Polymeric Sensors and Actuators

Chapter 7

Optical Sensors

Optical sensing techniques belong to the oldest and best established methods. Optical sensors are used for the detection and quantification in a wide field of analytical methods, including the medical, pharmaceutical, environmental, defense, bioprocessing, and food industries. There is still a continuous demand for simple, rapid, sensitive, and in situ monitoring techniques that explains the continuous interest in research (1).

Fluorescent probes for sensing processes in polymers have been reviewed (2). In general, the intrinsic fluorescence of polymers is unspecific so it is not useful to analyze their properties or to correlate changes in their microenvironment. However, when the polymers are modified, they can be readily used for detecting certain analytes. Optical biosensors have been recently reviewed, among other types of biosensors (3, pp. 297–300).

7.1 Conjugated Polymers

Conjugate structures between each repeating unit of a polymer results in a semiconductive molecular wire. The energy transfer of excitons along the conjugated backbones is very fast, therefore, sensors based on conjugated polymers are extremely sensitive to minor perturbations and an amplification of a response of the collective system occurs. This behavior is advantageous over sensors made from small molecules (4,5).

The first conjugated polymer (CP), was a halogenated poly(acetylene) that was discovered in 1977 (6). It was found that the electrical conductivity increases by ...