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We experimentally and theoretically investigate the influence of alumina coating on the second-harmonic generation (SHG) from split-ring resonator shaped air apertures engraved in a gold film, which are also termed as complementary split-ring resonators (CSRRs). By coating the CSRR arrays with alumina film of certain thickness, we precisely tune their electric diploe resonances (EDRs) to overlap the fundamental wavelength (FW) and realize the EDR enhanced SHG process. On this basis, by shortening the arm length of the CSRRs and then coating them with a certain thickness of the alumina film, we have achieved an SHG enhancement of nearly 1.2-fold in experiment and 8-fold in simulation compared to the CSRR array with an unshortened arm length. We attributed it to the improvement of the magnitude of the effective nonlinear source due to the realization of a doubly-resonant condition. As a flexible method, dielectric coating not only is beneficial to precisely and dynamically optimize the linear and nonlinear properties of the as-fabricated nanoscale devices but also can play the role of a protective layer, which can partially improve the damage threshold of these plasmonic nanoscale devices.

We report on the experimental investigation of polarity-switchable hot electron-induced photocurrents in dual-plasmonic nanostructures, consisting of two layers of gold nanoparticles (AuNPs) separated by a TiO2 film. Hot electrons generated through the non-radiative decay of the localized surface plasmon resonances supported by the top and bottom layers of AuNPs can be simultaneously injected into the TiO2 film in opposite directions and counteract each other. As a result, the polarity and magnitude of the net photocurrents can be tailored by controlling the population of hot electrons either generated from or collected by the two layers of AuNPs. We believe the wavelength-dependent photocurrent polarity switching could be useful for biosensors with a direct electrical readout and photoconversion applications.

A porous NiFe (oxy)hydroxide catalyst fabricated on n+pp+-Si/Ni/NiOx, which is converted from an electrodeposited NiFe oxysulfide, allows a silicon photoanode for water splitting to hit a record 5.1% efficiency with good stability of up to 135 h under 40 mA cm−2 in 1.0 M NaOH.

We report a potential efficient fluorescent label based on the dyed dielectric-metal core–shell resonators (DMCSRs). By utilizing the near-field coupling between the dyes and the multipolar sharp cavity plasmon resonances, the dyed DMCSRs with diameter of 1.02 μm are demonstrated to be capable of supporting multiple spontaneous emission peaks with the linewidths as narrow as ~ 10 nm in visible range, and these reshaped fluorescent emissions are insensitive to the surrounding dielectric environment. Furthermore, these multiple narrow emission peaks show a precise tunability on the spectrum by simply separating a nanometric dielectric layer between the dielectric core and the metallic shell, which may provide an attractive spectral multiplexing strategy in the fields of cell biology and medical sciences.

We experimentally report improved photocurrent performance under the illumination of both UV and visible light in the metal–semiconductor–metal nanostructures with double Schottky barriers, consisting of a monolayer of Au nanoparticles and a planar Au film separated by a thin WO3 layer. In addition to the near-unit broadband optical absorption causing the increased population of hot electrons, we demonstrate that the occurrence of the electron trapping effect at the bottom Schottky barrier is also responsible for the photocurrent enhancement under visible light illumination. Under the direct UV bandgap excitation of WO3, the electron trapping effect at the bottom barrier plays a crucial role in the anodic photocurrent enhancement. Furthermore, we demonstrate that by replacing the Au film with the metal Pt of higher work function to increase the barrier height of the bottom Schottky barrier, and hence strengthening its ability for electron trapping, the photocurrent is found to gain a further significant enhancement under the illumination of both visible and UV light.

We report experimental investigation of the effect of the cobalt hydroxide (Co(OH)2) decoration on the photocatalytic activity of the titanium dioxide (TiO2) films. We demonstrate that the decoration of Co(OH)2 is able to red-shift the absorption edge of the TiO2 film from UV to the visible light region, enhance the optical absorption, and facilitate the charge separation and transfer. As a result, the Co(OH)2-TiO2 composite film is found to exhibit much larger photocurrent and higher performance in photocatalytic degradation of methyl orange than the pure TiO2 film.