Pd nanoparticles embedded in nanolignin (Pd@LNP) as a water dispersible catalytic nanoreactor for Cr(VI), 4-nitrophenol reduction and CC coupling reactions.

The use of water-dispersible and sustainable Pd nanocatalysts to reduce toxic heavy metal ions and catalyze important organic reactions has profound significance for the environmental remediation and the catalytic industry. In this work, a novel water-dispersible and recyclable Pd@LNPs nanoreactor composed of Pd nanoparticle cluster core and LNPs shell was developed in microwave reactor in aqueous solution. It turned out that Pd nanoparticles grew uniformly and stably inside LNPs nanosphere due to the coordinated binding and interaction between Pd and the functional groups in LNPs, which was significantly different from surface loading. The green and biodegradable LNPs nanospheres are not only used as reducing agents for Pd (II) and nanocarriers, but also act as individual nanocontainers to provide favorable sites for reactions and effectively control the entry and release of reactants and products. Furthermore, the excellent and efficient catalytic properties of Pd@LNPs were exhibited by CC coupling reactions and the reduction of Cr(VI) and 4-nitrophenol. The Pd@LNPs prepared in this study have the advantages of excellent dispersion, great recyclability, high turnover frequency and better green sustainability metrics. It will have a great significance for the development of the potential high-value of lignin and the progress in the field of bio-nanocatalysts.

Microwave-Assisted Synthesis of Pd Nanoparticles into Wood Block (Pd@wood) as Efficient Catalyst for 4-Nitrophenol and Cr(VI) Reduction.

Palladium (Pd) nanoparticle catalysis has attracted increasing attention due to its efficient catalytic activity and its wide application in environmental protection and chemical synthesis. In this work, Pd nanoparticles (about 71 nm) were synthesized in aqueous solution by microwave-assisted thermal synthesis and immobilized in beech wood blocks as Pd@wood catalysts. The wood blocks were first hydrothermally treated with 10% NaOH solution to improve the internal structure and increase their porosity, thereby providing favorable attachment sites for the formed Pd nanoparticles. The stable deposition of Pd nanoparticle clusters on the internal channels of the wood blocks can be clearly observed. In addition, the catalytic performance of the prepared Pd@wood was investigated through two model reactions: the reduction of 4-nitrophenol and Cr(VI). The Pd@wood catalyst showed 95.4 g-1 s-1 M-1 of normalized rate constant knorm and 2.03 min-1 of the TOF, respectively. Furthermore, Pd nanoparticles are integrated into the internal structure of wood blocks by microwave-assisted thermal synthesis, which is an effective method for wood functionalization. It benefits metal nanoparticle catalysis in the synthesis of fine chemicals as well as in industrial wastewater treatment.

A continuous flow mode with a scalable tubular reactor for the green preparation of stable alkali lignin nanoparticles assisted by ultrasound.

Lignin nanoparticles (LNPs) have become a hot topic recently because of their improved physicochemical properties and the excellent integration into various industrial sectors compared to lignin. However, the green large-scale production of stable LNPs severely restricts the high-value applications of LNPs. In this work, a simple and potentially scalable continuous-flow mode setup with a tubular flow reactor was designed for the green preparation of stable alkali LNPs assisted by ultrasound. When the flow rates of lignin solution and nitric acid solution were 8.00 mL/min and 2.67 mL/min respectively, and the length of the tube was 5.5 m, the average residence time of mixed solution was 62.2 s in the tubular reactor. Spheroid nanoparticles with an average size of 97.2 nm were obtained under this optimized condition. Furthermore, the results showed a better control of the mixing compared to the batch process, resulting in a homogeneous distribution of smaller particle sizes thus improving stability and UV-blocking properties. This is attributed to the better mixing and excellent mass transfer characteristics in the tube, which provides favorable conditions for the full contact and uniform dispersion of the mixed solution. More importantly, continuous flow mode makes it possible to prepare LNPs with excellent physicochemical properties on a large scale, which will bring great opportunities for the industrial production and application of LNPs.

The preparation of stable spherical alkali lignin nanoparticles with great thermal stability and no cytotoxicity.

In order to further develop the potential applications of lignin biomass, the research on lignin nanoparticles (LNPs) and their nanocomposites has attracted increasing attention. In this study, a facile and no chemical modification approach to prepare stable alkali lignin nanospheres is presented. The nanospheres around 85-125 nm were prepared through the π-π interactions between molecules in the self-assembly process. Lignin alkali was dissolved in ethylene glycol at different initial concentrations and subsequently ultrasound and dialysis treatment were conducted to prepare LNPs. The prepared LNPs had zeta potentials between -20 mV and -40 mV, and they were electrostatically stable over the pH range of 3 to 12 in aqueous solution. The chemical structure of LNPs was not significantly modified compared to lignin. Meanwhile the increased content of carboxyl and aliphatic hydroxyl groups in the LNPs structure was observed. Furthermore, the thermal stability and solubility in organic solvents (ethanol, acetone and THF) of LNPs were enhanced compared to those of lignin. In vitro cell viability evaluation indicated that the prepared LNPs had no cytotoxicity and excellent biocompatibility with mouse fibroblast. Therefore, we proposed here the production of high-quality and renewable LNPs, which will provide a novel perspective for multifunctional applications of bio-based nanomaterials.

