Controllable terahertz conductivity in single walled carbon nanotube/polymer composites

Terahertz (THz) conductivity of single walled carbon nanotube (SWNT)/poly-vinyl alcohol (PVA) composites has been studied in the frequency window of 0.3-2.0 THz. SWNT/PVA composite films with a constant thickness of 300 +/- 20 mu m are grown by dispersing required amount of SWNT in PVA solution via a slow drying process at room temperature under ambient condition. THz time domain spectroscopic measurements have been performed in transmission geometry at room temperature under N2 atmosphere and THz conductivity spectra have been extracted from the time domain data. It is found that conductivity of these samples can be efficiently tuned by changing the length of the SWNTs and also the SWNT weight fraction. For the highest weight fraction at a frequency of 1.5 THz, longer SWNT sample (average length similar to 15 mu m) showed 80% increased conductivity than its shorter counterpart (average length similar to 2 mu m) of the same diameter (1-2 nm). Shielding effectiveness of the samples has also been engineered by simply changing the effective length of SWNT inclusion in the polymer matrix. A modified Universal Dynamic Response model is applied to analyze the conductivity spectra of the samples. (C) 2015 AIP Publishing LLC.