Preparation And Preliminary Application Of Novel Peroxidase Nanoenzymes And Photocatalytic Materials

Nanomaterials with catalytic functions have been widely studied and applied due to their advantages such as high activity,strong stability,and mild reaction conditions.In this thesis,four kinds of catalysis systems have been constructed by using different nanomaterials with peroxidase-like nanozymes and/or photocatalytic functions.Moreover,the as-prepared catalytic nanomaterials were applied separately for the colorimetric detection of dopamine?DA?,levodopa?LDA?,and heparin,the efficient production of H₂O₂ through photocatalytic water splitting,and the catalytic detoxification,detection,and adsorption-based removal of mercury in the environment wastwater.The main research contents include:?1?Mesoporous magnetic Fe₃O₄ nanoparticles?NPs?were fabricated with peroxidase-like catalysis activity towards a catalysis-enhanced colorimetric analysis method for detecting DA and LDA in urine through the specifically strong Fe-DA chelation?Chapter 2?.Mesoporous and magnetic Fe₃O₄ NPs were prepared by using the glycol solvothermal method.The experimental results indicate that the so synthesized Fe₃O₄ NPs could have certain magnetic properties and peroxidase-like activity.Importantly,the introduction of DA and its derivative LDA with biscatechol groups could greatly enhance their peroxidase activities.A colorimetric Fe₃O₄catalysis-enhanced colorimetric method was thereby established to detect DA and LDA in urine samples,with the detection limits as low as 8.0 nM and 5.0 nM,respectively.?2?A kind of metal-free polymeric nanozyme with peroxidase-like catalysis has been fabricated by using polyethyleneimine?PEI?and 3,4-dihydroxybenzaldehyde?DHB?towards a catalysis-inhibition colorimetric method for probing heparin in serum?Chapter 3?.The metal-free polymeric nanozyme of PEI-DHB NPs were prepared by the one-pot covalent coupling route at room temperature.It was found that the negatively charged heparin could tightly bind with the positively charged PEI-DHB NPs through the strong electrostatic adsorption,resulting in the inhibition of their peroxidase catalysis activities.A highly sensitive colorimetric analysis method was thus developed for the detection of heparin in human serum,with a detection limit as low as about 2.5 nM.?3?A nanophotocatalyst with tunable morphology and photocatalytic activity was developed and applied for the production of H₂O₂ by photocatalytic splitting of pure water under the visible light,showing the high H₂O₂ production efficiency?Chapter 4?.Mesoporous carbon nitride quantum dots@melamine?MA?-silver(CN_QDs@MA-Ag)nanocomposites were prepared through the supermolecular self-assembled route using different proportions of CN_QDs.Unexpectedly,it was discovered that the materials could exhibit different morphologies?such as nanowires,nanoflowers,and nanosheets?.At the same time,they could display the morphology-depending visible-light photocatalytic activity.Among them,the CN_QDs@MA-Ag ones(containing 30%CN_QDs)with pinecone-like structure showed the strongest acapability of the photocatalytic water splitting towards H₂O₂ production with the efficiency to39.82?mol·g^-1 h^-1,which is more than ten times higher than that of the ones catalyzed only by pure CN_QDs.?4?CN_QDs@MA-Ag nanocomposites were prepared by the controlled supramolecular self-assembly method with the dual catalytic functions of nanozyme catalysis and photocatalysis for the catalytic detoxification,detection and adsorption-based removal of mercury in environmental wastewater?Chapter 5?.It was found that the prepared catalytic nanomaterials could not only exhibit the peroxidase-like catalytic activity that could be specifically enhanced by adding Hg²⁺ions.A catalysis-enhanced colorimetric method was thereby established to detect Hg²⁺ions in wastewater,with the detection limit as low as about0.050 nM.At the same time,the as-fabricated nanocomposites could photocatalyze the water splitting to produce H₂O₂ for the reduction and detoxification of elemental mercury.In addition,the mesoporous CN_QDs@MA-Ag could be employed as the adsorbent to achieve the adsorption-based removal of mercury,with the removal efficiency as high as 89.5%.