Herein, we report on the ability to create complex 2-D and 3-D silica networks in vitro via polycationic peptide-mediated biosilicification under experimentally altered chemical and physical influences. These structures differ from the sphere-like silica network of particles obtained in vitro under static conditions. Under chemical influences, overall morphologies were observed to shift from a characteristic network of sphere-like silica particles to a sheetlike structure in the presence of -OH groups from additives and to sharp-edged, platelike structures in the presence of larger polycationic peptide matrixes. Under physical influences, using externally applied force fields, overall silica morphologies were observed to transition from sphere-like to fiberlike and dendrite-like structures. These findings could lead to the future development of bio-inspired complex 2-D and 3-D silica micro- and nano-devices.

The specific density and molar liquid volume of 40 imidazolium-based ionic liquids were predicted using the COSMO-RS method, a thermodynamic model based on quantum chemistry calculations. A molecular model of ion pairs was proposed to simulate the pure ionic liquid compounds. These ion-paired structures were generated at the B3LYP/6-31++G** computational level by combining the cations 1-methyl- (Mmim+), 1-ethyl- (Emim+), 1-butyl- (Bmim+), 1-hexyl- (Hxmim+), and 1-octyl-3-methylimidazolium (Omim+) with the anions chloride (Cl-), tetrafluoroborate (BF4 -), tetrachloroferrate (FeCl4 -), hexafluorophosphate (PF6 -), bis(trifluoromethanesulfonyl)imide (Tf2N-), methylsulfate (MeSO4 -), ethylsulfate (EtSO4 -), and trifluoromethanesulfonate (CF3SO3 -). Satisfactory agreement with the available experimental measurements was obtained, showing the capability of the current computational approach to describe the effect of the anion nature and cation substituent on the volumetric properties of this family of ionic liquids. Thus, calculated and experimental density values of ionic liquids (and also other common solvents) were fitted by linear regressions with correlation coefficients R > 0.99 and standard deviations SD < 20 kg/m3. Consequently, molar liquid volumes were also predicted very accurately by COSMO-RS, indicating the suitability of the ion-pair model to describe intermolecular interactions of pure ionic liquids. In this sense, the σ-profiles of the ion-paired molecules were used to qualitatively analyze the influence of cation and anion natures of ionic liquids on their volumetric properties. As a result of the analysis, we propose the charge distribution area below the σ-profile (S σ -profile) as a simple a priori parameter to characterize the contributions of cation and anion to the ionic liquid behavior as tool to design solvents.

The quantum chemical Conductor-like Screening Model for Real Solvents (COSMO-RS) method was evaluated as a theoretical framework to computationally investigate the application of room temperature ionic liquids (ILs) in absorptive technologies for capturing CO2 from power plant emissions to efficiently reduce both experimental efforts and time consumption. First, different molecular models to simulate ILs and computational methods in geometry calculations were investigated to optimize the COSMO-RS capability to predict Henry’s Law coefficients using a demanding solubility sample test with 35 gaseous solute-IL systems and 20 CO2−IL systems. The simulation results were in good agreement with experimental data, indicating that using an ion-pair molecular model optimized in a gas-phase environment allows a finer COSMO-RS description of the IL structure influence on the CO2 and other solutes solubilities. Moreover, the COSMO-RS methodology was used for the first time to achieve a deeper insight into the behavior of the solubility of CO2 in ILs from a molecular point of view. For this purpose, further analyses of the energetic intermolecular interactions between CO2 and ILs were performed by COSMO-RS, revealing that the van der Waals forces associated with the solute in the liquid phase determine the absorption capacity of CO2 in ILs, which is measured in terms of Henry’s Law coefficients. These findings were finally driven by a rational screening over 170 ILs with COSMO-RS to design new ILs that enhance CO2 capture by physical absorption.

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Heat capacity, glass-transition, crystallization, and melting temperatures of 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO 4 ]) and 1-butyl-3-methylimidazolium methylsulfate ([Bmim][MeSO 4 ]) ionic liquids (ILs) have been determined by differential scanning calorimetry (DSC). Their thermal stabilities have been analyzed by thermogravimetric analysis (TGA). Given the effect of the heating rate over the decomposition temperatures, isothermal TGA experiments are proposed as a more appropriate method to evaluate the thermal stability of the ILs. Inside the working range (-150 °C to 30 °C), [Emim][EtSO 4 ] and [Bmim][MeSO 4 ] present a glass-transition temperature of -78.4 °C and -91.9 °C, respectively. [Bmim][MeSO 4 ] has a melting temperature of -4.1 °C. The C p was determined in a working range (10 °C to 100 °C) where its value increases lineally with temperature.

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A thermogravimetric technique based on a magnetic suspension balance operating in dynamic mode was used to study the thermodynamics (in terms of solubility and Henry's law constants) and kinetics (i.e., diffusion coefficients) of CO2 in the ionic liquids [bmim][PF6], [bmim][NTf2], and [bmim][FAP] at temperatures of 298.15, 308.15, and 323.15 K and pressures up to 20 bar. The experimental technique employed was shown to be a fast, accurate, and low-solvent-consuming method to evaluate the suitability of the ionic liquids (ILs) to be used as CO2 absorbents. Thermodynamic results confirmed that the solubility of CO2 in the ILs followed the order [bmim][FAP] > [bmim][NTf2] > [bmim][PF6], increasing with decreasing temperatures and increasing pressures. Kinetic data showed that the diffusion coefficients of CO2 in the ILs followed a different order, [bmim][NTf2] > [bmim][FAP] > [bmim][PF6], increasing with increasing temperatures and pressures. These results evidenced the different influence of the IL structure and operating conditions on the solubility and absorption rate of CO2, illustrating the importance of considering both thermodynamic and kinetic aspects to select adequate ILs for CO2 absorption. On the other hand, the empirical Wilke-Chang correlation was successfully applied to estimate the diffusion coefficients of the systems, with results indicating the suitability of this approach to foresee the kinetic performance of ILs to absorb CO2. The research methodology proposed herein might be helpful in the selection of efficient absorption solvents based on ILs for postcombustion CO2 capture.

The performance of the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), and 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]) ionic liquids (ILs) as alternative solvents in the liquid–liquid extraction of toluene from heptane was evaluated at 313.2 K. These ILs were selected due to their low viscosity and their highly aromatic character. Densities and viscosities of the ILs have also been determined over the temperature range from 293.15 to 353.15 K. To analyze the potential of the ILs to be applied in an industrial aromatic extraction process, toluene and heptane distribution ratios, separation factors, and physical properties of the ILs have been compared to the sulfolane values. In addition, the nonrandom two-liquid model successfully correlated the liquid–liquid equilibrium data for the three ternary systems studied.