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The valorization of the black liquor produced during the chemical pulping of wheat straw is the key to the sustainable use of this abundant agricultural waste. However, the silica problem has hampered the recovery process. Herein, nanoprecipitation technology was used to produce lignin nanoparticles (LNPs) from wheat straw black liquor using γ-valerolactone (GVL) as a solvent and water as an anti-solvent. The results showed that a uniform, well-dispersed, and stable LNP was produced. The particle size and Zeta potential of 161 nm and −24 mV of the LNP suspension were obtained at a GVL concentration of 87%. The chemical structure and bonding of the lignin were adequately preserved after nanoprecipitation based on two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, Fourier transform infrared (FTIR) analysis, and thermal stability was improved based on thermogravimetric analysis. In addition, the abundant phenolic hydroxyl groups of LNP quantified by 31P-NMR analysis are beneficial for chemical cross-linking and modification. This work not only achieved the valorization of wheat straw black liquor but also opened up a new avenue for advanced nanomaterials. [ABSTRACT FROM AUTHOR]

The valorization of the black liquor produced during the chemical pulping of wheat straw is the key to the sustainable use of this abundant agricultural waste. However, the silica problem has hampered the recovery process. Herein, nanoprecipitation technology was used to produce lignin nanoparticles (LNPs) from wheat straw black liquor using γ-valerolactone (GVL) as a solvent and water as an anti-solvent. The results showed that a uniform, well-dispersed, and stable LNP was produced. The particle size and Zeta potential of 161 nm and −24 mV of the LNP suspension were obtained at a GVL concentration of 87%. The chemical structure and bonding of the lignin were adequately preserved after nanoprecipitation based on two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, Fourier transform infrared (FTIR) analysis, and thermal stability was improved based on thermogravimetric analysis. In addition, the abundant phenolic hydroxyl groups of LNP quantified by 31P-NMR analysis are beneficial for chemical cross-linking and modification. This work not only achieved the valorization of wheat straw black liquor but also opened up a new avenue for advanced nanomaterials.

Efficient wound healing is feasible when the dressing materials simultaneously target multiple factors causing wound chronicity, such as deleterious proteolytic and oxidative enzymes and bacterial infection. Herein, entirely bio-based multifunctional self-assembled hydrogels for wound healing were developed by simply mixing two biopolymers, thiolated hyaluronic acid (HA-SH) and silk fibroin (SF), with lignin-based nanoparticles (NPs) as both structural and functional elements. Sono-enzymatic lignin modification with natural phenolic compounds results in antibacterial and antioxidant phenolated lignin nanoparticles (PLN) capable of establishing multiple interactions with both polymers. These strong and dynamic polymer-NP interactions endow the hydrogels with self-healing and shear-thinning properties, and pH-responsive NP release is triggered at neutral to alkaline pH (7–9). Despite being a physically crosslinked hydrogel, the material was stable for at least 7 days, and its mechanical and functional properties can be tuned depending on the polymer and NP concentration. Furthermore, human skin cells in contact with the nanocomposite hydrogels for 7 days showed more than 93% viability, while the viability of clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa was reduced by 99.7 and 99.0%, respectively. The hydrogels inhibited up to 52% of the activity of myeloperoxidase and matrix metalloproteinases, responsible for wound chronicity, and showed a strong antioxidant effect, which are crucial features promoting wound healing. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles (LNPs), as a new type of green nanomaterial, initiate many promising applications in polymer composites. However, their heterogeneity, dissolution in organic solvents, and poor compatibility in the polymer matrix greatly limited the applications of LNPs fillers. Herein, we proposed an antisolvent precipitation of the fractionations by combining a hydrothermal treatment-assisted synthesis to fabricate self-crosslinked LNPs (ScLNPs), which have good stability in the organic solvent and controllable sizes. After surface grafting modification with d -lactide, ScLNPs- graft -poly(d -lactide) (ScLNPs- g -PDLA) exhibited excellent dispersion and compatibility in PLLA matrix. Using the rational design and addition of ScLNPs- g -PDLA fillers, the strength and toughness of the generated PLLA composite reached 31.6 MPa and 396 % (the highest value among the PLLA materials), respectively. Furthermore, the mechanical performance can also be well-tuned by the sizes and amounts of LNPs fillers. This strategy involving only green and recyclable materials provides an effective route to producing sustainable polymeric plastics with integrated strength and super-toughness. • Self-crosslinked LNPs were prepared by a crosslinker-free route. • ScLNPs have controllable sizes and good stability in the organic solvent. • ScLNPs- g -PDLA/PLLA exhibits supertough and strong performance. • The mechanical properties of the composites can be well-tuned by LNPs fillers. [ABSTRACT FROM AUTHOR]

Lignocellulose nanofibrils (LCNFs) are nano-objects that contain lignin. The presence of lignin in the fibrils affects the process production of cellulose nanofibrils. It modifies the morphology of fibrils produced and the rheological behavior of suspensions, which is crucial in developing applications for this material. This work aims to understand the role of lignin in the mechanical-enzymatic production process of LCNFs and the morphological, superficial, and rheological properties of LCNF suspensions. Lignin has a negative effect on the mechanical and enzymatic processes, generating larger fibrils with less homogeneous size distributions and with lower zeta potential. In addition, the composition of the fibrils changes, part of the lignin is removed and dispersed into the solvent in the form of lignin nanoparticles. These nanoparticles are neutral and can be deposited on the surface of the fibrils. Regarding rheological properties, fibrils with lignin are less flexible than bleached fibrils. Such characteristics are due to the cementing capacity of lignin, which increases the hydrodynamic volume that these structures occupy per unit mass. Furthermore, in the semi-dilute region, lignin acts as a control agent for the viscosity in the suspensions due to its hydrophobic characteristic, which forms weak aggregates, poorly hydrated, and hydrodynamically smaller, which generate less resistance to flow. [ABSTRACT FROM AUTHOR]

