I have carbon nanofibers synthesized by the carbonization of poly-acrylonitrile (PAN) using the electro-spinning technique and deposited silver nanoparticles over it by magnetron sputtering system. I tested the sample for acetylene detection (a reducing gas). The resistance reduced after exposing the gas and returned to base level when turned-off the gas supply, this shows the n-type behavior of the dominant carbon nanofiber. How can I confirm carbon nanofiber's semiconducting behavior using any other experimental process?