Green Synthesis of Silver Nanoparticles as an Effective Antibiofouling Material for Polyvinylidene Fluoride (PVDF) Ultrafiltration Membrane

Polyvinylidene Fluoride (PVDF) and Nanoclay Composites' Mixed-Matrix Membranes: Exploring Structure, Properties, and Performance Relationships

Polyvinylidene fluoride (PVDF) membranes have become a favored choice for membrane filtration because of their outstanding mechanical characteristics, chemical resistance, thermal stability, and ease of handling. Nevertheless, the hydrophobic nature of PVDF membranes can result in fouling, which diminishes their efficiency over time. This study explores the impact of ZnO-Nanoclay on the properties and performance of mixed matrix membranes made from polyvinylidene fluoride (PVDF) at different loading percentages (0, 1, and 3 wt%). The ZnO-Nanoclay nanoparticles were synthesized using environmentally friendly methods, characterized, and blended into PVDF matrices via a solution-casting technique, resulting in a series of membranes. The synthesized nanoparticles were analyzed using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The resulting mixed-matrix membranes underwent comprehensive analyses to assess their structure and surface properties, employing SEM, XRD, Atomic Force Microscopy (AFM), and contact-angle measurements. Furthermore, tensile, antibacterial, and barrier properties were evaluated. Integrating ZnO-Nanoclay into PVDF membranes greatly improves antifouling properties, achieving inhibition rates of 99.92% at a clay-loading percentage of 3 wt% and increasing water-flux rates by 16% compared to pure PVDF membranes at 1 wt%. In addition, ZnO-Nanoclay nanoparticles significantly boost the mechanical properties of PVDF membranes, enhancing maximum strength by 500% at 3 wt% loading. This study examines the interplay between the structure, properties, and performance of mixed-matrix membranes by comparing different PVDF membranes that were mixed with different nanoclay composites, providing significant insights into improving these membranes through the incorporation of nanoclay composites to enhance their overall properties and effectiveness.

Green-synthesised silver and zinc oxide nanoparticles from stingless bee honey: Morphological characterisation, antimicrobial action, and cytotoxic assessment

This study investigated the green synthesis of silver nanoparticles (Ag-NPs) and zinc oxide nanoparticles (ZnO-NPs) using an aqueous extract of stingless bee honey (SBH) as a reducing and stabilising agent. The rich compositions of SBH containing flavonoids, phenolics, organic acids, sugars, and enzymes makes the SBH extract an ideal biocompatible precursor for the NPs synthesis. Physicochemical characterisation of the synthesised NPs was performed using UV-Vis spectroscopy, FESEM, TEM, XRD, and FTIR spectroscopy. The results revealed that the Ag-NPs and ZnO-NPs exhibited polydispersity, with size ranges between 25-50 nm and 15-30 nm, respectively. A majority of the NPs possessed a spherical morphology. Furthermore, the study evaluated the antimicrobial activity of the SBH-based NPs against gram-positive (Staphylococcus aureus, ATCC 43300) and gram-negative (Escherichia coli, ATCC 25922) bacteria. The findings demonstrated significantly higher antimicrobial efficacy of the Ag-NPs with a zone of inhibition (ZOI) of 16.91 mm against S. aureus, and 17.43 mm against E. coli compared to the ZnO-NPs which having a ZOI of 13.05 mm and 14.01 mm, respectively. Notably, cytotoxicity assays revealed no adverse effects of the synthesised NPs on normal mouse fibroblast (3T3) and human lung fibroblast (MRC5) cells up to 100 μg/ml of concentration. These findings suggest the potential of SBH-based Ag-NPs and ZnO-NPs as safe and effective antibacterial agents for various applications, including pharmaceuticals, cosmetics, ointments, and lotions.

Green-synthesized silver nanoparticle-enhanced nanofiltration mixed matrix membranes for high-performance water purification

This study presents the fabrication and characterization of mixed matrix membranes (MMMs) incorporating green-synthesized silver nanoparticles (AgNPs) using Hibiscus Rosa sinensis extract within a polyethersulfone (PES) matrix for nanofiltration (NF) application. The membranes were evaluated for their pure water permeability, salt rejection, dye removal, and antifouling performance. Results showed that the membrane with 0.75 wt% AgNPs exhibited the highest pure water permeability of 36 L/m2 h-1 bar-1 attributed to increased porosity and enhanced hydrophilicity. Addition of 0.75wt% AgNPs resulted in significant improvements, with NaCl rejection increased from 32 to 57%, MgSO4 from 26 to 67%, and CaCl2 from 27 to 41%. Antifouling tests revealed that the 0.75 wt% AgNPs membrane had the lowest irreversible fouling and highest flux recovery due to the antimicrobial action and improved surface properties of AgNPs. Importantly, the performance of the fabricated membranes align with loose nanofiltation characteristcs, as evidence by high dye rejection rates coupled with moderate rejection of salts. This study highlights the potential of green-synthesized AgNPs as effective nanofillers for developing high-performance and environmentally sustainable membranes into wastewater treatment.

