Tailoring Broad-Band-Absorbed Thermoplasmonic 1D Nanochains for Smart Windows with Adaptive Solar Modulation

Abstract

Controlling solar transmission through windows promises to reduce building energy consumption. A new smart window for adaptive solar modulation is presented in this work proposing the combination of the photothermal one-dimensional (1D) Au nanochains and thermochromic hydrogel. In this adaptive solar modulation system, the Au nanochains act as photoresponsive nanoheaters to stimulate the optical switching of the thermochromic hydrogel. By carefully adjusting the electrostatic interactions between nanoparticles, different chain morphologies and plateau-like broad-band absorption in the NIR region are achieved. Such broad-band-absorbed 1D nanochains possess excellent thermoplasmonic effect and enable the solar modulation with compelling features of improved NIR light shielding, high initial visible transmittance, and fast response speed. The designed smart window based on 1D Au nanochains is capable of shielding 94.1% of the solar irradiation from 300 to 2500 nm and permitting 71.2% of visible light before the optical switching for indoor visual comfort. In addition, outdoor cooling tests in model house under continuous natural solar irradiation reveal the remarkable passive cooling performance up to ∼7.8 °C for the smart window based on 1D Au nanochains, showing its potential in the practical application of building energy saving.

Thermochromic Hydrogels with Dynamic Solar Modulation and Regulatable Critical Response Temperature for Energy‐Saving Smart Windows

“…T lum (380–780 nm), T solar (300–2500 nm) and D T solar could be determined by the following equations: where ϕ lum (λ) is the standard luminous efficiency function for photopic vision, [ 34 ] ϕ solar (λ) is the solar irradiance spectrum for air mass 1.5 (AM1.5, corresponding to the sun standing 37° above the horizon), [ 35 ] T (λ) is the measured spectral transmittance, and T is the testing temperature. Compared with the recently reported results of the most studied inorganic VO 2 thermochromic coatings [ 10,36–38 ] and other hydrogel‐based smart windows, [ 17,39–42 ] an unprecedented combination of high T lum (99.05%) and D T solar (33.42%) could be achieved by applying the Gel‐0.8‐NaCl hydrogel (Table S1, Supporting Information). It is notable that the T lum exceeds all the literature data, while the moderate D T solar value can be attributed to the fact that other smart window technologies allow the full regions of the solar irradiation to through and our hydrogels will block infrared spectra.…”

Multi‐stimuli‐responsive and Multi‐functional Smart Windows

“…Other thermosensitive materials include poly(N‐vinylcaprolactam), [114] methyl‐ or hydroxypropyl cellulose, [115–118] and polyampholyte hydrogels [119] . It has been reported that a faster thermal response can be achieved in these polymers by incorporating Au nanoparticles or Au nanoparticle clusters (Figures 1d–f) [120] . Owing to the LSPR characteristics of Au nanoparticles and their clusters at visible and near‐infrared frequencies, they are able to absorb and scatter the light with different proportionality according to their geometries [121] .…”

“…(e,f) Time‐course change in the window temperatures (e) and indoor temperatures (f) of the bare glass, PNiPAAM‐based smart window, and PNiPAAM‐based smart window containing Au nanoparticle clusters under the irradiation of simulated solar lights. Reproduced with permission [120] . Copyright 2021, American Chemical Society.…”

“…Reproduced with permission. [120] Copyright 2021, American Chemical Society. (g) A schematic for the working principle of the smart windows composed of PNiPAAM-based hydrogel and antimony-tin oxide (ATO) nanoparticles.…”

“…faster thermal response can be achieved in these polymers by incorporating Au nanoparticles or Au nanoparticle clusters (Figures 1d-f). [120] Owing to the LSPR characteristics of Au nanoparticles and their clusters at visible and near-infrared frequencies, they are able to absorb and scatter the light with different proportionality according to their geometries. [121] If the nanoparticles have a high absorption ratio or absorption crosssection, then the absorbed light can be converted to heat, which in turn increases the overall temperature of the window.…”