Table 1.

Commonly used in situ techniques for the molecular-level surface characterization

Techniques	Properties characterized
Transmission electron microscopy (TEM)	Surface/interface structure, the size, shape, and crystallinity of nanocrystals
X-ray diffraction (XRD)	Structure of micro- and mesoporous materials
Surface X-ray diffraction (SXRD)	Surface structure
Ambient pressure X-ray photoelectron spectroscopy (AP-XPS)	Surface chemical composition
Small Angle X-ray scattering (SAXS)	Characteristic distances of ordered nanomaterials
X-ray emission spectroscopy (XES)	Electronic structure of surfaces
Near-edge X-ray absorption fine structure (NEXAFS)	Surface chemical composition
Extended X-ray Absorption fine structure (EXAFS)	Chemical composition and bonding environment of nanoparticles
Polarization-modulated reflection–absorption infrared spectroscopy (PM–RAIRS)	Surface reaction intermediates
Surface enhanced Raman spectroscopy (SERS)	Surface reaction intermediates
Sum frequency generation spectroscopy (SFG)	Surface reaction intermediates
High pressure scanning tunneling microscopy (HP-STM)	Surface morphology and electronic structure
Atomic force microscopy (AFM)	Surface morphology, tribological properties, and work function