Photoprocesses in Hybrid Nanostructures

J. Hranisavljevic, N.M. Dimitrijevic, G. A. Wurtz, J.S. Im, and G.P. Wiederrecht, J. Am. Chem. Soc., 124, pp. 4536-7 (2003)

Researchers in the Chemistry Division at Argonne National Laboratory have recently studied the unusual photochemistry of molecular J-aggregates on the surface of noble metal nanoparticles. Noble metal nanoparticles are known for free electron waves, or plasmons, that produce extraordinarily intense and confined electromagnetic waves within a few nanometers of the particles’ surfaces. By using molecular J-aggregates, known for their high absorption cross sections, a uniform monolayer of organic electron donors was placed on the surface of the nanoparticles. Ultrafast optical spectroscopy studies revealed a multi-electron, photoinduced reduction of the nanoparticles by the J-aggregates when the plasmon band was optically excited with a femtosecond pulse of light. Reversible charge storage of approximately 300 electrons by the 10-nm-diameter nanoparticles was shown. Scanning near-field optical microscopy studies on organized patterns of closely spaced metallic nanoparticles reveal collective plasmon character. Ultimately, the unusual photochemical properties of functionalized nanoparticles is expected to enable a modulation of collective plasmon properties for subdiffraction limited photon propagation in nanostructures.

Schematic of a photoinduced electron transfer reaction
between the J-aggregate and Ag nanoparticle
following photoexcitation of the plasmon

August 27, 2003