Concentration detection of carbon nanotubes in electrophoretic suspension with UV–vis spectrophotometry for application in field emission devices

A simple method to detect the concentration of multiwall carbon nanotubes (MWNTs) and Mg(NO3)2 in electrophoretic suspension was developed. It consists of UV–vis absorbance spectrophotometry for MWNTs and conductivity test for Mg2+. The obtained linear calibration curves were used to determine the amount of MWNTs and Mg2+ in the electrophoretic suspension. Furthermore, the morphologies, field emission properties and compositions of the electrophoretic deposited MWNTs films from suspension were investigated in detail. The results showed that the optimized concentration of MWNTs and Mg(NO3)2 were 0.12 g/L and 0.20 mmol/L in MWNTs electrophoretic suspension, respectively. Under the optimum conditions, the turn-on field of MWNTs cathode was 0.90 V/μm and the maximum emission current density was 2.90 mA/cm2.