Hydrogen bonding and molecular orientations across thin water films on sapphire

Boily, Jean-François; Fu, Li; Tuladhar, Aashish; Lu, Zhou; Legg, Benjamin A.; Wang, Zheming M.; Wang, Hongfei

doi:10.1016/j.jcis.2019.08.028

Cited by 15 publications

(18 citation statements)

References 70 publications

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“…The nearly identical OH stretch frequencies in the bulk and at the surface suggest that for gibbsite there are only weak H-bonding interactions between the surface hydroxyls and hydration waters under ambient conditions, and thus the hydration waters only minimally perturb the surface hydroxyl groups. The absence of any significant spectral intensities around 3200, 3400, and 3700 cm –1 , where typical OH stretch frequencies of “ice-like”, “liquid-like”, and “dangling” interfacial O–H stretch vibration frequencies at the water–vapor interface or hydration waters on quartz and sapphire crystal surfaces are expected, ,,− also suggests either relatively low hydration on gibbsite or the hydration waters are oriented in such a way that their O–H groups produce little net VSFG intensity. Indeed, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements (Figure S4) showed that below ∼150 °C, weight reduction, which can be attributed mainly to physisorbed hydration waters, was less than 1%.…”

Section: Resultsmentioning

confidence: 99%

Surface Hydration and Hydroxyl Configurations of Gibbsite and Boehmite Nanoplates

et al. 2020

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The discontinuation of the bulk structure at the interface between metal oxide particles and water leads to altered bonding characteristics and unique facet-dependent molecular environments. Surface hydration and hydroxylation add further complexity to the interface, details that for metal (oxy)hydroxides are especially difficult to isolate from the background signal of bulk structural hydroxyls. Here, we probe for the first time the surface hydroxyl structures and the effect of hydration on basal surfaces of gibbsite (α-Al(OH)3) and boehmite (γ-AlOOH) nanoplates under ambient conditions, using the interface-sensitive technique vibrational sum frequency generation (VSFG) spectroscopy. VSFG spectra of the hydroxyl stretching modes at the interfaces with adsorbed water layers compared directly to Raman and infrared spectra of the bulk modes show that while gibbsite surface frequencies were sharp and nearly identical to those in the bulk, boehmite surface hydroxyls displayed a very different broad spectrum of states. Ab initio molecular dynamics simulations of both basal surfaces with and without hydration waters reveal that gibbsite surface hydroxyls interact only weakly with overlying hydration waters remaining essentially unperturbed, whereas those on boehmite can interact more strongly facilitated by higher configurational degrees of freedom at the interface and there is more extensive H-bonding on boehmite surface under ambient conditions. The findings clearly unveil substantial differences in the hydrated interfacial dynamics of these two otherwise similar materials, with implications for their interfacial chemistry, wettability, and rheology.

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Section: Resultsmentioning

confidence: 99%

Surface Hydration and Hydroxyl Configurations of Gibbsite and Boehmite Nanoplates

et al. 2020

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“…This was achieved using the gmx solvate utility of GROMACS/2018.3 ( 40 ). Classical MD simulations (300 K) as described in our previous work on aluminum oxides ( 4 ) were carried out using the revised ClayFF force field for gibbsite and water ( 41 ). Simulation cells were first energy-minimized (double precision) using a steepest descent algorithm.…”

Section: Methodsmentioning

confidence: 99%

“…These films are intrinsically tied to the availability and transport of water in environmental ( 2 ) and atmospheric ( 3 ) processes. The nano- to microscale solvation environments ( 4 ) of mineral-supported water films impact the global cycling of nutrients and elements in terrestrial environments, control microscale variations in soil pH ( 2 ), and are even crucial for the survival of microorganisms and other life forms in arid environments ( 5 ). Water and ice films additionally play an essential role in atmospheric cloud formation phenomena ( 3 ) and thereby the global climate ( 6 ) and climate geoengineering ( 7 ).…”

Section: Introductionmentioning

confidence: 99%

Direct observation of anisotropic growth of water films on minerals driven by defects and surface tension

et al. 2020

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Knowledge of the occurrences of water films on minerals is critical for global biogeochemical and atmospheric processes, including element cycling and ice nucleation. The underlying mechanisms controlling water film growth are, however, misunderstood. Using infrared nanospectroscopy, amplitude-modulated atomic force microscopy, and molecular simulations, we show how water films grow from water vapor on hydrophilic mineral nanoparticles. We imaged films with up to four water layers that grow anisotropically over a single face. Growth usually begins from the near edges of a face where defects preferentially capture water vapor. Thicker films produced by condensation cooling completely engulf nanoparticles and form thicker menisci over defects. The high surface tension of water smooths film surfaces and produces films of inhomogeneous thickness. Nanoscale topography and film surface energy thereby control anisotropic distributions and thicknesses of water films on hydrophilic mineral nanoparticles.

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“…Building upon our recent work on water vapor binding on minerals, − we here resolved the humidity-dependent loadings of water achieved on birnessite nanoparticles, alongside their resulting vibrational spectral profiles and the interlayer expansion they generate. We predict the microscopic hydration states of birnessite using a composite adsorption–condensation–intercalation model that we recently developed for layered minerals.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Hydration in Layered Manganese Oxides

et al. 2021

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Birnessite is a layered MnO 2 mineral capable of intercalating nanometric water films in its bulk. With its variable distributions of Mn oxidation states (Mn IV , Mn III , and Mn II ), cationic vacancies, and interlayer cationic populations, birnessite plays key roles in catalysis, energy storage solutions, and environmental (geo)chemistry. We here report the molecular controls driving the nanoscale intercalation of water in potassium-exchanged birnessite nanoparticles. From microgravimetry, vibrational spectroscopy, and X-ray diffraction, we find that birnessite intercalates no more than one monolayer of water per interlayer when exposed to water vapor at 25 °C, even near the dew point. Molecular dynamics showed that a single monolayer is an energetically favorable hydration state that consists of 1.33 water molecules per unit cell. This monolayer is stabilized by concerted potassium–water and direct water–birnessite interactions, and involves negligible water–water interactions. Using our composite adsorption–condensation–intercalation model, we predicted humidity-dependent water loadings in terms of water intercalated in the internal and adsorbed at external basal faces, the proportions of which vary with particle size. The model also accounts for additional populations condensed on and between particles. By describing the nanoscale hydration of birnessite, our work secures a path for understanding the water-driven catalytic chemistry that this important layered manganese oxide mineral can host in natural and technological settings.

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Hydrogen bonding and molecular orientations across thin water films on sapphire

Cited by 15 publications

References 70 publications

Surface Hydration and Hydroxyl Configurations of Gibbsite and Boehmite Nanoplates

Surface Hydration and Hydroxyl Configurations of Gibbsite and Boehmite Nanoplates

Direct observation of anisotropic growth of water films on minerals driven by defects and surface tension

Nanoscale Hydration in Layered Manganese Oxides

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