Multifunctional conductive hydrogels have shown great promise in wearable flexible sensor application. This paper reported a dual-network self-healing electrically hydrogel through simple one-pot polymerization, which initiated from Ag+- lignin nanoparticles (LNPs) -APS redox system. Owing to the reversible metal coordination and hydrogen bonding cross-linked among polymer network, the resulting conductive hydrogel-based sensor demonstrated excellent stretchable, adhesion strength, and fatigue resistance. Additionally, the complex hydrogel (PHEMA/SA/Gly/Ca) incorporating with glycerol and CaCl 2 in particular exhibited strong frost resistance (−40oC) and moisturizing qualities to monitor the motion signals in the low-temperature dry state. Therefore, the fabricated wearable sensor is sufficient for detecting large and small human motions, suggesting lots of promising applications in electronic skins, information identification and encryption, and human-motion monitoring. [Display omitted] • A multifunctional dual-network polymer conductive hydrogel was mild fabricated. • The hydrogel exhibited excellent adhesion strength to various material surfaces. • Glycerol and CaCl 2 invested complex hydrogel exceptional frost resistance (−40 °C). • The self-healing dual-network hydrogel possess excellent moisturizing property. • The hydrogel had application as wearable strain sensors to detect human movement. [ABSTRACT FROM AUTHOR]

We study the effect of electrolytes on the stability in aqueous media of spherical lignin particles (LP) and its relevance to Pickering emulsion stabilization. Factors considered included the role of ionic strength on morphology development, LP size distribution, surface charge, interfacial adsorption, colloidal and wetting behaviors. Stable emulsions are formed at salt concentrations as low as 50 mM, with the highest stability observed at a critical concentration (400 mM). We show salt-induced destabilization of LP aqueous dispersions at an ionic strength >400 mM. At this critical concentration LP flocculation takes place and particulate networks are formed. This has a profound consequence on the stability of LP-stabilized Pickering emulsions, affecting rheology and long-term stability. The results along with quartz microgravimetry and confocal microscopy observations suggest a possible mechanism for stabilization that considers the interfacial adsorption of LP at oil/water interfaces. The often-unwanted colloidal LP destabilization in water ensues remarkably stable Pickering emulsions by the effect of network formation. [ABSTRACT FROM AUTHOR]

Herein, we innovatively synthesized an ionic conductive PVA/LNP hydrogel with integrated excellent mechanical, anti-freezing, moisturizing, transparent and UV-shielding performances via incorporating nanolignin (also called lignin nanoparticle, LNP) and aluminum chloride (AlCl 3) into polyvinyl alcohol (PVA) matrix containing ethylene glycol/water (EG/H 2 O) binary solvent. The rigid porous network structure was well constructed by the hydrogen bond interactions among the evenly distributed LNP and PVA chains, thus providing abundant ion transport channels, which attributed to the outstanding ionic conductivity (up to 1.35 × 10−2 S/m, at −24 °C) with improved mechanical strength and flexibility. The tensile strength and elongation at break of PVA/LNP hydrogel were greatly increased from 574.6 kPa and 363.7% to 1241.4 kPa and 589% at the addition of 0.35% LNP, respectively. In addition, the UV-resistance ability was 95% at 365 nm, while the transparency was 74% at 550 nm. The binary solvent of EG and H 2 O ensured long-term moisturizing capability (10 days) of the hydrogel at 35 °C and 60 RH%, as well as possessing superior anti-freezing performance over the temperature range of −62.6 to 24 °C. As a result, the fabricated PVA/LNP hydrogel was successfully used as strain sensor for detecting diverse human motions and electrophysiological signals. • A novel high strength conductive PVA/LNP hydrogel was fabricated and exhibits excellent performance as strain sensor. • Lignin nanoparticle acted as a spacer to construct a rigid porous network structure during the formation of PVA hydrogel. • The porous network offered numerous channels for ion transport, thus enhancing conductive properties and mechanical. • The binary solvent in the hydrogel endowed long-term moisturizing capability and superior anti-freezing performance. [ABSTRACT FROM AUTHOR]

Cellulose nanofibril (CNF) films have attracted great attention in food packaging application due to their excellent mechanical strength and oxygen barrier properties. If antibacterial nanoparticles are incorporated into CNF films, the generated antibacterial CNF films would further improve their packaging performance. Since the commonly used inorganic nanoparticles would persist in the environment after usage, biopolymer-based nanoparticles are highly desirable. Herein, novel antibacterial lignin nanoparticles were designed by the nanoprecipitation of the tetrahydrofuran (THF) solution of lignin into the aqueous solution of polyhexamethylene guanidine hydrochloride (PHGH). The as-fabricated spherical PHGH-LNPs had an average diameter of 135 ± 2 nm and zeta potential of approximately 50 mV with an excellent pH (4–10) and time stability (even after storage for 90 days). Due to the positive charge of PHGH-LNPs and the hydrophilic character of PHGH, the nanoparticles displayed a good dispersion in the CNF slurry. PHGH-LNPs/CNF films were obtained by further solvent casting. The excellent compatibility between PHGH-LNPs and CNFs leaded to the composite film with a similar tensile strength and unapparent fibril structure in comparison with that of the pristine CNF film. In particular, the PHGH-LNPs/CNF film at a nanoparticle dosage of 8 wt% presented a water vapor barrier ratio of 34% and 100% inhibition against both L. monocytogenes and E. coli. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advancements in isolation methods of various LNPs are reviewed. • Structural, thermal, and macromolecular properties of LNPs are discussed. • Beneficial uses of LNPs as a natural antioxidant are suggested. • Research challenges and future perspectives related to the use of LNPs are emphasized. Over 220 million tonnes of biomass waste are generated annually around the world. One of the biomasses generated is lignocellulosic biomass which consists of lignin, cellulose, and hemicellulose. Since lignin possesses numerous unique qualities, researchers ought to substitute lignin for high value-added applications. However, lignin's properties such as irregular shape, heterogeneity, low dispersity, and large particle size have limited its capability for high value-added applications. Thus, the conversion of lignin into lignin nanoparticles (LNPs) has gained much attention in the research community. The present review aims to educate readers about the techniques employed to isolate LNPs, including physical and chemical approaches which influence the properties of LNPs. Characterization methods for LNPs, including structural, thermal, molecular weight, microstructural, and macromolecular properties are further discussed. Various determination methods pertaining to antioxidant activity of LNPs such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), TEAC (Trolox equivalent antioxidant capacity) assay, and oxygen uptake inhibition (OUI) are reviewed. This review also details the recent advancements of LNPs as antioxidants. Prospects and challenges in the development of LNPs are also highlighted. [ABSTRACT FROM AUTHOR]

