Sunscreen Performance of Lignin from Different Technical Resources and Their General Synergistic Effect with Synthetic Sunscreens

Five types of industrial lignin are blended with a pure cream and a commercial sunscreen lotion. Lignin is found to significantly boost their sunscreen performance. Photostability of the lignin-modified lotions is analyzed. The results show that hydrophobic lignin has better sunscreen performance than hydrophilic counterpart. Sun protection factor (SPF) of the pure cream containing 10% organosolv lignin (OL) reaches 8.66. Small amount of hydrophobic lignin dramatically increases SPF value of the sunscreen lotions. Adding 1% lignin almost doubles the sun lotion’s SPF. Addition of 10% OL to the lotion boosts its SPF from 15 to 91.61. However, it is also found that hydrophilic lignin tends to demulsify the lotions due to an electrostatic disequilibrium. After 2 h of UV radiation, UV absorbance of all the five lignin-modified sunscreen lotions increases up to the limit of measuring instrument. All the lignin types studied in this work are found to have a general synergistic effect with sunscreen actives in the commercial lotion. An effort is also made to elucidate radical mechanisms of the synergy

UV-Assisted Room-Temperature Fabrication of Lignin-Based Nanosilver Complexes for Photothermal-Mediated Sterilization

Green and controllable preparation of silver nanoparticles (AgNPs) remains a great challenge. In this work, ethanol-extracted lignin-based nanosilver composites (AgNPs@EL) were synthesized at room temperature with the assistance of ultraviolet (UV) radiation. The ethanol-extracted lignin (EL) could serve as natural dispersion carriers and reducing agents for AgNPs. The reducing ability of EL could be further improved under UV irradiation, which enables the rapid synthesis of AgNPs at room temperature. More importantly, due to the good photothermal conversion capacity of EL, AgNPs@EL exhibits remarkably enhanced photothermal performance and excellent photothermal antibacterial ability, which could cause 7.2 and 5.3 log10 CFU/mL reduction against Escherichia coli and Staphylococcus aureus, respectively, under near-infrared (NIR) irradiation (808 nm, 1.8 W/cm2) for 5 min. Furthermore, the composite film obtained by impregnating bacterial cellulose onto AgNPs@EL solution also shows significantly improved mechanical properties and photothermal antimicrobial activity. Therefore, this work may provide insights into the design of lignin-based photothermal-mediated antimicrobial materials

Facile and Efficient Synthesis of Silver Nanoparticles Based on Biorefinery Wood Lignin and Its Application as the Optical Sensor

Fabricating silver nanoparticles (AgNPs) based on renewable energy sources is wildly exploited because of the sustainable synthetic strategy and versatile applications of AgNPs. Alkali lignin (AL), as the byproduct from pulp mills, is a potential natural reducing agent. However, the synthetic methods of AL-based AgNPs (AL@Ag) still have drawbacks, such as unusual conditions and extra and high-cost purification processes. Here, a facile and efficient approach to synthesize and purify good-dispersing AL@Ag (17–27 nm) was presented, using Ag₂O as the silver precursor and AL as both reducing agents and stabilizers in dimethyl sulfoxide (DMSO) solvent. The maximum reduction capacity of AL to Ag⁺ was increased to 8 mM/g at room temperature because of the activation of both Ag₂O and DMSO. Most conveniently, the product was effectively purified by easy centrifugation. The reducing mechanism and reaction behavior were also systematically studied. Meanwhile, AL@Ag maintained versatile applications of AgNPs and exhibited great potential as the colorimetric sensor and plasmonic resonance energy acceptor for Hg²⁺ and rhodamine B, respectively. Our work displayed a general and efficient method to prepare AL@Ag, which might provide a realizable perspective to the high-value utilization of lignin

A Novel Lignin/ZnO Hybrid Nanocomposite with Excellent UV-Absorption Ability and Its Application in Transparent Polyurethane Coating

