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Thermoplasmonic‐Activated Hydrogel Based Dynamic Light Attenuator
Author(s) -
Pierini Filippo,
Guglielmelli Alexa,
Urbanek Olga,
Nakielski Pawel,
Pezzi Luigia,
Buda Robert,
Lanzi Massimiliano,
Kowalewski Tomasz A.,
De Sio Luciano
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000324
Subject(s) - materials science , opacity , attenuator (electronics) , nanorod , light scattering , optoelectronics , optical transparency , refractive index , optical attenuator , dynamic light scattering , phase transition , nanoparticle , optics , scattering , nanotechnology , composite material , fiber optic sensor , physics , attenuation , fiber , quantum mechanics
This work describes the morphological, optical, and thermo‐optical properties of a temperature‐sensitive hydrogel poly( N ‐isopropylacrylamide‐ co ‐ N ‐isopropylmethacrylamide) [P(NIPAm‐ co ‐NIPMAm]) film containing a specific amount of gold nanorods (GNRs). The light‐induced thermoplasmonic heating of GNRs is used to control the optical scattering of an initially transparent hydrogel film. A hydrated P(NIPAm‐ co ‐NIPMAm) film is optically clear at room temperature. When heated to temperatures over 37 °C via light irradiation with a resonant source (λ = 810 nm) to the GNRs, a reversible phase transition from a swollen hydrated state to a shrunken dehydrated state occurs. This phenomenon causes a drastic and reversible change in the optical transparency from a clear to an opaque state. A significant red shift (≈30 nm) of the longitudinal band can also be seen due to an increased average refractive index surrounding the GNRs. This change is in agreement with an ad hoc theoretical model which uses a modified Gans theory for ellipsoidal nanoparticles. Morphological analysis of the composite film shows the presence of well‐isolated and randomly dispersed GNRs. Thermo‐optical experiments demonstrate an all‐optically controlled light attenuator (65% contrast ratio) which can be easily integrated in several modern optical applications such as smart windows and light‐responsive optical attenuators.