The biocompatible, biodegradable and strong polyvinyl alcohol-based films have been widely investigated and used in the field of active packaging. To endow with diverse function, this paper firstly prepared lignin nanoparticles loaded with potassium sorbate (LNP@PS) as additives to exploit additional antibacterial, UV blocking, oxygen barrier, and water barrier properties. Besides, tannin acid (TA) was incorporated for compensating and further enhancing mechanical properties. Results showed that the PVA-based composite films containing 3 % LNP@PS and 5 % TA could achieve the optimal tensile strength at 74.51 MPa, water vapor permeability at 7.015·10−13·g·cm/cm2·s·Pa and oxygen permeability at 1.93 cm3/m2·24 h MPa, which was an 165 % of increase, 47 % and 112 % of reduction respectively compared to pure PVA films. Additionally, the composite films exhibited apparently superior bacteria and oxygen resistance properties evidenced by microbial infection and free radical scavenging performance. In addition, the slow-release effect of PS assisted the strawberry preservation with an extension of 3 days, which provided a promising novel route to prepare active food packaging material. [ABSTRACT FROM AUTHOR]

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Efficient wound healing is feasible when the dressing materials simultaneously target multiple factors causing wound chronicity, such as deleterious proteolytic and oxidative enzymes and bacterial infection. Herein, entirely bio-based multifunctional self-assembled hydrogels for wound healing were developed by simply mixing two biopolymers, thiolated hyaluronic acid (HA-SH) and silk fibroin (SF), with lignin-based nanoparticles (NPs) as both structural and functional elements. Sono-enzymatic lignin modification with natural phenolic compounds results in antibacterial and antioxidant phenolated lignin nanoparticles (PLN) capable of establishing multiple interactions with both polymers. These strong and dynamic polymer-NP interactions endow the hydrogels with self-healing and shear-thinning properties, and pH-responsive NP release is triggered at neutral to alkaline pH (7–9). Despite being a physically crosslinked hydrogel, the material was stable for at least 7 days, and its mechanical and functional properties can be tuned depending on the polymer and NP concentration. Furthermore, human skin cells in contact with the nanocomposite hydrogels for 7 days showed more than 93% viability, while the viability of clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa was reduced by 99.7 and 99.0%, respectively. The hydrogels inhibited up to 52% of the activity of myeloperoxidase and matrix metalloproteinases, responsible for wound chronicity, and showed a strong antioxidant effect, which are crucial features promoting wound healing.

Owing to the low synthetic cost, low toxicity for most types and outstanding lignin solubility, deep eutectic solvents (DESs) have been recently exploited in fractionation of lignocellulosic biomass. Unfortunately, the DES-fractionated lignin, as another major product, was usually ignored and disposed improperly. Accordingly, the present study employed DES (choline chloride:lactic acid) to fractionate natural biomass for producing highly dispersed lignin nanoparticles. The obtained nano-lignin was utilized to prepare electrode materials for supercapacitors for the first time, and a higher specific capacitance than those prepared from conventional lignin was acquired. The results demonstrated that the lignin fractionation rate could be promoted via extending treatment time at low temperatures, whereas the DES to biomass mass ratio might be the lignin dissolution-limiting factor at high temperature. Uniform lignin nanoclusters could be obtained after DES fractionation, and increasing fractionation temperature was beneficial for preparing nano-lignin in DES. The cleavages of lignin-carbohydrate complexes and lignin subunits might account for the formation mechanism of lignin oligomers. Meanwhile, the aggregation of monolignols could contribute to the growth of lignin nanoparticles. The one-step KOH activation could induce hierarchical pores in lignin fractionated from moderate residence time, whereas two-step method was advisable for more aggregated DES-lignin. Based on the directly activated DES-lignin with a high surface area of 3577.3 m2 g−1, the prepared supercapacitor exhibited a superior specific capacitance of 248.8 F g−1. This study aimed to provide a novel method for producing high-performance energy storage carbon materials based on DES fractionated lignin from lignocellulose. [Display omitted] • Above 60 wt% of lignin could be extracted from biomass in ChCl:LA type of DES. • Lignin nanoparticles with good uniformity of particle size were obtained. • Cyan-fluorescent lignin-based carbon dots were obtained along with fractionation. • One-step activation could produce hierarchical pores in less aggregated lignin. • The specific capacitance of activated DES-lignin reached 248.8 F g−1 at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles (LNP) were obtained by an acidolysis process from corn pristine lignin. X-ray photoelectron spectroscopy (XPS) and radical scavenging activity (RSA) of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) confirmed a significant enhancement in reactivity of LNP in comparison with pristine lignin. Polyurethane (PU) nanocomposites were prepared by pre-polymerization of polyethylene glycol and diisocyanates in the presence of different contents (1, 3, 5 and 7 wt%) of LNP. The effects of LNP, serving as both biobased polyol and crosslinker, on the mechanical, hydrophobicity and dielectric behavior of the resulted PU nanocomposites were investigated. Tensile test results showed an overall enhancement for mechanical performance, and the elongation at break exceeded 1000% for all studied PU nanocomposites. Meanwhile, dynamic mechanical analysis (DMA) revealed that the crosslinking densities gradually increased with LNP addition. Furthermore, LNP based PU nanocomposites showed inherent resistance towards ultraviolet radiation and frequency dependent behavior for electrical conductivity. On the other hand, LNP based PU nanocomposites revealed good thermal reprocessability due to the transcarbamoylation reaction in the presence of DBTDL catalyst.

