Construction Of Phenylalanine-based Chiral Self-assembly Aggregates And Their Application In Regulating Synthesis Of Chiral Metal Oxide Electrode Materials

Chiral self-assembles can form unique chiral structures such as nanotubes,spirals,twists and nanofibers by adjusting their functional group structure or weak intermolecular interaction.Chiral self-assembles have various structures,high mechanical rigidity and thermal stability,which have great potential in fields of nanobiology,biomimetic biomineralization and molecular recognition sensor.Therefore,the development of chiral self-assembles and researching the mechanism of chiral self-assembly has attracted extensive attention.To the best of knowledge,the construction of chiral self-assembly can be achieved by chiral amphiphilic molecules through self-assembly.Therefore,the design and synthesis of chiral amphiphilic molecular is very important for the development of new chiral self-assembly bodies.Due to its environmental friendliness,biological compatibility,adjustable structure and one or more chiral centers,chiral amino acid surfactants are expected to be widely used in life science,material preparation,food emulsification,daily fine chemicals and other fields.In recent years,amino acid molecules with abundant structure and chiral characteristics,have attracted a great deal of attention.The introduction of amino acid into specific amphiphilic molecules could construct molecular self-assembles with different structures.Studies have shown that covalent or non-covalent interactions between different molecules,such as complexation,hydrogen bonding,electrostatic interaction,hydrophobic interaction,π-stacking and chiral recognition,have different contributions to the construction of aggregates.However,the intermolecular interaction can contribute to the construction of chiral self-assembly by varying physical and chemical conditions(such as temperature,pH,ionic strength,etc,),as well as the regulation of various molecular structures.However,the formation and transformation of different ordered structures are not systematic and perfect.In addition,the carbon atoms connecting the amino and carboxyl ends in the surfactants of amino acids are asymmetric carbon atoms.Therefore,the construction of new chiral self-assemblies based on the chirality can provide new approaches for the separation and recognition of chiral drugs,the preparation of chiral materials and functional applications.In this paper,chiral phenylalanine surfactants with long chains of benzene ring are designed and synthesized,and the association characteristics,gelation behavior,and the structure and transformation of complex self-assembly bodies induced by supramolecular compounds calixarene in aqueous solution has been investigated.The relationship between the self-assembly structure and chiral signal has been discussed.Chiral amino acid surfactant self-assembles have been used for regulating the synthesis of different chiral structure of metal oxide electrode materials,and found that it can greatly enhance the electrocatalytic property The research contents had been clarified into five parts as follows1.The synthesis and self-assembling behavior of chiral phenylalanine-derived surfactantThe amino acid derived surfactant(N-(2-hydroxylalkyl)-L-phenylalanine)has been prepared via ring-opening reaction of alkylene oxide and connecting to N-terminate of phenylalanine.The self-assembling behaviors of C12-Phe can be controlled by varying concentration,alkyl chain length and temperature of C12-Phe solution.C12-Phe assemblies are investigated by surface tension,UV spectrum,circular dichroism spectrum,nuclear magnetic resonance,dynamic light scattering,transmission electron microscopy and molecular dynamics simulations.From the remarkable difference between the structures and morphology of the self-assembling materials based on C12-Phe and C12-Ala,it could be concluded that the self-assembly behaviors were dramatically altered by the phenyl group.The presence of a center π-π stacking between two C12-Phe strands was demonstrated to be an important factor in promoting the twisted nanofiber morphology and a stronger network.With the increase of alkyl chain length,the self-assemblies was improved and the as-prepared self-aggregates transformed from fiber/fiber rods to wound multiple fibers with dendritic structures.When the temperature of aquoues solution of chiral phenylalanine-derived surfactant is increased,the intermolecular hydrogen bond is broken,and the morphology of the self-assembled body changes from spiral winding to rod-like structure and then forms fiber structure.The chiral signal of N-(2-hydroxyalkyl)-L-phenylalanine aggregates was enhanced with the increase of the solution concentration.The above results will provide an important theoretical basis for the fabrication of new chiral self-assembly and its regulation mechanism,especially for the amplification if chiral signals.demonstrated C12-Phe self-assemblies have great potential in a variety of biomedical applications.2.Construction of N-(2-hydroxylalkyl)-L-phenylalanine chiral hydrogelThe pH-responsive hydrogel based on N-(2-hydroxylalkyl)-L-phenylalanine surfactant has been prepared and investigated its gelation behavior by varying chain length and concentration,which demonstrates the phase inversion temperature.Various characterizations have been carried out to analyze morphologies and rheological property of N-(2-hydroxylalkyl)-L-Phenylalanine hydrogels.Circular dichroism(CD)was used to study the chirality of hydrogels at different concentrations and with different chain lengths Small-angle X-ray