Synthesis of bimetallic Pt–Cu nanoparticles and their application in the reduction of rhodamine B

Monometallic (Pt and Cu) and bimetallic (Pt–Cu) nanoparticles were synthesized in water-in-oil microemulsions of water/AOT/hexane by the reduction of their corresponding salt (H2PtCl6 and (CH3COO)2Cu·H2O) with hydrazine hydrate under low temperature condition (5 °C). The particles were characterized for their size, morphology, composition, charge and optical behavior using various techniques like TEM, SAED, DLS, XRD, EDAX, UV–vis spectroscopy, etc. The prepared nanoparticles were reasonably monodispersed with spherical morphology having an average diameter of 3 nm. The synthesized mono and bimetallic nanoparticles were utilized as catalyst in the reduction of a dye rhodamine B (Rh B) using NaBH4 which is otherwise extremely slow. The reaction was studied by observing the decrease in absorbance at 554 nm (characteristic peak of the dye) spectrophotometrically and a comparative study for the catalytic performance of the synthesized bimetallic and individual monometallic nanoparticles was done for the reduction reaction. The degradation reaction follows first order kinetics and the rate constant k, calculated for bimetallic Pt–Cu, monometallic Cu and Pt nanoparticles and uncatalyzed reactions comes out to be 4.5 × 10−2 s−1, 2.7 × 10−3 s−1, 8.0 × 10−4 s−1 and 5.0 × 10−5 s−1 respectively, i.e. the rate constant follows the order kbimet > kCu > kPt > kuncat. Our results show that bimetallic Pt–Cu nanoparticles are very promising for catalytic application as compared to their monometallic nanoparticles which may be attributed to its small size and synergistic effect of two metal nanoparticles.