Wettability of Bare and Graphene-Adsorbed Pt(111) during Glass

Article Cite This: J. Phys. Chem. C XXXX, XXX, XXX−XXX

pubs.acs.org/JPCC

Wettability of Bare and Graphene-Adsorbed Pt(111) during Glass− Liquid Transition, Crystallization, and Premelting of Water Ryutaro Souda*,† and Takashi Aizawa*,‡ †

J. Phys. Chem. C Downloaded from pubs.acs.org by YORK UNIV on 12/03/18. For personal use only.

Transmission Electron Microscopy Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan ‡ Center for Functional Sensor & Actuator, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan ABSTRACT: Properties of thin water films on Pt(111) with and without monolayer graphene (MLG) in between were investigated using reflection high-energy electron diffraction, time-of-flight secondary-ion mass spectrometry, and temperature-programmed desorption. During water deposition at 100 K, water molecules in direct contact with the MLG/Pt(111) surface tend to be arranged locally by directing free OH groups toward the substrate. However, such species is formed initially only in the submonolayer regime on bare Pt(111). This behavior is likely to be associated with hydrophobic hydration. Crystallites of cubic and hexagonal ices with (111) and (0001) orientations, respectively, are grown epitaxially on the Pt(111) and MLG/ Pt(111) substrates with considerable stacking disorders. The Hdown water species remain on Pt(111) after crystallization, although they disappear completely from the MLG/Pt(111) substrate. These behaviors indicate that the water monolayer is equilibrated with a premelting layer on the ice crystallite. It behaves like a liquid and plays a role in the ripening of pre-existing crystallites during water vapor deposition. Consequently, the potential field and wettability of the Pt(111) substrate are not transmitted through the MLG layer formed on it, as far as the liquidlike water formed at cryogenic temperature is concerned.

1. INTRODUCTION Water adsorbed on solid surfaces and confined in nanoporous media is ubiquitous in nature. Understanding its properties is of fundamental importance not only for natural science, such as biology, astrophysics, and environmental science, but also for technological applications of functional materials. It is established that hydrogen-bonded two-dimensional ice films are formed on close-packed transition metal surfaces, such as Pt(111), Ru(0001), Ni(111), and Pd(111), at cryogenic temperatures.1−4 It has been considered that a buckled “bilayer” of ice, which is analogous to the (0001) and (111) planes of hexagonal ice Ih and cubic ice Ic, is formed.1,2 In reality, however, no consensus has been reached regarding the structure and properties of two-dimensional (2D) water layers in direct contact with substrates.4 The second nearest neighbor distances in transition metal close-packed surfaces are similar to the lateral spacing of water in bulk ice, so that a (√3 × √3) R30° pattern observed in low-energy electron diffraction (LEED) has been ascribed to the formation of a commensurate hexagonal ice bilayer.1,2 However, recent experiments and theory have revealed that water forms a range of different hydrogen-bonded clusters or networks,4 suggesting that the strength of the metal−water bond and the chemical reactivity of the surface control the film structure rather than the lateral lattice parameter matching. In fact, Feibelman5 depicted that a partially dissociated hydrogen© XXXX American Chemical Society

bonded network is formed on Ru(0001) because the binding energy of an intact water bilayer is too small to stabilize a continuous 2D layer over the formation of three-dimensional (3D) ice crystallites. In contrast, water does not dissociate on Pt(111)1−4 or does so in very small amounts.6 Slow deposition of water molecules onto the Pt(111) substrate at temperatures above ca. 130 K leads to a 2D domain of a (√37 × √37)R25° structure, which is replaced by a (√39 × √39)R16° structure with increasing coverage, as demonstrated by both helium atom scattering (HAS)7 and LEED.8 Such ordered domains are imaged by using scanning tunneling microscopy (STM).9 It is likely that the previously reported (√3 × √3)R30° LEED pattern occurs when the film is damaged by an electron beam or when water is coadsorbed with a small amount of oxygen because chemisorbed O and OH species pin the water structure with respect to the Pt(111) surface.10 Further information about the structure of a water monolayer (ML) on Pt(111) was obtained by Ogasawara et al.11 Using a crystalline ice film formed by heating amorphous solid water (ASW) at 140 K, they observed that all water molecules in the first layer bind directly to the Pt(111) surface via alternating metal−oxygen and metal−hydrogen bonds, Received: August 30, 2018 Revised: November 13, 2018

A

DOI: 10.1021/acs.jpcc.8b08445 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C thereby forming a flat H-down overlayer. The multilayer water does not necessarily form a continuous crystalline film on top of this ML because water nucleation might be inhibited on the wetting ML.4,8 Consequently, crystallites are expected to grow via a Stranski−Krastanov mode. Kimmel et al.12 claimed that the water ML on Pt(111) is hydrophobic because the H-down water ML cannot form further hydrogen bonds with the multilayer film via H donation. Thus, it is considered that multilayer adsorption is very sensitive to the binding energy of the first water layer and that this can be reconstructed easily. In any case, continuous ice films can be formed at higher water coverage. The LEED I−V analyses revealed that crystalline films thicker than ca. 40−50 layers exhibited a (1 × 1) termination of ice Ih(0001).13 It was also shown that water molecules in the upper half of the bilayer were invisible to LEED because of a large amplitude vibrational motion. On the other hand, graphite appears to be more hydrophobic than transition metal substrates like Pt(111) and Ru(0001), as revealed from the occurrence of complete dewetting after crystallization of ASW on highly oriented pyrolytic graphite (HOPG).14,15 It is also revealed that the adsorbed water species tend to direct their OH groups toward the HOPG substrate before crystallization occurs.15 To date, molecular dynamics (MD) simulations have been carried out to reveal the structure and dynamics of liquid water confined in carbon nanotubes and near ML graphene (MLG) sheet(s).16−23 Many plausible structures of the hydrogenbonded water molecules at the substrate interface have been proposed, including a bulklike structure,21 a slight preference for H-up orientations (near parallel being the likeliest),22,23 and the presence of the free OH group (H-down orientations).16−20 In this respect, a unique behavior of “wettability transparency” was recently reported for liquid water on supported MLG:24 The contact angles of water on Cu, Au, and Si substrates are transmitted to MLG formed on them, implying that van der Waals interactions between graphene and water are negligible. In reality, however, interactions of water with MLG are controversial. There exist conflicting experimental and theoretical reports supporting the opaqueness,25,26 transparency,24 and translucency27,28 in water wettability of MLG. A key difference comes from different extents of screening of different interactions by graphene.29 The real surface wettability can also be masked in atmospheric contact angle measurements by hydrocarbon contaminants from the environment.25 Regarding the structure of crystalline ice formed on MLG/Pt(111), Kimmel et al. reported that a new ice polymorph consisting of two flat water layers was formed when water was deposited at temperatures between 100 and 135 K.30 The water molecules are arranged in plane hexagonal units, and the two water layers are stacked on top of each other, so that the number of hydrogen bonds in the ice film is maximized to weaken the interaction with the hydrophobic substrate. Such a new ice polymorph was first predicted to occur when water was confined in hydrophobic slit pores.31 Kimmel et al. claimed that such a structure was created even for supported water films using the MLG/ Pt(111) substrate. Very recently, a remarkable property of MLG was reported in terms of “remote epitaxy”:32 GaAs grows homoepitaxially on a GaAs(001) substrate beyond the MLG layer in between, suggesting that the potential field of the substrate propagates through MLG without screening. Therefore, it is of great interest to reveal whether or not the

