DNA-Functionalized Carbon Nanotube Chemical Sensors

     We have developed chemical sensors consisting of a single-walled carbon nanotube field effect transistor (swCN-FET) with a nanoscale layer of single stranded DNA (ssDNA) adsorbed to the tube's outerwall. The current through the swCN-FET shows a characteristic response to gaseous analytes. This response varies depending on the base sequence of the adsorbed ssDNA.These sensors have been able to detect methanol, trimethylamine, propionic acid, dimethyl methylphosphonate (a simulant of sarin), and dinitrotoluene (a derivative of TNT) at the ppm level. The response and recovery of this biosensor is on the order of seconds.

Figure 1: DNA-Functionalized Carbon Nanotube Chemical Sensor

Polymer and Metal Oxide Nanowire Chemical Sensors

     The Johnson Group is also studying neural network nanogas sensor arrays in cooperation with Dr. Mallouk's group at Penn State. The arrays may consist of various nanowires , e.g. PEDOT/PSS polymer nanowires, SnO2 nanowires, etc., which are sensitive to different gases.  A neural network of these arrays can identify gases with much higher realiability. This topic is interesting because it's a big step in realizing Artificial Electronic NanoNoses. We electroplate on the filter membranes to prepare the nanowires and use dielectrophoresis to assemble the nanowires onto specific loations on the IC chip. Currently only Yaping is working on this project in our group.
 

Figure 2: A single nanowire assembled onto a 6um gap and its I-V curve

Figure 3: A single nanowire exposed to different chemicals at different concentrations