Green Fabrication Approaches of Lignin Nanoparticles from Different Technical Lignins: A Comparison Study

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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ChemSusChem, Volume 14, issue 21
The production of lignin nanoparticles (LNPs) has emerged as a way to overcome the highly variable and complex molecular structure of lignin. It can offer morphological control of the lignin polymer, allowing the formation of stable LNP dispersions in aqueous media, while increasing the potential of lignin for high-value applications. However, the polydispersity and morphology of LNPs varies depending on the lignin grade and preparation method, and a systematic comparison using different technical lignins is lacking. In this study, it was attempted to find a green fabrication method with a distinct solvent fractionation of lignin to prepare LNPs using three different technical lignins as starting polymers: BLN birch lignin (hardwood, BB), alkali Protobind 1000 (grass, PB), and kraft LignoBoost (softwood, LB). For that, three anti-solvent precipitation approaches to prepare LNPs were systematically compared: 70 % aqueous ethanol, acetone/water (3 : 1) and NaOH as the lignin solvent, and water/aqueous HCl as the anti-solvent. Among all these methods, the acetone/water (3 : 1) approach allowed production of homogeneous and monodisperse LNPs with a negative surface charge and also spherical and smooth surfaces. Overall, the results revealed that the acetone/water (3 : 1) method was the most effective approach tested to obtain homogenous, small, and spherical LNPs from the three technical lignins. These LNPs exhibited an improved stability at different ionic strengths and a wider pH range compared to the other preparation methods, which can greatly increase their application in many fields, such as pharmaceutical and food sciences.
The authors acknowledge financial support from the European Research Council (Grant No. 863808). M.B.A. acknowledges the Academy of Finland for funding (Grant No. 330617). P.A.P. thanks the Academy of Finland for funding (Grant No. 315768). The authors thank the Electron Microscopy Unit, University of Helsinki, for providing the necessary laboratory facilities and assistance. The facilities and expertise of the HiLIFE NMR unit at the University of Helsinki, a member of Instruct-ERIC Centre Finland, FINStruct, and Biocenter Finland are gratefully acknowledged. We acknowledge the provision of facilities and technical support by Aalto University at OtaNano – Nanomicroscopy Center (Aalto-NMC). We also thank Troy Faithfull (University of Helsinki) for revising the manuscript.
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Figueiredo , P , Lahtinen , M , Agustin , M B , Morais de Carvalho , D , Hirvonen , S-P , Penttilä , P & Mikkonen , K S 2021 , ' Green Fabrication Approaches of Lignin Nanoparticles from Different Technical Lignins: A Comparison Study ' , ChemSusChem , vol. 14 , no. 21 , pp. 4718-4730 .