Construction Of AuNPs/Cyclodextrin/Oligoaniline Chiral Nanozymes And Their Catalytic Performance For Dopa

Natural enzyme is a kind of chiral catalysts with high activity and selectivity.The reaction concentration of the substrate in its hydrophobic pocket can be increased effectively and thereby accelerated the reaction rate by specific identification with the substrate.However,natural enzymes also have some inherent shortcomings,such as poor stability,high catalytic cost and difficult storage,which seriously affect their industrial applications.Therefore,the development of artificial enzymes with enzyme-like activity is particularly important.Nano-ezymes,derived from the combination of nanotechnology and biocompatibility have aroused great attention.Nanozymes not only have similar catalytic activity to natural enzyme,but also easy to prepare,economical and highly stable.Although important progress has been achieved in the study of nanozymes,their applications in the area of chiral catalysis is still in its infancy.In this thesis,we aim to design and construction of functional chiral nanozymes and investigate their catalytic performance.We choose AuNPs as the catalytic center and oligoaniline-based porous helical nanomaterials and cyclodextrin as the chiral scaffolds.By complexation of these components,a series of chiral nanozymes were obtained.Subsequently,the investigation of chiral nanozymes in catalyzing different configurations of dopamine(L/D-DOPA)was performed.Specific research work is as follows:1.The classifications of nanozymes are reviewed in this paper.Meanwhile,the construction methologies of various nanozymes are also depicted in detail.In the end,the aplications of nanozymes in the areas of sensing,chiral catalysis,environment treatment,disease therapy and bioimaging are summarized.2.Aniline was added as raw material,ammonium persulfate(APS)oxidant was then added to initiate the polymerization in the isopropyl alcohol/water solvent mixture.In this process,porous helical nanoribbons(PHNRs)were prepared by adjusting the addition amount and addition timepoint of β-CD,as well as the polymerization time.The formation mechanism was investigated by means of 1H NMR,mass spectrometry,FTIR,TEM and SEM.The results showed that β-CD was selectively combined with oligoaniline at different polymerization stages to form host-guest compounds.With the extension of polymerization time,the host-guest effect was weakened,β-CD gradually fell off to facilitate the formation of PHNRs.AuNPs@PHNRs chiral nanozyme was obtained by combining AuNPs with PHNRs through electrostatic interactions.The catalytic properties of L-DOPA and D-DOPA were studied by using this chiral nanozyme.Due to the different affinity between the chiral catalyst and the two configurations of DOPA,the catalytic performance of L-DOPA was superior to D-DOPA.3.α-CD,β-CD and γ-CD bearing chiral hydrophobic cavities were used as reductants and stabilizers,through reacting with chlorauric acid(HAuCl4),three chiral nanozymes of AuNPs@α-CD,AuNPs@β-CD and AuNPs@y-CD were prepared respectively,under mild conditions.The micromorphologies of the nano-enzymes were characterized by TEM.It was found that the particle sizes of the synthesized AuNPs in the range of 15-20 nm.Subsequently,the catalytic properties of the prepared chiral nanozymes on the two configurations of dopa at different temperatures(25℃ and 35℃)were systematically studied.The experimental results showed that AuNPs@α/β/γ-CD exhibited certain catalytic selectivity for D-DOPA.Interestingly,the catalytic selectivity showed a size effect,i.e.,AuNPs@α-CD<AuNPs@β-CD<AuNPs@γ-CD.In addition,increasing the reaction temperature could also improve the catalytic selectivity.Taken together,these results demonstrated that reaction temperature and the cavity volume of cyclodextrin have significant influence on the catalytic rate and chiral selectivity.4.AuNPs@α/β/γ-CD@PHNRs chiral nanozymes were prepared by combining the prepared PHNRs with AuNPs@α/β/γ-CD.Taking them as chiral catalysts,the catalytic rate and selectivity of three catalysts for L-DOPA and D-DOPA were investigated.The results showed that AuNPs@α/β/γ-CD@PHNRs showed a certain selectivity,but it was smaller than AuNPs@α/β/γ-CD and AuNPs@PHNRs.These results suggested that there is a competitive/subtracting relationship between the porous helical nanoribbons and cyclodextrin.The two chiral scaffolds probably provide a competitive chiral catalytic environment,therefore inhibited the improvemen catalytic selectivity.