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<p>Silver nanoparticles (Ag NPs) were biosynthesized using <i>Bacillus</i> sp. AVK-21 (putatively identified based on 16&#xa0;S rRNA sequencing) isolated from water samples, wherein microbial metabolites served as natural reducing and stabilizing agents for the reduction of Ag⁺ to Ag⁰. Formation of Ag NPs was confirmed by a characteristic Surface Plasmon Resonance (SPR) peak at 430&#xa0;nm in UV-Vis spectroscopy, while FTIR analysis revealed functional biomolecules responsible for nanoparticle capping. TEM demonstrated predominantly spherical nanoparticles with an average primary size of 62.4 ± 9.46&#xa0;nm, and SAED confirmed their face-centered cubic crystalline structure. DLS indicated a hydrodynamic diameter of 271.3 ± 19.7&#xa0;nm, reflecting aggregation behavior consistent with the near-zero zeta potential (~ 0 mV), which indicates minimal electrostatic stabilization and kinetically transient colloidal stability governed by biomolecule-mediated steric hindrance. EDS verified elemental silver composition with a characteristic energy peak near 3&#xa0;keV. The photocatalytic efficiency of the biosynthesized Ag NPs was evaluated against Congo Red dye under sunlight and UV irradiation, wherein sunlight exposure resulted in significantly greater degradation (67.01 ± 0.40%) compared to UV irradiation (37.80 ± 0.40%) within 120&#xa0;min. Pseudo-first-order kinetic modeling confirmed approximately 2.3-fold faster degradation kinetics under sunlight, with rate constants of 9.16 × 10⁻³ min⁻¹ (R² = 0.982) and 3.95 × 10⁻³ min⁻¹ (R² = 0.958) respectively. The enhanced sunlight performance is attributed to broader spectral excitation and improved ROS generation. This study highlights the potential of microbially synthesized Ag NPs as simple, sustainable photocatalysts for dye-polluted wastewater treatment.</p>

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Green synthesis and physicochemical characterization of biogenic silver nanoparticles for comparative sunlight and uv photocatalytic degradation of Congo red

  • 期刊论文

  • 发表日期：

    2026年5月21日

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  • S. Aditya,
  • A. Vimal,
  • A. Kavi Praba

摘要

Silver nanoparticles (Ag NPs) were biosynthesized using Bacillus sp. AVK-21 (putatively identified based on 16 S rRNA sequencing) isolated from water samples, wherein microbial metabolites served as natural reducing and stabilizing agents for the reduction of Ag⁺ to Ag⁰. Formation of Ag NPs was confirmed by a characteristic Surface Plasmon Resonance (SPR) peak at 430 nm in UV-Vis spectroscopy, while FTIR analysis revealed functional biomolecules responsible for nanoparticle capping. TEM demonstrated predominantly spherical nanoparticles with an average primary size of 62.4 ± 9.46 nm, and SAED confirmed their face-centered cubic crystalline structure. DLS indicated a hydrodynamic diameter of 271.3 ± 19.7 nm, reflecting aggregation behavior consistent with the near-zero zeta potential (~ 0 mV), which indicates minimal electrostatic stabilization and kinetically transient colloidal stability governed by biomolecule-mediated steric hindrance. EDS verified elemental silver composition with a characteristic energy peak near 3 keV. The photocatalytic efficiency of the biosynthesized Ag NPs was evaluated against Congo Red dye under sunlight and UV irradiation, wherein sunlight exposure resulted in significantly greater degradation (67.01 ± 0.40%) compared to UV irradiation (37.80 ± 0.40%) within 120 min. Pseudo-first-order kinetic modeling confirmed approximately 2.3-fold faster degradation kinetics under sunlight, with rate constants of 9.16 × 10⁻³ min⁻¹ (R² = 0.982) and 3.95 × 10⁻³ min⁻¹ (R² = 0.958) respectively. The enhanced sunlight performance is attributed to broader spectral excitation and improved ROS generation. This study highlights the potential of microbially synthesized Ag NPs as simple, sustainable photocatalysts for dye-polluted wastewater treatment.