Publications

Abstract This work investigates the potential of betaine as a substitute for choline chloride in the formation of polyol-based DES. The solid-liquid equilibrium (SLE) phase diagrams of binary mixtures of betaine with one polyol (ethylene glycol, 1,3-propanediol, glycerol, meso-erythritol, xylitol, or sorbitol) were studied across the entire composition range. Experimental measurements of the phase diagrams were limited by the thermal degradation of betaine and by the boiling points or high viscosities of some polyols. Overall, betaine exhibited negative deviations from ideality, while most polyols displayed near-ideal behaviour. COSMO-RS, a thermodynamic model, satisfactorily predicts these deviations from ideality and the observed phase behaviour. Mixtures of betaine and polyols yielded a narrower liquid-phase window for room-temperature applications than the corresponding choline chloride systems. The cross-association of betaine with polyols is more favourable than its self-association, and stronger interactions between the polyols and betaine than with choline chloride are expected, leading to more negative deviations; thus, the smaller melting temperature depression must result from a higher enthalpy of fusion of betaine than that of choline chloride.

Abstract The biphasic transfer of Eu(NO3)3 by trioctylphosphine oxide (TOPO) diluted in a molecular diluent or as a component of a hydrophobic eutectic solvent (HES) was studied by two-phase isothermal titration calorimetry and complemented by XAS, FTIR, and NMR spectroscopy. In HES, the solvent intermolecular interactions introduce an enthalpic penalty, which is overcompensated by a reduction of the entropic cost of Eu(III) phase transfer, resulting in enhanced metal partitioning.

Abstract A comprehensive thermodynamic and supramolecular characterization was conducted on a series of phenanthroline-based organic semiconductors and related derivatives, including 1,10-phenanthroline (PHEN), neocuproine (DMPHEN), bathophenanthroline (BPHEN), and bathocuproine (BCP), to elucidate how systematic molecular substitution affects their stability, volatility, and optoelectronic properties. Heat capacity and phase-transition studies, including vapor-pressure measurements, provided a consistent thermodynamic framework for these materials. Analysis of heat capacities revealed that methyl and phenyl groups contribute independently and additively, supporting transferable models for predicting thermal behavior. Thermogravimetric analysis showed that phenyl substitution enhances thermal stability (BPHEN, BCP), whereas methyl substitution slightly decreases it. Differential scanning calorimetry revealed distinct phase behaviors: PHEN is sensitive to hydration, DMPHEN exhibits polymorphism, BPHEN tends to form a glass, and BCP crystallizes reproducibly. Sublimation studies using Knudsen effusion coupled with a quartz crystal microbalance yielded enthalpic and entropic parameters clarifying volatility trends. Complementary supramolecular analysis identified the key pi-pi stacking, C-H & centerdot;& centerdot;& centerdot;N and C-H & centerdot;& centerdot;& centerdot;pi interactions underlying crystal cohesion. UV-vis spectroscopy further provided the band gap energies, which are relevant to optoelectronic performance. By correlating thermodynamic data with supramolecular organization and molecular structure, this study establishes a rigorous framework for the rational design and processing of phenanthroline derivatives in robust and efficient organic electronic devices.

Abstract A systematic investigation of thin films of pyridinium-based ionic liquids (ILs), [C n py][NTf2] (n = 2-9), deposited via physical vapor deposition on ITO and Au/ITO substrates is presented, providing the first comprehensive study of vacuum-deposited films within this homologous series. The influence of evaporation temperature, deposition rate, alkyl chain length, and substrate on thin-film morphology, nucleation and coalescence dynamics, interfacial behavior, and film structure was examined using SEM, optical microscopy, FTIR, and XPS. SEM analyses reveal that higher evaporation temperatures, which increase the deposition rate, lead to larger droplets and enhanced coalescence, resulting in larger microstructures. A comparison of the film morphologies across the IL series shows that longer cation alkyl chains further enhance lateral spreading and wetting, particularly on Au substrates. An odd-even effect on the morphological characteristics of the films is observed across the series, reflecting subtle differences in interfacial interactions. Moreover, a clear distinction in wetting behavior between short- and long-chain pyridinium ILs is evident, consistent with trends previously reported for imidazolium-based ILs. FTIR spectra comparing bulk and thin IL films confirm that the ILs retain their chemical integrity upon film formation. XPS measurements support the morphological observations, highlighting that ILs comprising longer alkyl chains achieve more complete surface coverage. The results of this work provide fundamental insights into the interplay between the cation alkyl chain length of pyridinium-based ILs, substrate interactions, and film formation dynamics, offering guidance for the rational design of IL films for functional surface applications.

