Preparation And Properties Of Graphene-loaded Silver-based Nanoparticle Composites

Silver nanoparticles?AgNPs?are widely used as antibacterial materials in daily life,such as eye drops,food preservation,cosmetics,disinfectants and water treatment,because of their excellent antibacterial properties,broad spectrum and high safety o f antibiotics and play a huge role in the protection of human health.However,due to the high activity and poor stability of AgNPs,it is easy to cause rapid loss of Ag,which not only reduces the antimicrobial properties of AgNPs,increases the cost of antimicrobial,but also may cause heavy metal pollution.In order to solve these problems and improve the antibacterial properties,the Ag-based nanoparticles were uniformly dispersed by using the graphene oxide?GO?with high specific surface area as templated.The iron element?Fe?was introduced to prepare a composite material with magnetic properties,to facilitate the reuse of antimicrobial materials.Herein,composites of reduced graphene oxide?rGO?supported AgFe or Ag/Fe₃O₄ nanoparticles have been designed and prepared.The effects of preparation conditions on the composition and microstructure of the composites were studied in detail.The relationships between the microstructure and antibacterial,bactericidal,biocompatibility of the composites we re studied in detail.Biocompatible and separable antimicrobial materials were successfully prepared and their controllable synthetic process parameters were also obtained.The main research contents are as follows:1.AgFe/r GO composites were prepared by in situ growth with one-step reaction by using GO as template,AgNO₃ and Fe?NO₃?₃·9H₂O as metal precursors and NaBH₄ as reducing agent.Escherichia coli?E.coli?and Staphylococcus aureus?S.aureus?were used to detect the antibacterial properties.The results showed that the pH values and the ratios of the metal precursor were important factors to controll the microstructure of the composites.The nanoparticles with AgFe alloy structure were prepared at pH of 9.5 and a molar ratio of Ag⁺ to Fe³⁺ of 1: 1.Nanoparticles with the average particle size was 5 nm were uniformly decorated on the r GO sheets.The composite materials had excellent antibacterial properties toward E.coli and S.aureus,the Minimum inhibitory concentration?MIC?was 80 mg/L and 120 mg/L,the Minimum bactericidal concentration?MBC?was 50 mg/L and 100 mg/L,respectively.In addition,the composite had a good biosecurity when it's concentration below 50 mg/L.2.Ag/Fe₃O₄/rGOcomposites were prepared by two-step experiment by using GO,AgNO₃ and FeCl₂·4H₂O as raw materials,NaBH₄ as reducing agent.Firstly,Fe₃O₄/rGO was prepared,and then Ag was further introduced to obtain Ag/Fe₃O₄/rGO composites.The results showed that the metal precursor ratio was an important factor to control the microstructure of the composites.When the molar ratio of Ag⁺ to Fe²⁺was 1: 2,Fe₃O₄ and Ag nanoparticles with average diameters of 10 and 20 nm,respectively,were uniformly loaded on the rGO.The saturation magnetic susceptibility of the composites was 24.7Am²/kg,which can be attracted by magnets.The MIC of E.coli and S.aureus was 50 mg/L and 80 mg/L,the MBC was 30 mg/L and 50 mg/L,respectively.At the same time,the composite material had a good biosecurity.3.AgFe/graphene cellular monolith?AgFe/GCM?composites were prepared by chemical reduction-gel reaction.The AgNO₃,Fe?NO₃?₃·9H₂O solution was mixed with GO suspension,and then treated with NaBH₄ and ascorbic acid.The material was assembled into gel at 90? for 4 h,and freeze-dried to obtain AgFe/GCM composites.The results showed that the molar ratio of Ag⁺ and Fe³⁺ in the reaction precursors had an important effect on the morphology and loading proportion of the composites.When the ratio was 1: 1,the pore structure of the composites was obvious and the AgFe nanoparticles were loaded uniformly.The MIC values of the composites against E.coli and S.aureus was 50 mg/L and 100 mg/L,the MBC values was 30 mg/L and 50mg/L,respectively.In the dynamic sterilization device,after filtering for 5 times,70% of the bacteria in the solution were killed,suggesting the potential applications of the obtained materials in water filtration sterilization.Furthermore,the release rate of Ag⁺ decreases due to the presence of Fe.When the concentration of the composite was 50 mg/L,the cell survival rate was 85%,showing excellent biosecurity.