crystallization kinetics of water and wettability of Pt(111) are influenced by the MLG layer formed on it. The wettability of solid surfaces should be discussed in terms of the interaction with liquid water. At cryogenic temperatures, liquidlike water is formed above the glass transition temperature (Tg) of 136 K, as determined from differential scanning calorimetry33 and time-of-flight secondary-ion mass spectrometry (TOF−SIMS).34 In the framework of polyamorphism,35 it is well-established that the liquid water formed at Tg is a distinct phase, termed low-density liquid (LDL). Its local structure resembles that of crystalline ice rather than normal liquid water.36 In the ML regime, the water mobility commences in the sub-Tg region (ca. 110−120 K), as revealed from the water uptake in mesoporous media.37 On the other hand, another type of liquidlike water (quasi-liquid) is formed on the crystallite surface via premelting, as demonstrated by the uptake behavior of alkali-halide adspecies in the ice film interior38 as well as the decomposition of thin crystalline ice films on a reactive V substrate.39 Till date, water crystallization kinetics has been explored using various experimental methods, such as isothermal desorption, 40−43 temperature-programmed desorption (TPD),43−48 reflection high-energy electron diffraction (RHEED),49−52 and reflection absorption infrared spectroscopy,47,53,54 in addition to LEED13 and STM.55 Water crystallization is strongly substrate-dependent at a specific film thickness,42 but crystallization might be initiated from the free surface.54 Although bilayer and multilayer ice Ih are reported to form on Pt(111) based on LEED,13 RHEED studies conclude that metastable ice Ic crystallites are grown preferentially on both hydrophilic and hydrophobic substrates.49−52 RHEED has the advantage of analyzing small crystallites descended from thinner ASW films in contrast to LEED. This might be responsible for the discrepancy in the observed crystalline ice structures. The purpose of this paper is to investigate the interactions of water molecules with bare and MLG-adsorbed Pt(111) substrates, especially in the (sub)-ML regime, to gain more insight into the structures of 3D ice crystallites and properties of 2D water layers. To this end, crystallization and dewetting kinetics of water are explored using RHEED, TOF−SIMS, and TPD as functions of substrate temperature and water coverage. The structure and morphology of crystalline ice films formed by heating the initial ASW films and during water vapor deposition are analyzed by combined RHEED and TOF− SIMS analyses. The local orientation of water molecules at the substrate interface is discussed based on relative TOF−SIMS yields as a function of temperature. The origin of the 2D water layer and its properties are explored by comparison of wettability between the bare and MLG-adsorbed Pt(111) substrates during the glass−liquid transition and premelting of water.

2. EXPERIMENTAL SECTION The substrate was a crystalline platinum disc (10 mm ϕ, 1 mm thick) with a mirror-finished (111) face, which was spotwelded to a sample holder made of Ta. It was inserted into an ultrahigh vacuum (UHV) chamber (base pressure of 2 × 10−10 Torr) through a load-lock system. Cooling of the sample was achieved by means of a closed-cycle helium refrigerator. The substrate temperature was controlled using a cartridge heater by monitoring the temperature of the cold finger close to the sample position using Au(Fe)-chromel thermocouples. Liquid B


Article

The Journal of Physical Chemistry C water and benzene were degassed before use via several freeze−pump−thaw cycles. Their vapors were admitted into the UHV chamber through precision variable leak valves. The substrate was heated to ∼1500 K by electron bombardment from behind. Contaminants were removed by several Ar+ sputtering and annealing cycles. MLG was formed on the clean Pt(111) substrate via thermal decomposition of benzene: the substrate was heated to ca. 1000 K under the backfilling benzene pressure of 5 × 10−7 Torr for 200 s. Cleanliness of the Pt(111) substrate as well as the formation of the MLG layer were confirmed based on the TOF−SIMS spectra and RHEED patterns. The UHV chamber was equipped with a high-energy electron gun (Eiko Co. Ltd., MB-1000) and a phosphor screen for RHEED. Diffraction patterns were recorded using a high-sensitivity charge-coupled device camera. To reduce undesirable effects by a high-energy electron beam (30 keV), the image was taken intermittently (pulse duration of ∼0.5 s) only at a specific temperature and coverage of interest. TOF− SIMS measurements were made using a primary beam of 2 keV He+ ions generated in an electron impact-type ion source (SPECS GmbH, IQE 12/38) after chopping into pulses. Positive secondary ions ejected perpendicularly to the surface were detected using a microchannel plate after passing through a field-free TOF tube. To extract low-energy secondary ions efficiently, a bias voltage (+500 V) was applied to the sample, and a removable mesh plate (grounded) was placed in front of the sample surface. TOF−SIMS spectra were constructed every 30 s using a multichannel scaler (Laboratory Equipment Inc., LN-6500R). Degradation of the sample by He+ irradiation was minimized by keeping the fluence below 1 × 1012 ions cm−2 (sample current of ∼0.1 nA/cm−2). TPD spectra were obtained using a quadrupole mass analyzer (Hiden Analytical Ltd., IDP 300S) put in a differentially pumped housing. An orifice of the housing was approached closer to the sample surface (∼2 mm) to reduce the background signal. The substrate temperature was ramped at a rate of 5 K min−1 during temperature-programmed measurements of RHEED, TOF−SIMS, and TPD.

