Chemistry Reference
In-Depth Information
CHAPTER 12
COLORIMETRIC SENSING AND
BIOSENSING USING FUNCTIONALIZED
CONJUGATED POLYMERS
AMIT BASU
12.1. INTRODUCTION
A sensor is a device or material that generates a measurable output when an external
stimulus is applied. Living systems routinely use molecular recognition, the associ-
ation of two or more molecules, as a stimulus for sensing in the biological context.
In these cases the output typically consists of subsequent molecular recognition
events, such as modulation of enzymatic activity, activation of signaling pathways,
or communication with neighboring cells. Abiotic sensors, the goal of which is
analyte detection, have been successfully developed by exploiting many natural molecu-
lar recognition systems. Synthetic recognition systems based on biomimicry and host-
guest systems have also been used. The outputs of these synthetic sensors include
changes in electrochemical properties, refractive indices, or spectroscopic signatures.
Conjugated polymers have been extensively studied for their applications in
sensing (Mcquade et al. 2000). They can be readily modified with molecular recog-
nition elements before or after polymerization, affording a modular platform on
which sensors may be built or constructed. In addition, analyte binding often perturbs
the optical and/or conductive properties of conjugated polymers, making them useful
for the development of optical or electrochemical sensors. Although numerous
examples of conjugated polymers that change their fluorescence properties upon
analyte binding have been reported, several types of conjugated polymers also
undergo striking visible color changes. Colorimetric sensing has the advantage that
it frequently requires nothing more than the human eye for detection, although
further quantification can be carried out using absorption spectroscopy.
