Synthesis of Platinum Nanoparticles by Reaction of Filamentous Cyanobacteria with Platinum(IV)−Chloride Complex

Abstract

Interaction of cyanobacteria (Plectonemaboryanum UTEX 485) with aqueous platinum(IV)−chloride (PtCl₄°) has been investigated at 25−100 °C for up to 28 days, and 180 °C for 1 day. The addition of PtCl₄° to the cyanobacteria culture initially promoted the precipitation of Pt(II)−organic material as amorphous spherical nanoparticles (≤0.3 μm) in solutions and dispersed nanoparticles within bacterial cells. The spherical Pt(II)−organic nanoparticles were connected into long beadlike chains by a continuous coating of organic material derived from the cyanobacterial cells, and aged to nanoparticles of crystalline platinum metal with increase in temperature and reaction time. The stepwise reduction for the formation of platinum nanoparticles in the presence of cyanobacteria was deduced to be Pt(IV) [PtCl₄°] → Pt(II) [Pt(II)−organics] → Pt(0). Spherical platinum-bearing nanoparticles were not present in abiotic PtCl₄° experiments conducted under similar conditions and duration.