Natural biopolymer nanoparticles (NPs), including nanocrystalline cellulose (CNC) and lignin, have shown potential as scaffolds for targeted drug delivery systems due to their wide availability, cost‐efficient preparation, and anticipated biocompatibility. As both CNC and lignin can potentially cause complications in cell viability assays because of their ability to scatter the emitted light and absorb the assay reagents, we investigated the response of bioluminescent (CellTiter‐Glo®), colorimetric (MTT® and AlamarBlue®), and fluorometric (LIVE/DEAD®) assays for the determination of the biocompatibility of the multimodal CNC and lignin constructs in murine RAW 264.7 macrophages and 4T1 breast adenocarcinoma cell lines. Here, we have developed multimodal CNC and lignin NPs harboring the radiometal chelator 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid and the fluorescent dye cyanine 5 for the investigation of nanomaterial biodistribution in vivo with nuclear and optical imaging, which were then used as the model CNC and lignin nanosystems in the cell viability assay comparison. CellTiter‐Glo® based on the detection of ATP‐dependent luminescence in viable cells revealed to be the best assay for both nanoconstructs for its robust linear response to increasing NP concentration and lack of interference from either of the NP types. Both multimodal CNC and lignin NPs displayed low cytotoxicity and favorable interactions with the cell lines, suggesting that they are good candidates for nanosystem development for targeted drug delivery in breast cancer and for theranostic applications. Our results provide useful guidance for cell viability assay compatibility for CNC and lignin NPs and facilitate the future translation of the materials for in vivo applications. [ABSTRACT FROM AUTHOR]

Conductive hydrogels have attracted considerable interest for potential applications in soft robotics, electronic skin and human monitoring. However, insufficient mechanical characteristics, low adhesion and unsatisfactory electrical conductivity severely restrict future application possibilities of hydrogels. Herein, lignin nanoparticles (LNPs)-Fe3+-ammonium persulfate (APS) catalytic system was introduced to assemble Poly(2-hydroxyethyl methacrylate)/LNPs/Ca2+ (PHEMA/LNPs/Ca) hydrogels. Due to the abundant metal coordination and hydrogen bonds, the composite hydrogel displayed ultrahigh stretchable capacity (3769 %), adhesion properties (248 kPa for skin) and self-healing performance. Importantly, hydrogel sensors possess with high durability, strain sensitivity (GF = 8.75), fast response time and freeze resistance (−20 °C) that could be employed to monitor motion signals in low-temperature regime. Therefore, the LNPs-Fe3+ catalytic system has great potential in preparing hydrogel for various applications such as human-computer interaction, artificial intelligence, personal healthcare and subzero wearable devices. At the same time, incorporation of natural macromolecules into polymer hydrogels is tremendous research significance for investigating high-value utilization of lignin. [Display omitted] • Lignin based hydrogels via metal coordination and hydrogen bonds were fabricated. • Self-healing hydrogels possess highly flexibility (3769 %) and repeated adhesiveness. • Introducing Ca2+ improved hydrogels conductivity and anti-freezing performance. • Hydrogels demonstrated excellent tensile and pressure strain sensitivity (GF = 8.75). [ABSTRACT FROM AUTHOR]

In this work, pectin-lignin nanoparticle (LNP) composite films were prepared, the physical, antioxidant and antibacterial properties of the films systematically evaluated. The LNP were compatible with the pectin matrix, and the tensile strength (TS) and water contact angle (WCA) of the pectin-based films were enhanced by 164% and 56% at the optimum LNP loading of 3.0% (w/w). The results of dynamic WCA demonstrate the hydrophobic stability of pectin-LNP composite films. Even trace amounts of LNP (1.0%, w/w) were found to significantly improve the mechanical properties (TS improved 67.33%), hydrophobicity (WCA improved 48.83), and water barrier properties (the water vapor permeability decreased by 25.30%) of the pectin-based films. The tight entanglement and strong positive interaction between pectin and LNP promote the formation of dense structures, which is beneficial to the film properties. In addition, all pectin-LNP composite films almost completely shield the UVB (320-275 nm) and UVC (275-200 nm) spectrum, along with most of the UVA (400–320 nm) spectrum, which demonstrates their strong anti-ultraviolet performance. In terms of bioactivity, the addition of LNP significantly enhanced the DPPH radical scavenging ability (maximum boost is 6.33 times) and antibacterial ability (maximum inhibition rate was 78.79 for S.aureus and 47.80% for E.coli) of the pectin film. These results suggest that the pectin-LNP composite film are promising active packaging materials for food preservation/packaging applications. [Display omitted] • Pectin-lignin nanoparticle (LNPs) composite films were prepared. • LNPs were uniformly dispersed in pectin-based films (high compatibility). • LNPs addition enhanced the mechanical and hydrophobic properties of pectin films. • The composite films showed good anti-UV, antioxidant, and antibacterial activities. • The composite films have great potential for active food packaging. [ABSTRACT FROM AUTHOR]

