Photocatalytic and Antibacterial Activity of CoFe2O4 Nanoparticles from Hibiscus rosa-sinensis Plant Extract

Recent developments in the bio-mediated synthesis of CoFe2O4 nanoparticles using plant extracts for environmental and biomedical applications

Conventional methods for the synthesis of nanoparticles often involve toxic chemicals, exacerbating environmental issues in the context of climate change and water scarcity. Green synthesis using plant extracts offers a sustainable and viable alternative for CoFe2O4 nanoparticle production, but understanding the mechanisms and applications of this method is challenging. Here, we review the synthesis and applications of CoFe2O4 nanoparticles using plant extracts with emphasis on biomedical activity and water treatment. Plant extract-mediated CoFe2O4 nanoparticles exhibit high surface area, small particle size, unique morphology, sufficient band gap energy, and high saturation magnetization. These nanoparticles demonstrate strong antimicrobial and anticancer activities, highlighting their potential in biomedical treatments. Green CoFe2O4 are effective in removing organic dyes, heavy metals, and pharmaceuticals from water, promoting cleaner water resources. Challenges such as scalability and reproducibility still remain, but ongoing research aims to optimize synthesis protocols and explore new applications. This work underscores the importance of sustainable nanotechnology in addressing environmental challenges.

Magnetic separation, sunlight-driven photocatalytic activity, and antibacterial studies of Sm-doped Co0.33Mg0.33Ni0.33Fe2O4 nanoparticles

Magnetic nanoparticles have emerged as a promising tool for wastewater treatment due to their unique properties. In this regard, Co0.33Mg0.33Ni0.33SmxFe2-xO4 (0.00 ≤ x ≤ 0.08) nanoparticles were prepared to examine their magnetic separation efficiency (MSE), photocatalytic, antibacterial, and antibiofilm performances. Pure nanoparticles, having the highest saturation magnetization (Ms = 31.87 emu/g), exhibit the highest MSE, where 95.6% of nanoparticles were separated after 20 min of applying a magnetic field of 150 mT. The catalytic performance of the prepared samples is examined by the photodegradation of rhodamine B (RhB) dye exposed to direct sunlight radiation. Improved photocatalytic activity is exhibited by Co0.33Mg0.33Ni0.33Sm0.04Fe1.96O4 nanoparticles, labeled as Sm0.04, where the rate of the degradation reaction is enhanced by 4.1 times compared to pure nanoparticles. Rising the pH and reaction temperature improves the rate of the photodegradation reaction of RhB. The incorporation of 15 wt% reduced graphene oxide (rGO) with Sm0.04 enhanced the rate of the reaction by 1.7 and 2.4 times compared with pure Sm0.04 sample and rGO, respectively. The antibacterial and antibiofilm activities against Escherichia coli, Leclercia adecarboxylata, Staphylococcus aureus, and Enterococcus faecium are assessed by the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) broth microdilution, the agar well diffusion, the time-kill assays, the biofilm formation, and destruction assays. The bacteria used in these assessments are isolated from wastewater. The nanoparticles exhibit a bacteriostatic activity, with a better effect against the Gram-positive isolates. Co0.33Mg0.33Ni0.33SmxFe2O4 (x = 0.00) nanoparticles have the best effect. The effect is exerted after 2-3 h of incubation. Gram-positive biofilms are more sensitive to nanoparticles.

Multifunctional characteristics of biosynthesized CoFe2O4@Ag nanocomposite by photocatalytic, antibacterial and cytotoxic applications

Carissa carandas, a traditional medicinal herb with a high concentration of antioxidant phytochemicals, has been used for thousands of years in the Ayurveda, Unani, and homoeopathic schools of medicine. By employing Carissa carandas bark extract as a reducing and capping agent in green biosynthesis, we extend this conventional application to produce CoFe2O4 and CoFe2O4@Ag nanocomposite. A variety of techniques have been used to characterize the synthesised nanocomposite, including UV-Vis, FTIR, XRD, FESEM, EDX, and BET. The CoFe2O4 and CoFe2O4@Ag nanocomposite demonstrated promising antibacterial action against human bacterial pathogens like B. subtilis and S. aureus as gram positive and P. aeruginosa and E. coli as gram negative with inhibition zones of 24.3 ± 0.57, 17.4 ± 0.75 and 20.5 ± 0.5, 19.8 ± 1.6 mm respectively, and the obtained results were superior to the nanocomposite without silver. Moreover, in-vitro cytotoxicity effects of biosynthesized CoFe2O4 and CoFe2O4@Ag were performed on the human breast cancer cell MCF-7. It was found that the MCF-7 cells' 50% inhibitory concentration (IC50) was 60 μg/mL. Additionally, biosynthesized CoFe2O4 and CoFe2O4@Ag nanocomposite was used to demonstrate the photocatalytic eradication of Rhodamine Blue (RhB). Due to the addition of Ag, which increases surface area, conductivity, and increased charge carrier separation, the CoFe2O4@Ag nanocomposite exhibits a high percentage of photocatalytic degradation of ⁓ 98% within 35 min under UV light irradiation. The photocatalytic performance of as-synthesised nanocomposite was evaluated using dye degradation-adsorption in both natural light and dark condition. Under dark conditions, it was found that 2 mg mL-1 CoFe2O4@Ag in RhB aqueous solution (5 ppm) causes dye adsorption in 30 min with an effectiveness of 72%. Consequently, it is anticipated that the CoFe2O4@Ag nanocomposite will be a promising photocatalyst and possibly a noble material for environmental remediation applications.