Lignin decolorization in organic solvents and their application in natural sunscreen

Lignin-Stabilized Tough, Sticky, and Recyclable Liquid Metal/Protein Organogels for Multifunctional Epidermal Smart Materials

Biomass-encapsulated liquid metals (LMs) composite gels have aroused tremendous attention as epidermal smart materials due to their biocompatibility and sustainability. However, they can still not simultaneously possess toughness, adhesion, and recoverability. In this work, the tough, sticky, and recyclable protein-encapsulated LMs organogels (GLMx) are fabricated through the micro-interfacial stabilization of LMs by lignin and the following preparation of food-making inspired gels. With the help of lignin modification, the LMs micro-drops demonstrated uniform dispersion in the protein matrix, as well as dense non-covalent interactions (e.g., H─bond and hydrophobic interaction) with amino acid residues in peptide chains, which endowed the GLMx with high conductivity (≈5.4 S m-1), toughness (≈738.2 kJ m-3), self-adhesiveness (a maximal lap-shear strength of ≈58.3 kPa), and recoverability. By tightly adhering onto human skin, the GLMx can act as epidermal sensors to detect drastic (e.g., joint bending) and subtle body movements (e.g., swallowing) and even recognize handwriting and speaking in real-time. Moreover, the organogels can also harvest solar energy and convert it into heat and electricity, which is promising in self-powered intelligent devices. Thus, this work paves a facile way to prepare protein/LMs composite organogels that are suitable for multiple applications like healthcare, human-robot interactions, and solar energy conversion.

State-of-the-art of lignin-derived carbon nanodots: Preparation, properties, and applications

Lignin-derived carbon nanodots (LCNs) are nanometer-scale carbon spheres fabricated from naturally abundant lignin. Owing to rich and highly heritable graphene like π-π conjugated structure of lignin, to fabricate LCNs from it not only endows LCNs with on-demand tunable size and optical features, but also further broadens the green and chemical engineering of carbon nanodots. Recently, they have become increasingly popular in sensing, bioimaging, catalysis, anti-counterfeiting, energy storage/conversion, and others. Despite the enormous research efforts put into the ongoing development of lignin value-added utilization, few commercial LCNs are available. To have a deeper understanding of this issue, critical impacts on the preparation, properties, and applications of state-of-the-art LCNs are carefully reviewed and discussed. A concise analysis of their unique advantages, limitations for specific applications, and current challenges and outlook is conducted. We hope that this review will stimulate further advances in the functional material-oriented production of lignin.

Polymerizable deep eutectic solvent treated lignocellulose: Green strategy for synergetic production of tough strain sensing elastomers and nanocellulose

Liquid free ion-conductive elastomers (ICEs) have demonstrated promising potential in various advanced application scenarios including sensor, artificial skin, and human-machine interface. However, ICEs that synchronously possess toughness, adhesiveness, stability, and anti-bacterial capability are still difficult to achieve yet highly demanded. Here, a one-pot green and sustainable strategy was proposed to fabricate multifunctional ICEs by extracting non-cellulose components (mainly lignin and hemicellulose) from lignocellulose with polymerizable deep eutectic solvents (PDES) and the subsequent in-situ photo-polymerization process. Ascribing to the uniform dispersion of non-cellulose components in PDES, the resultant ICEs demonstrated promising mechanical strength (a tensile strength of ~1200 kPa), high toughness (~9.1 MJ m-3), favorable adhesion (a lap-shear strength up to ~61.5 kPa toward metal), conducive stabilities, and anti-bacterial capabilities. With the help of such advantages, the ICEs exhibited sensitive (a gauge factor of ~23.5) and stable (~4000 cycles) performances in human motion and physiological signal detection even under sub-zero temperatures (e.g., -20 °C). Besides, the residue cellulose can be mechanically isolated into nanoscale fibers, which matched the idea of green chemistry.

