Self-Assembled Poly(N-methylaniline)-Lignosulfonate Spheres: From Silver-Ion Adsorbent to Antimicrobial Material

Lignin self-assembly phenomena and valorization strategies for pulping, biorefining, and materials development: Part 1. The physical chemistry of lignin self-assembly

Physical chemistry aspects are emphasized in this comprehensive review of self-assembly phenomena involving lignin in various forms. Attention to this topic is justified by the very high availability, low cost, and renewable nature of lignin, together with opportunities to manufacture diverse products, for instance, polymers/resins, bioplastics, carbon fibers, bio-asphalt, sunscreen components, hydrophobic layers, and microcapsules. The colloidal lignin material, nanoparticles, and microstructures that can be formed as a result of changes in solvent properties, pH, or other adjustments to a suspending medium have been shown to depend on many factors. Such factors are examined in this work based on the concepts of self-assembly, which can be defined as an organizing principle dependent on specific attributes of the starting entities themselves. As a means to promote such concepts and to facilitate further development of nano-scale lignin products, this article draws upon evidence from a wide range of studies. These include investigations of many different plant sources of lignin, processes of delignification, solvent systems, anti-solvent systems or other means of achieving phase separation, and diverse means of achieving colloidal stability (if desired) of resulting self-assembled lignin structures. Knowledge of the self-organization behavior of lignin can provide significant structural information to optimize the use of lignin in value-added applications. Examples include chemical conditions and preparation procedures in which lignin-related compounds of particles organize themselves as spheres, hollow spheres, surface-bound layers, and a variety of other structures. Published articles show that such processes can be influenced by the selection of lignin type, pulping or extraction processes, functional groups such as phenolic, carboxyl, and sulfonate, chemical derivatization reactions, solvent applications, aqueous conditions, and physical processes, such as agitation. Precipitation from non-aqueous solutions represents a key focus of lignin self-assembly research. The review also considers stabilization mechanisms of self-assembled lignin-related structures.

A Comprehensive Mini-Review on Lignin-Based Nanomaterials for Food Applications: Systemic Advancement and Future Trends

The shift to an environmentally friendly material economy requires renewable resource exploration. This shift may depend on lignin valorization. Lignin is an aromatic polymer that makes up one-third of total lingo-cellulosic biomass and is separated into large amounts for biofuel and paper manufacture. This renewable polymer is readily available at a very low cost as nearly all the lignin that is produced each year (90-100 million tons) is simply burned as a low-value fuel. Lignin offers potential qualities for many applications, and yet it is underutilized. This Perspective highlights lignin-based material prospects and problems in food packaging, antimicrobial, and agricultural applications. The first half will discuss the present and future studies on exploiting lignin as an addition to improve food packaging's mechanical, gas, UV, bioactive molecules, polyphenols, and antioxidant qualities. Second, lignin's antibacterial activity against bacteria, fungi, and viruses will be discussed. In conclusion, lignin agriculture will be discussed in the food industries.

High value valorization of lignin as environmental benign antimicrobial

Lignin is a natural aromatic polymer of p-hydroxyphenylpropanoids with various biological activities. Noticeably, plants have made use of lignin as biocides to defend themselves from pathogen microbial invasions. Thus, the use of isolated lignin as environmentally benign antimicrobial is believed to be a promising high value approach for lignin valorization. On the other hand, as green and sustainable product of plant photosynthesis, lignin should be beneficial to reduce the carbon footprint of antimicrobial industry. There have been many reports that make use of lignin to prepare antimicrobials for different applications. However, lignin is highly heterogeneous polymers different in their monomers, linkages, molecular weight, and functional groups. The structure and property relationship, and the mechanism of action of lignin as antimicrobial remains ambiguous. To show light on these issues, we reviewed the publications on lignin chemistry, antimicrobial activity of lignin models and isolated lignin and associated mechanism of actions, approaches in synthesis of lignin with improved antimicrobial activity, and the applications of lignin as antimicrobial in different fields. Hopefully, this review will help and inspire researchers in the preparation of lignin antimicrobial for their applications.

