Nanoplasmonics For Photovoltaics And Photocatalysis

Plasmonics, which merges photonics and electronics on nanoscale dimensions, has attracted intensive interest due to its unique properties. Noble metal nanoparticles such as Au and Ag exhibit special Localized Surface Plasmon Resonance (LSPR) effects and thus act as efficient nanosources of light, heat and energetic electrons in photocatalysis and photo to electron conversion processes. Hence, this dissertation focused on the utiiztion of LSPR effects in photovoltaics and photocatalysis. The main content of the dissertation included the following work:1. We designed and constructed core-shell plasmonic nanostructures to realize precise, long separation distance control between the gold core (energy acceptor) and fluorophores (energy donor). Both steady-state and time-resolved fluorescence measurements were employed to investigate radiative properties of the as-prepared nanosystem. The observed overall fluorescence quenching of the core-shell plasmonic nanocomposites with the decrease of shell thickness is attributed to a concurrent increase of nonradiative rates and decrease of radiative rates with the separation distance decrease. However, neither fluorescence resonance energy transfer (FRET) nor nanometal surface energy transfer (NSET) model is suitable for describing the fluorescence quenching efficiency.2. Based on the above-mentioned study, we embedded Au NPs coated with a dielectric SiO2layer into polymer solar cells, attempting to reduce the negative effects of these metallic nanostructures and thus increase photovoltaic photocurrent and efficiency. We constructed inverted polymer solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester, and blended Au NPs coated with SiO2layer, i.e., Au@SiO2core-shell nanostructures into the active layer. Compared with plasmonic solar cells embedded with sole Au NPs. the device incorporating Au@SiO2core-shell nanostructures indeed exhibited significantly augmented photocurrent density, though not a superior overall efficiency. The photocurrent density increase is attributed to the dielectric layer coating Au NPs, which mitigates metal-mediated losses such as exciton quenching, probably induced by the electron accumulation on the metallic surface, but which meanwhile is thin enough to maintain the plasmonic effects of the gold core upon photoexcitation.3. We developed one-step synthesis of carbon quantum dots (CQDs) and employed them both as a reducing agent and a template to fabricate CQDs@Ag NPs. Because of clustering effect of silver nanoparticles on the carbon dots and the coupling effect between excitons and surface plasmons, the photocatalytic efficiency of organic dye degradation was remarkably enhanced.