Elucidation of Tip-Broadening Effect in Tip-Enhanced Raman Spectroscopy (TERS): A Cause of Artifacts or Potential for 3D TERS

The tip-broadening effect (TBE), which makes the apparent dimensions of the imaged objects larger than they truly are, is one of the major disadvantages of atomic force microscope-related technique, like tip-enhanced Raman spectroscopy (TERS). However, the TBE also provides an opportunity to achieve three-dimensional (3D) TERS if the plasmonically active zones located at the shaft of the used tip. Herein, we found that the side part of the p-nitrothiophenol (pNTP)-modified Au microplates (AuMPs) can be observed when TBE exists. Moreover, the 3D TERS feature was applied to monitor reduction species of pNTP catalyzed by Au microplates (AuMPs). Our results showed that the 3D TERS is capable of distinguishing signals from both the side and top part in a single piece of AuMP, corresponding to Au{100} or Au{110} with low catalytic activity and Au{111} with higher catalytic activity, respectively.