Cavitands, nanostructured supramolecules with pre-organized cavities, bind chemical analytes to form guest host complexes. We have demonstrated 1,2 the capability to use cavitands for chemical sensing using a highly sensitive optical transduction scheme viz. surface plasmon resonance (SPR). Cavitands of different types with respect to cavity size and chemical functionality have been shown to be selective for sensing both TICs (toxic industrial chemicals) as well as CWAs (chemical warfare agent simulants) such as DMMP. A comparison with conventional polymer sensing layers suggests that cavitands are more selective due to the presence of binding cavities with prescribed interactions. A second approach is to use nematic liquid crystals3 for chemical sensing. A unique property of these materials is that they amplify local interactions into macroscopic perturbations. We have utilized this property to demonstrate high selectivity and sensitivity for detection of chemical vapors. It is shown that chemical isomers such as m-xylene and p-xylene vapors induce substantially different surface plasmon shifts due to interaction with a thin layer of liquid crystal. These novel materials appear to be highly promising for applications in chemical sensing.

References:

1. “Optical Sensing of the Selective Interaction of Aromatic Vapors with Cavitands.”, by E. Feresenbet, E. Dalcanale, C. Dulcey, and D. K. Shenoy, Sensors and Actuators B. Chemical, 97, 211 (2004).

2. “Effect of Thin Film Processing on Cavitand Selectivity.” By D. K. Shenoy, E. Feresenbet, R. Pinalli, and E. Dalcanale, Langmuir, 19, 10454 (2003).

3. “Optical Chemical Sensing Using Nematic Liquid Crystal.”, by E. Feresenbet, F. Taylor, T. Chinowsky, S. Yee, and D. K. Shenoy, submitted to Sensor Letters.