Single Nanoparticle Collision Electrochemistry for Dual-mode Characterization of Synthesis Process of Silver-coated Gold Core-shell Nanomaterials
The accurate characterization of the synthesis process of core-shell nanomaterials is crucial for studying their structural evolution and structure-activity relationships.In this work,a new method that combined the advantages of electrocatalytic and direct electrolytic single-nanoparticle collision for dual-mode characterization of the synthesis process of core-shell nanomaterials was developed.The method was used to accurately detect the Ag shell volume(VAg)of Au@AgNPs synthetized at different conditions on the basis of the proportional relationship between VAg and oxidation peak charge(Q).Moreover,Au@AgNPs,small-sized Au seeds and generated Ag nuclei were detected based on the amplification of electrocatalytic single-nanoparticle collision to explore the growth mechanism of Ag shells.The results showed that when 3.2×10-3 mol/L of silver nitrate and 5.3×10-4 mol/L of sodium citrate were added to the Au seed solution,and the reaction continued at 95℃for 60 min,the largest sized spherical Au@AgNPs were synthesized(d≈33 nm),with VAg of about 2.2×10-17 cm3,and both the concentration of silver nitrate solution and sodium citrate solution affected VAg.In addition,it was found that the growth of Ag shells involved nucleation and coalescence,rather than directly deposition on the surface of Au seeds after Ag+reduction.Moreover,the rates of nucleation and growth varied at different stages,reaching up to 1.0×10-17 cm3/min in the first 1 min,decreasing to 5.5×10-20 cm3/min within 30-60 min,and almost 0 cm3/min during 60-120 min,following the pattern of being fast initially,then slowing down,and finally reaching a stagnation point.This work provided a new approach to accurately characterize the synthesis process of core-shell nanomaterials,which was of great significance for precisely constructing efficient core-shell nanomaterials.
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