Polymer-guided grafting of single W atoms onto titanate nanotubes increases SERS activity in semiconductors

Metal single atoms have been demonstrated to induce surface-enhanced Raman scattering (SERS) due to their effectiveness in the modification of electronic structure. However, precisely modulating the relative positions of metal single atoms on sub-nanolattices remains a formidable challenge, which makes SERS studies of metal single atoms dependent on localized environments still lacking. Herein, we rely on polyethylene glycol (PEG) as a soft template to achieve the modulation of the relative positions of W atoms on titanate nanotubes (W-TNTs) and probe the local-environment-dependent SERS induced by metal single atoms based on this technique. We find that the relative position of the W single atoms greatly affects their SERS performance. This phenomenon has been attributed to the difference in charge transfer ability between single W atoms of different configurations, with isolated W atoms inducing a significantly higher density of electronic states near the Fermi energy than associated W atoms, leading to an enhanced polarization of the probe molecule and subsequently a stronger Raman signal. Our findings demonstrate a technique to effectively control the relative positions of single atoms and provide insights into single-atom-induced SERS associated with localized environments, which will facilitate the rational design of SERS substrates based on metal single atoms.