Synthesis of Fe₃O₄–<i>Zingiber officinale</i> extract/ZnO/OA/DMSO ferrofluid as antimicrobial agent

Abstract In recent years, the problem of antibiotic resistance has emerged as a significant public health concern. The growing prevalence of antibiotic-resistant microbes hinders the efficacy of these drugs in treating microbial infections. This study reports the successful development of Fe 3 O 4 – Zingiber officinale extract/ZnO ferrofluid-based antimicrobial agents synthesized using double surfactants, namely oleic acid (OA) and dimethyl sulfoxide (DMSO). The x-ray diffraction (XRD) characterization produced Fe 3 O 4 and ZnO with crystallite sizes of 12.79–13.58 nm and 38.38–21.12 nm, respectively. Likewise, the results of the SEM characterization showed particle sizes of 36.49–43.67 nm, which tended to agglomerate. Then, the energy dispersive x-ray (EDX) spectrum also confirmed the composition of the nanocomposite with the presence of Fe, Zn, C, and O elements. Meanwhile, the FTIR spectrum showed a function group of Fe 3 O 4 – Zingiber officinale extract/ZnO/OA/DMSO ferrofluid at wave number 400–4000 cm −1 . The increase in mass of Fe 3 O 4 – Zingiber officinale extract nanoparticles causes the octahedral Fe–O vibration peak to shift to a larger wave number of 453–467 cm −1 . All samples exhibited superparamagnetic properties, increasing saturation magnetization values by adding Fe 3 O 4 – Zingiber officinale extract nanoparticles. Moreover, the antimicrobial activity of ferrofluids was evaluated through the diffusion method on Staphylococcus aureus , Escherichia coli , Bacillus subtilis , and Candida albicans with the optimal inhibition diameter of 12.84, 15.24, 11.90, and 9.01 mm, respectively. These synthesized samples are findings that strengthen the capacity of ferrofluids to inhibit microbial growth, thereby offering a promising avenue for developing novel antimicrobial agents.