Water Adsorption on Hydrophilic and Hydrophobic Surfaces of Silicon

Chen, Lei; He, Xin; Liu, Hongshen; Qian, Linmao; Kim, Seong H.

doi:10.1021/acs.jpcc.8b01821

Cited by 148 publications

(138 citation statements)

References 79 publications

(140 reference statements)

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“…The water contact angle on a highly hydrophilic surface may be as low as nearly zero and rises with the hydrophobicity of the solid surface [39,40]. Qualitatively, water adsorption preferentially occurs on hydrophilic surfaces [41][42][43][44][45][46]. Apart from the amount or thickness of the water layers adsorbed on a surface, the surface chemistry can also alter the configuration of water molecules in the adsorbed layer.…”

Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

“…When a surface is hydrophilic, both ordered and liquid-like water structures can coexist as the outermost adsorbed layer [10,47]. In contrast, adsorbed water assumes a more liquid-like structure on hydrophobic surfaces [41]. Using MD simulations, Willard et al [48] reported that water molecules adsorbed on hydrophobic surfaces showed diffusive behavior due to the lack of strong interactions with the surface.…”

Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

“…Chen et al [41] compared the configurations of adsorbed water layer on a hydrophilic Si oxide surface (terminated with Si-OH groups, water contact angle <5 • ) and a relatively hydrophobic Si surface (terminated with Si-H groups, water contact angle ≈ 83 • ) by characterizing O-H stretching vibrations using attenuated total reflection infrared (ATR-IR) spectroscopy. As shown in Figure 5a and b, the difference in the H-bonding interactions of water molecules adsorbed on these two surfaces is manifested in the peak shape of the O-H stretching mode in the range of 3000-3800 cm −1 .…”

Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

See 2 more Smart Citations

Thickness and Structure of Adsorbed Water Layer and Effects on Adhesion and Friction at Nanoasperity Contact

Xiao

Shi

et al. 2019

Colloids and Interfaces

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Most inorganic material surfaces exposed to ambient air can adsorb water, and hydrogen bonding interactions among adsorbed water molecules vary depending on, not only intrinsic properties of material surfaces, but also extrinsic working conditions. When dimensions of solid objects shrink to micro- and nano-scales, the ratio of surface area to volume increases greatly and the contribution of water condensation on interfacial forces, such as adhesion (Fa) and friction (Ft), becomes significant. This paper reviews the structural evolution of the adsorbed water layer on solid surfaces and its effect on Fa and Ft at nanoasperity contact for sphere-on-flat geometry. The details of the underlying mechanisms governing water adsorption behaviors vary depending on the atomic structure of the substrate, surface hydrophilicity and atmospheric conditions. The solid surfaces reviewed in this paper include metal/metallic oxides, silicon/silicon oxides, fluorides, and two-dimensional materials. The mechanism by which water condensation influences Fa is discussed based on the competition among capillary force, van der Waals force and the rupture force of solid-like water bridge. The condensed meniscus and the molecular configuration of the water bridge are influenced by surface roughness, surface hydrophilicity, temperature, sliding velocity, which in turn affect the kinetics of water condensation and interfacial Ft. Taking the effects of the thickness and structure of adsorbed water into account is important to obtain a full understanding of the interfacial forces at nanoasperity contact under ambient conditions.

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Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

Section: Effect Of Surface Wettability On Water Adsorptionmentioning

confidence: 99%

See 1 more Smart Citation

Thickness and Structure of Adsorbed Water Layer and Effects on Adhesion and Friction at Nanoasperity Contact

Xiao

Shi

et al. 2019

Colloids and Interfaces

Self Cite

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“…8,9,10,11 Infrared (IR) spectroscopy has proven an ideal method for studying adsorbed water, both qualitatively and quantitatively, as it is very sensitive to water and its states of hydrogen bonding. 9,12,13,14,15 The (O-H) stretching bands located between 3000 cm -1 and 3800 cm -1 give rich qualitative information as they are strongly affected by the molecule's environment and the structure of water. Several water complexes have been reported that can be distinguished within this region based on IR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Pore Size-Dependent Structure of Confined Water in Mesoporous Silica Films from Water Adsorption/Desorption Using ATR–FTIR Spectroscopy

