Hydrophobic hydration is considered to have a key role in biological processes ranging from membrane formation to protein folding and ligand binding. Historically, hydrophobic hydration shells were thought to resemble solid clathrate hydrates, with solutes surrounded by polyhedral cages composed of tetrahedrally hydrogen-bonded water molecules. But more recent experimental and theoretical studies have challenged this view and emphasized the importance of the length scales involved. Here we report combined polarized, isotopic and temperature-dependent Raman scattering measurements with multivariate curve resolution (Raman-MCR) that explore hydrophobic hydration by mapping the vibrational spectroscopic features arising from the hydrophobic hydration shells of linear alcohols ranging from methanol to heptanol. Our data, covering the entire 0-100 °C temperature range, show clear evidence that at low temperatures the hydration shells have a hydrophobically enhanced water structure with greater tetrahedral order and fewer weak hydrogen bonds than the surrounding bulk water. This structure disappears with increasing temperature and is then, for hydrophobic chains longer than ~1 nm, replaced by a more disordered structure with weaker hydrogen bonds than bulk water. These observations support our current understanding of hydrophobic hydration, including the thermally induced water structural transformation that is suggestive of the hydrophobic crossover predicted to occur at lengths of ~1 nm (refs 5, 9, 10, 14).

SBA-16 mesoporous silicas with cubic Im3m structure were synthesized using Pluronic F127 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (EO 106 PO 70 EO 106 ) and its blends with Pluronic P123 triblock copolymer (EO 20 PO 70 EO 20 ) as supramolecular templates. The resulting materials were characterized using X-ray diffraction, transmission electron microscopy, and argon and nitrogen adsorption. Selected samples were also modified with series of organosilanes of gradually increasing sizes and the accessibility of the pore structure after the modification was assessed using argon adsorption, which allowed us to determine the diameter of entrances to the ordered mesopores. It was shown that the pore cage diameter in SBA-16 can be enlarged in a wide range not only by increasing the synthesis temperature and time, as previously known, but also by increasing the content of P123 copolymer in the polymer mixture. These three ways allowed us to synthesize SBA-16 with nominal mesopore diameters from ∼4.5 to 9 nm. Even more importantly, they were also suitable for the tailoring of the pore entrance diameter from ∼1 to at least 6 nm, although in this case, the effect of the copolymer mixture composition on the entrance size was relatively small. In the case of SBA-16 samples synthesized at low temperatures or short hydrothermal treatment times, there was evidence that the pore entrance size was as low as 0.4-0.7 nm, as argon atoms were capable of entering the pore structure, but trimethylchlorosilane appeared to be largely excluded from it. By varying the synthesis temperature, time, and template composition, SBA-16 samples with essentially the same mesopore cage diameter and with largely different pore entrance sizes were synthesized. The present work is a step forward in the synthesis of a mesoporous molecular sieve with independently tailored mesopore diameter and entrance size.

The unique structural, dynamical and chemical properties of air/water and oil/water interfaces are thought to play a key role in various biological, geological and environmental processes. For example, non-hydrogen-bonded ('dangling') OH groups--which create surface defects in water's hydrogen bonding network and are experimentally detected at both macroscopic (air/water or oil/water) and microscopic (dissolved hydrophobic molecule) interfaces--are thought to catalyse some chemical reactions. However, how the size, curvature or charge of the exposed hydrophobic surface influences water's propensity to form dangling OH defects has not yet been established quantitatively. Here we use Raman multivariate curve resolution to probe spectroscopically the hydrophobic hydration shell and, using a statistical multisite analysis, we show that such interfacial dangling OH structures are entropically stabilized and their formation is cooperative (the probability that a non-hydrogen-bonded OH group will form depends nonlinearly on the hydrophobic surface area). We thus expose an important difference between the chemical properties of molecular and macroscopic oil/water interfaces.