Recently, transparent wood (TW) has been considered for many applications, such as windows, energy storage, and electronic devices. This study presents the fabrication of eco-friendly TW using waste lignin as a resource to enhance the TW's performance by providing UV-shielding functionality. Three different pretreatment methods were explored for TW fabrication, including solar-assisted bleaching, steam bleaching, and NaOH delignification. The average size of the lignin nanoparticles (LNs) characterized using a scanning electron microscope and nanoparticle analyzer and was found to be around 100 nm. The LNs had zeta potentials of − 44.2 mV to − 34.9 mV for the first and sixth months, respectively. The transmittance of TW ranged from 20% to 80%, depending on the pretreatment and additional LNs content. By incorporating just 1% of LN, the TW composites were found to effectively block all UV-C, UV-B, and UV-A radiation while maintaining adequate visible light transmittance. The thermal stability, crystallinity index, and mechanical properties of wood and TW were investigated and compared. The NaOH delignification TW (Na-TW) has shown the highest transmittance, tensile strength, UV-shielding functionality, and comparable thermal stability with solar transparent wood (SL-TW) and steam transparent wood (ST-TW) methods. These findings indicate that TW LNs nanocomposite is a promising candidate for UV-shielding window applications. [Display omitted] • Transparent wood was fabricated by infiltrating lignin nanoparticles (LNs). • Transparent wood offered good transparency, UV-shielding, mechanical properties. • 1% LNs contained wood shows good transparence and UV-shielding. • Eco-friendly transparent wood was fabricated using waste lignin. [ABSTRACT FROM AUTHOR]

The valorization of the black liquor produced during the chemical pulping of wheat straw is the key to the sustainable use of this abundant agricultural waste. However, the silica problem has hampered the recovery process. Herein, nanoprecipitation technology was used to produce lignin nanoparticles (LNPs) from wheat straw black liquor using γ-valerolactone (GVL) as a solvent and water as an anti-solvent. The results showed that a uniform, well-dispersed, and stable LNP was produced. The particle size and Zeta potential of 161 nm and -24 mV of the LNP suspension were obtained at a GVL concentration of 87%. The chemical structure and bonding of the lignin were adequately preserved after nanoprecipitation based on two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, Fourier transform infrared (FTIR) analysis, and thermal stability was improved based on thermogravimetric analysis. In addition, the abundant phenolic hydroxyl groups of LNP quantified by 31 P-NMR analysis are beneficial for chemical cross-linking and modification. This work not only achieved the valorization of wheat straw black liquor but also opened up a new avenue for advanced nanomaterials.

A rapid and green preparation of lignin nanoparticles was demonstrated starting from bio-refinery lignin containing grafted carbohydrates. The particles were prepared by recovering a fraction of the lignin, which contained 24% carbohydrate (by weight) as the insoluble fraction in 0.5 M NaOH. The carbohydrate content of this fraction was verified with a wet chemistry analytical technique, nuclear magnetic resonance, and X-ray diffraction. This fraction was then dissolved in a NaOH/urea/water system and added dropwise to water under a high shear, which rapidly formed precipitated particles in a size range of approximately 100 nm. This carbohydrate-containing fraction of the lignin was soluble in a green solvent system that was not suited for lignin alone. The generated particles were stable in different organic solvents and water. Overall, the dissolution of the bio-refinery lignin in the NaOH/urea/water system, followed by precipitation in water can be regarded as a green and rapid method to produce stable nanoparticles. The generated nanoparticles, containing both carbohydrates and lignin, are expected to have unique applications because of their bi-component nature. Furthermore, this is the first publication to show how materials with high levels of lignin can be solubilized in solvents that are conventionally used for cellulose. [ABSTRACT FROM AUTHOR]

Abstract Biorenewable polymers from natural resources have attracted a greater attention of the research for different applications. In this work, renewable lignin nanoparticles (LNP) were employed as cross-linking junctions to prepare high mechanical properties hydrogel, polyacrylamide/lignin nanoparticle (PAM/LNP) nanocomposite hydrogel. The hydrogel exhibits high compressive and tensile strengths as well as excellent recoverability. The fracture strength of the PAM/LNP hydrogel under compressive stress is on the order of megapascals, which is several orders of magnitude higher than those of pure PAM hydrogel. The synergic improving effect of nanocomposite network structure and the strong H-bonding between polymer chains endow the hydrogel with an excellent mechanism of distributing the applied load. Considering good mechanical properties, simple synthesis methods and noncytotoxicity, this high performance hydrogel material has potential applications in biomedical fields, such as tissue engineering or regeneration, artificial muscles, strong underwater antifouling materials, and so on. [ABSTRACT FROM AUTHOR]

Cross-linked and decolorized lignin nanoparticles (LNPs) were prepared enzymatically and chemically from softwood Kraft lignin. Colloidal lignin particles (CLPs, ca. 200 nm) in a non-malodorous aqueous dispersion could be dried and redispersed in tetrahydrofuran (THF) or in water retaining their stability i.e. spherical shape and size. Two fungal laccases, Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) were used in the cross-linking reactions. Reactivity of ThL and MaL on Lignoboost™ lignin and LNPs was confirmed by high performance size exclusion chromatography (HPSEC) and oxygen consumption measurements with simultaneous detection of red-brown color due to the formation of quinones. Zeta potential measurements verified oxidation of LNPs via formation of surface-oriented carboxylic acid groups. Dynamic light scattering (DLS) revealed minor changes in the particle size distributions of LNPs after laccase catalyzed radicalization, indicating preferably covalent intraparticular cross-linking over polymerization. Changes in the surface morphology of laccase treated LNPs were imaged by atomic force (AFM) and transmission emission (TEM) microscopy. Furthermore, decolorization of LNPs without degradation was obtained using ultrasonication with H 2 O 2 in alkaline reaction conditions. The research results have high impact for the utilization of Kraft lignin as nanosized colloidal particles in advanced bionanomaterial applications in medicine, foods and cosmetics including different sectors from chemical industry. [ABSTRACT FROM AUTHOR]

