bind CO2. The ammonium-, phosphonium-, and sulfonium-based 2-cyanopyrrolidines were investigated using the state-of-the-art method to describe the thermochemistry of the CO2 fixation reactions. The infrared spectra and electronic and structural properties were simulated at the hybrid density functional level of theory to characterize the reactants and products of the chemisorption reactions. We conclude that the proposed CO2 capturing mechanism is thermodynamically allowed and discuss the difference between different families of RTILs. Quite unusually, the intramolecular electrostatic attraction plays an essential role in stabilizing the zwitterionic products of the CO2 chemisorption. The difference in chemisorption performance between the families of RTILs is linked to sterical hindrances and nucleophilicities of the alpha- and beta-carbon atoms of the aprotic cations. Our results rationalize previous experimental CO2 sorption measurements (Brennecke et al., 2021).

Abstract Deep eutectic solvents (DES) are an important class of green solvents that have been developed as an alternative to toxic solvents. However, the large-scale industrial application of DESs requires fine-tuning their physicochemical properties. Among others, surface tension is one of such properties that have to be considered while designing novel DESs. In this work, we present the results of a detailed evaluation of Quantitative Structure-Property Relationships (QSPR) modeling efforts designed to predict the surface tension of DESs, following the Organization for Economic Co-operation and Development (OECD) guidelines. The data set used comprises a large number of structurally diverse binary DESs and the models were built systematically through rigorous validation methods, including 'mixtures-out'- and 'compounds-out'-based data splitting. The most predictive individual QSPR model found is shown to be statistically robust, besides providing valuable information about the structural and physicochemical features responsible for the surface tension of DESs. Furthermore, the intelligent consensus prediction strategy applied to multiple predictive models led to consensus models with similar statistical robustness to the individual QSPR model. The benefits of the present work stand out also from its reproducibility since it relies on fully specified computational procedures and on publicly available tools. Finally, our results not only guide the future design and screening of novel DESs with a desirable surface tension but also lays out strategies for efficiently setting up silico-based models for binary mixtures.

Abstract The complex nature of electrode charge screening is well-known for ionic liquids (ILs). Due to strong ionion correlations, these electrolytes form a distinctive layered structure at interfaces. Variations in electrode potential cause structural changes that are reflected in a peculiar shape of differential capacitance-potential dependence with characteristic peaks. Although the differential capacitance for various ILs in conjunction with metal electrodes accessed via molecular dynamics (MD) simulations has been reported in the literature, retrieving a capacitance-potential curve, C(U), from the MD trajectories is not a trivial task. In this work, we present the results of the MD simulations of the IL 1-butyl-3-methylimidazolium hexafluorophosphate at a single-crystalline Au (100) surface. The discussion focuses on the simulation data treatment for C(U) curve fitting. It is shown that the resulting C strongly depends on the fitting method used. Four capacitance peaks and three structural reorganization types were identified in the studied system. With the help of a semi-quantitative approach in the framework of the original bilayer model of electric double layer (EDL), it is argued that the ions' reorientation is in the origin of the capacitance peaks. Also, it is shown that under the conditions of this study, the multilayer structure, characteristic of EDL in ILs on the whole, is far from the "lattice saturation" regime. The multilayer structure possesses a steric packing effect that impedes structural changes, decreasing the capacitance.

Abstract Deep eutectic solvents (DES) are often regarded as greener sustainable alternative solvents and are currently employed in many industrial applications on a large scale. Bearing in mind the industrial importance of DES-and because the vast majority of DES has yet to be synthesized-the development of cheminformatic models and tools efficiently profiling their density becomes essential. In this work, after rigorous validation, quantitative structure-property relationship (QSPR) models were proposed for use in estimating the density of a wide variety of DES. These models were based on a modelling dataset previously employed for constructing thermodynamic models for the same endpoint. The best QSPR models were robust and sound, performing well on an external validation set (set up with recently reported experimental density data of DES). Furthermore, the results revealed structural features that could play crucial roles in ruling DES density. Then, intelligent consensus prediction was employed to develop a consensus model with improved predictive accuracy. All models were derived using publicly available tools to facilitate easy reproducibility of the proposed methodology. Future work may involve setting up reliable, interpretable cheminformatic models for other thermodynamic properties of DES and guiding the design of these solvents for applications.</p>