Figure 1. (a) Evolutions of typical secondary-ion intensities from the water-adsorbed Pt(111) substrate as a function of exposure of water molecules at 100 and 125 K. RHEED images of the films formed during exposure of 5 L water molecules at (a) 100 and (b) 125 K are also shown. They are taken along the [11−2] azimuth of Pt(111).

gradually at 125 K relative to that at 100 K. This is expected to occur when the film grows inhomogeneously: A 2D layer that yields higher Pt+(H2O)2 intensity tends to remain in the multilayer regime because 3D islands are formed via water crystallization. This is confirmed from a spotty RHEED pattern displayed in Figure 1c, which is obtained during 5 L water deposition at 125 K. The spotty pattern is fundamentally unchanged with further increasing water coverage. In contrast, a diffuse RHEED pattern shown in Figure 1b is obtained at a substrate temperature of 100 K, indicating that an ASW film is deposited. The dewetting and crystallization kinetics of initial ASW films with different thicknesses were investigated as a function of the substrate temperature. Figure 2 displays the experimental results of (a) temperature-programmed TOF− SIMS and (b) TPD of water molecules (0.5 L) adsorbed on the Pt(111) substrate at 100 K. The secondary-ion intensities decrease at 155−170 K along with water evaporation, as revealed from the water TPD spectrum. The peak at higher (lower) temperature is ascribable to thermal desorption of water from 2D (3D) domains.8,12 Consequently, a part of water molecules tend to agglomerate to form multilayer domains even at such small exposure. Figure 3 represents the experimental results of (a) TOF− SIMS and (b) TPD obtained using the ASW film formed on Pt(111) by exposure of 1 L water at 100 K. In this case, a stepwise decrease of the H+ intensity is observed using TOF− SIMS at 150, 160, and 170 K. A similar step is also identified in the H3O+ intensity at 160 K. The TPD spectrum consists of 2D (170 K) and 3D (160 K) peaks; the latter is more intense than the former even at such a small exposure as 1 L. All secondary ions decay at 170 K along with the 2D peak of TPD. The steps of H+ and H3O+ intensities at 160 K are associated

3. EXPERIMENTAL RESULTS 3.1. Pt(111). Figure 1a shows the typical secondary-ion intensities from the Pt(111) substrate as a function of exposure of water molecules at 100 K (solid lines) and 125 K (broken lines). The TOF−SIMS spectra were taken continuously under the backfilling pressure of water at 1 × 10−8 Torr. No secondary ions were emitted from the clean Pt(111) substrate. Upon adsorption of water, not only H+ and H3O+ ions but also ion adducts in the form of Pt+(H2O)n were emitted. The former is created via collisions between water molecules and tend to saturate in intensity at ca. 2 L (Langmuir; 1 L = 1 × 10−6 Torr s), whereas the latter is formed during collisions between Pt and water on the way out from the surface. Till date, we have assigned the saturation point of the former (2 L) to completion of the first ML. This definition conflicts significantly with that based on TPD, as described later. In this paper, therefore, the film thickness is estimated from water exposure instead of its exact coverage. The Pt+(H2O)2 ions are emitted even after the substrate is covered by multilayer water films. The initial sticking probabilities of water are almost same at temperatures between 100 and 125 K, as revealed from the ion evolution curves in the sub-ML regime. With increasing exposure, however, the Pt+(H2O)2 intensity decreases rather C


Article

The Journal of Physical Chemistry C

to water crystallization, as demonstrated by the RHEED patterns shown in the inset of Figure 3b: A diffuse pattern of ASW at 140 K becomes spotty at 150 K. The spots disappear after evaporation of crystallites at 160 K; the RHEED pattern from the 2D layer at 162 K exhibits no ordered structures except for the Pt(111) substrate. The TOF−SIMS intensities obtained using the ASW film formed by water exposure of 5 L are shown in Figure 4a. The

Figure 2. Temperature-programmed TOF−SIMS intensities (a) and TPD spectrum (b) from the water-adsorbed Pt(111) substrate. After exposure of 0.5 L H2O molecules at 100 K, the temperature was ramped at a rate of 5 K min−1.

Figure 4. Same as in Figure 2, but for exposure of 5 L H2O.

secondary-ion intensity changes at 155−160 K. The increase in the Pt+(H2O)2 intensity at this temperature indicates that the film morphology changes as a result of the formation of 3D islands (i.e., crystallites) and patches of the 2D layer that emits Pt+(H2O)2 efficiently. This dewetting transition is also responsible for the simultaneous decays of the H+ and H3O+ intensities. The water TPD spectrum in Figure 4b consists of a main peak from crystallites at 167 K and a small shoulder from the 2D layer at 170 K. An additional shoulder occurs at ca. 160 K because of water crystallization.44,45 Figure 5 presents the experimental results of (a) TOF− SIMS and (b) TPD obtained using the ASW film (20 L) formed on Pt(111) at 100 K. No Pt+(H2O)2 ion is ejected initially; it evolves during crystallization at ca. 160 K simultaneously with the water TPD shoulder. The 2D layer remains after the growth of crystal grains, as revealed from the high Pt+(H2O)2 intensity. However, the 2D peak in TPD (∼170 K) is hidden by the intense 3D peak because the latter shifts to higher temperatures with increasing water coverage as a result of the zero-order desorption kinetics. The crystallization kinetics of water described above is confirmed based on RHEED images, as portrayed in Figure 6. All images were obtained along the [11−2] azimuth of Pt(111). For the clean Pt(111) substrate (a), intense diffraction rods are recognizable in the zero-order and firstorder Laue zones. After the formation of ASW films at 100 K, the rods from the Pt(111) substrate are weakened, and diffuse scattering characteristic of the amorphous phase is observed (see Figure 1b). The RHEED images displayed in (b−f),

Figure 3. Same as in Figure 2, but for exposure of 1 L H2O at 100 K. RHEED images from the film at specific temperatures are also shown in (b). They are taken along the [11−2] azimuth of Pt(111).

with desorption of crystallites, as manifested by the occurrence of the 3D peak in TPD. In contrast, the Pt+(H2O)2 ion remains considerably after the disappearance of crystallites because it is emitted preferentially from the 2D layer (see Figure 1). Nothing happens in the water TPD spectrum at around 150 K although it is identified as the first decay of H+ in TOF−SIMS. It should be noticed that the film becomes inhomogeneous even at such small water coverage. This behavior is ascribable D