The inherent complexity and large particle size of native-state lignin are the major factors limiting its performance in high value-added materials. To realize the high-value application of lignin, nanotechnology is a promising method. Therefore, we offer a nanomanufacturing approach to produce lignin nanoparticles with uniform size, regular shape and high yield using electrospray. They are efficient in stabilizing oil-in-water (O/W) Pickering emulsions that remain for one month. Lignin has the abilities to demonstrate broad-spectrum UV resistance and green antioxidant properties in advanced materials, taking advantage of its inherent chemical characteristics. In addition, lignin has high safety for topical products according to an in vitro cytotoxicity test. In addition, the nanoparticle concentrations used in the emulsion were as low as 0.1 mg/ml, which maintained UV-resistant ability and overcame traditional lignin-based materials with unfavorable dark colors. Overall, lignin nanoparticles not only act as stabilizers at the water-oil interface but also realize the high functionality of lignin. [Display omitted] • A simple method for preparing lignin nanoparticle by electrospray technology • Morphological modification lignin acts as stabilizer at Pickering emulsion. • The emulsion overcomes lignin materials with dark color and keeps anti-UV ability. • Lignin with broad-spectrum UV barrier, antioxidant activity and biological safety [ABSTRACT FROM AUTHOR]

In this study, we innovatively synthesized a multifunctional PVA/PU-LNP composite hydrogel with integrated distinguished UV-blocking, mechanical strength, dynamic viscoelasticity and thermal properties by introducing lignin nanoparticle (LNP) into polyvinyl alcohol (PVA) and polyurethane (PU) mixed matrix through freeze-thaw cycle. The rigid porous network structure was established by hydrogen bond interactions among the well-distributed LNP and PVA/PU molecular chains, which endowed excellent mechanical strength, viscoelasticity, thermal stability and flexibility with PVA/PU-LNP composite hydrogel. The elongation at break and tensile strength of PVA/PU-LNP composite hydrogel were markedly improved from 227.3 % and 247.1 KPa to 460.1 % and 950.4 KPa with the LNP loading of 2 % based on PVA weight, respectively. Meanwhile, PVA/PU-2%LNP hydrogel exhibited prominent compressive resistance and pleasing shape recovery capability. Moreover, the blending of LNP at a low dosage (0.5 %) based on PVA weight effectively shielded 99.34 % of UV light and penetrated 42.27 % of visible light, indicating that PVA/PU-LNP composite hydrogel demonstrated outstanding anti-UV performance. In addition, the incorporation of LNP caused a remarkable decline in the pore size of PVA/PU-LNP composite hydrogel (4.39 ± 0.46 μm to 1.54 ± 0.22 μm), which slightly reduced water uptake capacity of composite hydrogel. Therefore, this work provided a new approach to constructing a multifunctional composite hydrogel. • A multifunctional hydrogel was fabricated through freeze-thaw cycle. • The hydrogel was fabricated by introducing lignin nanoparticle into polyvinyl alcohol and polyurethane mixed matrix. • The hydrogel possesses distinguished UV-blocking, mechanical strength, dynamic viscoelasticity and thermal properties. [ABSTRACT FROM AUTHOR]

Chitosan (CS) films have demonstrated strong antibacterial properties, excellent biocompatibility and biodegradability, but poor UV blocking, oxygen and water barrier and mechanical properties limit their application in antimicrobial food packaging. In this study, CS films were incorporated with nanofillers, including lignin nanoparticles (LNP, 1–5 wt %) and acylated soy protein isolate nanogel (ASPNG, 3–7 wt %) to improve their tensile strength, oxygen and water barrier, UV blocking and antibacterial properties. SEM images illustrated that the addition of LNP and ASPNG significantly affected the surface morphology of the CS film. Meanwhile, LNP incorporation improved UV blocking property of composite film, while an improved sustained antibacterial property was achieved with ASPNG incorporation. Interestingly, CS composite film incorporated with 3% LNP and 5% ASPNG showed a remarkable increase in tensile strength (37.29–54.29 MPa) and decreased oxygen barrier property (5.73–2.83 cm3/m2·24 h MPa) relative to pure CS film. It is worth mentioning that the bacterial counts in samples treated by 3% LNP/5% ASPNG-CS composite film decreased approximately 2.37 log CFU/mL, which exhibited higher antibacterial activity than other composite films. However, this study also demonstrated that incorporation of LNP and ASPNG slightly decreased the light transmission and increased surface roughness of CS film. All in all, the CS composite film with enhanced mechanical, barriers, antibacterial properties were obtained by incorporating an appropriate proportion of LNP and ASPNG and could further be utilized as a promising antibacterial food packaging material. [Display omitted] • Lignin nanoparticles (LNP) and acylated soy protein isolate nanogel (ASPNG) were fabricated. • LNP and ASPNG incorporation improved tensile strength and elongation at break of the film. • LNP and ASPNG incorporation improved oxygen and water vapor barrier properties of the film. • 3% LNP/5% ASPNG enhanced CS film's potassium sorbate sustained release ability. • 3% LNP/5% ASPNG-CS film had higher antibacterial activity than pure chitosan film. [ABSTRACT FROM AUTHOR]

Foam is a thermodynamically unstable dispersion system, and the stability of foam under severe conditions is still a bottleneck restricting the application. Exploring the stabilization mechanism of foam and new ways to improve foam stability has always been a concern in related fields. Based on global attention to environmental friendliness, enhancing foam performance using green biomaterials is of great significance. This study explored the foam properties generated by the composite solution of bio-based lignin nanoparticles (LNPs) and surfactant. Experimental results show that, the composite foam is much more stable compared with the pure surfactant foam. The half-life time t 1/2 was 10 times higher than that of the pure surfactant foam at 423 K, and the dynamic stability of the foam under shear disturbance was significantly improved, too. A variety of experimental methods are used to investigate the foam stabilization mechanism of the composite system, and it was verified that the LNPs combined with the surfactant molecules both in bulk phase and at gas/water interface. The surfactant molecules arrange more closely at the interface, decrease the surface tension. The LNPs were carried into the foam films and the drained films could be 2–4 times thicker than pure AOS foam, which slow down the rate of gas permeating across the films and increase the strength and liquid carrying ability of liquid film. The decrease of the drainage rate and the maintaining of the thickness of the foam film both could be helpful for strengthen of the foam stability, even under harsh conditions such as high temperature and shear disturbance. Compared with water-soluble polymers, inorganic NPs and other artificially synthesized foam co-stabilizers, LNPs are of natural origin, degradable, stable in structure and have outstanding environmental-friendly superiority. The excellent performance of the green aqueous foam system composed of lignin NPs and surfactants revealed in this research shows good application prospects in the enhanced oil recovery and daily chemistry fields. [Display omitted] [ABSTRACT FROM AUTHOR]