Lignin reinforced tough, adhesive, and recoverable protein organohydrogels for wearable strain sensing under sub-zero temperatures

Protein-based hydrogels with promising biocompatibility and biodegradability have attracted considerable interest in areas of epidermal sensing, whereas, which are still difficult to synchronously possess high mechanical strength, self-adhesion, and recoverability. Hence, the bio-polymer lignosulfonate-reinforced gluten organohydrogels (GOHLx) are fabricated through green and simple food-making processes and the following solvent exchange with glycerol/water binary solution. Ascribing to the uniform distribution of lignosulfonate in gluten networks, as well as the noncovalent interactions (e.g., H-bond) between them, the resultant GOHLx exhibit favorable conductivity (∼14.3 × 10-4 S m-1), toughness (∼711.0 kJ m-3), self-adhesion (a maximal lap-shear strength of ∼33.5 kPa), high sensitivity (GF up to ∼3.04), and durability (∼3000 cycles) toward shape deformation, which are suitable for the detection of both drastic (e.g., elbow and wrist bending) and subtle (e.g., swallowing and speaking) human movements even under -20 °C. Furthermore, the GOHLx is also biocompatible, degradable, and recoverable (by a simple kneading process). Thus, this work may pave a simple, green, and cheap way to prepare all-biomass-based, tough, sticky, and recoverable protein-based organohydrogels for epidermal strain sensing even in harsh environments.

Lignocellulosic biomass pretreatment with a lignin stabilization strategy and valorization toward multipurpose fractionation

Lignocellulosic biomass has emerged as a promising alternative with sustainable advantages for the production of a wide range of renewable products and value-added chemicals. In this study, a pretreatment strategy that use a fully recyclable acid hydrotrope (p-TsOH aqueous solution) to extract lignin and employ glyoxylic acid (GA) to stabilize lignin was proposed for biomass valorization toward multipurpose fractionation. 83.0 % of lignin was dissolved out by p-TsOH hydrotrope (80 wt%) with GA addition to form GA-stabilized product at 80 o C for 15 min. The stabilized lignin was subsequently used as an additive in the preparation of lignin-based suncream. Notably, the incorporation of 4 wt% lignin nanospheres into an SPF15 sunscreen yielded a measured SPF of 59.94. Furthermore, the depolymerization of uncondensed lignin into aromatic monomers yielded a high lignin-oil yield of 84.2 %. Additionally, direct heating of the pretreatment liquor facilitated the conversion of monosaccharides into furfural, achieving a desired yield of 53.7 % without the addition of any acid catalyst. The pretreatment also enhanced the enzymatic hydrolysis of glucan, resulting in a saccharification yield of 98.4 %. Moreover, short-term ultrasonication of the pretreated substrate yielded pulp suitable for papermaking. Incorporating 15 wt% fibers into the produced paper sheets led to a 5.3 % increase in tear index and a 25.4 % increase in tensile index. This study presents a viable pretreatment strategy for the multipurpose fractionation of lignocellulosic biomass, offering potential avenues for biomass valorization.

Metal ion and hydrogen bonding synergistically mediated carboxylated lignin/cellulose nanofibrils composite film

In order to alleviate the resource and environmental problems caused by plastic film materials, the development of biodegradable cellulose-based films is crucial. Inspired by the strengthening mechanism of cellulose-lignin network from wood, carboxylated lignin (CL) was isolated using maleic acid (MA) pretreatment catalyzed by metal chlorides. Compared with pure MA, the presence of metal ions yielded CL with high carboxyl content (0.34 mmol/g), small size and good dispersibility. CL was then composited with CNF to prepare various CL/cellulose nanofibrils (CNF) composite films. When the addition of ferric chloride was 0.3 mmol/g maleic acid, the corresponding composite films exhibited highest tensile strength (180.0 MPa), Young's modulus (13.0 GPa) and excellent ultraviolet blocking rate (97.0 %). Meanwhile, the interaction forces measured by atomic force microscope showed that the binding between CNF and various CLs (276-406 nN) was higher than that between pure CNFs (202 nN), verifying that CL enhanced the mechanical properties of composite films. In summary, this work constructs a super-strong network between CL and CNF synergistically mediated by metal ion crosslinking and hydrogen bonding, which can be a promising alternative to replace conventional plastics in multiple areas.