Nano-carbon: preparation, assessment, and applications for NH3 gas sensor and electromagnetic interference shielding

Abstract

We report on the preparation and characterization of nano-carbon for applications in NH₃ sensing and electromagnetic interference shielding (EMI, X-band, 8–12 GHz). Nano-carbon was synthesized by combustion of 1,7,7-trimethyl-bi-cycloheptan (camphor, C₁₀H₁₆O) deposited at 77 K. Morphological analysis showed nano-carbon was spherically concentric shells (40–50 nm); interconnected spatially. In Raman, vibration modes observed at 1390 (D) and 1580 (G) cm⁻¹, indicated presence of sp³ within sp² shells. UV-visible and photoluminescence spectroscopic analysis revealed that, band gap of nano-carbon was 4.5 eV with midgap of 2.7 eV and two flouro-excited states; making it useful for Fabry–Perot interferometer optical fibre gas sensor. Details of sensor system, its mechanism and transfer function analysis is presented. The system sensitivity was 3 ppm with response and recovery time, respectively, 5 and 8 s. The molecular imprint of NH₃ on nano-carbon (1–5 ppb C-loss/10 cycles; 2 : 1, sp³ : sp² rupture) was obtained that set life time of sensor probe. In EMI, % reflection of nano-carbon was comparable with copper. The losses due to hopping and migration current were large in nano-carbon and attributed to in-plane σ-bond and tetrahedral sites in nano-carbon that interacted with radiation at higher skin depth, around four times more than that of copper. Details of EMI shielding mechanism is presented.