Peroxidase-like Activity Of Carboxymethyl Chitosan Modified Palladium Nanoparticles

Objective: To study the peroxidase-like activity and application of carboxymethyl chitosan（CMCTS）modified palladium nanoparticles（PdNPs）.Methods: CMCTS-PdNPs were synthesized by one-step sodium borohydride reduction of potassium chloropalladate in the presence of carboxymethyl chitosan as a protective agent.The as-prepared CMCTS-PdNPs were used to catalyze the oxidation of a peroxidase substrate 3,3’,5,5’-tetramethylbenzidine（TMB）by H₂O₂ to form the oxidized colored product,which can be measured at 652 nm by spectrophotometry.Iodide ion was determined based on the inhibition effect of iodide on the catalytic activity of CMCTS-PdNPs.Results: From the experimental results,we found that CMCTS-PdNPs possess peroxidase-like activity,which can catalyze the oxidation of TMB to the oxidized colored product by H₂O₂.Based on the peroxidase-like activity,analytical methods for hydrogen peroxide and iodide determination were established.The linear equation was A=-0.015+0.145C（r=0.9991）for hydrogen peroxide assay.The limit of detection（LOD）was found to be 0.15 mM.As for iodide ion,the linear equation was A=1.06-0.0764C（r=0.995）.The limit of detection was 0.19 nM.In the real life,the chromogenic system of CMCTS-PdNPs catalyze the oxidation of the peroxidase substrate TMB by H₂O₂ could be used to detect the iodide ion in tap water and kelp.The recovery of standard addition were 95.53%-102.8% and 96.14%-97.43% respectively.The CMCTS-PdNPs was turned out to be more stable than bare PdNPs,and had higher catalytic activity than bare PdNPs and citrate-PdNPs.Conclusion: In this study,we found that the carboxymethyl chitosan can not only stabilize Pd nanoparticles,but also maintain the peroxidase-like activity of Pd nanoparticles.The peroxidase-like activity of CMCTS-PdNPs can be successfully applied for the determination of hydrogen peroxide and iodine ion.