Nanotube-Based Sensor Detects Gama Rays

Detecting dangerous gamma rays could become simpler and less expensive, thanks to a new sensor based on a carbon nanotube-polymer composite (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200904936). The technology, which relies on a simple resistivity measurement, could find practical use in national security or nuclear research, say MIT’s Timothy M. Swager and Jose M. Lobez, who created the device. The sensor is composed of a network of multiwalled carbon nanotubes embedded in a nonconductive poly(olefin sulfone) matrix. Exposure to gamma rays depolymerizes the matrix, creating low-resistance connections between the nanotubes. This, in turn, leads to an increase in conductivity in the system. Swager and Lobez employed several chemical tricks to boost the performance of their sensor. Using click chemistry, they added pyrene moieties and bismuth complexes to the polymer. The former improve the nanotubes’ dispersion, and the latter increase the system’s opacity to ionizing radiation. The new sensor produces a real-time signal at room temperature, is composed of relatively inexpensive starting materials, and has nearly zero cost of operation, the researchers note.