An electronically pure carbon nanotube ink, includes a population of semiconducting carbon nanotubes suspended in a liquid, the ink being essentially free of metallic impurities and organic material, and characterized in that when incorporated as a carbon nanotube network in a metal/carbon nanotube network/metal double diode, a nonlinear current-bias curve is obtained on application of a potential from 0.01 V to 100 V. The ink can be used to prepare air-stable n-type thin film transistors having performances similar to current thin film transistors used in flat panel displays amorphous silicon devices and high performance p-type thin film transistors with high-κ dielectrics.