A Lignin Silver Nanoparticles/Polyvinyl Alcohol/Sodium Alginate Hybrid Hydrogel with Potent Mechanical Properties and Antibacterial Activity.

Antibacterial hydrogels have attracted significant attention due to their diverse applications, efficient antimicrobial properties, and adaptability to various environments and requirements. However, their relatively fragile structure, coupled with the potential for environmental toxicity when exposed to their surroundings for extended periods, may significantly limit their practical application potential. In this work, a composite hydrogel was synthesized with outstanding mechanical features and antibacterial capability. The hydrogel was developed through the combination of the eco-friendly and enduring antibacterial agent, lignin silver nanoparticles (Lig-Ag NPs), with polyvinyl alcohol (PVA) and sodium alginate (SA), in varying proportions. The successful synthesis of the hydrogel and the dispersed distribution of Lig-Ag NPs within the hydrogel were confirmed by various analytical techniques, including field emission scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), mercury intrusion porosimetry (MIP), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The formation of multiple hydrogen bonds between Lig-Ag NPs and the composites contributed to a more stable and dense network structure of the hydrogel, consequently enhancing its mechanical properties. Rheological tests revealed that the hydrogel exhibited an elastic response and demonstrated outstanding self-recovery properties. Significantly, the antibacterial hydrogel demonstrated effectiveness against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), achieving a <5% survival of bacteria within 12 h. This study presented a green and straightforward synthetic strategy for the application of antibacterial composite hydrogels in various fields.

Lignin particles as green pore-forming agents for the fabrication of microporous polysulfone membranes.

Templating polymeric membranes with micro-nano-scaled solid materials is an effective method to simultaneously improve the water flux and retention ratio. However, the fabrication of a green, recyclable, and size-controlled template material remains a challenge. Here, a new green pore-forming agent, lignin particles (LP), was developed to prepare porous polysulfone (PSF) membranes via the phase inversion technique. A series of LP have uniform sizes from ~200 nm to ~1800 nm. The performances of the templated PSF membranes cast at different sizes and contents of LP were examined for their surface and crosssection morphologies. The LP-templated PSF membranes displayed a remarkable enhancement in flux, porosity, and moisture content. Particularly, the PSF membranes cast with LP from ~200 to 1800 nm broke the traditional trade-off to a certain degree, which possessed stable retentions of bovine serum albumin (> 85 %) and significantly improved water flux (174.275 to 254.775 L m-2 h-1). In addition, the LP pore-forming agent is low-cost and environmentally friendly as it was prepared from industrial by-products and can be easily recycled. Overall, this study shows that lignin particles are green pore-forming agents that can be used for the fabrication of porous polymeric membranes with improved performance for water treatment.

Combined bactericidal process of lignin and silver in a hybrid nanoparticle on E. coli.

Among multiple engineered nanoparticles that have been used in the bactericidal application, silver nanoparticles (Ag NPs) are the most explored bactericidal functional materials with their high efficiency and broad-spectrum bactericidal properties. However, environmental toxicology and lack of modifiability restrict their further development. In this study, a simple and economic method was established to fabricate lignin and silver hybrid nanoparticles (Lig-Ag NPs) with bactericidal ability. Afterwards, material characterization, bactericidal evaluation, and mechanism exploration were implemented to explore the properties of Lig-Ag NPs. The results indicated that Lig-Ag NPs not only demonstrated remarkable dispersity, uniformity, and encapsulation efficiency but also possessed approximated bactericidal ability on Escherichia coli and better durability compared with the same concentration of Ag NPs on E. coli. On the other hand, flow cytometry and transcriptomic analysis were used to further explore the bactericidal mechanism of Lig-Ag NPs. The results showed that oxidative stress was the possible leading bactericidal mechanism of Lig-Ag NPs. The formation approaches of reactive oxygen species production were various including the slow release of silver ion and generation of quinone/semi-quinone radicals on account of the combined effect of lignin and silver. Graphical abstract: Lig-Ag NPs exhibited remarkable dispersity, uniformity, encapsulation efficiency, and possessed approximated bactericidal ability and better durability compared with Ag NPs. Supplementary information: The online version contains supplementary material available at 10.1007/s42114-022-00460-z.

A functional lignin-based nanofiller for flame-retardant blend.

Lignin-based flame retardants represent great promising next-generation flame retardants due to their sustainability, unique aromatic structure, and high charring capability. However, their applications are still limited by the compatibility, processability, and efficiency of flame retardancy. Here, a green functional lignin-based nanofiller (lignin-diethylenetriamine/red phosphorus nanoparticles, Lignin-N-P NPs) was prepared by the chemical modification and co-precipitation. After blending with the commercial acrylonitrile butadiene styrene copolymers (ABS), the physical, chemical, and flame retardant properties of the blends reveal that Lignin-N-P NPs/ABS blend has acceptable processability, mechanical properties, and significantly improved thermal stability and fire performance. Its values of peak heat release rate and total heat released per unit area were significantly dropped 67.8% and 77.5%, respectively. This study will initiate a new design for not only flame retardants but also lignin-based materials.

Green and stable piezoresistive pressure sensor based on lignin-silver hybrid nanoparticles/polyvinyl alcohol hydrogel.

Hydrogel-based piezoresistive sensors have high practical value in many revolutionary applications, such as intelligent and electronic devices. However, with existing hydrogels, it is very difficult to achieve a combination of good mechanical properties, stable conductivity, and simple/green fabrication method. In this study, hybrid organic-inorganic nanoparticles (lignin-silver hybrid nanoparticles, Lig-Ag NPs) were synthesized by using alkaline lignin as the organic component and silver nanoparticle (Ag NPs) as the inorganic component. Interaction between the lignin and Ag NPs leads to the composite of hybrid nanoparticles that not only decreased the release of Ag NPs but also generated dynamically stable semi-quinone radicals in lignin. After compositing with polyvinyl alcohol (PVA) matrix, Lig-Ag NPs provided strong sacrificial hydrogen bonds and facilitated the delivery of electronic. Benefiting from these structural features and the pore-forming effect of ammonia (from Lig-Ag NPs solution), the PVA/Lig-Ag NPs hydrogel exhibits outstanding compressibility, pressure sensitivity, and stability of signal response. This study provides a green and simple design strategy for piezoresistive pressure sensors based on nanocomposite hydrogel.

Cellulose-assisted construction of high surface area Z-scheme C-doped g-C3N4/WO3 for improved tetracycline degradation.

The preparation of heteroatom doping heterojunction photocatalysts with nontoxic carbonaceous materials and simple method still remains a challenge. Herein, ternary Z-scheme C-doped graphitic carbon nitride/tungsten oxide (C-doped g-C3N4/WO3) was successfully fabricated via the hydrothermal impregnation with cellulose nanocrystal, high-temperature calcination, and electrostatic self-assembly with WO3 nanocuboids in turns. Benefiting from the porous structure, high specific areas (57.20 m2 g-1), C-substitution, and the formation of Z-scheme heterojunction, the resulting photocatalyst exhibited narrower band-gap, enhanced visible-light absorption and separation of charge carrier, faster interfacial charge transfer, good oxidation/reduction capacities, and thus improved the photocatalytic activity performance. As such, this investigation will provide an effective route for not only incorporating semiconductors and heteroatoms into g-C3N4 but also developing more heterojunction with markedly improved photocatalytic performance.