Abstract The purpose of this article is to present and discuss a historical house project that was transposed into virtual reality, to be preserved as digital cultural heritage. The Matosinhos House, in Portugal, is part of a residential project designed by the architect Alvaro Siza Vieira in 1955-56, is the historical house that was chosen as case study. The article displays the historical significance of the project, as well as the method applied to transpose it into virtual reality. The goal is to promote access to digital cultural heritage based on reliable and accurate interpretation of the collected data.

Abstract The effect of the anion on the electrical conductivity of ionic liquids was explored by a high-precision study of the temperature dependence (283–333 K) of the electrical conductivity of ten ILs based on the 1-butyl-3-methylimidazolium cation, [C4C1im]+. The following trend was observed for the molar conductivity at the reference temperature of 298.15 K: Ac < PF6− < BETI < OTf < TFA < BF4− < FAP < NTf2 < FSI < DCA. The molar conductivity at infinite temperature, AΛ, and the energy barrier, EΛ, derived from the Vogel–Fulcher–Tammann equation (VFT) fitting were found to correlate well with the shape/size/dynamics and cohesive energy/charge localization of the studied ions. An extensive revision and comparison with the available experimental electrical conductivity data for the studied ionic liquids is also presented. Additionally, this work presents a detailed description, testing, and evaluation of performance results of a new system/methodology for the high-precision measurement of the electrical conductivity of ionic fluids, designed to minimize the size of the ionic liquid sample and in situ degassing of the sample. The measuring system is based on a high-precision LCR meter and a conductivity cell system designed to ensure the vacuum and gastightness of the sample container. The high-precision temperature control is ensured by a customized thermal chamber based on a heating and cooling Peltier system. The electrical conductivity data were corrected for the effect of solution polarization by extrapolating the resistance to infinite frequency. The accuracy and resolution of the system were evaluated by measuring the conductivity of the reference ionic liquid, [C6C1im][NTf2] which was found to be in excellent agreement with the recommended data. © 2025 The Author(s)

Abstract This study demonstrates the efficacy of ionic liquid (IL)-assisted vapor deposition in achieving high-quality and distinctive crystal film growth of two organic semiconductors (OSCs): a carbazole derivative (TCB) and a phenylamine derivative (TDAB). ILs with different wetting properties (short-chain [C2C1im][NTf2] and long-chain [C8C1im][NTf2]) and engineered shapes (microdroplets and coalesced film) were utilized as solvents in a vacuum. Through a meticulously designed experimental strategy, encompassing both sequential and simultaneous deposition of the IL and the OSC, this study unveils the pivotal role of ILs in shaping the crystallization behavior of the organic compound. Differential scanning calorimetry, polarized light microscopy, high-resolution scanning electron microscopy, and X-ray diffraction were employed for the films' thermal, morphological, and structural characterization. Thin films of TDAB exhibit crystallinity and a greater tendency to grow tridimensionally, forming giant pillars. However, the typical vertical growth of TDAB on solid substrates is altered when deposition occurs on surfaces coated with ILs. The IL promotes the lateral growth of nanostructures. The experimental results reveal variations in film morphology and coverage influenced by the cation alkyl chain length of the IL. In contrast to TDAB, TCB films are amorphous when thermally evaporated on solid substrates. Notably, IL-assisted vapor deposition induces the crystallization of TCB. Furthermore, TCB films deposited on coalesced IL films exhibit enhanced crystallinity and homogeneous horizontal growth, representing a significant finding in the context of thin film deposition and semiconductor device fabrication.

