Time-dependent wet-processing of HiPCo nanotubes in ∼0.5M phosphoric acid, and its effects upon the structural, transport, infra-red light absorption and photoconduction characteristics were studied. Nanotubes were treated for nominal time intervals of 1, 2 and 3h. The treatment was found to be a two-step process that initially resulted in the removal or partial replacement of most pre-existing C-O, OH and CHx groups by phosphorus oxy and carbonyl groups. According to T-dependent current-voltage measurements, the differential conductance of nanotube networks varied with temperature as ∼Ta, with the exponent exhibiting a slight increase as a result of the treatment; attributed to a slight increase in disorder and not to doping effects. Nanotubes which had been processed for 3h also exhibited an order of magnitude improvement in photoconduction response time, compared to that of untreated tubes, with growth/decay characteristic time-constants approaching the sub-second range.

Investigation of Time-Rated Defect Formation, Infrared Absorption and Transport Characteristics of Single-Walled Carbon Nanotubes Wet-Processed in Phosphoric Acid. M.Omari, T.Hosseini, D.Brocker, N.A.Kouklin: Nano, 2012, 7[4], 1250026