Antibacterial lignin-based nanoparticles and their use in composite materials

Lignin, one of the most abundant biopolymers on earth, has been traditionally considered a low-value by-product of the pulp and paper industries. This renewable raw material, besides being a source of valuable molecules for the chemical industry, also has antioxidant, UV-absorbing, and antibacterial properties in its macromolecular form. Moreover, lignin in the form of nanoparticles (LigNPs) presents advantages over bulk lignin, such as higher reactivity due to its larger surface-to-volume ratio. In view of the rapid surge of antimicrobial resistance (AMR), caused by the overuse of antibiotics, continuous development of novel antibacterial agents is needed. The use of LigNPs as antibacterial agents is a suitable alternative to conventional antibiotics for topical application or chemical disinfectants for surfaces and packaging. Besides, their multiple and unspecific targets in the bacterial cell may prevent the emergence of AMR. This review summarizes the latest developments in antibacterial nano-formulated lignin, both in dispersion and embedded in materials. The following roles of lignin in the formulation of antibacterial NPs have been analyzed: (i) an antibacterial active in nanoformulations, (ii) a reducing and capping agent for antimicrobial metals, and (iii) a carrier of other antibacterial agents. Finally, the review covers the inclusion of LigNPs in films, fibers, hydrogels, and foams, for obtaining antibacterial lignin-based nanocomposites for a variety of applications, including food packaging, wound healing, and medical coatings.

Synthesis and characterization of chitosan/polyacrylamide hydrogel grafted poly(N-methylaniline) for methyl red removal

Chitosan/polyacrylamide hydrogel grafted poly(N-methylaniline) (CS/PACM-gr-PNMA) was good synthesized by chemical oxidative radical polymerization using potassium persulphate (KPS). The obtained polymer samples are characterized using IR and Uv-visible spectroscopy. Both surface properties and thermal stability were studied using XRD, SEM, BET and TGA techniques respectively. The characterized polymeric samples were used as a new sorbent for methyl red (MR). MR as an example of azo-dyes presence as pollutants in industrial wastewater which cause physiological damages was chosen to uptake. The influence of contact time, adsorbent dose, and temperature on the efficiency of CS/PACM-gr-PNMA towards the removal of MR was investigated. The efficacy was equal to 98% through 120 min at room temperature. The obtained data show that, ∆H = -21.478 kJ mol^-1, so adsorption process is physically spontaneous and follow Freundlich isotherm. The sorption process of MR on the surface of CS/PACM-gr-PNMA is proceed via the Lagergren pseudo-second order reaction. This confirms the removal mechanism by both chemical and physical adsorption of MR with both unpaired and π electrons present in polymer structure on NH, NH_2, and benzene or quinoid units respectively. In addition, it can explain the chemical adsorption type which occurs through sharing between the used adsorbent materials and the dissolved materials beside the physical adsorption.

"Waste to Wealth": Lignin as a Renewable Building Block for Energy Harvesting/Storage and Environmental Remediation

Lignin is the second most earth-abundant biopolymer having aromatic unit structures, but it has received less attention than other natural biomaterials. Recent advances in the development of lignin-based materials, such as mesoporous carbon, flexible thin films, and fiber matrix, have found their way into applications to photovoltaic devices, energy-storage systems, mechanical energy harvesters, and catalytic components. In this Review, we summarize and suggest another dimension of lignin valorization as a building block for the synthesis of functional materials in the fields of energy and environmental applications. We cover lignin-based materials in the photovoltaic and artificial photosynthesis for solar energy conversion applications. The most recent technological evolution in lignin-based triboelectric nanogenerators is summarized from its fundamental properties to practical implementations. Lignin-derived catalysts for solar-to-heat conversion and oxygen reduction are discussed. For energy-storage applications, we describe the utilization of lignin-based materials in lithium-ion rechargeable batteries and supercapacitors (e.g., electrodes, binders, and separators). We also summarize the use of lignin-based materials as heavy-metal adsorbents for environmental remediation. This Review paves the way to future potentials and opportunities of lignin as a renewable material for energy and environmental applications.

Luminescent Silver-Purine Double Helicate: Synthesis, Self-Assembly and Antibacterial Action

The synthesis, self-assembly and antibacterial activity of a luminescent silver-purine double helicate is reported. The structure of the newly synthesized silver-supported helicate [C₃₆ H₂₄ N₁₆ O₄ Cl₅ Ag₁ ] was unambiguously characterized by single-crystal X-ray crystallography. It exhibited a bright bluish-green emission (λ_max =460 nm), when excited with 380 nm light. Microscopic investigations showed that the complex has a propensity to self-assemble into nanospheres. The antibacterial activity of this silver-containing helicate was studied against both Gram-positive and Gram-negative bacteria. MIC (minimal inhibitory concentration) values showed that the complex is very active against Gram-negative bacteria. Further internalization of the silver complex into E. coli bacteria was mapped with the help of microscopic techniques. These results are significant as silver was recently found to enhance antibiotic action against Gram-negative bacteria, raising hope in countering severe bacterial infections.