Dual-band high-frequency metamaterial absorber based on patch resonator for solar cell applications and its enhancement with graphene layers

In this paper, a dual-band high-frequency metamaterial absorber based on patch resonator is designed and analyzed for solar cells. In order to obtain a metamaterial absorber, metal-semiconductor-metal layers are combined. The results of the designed structure are shown in the infrared and visible ranges of solar spectrum. Structural parameters and dimensions of the device have a significant importance on the performance of the designed absorber. The simulations are carried out with full-wave electromagnetic (EM) solver based on the finite integration technique. In the first simulation, the constitutive parameters of the structure are selected as constant in which the metamaterial absorber has 99.99% absorption at 558.75 THz and 99% absorption at 216.75 THz. When the structure parameters are designed again according to Drude model, the second simulation results show that the metamaterial absorber has 99.96% absorption at 514.5 THz and 99.63% absorption at 197.25 THz. Moreover, the second simulation results show that the proposed design is also polarization and incident angle insensitive. Furthermore, the structure is enhanced by the integration of the graphene layer(s). In addition, the fractional bandwidths (FBW) for the resonances are also calculated to show the quality of the absorber. As a result, the proposed metamaterial absorber based on patch resonator and its enhancement with graphene present high absorption in the infrared and visible ranges and can be used in many meta material and solar applications

Purification use and toxicity of paramagnetic short multi-walled carbon nanotubes

Carbon nanotubes (CNT) have high surface area and absorption capabilities and the absorption capacity of multi-walled CNTs (MWNTs) enables paramagnetic nanotubes to be obtained by absorbing iron salts. Characterization of paramagnetic MWNTs was performed with TEM, FTIR, DSC, and VSM. Paramagnetic CNTs are used for the purification of water from heavy metals and plastic originated compounds. Most of the PVC-based materials contain phthalate acid esters (PAE) which have considerable effects on human health. In this study, MWNTs were used for removing diethyl phthalate (DEP) from methanol after their toxicity evaluation. Concentration-dependent absorption of 494, 1461, and 2950 ppm, respectively, were measured from the mixture containing 13.3, 33.3, and 66.6% DEP in 40 mg paramagnetic MWNT solution. Although it was concluded that magnetic nanotubes would exhibit significant toxic effects compared to untreated MWNTs, GC-MS results were showed a reliable absorption capacity of magnetic nanotubes for purification applications. The results demonstrated that the use of magnetic MWNTs for the extraction of PAEs is an efficient way from liquids