Browsing by Subject "Solar irradiation"

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    Bismuth-based metamaterials: From narrowband reflective color filter to extremely broadband near perfect absorber
    (De Gruyter, 2019) Ghobadi, Amir; Hajian, Hodjat; Gökbayrak, Murat; Bütün, Bayram; Özbay, Ekmel
    In recent years, sub-wavelength metamaterials-based light perfect absorbers have been the subject of many studies. The most frequently utilized absorber configuration is based on nanostructured plasmonic metals. However, two main drawbacks were raised for this design architecture. One is the fabrication complexity and large scale incompatibility of these nano units. The other one is the inherent limitation of these common metals which mostly operate in the visible frequency range. Recently, strong interference effects in lithography-free planar multilayer designs have been proposed as a solution for tackling these drawbacks. In this paper, we reveal the extraordinary potential of bismuth (Bi) metal in achieving light perfect absorption in a planar design through a broad wavelength regime. For this aim, we adopted a modeling approach based on the transfer matrix method (TMM) to find the ideal conditions for light perfect absorption. According to the findings of our modeling and numerical simulations, it was demonstrated that the use of Bi in the metal-insulator-metal-insulator (MIMI) configuration can simultaneously provide two distinct functionalities; a narrow near unity reflection response and an ultra-broadband near perfect absorption. The reflection behavior can be employed to realize additive color filters in the visible range, while the ultra-broadband absorption response of the design can fully harvest solar irradiation in the visible and near infrared (NIR) ranges. The findings of this paper demonstrate the extraordinary potential of Bi metal for the design of deep sub-wavelength optical devices.
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    Conscientious design of Zn-S/Ti-N layer by transformation of ZnTiO3 on electrospun ZnTiO3@TiO2 nanofibers: stability and reusable photocatalytic performance under visible irradiation
    (American Chemical Society, 2018) Ranjith, K. S.; Uyar, Tamer
    Herein, we report the rational design of Zn-S/Ti-N on TiO2 as a hierarchical nanoarchitecture from the ZnTiO3@TiO2 nanofibers (NFs) through electrospinning followed by a hydrothermal process using l-cysteine as an S/N source. Controlling the hydrothermal temperature, the hierarchical form of NFs exhibited highly efficient visible catalytic behavior for organic dye (i.e., Rhodamine B) degradation since S and N based surface function on the oxide surface resulted in unique interlayer induced strain coupled surface defects. The surface functionalization of the ZnTiO3 surface with S and N was solidly confirmed by X-ray photo-electrospectroscopy (XPS) and energy-dispersive X-ray (EDX) with elemental mapping results. Inducing the S/N functionality at higher hydrothermal temperature reverses the structural arrangement of ZnTiO3 favoring the interaction of S preferably with Zn and Ti with N for the formation of ZnS/TiN@TiO2 NFs. The tunable band function through the Zn-S/Ti-N cofunctionalization exhibited effective long-term catalytic performance under UV and visible irradiation with a degradation rate of 0.0362 and 0.0313 min-1, which is nearly 3.1 and 1.3 times higher than that of the ZnTiO3@TiO2 and ZnTiO3-S/N@TiO2 NFs, respectively. The catalysts are highly photoactive after multiple photocatalytic cycles with stable surface and structural features under visible irradiation. The study could provide new opportunities for designing hierarchical structures in ternary form of nanoscale architectures for effective visible photocatalytic activity. Copyright