The interface between nano-sized precious metal clusters such as Silver (Ag) and a semiconductor such as graphite (Gr) is called a heterojunction (Ag/Gr). Heterojunctions have great promise in enhance solar energy conversion due to their unique and enhanced optical, electronic, and chemical properties. When excited with laser pulses, electrons in the system acquire a mean energy higher than its thermal equilibrium value and are referred to as "hot electrons". In fact, graphitic materials are model systems for the study of hot electron dynamics. An ineffective screening within the layers of graphite allows the hot electrons to reach temperatures comparable to that in the solar photosphere!
In a study supported by the Center for Chemistry at the Space-Time Limit recently published in the Journal of the American Chemical Society, Hrvoje Petek and his group modified the Gr surface with Ag nanoclusters (NC)s to investigate how the excitation of the plasmonic resonance of the Ag/Gr heterojunction affects the generation, spatial distributions, and relaxation processes of hot electrons. Plasmonic resonance is a prominent feature of precious-metal nanoparticles; it is a sharp and intense absorption band in the visible range that arise from a collective resonant oscillation of the free electrons of the conduction band of the metal called plasmon.