Understanding the molecular structure of water at solid–liquid interfaces is essential for advancing catalysis, energy conversion, and environmental technologies. However, directly characterizing interfacial water species in excess liquid water remains a major experimental challenge. Here, we introduce a new strategy that combines high-resolution 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy with first-principles molecular dynamics simulations to resolve and assign the chemical environments of interfacial water and hydroxyl species on hydrated titanium dioxide (TiO2) nanoparticles. Using partial proton–deuteron exchange and fast MAS techniques, we achieve site-specific detection of surface-bound H2O and OH groups at the solid–liquid interface. This enables a detailed atomistic assessment of surface hydration states under ambient conditions. Our results reveal that the fully hydrated anatase (101) TiO2 surfaces are positively protonated and exhibit hydrophobic behavior, a counterintuitive finding with significant implications for interfacial reactivity. The approach developed in this work is widely applicable for unraveling complex hydration structures at oxide–water interfaces with molecular resolution.

TiO2-II is a high pressure form of titania with a density about 2% larger than that of rutile. In contrast to the common polymorphs anatase, brookite and rutile its electronic structure and optical properties are poorly characterized. Here we report on a comparative electron-energy-loss-spectroscopy (EELS) study for which high resolution valence-loss and core-loss EELS data were acquired from nanocrystalline (<75 nm sized) titania particles with an energy resolution of about 0.2 eV. Electronic structure features revealed from titanium L3,2 and oxygen K electron energy loss near-edge structures show a strong similarity of TiO2-II with both rutile and brookite, which is attributed to similarities in the connectivity of octahedral TiO6 units with neighboring ones. From combined valence-loss EELS and UV-VIS diffuse reflectance spectroscopy data the band gap of TiO2-II was determined to be indirect and with a magnitude of-3.18 eV, which is very similar to anatase (indirect,-3.2 eV), and distinctly different from rutile (direct,-3.05 eV) and brookite (direct,-3.45 eV).

A multianvil cell assembly with octahedral edge length 25 mm has been adapted for high pressure investigations involving water-rich environments up to 6.5 GPa and 400 & DEG;C. Water-rich samples are confined in Teflon containers with a volume up to 300 mm(3). Applicability tests were performed between 250 and 400 & DEG;C by investigating the transformation of amorphous titania particles close to the rutile-TiO2-II (& SIM;5 GPa) phase boundary, and the transformation of amorphous silica particles close to the quartz-coesite (& SIM;2.5 GPa) and coesite-stishovite (& SIM;7 GPa) phase boundaries. The performed experiments employed 25.4 mm tungsten carbide anvils with a truncation edge length of 15 mm. The sample pressure at loads approaching 820 t was estimated to be around 6.5 GPa. The large volume multianvil cell is expected to have broad and varied application areas, ranging from the simulation of geofluids to hydrothermal synthesis and conversion/crystal growth in aqueous environments at gigapascal pressures.

Cellulose fibrils are the structural backbone of plants and, if carefully liberated from biomass, a promising building block for a bio-based society. The mechanism of the mechanical release─fibrillation─is not yet understood, which hinders efficient production with the required reliable quality. One promising process for fine fibrillation and total fibrillation of cellulose is cavitation. In this study, we investigate the cavitation treatment of dissolving, enzymatically pretreated, and derivatized (TEMPO oxidized and carboxymethylated) cellulose fiber pulp by hydrodynamic and acoustic (i.e., sonication) cavitation. The derivatized fibers exhibited significant damage from the cavitation treatment, and sonication efficiently fibrillated the fibers into nanocellulose with an elementary fibril thickness. The breakage of cellulose fibers and fibrils depends on the number of cavitation treatment events. In assessing the damage to the fiber, we presume that microstreaming in the vicinity of imploding cavities breaks the fiber into fibrils, most likely by bending. A simple model showed the correlation between the fibrillation of the carboxymethylated cellulose (CMCe) fibers, the sonication power and time, and the relative size of the active zone below the sonication horn.

