N, S co-doped porous carbon nanosheet foam as MALDI matrix for efficient and direct profiling of biomolecules and environmental contaminants

Abstract

It is still urgent to develop a powerful method for high-throughput and sensitive analysis of various small biomolecules and environmental contaminants. Herein, a three-dimensional foam consisting of nitrogen and sulfur co-doped porous carbon (N, S-C) nanosheet synthesized was served as an excellent matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) efficiently and directly detecting various small biomolecules and pollutant compounds. This N, S-C nanosheet possessed the advantages of carbon foam for resonant chamber, high-contents of N/S heteroatoms co-doping, large surface area, hierarchical pore and good UV absorption. The use of N, S-C matrix could exhibit higher MS intensities, lower background noise, better salt tolerance and higher sensitivity for probing the various analytes, much superior to the traditional CHCA (α-cyano-4-hydroxycinnamic acid) matrix and control materials (C and N-C). The limit of detection (LOD)s of 1-hydroxy-pyrene, 4-nitrocatechol and nitroguaiacol were calculated to be 0.1 μg/mL, 1 μg/mL and 8 μg/mL at a signal-to-noise ratio (S/N) of 3. Moreover, the rapid and precise detections of 4-nitrocatechol, nitroguaiacol, and 1-hydroxy-pyrene in PM2.5 real sample have also been achieved. Through density functional theory (DFT) simulations, we reveal the sensing mechanism of small molecular deprotonation with the N and S co-doping into carbon matrix. This work may be promising to provide an excellent carbon matrix for the analysis of MALDI-TOF MS method in the biological and environmental field.