• TEMPO-oxidized nanocellulose lacks chemical, thermal, and color stability. • Removing unstable sodium carboxylate moieties was crucial to increase stability. • Two approaches were used to obtain stable nanocomposites for long-term applications. • Alkali-acid post-treatment removed the chemical groups that promote degradation. • Addition of antioxidant nanolignin also improved the aging performance. Cellulose oxidation catalyzed by TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) is a trending methodology to enable the fibrillation and production of large amounts of cellulose nanofibrils (CNF) in a cost-effective and energy-saving manner. However, TEMPO-oxidized CNF lack colorimetric, thermal, and physicochemical stability due to intrinsic structural characteristics, i.e., the presence of sodium carboxylate functional groups and anhydroglucuronate units of low molecular weight. The susceptibility of CNF to deterioration at moist-heat conditions can negatively impact the use of these promising nanomaterials in long-term applications, such as protective coatings and electronic devices. Herein, we showed that the incorporation of lignin nanoparticles (LNP) enhanced the resistance to degradation of nanocomposite films based on nanocelluloses (CNF and cellulose nanocrystals). The improvement of the aging performance in nanolignin-containing films was attributed to the higher antioxidant capacity provided by lignin, which also imparted UV-protection. Alternatively, the removal of unstable functional groups and residues in TEMPO-oxidized CNF by an alkali-acid post-treatment was also proven effective in imparting higher thermal, physicochemical, and colorimetric stability to CNF and nanocomposite films. Therefore, the incorporation of LNP or the implementation of a post-treatment protocol into CNF are diverse, yet simple and efficient strategies to enable the application of these bio-based green nanomaterials into durable products. [Display omitted] [ABSTRACT FROM AUTHOR]

Achieving efficient exploitation of agricultural waste is of great significance for future biorefinery. A green deconstruction strategy of lignocellulose exerts an immense impact on their conversion and lignin valorization. Deep eutectic solvent (DES) as eco-friendly solvents can sufficiently fractionate lignin from lignocellulose, and the considerate comprehension of fundamental chemistry of lignin would facilitate the process optimization and tailored upgrade of lignin in biorefinery. Herein, three different DESs, including acidic and alkaline systems, were adopted to deconstruct raw and hydrothermal tobacco stalk under certain conditions, gaining different lignin fractions. Structural transformation of recovered lignin macromolecules during acidic and alkaline DES delignification has been investigated in comparison with mill wood lignin (MWL) via state-of-the-art NMR spectra, GPC, FTIR, and TGA techniques. Results showed that hydrothermal pretreatment facilitated the yields (from 35.6% to 46.0% to 43.1–58.5%) and molecular weights (from 1310 to 2280 g/mol to 1600–2400 g/mol) of the recovered DES lignin. Moreover, acidic DES lignin presented significantly fragmented (without β- O -4 linkage) and condensed structures as well as the lower molecular weight, while a well-preserved structure (~50/100 Ar β- O -4 linkage) and fewer hydroxyl groups were observed in alkaline DES ones. Furthermore, these lignins displayed structure-dependent nanoparticle size, excellent UV absorption, and antioxidant activity, offering a crucial foundation for the targeted valorization of lignin from agricultural waste. • Lignin was comparatively isolated by acidic and alkaline deep eutectic solvents from tobacco stalk. • Acidic and alkaline deep eutectic solvents exhibited distinctly different routes on lignin depolymerization. • Recovered lignins showed nanoparticle size that is dependent on their macromolecular structure. • Recovered lignins are promising precursors for fabricating lignin-based functional materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin nanoparticles (LNs) are prepared by self-assembly in DMSO/H 2 O binary solvent. • LNs significantly reinforce mechanical properties of nanocomposite organogels. • Organogels exhibit incredible freezing tolerance even at −80 °C and anti-dehydration ability with 88% weight retention. • Organogels serve as flexible strain sensors to detect signals in extreme conditions. Despite the remarkable progress in efforts to fabricate flexible and wearable sensors based on the conductive hydrogels has been witnessed in recent years, the traditional conductive hydrogels still suffer from poor mechanical properties and intrinsic instability owing to the inevitable freeze at low temperature and water evaporation at room temperature, severely limiting their practical applications. Herein, we developed a robust and conductive lignin-based nanocomposite organogel with extreme temperature tolerance and long-lasting moisture, which is prepared in a binary-solvent system composed of dimethyl sulfoxide (DMSO) and water. Notably, the incorporation of DMSO/H 2 O binary solvent facilitates the transformation from lignin macromolecules into nanoparticles by self-assembly method, leading to the significant mechanical reinforcement of the obtained polyvinyl alcohol-lignin nanoparticle (PVA-LN) organogel. Meanwhile, the formation of a large amount of hydrogen bonds between DMSO and water molecules prevented the generation of ice crystals, and the water evaporation was hindered simultaneously. Thus, the PVA-LN organogel exhibited incredible freezing tolerance (-80 °C) and remarkable long-lasting moisture (88% weight retention after 7 days), remaining stable mechanical flexibility and electrical conductivity in a wide temperature range. In addition, profited from the high strain sensitivity, fast response time, and excellent stability, the PVA-LN organogels were applicable to be assembled into flexible strain sensors to detect large human motions and subtle physiological signals even at extreme environments. It is envisioned that this work opens up a new prospect for the design of the stretchable biomass-based hydrogels with strain-sensitive properties for potential applications in flexible wearable electronics and healthcare monitoring in a broad temperature range. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) has a wide application in the chemical, electronic and textile industries due to its high ductility, toughness, and good thermal stability. However, the generation of strong and multifunctional PU film is challenging. Herein, lignin nanoparticle (LNP), which was produced from black liquor (i.e. , a waste stream from the wheat straw pulping process) using biomass based γ- valerolactone via nanoprecipitation, was used as a nano-filler for enhancing the strength of the PU film. The well distributed LNP had nano-sized particles and abundant phenolic hydroxyl groups, which could act as lubricating agents when incorporated into the PU matrix, thus leading to energy dissipation. By developing additional hydrogen bonds, LNP enhanced the tensile strength and elongation of the PU film. The maximum tensile strength and elongation at break of 50.7 MPa and 755.8% were achieved, while pure PU film had 18.4 MPa and 223.2% tensile strength and elongation, respectively. In addition, the natural inherent properties of lignin endowed the PU film with multifunctional properties, such as hydrophobicity, anti-ultraviolet, and better hydrothermal stability. Based on these interesting results, the LNP incorporation into the PU film could further broaden the practical utilization of the PU film. [Display omitted] • Biomass based solvent was used to produce well distributed lignin nanoparticle. • High strength film was fabricated through a facile blending and casting process. • Natural inherent properties of lignin endowed film with multifunctional properties. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles (LNP) were obtained by an acidolysis process from corn pristine lignin. X-ray photoelectron spectroscopy (XPS) and radical scavenging activity (RSA) of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) confirmed a significant enhancement in reactivity of LNP in comparison with pristine lignin. Polyurethane (PU) nanocomposites were prepared by pre-polymerization of polyethylene glycol and diisocyanates in the presence of different contents (1, 3, 5 and 7 wt%) of LNP. The effects of LNP, serving as both biobased polyol and crosslinker, on the mechanical, hydrophobicity and dielectric behavior of the resulted PU nanocomposites were investigated. Tensile test results showed an overall enhancement for mechanical performance, and the elongation at break exceeded 1000% for all studied PU nanocomposites. Meanwhile, dynamic mechanical analysis (DMA) revealed that the crosslinking densities gradually increased with LNP addition. Furthermore, LNP based PU nanocomposites showed inherent resistance towards ultraviolet radiation and frequency dependent behavior for electrical conductivity. On the other hand, LNP based PU nanocomposites revealed good thermal reprocessability due to the transcarbamoylation reaction in the presence of DBTDL catalyst. Unlabelled Image • Lignin nanoparticles were obtained by a facile acidolysis process from corn lignin. • LNP served as both biobased polyol and crosslinker in polyurethane nanocomposites. • The thermal decomposition temperature of the PU nanocomposites was enhanced. • PU-LNP nanocomposites have inherent resistance towards ultraviolet radiation. • PU-LNP nanocomposites show a frequency dependent behavior for electrical conductivity. [ABSTRACT FROM AUTHOR]

