Plasmon-Driven Photochemical Reduction Reaction on Silver Nanostructures for Green Fabrication of Superhydrophobic Surface

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection.

Ultrafast Photodynamics of Glucose

We have investigated the photodynamics of β-d-glucose employing our field-induced surface-hopping (FISH) method, which allows us to simulate the coupled electron-nuclear dynamics, explicitly including nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S₁ and S₂ states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs), whose geometries in most cases involve the elongation of a single O-H bond, whereas in some instances, ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations, explicitly including a UV laser pulse of 6.43 eV photon energy, reveal that after initial excitation, the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S₁ state through the same types of CIs as observed in the field-free simulations.