Silver coated and filled carbon nanotubes: Synthesis, electrical and thermal properties, and iodine vapor sensing

Here we present a simple method to fill multiwalled carbon nanotubes (MWCNT) with silver. This method involves stirring of MWCTs in AgNO3 solution at room temperature in open air followed by heating in H-2 atmosphere at 250 degrees C for two hours. Process also leads to small coating of Ag on the surface. We confirmed the presence of crystalline silver in both coating and filling in hybrid MWCNTs by high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction. After silver coating and filling, bulk thermal diffusivity and thermal conductivity of Ag hybrid MWCNTs were increased by 242% and 255%, respectively. Furthermore, current-voltage measurements using tuna probe in atomic force microscopy showed higher number of charge carriers in the Ag hybrid nanotubes compared to pristine MWCNTs which resulted in up to 173% increase in their electrical conductivity. The Ag hybrid MWCNT based sensor also showed rapid and reversible sensing for I-2 vapors: bulk sensor film demonstrated sensing response of 45% in just similar to 60 s at room temperature. However, the sensor recovery was slower: after removal of I-2 vapors source, the recovery took 400 s and required heating at 100 degrees C in air. Response and recovery of sensor film was maintained after repeated cycles of exposure. Finally, the Ag hybrid MWCNTs film displayed high stability and selectivity for I-2 vapors.

Automated summary

In this study, a simple method to fill multiwalled carbon nanotubes (MWCNT) with silver has been presented, leading to an increase in both the thermal diffusivity and electrical conductivity of the hybrid MWCNTs. The hybrid MWCNT film demonstrated rapid and reversible sensing for I-2 vapors, although the sensor recovery process required heating at a higher temperature. The Ag hybrid MWCNTs film displayed high stability and selectivity for I-2 vapors even after repeated cycles of exposure.