Silver nanoparticle catalyzed reduction of aromatic nitro compounds

The combination of catalytic quantities of silver metal nanoparticles with NaBH4 smoothly reduces aromatic nitro compounds to amines in aqueous medium. Silver nanoparticles formed in situ are the active catalyst. The kinetic parameters of the reaction with still growing microelectrode (GME) and full grown microelectrode (FGME) silver metal particles in aqueous solution have been compared taking the plasmon band of the silver metal nanoparticles into consideration. In aqueous solution the reaction follows a first order kinetics with the full-grown (FGME) particles and zero order kinetics with the still growing particles (GME). The metal surface remains active and the activity remains unaltered throughout the course of the reduction. Catalysis was due to the efficient nanoparticle mediated electron transfer from BH4- ion to the nitro compounds. Nitro compounds like 2-nitrophenol (2-NP), 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) were tested with NaBH4 using both GME and FGME as catalyst and their rate of reduction has been observed to follow the sequence, 4-NP > 2-NP > 4-NA. (C) 2002 Elsevier Science B.V. All rights reserved.