This study aims to explore innovative approaches for synthesizing ultra-fine ceria nanoparticles by employing diverse assisted-sol-gel syntheses such as microwave, sonochemical, reflux, and heating methods and a comparative property assessment of the resultant nanoparticles. The physicochemical properties of the synthesized nanoparticles were analyzed including, crystallinity, crystallite size, bonding characteristics, reflectance, band gap, optical emission, nanoparticle size, morphology, and surface charge features. Highly crystalline, structurally pure, spherical-shaped, positively charged CeO2 nanoparticles were obtained in all the synthesis methods. Among the four methods, notable outcomes were given by cerium dioxide (CeO2) nanoparticles synthesized via a microwave-assisted sol-gel method. These nanoparticles feature nanocrystalline structures with additional monodisperse quantum dot formations of size 3 +/- 1.5 nm, distinguished by a band gap of approximately 3.05 eV, BET surface area of 76 m(2)/g and a prominent blue emission band at around 464 nm. Antibacterial assays unveiled the remarkable inhibitory effects of microwave-synthesized CeO2 nanoparticles against gram-negative bacteria, including E. coli and P. aeruginosa. In the quest for targeted antibacterial agents, this narrow-spectrum bactericidal activity highlights the potential of these nanoparticles as targeted antibacterial agents, offering promising avenues for combating infections caused by Gram-negative bacterial strains.