Preparation Of Novel Nanozymes And Their Use In Colorimetric Analysis Of Medical And Environmental Targets

Nanozymes are a class of nanomaterials with enzymatic catalytic activity,which have drawed much attention thanks to their properties such as high stability,low cost and functional versatility.However,the common nanozymes designed so far may suffer from some disadvantages like low catalytic activity and substrate specificity,which may limit largely their wide applications in the biosensing,medical imaging,and nanocatalysis fields.To overcome these problems,herein,this thesis has innovatively developed three kinds of regulation methods for activity-improved nanozymes applied for the detections of adenosine triphosphate(ATP),H₂O₂ and Hg²⁺ions.The main contents include:(1)A aptamers(Apts)-based regulation method has been developed for Fe₃O₄ NPs nanozymes for the quantitative detection of ATP(Chapter 2).It was found that once Fe₃O₄ NPs were combined with ATP Apts,their catalytic activity could be significantly enhanced(about 5times of Fe₃O₄ nanozyme).Moreover,in the presence of ATP,the specific binding of ATP and Apts,would detach Apts from Fe₃O₄@Apts,resulting in a decrease in the catalytic activity depending on the ATP concentrations.A highly selective detection has thereby been developed for sensing ATP in the linear concentrations ranging from 0.50?M-100?M.In addition,the ATP sensor was applied to assess the ATP levels in blood,showing the potential application feasility for the detection-based diagnosis of some ATP-related diseases in clinical labortories(2)A simple and effective plasma treatment strategy has been developed to dope heteroatom N into the carbon-based nanozyme of Q-graphene(N-QG),achieving the enhanced peroxidase-like performance(Chapter 3).It was found that the catalytic activity of the obtained N-QG could be nearly 4 times higher than that of QG.This plasma treatment strategy can significantly improve the peroxidase-like activity of N-QG,whereas other types of catalytic activities of enzymes(ie,oxidase and catalase-like)might be basically unchanged.A N-QG catalysis-based colorimetric detection was futher developed for probing H₂O₂ in milk,with the limit of detection as low as about 0.75?M.More importantly,this plasma treatment-based nitrogen doping approach may promise a new route for the enhancement of the catalytic performances of various nanozymes.(3)A spherical nanocomposite nanozyme of carbon nitride/cerium dioxide(g-C₃N₄/CeO₂)have been prepared by growing CeO₂ nanocatalyst in situ on g-C₃N₄ nanosheets for the colorimetric detection of Hg²⁺(Chapter 4).It was discovered that the resulting g-C₃N₄/CeO₂nanozyme could present greatly enhanced catalytic activity,presumably due to that the synergetic introduction of g-C₃N₄might increase the electron transfer in CeO₂.Moreover,in the presence of Hg²⁺ions,the catalytic activities of g-C₃N₄/CeO₂ would be largely inhibited,leading to the decrease of catalysis rationally depending on the Hg²⁺ion concentrations.Thus,an analysis strategy was proposed for the colorimetric analysis of Hg²⁺ions separately in the complex samples of blood and wastewater,with the limit of detection(LOD)as low as 0.23 n M and 0.42 n M,respectively.In addition,this preparation approach of nanocomposite nanozymes constructed by growing nanocatalysts onto a two-dimensional substrate can be extended to the design of other kinds of catalytic-based nanozymes in various detection systems.