Assembly And Application Of Two-dimensional Noble Metal Organic Supramolecular Materials

In recent years,two-dimensional(2D)supramolecular materials have been a research hotspot.Among them,noble metal organic 2D materials have shown great application potential in the fields of catalysis,optics,and electrochemistry.This work introduces the noble metals(Pd,Pt,Au,Ag,and Ir)into 2D films,focuses on the assembly mechanism of metal organic 2D materials.This thesis also focuses on the structure and characteristics of the designed materials and develops their applications in catalysis and liquid phase molecular detection.This study is part of the collaboration between Tianjin University and the Johns Hopkins University on the preparation and catalytic application of metal-peptide assembies.The studies in Chapters 2 and 3 were performed in Tianjin University.The studies in Chapter 4 were conducted in the Johns Hopkins University.In Chapter ?,Pd/Pt/Au@KLVFF nanofilms were synthesized by glow-discharge electron-induced assembly method(also known as room-temperature electron-induced assembly).This method treats an aqueous solution of peptides containing Pd²⁺,Pt⁴⁺or Au³⁺.After electron induction,the reduction of metal ions and the peptide assembly can be synchronously completed.The peptide sequence is KLVFF.This process is fast and no need of H₂ or chemical reducing agents.It is a green and environmentally friendly ultra-fast assembly technology.This work combines experimental characterization and density functional theory(DFT)calculations to systematically study the assembly mechanism.Studies shows that during the assembly process,the C-H bonds of peptides at the benzene ring and tertiary carbon position are partially oxidized to C-OH bonds.The C-OH formed by the electron-induced effect provides additional intermolecular hydrogen bonds promote the ultra-fast peptide assembly to form a random and disordered Dish-shaped peptide building block.Further studies prove that the?-?stacking effect of benzene rings promotes the stacking of dish-shaped building blocks at the gas-liquid interface to form 2D structure.During the mechanism study,it was found that Pd/Pt/Au@KLVFF nanofilms had the property of releasing noble metal nanoparticles:Pd,Pt,Au nanoparticles released rapidly under Na BH₄ stimulation can efficiently catalyze the reduction of 4-nitrophenol.Chapter 3 is based on Chapter 2 and expands the material synthesis and application range.In this work,Ag-PVP films were prepared using polyvinylpyrrolidone(PVP)instead of peptides.This work expands the types of organic skeletons,reduces the cost of synthesis,and increases the film size from the micron level of the peptide film to the centimeter level of the macroscopic polymer film.The Ag-PVP film synthesized by the electron induced assembly method can cover the solution surface completely.By studying the distribution and optical properties of silver particles in Ag-PVP film,it is proved that the distance of silver particles can be adjusted spontaneously according to the size of the probe molecule.Application research proves that the Ag-PVP films floating on the liquid surface has excellent surface Raman enhanced scattering(SERS)effect,and can significantly enhance liquid-phase Raman signals of 4-aminothiophenol(4-ATP),riboflavin,4-mercaptobenzoic acid(4-MBA),4-mercaptophenol(4-MPh)and 4-aminobenzoic acid(4-ABA).This work expands the preparation method of SERS substrates and provides a new method for liquid phase molecular detection.Iridium-containing(Ir)organic compounds are important homogeneous catalysts,but some iridium-containing compounds have instability problems in the reaction.For this reason,a homogeneous catalyst Cp^*Ir(ppy)Cl containing iridium(Ir)is chemically connected to the hydrophilic end and hydrophobic ends of rationally designed peptides,respectively,and synthesize two metallized peptide amphiphile(MPA).After self-assembly,two-dimensional nano-ribbons and one-dimensional nano-fibers were formed,respectively.Ir active centers were distributed on the surface of the nano-ribbons and the core of the nano-fibers.We used the obtained supramolecular materials for water oxidation,focusing on the influence of supramolecular structure on the catalytic stability of water oxidation.Studies have shown that fixing Cp^*Ir(ppy)Cl on the surface of the supramolecular structure helps to slow down the agglomeration of the Ir-OO-Ce intermediate species,thereby effectively improving the catalytic stability;Wrapping Cp^*Ir(ppy)Cl inside the peptide fibers will cause a decrease in catalytic activity and stability.The metal peptide assembly expected to provide a new research idea for heterogeneous catalyst heterogeneity.