In this work, lignin/zinc oxide nanocomposites with excellent UV-absorbent performance were prepared through a novel hydrothermal method using industrial alkali lignin (AL) as raw materials. AL was first modified by quaternization to synthesize quaternized alkali lignin (QAL). The QAL/ZnO nanocomposites with different lignin contents were then prepared via a facile one-step hydrothermal method using QAL and zinc nitrate hexahydrate and hexamethylenetetramine in aqueous solution. The prepared nanocomposite possessed an average diameter of ∼100 nm and showed excellent synergistic UV-absorbent performance. The particle morphology and hybrid structure were carefully characterized by SEM, TEM, XRD, FT-IR, XPS, UV–vis, and TG analyses. Interestingly, it was found that the UV transmittance of polyurethane (PU) film was significantly reduced and the mechanical properties of the PU were significantly enhanced when blended with the prepared QAL/ZnO nanocomposite. The results of this work were of practical importance for high value-added application of industrial lignin in the field of functional materials

Formation of Uniform Colloidal Spheres Based on Lignosulfonate, a Renewable Biomass Resource Recovered from Pulping Spent Liquor

Effects of mass ratios on the sodium lignosulfoante (NaLS) and cetyltrimethylammonium bromide (CTAB) mixing system were first investigated by zeta potential and surface tension measurements. Uniform colloidal spheres from the NaLS/CTAB complex were then fabricated via electrostatic and hydrophobic self-assembly and characterized by DLS, TEM, contact angle, elemental analysis, XPS, and FTIR measurements. Results showed the stoichiometric mass ratio (SMR) of the NaLS/CTAB system was 1:2.82, where the hydrophobicity was strongest and preparing colloidal spheres was feasible. Colloidal spheres were formed through gradual aggregation of NaLS/CTAB molecules at SMR, which was induced by continuously adding water into NaLS/CTAB/EtOH solutions. NaLS/CTAB molecules started to form spheres at a critical water content of 58 vol %, and the formation process was completed at a water content of 84 vol % when the initial concentration of NaLS/CTAB in EtOH was 1.0 mg mL^–1. The sizes of NaLS/CTAB colloidal spheres could be well controlled by adjusting water-adding rates. This preparation of lignosulfonate-based nanoparticles is very simple, safe, and low-cost, and these obtained nanoparticles have advantages of biodegradability and ultraviolet resistance. This study provides a green and valuable approach to value-added applications of lignosulfonate biomass recovered from pulping spent liquor and is of great significance for both economic and environmental benefits

Horseradish Peroxidase Modification of Sulfomethylated Wheat Straw Alkali Lignin To Improve Its Dispersion Performance

Wheat straw alkali lignin (WAL), byproducts from the alkali pulping process, is a low-value product with poor water solubility and limited dispersion performance. Sulfomethylated wheat straw alkali lignin (SWAL) was first prepared by sulfomethylation. In order to further improve the dispersion performance of WAL, a commercially available horseradish peroxidase (HRP) was then used to modify SWAL. Gel permeation chromatography showed an obvious increase in molecular weight after HRP modification by approximately 6 fold and 18 fold, compared with SWAL and WAL, respectively. The structural characterization was investigated by functional group content measurements and IR and ¹H NMR analyses. After the HRP modification, the phenolic and methoxyl group content decreased, while the sulfonic and carboxyl group content increased. Because of the higher molecular weight and hydrophilic group content, the HRP modification induced a significant improvement in adsorption and dispersion performance of WAL

Preparation of Photoresponsive Azo Polymers Based on Lignin, a Renewable Biomass Resource

