Study On The Preparation Of Hollow Porous Ago Microspheres And Its Bactericidal Performance

AgO has strong bactericidal ability,broad antibacterial spectrum,ideal band gap and high battery specific capacity.It has potential application prospects in drinking water purification,drug-resistant bacteria killing,photocatalysis and batteries,Ilowever,the current preparation of AgO is mainly rod-like,plate-like,circular and other zero-dimensional,one-dimensional or two-dimensional nanoparticles,which have problems such as small specific surface area,easy agglomeration of particles and aggregation of reaction sites,leading to the degradation of bactericidal and photocatalytic activity.It is expected to solve the above problems by making the material into hollow porous structure.Therefore,in this paper,the fumed SiO:nanospheres,which are inexpensive,stable in structure,and easy to remove by alkali soaking,are used as templates,combing with strong electrostatic adsorption and chemical oxidation to prepare hollow porous AgO microsphcrcs.The effects of pH value and concentration of silver ammonia solution,NaOH soaking time and concentration on the morphology,particle size,particle size distribution,pore structure and specific surface area of the material are studied by SEM,TEM,XRD,AgO content test,BET and other methods.The effect of the AgO content and pore structure of the hollow porous microspheres on its bactericidal activity is studied by the flask shaking method and the plate counting method.The results shows that:Using fumed SiO₂ nanospheres as a template,with the help of the strong electrostatic adsorption between[Ag（NH₃）₂]⁺ and SiO₂ nanosphercs,the surface of the SiO₂ nanospheres is covered with[Ag（NH₃）₂]⁺,and NH₃ is removed by NaCl.The next,through chemical oxidation and NaOH soaking to remove the template,the hollow porous AgO microspheres with higher specific surface area and enhanced bactericidal activity were successfully prepared.The pH value of the silver ammonia solution affects the dispersion of the fumed SiO₂ nanospheres in the silver ammonia solution and the adsorption capacity and tightness of[Ag（NH₃）₂]⁺ on SiO₂,which in turn affects the structure of the hollow porous microspheres and the AgO content.As the pH value of the silver ammonia solution increases,the size of microspheres decreases,the shell thickness decreases,the particle size distribution narrows and becomes porous gradually,and the hollow structure appears.In addition,the increase in the pH of the silver ammonia solution causes the AgO content,specific surface area,and sterilization effect of the hollow porous microspheres to increase first and then decrease.When pH value is 6,the content of AgO is the highest（79.98%）,while when pH value is 8,the highest values of specific surface area is 28.653 m2/g,the bactericidal efficacy is the strongest,and the bactericidal efficacy reached 99.729%.The concentration of silver ammonia solution mainly affects the size,pore structure and shell thickness of the hollow porous microspheres by controlling the adsorption amount of[Ag（NH₃）₂]⁺.As the concentration of silver-ammonia solution increases,the size of the hollow porous AgO microspheres becomes larger,the shell layer gradually becomes dense,and the thickness of the shell layer increases;when the concentration of silver-ammonia solution increases,the AgO content of the hollow porous microspheres first increases and then decreases and the specific surface area decreases,and reached the maximum at 0.15 mol/L,which is 29.602 m2/g,at this time the sterilization effect is the best.Soaking in NaOH can remove the SiO₂ core and obtain a hollow porous structure.The longer the soaking time,the more complete the removal of SiO₂,the looser and porous shell layer of the hollow porous microspheres,and the reduction of the thickness of the shell layer,which increases the specific surface area and AgO content of AgO microspheres,thereby increasing the sterilization activity of AgO.However,if the soaking time is too long,the hollow porous structure is easy to collapse,which reduces the specific surface area of AgO microspheres,thereby weakening the bactericidal activity;when the NaOH soaking time is 16 h,the specific surface area of the hollow porous AgO microspheres is 24.496 m2/g,the content of AgO is 71.40%,and the bactericidal rate is 99.600%.Increasing the concentration of NaOH can also loose structure,reduce the thickness of the shell layer and increase the AgO content.When the NaOH concentration is 3.0 mol/L,the hollow porous microspheres obtain the best structure and performance.At this time,the AgO content is 85.49%,the specific surface area is 38.173 m2/g,and the bactericidal rate is 99.956%.