Deep Eutectic Solvents Hierarchical Deconstruct Lignocellulose Into Nano Building Block

The shortage of fossil energy and increasingly serious environmental problems have always been the focus of attention of countries around the world and finding green and renewable resource alternatives can fundamentally solve these problems and achieve sustainable development of mankind.Lignocellulose is a renewable and abundant resource that can be used as a feedstock for polymer materials,fuels and other renewable chemicals,making it an ideal alternative to traditional fossil fuels and chemicals.However,the components of lignin,hemicellulose and pectin and cellulose crystallinity lead to the stubbornness of lignocellulose,so effective pretreatment methods are the key to efficiently separate the three components of cellulose,hemicellulose and lignin to realize the resource and high-value application of lignocellulose.Deep eutectic solvents(DESs)can selectively dissolve lignin,which provides a new idea for the separation of lignocellulose,especially the extraction of lignin.When the material is transformed into a nanoscale,unique properties will appear,and the nanoification of lignocellulose components has always been an important way for its high-value application.In this study,DESs were used to pretreat lignocellulosic wastes,the mechanism of efficient selective separation of lignocellulose by DESs was explored,and the mechanism of possible reactive DESs in situ extraction and amination lignin was proposed and verified.Further explore the feasibility of synthesizing nanomaterials from solid components and waste liquid after DESs pretreatment and constructing electronic devices and device functionalization.The main findings are as follows:(1)Acidic DESs showed strong delignification ability and could improve the accessibility of cellulose,while alkaline DESs maintained better cellulose components.DESs can cleave the lignin-carbohydrate linkage bond and the ether bond between the lignin molecule,enabling selective lignin extraction.In addition,reactive monoethanolaminecholine chloride DESs can selectively amination lignin in situ during the selective extraction of lignin,and when the ether bond between lignins is broken,the obtained phenolic hydroxyl group will react with monoethanolamine and then generate new ether bonds.(2)The swelling of cellulose components by DESs is conducive to the preparation of lignin-containing cellulose nanofibrils(LCNFs).The properties of derived lignin nanospheres(LNPs)depend on the chemical structure and composition of the lignin fragment.Acid-catalyzed condensation occurs in lignin extracted from acid DESs,resulting in higher thermal stability of acid DESs LNPs.In contrast,basic DESs lignin has a higher molecular weight and the prepared LNPs have a smaller particle size.The average particle size of the carbon quantum dots(CQDs)synthesized by DESs waste liquid is less than 5 nm,and there are obvious lattice fringes.The yield of CQDs synthesized from DESs waste liquid(～14%)and fluorescence quantum yield(7.9%)were the highest at lower pretreatment temperatures.(3)The temperature sensors constructed by LCNFs-100 and CQDs-100 have excellent thermal response performance(Temperature coefficient of resistance=-0.0226℃-1)and high stability and repeatability,and can also have fluorescent anti-counterfeiting functions in practical applications in intelligent packaging,which proves the feasibility of functionalized construction of electronic devices and devices based on nanomaterials prepared by DESs pretreatment system.