scattering(SAXS)was used to study the characteristics of hydrogels structure with the change of concentration.TEM was used for observing the morphology of hydrogels formed by self-aggregation with different chain lengths and concentrations.The research results demonstrate that phenylalanine-derived surfactant only can form chiral hydrogel in aqueous buffer at pH ranging from 12.5 to 13.The effect of hydrocarbon chain length on the gelation efficiency was investigated.The increase of the chain length of the hydrocarbon tail enhances the ability to gelate buffered water.The effect of concentrations on the gelation was investigated.With the increase of N-(2-hydroxylalkyl)-L-phenylalanine concentration and chain length of the hydrocarbon tail,the aggregation would be closely arranged and have weaker chirality,leading to the weakening of coupling between carbonyl group and benzene ring chromophiles.The research results indicated that the chirality of substances would not always show the role of chiral amplification,and it could decrease under certain conditions.However,the increase of chain length and concentration would increase the viscoelasticity and the phase transition temperature of the hydrogels,and significantly decrease the chiral signal with the increase of chain length.The chiral gel is mainly formed through the intermolecular hydrogen bond between OH and NH groups on adjacent molecular chains and the chral recognition of chiral center.3.Fabrication of N-(2-hydroxylalkyl)-L-phenylalanine induced calix[4]arene in a novel composite chiral self-assemblyA new chiral complex aggregation of calix[4]aromatic carboxylic acid derived supramolecular compound with N-(2-hydroxylalkyl)-L-phenylalanine was investigated in aqueous solution.The surface tension of calix[4]aromatic/phenylalanine surfactant composite system was measured by surface tensiometer.The hydrodynamic radius was measured by dynamic light scattering method.The chemical shift of NMR hydrogen spectrum was used to make the Job curve and fit the binding ratio.Ultraviolet spectrophotometry,circular dichroism and negative staining transmission electron microscopy(TEM)were used to characterize the self-assembly of phenylalanine-derived surfactant induced amphiphiliccalix[4]aromatic carboxylic acid derivatives.It was found that at a fixed concentration of 0.1 mmol/L calix[4]arene,when the composite ratio of the two substances was less than or equal to 2:1,they formed the special morphology of pellet envelops.While more than 2:1,they formed the special morphology of tropical berries.It could be ascribed to three aspects,which are hydrophobic interaction of the alkyl chain of chiral phenylalanine surfactant and cavity of calixarene,π-π conjugates formed by two chiral phenylalanine benzene rings in the head of the surfactant with benzene of ocalix[4]arene,as well as the head of the center of the chiral recognition,which makes the benzene rings and adjacent to the alkyl chain of phenylalanine insert into cavity of calixarene.As for beyond composite ratio of phenylalanine-derived surfactants,it would assembly form one-dimentional self-assembles wrapped around spherical body in the presence of intermolecular driving force.4.Synthesis of chiral cerium dioxide nanomaterials induced by N-(2-hydroxyl dodecyl)-L-phenylalanine and its electrocatalytic propertiesThe chiral cerium oxide nanoparticles(CeO2)were prepared by hydrothermal method with the assistance of a chiral amino acid-based surfactant(N-(2-hydroxylalkyl)-L-phenylalanine)as a structurc directing agent.Various characterizations have been conducted to analyze the morphologies and structure of chiral cerium oxides,such as TEM,SEM and HRTEM.The circular dichroism of cerium dioxide nanoparticles was determined,and the results show that cerium dioxide nanoparticles are assembled into asymmol structures and exhibit chiral signals.Due to the structure of chiral assembly structure of phenylalanine-derived surfactant,crystal nucleus of cerium dioxide nanoparticles show asymmol growth,which may be the origin of chirality.The resultant CeO2 can be used as modifier materials for electro-catalytic oxidation of glucose.The resultant chiral C-CeO2 could be used for detecting glucose in the range of 0.80 μmol/L-2.00 mmol/L with a detection limit of 0.40 μmol/L.The chiral C-CeO2have great potential in the field of electrochemical sensor.5.Synthesis of chiral LaSrCoO4 nanomaterialsinduced by N-(2-hydroxyl dodecyl)-L-phenylalanine and its electrocatalytic propertiesIn this chapter,chiral LaSrCoO4 with porous structure was synthesized by chiral N-(2-hydroxyalkyl)-L-phenylalanine surfactant.X-ray diffraction,scanning electron microscopy,transmission electron microscopy,high resolution transmission electron microscopy and photoelectron spectroscopy were used to determine the morphology,structure and composition of the materials.It was found that LaSrCoO4 prepared with the presence of 1.2 mmol/L amino acid surfactant as the chiral-direct agent,demonstrated small particle sizes and the high porosity.The circular dichroism spectra of chiral LaSrCoO4 were determined by circular dichroism.When the surfactant concentration is 1.2 mmol/L,the chiral signal reaches the maximum value.However,as the concentration of surfactant continues to increase,the chiral signal begins to weaken.Therefore,LaSrCoO4 can be induced chirally based on the chiral phenylalanine-derived surfactant self-assembly,which presents a unique porous structure and electrocatalytic property.This chiral induction provides a new way to design cathode materials for fabrication of intermediate temperature solid oxide fuel cells.