Article


diffraction from crystallites is identifiable using the thinnest film (b) at any temperature. However, Bragg spots appear in (c,d) because of the epitaxial growth of crystallites with respect to the Pt(111) substrate. The spotty RHEED pattern is also observed using the 5 L ASW film (e). However, it switches to a Debye−Scherrer ring pattern for the 20 L ASW film (f) because crystallites grow randomly. The spotty and streaky diffraction patterns are observable provided that the 3D TPD peak occurs via film dewetting because water molecules aggregate upon crystallization. This appears to be not the case for the thinnest film formed by exposure of 0.5 L water. Probably, nascent crystallites or “nuclei” formed in this sub-ML film are not identified clearly by RHEED because of the limited number or smaller size of grains relative to the coherence length of electrons. The spotty RHEED patterns are interpreted either as the (111) oriented ice Ic or as the (0001) oriented ice Ih; simulated RHEED patterns for the ices Ih and Ic, respectively, are represented in Figure 6g,h. The spotty RHEED patterns in Figure 6c,d are basically assignable to 3D grains of ice Ih. However, lack of (102), (104), (202)... spots and streaky (101), (103), (201)... spots suggest that stacking of the basal planes is fairly disordered, namely crystallites themselves contain a large number of stacking faults.56 Weak streaks underlying the spots suggest that crystal grains have a flat terrace or that a 2D water lattice exists. Crystallites grown in another azimuthal angle are also recognizable as additional sharp spots in Figure 6e. In contrast to the crystallites formed by heating the initial ASW film, diffraction spots of ice Ic are dominant when water is deposited at 125 K as displayed in Figure 1c, where additional spots appear between the original spots of ice Ic because twins are formed. 3.2. MLG/Pt(111). In this section, it is explored how MLG formed on the Pt(111) substrate influences wetting and crystallization kinetics of water in comparison with the abovementioned results using bare Pt(111). Figure 7 displays (a) TOF−SIMS and (b) TPD experimental results obtained using the ASW film formed on MLG/Pt(111) by exposure of 1 L water at 100 K. Because of the presence of MLG, ion sputtering from the Pt(111) substrate is quenched completely; instead, reacted ions such as HCO+ are emitted. This result signifies that only the substrate species in direct contact with the water molecules form ion adducts or reacted species. All secondary ions tend to decrease in intensity at ca. 150 K, which is followed by a complete decay of H+ and H3O+ ions at 165 K. The former is ascribable to the growth of crystal grains, whereas the latter corresponds to their thermal desorption, as manifested by the occurrence of the water TPD peak at this temperature. The complete decay of the HCO+ ion at 150 K as well as the absence of the double-peak structure in water TPD indicates that no 2D layer of water remains after crystallization in contrast to the result using the bare Pt(111) substrate. The crystallization kinetics of ASW is investigated based on RHEED patterns as a function of the initial film thickness. Figure 8 displays the typical images from (a) the MLG/ Pt(111) substrate and crystalline ices formed on it: the initial ASW films prepared by exposures of (b) 0.5, (c) 1, (d) 2, (e) 5, and (f) 20 L water at 100 K were crystallized by heating them above 150 K. The MLG grows incommensurately with respect to the Pt(111) substrate and yields weak streaks that appear inside and outside the rods from the Pt(111) substrate in the zero-order Laue zone, as reported previously.57 All RHEED images from water signify the formation of 3D grains.

Figure 5. Same as in Figure 2, but for exposure of 20 L H2O.

Figure 6. RHEED images of the clean Pt(111) substrate (a) and crystalline ice films formed by heating ASW to 155−160 K. The ASW films were prepared by exposure of (b) 0.5, (c) 1, (d) 2, (e) 5, and (f) 20 L water molecules at 100 K. The images were taken along the [11−2] azimuth of Pt(111). Simulated RHEED patterns for (g) (0001)-oriented hcp and (h) (111)-oriented fcc lattices are also displayed.

respectively, are obtained by heating ASW films formed by exposures of 0.5, 1, 2, 5, and 20 L water above 150 K. No E


Article


grow randomly with respect to the substrate, in agreement with the result using bare Pt(111) (see Figure 6f). Consequently, the epitaxial growth of crystallites is identified only for thinner ASW films. Figure 9 exhibits the evolutions of typical secondary-ion intensities during deposition of water molecules onto the

Figure 7. Temperature-programmed TOF−SIMS intensities (a) and TPD spectrum (b) from the MLG/Pt(111) substrate after exposure of 1 L water molecules at 100 K.

Figure 9. Evolutions of typical secondary-ion intensities from the water-adsorbed MLG/Pt(111) substrate as a function of exposure of water molecules at 100 and 125 K.

MLG/Pt(111) substrate at 100 K (solid lines) and 125 K (broken lines). The H3O+ intensity tends to saturate by deposition of 2 L water at 100 K, but the H+ intensity increases gradually, providing a contrast to the result using bare Pt(111) (see Figure 1). The ion evolutions during deposition at 125 K are suppressed considerably at small exposures. This behavior is partly ascribable to reduction of the initial sticking probability of water molecules at 125 K. In fact, the integrated TPD peak area from the film formed by exposure of 1 L water at 125 K is about half of that formed at 100 K (not shown). The slow evolution of the initial TOF−SIMS intensities at 125 K also results when crystallites are formed during water vapor deposition. Figure 10 displays the RHEED images of

Figure 8. RHEED images of the MLG/Pt(111) substrate (a) and crystalline ice films formed by heating ASW to 150−160 K. The ASW films were prepared by exposure of (b) 0.5, (c) 1, (d) 2, (e) 5, and (f) 20 L water molecules at 100 K. The images were taken along the [11−2] azimuth of Pt(111).

Figure 10. RHEED images of crystalline ices formed by exposing the MLG/Pt(111) substrate to (a) 1 and (b) 5 L water molecules at 125 K.

The diffraction spots exhibit a characteristic of ice Ic at smaller coverage; they become streaky with increasing coverage, suggesting the coexistence of Ic and Ih crystallites or the formation of stacking disorders.56 The sharp spots inside the second rods come from crystallites grown with randomly oriented basal planes along the surface normal like MLG. The Debye−Scherrer ring pattern occurs in (f) because crystallites

water films formed at 125 K on MLG/Pt(111). In both ML (1 L; a) and multilayer (5 L; b) regimes, diffraction spots of ice Ic are recognizable. The diffraction patterns become spottier than those from the crystalline films formed by heating the initial ASW films above ca. 150 K (see Figure 8). Further information about the local structure of water molecules can be obtained from the relative secondary-ion F


Article


tends to be directed toward the substrate before and after crystallization.

intensities in TOF−SIMS because ions are created efficiently via breakage of partly ionic bonds (the bond-breaking mechanism).58,59 Therefore, the H+ intensity from water is expected to provide information about the original O−H bond direction.15 To this end, the intensity of H+ is replotted relative to that of H3O+ as a function of temperature. Figure 11