et al. 2019

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The local structure of water on chemically and structurally different surfaces is subject of ongoing research. In particular, confined spaces as found in mesoporous silica have a pronounced effect on the interplay between adsorbate-adsorbate and adsorbate-surface interactions. Mid-infrared spectroscopy is ideally suited to quantitatively and qualitatively study such systems as the probed molecular vibrations are highly sensitive to intermolecular interactions. Here, the quantity and structure of water adsorbed from the gas phase into silica mesopores at different water vapor pressures was monitored using mid-infrared attenuated total reflection (ATR) spectroscopy. Germanium ATR crystals were coated with different mesoporous silica films prepared by evaporation induced self-assembly. Quantitative analysis of the water bending vibration at 1640 cm-1 at varying vapor pressure allowed for retrieving porosity and pore size distribution of the mesoporous films. The results were in excellent agreement with those obtained from ellipsometric porosimetry. In addition, different degrees of hydrogen bonding of water as reflected in the band position and shape of the stretching vibrations (3000-3750 cm-1) were analyzed and attributed to high-density, unordered bulk and low-density, surface-induced ordered water. Thereby, the progression of surface-induced ordered water and bulk water as a function of water vapor pressure was studied for different pore sizes. Small pores with 5 nm diameter showed a number of two ordered monolayers, while for pores > 12 nm the number of ordered monolayers is significantly larger and agrees with the number observed on planar SiO2 surfaces.

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“…Second, the photonic crystal effect can further enhance the plasmonic resonance effects, although the enhancement can possibly be reduced in microfluidic devices due to the smaller index contrast between biosilica and fluid. Third, the hydrophilic surface of diatom pores can absorb target molecules in the solution due to Langmuir adsorption isotherm, allowing physical concentration of the analyte and facilitates better mass transport to the sensing area . Quantitative analysis of these three different effects is beyond the scope of this manuscript and will be investigated in our future research.…”

Section: Resultsmentioning

confidence: 99%

Biological Photonic Crystal‐Enhanced Plasmonic Mesocapsules: Approaching Single‐Molecule Optofluidic‐SERS Sensing

Sivashanmugan

Squire

Kraai

et al. 2019

Advanced Optical Materials

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Optofluidic devices are particularly well-suited for biological and chemical sensing. Especially, nanophotonic sensors employed in optofluidics have greatly overcome the limitations of conventional optical sensors in terms of size, sensitivity, specificity, tunability, photostability, and in vivo applicability. [1] Equally important, microfluidic devices enable facile delivery of sample solution to the sensing region and allow for high throughput detection. However, the limit of mass transport imposed by the laminar flow inside the microfluidic channel dictates the sensitivity and throughput of optofluidic devices. [2] In past years, various optofluidic devices have been developed using microring resonators, [3] metamaterials, [4] surface plasmon resonance (SPR), [5] and surfaceenhanced Raman scattering (SERS). [6] As a vibrational spectroscopic technique, SERS can provide specific information about the molecular structure by the strong local optical field enhancement generated by plasmonic nanoparticles (NPs) or nanostructures. [7] Most published optofluidic-SERS results were obtained utilizing either 1) colloidal metallic NPs flowing inside microfluidic channels, or 2) SERS-active plasmonic nanostructures fabricated on the surface of the microfluidic channels to provide the necessary SERS enhancement factors (EFs). Plasmonic NPs, primarily based on silver (Ag) or gold (Au), such as colloidal metallic NPs, [8] nanorods, [9] nanostars, [10] core-shell NPs, [11] and Surface-enhanced Raman scattering (SERS) sensing in microfluidic devices, namely optofluidic-SERS, suffers an intrinsic tradeoff between mass transport and hot spot density, both of which are required for ultrasensitive detection. To overcome this compromise, photonic crystal-enhanced plasmonic mesocapsules are synthesized, utilizing diatom biosilica decorated with in-situ growth silver nanoparticles (Ag NPs). In the optofluidic-SERS testing of this study, 100× higher enhancement factors and more than 1,000× better detection limit are achieved compared with traditional colloidal Ag NPs, the improvement of which is attributed to unique properties of the mesocapsules. First, the porous diatom biosilica frustules serve as carrier capsules for high density Ag NPs that form high density plasmonic hot-spots. Second, the submicron-pores embedded in the frustule walls not only create a large surface-to-volume ratio allowing for effective analyte capture, but also enhance the local optical field through the photonic crystal effect. Last, the mesocapsules provide effective mixing with analytes as they are flowing inside the microfluidic channel. The reported mesocapsules achieve single molecule detection of Rhodamine 6G in microfluidic devices and are further utilized to detect 1 × 10 −9 m of benzene and chlorobenzene compounds in tap water with near real-time response, which successfully overcomes the constraint of traditional optofluidic sensing.

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Water Adsorption on Hydrophilic and Hydrophobic Surfaces of Silicon

Cited by 148 publications

References 79 publications

Thickness and Structure of Adsorbed Water Layer and Effects on Adhesion and Friction at Nanoasperity Contact

Thickness and Structure of Adsorbed Water Layer and Effects on Adhesion and Friction at Nanoasperity Contact

Pore Size-Dependent Structure of Confined Water in Mesoporous Silica Films from Water Adsorption/Desorption Using ATR–FTIR Spectroscopy

Biological Photonic Crystal‐Enhanced Plasmonic Mesocapsules: Approaching Single‐Molecule Optofluidic‐SERS Sensing

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