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We report a transparent display based on a metasurface of silver nanoparticles (Ag NPs), consisting of a transparent substrate and a layer of Ag NPs deposited by a dielectric film. The Ag NPs metasurface is prepared by a simple and direct annealing process. It presents a deep transmission valley at the wavelength of λ = 468 nm and enables desired transparent display by projecting the monochromatic image onto the metasurface. We also demonstrate that the formed Ag NPs can be approximated as truncated nanospheres, which have obvious directional scattering properties, and can radiate most of the scattered energy into the backward hemisphere with a relatively large angular beamwidth (the full width at half maximum of the scattered intensity) of ∼90°. Therefore, the fabricated displays possess wide viewing angles and high brightness characteristics. Additionally, the transmission modes can be red-shifted to the wavelength of λ = 527 nm by controlling the thickness of the deposited dielectric film. This approach using traditional thin film deposition and moderate annealing processing techniques enables simple, low-cost, and scalable fabrication in large areas for transparent displays.

The widespread use of light emitting diode (LED) based devices makes us inevitably exposed to a blue-enriched environment and brings a potential risk to our eyes. Developing a blue-light-blocking filter with narrow absorbing band, so as to only block harmful blue light (415–455 nm) is highly expected. Here, we create a blue-light-blocking film, consisting of a transparent medium embedded with plasmonic nanoparticles (NPs) that selectively absorb harmful blue light. We present the optimal design based on Mie theory by comprehensive scanning of the parametric space for the NPs, and experimentally demonstrate this concept with a blue-light-blocking film made of silver NPs in a polymer matrix by a simple solvothermal method. For the case of the silver NPs content ∼0.16 wt%, the film can block harmful blue light ∼65% at λ 0 ≈ 430 nm, while maintaining high transparency for the long wavelength light (λ 0 > 500 nm). We also demonstrate that it is possible to correct color cast by optimizing the design of the plasmonic NPs with sharp absorption resonances at yellow waveband. This method has attractive features including simplicity, low cost, non-toxic and scalability to large sizes, which makes it beneficial for blue-light-blocking applications.

Nonlinear optical response could be greatly enhanced when metasurfaces support plasmonic resonances at both fundamental and harmonic wavelengths. However, it is still challenging to fulfill the doubly resonant condition. Here, we propose a dielectric-loading method, which simply coats a conformal thin dielectric layer onto the plasmonic metasurfaces, to introduce an additional degree of freedom and make the doubly resonant condition easily fulfilled. We demonstrate that by simultaneously tuning the thickness of the coated dielectric layer and the geometrical parameters of the gold complementary split-ring resonators (CSRRs), the doubly resonant enhancement of third harmonic generation (THG) could be achieved for any given fundamental wavelengths. We also experimentally verify this concept and show that the THG intensity in the dielectric-loaded CSRRs under the doubly resonant condition could be further increased about 3 times as compared with the case of the conventional CSRRs.

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.

Nonlinear optical processes are promising for many applications, and recently great attention has been paid to improve the nonlinear efficiency of plasmonic metasurfaces. Here, we propose a hybrid structure consisting of a gold split-ring resonator (SRR) based nonlinear metasurface on top of a dielectric waveguide layer. By adjusting the periodicity of the SRR array, we demonstrate that the coupling between the magnetic surface plasmons (MSPs) of the SRRs and the waveguide modes could greatly enhance the second harmonic generation (SHG) intensity. Compared with the conventional SRR arrays, the hybrid structures could provide an extra enhancement in the SHG intensity of more than one order of magnitude.

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.