Photoluminescence of metal nanoparticles has drawn considerable research interest due to their potential applications in light-emitting displays, optoelectronics, luminescent sensors, and biomedical imaging. However, the origin and underlying mechanism of photoluminescence in these clusters still remain unclear. Herein, the geometrical and electronic structural changes upon photoexcitation in the Au38(SH)24 and Au22(SH)18 nanoparticles are discussed using time-dependent density functional theory (TDDFT) methods. All structures are optimized in the gas phase using the BP86/DZ level of theory. Bond length changes in the Au23 core of Au38(SH)24 up to a maximum of 0.06 Å lead to small electronic structure changes in the optimized first singlet excited states with different state symmetries. The observed geometric and electronic structure variations upon photoexcitation are relatively small compared to the previously studied Au25(SH)18- nanoparticle and this can be correlated with the Stokes shifts calculated in the range of 0.06-0.09 eV. However, the optimized first singlet and triplet excited states of Au22(SH)18 nanoparticle showed a larger degree of structural flexibility. Since Au22(SH)18 is known to have strong luminescence quantum yields, this flexibility may contribute to its quantum yield. However, the crystal structure of this nanocluster is not known yet, so this flexibility may instead indicate that the previously predicted structure is not optimal.

Luminescence properties of Au38(SH)24 and Au22SH18 nanoparticles

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.