Polymers are versatile materials that we employ to develop new sensing devices. The primary target analyte are explosives, especially TNT. The goal is to create versatile sensors that can be readily adapted to emerging threats.

Two approaches are being used to design highly sensitive sensors for explosives. The first uses sensory polymers that are incorporated into high surface area substrates such as porous silicon or sol-gels. The polymers are chosen to be fluorescent so that an optical readout is used to quantitate the presence or absence of analyte. The high surface area of the substrate increases the likelihood that an analyte will encounter the sensing polymer, which increases the sensitivity of the device considerably. The second approach is to use quantum dots decorated with molecules that interact specifically with target molecules. Quantum dots exhibit strong fluorescence whose emission wavelength can be tuned by changing the size of the quantum dot. By matching the emission wavelength of the quantum dot to the absorption energy of a bound analyte, resonance energy transfer can occur that will affect the fluorescence intensity of the quantum dot. This provides a sensitive transduction mechanism that is further enhanced by the large surface area of the quantum dots. This work is funded by NSF and the DHS Center of Excellence.