*Article* **Photocatalytic Degradation of Fluoroquinolone Antibiotics in Solution by Au@ZnO-rGO-gC3N<sup>4</sup> Composites**

**Abniel Machín 1,\* , Kenneth Fontánez <sup>2</sup> , José Duconge <sup>3</sup> , María C. Cotto <sup>3</sup> , Florian I. Petrescu <sup>4</sup> , Carmen Morant <sup>5</sup> and Francisco Márquez 3,\***


**Abstract:** The photocatalytic degradation of two quinolone-type antibiotics (ciprofloxacin and levofloxacin) in aqueous solution was studied, using catalysts based on ZnO nanoparticles, which were synthesized by a thermal procedure. The efficiency of ZnO was subsequently optimized by incorporating different co-catalysts of gC3N<sup>4</sup> , reduced graphene oxide, and nanoparticles of gold. The catalysts were fully characterized by electron microscopy (TEM and SEM), XPS, XRD, Raman, and BET surface area. The most efficient catalyst was 10%Au@ZnONPs-3%rGO-3%gC3N<sup>4</sup> , obtaining degradations of both pollutants above 96%. This catalyst has the largest specific area, and its activity was related to a synergistic effect, involving factors such as the surface of the material and the ability to absorb radiation in the visible region, mainly produced by the incorporation of rGO and gC3N<sup>4</sup> in the semiconductor. The use of different scavengers during the catalytic process, was used to establish the possible photodegradation mechanism of both antibiotics.

**Keywords:** ciprofloxacin; levofloxacin; ZnO; gC3N<sup>4</sup> ; rGO; Au nanoparticles
