Carbonized polymer dots for discrimination of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol

It is of great significance for the discrimination of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP) from their analogues. Here, based on the electron-deficient properties of TNT and TNP, a series of o-phenylenediamine/polyethyleneimine carbonized polymer dots (OPD/PEI CPDs) with different densities and types of amine groups (-NH₂) on the surface were designed by modulating the ratio of the precursors OPD and PEI. The surface -NH₂ group of OPD/PEI CPDs could form a Meisenheimer complex with TNT, triggering the Forster resonance energy transfer, while forming hydrogen bonds with hydroxyl in TNP, triggering the charge transfer and spectral overlap to produce photoinduced electron transfer accompanied with inner filter effect. When the ratio of OPD to PEI is 1:1 and the surface -NH₂ content is 26.06 %, the OPD/PEI₁ CPDs demonstrated a more superior sensing performance toward targets, including a low limit of detection (TNT: 324 nM and 255 µM, TNP: 21.08 nM and 318.6 nM), a rapid response (<1 s), and a rather good selectivity in the presence of 20 interferents. Moreover, the practicality of the OPD/PEI₁ CPDs was further verified by an OPD/PEI₁ CPDs-based paper sensor, which is capable of discriminating TNT and TNP particles and vapors as low as pg-level and ppm-level respectively.