Stable colloidal silver nanoparticles (AgNPs) were synthesized using Caulerpa serrulata (green marine algae) aqueous extract as an efficient reducing and stabilizing agent. This method is considered to be a sustainable alternate to the more complicated chemical procedures. To achieve the optimization synthesis of AgNPs, several effects such as extract concentration, contact time, pH values, and temperature were examined. The synthesized AgNPs were characterized by UV-Vis spectroscopy, FT-IR, XRD, and HR-TEM. The synthesized AgNPs showed an intense surface plasmon resonance band at 412 nm at the optimal conditions (20% (v/v) extract and 95 °C). TEM reveal that higher extract concentration and higher temperature leading to the formation of spherical AgNPs with an average particle size of 10 ± 2 nm. The synthesized AgNPs showed excellent catalytic reduction activity of Congo red (CR) dye from aqueous solutions. The degradation percentage of CR with AgNPs accelerated by increasing either NaBH concentration or catalytic dosage. The AgNPs synthesized at higher temperature (e.g., 10Ag-95) exhibited the highest catalytic activity. The reaction kinetics was found to be pseudo first order with respect to the dye concentration. Moreover, the AgNPs displayed antibacterial activity at lower concentration against Staphylococcus aureus, Pseudomonas aeruginosa, Shigella sp., Salmonella typhi, and Escherichia coli and may be a good alternative therapeutic approach. The outcomes of the current study confirmed that the synthesized AgNPs had an awesome guarantee for application in catalysis and wastewater treatment.
Seaweeds have a growing number of successful applications in the food industry, medicine and in the cosmetic industry, which increases the importance of evaluating their chemical composition. In the present study, three common Egyptian seaweeds (Dictyota dichotoma, Turbinaria decurrens and Laurencia obtusa) were collected from the Red Sea coast, Suez, Egypt. The chemical profile of the three seaweeds was studied beside the antioxidant activity of their extracts. The results indicated that the amount of carbohydrate was greater than the protein and lipid contents in the three seaweeds, with a natural richness in minerals and antioxidants besides considerable amounts of monounsaturated and polyunsaturated fatty acids, including Omega-3 and Omega-6 fatty acids. All essential amino acids for human were found in the three seaweeds, with significant amounts of aspartic and glutamic acids. Furthermore, the results of the antioxidant activity assays were consistent with the antioxidant contents (phenols, flavonoids, alkaloids, vitamin C, carotenoids) of each seaweed. D. dichotoma was the most valuable seaweed of the three species studied, due to its relatively high protein content of 7.28 ± 0.25%, moderate carbohydrate content of 25.35 ± 0.32%, and highest pigment and antioxidant contents. In conclusion, these three seaweeds, especially Dictyota dichotoma, have an interesting chemical composition with a prospective nutritional and pharmaceutical value.
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