Synthesis and characterization of ultrafine γ-Al₂O₃:Cr nanoparticles and their performance in antibacterial activity

Preventing the growth of potentially deadly bacteria by newly synthesized nanoparticles (NPs) is of great importance in the development of future drugs. Here, chromium-doped alumina (Al₂O₃:Cr) NPs with an average diameter of about 6 nm were synthesized by a novel combination of chemical and sol–gel methods, followed by their calcination at different temperatures. The antibacterial properties of the resulting non-porous NPs were evaluated by the decomposition of two detectors (anthracene and methylene blue), and biofilms with five different concentrations (0−100 mg/mL), while also investigating structural, chemical, morphological and optical properties. Scanning and transmission electron microscopic analyses, along with X-ray diffraction patterns of the Al₂O₃:Cr NPs revealed ultrafine crystalline particulates with spherical-like morphology. Moreover, the formation of Al–O chemical bonds, and an optical band gap of 3.07 eV were evidenced. Antibacterial activity of the γ-Al₂O₃:Cr NPs calcined at 800 °C showed high inhibitions of 60% and 61% against S.aureus and P.aeruginosa microorganisms at a minimum inhibitory concentration of 100 mg/mL, indicating their potential use in the decomposition of gram-positive and gram-negative biofilms, respectively.