4. DISCUSSION 4.1. Pt(111). The morphology and local structure of ASW films are unchanged on Pt(111) after the evolution of LDL at Tg = 136 K. The film morphology changes at ca. 150−160 K as a result of crystallization, resulting in 3D crystallites and an extended 2D layer. The ice Ih crystallites with stacking disorders grow preferentially having an epitaxial relationship of (0001)Ih//(111)Pt and [11−20]Ih//[11−2]Pt. A randomly oriented polycrystalline film is descended from the 20 L ASW film because of the spontaneous nucleation in the film interior. The thinnest ASW film (0.5 L) is fundamentally regarded as a wetting 2D layer, although small crystallites (nuclei) are likely to coexist. The free OH group of water at the substrate interface tends to be directed toward the Pt(111) substrate. This occurs not only after water crystallization but also during deposition of ASW at 100 K. Till date, the H-down orientation of water has been observed on Pt(111) after film dewetting (i.e., crystallization).11 The presence of such species has not been reported during deposition of ASW because only a limited number of molecules are reoriented at the very initial stage of water deposition, as shown in Figure 11a. First, we need to address discrepancy in definitions of water coverage between the present and previous studies. We have determined the completion of the first ML of ASW from the saturation point of the H3O+ evolution curves in TOF−SIMS. However, the film thickness has often been determined from the saturation exposure of the 2D peak intensity in TPD.8,12 The definition in TPD relies on the assumption that a uniform multilayer film desorbs in a layer-by-layer fashion till the last layer bound tightly to the substrate disappears, thereby yielding the 2D peak well separated from the 3D peak (see Figures 2−4). Apparently, this assumption is not valid for inhomogeneous (dewetted) crystalline ice films. The H-down water species yielding the 2D TPD peak is not simply ascribable to crystalline ice, as evidenced by the fact that no long-range order is recognizable in RHEED (see Figure 3b). Probably, the adhesive energy of water molecules on Pt(111) is so small that 3D grains (crystallites) tend to form. This manifests itself most typically in the occurrence of the 3D peak at such small exposure as 0.5 L. In contrast to the inhomogeneous crystalline ice film, fundamentally uniform ASW and LDL films are deposited at lower temperatures, so that we have defined the ML based on the saturation point of TOF−SIMS evolution curves. RHEED images imply that an ordered 2D layer or an ice Ih crystallite having a flat terrace grows at ca. 150 K (Figure 6). The former is denied if it is identical to the 2D layer formed after the evaporation of crystallites. The latter is supported by the STM observation as far as the morphology of crystallites is concerned.60 The detailed structural information about such small crystallites is not obtainable using experimental techniques other than RHEED. Indeed, LEED13 and HAS61 studies have so far revealed the presence of large flat domains of ice Ih(0001) as thick as 40−50 layers via water vapor deposition at 130−140 K, although the ordered 2D ice layers exhibiting (√37 × √37)R25° and (√39 × √39)R16° structures are also identified.7,8 The latter is not observed in the present study. Probably, they are formed under specific conditions of the water adsorption rate and substrate temperature, as described in the literature.7

Figure 11. TOF−SIMS relative intensities of H+ to H3O+ as a function of temperature. Results using (a) Pt(111) and (b) MLG/ Pt(111) substrates after exposure of 0.5−5 L water molecules are compared.

displays the experimental results for (a) Pt(111) and (b) MLG/Pt(111) substrates covered by ASW with different thicknesses. The relative H+ yield is small for thinner ASW films (T < 150 K) on both substrates. The suppression of the H+ yield is not ascribable to ion neutralization effects by the substrate. This was demonstrated by using ASW films deposited onto HOPG at 20 K:15 The H+ (H3O+) intensity decreases gradually (remains almost constant) with increasing temperature up to 150 K. The present and previous studies reveal that the free OH group of interfacial water tends to be directed toward the substrate prior to crystallization. It should be noticed that the H-down water molecules are formed preferentially till completion of the first ML (2 L; according to the TOF−SIMS definition) on MLG, whereas they are observed only at the very initial stage of water deposition on Pt(111). After water crystallization at 150 K, the relative H+ yields also contrast sharply between the bare and MLGadsorbed Pt(111) substrates. The results for MLG/Pt(111) are interpreted more straightforwardly because crystal grains formed via complete dewetting are dispersed on the MLG surface without the 2D layer. The relative H+ yield increases because the unpaired OH group on the crystallite surface is directed toward the vacuum side. The opposite behavior is expected to occur when the 2D layer occupies a larger area than the 3D crystallites via the dewetting transition. Probably, this is the case for the results using the bare Pt(111) substrate. Consequently, the free OH group of water forming a 2D layer G


Article


2D layer formed after water crystallization (i.e., quasi-liquid). Probably, this is the reason why the H-down water species are formed at the substrate interface before and after crystallization. 4.2. MLG/Pt(111). The presence of MLG modifies the surface properties of Pt(111) significantly in terms of the sticking probability of water molecules, crystallization kinetics of the ASW film, and wetting of quasi-liquid layer formed after crystallization. The results using MLG/Pt(111) are fundamentally identical to those using HOPG.14,15,52 Apparently, the wettability and epitaxy of the Pt(111) substrate do not propagate through the MLG layer, as far as interactions with LDL and quasi-liquid formed at cryogenic temperatures are concerned. The H-down interfacial structure of ASW is realized more preferentially on MLG than on bare Pt(111) till higher water coverage (see Figure 11). Probably, this phenomenon is associated with hydrophobicity of the MLG surface because local ordering of water is enhanced via “hydrophobic hydration.”16 The multilayer ASW film (5 L) also prefers the H-down configuration at temperatures higher than water’s bulk Tg of 136 K, as demonstrated in Figure 11b, suggesting that the interfacial water also influences the structure of the second LDL layer (i.e., formation of the second “hydration shell”). So far, local structure ordering of liquid water and presence of the free OH group near the graphene sheet have been suggested by MD simulations.16−20 Such an interfacial structure appears to be realized more preferentially for LDL rather than normal water because the former resembles crystalline ice in the local structure.36 The 2D layer of water completely dewets the MLG/Pt(111) surface after crystallization occurs, thereby resulting in scattered ice grains and bare MLG patches. The result is explainable as the merger of the quasi-liquid layer with equilibrating crystal grains. This behavior is likely to occur if the adhesive energy of the H-down species on MLG is smaller than the cohesive energy of water on the crystallite surface. Consequently, the 2D water layer on MLG is stabilized (destabilized) for LDL (quasi-liquid) because of the absence (presence) of crystallites. Kimmel et al.30 reported that two-layer crystalline ice films grew on the MLG/Pt(111) substrate when water was deposited at temperatures between 100 and 135 K. The water molecules are arranged in flat hexagonal units, and the two water layers are stacked on top of each other to minimize the number of free OH groups at the interface. The present result apparently conflicts with this model because scattered 3D grains of ice Ic crystallites are grown from the very initial stage of water deposition at 125 K on MLG/Pt(111) (Figures 9 and 10). No indications of the growth of such a layered crystalline ice film are obtained at all. However, the 2D layer tends to coexist with Ic crystallites during water deposition at 125 K, as revealed from the HCO+ intensity that becomes conspicuous with increasing exposure (>5 L). The H+ intensity is suppressed relative to the H3O+ intensity both during crystal growth at 125 K and ASW deposition at 100 K (Figure 9) because the free OH group of the 2D layer is directed toward the MLG surface before and after crystallization. Consequently, a quasi-liquid layer is formed transiently during water deposition at temperatures slightly higher than the surface diffusivity onset (125 K), although it is finally absorbed by crystallites on the MLG surface with increasing temperature (Figure 7). No long-range order other than ice Ic is identified using RHEED in Figure 10. However, MD simulations