Stable binary icosahedral quasicrystals (i-QCs) based on rare earth (RE) and cadmium are typically accessed by solution growth experiments, which operate in very narrow composition and temperature windows. Here, we present a procedure which allows study of peritectic reactions between approximant crystal (AC) phase and liquid yielding i-RECd and exemplify with i-GdCd and ternary variants where Cd is partially replaced by isovalent Zn (i-Gd(Cd,Zn)) or Mg (i-Gd(Cd,Mg)), or the 4f element Gd is replaced by nonmagnetic Y (i-(Gd,Y)Cd). The solubility limits for Zn and Mg substitution are about 10% and 20%, respectively, whereas Gd and Y show a complete solid solution behavior. We find that the peritectic decomposition temperature for i-GdCd is 390 degrees C, which is decreased when Gd is replaced by Y (i-YCd: 350 degrees C) and increased when Cd is replaced by Zn (i-Gd(Cd90Zn10): 440 degrees C), and especially by Mg (i-Gd(Cd80Mg20): 520 degrees C). Whereas substitution decisively alters the decomposition temperature (and hence stability) of the considered i-QCs, the decomposition temperature of the corresponding AC phases remains at around 700 degrees C. During the investigation of the pseudobinary phase diagrams Gd-(Cd95Zn5), Gd-(Cd90Zn10), and Gd-(Cd(80M)g(20)), faceted i-QCs grains with sizes up to 4 x 4 x 4 mm(3) could be isolated.

LiAlSiO3(OH)2 is a dense hydrous aluminosilicate which is formed from LiAlSiO4 glass in hydrothermal environments at pressures around 5 GPa. The OH groups are part of the octahedral Al and Li coordination. We studied the dehydration behavior of LiAlSiO3(OH)2 by a combination of TEM and multi-temperature PXRD experiments. Dehydration takes place in the temperature interval 350–400 °C. Above 700 °C LiAlSiO3(OH)2 is converted via a transient and possibly still slightly hydrous phase into γ-eucryptite which is a metastable and rarely observed polymorph of LiAlSiO4. Its monoclinic structure is built from corner-sharing LiO4, AlO4 and SiO4 tetrahedra. The ordered framework of AlO4 and SiO4 tetrahedra is topologically equivalent to that of cristobalite.

A new method for stirring under high pressure conditions has been developed and tested. The key component is a Teflon cell assembly equipped with magnetic stirring function, which is capable to operate across a wide pressure range, up to at least 2 GPa, in a large volume press. The setup enables adjustable stirrer rotation rate and detection of stirring in a sample,e.g.to observe liquid-solid phase transitions at high pressure. The viscosity limit of stirring is ca. 500 times that of water at room temperature (i.e.similar to 500 mPas). Moreover, we show that zinc oxide nanoparticles hydrothermally synthesized at 0.5 GPa and 100 degrees C under stirring conditions show an order of magnitude smaller size (100 nm) compared to those synthesized under non-stirring conditions (1 mu m). The wide pressure range for stirring of viscous media opens interesting possibilities to produce novel materials via hydrothermal synthesis and chemical reactions.

Layered zinc hydroxides (LZHs) with the general formula (Zn2+)(x)(OH-)(2x-my ),(A(m-))(y)center dot nH(2)O (A(m-) = Cl- , NO3- , ac(-) , SO42-, etc) are considered as useful precursors for the fabrication of functional ZnO nanostructures. Here, we report the synthesis and structure characterization of the hitherto unknown binary representative of the LZH compound family, Zn-5(OH)(10)center dot 2H(2)O, with A(m-) = OH- , x = 5, y = 2, and n = 2. Zn-5(OH)(10)center dot 2H(2)O was afforded quantitatively by pressurizing mixtures of epsilon-Zn(OH)(2) (wulfingite) and water to 1-2 GPa and applying slightly elevated temperatures, 100-200 degrees C. The monoclinic crystal structure was characterized from powder X-ray diffraction data (space group C2/c, a = 15.342(7) angstrom, b = 6.244(6) angstrom, c = 10.989(7) angstrom, beta = 100.86(1)degrees). It features neutral zinc hydroxide layers, composed of octahedrally and tetrahedrally coordinated Zn ions with a 3:2 ratio, in which H2O is intercalated. The interlayer d(200) distance is 7.53 angstrom. The H-bond structure of Zn-5(OH)(10)center dot 2H(2)O was analyzed by a combination of infrared/Raman spectroscopy, computational modeling, and neutron powder diffraction. Interlayer H2O molecules are strongly H-bonded to five surrounding OH groups and appear orientationally disordered. The decomposition of Zn-5(OH)(10)center dot 2H(2)O, which occurs thermally between 70 and 100 degrees C, was followed in an in situ transmission electron microscopy study and ex situ annealing experiments. It yields initially 5-15 nm sized hexagonal w-ZnO crystals, which, depending on the conditions, may intergrow to several hundred nm-large two-dimensional, flakelike crystals within the boundary of original Zn-5(OH)(10)center dot 2H(2)O particles.