ABSTRACT
Within the most mesmerizing materials in the world of optoelectronics, mixed halide perovskites (MHPs) have been distinguished because of the tunability of their optoelectronic properties, balancing both the light-harvesting efficiency and the charge extraction into highly efficient solar devices. This feature has drawn the attention of analogous hot topics as photocatalysis for carrying out more efficiently the degradation of organic compounds. However, the photo-oxidation ability of perovskite depends not only on its excellent light-harvesting properties but also on the surface chemical environment provided during its synthesis. Accordingly, we studied the role of surface chemical states of MHP-based nanocrystals (NCs) synthesized by hot-injection (H-I) and anion-exchange (A-E) approaches on their photocatalytic (PC) activity for the oxidation of ß-naphthol as a model system. We concluded that iodide vacancies are the main surface chemical states that facilitate the formation of superoxide ions, O2â-, which are responsible for the PC activity in A-E-MHP. Conversely, the PC performance of H-I-MHP is related to the appropriate balance between band gap and a highly oxidizing valence band. This work offers new insights on the surface properties of MHP related to their catalytic activity in photochemical applications.
ABSTRACT
Se determinó el equilibrio líquido-líquido (ELL) de los sistemas ternarios benceno + (hexano, heptano y ciclohexano) con el líquido iónico 1-etil-3-metilimidazolio etilsulfato (EMIM-EtSO4) a 308,15 K; la selectividad (S) y el coeficiente de distribución (β) se calcularon desde los datos experimentales que se utilizaron para determinar la capacidad del líquido iónico como solvente para la separación del aromático desde sus mezclas con hidrocarburos alifáticos. La región de inmiscibilidad aumentó en el siguiente orden: ciclohexano < hexano < heptano. La consistencia de los datos experimentales del ELL es evaluado usando la ecuación de Othmer-Tobias. La composición de las fases en equilibrio se correlacionó con los modelos para coeficientes de actividad NRTL y Uniquac.
The equilibrium liquid-liquid (ELL) of ternary systems benzene + (hexane, heptane and cyclohexane) with the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate (EMIM-EtS0(4)) at 308.15 K, selectivity (S) and the distribution coefficient (β) are calculated from experimental data. The ability of ionic liquid as solvent for separation of the aromatic from their mixtures with ali-phatic hydrocarbons is analyzed. The region of immiscibility increased in the following order: cyclohexane < hexane < heptane. The consistency of the experimental data of ELL is evaluated using the equation of Othmer-Tobias. The composition of the phases in equilibrium is correlated with the models for the activity coeffcient NRTL and UNIQUAC.
O equilíbrio líquido-líquido (ELL) de los sistemas ternários benzeno + (hexa-no, heptano e ciclo-hexano) com o líquido iônico 1-etil-3-metilimidazólio etilsulfato (EMIM-EtS0(4)) com 308,15 K, seletividade (S) e o coeficiente de distribuição (β) são calculados a partir dos dados experimentais. Ela determina a capacidade de líquido iônico como solvente para a separação de aromático a partir de suas misturas com hidrocar-bonetos alifáticos. A região de imiscibilidade aumentou na seguinte ordem: ciclo-hexano < hexano < heptano. A consistência dos dados experimentais de ELL é avaliada usando a equação de Othmer-Tobias. A composição das fases de equilíbrio foi correlacionada com os modelos para coeficientes atividade NRTL e Uniquac.
ABSTRACT
The ionic mean activity coefficients of NaCl in trehalose-water and maltose-water mixtures have been experimentally determined at 298.15 K from emf measurements by electrochemical cell containing ion selective electrodes (ISE): Na-ISE/NaCl (m), sugar (Y%), H(2)O (100-Y%)/Cl-ISE. The electrolyte molality (m) ranged between 0.01 and 3 mol kg(-1), approximately, and the weight percent (Y%) of sugar in the mixture of solvents between 0, 10, 20, 30 and 40%. The system is considered as an electrolyte in a mixture of solvents and the data have been analysed by using the Debye-Hückel and Pitzer equations. The results obtained with both equations are in quite agreement with each other. The variation of the fit parameter from both equations were studied relative to the change in the dielectric properties of the mixture of solvents. Standard free energy of transference were comparatively discussed in terms of ion-solvent, ion-ion interactions and the hydration of both the electrolyte and the sugar.
