Plasmonic Nanocrystals with Complex Shapes for Photocatalysis and Growth: Contrasting Anisotropic Hot‐Electron Generation with the Photothermal Effect

Abstract

In plasmonics, and particularly in plasmonic photochemistry, the effect of hotelectron generation is an exciting phenomenon driving new fundamental and applied research.However, obtaining a microscopic description of the hot-electron states represents a challenging problem, limiting our capability to design efficient nanoantennas exploiting these excited carriers. This paper addresses this limitation and studies the spatial distributions of the photophysical dynamic parameters controlling the local surface photochemistry on a plasmonic nanocrystal. We found that the generation of energetic electrons and holes in small plasmonic nanocrystals with complex shapes is strongly position-dependent and anisotropic, whereas the 2 phototemperature across the nanocrystal surface is nearly uniform. Our formalism includes three mechanisms for the generation of excited carriers: the Drude process, the surface-assisted generation of hot-electrons in the sp-band, and the excitation of interband d-holes. Our computations show that the hot-carrier generation originating from these mechanisms reflects the internal structure of hot spots in nanocrystals with complex shapes. The injection of energetic carriers and increased surface phototemperature are driving forces for photocatalytic and photo-growth processes on the surface of plasmonic nanostructures. Therefore, developing a consistent microscopic theory of such processes is necessary for designing efficient nanoantennas for photocatalytic applications.

Manipulation of Fluid Convection by Surface Lattice Resonance

“…This is because the thermal conductivity of the metal is so much greater than that of the surrounding water that heat flows much faster inside the metal than in water. [ 5,44,45 ] In addition, the line plots’ comparison of SLR‐ and LSP‐based metasurfaces verifies the vital role of the metallic film to the SLR‐based metasurface, that is, it can not only effectively diffuse the heat generated by the nanodisk but also increase the spatial extent of the temperature distribution through its heat dissipation. In general, the SLR‐based metasurface platform allows extensive reconfigurability of the temperature field in space and time, which provides a higher degree of control for future applications such as optofluidic and particle manipulation.…”

“…This effect proves that the largest local electric field enhancement location does not guarantee the strongest thermal power. [5,43] This is because the optical hotspots usually come from the tip effect and charge accumulation at the metal interface. On the contrary, heat is generated from the place where the charge flows freely.…”

“…[3] In particular, photothermal effects in plasmonic nanoparticles (NPs) can be enhanced via enhanced light absorption, generating heat via nonradiative decay channel. [4][5][6][7][8] One can thereby manipulate fluid flows; and control suspended objects at the subwavelength scale by using plasmonics. Localized surface plasmon (LSP) and surface plasmon polariton (SPP) have been developed to manipulate fluid convection, living cells, DNA, and proteins.…”

Enhanced Photocatalytic Activity and Photoluminescence of ZnO Nano-Wires Coupled with Aluminum Nanostructures

“…For the hybrid-structure ZnONWs/AlNSs (5 nm and 9 nm; 450 °C), the photodegradation rates were 70% and 52% after 120 min irradiation time, respectively. For further exploration, the Langmuir–Hinshelwood (L–H) model was used to determine the methylene blue dye’s degradation rate constant [ 40 , 41 , 42 , 43 ]: where : concentration initial of MB; : concentration of MB after illumination time t ; : pseudo-first-order of kinetic rate degradation (rate constant).…”

“…So, during the excitation with the spotlight source at 365 nm, both the LSPR of AlNSs and the excitonic peak of ZnO are excited. The absorbed light at the plasmon wavelength generates a non-equilibrium distribution of electrons, which can decay in the generation of hot electrons on the surface of the nanostructure or low-energy electrons inside the nanostructure [ 40 ]. The generation of the latter ones results in heat in metals.…”