Pulsed laser excitation of phosphate stabilised silver nanoparticles

Laser flash photolysis studies were carried out on two types of silver nano particles prepared by gamma-radiolysis of Ag+ solutions in the presence of polyphosphate as the stabiliser. Type I silver nanoparticles displayed a su rface plasmon band at 390 nm. Type II silver nanoparticles showed a 390 nm surface plasmon band with a shoulder at 550 nm. On photoexcitation in the s urface plasmon band region, using 35 picosecond laser pulses at 355 nm and 532 nm, the type II solutions showed transient bleaching and absorption sig nals in the 450-900 nm region, which did not decay appreciably up to 5 nano seconds. These transient changes were found to get annealed in the interval t where 5 ns < t < 100 ns. Extended photolysis of the nanoparticle solutio ns with repetitive laser pulses resulted in a decrease in the values of the average particle size which were measured by employing the dynamic light s cattering technique.