Structure-efficiency relationships and mechanism in carbon quantum dots-shewanella hybrid biogenic fenton systems

Biogenic Fenton systems (BFS) show promise for removing emerging contaminants. Incorporating carbon quantum dots (CDs) offers a viable strategy to enhance its performance, yet the structure-efficiency relationships remain unclear. Herein, citrate-based CDs were synthesized via orthogonal design. The optimal CDs (313) degraded 90 ± 1% of the index pollutant 1,4-dioxane within 60  h, versus 70 ± 3% for BFS without CDs, whereas NaBH₄-reduced CDs suppressed degradation below the control. Structure analyses identified high graphitization degree, graphitic N and CO as key structural features. CDs (313) enhanced extracellular electron transfer by improving flavin biosynthesis (∼20%) and electrochemical performance, subsequently facilitating Fe²⁺ generation (1.15-fold) and ·OH production (1.17-fold). Adenosine triphosphate and intracellular electron generation were elevated 1.28-fold and 1.43-fold, respectively. Proteomics revealed upregulation of thiamine biosynthesis, biofilm formation, and sulfur/nitrogen metabolism. From an application perspective, CDs (313) reduced lactate requirement by 50% (5  mM lactate with CDs achieved comparable degradation to 10  mM without CDs). Light stimulation further improved BFS performance. Collectively, this work integrates structure-efficiency relationship and proteomic mechanism, providing a foundation for rational design of CDs--assisted BFS.