A highly simple and controllable nitrogen-doping method for carbon-based surface-enhanced Raman spectroscopy substrates

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive tool for label-free chemical analysis. Recently, carbon-based SERS substrates have gained preference over traditional metal-based ones because they possess uniform signal enhancement distribution, high biocompatibility, robust chemical stability, enhanced adsorption capacity, and high durability attributed to their reduced photothermal conversion. An important strategy for improving the SERS performance of carbon-based substrates is the incorporation of heteroatoms, particularly nitrogen (N). However, traditional N-doping methods are often complex and difficult to control. To address this challenge, we developed a simple and controllable N-doping method for preparing carbon-based SERS substrates. This method specifically manipulates N doping and expands the conjugated π-electron system in polyacrylonitrile (PAN)-based substrates by adjusting the pyrolysis temperature (up to 1200 °C) within a low vacuum environment (0.2 Pa) over a brief period (2 min). Interestingly, our PAN-based substrates, enriched with N atoms, demonstrated 7.5-20 times stronger Raman signal enhancement than graphite substrates commonly used in SERS experiments. This innovative fabrication method is expected to broaden the practical use of SERS substrates in various sensing applications.