Lignin is the richest source of renewable aromatics and has immense potential for replacing synthetic chemicals. The limited functionality of lignin is, however, challenging for its potential use, which motivates research for creating advanced functional lignin-derived materials. Here, we present an aqueous-based acid precipitation method for preparing functional lignin nanoparticles (LNPs) from carboxymethylated or carboxypentylated lignin. We observe that the longer grafted side chains of carboxypentylated lignin allow for the formation of larger LNPs. The functional nanoparticles have high tolerance against salt and aging time and well-controlled size distribution with R h ≤ 60 nm over a pH range of 5-11. We further investigate the layer-by-layer (LbL) assembly of the LNPs and poly(allylamine hydrochloride) (PAH) using a stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). Results demonstrate that LNPs made of carboxypentylated lignin (i.e., PLNPs with the adsorbed mass of 3.02 mg/m 2 ) form a more packed and thicker adlayer onto the PAH surface compared to those made of carboxymethylated lignin (i.e., CLNPs with the adsorbed mass of 2.51 mg/m 2 ). The theoretical flux, J , and initial rate of adsorption, (dΓ/d t ) 0 , analyses confirm that 22% of PLNPs and 20% of CLNPs arriving at the PAH surface are adsorbed. The present study provides a feasible platform for engineering LNPs with a tunable size and adsorption behavior, which can be adapted in bionanomaterial production.

• Pure lignin (ca. 98 % pure) is isolated from elephant grass leaves. • Elephant grass lignin has high concentration of phenolic groups (3.85 mmol g−1). • Stable (pH 5–11 and ionic strength below 0.01) lignin nanoparticles are assembled. • Lignin nanoparticles show high antioxidant activity as compared to other lignins. • Tinted sunscreen lotions are obtained with lignin nanoparticles. Finding renewable and green resources for nanomaterial preparation is a compelling topic concerning the sustainability in nanotechnological applications. In particular, lignin-based nanoparticles are pivotal for unlocking the use of lignin in value added products. In this paper, we isolated pure lignin (ca. 98 % of purity) from elephant grass (Pennisetum purpureum) using two simple extractions with diluted acid and alkali solutions and prepared lignin and lignin acetate nanoparticles dispersed in water-basis by anti-solvent addition. Elephant grass in natura contains ca. 25 % of lignin, which could be converted into lignin nanoparticles with a 37 % yield. Spherical lignin and lignin acetate nanoparticles were revealed by electron microscopies (TEM and FESEM) and proved to be stable in a wide pH range (5–11) and ionic strength lower than 0.01. Lignin nanoparticles showed higher antioxidant activity (RSI of ca. 82) as compared to lignin in solution and to the commercial antioxidants (BHT and BHA). These nanoparticles were successfully incorporated in a neutral cream, resulting in a tinted sunscreen formulation with both ultraviolet and visible absorption. Altogether, we present here an effective method to isolate pure lignin from a non-food biomass and to prepare stable and highly antioxidant lignin nanoparticles that can be applied in dermocosmetics and are intrinsically non-toxic to the environment. [ABSTRACT FROM AUTHOR]