Study On The Construction And Properties Of Core-Shell Materials Based On Phenolic Hydroxyl Polymers

Nanomaterials have important prospects in the field of materials science due to their excellent optical,electrical,magnetic and catalytic activity qualities.The design of nanomaterials into specific structures and ideal surface states allows for the targeted functionalisation of nanomaterials.Noble metal nanoparticles with large specific surface area and high activity are widely used in catalysis of organic pollutants,so addressing the easy aggregation and instability of noble metal nanoparticles at the nano level becomes the key to improving catalytic efficiency.In this thesis,nanomaterials with uniform distribution and regular morphology were constructed based on phenolic compounds with nano-Fe₃O₄ as the core material,followed by the loading of silver nanoparticles on the core-shell material.The addition of polymer layers could effectively improve the stability and recyclability of the catalytic materials.And their catalytic ability for different organic pollutants was initially explored.The main studies are as follows.（1）Based on polydopamine（PDA）,this work has successfully prepared core-shell structured nanomaterials（Fe₃O₄@PDA）loaded with Ag nanoparticles by a simple and green synthetic method.The ability of the PDA layer to reduce Ag in situ was exploited without the addition of a reducing agent,enabling the direct reduction and growth deposition of well-dispersed Ag nanoparticles on the polydopamine（PDA）layer.The Fe₃O₄@PDA@Ag nanomaterials showed good catalytic activity and recyclability towards 4-nitrophenol with a rate constant k of 1.03 min^-1.this simple and green synthesis method will also provide a platform for other catalytic applications.（2）Based on catechol-formaldehyde resin（CFR）,this work has prepared Fe₃O₄@catechol-formaldehyde core-shell structured nanospheres（Fe₃O₄@CFR）using a hydrothermal method under alkaline conditions.By varying the amount of catechol and formaldehyde,temperature and ammonia concentration,a series of Fe₃O₄@CFR core-shell structured nanomaterials were prepared.The results showed that the Fe₃O₄@CFR spherical diameter could be controlled between 320 to 935 nm by varying the reaction conditions.In addition,the core-shell structured Fe₃O₄@catechol-formaldehyde resin@Ag nanoparticles（denoted as Fe₃O₄@CFR@Ag）were obtained using the reduction of Ag NO₃ using Fe₃O₄@CFR without the addition of an external reducing agent.The presence of the CFR shell ensured that the silver nanoparticles were distributed like satellites on the CFR shell layer.Fe₃O₄@CFR@Ag showed good catalytic activity towards organic dyes.Further studies concluded that the catalytic activity of Fe₃O₄@CFR@Ag was higher for the cationic dye methylene blue（MB）than for the anionic dye methyl orange（MO）due to the presence of electrostatic interactions,indicating that Fe₃O₄@CFR@Ag is more selective for cationic dyes than for anionic dyes,which enlightens us that we can achieve efficient catalysis of a class of catalytic materials by changing the surface properties of the material.This shows that Fe₃O₄@CFR@Ag is more selective for cationic dyes than anionic dyes.（3）Based on pyrogenic gallic acid-formaldehyde resin（PGNR）,this work used a facile method to synthesize iron tetroxide@pyrogenic gallic acid-formaldehyde resin@silver nanoparticles Fe₃O₄@PGNR@Ag)core-shell structured nanomaterials.We used cetyltrimethylammonium bromide（CTAB）to perform a simple charge switch on the Fe₃O₄@PGNR@Ag material to achieve a successful conversion of the negatively charged Fe₃O₄@PGNR@Ag surface to the positively charged Fe₃O₄@PGNR@Ag-CTAB,realising its efficient catalysis of the anionic dye MO.In the catalysis for the cationic dye rhodamine B（Rh B）,it was verified that the unmodified Fe₃O₄@PGNR@Ag was better and more selective for Rh B.Similarly,for the electrically neutral tetracycline,Fe₃O₄@PGNR@Ag and Fe₃O₄@PGNR@Ag-CTAB did not show a significant difference in the catalytic rate.This chapter confirmed that electrostatic interactions had an influence on the conduct of catalytic reactions and that changing the surface properties of materials can be a simple way to improve the selectivity of catalytic materials.