Despite prolonged scientific efforts to unravel the hydration structures of ions in water, many open questions remain, in particular concerning the existences and structures of ion clusters in 1∶1 strong electrolyte aqueous solutions. A combined ultrafast 2D IR and pump/probe study through vibrational energy transfers directly observes ion clustering in aqueous solutions of LiSCN, NaSCN, KSCN and CsSCN. In a near saturated KSCN aqueous solution (water/KSCN molar ratio ¼ 2.4∕1), 95% of the anions form ion clusters. Diluting the solution results in fewer, smaller, and tighter clusters. Cations have significant effects on cluster formation. A small cation results in smaller and fewer clusters. The vibrational energy transfer method holds promise for studying a wide variety of other fast short-range molecular interactions.T he solution properties of ions in water are relevant to a wide range of systems, including electrochemistry, biological environments, and atmospheric aerosols (1, 2). For more than 100 yr, tremendous scientific efforts have been devoted to unravel the hydration structures of ions in water (1-11). However, many fundamental questions remain open, in particular concerning the existence, concentration, and structure of ion clusters in 1∶1 strong electrolyte aqueous solutions. Whether strong 1∶1 electrolytes (especially salts of Na þ and K þ ) form ion pairs or clusters in water has been considered a key issue for understanding many important problems, e.g., the excess ionic activity in 1∶1 electrolytes (12), ion dependent conformational and binding equilibria of nucleic acids (13), the concentration difference between Na þ and K þ in living cells, protein denaturation by salts (14, 15), and ion concentration dependent properties of ion channels (16).The properties of aqueous solutions of 1∶1 strong electrolytes deviate from the ideal dilute solution at extremely low concentrations (<10 −5 M). The deviations were generally believed to be caused by the attraction between ions of opposite charge and the repulsion of ions of the same charge, leading to the development of the Debye-Hückel theory (17, 18). However, this theory begins to fail at a very low concentration (∼10 −3 M), as the assumptions upon which the theory was based become invalid. The formation of ion pairs containing two ions of opposite charge has been proposed to be primarily responsible for this failure (1, 2). Recently, calculations from molecular dynamics (MD) simulations, suggested that, clusters with more than one ion of the same charge which are traditionally viewed as unlikely, could be a major factor contributing to the nonideality of solutions at medium or high concentrations (12,19). However, these predicted ion clusters cannot be investigated by the usual tools for probing molecular structures and particle sizes in liquids, e.g., X-ray or neutron diffraction (20), or the dynamic light scattering (19,21), because the contribution of ion-ion correlations to the total scattering pattern is too small compared to the contributions ...

Pt-like electrocatalytic activity of MoN, WN, and Fe 2 N for dyesensitized solar cells (DSSCs) is demonstrated in this work. Among the transition metal nitrides, MoN has superior electrocatalytic activity and a higher photovoltaic performance. This work presents a new approach for developing low-cost and highly-efficient counter electrodes for DSSCs.

No abstract

The multiple-mode two-dimensional infrared (2D-IR) spectrum in a broad frequency range from 1000 to 3200 cm−1 of a 1-cyanovinyl acetate solution in CCl4 is reported. By analyzing its relative orientations of the transition dipole moments of normal modes that cover vibrations of all chemical bonds, the three-dimensional molecular conformations and their population distributions of 1-cyanovinyl acetate are obtained, with the aid of quantum chemistry calculations that translate the experimental transition dipole moment cross angles into the cross angles among chemical bonds.