Transmittance Tunable Smart Window Based on Magnetically Responsive 1D Nanochains

Abstract

Smart optical materials are drawing more and more attention because of their wide application in energy conservation, wearable sensors, optical tuning, and medical devices. However, current smart optical materials, including electroresponsive, thermoresponsive, and mechanoresponsive materials, are greatly restricted in practical applications because of their long response time, complicated preparation, and high cost. This study develops a novel, magnetically tunable, smart optical material with swift and high-contrast optical switching based on one-dimensional (1D) Fe3O4@SiO2 nanochains (NCs), which have the large shape anisotropy of the 1D structure and the superparamagnetic properties of Fe3O4 particles. The material exhibited a clear transparent state when NCs were arranged parallel to the viewing direction under an applied magnetic field, whereas it showed good shielding effect when the NCs were randomly oriented upon removal of the field. The light transmittance could be dynamically adjusted over the wide range of 20–80% through a small applied magnetic field of 50–100 Oe, which is superior to most of the currently reported systems. This swift, sensitive, and reversible response is attributed to the good responsivity of magnetic NCs. Also, an effective model was proposed to explain the transmittance modulation scheme and forecast its optical potential. The large tunable range and the low triggered field make Fe3O4@SiO2 NCs an advantageous candidate for application in smart windows, optical switchers, and other fields.

Construction of Magnetic Nanochains to Achieve Magnetic Energy Coupling in Scaffold

“…The directional assembly of Fe 3 O 4 nanoparticles into ordered nanochain structures is expected to solve the above problem. Under external magnetic eld, the internal magnetic dipole moment of Fe 3 O 4 nanoparticles enable to be rapidly de ected to the direction of magnetic eld [10,11]. Moreover, the attractive magnetic dipole interaction drives multiple Fe 3 O 4 nanoparticles to assemble into ordered magnetic nanochain structures along with magnetic force lines [12,13].…”

Index-Matched Composite Colloidal Crystals of Core–Shell Particles for Strong Structural Colors and Optical Transparency

“…Photonic crystals (PCs) are periodically structured materials in which light propagation is prohibited across a specific frequency range, known as photonic band gaps. , Monodisperse colloidal particles can be crystallized into face-centered-cubic (FCC) colloidal photonic crystals (CPCs) by self-assembly . They do not have a complete or three-dimensional photonic band gap but a pseudo photonic band gap along the (111) direction or an optical stopband showing reflective structural colors. , Because of these unique optical properties, CPCs have been extensively investigated for their potential use in a wide range of practical applications such as nonbleaching inks and paints, − stimulus-responsive sensors, − reflective displays, − luminescence enhancement, , optical waveguides, , light harvesting of solar cells, , and smart windows. , To date, colloidal crystals have been obtained by a variety of self-assembly methods including dip coating, convective assembly, spin coating, melt-shear organization, electric-field-assisted printing, and Langmuir–Blodget films . However, due to inevitable defects such as point defects or grain boundaries, the colloidal crystals showed a white background by strong multiple scattering, thereby significantly limiting their practical application in visual observation.…”

“…4,5 Because of these unique optical properties, CPCs have been extensively investigated for their potential use in a wide range of practical applications such as nonbleaching inks and paints, 6−8 stimulus-responsive sensors, 9−12 reflective displays, 13−17 luminescence enhancement, 18,19 optical waveguides, 20,21 light harvesting of solar cells, 22,23 and smart windows. 24,25 To date, colloidal crystals have been obtained by a variety of self-assembly methods including dip coating, 26 convective assembly, 27 spin coating, 28 melt-shear organization, 29 electric-field-assisted printing, 15 and Langmuir−Blodget films. 30 However, due to inevitable defects such as point defects or grain boundaries, 31 the colloidal crystals showed a white background by strong multiple scattering, thereby significantly limiting their practical application in visual observation.…”

Piston-Type Optical Modulator for Dynamic Thermal Radiation Tuning Applications

“…As a result, many dynamic tuning techniques have been studied and applied in the past years. Researchers have demonstrated control over spectral properties mechanically [ 3 , 5 , 6 , 7 , 8 ], thermally [ 1 , 2 , 9 , 10 , 11 , 12 ], electrically [ 13 , 14 , 15 , 16 , 17 , 18 ], optically [ 19 , 20 , 21 , 22 ], and magnetically [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ], leading to a multitude of practical devices.…”

“…Researchers have achieved optical tuning by utilizing lasers to induce a liquid crystal phase change [ 21 ] and through ultraviolet pulse modification used to modify the resonance frequencies [ 22 ]. Additionally, magnetic fields have been applied to induce dielectric function anisotropy in both the near field [ 25 , 26 ] and the far field [ 27 ], to modify the orientation of nanochains within silicon dioxide to alter transmissivity [ 28 ], and to induce the piezophotonic effect via magnetic field excitation at specific frequencies [ 29 ].…”