Detachable and hierarchical assemblies for recyclable and highly efficient oil-fouling removal

Large-scale use of detergents to remove oil-fouling in industry continuously generates tremendous amounts of wastewater and thus leads to both economic and environmental problems.To develop recyclable oil-fouling removal strategy is an appealing solution but a challenging task.Herein,a kind of dynamic imine-based surfactant has been constructed by 2-formylbenzenesulfonic acid sodium salt(FBSS)and linear amines(CnNH_(2),n=6,7,8,10,and 12).Owing to high interfacial activity and strong assembly ability,dynamic FBSS/C8NH_(2)system can remove oil-fouling on multiple substrates for at least 10 cycles,largely reducing the toxicity to ecosystem.At basic pH,the hierarchical assemblies(from vesicle to network and hollow sphere)are formed and boost surfactant molecule enrichment around oil-fouling,leading to highly efficient emulsification.When pH is changed to acidic condition,the surfactant molecules dissociate due to the breaking of imine bonds,and accordingly the emulsion is destroyed and the released oil droplets float to the top layer.After removing the oil-fouling and adjusting the solution back to basic pH,the surfactant assemblies are reconstructed and used for the next oil-fouling cleaning cycle.This study provides a recyclable,efficient and eco-friendly oil-fouling removal approach,satisfying the need of sustainable development.

The role of aromatic residues in controlling the supramolecular chirality of short amphiphilic peptides

Although the relationship between molecular and supramolecular chirality remains elusive,the existing results have demonstrated the vital role of hydrophilic motifs in controlling the supramolecular handedness of peptide nanofibrils compared with hydrophobic ones.However,unlike conventional hydrophobic residues,we speculate that aromatic hydrophobic residues are mostly likely to play a unique role in regulating the supramolecular handedness because theπ–πstacking interactions of their side chains are directional like hydrogen bonding and can direct high levels of self-assembly due to the geometric confining of aromatic rings.To confirm this hypothesis,we here design a series of amphiphilic short peptides,with their hydrophobic motifs being composed of aromatic residues.Their short lengths not only favor their structural stability,synthesis,and sequence variation but also enable us to readily link their molecular and supramolecular structures.Through the combination of experiments and theoretical simulations,we demonstrate that the peptides containing L-form aromatic residues form left-handed nanofibrils while those containing D-form aromatic residues assemble into right-handed ones,irrespective of the chirality of their C-terminal hydrophilic residue.Theoretical calculations revealed that the stacking of aromatic side chains betweenβ-strands directed the twisting direction of theβ-sheets formed,with L-and D-form phenylalanine side chains stacking in a clockwise and anti-clockwise way,and more ordered and stronger aromatic stacking for homochiral peptides facilitated the formation of nanofibrils with a marked tubular feature.This study has bridged the knowledge gap in our understanding of how aromatic residues affect the supramolecular chirality of short peptides.