Lignin Nanoparticles and Their Nanocomposites.

Lignin nanomaterials have emerged as a promising alternative to fossil-based chemicals and products for some potential added-value applications, which benefits from their structural diversity and biodegradability. This review elucidates a perspective in recent research on nanolignins and their nanocomposites. It summarizes the different nanolignin preparation methods, emphasizing anti-solvent precipitation, self-assembly and interfacial crosslinking. Also described are the preparation of various nanocomposites by the chemical modification of nanolignin and compounds with inorganic materials or polymers. Additionally, advances in numerous potential high-value applications, such as use in food packaging, biomedical, chemical engineering and biorefineries, are described.

Delaying Anticancer Drug Delivery by Self-Assembly and Branching Effects of Minimalist Dendron-Drug Conjugates.

Self-assembly of a covalently-bound lipophilic drug to a dendronic scaffold for making organic nanoparticles is reported as a proof of concept in nanovectorization. A minimalist structural approach with a small PEG-dendron conjugated to paclitaxel (PTX), incorporating safe succinic and gallic acids, is efficient to provide the expected anticancer bioactivity, but also significantly retards and targets intracellular delivery of PTX in 2D and 3D lung cancer cell cultures. A branching effect of dendrons is crucial, when compared to linear PTX conjugates. Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) studies indicate the formation of stable, low-disperse nanoparticles at 10-5 m in H2 0, which could also be responsible for the biological effects. An ultrasensitive LC-MS/MS method was used for the determination of intracellular PTX concentration over time, along with the survival rates of cancer cells. Similarly, cell survival assays were successfully correlated to a 3D cell culture with spheroids for mimicking tumors, when treated with PTX conjugates. Our work opens the way to a full evaluation program required for new chemical entities.

Organocatalyzed cyclopropanation of alpha-substituted alpha,beta-unsaturated aldehydes: enantioselective synthesis of cyclopropanes bearing a chiral quaternary center.

An enantioselective cyclopropanation of alpha-substituted alpha,beta-unsaturated aldehydes with bromomalonate has been successfully developed through a domino Michael/alpha-alkylation strategy. The method allows the efficient formation of cyclopropanes bearing a quaternary carbon stereocenter at the alpha-position of the aldehydes by using iminium/enamine catalysis and gives a nice extension on the organocatalytic cyclopropanation of bromomalonate and alpha,beta-unsaturated aldehydes previously reported by other groups. Very good yields (up to 81%) and enantioselectivities (up to 97% ee) have been obtained. The optically active cyclopropane derivatives are of high synthetic interest as useful targets for further elaboration into more complex structures.

General access to aminobenzyl-o-carboranes as a new class of carborane derivatives: entry to enantiopure carborane-amine combinations.

The convenient synthesis of original aminobenzyl-o-carboranes, which represent a new class of nitrogenated carborane derivatives, is described. These novel compounds have been efficiently prepared starting from commercially available aromatic aldehydes and monosubstituted o-carboranes via carboranyl alcohols and chlorides as intermediates. The key step of this methodology is a selective nucleophilic amination under mild conditions that allows the formation of the expected amines while limiting the partial deboronation of the carborane cluster. This general strategy has been applied to the preparation of a wide variety of aminobenzyl-o-carboranes. The extension of this pathway to the synthesis of enantiopure carborane-amine combinations is also described.

Cooperative effect of carborane and pyridine in the reaction of carboranyl alcohols with thionyl chloride: halogenation versus oxidation.

Thionyl chloride (SOCl2) acts as halogenation reagent in its reaction with 1-[phenyl(hydroxy)methyl]-2-R-1,2-dicarba-closo-dodecaborane 1a, b but unexpectedly behaves as an oxidant for 1-[2'-pyridyl(hydroxy)methyl]-2-R-1,2-dicarba-closo-dodecaboranes 2a, b. The synthesis and characterization of all new compounds, including structure determinations of 1a, 2a, 1-[phenyl(chloro)methyl]-2-methyl-1,2-dicarba-closo-dodecaborane 3a, and 1-[2'-pyridyl(oxo)methyl]-2-methyl-1,2-dicarba-closo-dodecaboranes 4a are reported and the possible pathways are discussed.