Nanoparticles (NPs) of CuBi2O4 with an average size around 25 nm were obtained by a novel and eco-friendly synthesis method. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) reveal that CuBi2O4 NPs possess a tetragonal crystal structure. These NPs were characterised by Raman scattering, ultraviolet-visible (UV-Vis) absorption, photoluminescence (PL), and electron paramagnetic resonance (EPR) spectroscopies. Furthermore, an in vitro study of the antibacterial effect of CuBi2O4 NPs against two bacterial strains, Pseudomonas aeruginosa (ATCC 43636) and Staphylococcus aureus (ATCC 25923), was carried out. The results obtained from the counting of colony-forming units (CFUs) and by the XTT-PMS cell viability assay showed an inhibition of the bacterial growth by 88%–87% for P. aeruginosa and 100% for S. aureus, at 50 mg ml−1 of NPs concentration. The results of this work suggest that these nanoparticles have the potential to be used as antibacterial agents by embedding them into different surfaces or being dispersed in a coating, to prevent the bacterial colonisation.

This work presents the deposition and study of the semiconductor behavior of CuBi2O4 nanoparticles (NPs) with an average crystallite size of 24 ± 2 nm embedded in poly(3,4 ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) films. The CuBi2O4 NP bandgap was estimated at 1.7 eV, while for the composite film, it was estimated at 2.1 eV, due to PEDOT:PSS and the heterojunction between the polymer and the NPs. The charge transport of the glass/ITO/PEDOT:PSS-CuBi2O4 NP/Ag system was studied under light and dark conditions by means of current–voltage (I–V) characteristic curves. In natural-light conditions, the CuBi2O4 NPs presented electric behavior characterized by three different mechanisms: at low voltages, the behavior follows Ohm’s law; when the voltage increases, charge transport occurs by diffusion between the NP–polymer interfaces; and at higher voltages, it occurs due to the current being dominated by the saturation region. Due to their crystalline structure, their low bandgap in films and the feasibility of integrating them as components in composite films with PEDOT:PSS, CuBi2O4 NPs can be used as parts in optoelectronic devices.