Wavelength-Selective Photocatalysis Using Gold-Platinum Nanorattles

The selectivity of a thermal catalyzed reaction with multiple products, catalyzed on the surface of a catalyst exhibiting different surface facets and surface energy, is controlled by the temperature. Manipulating the temperature makes one product more dominant than the other. The selectivity of the photochemical reaction on the surface of plasmonic nanocatalyst of multiple plasmon modes is controlled by changing the wavelength of the exciting light. Gold nanospheres (AuNSs) located inside gold platinum double-shell nanoparticles in a rattle structure were prepared with different sizes and showed two plasmon spectral modes. The high-energy plasmon mode corresponds to the photoexcitation of the small nanosphere, whereas the low-energy plasmonic mode is related to both the gold platinum double-shell plasmon and the inside nanosphere, as assigned by calculation using the discrete dipole approximation (DDA) simulation technique. Photodimerization of 4-nitrothiophenol (4NTP) adsorbed on the surface of gold-platinum nanorattles (AuPtNRTs) was studied using the surface-enhanced Raman spectroscopy technique. When the AuPtNRTs are photoexcited at the high-energy band at 532 nm, which selectively excites the AuNS, 4NTP is photodimerized into an azo compound only on the surface of the AuNS. The 4NTP adsorbed on the surface of the outer gold platinum double shell did not react. Although the 785 nm photons excite both the AuNS and the outer shell of the AuPtNRTs, no photodimerization is observed with such low-energy photons.