When the water vapor is deposited at 125 K, nonwetting growth of crystallites occurs after completion of the 2D layer (Figure 1). The 2D layer tends to remain till considerably high exposures, as revealed from the gradual decrease of the Pt+(H2O)2 intensity. At such a low substrate temperature of 125 K, crystallites of metastable ice Ic are formed preferentially with the epitaxial relationship of (111)Ic//(111)Pt and [1− 10]Ic//[11−2]Pt (Figure 10) instead of stable ice Ih. In this context, a question is posed as how the crystal grows epitaxially on the 2D layer whose OH group is directed toward the substrate.8 The 3D crystallites are expected to be formed onto the 2D layer via the Stranski−Krastanov type growth. In order for this to occur, reconstruction of the 2D water to form hydrogen bonding with the ice multilayer is required, or the strain induced by the lattice constant misfit must be released if the 2D layer survives under the crystallites. The wetting layer restructures from the H-down to an H-up orientation in response to second-layer adsorption. The binding energy of the original H-down bilayer is only slightly larger than that for the H-up bilayer.4 The crystalline ice films appear to grow without wetting the 2D layer during water deposition at higher temperatures (T > 135 K). In this respect, Kimmel et al.12 suggested that the water ML is hydrophobic in nature because of the absence of dangling OH bonds or lone pair electrons to accept H. Using the initial ASW films, we can discuss the water crystallization kinetics without introducing confounding ideas such as water hydrophobicity. As demonstrated here, the Hdown configuration of water is realized at the substrate interface of ASW during deposition at 100 K, but the film morphology is unchanged after LDL evolves in the ML (multilayer) regime at 110−120 K (136 K). Apparently, the Hdown species at the interface does not influence the wetting behavior of LDL formed with increasing water coverage. Moreover, even the thinnest ASW film (0.5 L) that consists of H-down species (see Figure 11a) tends to nucleate, as evidenced by the occurrence of the 3D TPD peak in Figure 2. Apparently, the H-down species in direct contact with the substrate does not disturb the water nucleation. In any case, the amount of such water species at the substrate interface is so small that they are expected to have negligible effects on water crystallization kinetics during water vapor deposition at higher temperature. As described earlier, the liquidlike water (quasi-liquid) is formed even after crystallization because of premelting. The premelting is thought to result from the large vibrational amplitude of the crystal surface.62 In fact, the LEED structure analysis of the topmost surface of the crystalline ice bilayer becomes impossible at temperatures higher than 100 K because of the Debye−Waller factor.13 Such species can pop out from the lattice to the free surface and gain mobility, thereby forming a quasi-liquid layer.63 Therefore, the H-down water species in the 2D layer can be regarded as the quasiliquid that is spread over the substrate from the crystallite surface. During the water vapor deposition, the molecules are conveyed to the crystallites via incorporation in the quasiliquid layer, thereby resulting in ripening of the preexisting crystallites. Probably, this is the reason why the activation energy for crystal growth (56 kJ/mol) is much smaller than that for nucleation (140 kJ/mol).64 On the other hand, LDL is formed by heating ASW above Tg before crystallization occurs. LDL has local structural resemblance to crystalline ice Ih.36 Therefore, the ML of LDL is expected to be identical to the H


Article

The Journal of Physical Chemistry C Author Contributions

predicted that a hexagonal water layer can be formed on graphite.65 The quasi-liquid layer might be ordered when it is quenched before incorporation into crystallites.

R.S. and T.A. contribute equally to this work. Notes

The authors declare no competing financial interest.

■

5. CONCLUSIONS Interactions of water with bare and MLG-adsorbed Pt(111) substrates were investigated as a function of the substrate temperature and film thickness. During deposition of water molecules at 100 K, their free OH groups tend to be directed toward the substrate. The H-down water molecule is formed at the interface of the bare Pt(111) substrate not only during deposition of ASW at 100 K but also after its crystallization. However, this species is formed only at the very initial stage of water deposition, as estimated from the characteristic “ML peak” intensity of water TPD in comparison with the ASW ML determined based on the TOF−SIMS evolution curves. On the MLG/Pt(111) substrate, however, the H-down water species are formed preferentially during deposition at 100 K till the ASW ML is completed. Moreover, the second layer tends to reorient as well at T > Tg, suggesting that the interfacial structure propagates through the hydrogen-bonded water structures after the occurrence of water mobility. Probably, the local ordering of water molecules at the substrate interface is associated with hydrophobic hydration of MLG by ASW and LDL having crystal-like local structures. When water is deposited on the MLG/Pt(111) substrate at 125 K, a quasiliquid layer with H-down orientation is formed transiently together with crystallites. However, the quasi-liquid is finally absorbed by equilibrating crystallites, thereby leading to completely dewetted crystallites and bare MLG patches. The results using MLG/Pt(111) are fundamentally identical to those using HOPG. Consequently, the potential field of Pt(111) is not transmitted through the MLG layer (i.e., the occurrence of wettability opaqueness). Spotty RHEED patterns are observed by heating thin ASW films above 150 K, signifying that grains of ordered crystalline ices are formed epitaxially. The ice Ih crystallites grow preferentially on the bare Pt(111) surface, whereas grains of (111) oriented ice Ic are formed on the MLG/Pt(111) surface. For both cases, however, considerable stacking disorders are present. Randomly oriented crystallites are grown on both substrates when the initial ASW film thickness exceeds 10 ML, indicating that the substrate-induced nucleation is switched to spontaneous nucleation in the thin film interior. When water is deposited at 125 K, ice Ic grows preferentially on both bare and MLG-adsorbed Pt(111) substrates. The coexistence of 2D and 3D domains of water after crystallization is thought to be associated with premelting of crystallites. The quasi-liquid layer extended to the substrate is equilibrated with the premelting layer of crystallites, so that it plays a role in the ripening of preexisting crystals without further nucleation during water vapor deposition.

■

ACKNOWLEDGMENTS This research was partly funded by the Japan Society for the Promotion of Science through a Grant-in-Aid for Scientific Research (C) no. 22540339.

