Construction of Flexible Substrates Based on Transition Metal Nitrides for Ultrasensitive SERS Analysis

Flexible transition metal nitrides (TMNs) are considered key candidate materials for constructing next-generation high-performance flexible sensing devices. However, their strong metal-nitrogen bonds require high-temperature synthesis, which tends to cause spontaneous aggregation into three-dimensional bulk materials, making it difficult to obtain ultrathin two-dimensional materials suitable for flexible devices. This study proposes an innovative rapid and nondestructive microwave crystallization method. By ingeniously leveraging the abundant free electrons in quasi-metallic TMN nanostructures, electromagnetic irradiation induces efficient microwave heating, achieving exceptional crystallization within 20 s. This method effectively circumvents the sintering of ultrathin nanostructures inherent to conventional high-temperature annealing and increases the specific surface area of the product by more than 10-fold. Based on this method, dense and robust flexible TMN films with ultrahigh specific surface area and excellent chemical stability have been successfully obtained, enabling highly sensitive surface-enhanced Raman spectroscopy (SERS) detection of polycyclic aromatic hydrocarbons and nanoplastics.