Interfaces at the
nanoscale, also called nanointerfaces,
play a
fundamental role in physics and chemistry. Probing the chemical and
electronic environment at nanointerfaces is essential in order to
elucidate chemical processes relevant for applications in a variety
of fields. Many spectroscopic techniques have been applied for this
purpose, although some approaches are more appropriate than others
depending on the type of the nanointerface and the physical properties
of the different phases. In this Perspective, we introduce the major
concepts to be considered when characterizing nanointerfaces. In particular,
the interplay between the characteristic length of the nanointerfaces,
and the probing and information depths of different spectroscopy techniques
is discussed. Differences between nano- and bulk interfaces are explained
and illustrated with chosen examples from optical and X-ray spectroscopies,
focusing on solid–liquid nanointerfaces. We hope that this
Perspective will help to prepare spectroscopic characterization of
nanointerfaces and stimulate interest in the development of new spectroscopic
techniques adapted to the nanointerfaces.