■

REFERENCES

(1) Thiel, P. A.; Madey, T. E. The interaction of water with solid surfaces: Fundamental aspects. Surf. Sci. Rep. 1987, 7, 211−385. (2) Henderson, M. The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited. Surf. Sci. Rep. 2002, 46, 1−308. (3) Verdaguer, A.; Sacha, G. M.; Bluhm, H.; Salmeron, M. Molecular Structure of Water at Interfaces: Wetting at the Nanometer Scale. Chem. Rev. 2006, 106, 1478−1510. (4) Hodgson, A.; Haq, S. Water Adsorption and the Wetting of Metal Surfaces. Surf. Sci. Rep. 2009, 64, 381−451. (5) Feibelman, P. J. Partial Dissociation of Water on Ru(0001). Science 2002, 295, 99−102. (6) Lilach, Y.; Iedama, M. J.; Cowin, J. P. Dissociation of Water Buried under Ice on Pt(111). Phys. Rev. Lett. 2007, 98, 016105. (7) Glebov, A.; Graham, A. P.; Menzel, A.; Toennies, J. P. Orientational Ordering of Two-Dimensional Ice on Pt(111). J. Chem. Phys. 1997, 106, 9382−9385. (8) Haq, S.; Harnett, J.; Hodgson, A. Growth of thin crystalline ice films on Pt(). Surf. Sci. 2002, 505, 171−182. (9) Nie, S.; Feibelman, P. J.; Bartelt, N. C.; Thürmer, K. Pentagons and Heptagons in the First Layer on Pt(111). Phys. Rev. Lett. 2010, 105, 026102. (10) Clay, C.; Haq, S.; Hodgson, A. Hydrogen Bonding in Mixed OH+H2O Overlayers on Pt(111). Phys. Rev. Lett. 2004, 92, 046102. (11) Ogasawara, H.; Brena, B.; Nordlund, D.; Nyberg, M.; Pelmenschikov, A.; Petterrsson, L. G. M.; Nilsson, A. Structure and Bonding of Water on Pt(111). Phys. Rev. Lett. 2002, 89, 276102. (12) Kimmel, G. A.; Petrik, N. G.; Dohnalek, Z.; Kay, B. D. Crystalline Ice Growth on Pt(111): Observation of a Hydrophobic Water Monolayer. Phys. Rev. Lett. 2005, 95, 166102. (13) Materer, N.; Starke, U.; Barbieri, A.; van Hove, M.; Somorjai, G. A.; Kroes, G. J.; Minot, C. Molecular Surface Structure of a LowTemperature Ice Ih(0001) Crystal. J. Phys. Chem. 1995, 99, 6267− 6269. (14) Souda, R. Substrate and Surfactant Effects on the Glass−Liquid Transition of Thin Water Films. J. Phys. Chem. B 2006, 110, 17524− 17530. (15) Souda, R. Nanoconfinement Effects of Water on Hydrophilic and Hydrophobic Substrates at Cryogenic Temperatures. J. Phys. Chem. C 2012, 116, 20895−20901. (16) Lee, C. Y.; McCammon, J. A.; Rossky, P. J. The Structure of Liquid Water at an Extended Hydrophobic Surface. J. Chem. Phys. 1984, 80, 4448−4455. (17) Ho, T. A.; Striolo, A. Polarizability effects in molecular dynamics simulations of the graphene-water interface. J. Chem. Phys. 2013, 138, 054117. (18) Rana, M. K.; Chandra, A. Ab Initio and Classical Molecular Dynamics Studies of the Structural and Dynamical Behavior of Water near a Hydrophobic Graphene Sheet. J. Chem. Phys. 2013, 138, 204702. (19) Singla, S.; Anim-Danso, E.; Islam, A. E.; Ngo, Y.; Kim, S. S.; Naik, R. R.; Dhinojwala, A. Insight on Structure of Water and Ice Next to Graphene Using Surface-Sensitive Spectroscopy. ACS Nano 2017, 11, 4899−4906. (20) Ohto, T.; Tada, H.; Nagata, Y. Structure and dynamics of water at water-graphene and water-hexagonal boron-nitride sheet interfaces revealed by ab initio sum-frequency generation spectroscopy. Phys. Chem. Chem. Phys. 2018, 20, 12979−12985.

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Phone: +81-29-8604429. *E-mail: [email protected]. Phone: +81-29-8604321. ORCID

Ryutaro Souda: 0000-0003-4769-9034 I


Article


Films: Implications for Self-Diffusivity. J. Phys. Chem. B 2006, 110, 17987−17997. (44) Smith, R. S.; Huang, C.; Wong, E. K. L.; Kay, B. D. The Molecular Volcano: Abrupt CCl4Desorption Driven by the Crystallization of Amorphous Solid Water. Phys. Rev. Lett. 1997, 79, 909−912. (45) Smith, R. S.; Huang, C.; Kay, B. D. Evidence for Molecular Translational Diffusion during the Crystallization of Amorphous Solid Water. J. Phys. Chem. B 1997, 101, 6123−6126. (46) Günster, J.; Souda, R. Water Condensation on a Hydrophobic Surface: A Structural Self-Trapping System. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 71, 041407. DOI: 10.1103/physrevb.71.041407 (47) Bolina, A. S.; Wolff, A. J.; Brown, W. A. Reflection Absorption Infrared Spectroscopy and Temperature-Programmed Desorption Studies of the Adsorption and Desorption of Amorphous and Crystalline Water on a Graphite Surface. J. Phys. Chem. B 2005, 109, 16836−16845. (48) Günster, J.; Souda, R. On the Wettability of Lipid DPPC Films. Langmuir 2006, 22, 6939−6943. (49) Ruan, C.-Y.; Lobastov, V. A.; Vigliotti, F.; Chen, S.; Zewail, A. H. Ultrafast Electron Crystallography of Interfacial Water. Science 2004, 304, 80−84. (50) Yang, D.-S.; Zewail, A. H. Ordered Water Structure at Hydrophobic Graphite Interfaces Observed by 4D, Ultrafast Electron Crystallography. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 4122−4126. (51) He, X.; Wu, C.; Yang, D.-S. Communication: No Guidance Needed: Ordered Structures and Transformations of Thin Methanol Ice on Hydrophobic Surfaces. J. Chem. Phys. 2016, 145, 171102. (52) Souda, R.; Aizawa, T. Crystallization Kinetics of Water on Graphite. Phys. Chem. Chem. Phys. 2018, 20, 21856−21863. (53) Jenniskens, P.; Banham, S. F.; Blake, D. F.; McCoustra, M. R. S. Liquid water in the domain of cubic crystalline ice Ic. J. Chem. Phys. 1997, 107, 1232−1241. (54) Backus, E. H. G.; Grecea, M. L.; Kleyn, A. W.; Bonn, M. Surface Crystallization of Amorphous Solid Water. Phys. Rev. Lett. 2004, 92, 236101. (55) Thürmer, K.; Bartelt, N. C. Growth of Multilayer Ice Films and the Formation of Cubic Ice Imaged with STM. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 195425. (56) Malkin, T. L.; Murray, B. J.; Brukhno, A. V.; Anwar, J.; Salzmann, C. G. Structure of Ice Crystallized from Supercooled Water. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 1041−1045. (57) Aizawa, T.; Hwang, Y.; Hayami, W.; Souda, R.; Otani, S.; Ishizawa, Y. Phonon dispersion of monolayer graphite on Pt(111) and NbC surfaces: bond softening and interface structures. Surf. Sci. 1992, 260, 311−318. (58) Yu, M. L.; Mann, K. Bond Breaking and the Ionization of Sputtered Atoms. Phys. Rev. Lett. 1986, 57, 1476−1479. (59) Günster, J.; Höfft, O.; Krischok, S.; Souda, R. A Time-of-Flight Secondary Ion Mass Spectroscopy Study of 1-Ethyl-3methylimidazolium Bis(trifluoromethylsulfonyl)imide RT-Ionic Liquid. Surf. Sci. 2002, 602, 3403−3407. (60) Thürmer, K.; Bartelt, N. C. Nucleation Limited Dewetting of Ice Films on Pt(111). Phys. Rev. Lett. 2008, 100, 186101. (61) Braun, J.; Glebov, A.; Graham, A. P.; Menzel, A.; Toennies, J. P. Structure and Phonons of the Ice Surface. Phys. Rev. Lett. 1998, 80, 2638−2641. (62) Wautelet, M. Estimation of the variation of the melting temperature with the size of small particles, on the basis of a surfacephonon instability model. J. Phys. D: Appl. Phys. 1991, 24, 343−346. (63) Cheng, H.-P.; Berry, R. S. Surface Melting of Clusters and Implications for Bulk Matter. Phys. Rev. A 1992, 45, 7969−7980. (64) Dohnálek, Z.; Kimmel, G. A.; Ciolli, R. L.; Stevenson, K. P.; Smith, R. S.; Kay, B. D. The Effect of the Underlying Substrate on the Crystallization Kinetics of Dense Amorphous Solid Water Films. J. Chem. Phys. 2000, 112, 5932−5941.

