In the present study, we have studied the applicability of terahertz (THz) metamaterials for sensing low concentrations of premium explosives like RDX and TNT. A parallel metal-pair-based metamaterial has been investigated. The structure exhibits a Fano resonance at 0.627 THz in reflection geometry within the 0.1 to 1 THz range. The unit cell of the metamaterial comprises two asymmetric aluminium rod-like structures on an intrinsic silicon wafer with dimensions of 100 μm and 80 μm, respectively, and a silicon wafer thickness of 40 μm. The structure's periodicity is 120 μm along the x and y directions. We have also performed COMSOL-based simulations of metamaterial structures with different analyte thicknesses in conjunction with experimental verification. In the experiment, for an analyte thickness of 0.5 μm, the structure exhibits a refractive index-dependent sensitivity (S) of 5.1 GHz/RIU. For explosives, resonance peak shifts of 0.031 THz for TNT (refractive index 1.61) and 0.043 THz for RDX (refractive index 1.85) were observed from their respective resonance positions at 0.627 THz. These findings underscore the efficacy of THz metamaterials for detecting trace amounts of explosives.
Reduced Graphene Oxide (rGO) and other graphene-based two-dimensional (2D) materials exhibit promising potential across various fields, such as energy storage, solar cells, and sensors. However, concerns regarding the toxic nature of rGO in biomedical applications have been raised. In this study, we investigate the feasibility of utilizing hole arrays as a sensing platform for detecting the presence of rGO through the modulation of Surface Plasmon Resonance (SPR) via Extraordinary Transmission phenomena (EOT) in the Terahertz (THz) regime. The rGO is prepared using the Hummers method and subsequent reduction of Graphene Oxide (GO). Characterization of the reduced material is performed using Fourier-Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD), confirming successful reduction. Deposition of rGO on top of hole arrays resulted in changes in SPR frequency, indicating a responsive sensing platform sensitive to changes in rGO thickness. Experimental findings are further verified through numerical simulations. Our study highlights the potential of surface plasmon-based sensing platforms for the detection of rGO using hole arrays in the THz regime.
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