Pomegranate-derived phosphorus, nitrogen-doped carbon nanoflower/nanofiber hybrids and quasi-spherical dot stabilized Pickering emulsions with low-DS amphiphilic CMC for dual-mode detection of pathogenic bacteria and their metabolic pH signatures.

This study introduces a sustainable dual-waste valorization strategy, transforming agricultural residues (e.g. pomegranate skin and sugarcane bagasse) into a multifunctional smart diagnostic platform for the real-time detection of pathogenic bacteria. Utilizing a microwave-assisted hydrothermal route, we engineered a morphological evolution from quasi-spherical nitrogen-doped carbon dots (NCQDs) to hierarchical phosphorus and nitrogen co-doped carbon nanoflower/fiber hybrids (PNCNFs). The strategic introduction of phosphorus induced lattice strain and electronic reconfiguration, resulting in a significant increase in the hydrophilic-lipophilic balance (HLB) from 5.57 to 8.95. This elevated HLB, coupled with a tailored low-degree of substitution (DS 0.4) carboxymethyl cellulose (CMC) from bagasse, optimized the stability of Pickering nanoemulsions at the rosemary essential oil/water interface. The PNCNF hybrids demonstrated a superior surface-to-volume ratio, facilitating high-density functional site accessibility for dual-mode sensing. This platform provided synchronized colorimetric and fluorometric responses to the metabolic pH signatures of Escherichia coli and Staphylococcus aureus. DFT calculations and fluorescence dynamics confirmed that the P,N-doped framework possesses high kinetic reactivity and a pH-switchable electronic structure. Beyond detection, the system showed enhanced antibacterial efficacy through the synergistic action of the hierarchical petals and encapsulated bio-actives. This research demonstrates that the controlled manipulation of biomass-derived molecular precursors provides a viable pathway for developing multifunctional nanophotonic sensors, with potential applications for real-time monitoring in food safety and clinical diagnostics.