The Design of WTe₂/Graphene/Ag NPs Heterostructure for the Improvement of the Chemical Enhancement in SERS

Combining the advantages of metal and two-dimensional (2D) nanomaterials, various 2D/metal composite structures are proposed as surface-enhanced Raman spectroscopy (SERS) substrates. However, the chemical enhancement in the composite structure is usually less responsible for the total enhancement. In this work, we proposed a heterostructure including WTe₂/graphene/Ag nanoparticles (WTe₂/Gr/Ag) as an effective platform for SERS. The matching of energy levels facilitates charge transfer (CT) within the composite structure, which in turn significantly improves the chemical enhancement of SERS. Compared with WTe₂/Ag or Gr/Ag substrate, the SERS signals can be amplified up to 18-fold, and the detection limit could further reduce 3 orders of magnitude. Furthermore, the CT process in the SERS test can be further promoted after introducing the pyroelectric field based on the ferro-electricity of WTe₂. The enhancement factor of the WTe₂/Gr/Ag substrate finally reached 1.34 × 10¹². This work proposes a new idea for the design of highly sensitive SERS sensors.