Química Moderna e Aplicações

Abstrato

Time Course Evaluation of Nanozyme-Mediated Reversible/Irreversible Oxidation Reactions over Silver Nanoparticles as Peroxidase Alternatives

Saeed Reza Hormozi Jangi

Silver nanoparticles were synthesized and then characterized by different characterization methods. The as-prepared nanozymes were found to be uniform in size and morphology with a mean size as small as 11.8 nm and high peroxidase-like activity. Considering the high intrinsic peroxidase-like activity of silver nanoparticles, the time course studies were performed toward both reversible and irreversible nanozyme-mediated oxidation reactions. 3,3’,5,5’-Tetramethylbenzidine (TMB) and 3,3’-Diaminobenzidine (DAB) were selected as model substrates to study the reversible and irreversible oxidations, in order. The results revealed that the maximal activity of the silver nanozymes was achieved within 3.0 min toward TMB oxidation while regarding DAB, the steady-state plateau was observed after a reaction time as long as 25.0 min, indicating that the active nodes of the silver nanoparticles were completely saturated by TMB molecules 6.5-fold faster than the DAB molecules. Regarding time-dependent activity measurements, the nanozyme activity reached about 32% of its maximal activity toward DAB oxidation after a long oxidation time of 300 sec while for TMB oxidation, 32% of maximal nanozyme activity was observed after 30 sec (i.e., 10.0-fold faster than that of DAB). More precisely, the magnified slope (i.e., rate of change) of the initial linear portion of the reaction time curve of TMB oxidation (slope=0.6286) shows about a 10-fold higher reaction rate than the DAB oxidation (slope=0.0636). As a consequence, the as-prepared silver nanoparticles are more efficient oxidizing catalysts for the oxidation of TMB than DAB.