Ultrasonic Activation of Platinum Catalysts

The effect of ultrasonic treatment on the crystallinity and activity of platinum nanoparticles is demonstrated. Preformed platinum nanoparticles stabilized with citrate ions were ultrasonically modified in water, poly(vinylpyrrolidone) aqueous solution, and ethylene glycol solution. The rapid heating/cooling cycles of the cavitation microbubbles resulted in melting and formation of amorphous or crystalline platinum nanoparticles with controllable catalytic activity. After 1 h of ultrasonic treatment in all solutions platinum nanoparticles were found to be more crystalline and ordered. Amorphous platinum nanostructures were formed after 20 min of sonication in water, whereas in poly(vinylpyrrolidone) or ethylene glycol solutions they became just less crystalline and more disordered. The catalytic activity of the ultrasonically modified platinum nanoparticles was examined by means of the reaction of the hexacyanoferrate(III) reduction by thiosulfate ions. The fastest catalysis was enabled by platinum nanoparticles after sonication in poly(vinyl pyrrolidone) solution for 1 h, while the lowest activity was found for particles after the ultrasonic treatment for 20 min in ethylene glycol solution. Platinum nanoparticles before and after ultrasonic treatment in water have similar catalytic efficiencies.