Abstract Extensive research has focused on films formed by pure ionic liquids (ILs). However, growing interest in IL mixtures and their synergistic properties presents new opportunities for targeted applications and fundamental scientific investigations. This study explores the morphology of films composed of mixtures of two ILs, [C2C1im][OTf] and [C8C1im][OTf], co-deposited via physical vapor deposition (PVD)/vacuum thermal evaporation. The primary objective was understanding how varying the IL ratio influences droplet formation, surface coverage, and overall film structure. Thin-film growth was examined on glass substrates coated with indium tin oxide (ITO) and ITO/glass surfaces coated with metallic films (Au and Ag). Film morphology was characterized using optical and high-resolution scanning electron microscopy (SEM), while elemental composition was analyzed via X-ray photoelectron spectroscopy (XPS). The results show that IL mixture morphology is strongly influenced by both IL composition and substrate type. Increasing [C8C1im][OTf] content led to larger microstructures due to improved wetting, particularly on Au surfaces, resulting in nearly fully coalesced films. Metallic surfaces near ITO significantly impacted droplet behavior, with ILs exhibiting a strong affinity for metals, especially when the long-chain IL dominated the mixture. The IL-assisted crystallization of rubrene, a high-performance organic semiconductor (OSC) that typically exhibits poor crystallinity when deposited via PVD, highlights the potential of IL mixtures to enhance organic film quality. X-ray diffraction (XRD) confirmed that [C2C1im][OTf] and [C8C1im][OTf] mixtures significantly improved rubrene crystallinity, demonstrating their potential to create an optimal environment for OSC solubility and crystallization.

Abstract The impact of nanostructuration on the transport properties of ionic liquids (ILs) was explored by a systematic and high-resolution study of the temperature dependence of the viscosity and electrical conductivity of seven ILs homolog series: [C(n)C(1)im]BF4, [C(n)C(1)im]PF6, [C(n)C(1)im][OTf], [C(n)C(1)im][FAP], [C(n)C(1)im][NTf2], [CnC(1)pyr][NTf2], [Cnpy][NTf2]. The increase of the alkyl chain length was found to increase the viscosity and decrease the molar conductivity due to a reduction of the overall mobility of the liquid and enhancement of the van der Waals interactions. The temperature dependency of transport properties was fitted to the Vogel-Fulcher-Tammann equation (VFT), and the energy barrier and pre-exponential coefficients were derived. The obtained results highlight the trendshift (n = 6-7) in the profile of the transport properties, which is a reflection of the intensification of nanostructuration and describes the transition from a liquid with a strong ionic character to a nanostructured liquid dominated by the hydrophobic domain. The derived energy barriers were found to correspond to around 0.2-0.35 of the cohesive interactions of the ionic liquids, with the spherical anions BF4- and PF6- showing a higher fraction than the more stretched and larger anions, such as NTf2. This fraction was found to not be affected by the alkyl chain length. The increase of the nonpolar region was also reflected in a more pronounced deviation from the ideal Walden relation. This highlights the increased complexity of the electric conductivity when compared with viscosity due to the heterogeneity of charge distribution, revealing the impact of ionic surface-volume ratio and anion-cation size ratio.

Abstract Thin films of ionic liquids (ILs) have gained significant attention due to their unique properties and broad applications. Extensive research has focused on studying the influence of ILs' chemical composition and substrate characteristics on the structure and morphology of IL films at the nano- and mesoscopic scales. This study explores the impact of carbon-coated surfaces on the morphology and wetting behavior of a series of alkylimidazolium-based ILs. Specifically, this work investigates the effect of carbon coating on the morphology and wetting behavior of short-chain ([C(2)C(1)im][NTf2] and [C(2)C(1)im][OTf]) and long-chain ([C(8)C(1)im][NTf2] and [C(8)C(1)im][OTf]) ILs deposited on indium tin oxide (ITO), silver (Ag), and gold (Au) substrates. A reproducible vapor deposition methodology was utilized for the deposition process. High-resolution scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to analyze the morphological and structural characteristics of the substrates and obtained IL films. The experimental data revealed that the IL films deposited on carbon-coated Au substrates showed minor changes in their morphology compared to that of the films deposited on clean Au surfaces. However, the presence of carbon coatings on the ITO and Ag surfaces led to significant morphological alterations in the IL films. Specifically, for short-chain ILs, the carbon film surface induced 2D growth of the IL film, followed by subsequent island growth. In contrast, for long-chain ILs deposited on carbon surfaces, layer-by-layer growth occurred without island formation, resulting in highly uniform and coalesced IL films. The extent of morphological changes observed in the IL films was found to be influenced by two crucial factors: the thickness of the carbon film on the substrate surface and the amount of IL deposition.