In-situ photoreduction strategy for synthesis of silver nanoparticle-loaded PVDF ultrafiltration membrane with high antibacterial performance and stability

Ultrafiltration (UF) technology using polyvinylidene fluoride (PVDF) membrane has been widely applied to water and wastewater treatment due to its low cost and simple operation process. However, PVDF-based UF membrane always encountered the issue of membrane biofouling that greatly impacted the filtration performance. In this study, we prepare a silver nanoparticle (AgNP)-loaded PVDF (Ag/PVDF) UF membrane by an in-situ photoreduction method to mitigate the membrane biofouling. Different from the previously reported method, AgNPs were synthesized in-situ by a UV photoreduction process, in which Ag⁺ ions were reduced to zero-valent Ag nanoparticles by the photo-induced reducing radicals. Antibacterial experiments showed that the inhibition efficiency of Ag/PVDF membrane to Escherichia coli reached up to ~ 99% after antibacterial treatment for 24 h. In comparison with the pristine PVDF membrane, Ag/PVDF membrane possessed a lower water contact angle (83.7° vs. 38.1°), and its pure water flux increased by 23.7%, and a high bovine serum albumin (BSA) rejection efficiency was maintained. In addition, the high stability of the Ag/PVDF composite membrane was confirmed by the extremely low releasing amount of Ag. This study provides a novel strategy for the preparation of metal nanoparticle-incorporated Ag/PVDF ultrafiltration composite membrane showing favorable antibacterial performance and stability.

Ulvan as a Reducing Agent for the Green Synthesis of Silver Nanoparticles: A Novel Mouthwash

The antibacterial activity of an Ulvan-based silver nanoparticle (AgNP) system was evaluated in the current study. The green synthesis of biogenic silver nanoparticles was conducted using Ulvan, a sulphated polysaccharide extracted from Ulva lactuca. A novel mouthwash containing AgNPs was prepared, and tested for its efficacy and safety. AgNPs were confirmed with spectrophotometric analysis (UV–A visible spectrophotometer), and the characterisation was established with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The AgNPs were spherical, and their average size was 8–33 nm, as shown via TEM. The antioxidant assay was conducted via DDPH assay, wherein the AgNPs, at a concentration of 50 μL/mL, showed 93.15% inhibition. Furthermore, anticancer activity was tested by evaluating the cell viability utilising the method of an MTT assay on the 3T3-L1 cell lines. AgNPs, at 30 µL/mL, showed maximal cell viability, denoting no cytotoxic effect. The silver-nanoparticle-based mouthrinse, at a concentration of 100 µL/mL, demonstrated antimicrobial activity against Streptococcus mutans, Staphylococcus aureus, Lactobacillus, and Candida albicans. This study shows that mouthwash prepared from the Ulvan-silver nanoparticle system could be a nontoxic and effective oral antimicrobial agent.

PVDF/MOFs mixed matrix ultrafiltration membrane for efficient water treatment

Polyvinylidene fluoride (PVDF), with excellent mechanical strength, thermal stability and chemical corrosion resistance, has become an excellent material for separation membranes fabrication. However, the high hydrophobicity of PVDF membrane surface normally leads a decreased water permeability and serious membrane pollution, which ultimately result in low operational efficiency, short lifespan of membrane, high operation cost and other problems. Metal-organic frameworks (MOFs), have been widely applied for membrane modification due to its large specific surface area, large porosity and adjustable pore size. Currently, numerous MOFs have been synthesized and used to adjust the membrane separation properties. In this study, MIL-53(Al) were blended with PVDF casting solution to prepare ultrafiltration (UF) membrane through a phase separation technique. The optimal separation performance was achieved by varying the concentration of MIL-53(Al). The surface properties and microstructures of the as-prepared membranes with different MIL-53(Al) loading revealed that the incorporation of MIL-53(Al) enhanced the membrane hydrophilicity and increased the porosity and average pore size of the membrane. The optimal membrane decorated with 5 wt% MIL-53(Al) possessed a pure water permeability up to 43.60 L m-2 h-1 bar-1, while maintaining higher rejections towards BSA (82.09%). Meanwhile, the prepared MIL-53(Al)/LiCl@PVDF membranes exhibited an excellent antifouling performance.

Structure-Morphology-Antimicrobial and Antiviral Activity Relationship in Silver-Containing Nanocomposites Based on Polylactide

Green synthesis of silver-containing nanocomposites based on polylactide (PLA) was carried out in two ways. With the use of green tea extract, Ag⁺ ions were reduced to silver nanoparticles with their subsequent introduction into the PLA (mechanical method) and Ag⁺ ions were reduced in the polymer matrix of PLA-AgPalmitate (PLA-AgPalm) (in situ method). Structure, morphology and thermophysical properties of nanocomposites PLA-Ag were studied by FTIR spectroscopy, wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) methods. The antimicrobial, antiviral, and cytotoxic properties were studied as well. It was found that the mechanical method provides the average size of silver nanoparticles in the PLA of about 16 nm, while in the formation of samples by the in situ method their average size was 3.7 nm. The strong influence of smaller silver nanoparticles (3.7 nm) on the properties of nanocomposites was revealed, as with increasing nanosilver concentration the heat resistance and glass transition temperature of the samples decreases, while the influence of larger particles (16 nm) on these parameters was not detected. It was shown that silver-containing nanocomposites formed in situ demonstrate antimicrobial activity against gram-positive bacterium S. aureus, gram-negative bacteria E. coli, P. aeruginosa, and the fungal pathogen of C. albicans, and the activity of the samples increases with increasing nanoparticle concentration. Silver-containing nanocomposites formed by the mechanical method have not shown antimicrobial activity. The relative antiviral activity of nanocomposites obtained by two methods against influenza A virus, and adenovirus serotype 2 was also revealed. The obtained nanocomposites were not-cytotoxic, and they did not inhibit the viability of MDCK or Hep-2 cell cultures.