6,13-Pentacenequinone (PQ)-CuO nanocomposites for sunlight-driven dye degradation: first evidence of PQ as an...

CuO-PQ nanocomposites with 0.5 (CP 0.5), 1.0 (CP 1.0) and 1.5 wt% (CP 1.5) of PQ were prepared using a wet impregnation route and assessed for sunlight driven dye degradation and antibacterial activity. Powder X-ray diffraction confirmed pristine monoclinic CuO together with characteristic PQ reflections in the composites. UV-vis diffuse reflectance spectroscopy showed progressive band gap narrowing from 2.32 eV for CuO to 1.75, 1.68 and 1.63 eV for CP 0.5, CP 1.0 and CP 1.5, respectively, thereby increasing visible light absorption. CP 0.5 exhibited the highest photocatalytic performance, increasing the apparent rate constants for rhodamine 6G, methylene blue and safranine from 1.80 × 10^-3, 2.40 × 10^-3 and 3.92 × 10^-3 min^-1 for bare CuO to 1.03 × 10^-2, 5.40 × 10^-3 and 1.44 × 10^-2 min^-1, respectively. In antibacterial tests against Escherichia coli (EC), Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA), the CuO-PQ composites displayed significantly higher inhibition zones than CuO alone, reaching up to 27 mm for CP 1.0 and CP 1.5 against SA. While PQ has previously been incorporated into photocatalytic systems, its intrinsic antimicrobial activity has, to the best of our knowledge, not been reported earlier. In the current work we show that PQ acts as an antimicrobial active component within CuO-PQ nanocomposites. The improved dual functionality is attributed to interfacial coupling between CuO and PQ, which broadens the visible light response, promotes charge separation and enables more efficient generation of reactive oxygen species (ROS) under sunlight.