Growth and Characterization of Myristic Acid Crystals Doped with Co and Cu and Microbiological Assays for Potential Antimicrobial Applications

In this study, pure myristic acid (MA) polycrystals and those doped with Co and Cu were synthesized and characterized to evaluate their structural features, thermal properties, and antimicrobial effects against the bacterium Xanthomonas citri. Scanning electron microscopy revealed that doping with Co and Cu altered the crystal surfaces. Specifically, pure MA polycrystals exhibited rougher and more porous surfaces, whereas Co and Cu doped MA polycrystals displayed more compact and less porous morphologies. Energy-dispersive X-ray spectroscopy confirmed the presence of Co and Cu in the samples. X-ray diffraction indicated that all samples crystallized in the same monoclinic structure; however, Co and Cu doping led to a slight decrease in unit cell volume and average crystallite size. Raman spectroscopy revealed changes in the vibrational bands of the crystalline lattice. Thermal analyses demonstrated that the addition of Co and Cu ions influenced the thermal stability of pure MA. In microbiological assays, all samples exhibited antimicrobial activity against X. citri. In particular, Co-doped MA polycrystals showed bactericidal properties at all tested concentrations, while pure MA polycrystals exhibited bacteriostatic action at lower concentrations (≤15.6 µg/mL) and bactericidal action at higher concentrations. Cu-doped MA polycrystals did not inhibit bacterial growth at lower concentrations (7.8 µg/mL) but were bactericidal at higher concentrations. These results demonstrated increased lethality against X. citri, particularly for Co-doped MA polycrystals, which exhibited the lowest LD50 value (the toxicological dose required to inhibit 50% of the tested population). Overall, these findings indicate that metal-doped MA polycrystals may be effective for future antimicrobial applications.