This contribution reports, for what we believe is the first time, on
V
O
2
-based thin-film coatings on flexible Al substrates exhibiting a tunable positive emittance-switching
Δ
ε
=
(
ε
H
-
ε
L
)
>
0
. More precisely, a layered stack of a-
S
i
:
H
/
S
i
O
2
/
V
O
2
on flexible Al sheets presents minimum and maximum values of emissivity of about 0.18 and 0.57 at 40ºC and 83ºC, respectively, and hence allows an emittance-switching
Δ
ε
of 0.39 and a relative variation
Δ
ε
/
ε
Λ
of
∼
217
%
. Such variations fit with the potential applications of such coatings as smart radiation devices in small satellites and spacecraft.
In line with the renewed interest in developing novel Non Linear Optical (NLO) materials, natural Lycopene’s NLO Properties are reported for the first time within the scientific literature. Correlated to its 1-D conjugated π-electrons linear conformation, it is shown that natural Lycopene exhibits a significantly elevated 3rd order nonlinearity χ(3) as high as 2.65 10−6 esu, the largest value of any investigated natural phyto-compound so far, including β-carotene. In addition to a saturable absorption, the corresponding observed self-defocusing effect in Lycopene seems to be the result of a thermal nonlinearity. The nonlinear response coupled to the observed fluorescence in the Visible spectral range points to a potential photodynamic therapy application as well as the possibility of engineering of novel hybrid Lycopene based NLO nano-materials.
In this study, V2O5/V/V2O5 sandwich-structured films were deposited on glass substrates by electron beam evaporation. The thickness of the first (bottom) V2O5 layer was 40 nm and the last (top) layer was 20 nm, while that of the sandwiched vanadium layer varied up to 12 nm for different samples. The effects of varying the thickness of the sandwiched vanadium layer on microstructural and thermochromic properties of the as-deposited and thermal annealed films were investigated. Ultrahigh-resolution scanning electron microscopy revealed the presence of nanostructures with various irregular shapes on the surfaces of all films. Also, the atomic force microscopy revealed an average roughness of ∼10–38 nm for increasing thickness of the sandwiched vanadium layer. X-ray powder diffraction measurements showed the presence of the monoclinic VO2 (M) crystal structure of the films with (011) preferred orientation at 27.94° for both 7 and 12 nm thicknesses of the sandwiched vanadium layers. The varying thickness of the sandwiched vanadium layers enhanced phase transition temperature values to ∼33.92 and ∼29.11 °C for both 7 and 12 nm thicknesses of the sandwiched layers, respectively. These enhanced transition temperature values, as a result of thickness variation of the sandwiched vanadium layers, pointed toward utilization of this method in the successful synthesis of VO2 films for thermochromic windows application and optoelectronics.
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