Label-free electronic detection of DNA using simple double-walled carbon nanotube resistors

Label-free electrical detection of DNA hybridization using resistive sensing devices based on drop-casted doubled-walled carbon nanotube (DWNT) networks and as-grown films is presented. Sensitive, selective, and reliable detection of DNA hybridization is achieved by simple two-terminal measurements, which is suitable for the hand-held type of device applications. Our approach is able to detect DNA concentrations ranging from 50 to 500 nM. Utilizing location-selective capping by photoresists, we designed experiments to reveal the sensing mechanism and found that the carbon nanotube (CNT)-metal junction may not play a dominant role in sensing as it does in single-walled carbon nanotube-based transistor devices. A charge-transfer model is proposed to explain the detection mechanism.