Directly Convert Carbonaceous Microspheres to Three-Dimensional Porous Carbon Microspheres with a Robust Self-Supporting Structure as a Metal-Free SERS Substrate for Online High- Throughput Analysis

It is of great significance for practical applications to directly convert readily available biomass carbon into threedimensional (3D) porous carbon microspheres with a selfsupporting structure. Herein, we report the convenient conversion of biomass carbon microspheres to hierarchical porous carbon microspheres (HP-CMSs) with a robust self-supporting framework structure. A general SiO2-induced etching mechanism is proposed for the formation of the HP-CMSs. Benefiting from this robust 3D self-supporting frame structure, these HP-CMSs have outstanding mechanical, chemical, and thermal stability. As a metal-free surface enhanced Raman scattering (SERS) substrate with an ultrahigh specific surface area (4216 m2 g-1) and a high density of active sites, the HP-CMSs exhibit high sensitivity with a detection limit of 10-10 M and a Raman enhancement factor of 3.5 x 106. By integrating the enrichment and sensing functions of the HP-CMSs in a microfluidic channel, online high-throughput SERS detection of 20 samples within 5 min is achieved in a single channel, and the relative standard deviation of the signals between samples is only 5.1%. The current work develops a convenient preparation method that converts sustainable biomass carbon to 3D hierarchical porous carbon and provides a potential material for sensing, energy, catalysis, and other fields.