(21) Cicero, G.; Grossman, J. C.; Schwegler, E.; Gygi, F.; Galli, G. Water Confined in Nanotubes and between Graphene Sheets: A First Principle Study. J. Am. Chem. Soc. 2008, 130, 1871−1878. (22) Bratko, D.; Daub, C. D.; Leung, K.; Luzar, A. Effect of Field Direction on Electrowetting in a Nanopore. J. Am. Chem. Soc. 2007, 129, 2504−2510. (23) von Domaros, M.; Bratko, D.; Kirchner, B.; Luzar, A. Dynamics at a Janus Interface. J. Phys. Chem. C 2013, 117, 4561−4567. (24) Rafiee, J.; Mi, X.; Gullapalli, H.; Thomas, A. V.; Yavari, F.; Shi, Y.; Ajayan, P. M.; Koratkar, N. A. Wetting Transparency of Graphene. Nat. Mater. 2012, 11, 217−222. (25) Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P.; Li, L.; Liu, H. Effect of airborne contaminants on the wettability of supported graphene and graphite. Nat. Mater. 2013, 12, 925−931. (26) Lai, C.-Y.; Tang, T.-C.; Amadei, C. A.; Marsden, A. J.; Verdaguer, A.; Wilson, N.; Chiesa, M. A Nanoscopic Approach to Studying Evolution in Graphene Wettability. Carbon 2014, 80, 784− 792. (27) Shih, C.-J.; Wang, Q. H.; Lin, S.; Park, K.-C.; Jin, Z.; Strano, M. S.; Blankschtein, D. Breakdown in the Wetting Transparency of Graphene. Phys. Rev. Lett. 2012, 109, 176101. (28) Shih, C.-J.; Strano, M. S.; Blankschtein, D. Wetting Translucency of Graphene. Nat. Mater. 2013, 12, 866−869. (29) Belyaeva, L. A.; van Deursen, P. M. G.; Barbetsea, K. I.; Schneider, G. F. Hydrophilicity of Graphene in Water through Transparency to Polar and Dispersive Interactions. Adv. Mater. 2018, 30, 1703274. (30) Kimmel, G. A.; Matthiesen, J.; Baer, M.; Mundy, C. J.; Petrik, N. G.; Smith, R. S.; Dohnálek, Z.; Kay, B. D. No Confinement Needed: Observation of a Metastable Hydrophobic Wetting TwoLayer Ice on Graphene. J. Am. Chem. Soc. 2009, 131, 12838−12844. (31) Koga, K.; Zeng, X. C.; Tanaka, H. Freezing of Confined Water: A Bilayer Ice Phase in Hydrophobic Nanopores. Phys. Rev. Lett. 1997, 79, 5262−5265. (32) Kim, Y.; Cruz, S. S.; Lee, K.; Alawode, B. O.; Choi, C.; Song, Y.; Johnson, J. M.; Heidelberger, C.; Kong, W.; Choi, S.; et al. Remote Epitaxy through Graphene Enables Two-Dimensional Material-Based Layer Transfer. Nature 2017, 544, 340−343. (33) Johari, G. P.; Hallbrucker, A.; Mayer, E. The glass-liquid transition of hyperquenched water. Nature 1987, 330, 552−553. (34) Souda, R. Glass Transition and Intermixing of Amorphous Water and Methanol. Phys. Rev. Lett. 2004, 93, 235502. (35) Mishima, O.; Stanley, H. E. The Relationship between Liquid, Supercooled and Glassy Water. Nature 1998, 396, 329−335. (36) Finney, J. L.; Hallbrucker, A.; Kohl, I.; Soper, A. K.; Bowron, D. T. Structures of High and Low Density Amorphous Ice by Neutron Diffraction. Phys. Rev. Lett. 2002, 88, 225503. (37) Souda, R. Roles of 2D Liquid in Reduction of the GlassTransition Temperature of Thin Molecular Solid Films. J. Phys. Chem. C 2011, 115, 8136−8143. (38) Souda, R. Interfacial Reaction of Water Ice on Polycrystalline Vanadium and Its Effects on Thermal Desorption of Water. Phys. Chem. Chem. Phys. 2014, 16, 1095−1100. (39) Souda, R. Phase Transition of Thin Water Films on Graphite Probed by Interactions with LiCl Additives. J. Phys. Chem. C 2017, 121, 12199−12205. (40) Smith, R. S.; Huang, C.; Wong, E. K. L.; Kay, B. D. Desorption and Crystallization Kinetics in Nanoscale Thin Films of Amorphous Water Ice. Surf. Sci. 1996, 367, L13−L18. (41) Löfgren, P.; Ahlström, P.; Chakarov, D. V.; Lausmaa, J.; Kasemo, B. Substrate Dependent Sublimation Kinetics of Mesoscopic Ice Films. Surf. Sci. 1996, 367, L19−L25. (42) Löfgren, P.; Ahlström, P.; Lausma, J.; Kasemo, B.; Chakarov, D. Crystallization Kinetics of Thin Amorphous Water Films on Surfaces. Langmuir 2003, 19, 265−274. (43) McClure, S. M.; Barlow, E. T.; Akin, M. C.; Safarik, D. J.; Truskett, T. M.; Mullins, C. B. Transport in Amorphous Solid Water J


Article

The Journal of Physical Chemistry C (65) Sanfelix, P. C.; Holloway, S.; Kolasinski, K. W.; Darling, G. R. The Structure of Water on the (0001) Surface of Graphite. Surf. Sci. 2003, 532−5352, 166−172.

K


Wettability of Bare and Graphene-Adsorbed Pt(111) during Glass

Recommend Documents