High-Resolution Mapping Nanoscale Hydrophobicity for Fine Structures and Dynamic Evolution of Nanomaterial Surface

Nanomaterial hydrophobicity plays a critical role in interfacial phenomena ranging from biological toxicity to chemical reactions. However, it is difficult to figure out the high-resolution surface hydrophobicity at the nanoscale. Herein, a chemical force microscopy is demonstrated to profile in situ hydrophobicity images with the nanoscale resolution, exhibiting order-of-magnitude gain than the traditional methods. This method is utilized to rapidly recognize the spatial fine structure hydrophobicity on Au, graphite, mica, and graphene oxides (GO), enabling the recognition of complicated substances and structures. It is found that the hydrophobicity of GO is opaque and is independent of stacking thickness, which is entirely different from the original graphene. Especially, the regions of wrinkles/edges are first proved to be generally less attractive to the hydrophobic probe than flat areas. This method is used to observe the dynamic evolution of GO hydrophobicity in different aqueous conditions, and is capable of detecting local oxidation variation during interfacial reactions.