Advances in Atomic Force Microscopy: Weakly Perturbative Imaging of the Interfacial Water

Abstract

The structure and dynamics of interfacial water, determined by the water-interface interactions, are important for a wide range of applied fields and natural processes, such as water diffusion (Kim et al., 2013), electrochemistry (Markovic, 2013), heterogeneous catalysis (Over et al., 2000), and lubrication (Zilibotti et al., 2013). The precise understanding of water-interface interactions largely relies on the development of atomic-scale experimental techniques (Guo et al., 2014) and computational methods (Hapala et al., 2014b). Scanning probe microscopy has been extensively applied to probe interfacial water in many interdisciplinary fields (Ichii et al., 2012; Shiotari and Sugimoto, 2017; Peng et al., 2018a). In this perspective, we review the recent progress in the noncontact atomic force microscopy (nc-AFM) imaging and AFM simulation techniques and discuss how the newly developed techniques are applied to study the properties of interfacial water. The nc-AFM with the quadrupole-like CO-terminated tip can achieve ultrahigh-resolution imaging of the interfacial water on different surfaces, trace the reconstruction of H-bonding network and determine the intrinsic structures of the weakly bonded water clusters and even their metastable states. In the end, we present an outlook on the directions of future AFM studies of interfacial water as well as the challenges faced by this field.

Molecular Features of Hydration Layers: Insights from Simulation, Microscopy, and Spectroscopy

“…44 With a carbon monoxide (CO)-functionalized tip, Cao et al traced the reconstruction of H-bonds and determined the structures of the weakly bonded water clusters and their metastable states. 32 One can precisely define a tip in an MD simulation of AFM, facilitating the molecular interpretation of AFM. Miyazawa et al examined the effects of the tip on an AFM image by simulating three different functionalized tips: two calcite tips terminated by Ca 2+ and CO 3 2− and a silica tip terminated in a single silanol group (referred to as Ca, CO 3 , and OH tips, respectively, in Figure 4).…”

“…AFM has been a principal tool for investigating the molecular structure of a hydration layer. AFM imaging of the hydration layers on solids with an atomic resolution has been reviewed by Peng et al Cao et al went over the recent progress in the noncontact AFM imaging of the solid–water interfaces by utilizing functionalized tips. In a frequency modulation (FM) mode, an AFM tip oscillates at a specific frequency, and the changes in the frequency and amplitude of the cantilever are detected .…”

“…Recently, a functionalized tip was used to give an AFM imaging with high resolution. , With an OH-functionalized tip, Wagner et al probed the acidities of individual hydroxyl groups of an indium oxide surface . With a carbon monoxide (CO)-functionalized tip, Cao et al traced the reconstruction of H-bonds and determined the structures of the weakly bonded water clusters and their metastable states . One can precisely define a tip in an MD simulation of AFM, facilitating the molecular interpretation of AFM.…”

“…Instead, we present our perspective on how molecular simulation, if combined with AFM and VSFG experiments, corroborates our understanding of the molecular structural dynamics of a hydration layer. For in-depth reviews on AFM and VSFG experiments, readers are referred to the articles by Peng et al, 11 Cao et al, 32 Backus et al, 33 Tang et al, 22 and Yamaguchi and Otosu. 26 In Section 2, we discuss how AFM and simulation can elucidate the molecular structures of hydration layers.…”

Advances in Atomic Force Microscopy: Imaging of Two- and Three-Dimensional Interfacial Water

“…Until now, AFM imaging, together with ab initio calculation, classical molecular dynamics (MD) calculation and AFM simulation, has been applied to the investigation of the interfacial water on a wide variety of substrates, such as minerals ( Putnis, 2014 ), biomolecules ( Maver et al, 2016 ; Dufrene et al, 2017 ), and organic films ( Verma and Sharma, 2010 ). Previously, we introduced the development of AFM technique both in experiments and simulations, as well as their applications in the study of interfacial water, with particular emphasis on the detection of the nanoclusters and one-dimensional chains ( Cao et al, 2019 ). As a continuation, this perspective reviews the latest progresses in the utilization of AFM imaging in 2D and 3D interfacial water, including adsorbed water networks and electrolytes, as well as their growth processes.…”