In the past half-century, surface plasmon resonance in noble metallic nanoparticles has been an important research subject. Recent advances in the synthesis, assembly, characterization, and theories of traditional and non-traditional metal nanostructures open a new pathway to the kaleidoscopic applications of plasmonics. However, accurate and precise models of plasmon resonance are still challenging, as its characteristics can be affected by multiple factors. We herein summarize the recent advances of plasmonic nanoparticles and their applications, particularly regarding the fundamentals and applications of surface plasmon resonance (SPR) in Au nanoparticles, plasmon-enhanced upconversion luminescence, and plasmonic chiral metasurfaces.

Electrochromic devices can modulate their light absorption under a small driving voltage, but the requirement for external electrical supplies causes response-lag. To address this problem, self-powered electrochromic devices have been studied recently. However, insensitivity to the surrounding light and unsatisfactory stability of electrochromic devices have hindered their critical applications. Herein, novel perovskite solar cell-powered all-in-one gel electrochromic devices have been assembled and studied in order to achieve automatic light adjustment. Two alkynyl-containing viologen derivatives are synthesized as electrochromic materials, the devices with very high stability (up to 70000 cycles) serves as the energy storage and smart window, while the perovskite solar cell with power-conversion-efficiency up to 18.3% serves as the light detector and power harvester. The combined devices can automatically switch between bleached and colored state to adjust light absorption with variable surrounding light intensity in real-time swiftly, which establish significant potentials for applications as modern all-day intelligent windows.

We demonstrate reflection-mode plasmonic color filters based on lithographically patterned silver nanorods with ultrasmall inter-rod gaps. Fine and effective tuning of the plasmon resonance is shown by varying array periodicities. We determine the dependence of reflected intensity on diameter/periodicity ratio and then develop reflective plasmonic color filters using dense nanorod arrays. Experimental results agree well with theoretical calculations. Our approach is potentially useful for plasmon-assisted sensing, imaging and displays.

A lightweight and portable spectrometer is desirable for miniaturization and integration. The unprecedented capability of optical metasurfaces has shown much promise to perform such a task. We propose and experimentally demonstrate a compact high-resolution spectrometer with a multi-foci metalens. The novel metalens is designed based on wavelength and phase multiplexing, which can accurately map the wavelength information into its focal points located on the same plane. The measured wavelengths in the light spectra agree with simulation results upon the illumination of various incident light spectra. The uniqueness of this technique lies in the novel metalens that can simultaneously realize wavelength splitting and light focusing. The compactness and ultrathin nature of the metalens spectrometer render this technology have potential applications in on-chip integrated photonics where spectral analysis and information processing can be performed in a compact platform.

Transparent wood with high optical transmittance, excellent thermal insulation and high toughness has attracted significant attention as an energy-saving building material. Many research efforts were dedicated to functional transparent wood, from luminescent to electrochromic transparent wood. However, photochromic transparent wood that is highly desirable and critical for smart window applications has been rarely studied. Herein, we experimentally demonstrate photochromic transparent wood with photo-switching of transmittance in the visible light region and color tuning properties. The photochromic transparent wood was obtained by infiltrating the lignin modified wood template with a mixture of photochromic material 3′,3′-dimethyl-6-nitro-spiro[2H-1-benzopyran-2,2′-indoline]-1′-ethanol (DNSE) and pre-polymerized methyl methacrylate (MMA). This photochromic transparent wood exhibits a vibrant purple-to-colorless color change under the illumination of light. In addition, dichroic dye material doped photochromic woods were studied for providing more color change choices. The proposed photochromic transparent wood shows potential applications in mechanically robust, energy-efficient, photo-switchable, and colorful smart windows on a large scale.

Liquid crystals are a promising candidate for development of active plasmonics due to their large birefringence, low driving threshold, and versatile driving methods. We review recent progress on the interdisciplinary research field of liquid crystal based plasmonics. The research scope of this field is to build the next generation of reconfigurable plasmonic devices by combining liquid crystals with plasmonic nanostructures. Various active plasmonic devices, such as switches, modulators, color filters, absorbers, have been demonstrated. This review is structured to cover active plasmonic devices from two aspects: functionalities and driven methods. We hope this review would provide basic knowledge for a new researcher to get familiar with the field, and serve as a reference for experienced researchers to keep up the current research trends.