Layered Precursors Derived Mixed Metal Oxide As Biomimetic Nanozymes And Using For Antibacterial Application

Marine biofouling is one of the most important problems needing to solve in the development and utilization of marine resources.Therefore,it is of great significance to develop highly efficient and green non-toxic antifouling materials,and it also faces great challenges.Environment-friendly nanomaterials mimic enzymes(nanozymes)have great application prospects in antifouling field.In order to overcome the bottlenecks of materials in the application such as high cost,easy agglomerating deactivation,complex preparation process and harsh application environment,layered double hydroxide(LDHs)as precursor are performed to prepare mixed metal oxides(MMOs).By adjusting the composition and proportion of active transition metal in the LDHs and the baking temperature of the topotactic transition,MMOs with specific composition and structure can be prepared.A series of bifunctional MMOs with oxidase(OXD)and peroxidase(POD)like activities with different chemical composition,microstructure and surface properties were constructed.The key factors affecting the activity of ROS level were clarified.The relationship between structure of MMOs and the activity of mimic enzyme was established.The effects of ROS level mediated by different MMOs on fouling microorganisms were clarified,which provide theoretical support and guidance for the development of new,efficient and green antifouling materials.The specific research contents are as follows:1.Ni-V LDHs precursors with different[Ni²⁺]/[V³⁺]mole ratios were synthesized by urea coprecipitation.After calcination,Ni-V MMOs with different[Ni²⁺]/[V³⁺]mole ratios were obtained.The controlling mechanism of the crystal structure,morphology and specific surface area of MMOs by composition ratio and calcination temperature of the precursor was studied systematically.Ni-V MMOs calcined at 400 ? had large specific surface area and ultrathin nano sheet structure.Ni₃V₂O₈nanoparticles with particle size of sub-5 nm were well dispersed on the Ni O nanosheet matrix.For the first time,it was found that Ni-V MMOs exhibits excellent POD mimic activity.The composition and calcination temperature of precursor can be used to regulate the POD mimic activity.The·OH radical was the intermediate in enhancing the level of ROS.2.Co₆(CO₃)₂(OH)₈·H₂O@Co₃V₂O₈nanowire precursor were synthesized by urea coprecipitation when Co was used to instead of Ni.The Co-V MMOs nanowires composed of Co₃V₂O₈uniform dispersing among Co₃O₄by calcining Co₆(CO₃)₂(OH)₈·H₂O@Co₃V₂O₈nanowires.Co-V MMO nanowires possessed intrinsic OXD and POD catalytic activity.When the[Co²⁺]/[V³⁺]molar ratio was 3and the calcination temperature was 400 ?,Co-V MMOs showed the best activity.The activity originated from their ability to catalyze the generation of·O₂^-,which hydrolyze to·HO₂.Utilizing this unique bifunctional activity,Co-V MMOs exhibited a good antibacterial effect combining with a low level of H₂O₂(50?M).3.The single phase of Co-V LDHs were first prepared by controlling the amount of HMT accurately and controlling the p H of the coprecipitation system.After calcination,Co-V MMOs composed of Co₃V₂O₈and Co₃O₄could be prepared.The preparation of LDHs was the key factor to obtain highly active MMOs.MMOs inherited the layer structure of LDHs,which had larger specific surface area,richer surficial active sites and more evenly distributed composite structure.These superior surface properties enhanced the OXD and POD activity of 2D ultrathin Co-V MMOs nanosheets superior than 1D Co-V MMOs nanowires.It had excellent bactericidal properties under the condition of biological safety(not more than 10?g/m L)and 1?M H₂O₂(1/50 of 1D Co-V MMOs nanowires),which showed a good application prospect in the field of antifouling.4.The single-phase ternary Co-Al-Ce LDH was synthesized using a urea hydrolysis method with the ratio of Ce less than 5%.After calcination,Co-Al-Ce MMOs composed of CeO₂compounding with Co₃O₄and Co Al₂O₄had been successfully synthesized.It's the first time found Co-Al-Ce MMOs with dual enzyme-like activities.The molar ratio of Ce and the calcination temperature were the control factors for the catalytic activity of MMOs mimetic enzyme.When the molar ratio of Ce was 2.5%and calcination temperature was 200 ?,the obtained2.5Co Al Ce-200 sample exhibited the best POD-like activity.2.5Co Al Ce-200possessed dual enzyme-like activities similar to those of OXD and POD,which can catalyze H₂O₂and O₂to generate ROS,mainly·O₂^-.Owing to the excellent antibacterial capacity of·O₂^-,Co-Al-Ce MMOs exhibited antibacterial activity even in near-neutral p H solution.This provided strong evidence that Ce-containing MMO could be utilized as the potential green marine antifouling nanozyme material.5.We had hydrothermally synthesized VS₄submicrospheres,which were discovered to act as POD catalyst to oxidize the POD substrates in the aid of H₂O₂.The preparation of MMOs by LDHs was composed of oxides.In order to expand the preparation process of composite nano enzyme by layered precursor method,VS₄submicrospheres with a particle size of 300 nm were synthesized by hydrothermal method.The·OH radical was the intermediate in POD mimic catalyzed colorimetric in the presence of H₂O₂,which had potential antifouling activity.The relationship between transition metal sulfides and oxides was established.It was hoped that a better simulated enzyme antifouling material system would be obtained by controlled sulfidation and oxidation based on layered precursors.In a word,biomimetic composite nanozyme materials with good activity of simulated enzyme catalysis and bactericidal activity were obtained by derivatization of LDHs in this paper.By controlling the calcination conditions,MMOs could inherit the special morphology of the precursor,such as having a large specific surface area,rich surface active sites and a well distributed composite structure of the active phase.LDHs derived MMOs could effectively overcome the bottleneck of agglomeration and deactivation of nanozyme.According to the adjustable characteristics of layered precursor,ROS could be adjusted by controlled sulfuration and oxidation process,which was expected to be applied in the field.