Green fused nanoparticles from seaweed as a sustainable resource: Study on antimicrobial activities against human pathogens and photocatalytic degradation of methylene blue (MB) dye

[Display omitted] •PP extracts offer an eco-friendly, and non-toxic alternative to chemical/physical stabilizing agents.•PPAg-NPs show superior antibacterial effects of 16 mm against E. coli and 10 mm in B. subtilis.•Degradation of MB dye by 90% was achieved within 105 mints under UV-light treatment. The simple, fast, efficient route and eco-friendly synthesis of silver nanoparticles (Ag-NPs) using the marine-algae Padina pavonica (PP) extracts. The heat bio-reduction process involves using PP extract mediated to synthesize silver (Ag) nanoparticles (NPs). The PP extract provides an eco-friendly, low-cost, and safer alternative to traditional chemical and physical methods. The GC–MS results detect GLYCERYL TRIDODECANOATE, DODECANOIC ACID, and 1,2,3-PROPANETR dominantly examined majorly play a role in synthesizing the Ag-NPs. The synthesized PP-mediated NPs were denoted as PPAg-NPs and characterized the structural and morphological properties by UV–vis spectroscopy, XRD, SEM, HRTEM, EDS, DLS, and FT-IR. The 16S rDNA technique confirmed 6 (n = 6) human pathogens (HPs) strains were used for the antimicrobial study. Green synthesized PPAg-NPs showed a maximum and minimum inhibition growth zone of 16 mm in Escherichia coli, and 10 mm in Bacillus subtilis. The study result suggested the PPAg-NPs act with high efficiency and display greater sensitivity for antibacterial material depending on the concentrations. The synthesized green PPAg-NPs investigated the photocatalytic degradation of methylene blue (MB) dye. The highest 90 % efficiency was achieved under UV-light treatment within 105 min. The study’s outcome indicates that PPAg-NPs exhibit a strong antimicrobial efficacy toward HPs and MB decolorization that contributes to water cleansing, healthcare, and biomedical industries.