The ability to efficiently utilize solar thermal energy to enable liquid-to-vapor phase transition has great technological implications for a wide variety of applications, such as water treatment and chemical fractionation. Here, we demonstrate that functionalizing graphene using hydrophilic groups can greatly enhance the solar thermal steam generation efficiency. Our results show that specially functionalized graphene can improve the overall solar-to-vapor efficiency from 38% to 48% at one sun conditions compared to chemically reduced graphene oxide. Our experiments show that such an improvement is a surface effect mainly attributed to the more hydrophilic feature of functionalized graphene, which influences the water meniscus profile at the vapor-liquid interface due to capillary effect. This will lead to thinner water films close to the three-phase contact line, where the water surface temperature is higher since the resistance of thinner water film is smaller, leading to more efficient evaporation. This strategy of functionalizing graphene to make it more hydrophilic can be potentially integrated with the existing macroscopic heat isolation strategies to further improve the overall solar-to-vapor conversion efficiency.

We report the transformation of ionic liquid films from isotropic bulk to a fluid-ordered state over micrometer length scales. Data from infrared and nonlinear spectroscopy measurements show clear transitions that, for varying ionic liquids, occur over time frames of 10 min to 2 h. These maturation times depend linearly on the chosen ionic liquids' bulk viscosities. Interestingly, the ionic liquids do not form solids upon ordering but do exhibit strong preferential alignments of molecules that persist throughout the fluid films' thicknesses. Our measurements characterize this ordering process and show that it is largely insensitive to substrate surface chemistry or small amounts of absorbed water. Additional experiments show the transition is observed across several of the most common ionic liquid cations and that the process is completely reversible. The driving force for this organization is attributed to electrostatic and steric forces combined with a slow shearing of the viscous ionic liquid. These interactions work together to slowly bring the molecules within the film to a preferred, global orientation. The physical length and time scales of this transformation are unexpected and intriguing and invite additional studies to develop an understanding and control of ionic liquid materials' behavior, particularly near surfaces, to benefit their uses in lubrication, capacitive energy storage, and heterogeneous catalysis.

In situ infrared visible sum frequency generation spectroscopy (SFG) is used to examine the structure of water at the Ag-water interface in NaF and KF electrolyte solutions. Water is observed in environments associated with both the electrode surface and the diffuse double layer. Peaks are observed that are correlated with low-order water, water interacting with electrolyte ions, specifically adsorbed water to the electrode surface, and hydronium. Spectra obtained from a thiol-modified Ag surface enabled discrimination between surface-bound water and that in the double layer. The water organization is dependent on applied potential, with the observed intensities for specifically adsorbed and ion solvating water diminishing near the pzc.

The transport of anions across cellular membranes is an important biological function governed by specialised proteins. In recent years, many small molecules have emerged that mimick the anion transport behaviour of these proteins, but only a few of these synthetic molecules also display the gating/switching behaviour seen in biological systems. A small series of thiosquaramides was synthesised and their pH-dependent chloride binding and anion transport behaviour was investigated using 1H NMR titrations, single crystal X-ray diffraction and a variety of vesicle-based techniques. Spectrophotometric titrations and DFT calculations revealed that the thiosquaramides are significantly more acidic than their oxosquaramide analogues, with pKa values between 4.0 and 9.0. This led to the observation that at pH 7.2 the anion transport ability of the thiosquaramides is fully switched OFF due to deprotonation of the receptor, but is completely switched ON at lower pH.

A macrocyclic tetralactam host is threaded by a highly fluorescent squaraine dye that is flanked by two polyethyleneglycol (PEG) chains with nanomolar dissociation constants in water. Furthermore, the rates of bimolecular association are very fast with kon ~106–107 M−1s−1. The association is effective under cell culture conditions and produces large changes in dye optical properties including turn-on near-infrared fluorescence that can be imaged using cell microscopy. Association constants in water are ~1000 times higher than in organic solvents and strongly enthalpically favored at 27 °C. The threading rate is hardly affected by the length of the PEG chains that flank the squaraine dye. For example, macrocyle threading by a dye conjugate with two appended PEG2000 chains is only three times slower than threading by a conjugate with triethyleneglycol chains that are twenty times shorter. The results are a promising advance towards synthetic mimics of streptavidin/biotin.