Thermoplasmonic‐Activated Hydrogel Based Dynamic Light Attenuator

Abstract

This work describes the morphological, optical and thermo-optical properties of a temperaturesensitive 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=810nm) 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 (≈30nm) 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 "adhoc" 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 demonstrated 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.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Ultraviolet-C as a Viable Reprocessing Method for Disposable Masks and Filtering Facepiece Respirators

“…However, these methods face two cardinal problems: they might deform SUPPE irreversibly and face scalability issues [ 3 , 8 , 9 , 12 , 13 , 14 , 20 , 26 ]. In order to deal with such problems, some researchers [ 28 , 29 , 30 ] use nanostructured materials with photothermal properties, such as poly(NIPAm- co -NIPMAm) hydrogels [ 28 , 29 ]. This characteristic enables the absorption of visible/near-infrared light, creating localized heat sources [ 28 ].…”

“…In order to deal with such problems, some researchers [ 28 , 29 , 30 ] use nanostructured materials with photothermal properties, such as poly(NIPAm- co -NIPMAm) hydrogels [ 28 , 29 ]. This characteristic enables the absorption of visible/near-infrared light, creating localized heat sources [ 28 ]. Although this solution might solve the previous problems, it is still in its infancy.…”

Photo-Aligned Nematic Liquid Crystals Enable the Modulation of Thermoplasmonic Heating

“…[1][2][3][4] while for different geometries more complex theoretical models are required. Nowadays, the thermoplasmonic heating is used in several research fields such as high precision medicine [5][6][7], electronics [8][9][10] optics [11][12][13], biology [14,15], and catalysis [16,17]. All above applications are based on the possibility to finely tune the photo-thermal efficiency of the NPs that can be done by acting on several control parameters such as the intensity of the impinging beam [1][2][3][4], the number (N) of involved NPs, and the dielectric function of the surrounding medium ε H [18].…”

Personalized Reusable Face Masks with Smart Nano‐Assisted Destruction of Pathogens for COVID‐19: A Visionary Road

“…As a proof of concept, the photothermal properties of the pristine and Au NR treated FFP2 respirator were experimentally studied by utilizing a thermo‐optical setup described in detail elsewhere [31] . Briefly, we recall that under suitable light illumination, Au NRs absorb light (Figure 2 a, left).…”