Here we show that by adjusting the concentration of tetrabutyl ammonium and phosphonium salts in water (% 1.5-2.0 m), hydrophobic solvation triggers the formation of a unique, highly incompressible supramolecular liquid, with a dynamic structure similar to clathrates, involving essentially all H 2 O molecules of the solvent. Despite the increasing local order, the thermal diffusivity, and compressibility of these supramolecular liquids is strongly decreased with respect to bulk water due to slower relaxation dynamics. The results presented in this paper open an avenue to design a new family of supramolecular fluids, stable under atmospheric conditions, which can find important technological applications in energy storage and conversion. Dissolving small non (or moderate)-polar molecules in water induces the formation of local ice-like structures around them. [1-4] Above a certain concentration of the solute, and under conditions of high pressure and low temperature, these host-guest hydrates can form crystalline solids, so-called clathrate hydrates, a vast class of materials with important applications in gas separation, storage and transportation. [5-7] When the host molecule takes part within the multi-polyhedral structure of hydrogen-bonded water, semi-clathrate hydrates are formed. This is the case for tetrabutyl ammonium bromide (TtBABr) and other quaternary ammonium salts, in which the anions incorporate into

Nanostructured carbon materials with tailor-made structures (e.g., morphology, topological defect, dopant, and surface area) are of significant interest for a variety of applications. However, the preparation method selected for obtaining these tailor-made structures determines the area of application, precluding their use in other technological areas of interest. Currently, there is a lack of simple and low-cost methodologies versatile enough for obtaining freestanding carbon nanostructures that can be used in either energy storage or chemical detection. Here, a novel methodology for the development of a versatile electrochemically active platform based on freestanding graphite nanoplatelets (GNP) has been developed by exploiting the interiors of hollow carbon nanofibers (CNF) comprising nanographene stacks using dry ball-milling. Even though ballmilling could be considered as a universal method for any carbonaceous material, often, it is not as simple (one step, no purification, and no solvents), efficient (just GNP without tubular structures), and quick (just 20 min) as the sustainable method developed in this work, free of surfactants and stabilizer agents. We demonstrate that the freestanding GNP developed in this work (with an average thickness of 3.2 nm), due to the selective edge functionalization with the minimal disruption of the basal plane, can act either as a supercapacitor or as a chemical sensor, showing both a dramatic improvement in the charge storage ability of more than 30 times and an enhanced detection of electrochemically active molecules such as ascorbic acid with a 236 mV potential shift with respect to CNF in both cases. As shown here, GNP stand as an excellent versatile alternative compared to the standard commercially available carbon-based materials. Overall, our approach paves the way for the discovery of new nanocarbon-based electrochemical active platforms with a wide electrochemical applicability.

The dynamic structure of liquid water can be disrupted by the presence of non‐polar organic molecules, in a process known as hydrophobic solvation. Maria Giménez‐López, Francisco Rivadulla et al. demonstrate in their Communication on page 7540 that the particular orientation of hydrocarbon chains in tetraalkylammonium and phosphonium salts induces a peculiar structure of water molecules different from the bulk, changing its physicochemical properties.

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