| Hollow mesoporous materials are geneally applied in energy storage,wave absorption,catalysis,gas sensitivity and drug transmission due to their advantages of high specific surface area,pore capacity,low density and stable chemical properties.Among them,hollow mesoporous SiO2 spheres,as the carrier of catalyst,can not only avoid the aggregation of active substances,but also reduce the transport distance of charge carriers and promote the enrichment of pollutant molecules.However,the preparation of hollow mesoporous materials usually requires the cumbersome and time-consuming hard template method,and the catalyst is difficult to recover directly.We used hollow mesoporous SiO2 as a template to avoid the complex template removal process,and prepared different shapes of hollow mesoporous(ZnFe2O4,FeS2)/SiO2 composite.ZnFe2O4 as the active center,the catalyst can be magnetically separated from water.The S atoms in FeS2 can accelerate the charge transfer between Fe ion and H2O2,thus enhancing the catalytic activity.The main research contents are as follows:(1)Magnetic double-layer mesoporous ZnFe2O4/SiO2 hollow spheres were synthesized by one-step solvothermal which using mesoporous SiO2 hollow spheres as template.With a high specific surface area(443 m2/g),the composite exhibited selective adsorption of the methylene blue(MB),and the adsorption-desorption equilibrium was achieved in only 1 min.For 60 mg/L MB solution,approximately 50%of the MB was removed by adsorption,while the remaining 50%was degraded by photo-Fenton within 90 min.And the total organic carbon(TOC)removal rate was up to 90%.In addition,the catalyst is magnetic and can be directly separated from the pollutants for easy recycling.Moreover,after 5 cycles,the catalytic performance was unchanged,indicating that the catalyst had good reusability.In conclusion,ZnFe2O4/SiO2 composite has good adsorption property and photo-Fenton activity.(2)Based on the previous chapter,ZnFe2O4/SiO2 composite with octahedral yolk-shell structure was synthesized by changing the reactant concentration.Compared with the previous chapter,the composite can degrade 60 mg/L MB 100%within only 70 min,which reduces the reaction time.At the same time,the formation mechanism of octahedral yolk-shell ZnFe2O4/SiO2 composite was studied by microcalorimetry.First of all,Fe3+ and Zn2+ enter the cavity of SiO2 spheres through the mesoporous shell,before ?-(Fe,Zn)OOH and ?-Fe2O3 were formed in the core and on the outer surfaces of the hollow SiO2 spheres,where ?-Fe2O3 had an octahedral morphology.Finally,?-Fe2O3 was converted into octahedron-shaped ZnFe2O4 and SiO2 was simultaneously modifed into nanosheets.When the heating rate was decreased from 2.0?/min to 0.25?/min,?-(Fe,Zn)OOH and?-Fe2O3 were only synthesized after keeping at 200? for 24 h,and the as-synthesized octahedral particles did not have a yolk-shell framework structure.(3)According to the results of the previous two chapters,double FeS2/SiO2 hollow spheres were obtained by vulcanizing Fe3O4/SiO2 composite.As a Fenton catalyst,FeS2/H2O2 system not only generates·OH,but also generates·SO4-with strong oxidability in the process of catalytic oxidation of pollutants,accelerating the catalytic reaction.In order to expand the application of the catalyst,the prepared Fenton catalyst was used as peroxidase,which reacted with H2O2 to catalyze the colorless substrate 3,3',5,5'-tetramethylbenzidine(TMB)into blue oxTMB within 1 min.Based on the peroxidase-like activity of FeS2/SiO2 composite,we builded a way for the rapid detection of H2O2.The Michaelis constant(Km)of 0.0126 mM was far lower than that of FeS2(0.227 mM)and natural horseradish peroxidase(HRP,3.7 mM),indicating that as-prepared material has an outstanding affinity for H2O2.Moreover,the detection time was only 1 min,and the limit of detection(LOD)was 4.20 nM,lower than the similar peroxidase.By addition glutathione(GSH),the blue color will fade to colorless,and the change of absorbance value can be monitored by Uv-vis spectrometer.Therefore,based on the inhibitory effect of GSH on FeS2/SiO2 peroxidase-like activity,we also developed a GSH sensing system with high sensitivity and specificity,with a detection range of 1.0-40 ?M and a LOD of 0.160 ?M.Moreover,the sensing system is not affected by substances such as amino acids in serum,and has practical application potential.This research based on nanomaterial sensors provides the possibility of applications in biosensing,environmental monitoring and other fields. |
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