Lignin-based azo polymers are prepared from alkali lignin, a byproduct in spent liquor from the pulping and papermaking industry, and their structures and photochromic effects are characterized by elemental analysis, Fourier transform infrared, ¹H nuclear magnetic resonance, and ultraviolet–visible spectroscopy. Results show that only the 2-(4-nitrophenyl azo) phenol lignin-modified polymer (AL-azo-NO₂) shows a significant photochromic effect, and its photoresponsive behavior is evidently slower than that of the synthetic polymer with a similar azo chromophore. For the 2-(4-methoxyphenyl azo) phenol lignin-modified polymer, its photoisomerization behavior was expected to be similar to that of azobenzene-type molecules, but its photoresponse is not obvious. The abnormal photochromic effect of AL-azo polymers is related to strong steric hindrance of lignin backbones. With addition of water (poor solvent), AL-azo-NO₂ shrinks gradually, which prevents azobenzene groups from isomerizing and results in a lower isomerization efficiency at higher water contents. Preparation of lignin-based azo polymers offers a novel source of azo polymers and provides a green and sustainable pathway for value-added utilization of lignin biomass recovered from the pulping industry

Fabrication of Lignosulfonate Vesicular Reverse Micelles to Immobilize Horseradish Peroxidase

Sodium lignosulfonate reverse micelles (SLRMs) with vesicular structure were prepared by self-assembling in ethanol–water media and applied to encapsulate horseradish peroxidase (HRP). Results showed that sodium lignosulfonate (SL) could not form SLRMs until the ethanol content reached 63% when its initial concentration was 7.5 g L^–1. Owing to strong electrostatic repulsion, solid spherical SLRMs gradually swelled to stable vesicular structures with an average size of 240 nm. The shell of the SLRM thickened when NaCl was added to screen the electrostatic interaction. HRP can be effectively encapsulated while retaining its activity in the hydrophilic core of a SLRM. When hydrogen peroxide was added to initiate the catalytic activity of HRP, SL molecules would be polymerized and the structure of SLRMs would be fixed. Furthermore, HRP immobilized in polymerized SLRMs showed high activity at a more acidic pH of 4 and at a lower optimal temperature decrease of 35 °C compared to free HRP. SLRM allows enzymes such as HRP to work at more acidic and lower temperature conditions

Conductivity Enhancement of Poly(3,4-ethylenedioxythiophene)/Lignosulfonate Acid Complexes via Pickering Emulsion Polymerization

Poly­(3,4-ethylenedioxythiophene)/lignosulfonate acid (PEDOT/LS) submicron particles are doped into a 3,4-ethylenedioxythiophene (EDOT)/water mixture as a solid stabilizer to form a Pickering emulsion. The conductivity of the new PEDOT/LS complexes prepared by Pickering emulsion polymerization (PEDOT/LS-PEP) is improved by 2 orders of magnitude. The structure and properties of PEDOT/LS-PEP are investigated by UV, FTIR, XRD, XPS, DLS, optical microscope, four point probe meter, and surface resistance tester. The results show that the average particle size increases from 550 nm to 2.4 μm, and the PEDOT content in PEDOT/LS-PEP is 3.5 times that in the original PEDOT/LS submicron particles, while the structure of PEDOT/LS-PEP remains amorphous. Due to the enhancement in conductivity, the coating film made by PEDOT/LS-PEP decreases the surface resistance of glass from 10¹² to 10⁶ Ω sq^–1. These new PEDOT/LS-PEP complexes meet the requirement of industrial antistatic materials well

Synergistic Antioxidant Performance of Lignin and Quercetin Mixtures

A natural, effective, and inexpensive hindered phenolic antioxidant mixture was prepared by blending lignin into quercetin. The antioxidant performance of lignin and quercetin mixture was analyzed by determining the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and a low-cost and high-efficiency ratio was found to be 4:1 (w/w). After UV radiation for 4 h, the DPPH scavenging ratio of the quercetin/lignin mixture decreased only 13.8%, while that of quercetin and lignin decreased 42.9% and 28.6%, respectively. The UV and fluorescence analysis indicated that quercetin molecules inserted into the lignin to weaken its aggregation and form new conjugated structures. Adding lignin may provide a green alternative to the expensive quercetin or synthetic antioxidants used in food, cosmetics, and pharmaceuticals