Experimental MethodsRaman Spectral Measurements: Raman spectra were obtained using a home-built, micro-Raman system similar to that used in previous studies (1). The system used in the present studies includes an Ar-Ion laser source (514.5nm, ~ 50 mW power at the sample) and a thermoelectrically cooled CCD detector (Princeton Instruments Inc., Pixis 400, 1340x400 pixel) mounted to a 300 mm focal length imaging spectrograph (SpectraPro300i, Acton Research Inc.), with a 300 g/mm grating, such that the dispersion is approximately 5 cm -1 per CCD pixel. Liquid samples were analyzed in spectroscopic 1 cm glass cuvettes contained within a thermoelectric, temperature-controlled, translating cell holder (Quantum Northwest). The solution temperature was controlled to within ± 0.01 °C over a 0°C to 60°C temperature range. Such temperature control was required in order to avoid spurious spectral features in the solute-correlated (SC) spectra resulting from small differences in temperature between the solution and pure water samples. A helium lamp was placed behind the sample so that two He lines at 587.562 nm and 667.815 nm were visible in each Raman spectrum (on either side of the OH stretch band). The He lines were used to correct for small wavelength drifts (resulting from small changes in ambient temperature and pressure) which, if uncorrected, would also produce spurious features in the SC spectra within the OH stretch band. The frequency shifts were corrected by introducing a sub-pixel shift the wavelength axis of the solution spectra so as to precisely match the He peak positions in the solution and pure water spectra. The latter shifts were performed using IgorPro (Wavemetrics Inc.) which facilitates duplication of waves with sub-pixel shifts, using a command such as wave1=wave0(p+d), where p is the pixel number (variable) d is a real constant whose magnitude is typically less than 0.1, and wave1 and wave0 are the shifted and un-shifted solution spectra, respectively.Benzene: Spectrophotometry grade benzene (99.93 % assay, EMD Chemicals Inc., Germany) was used without further purification. Water was ultra-purified (Milli-Q UF plus, Millipore Inc.) to an electrical resistance of 18.2 MΩ •cm. Saturated benzene in water was prepared by thoroughly stirring a sample consisting of water with a small excess benzene for 5 min. The solution was then allowed to equilibrate at the desired temperature for at least one day (in equilibrium with the excess benzene phase). Raman spectra were collected from the aqueous phase of the resulting solution (with an excess benzene layer at the top) as well as from a pure water sample (at the same temperature). All samples were equilibrated for at least 5 min in the temperature controlled sample cell holder, and measurements were made in the same cell position. Total (un-polarized) Raman scattering spectra of each solution of benzene in water

A highly graphitized ordered nanoporous carbon (ONC) was synthesized by using commercial mesophase pitch as carbon precursor and siliceous colloidal crystal as template. Since silica colloids of different sizes (above 6 nm) and narrow particle size distribution are commercially available, the pore size tailoring in the resulting ONCs is possible.

The structure of ordered mesoporous carbons (OMC) synthesized with sucrose, furfuryl alcohol or acenaphthene using the SBA-16 mesoporous silica template with cubic Im3 ¯m structure has been investigated with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N 2 adsorption. This work shows that, in contrast to carbons prepared from sucrose by using SBA-15 silica as template, the impregnation of SBA-16 with sucrose failed to produce OMC with cubic Im3 ¯m structure. However, when furfuryl alcohol and acenaphthene were used as carbon precursors, the cubic Im3 ¯m structure was retained in the products. Thus, the latter carbon precursors were more suitable than sucrose for the formation of rigidly interconnected carbon bridges through narrow apertures of the cage-like siliceous SBA-16 mesostructure. In particular, the use of furfuryl alcohol as carbon precursor allowed us to control the degree of mesopore filling in SBA-16 and consequently, to synthesize hollow or fully filled cage-like silica-carbon mesostructures as was done in the case of channel-like SBA-15. In the case of acenaphthene only fully filled mesostructures were formed but with a much higher degree of graphitization. In the present work, we took advantage of the recent developments in the synthesis of SBA-16 with tailored diameter and entrance size of mesopores and made a step forward in the fabrication of OMC by using cage-like mesoporous silicas with narrow interconnections as templates.{ Electronic supplementary information (ESI) available: Fig. 1S, 4S, and 5S showing N 2 adsorption-desorption isotherms for the SBA-16/ carbon composites, the recovered SBA-16 samples obtained from the composites, and the carbon samples, respectively; Fig. 2S and 3S showing XRD patterns for the C FA1 -t carbons and the recovered SBA-16 samples obtained from the composites. See

Mesoporous carbons with extremely large pore volume ( approximately 6 cm3/g) and narrow bimodal pore size distribution were synthesized by using 24 nm silica colloids as template.

The general consensus in the studies of nanostructured carbon catalysts for oxidative dehydrogenation (ODH) of alkanes to olefins is that the oxygen functionalities generated during synthesis and reaction are responsible for the catalytic activity of these nanostructured carbons. Identification of the highly active oxygen functionalities would enable engineering of nanocarbons for ODH of alkanes. Few-layered graphenes were used as model catalysts in experiments to synthesize reduced graphene oxide samples with varying oxygen concentrations, to characterize oxygen functionalities, and to measure the activation energies for ODH of isobutane. Periodic density functional theory calculations were performed on graphene nanoribbon models with a variety of oxygen functionalities at the edges to calculate their thermal stability and to model reaction mechanisms for ODH of isobutane. Comparing measured and calculated thermal stability and activation energies leads to the conclusion that dicarbonyls at the zigzag edges and quinones at armchair edges are appropriately balanced for high activity, relative to other model functionalities considered herein. In the ODH of isobutane, both dehydrogenation and regeneration of catalytic sites are relevant at the dicarbonyls, whereas regeneration is facile compared with dehydrogenation at quinones. The catalytic mechanism involves weakly adsorbed isobutane reducing functional oxygen and leaving as isobutene, and O2 in the feed, weakly adsorbed on the hydrogenated functionality, reacting with that hydrogen and regenerating the catalytic sites.