291911 Polyaniline As a Colorimetric Sensor of Horse Radish Peroxidase
Polyanaline is a conducting polymer that is generally utilized for its electrical conductive properties and its ability to obtain multiple oxidation states through acid/base chemistry. These oxidation states have associated colors as shown in Figure 1, an attribute that is commonly utilized in sensing systems.
Figure 1. Diagram of the oxidation states with pictures of the associated colors. Green Emeraldine changes color from green to blue within the pH range of 6.0 to 7.0. The Blue Emeraldine Base then changes from Blue to purple when oxidized
We developed a colorimetric detection method of hydrogen peroxidase utilizing aqueous polyaniline dispersions as part of a sensing system for bacterial pathogens. Colorimetric detection may provide sensitive detection while eliminating the need for cumbersome quantitative equipment. Aqueous polyaniline dispersions synthesized using interfacial polymerization and sterically stabilized polyaniline dispersions synthesized using oxidative polymerization in the presence of poly(vinyl pyrrolidone) are compared in terms of stability and sensitivity. To determine the limit of detection of each dispersion, various conditions such as pH, temperature, and polymer concentration were manipulated. We also correlate changes in UV spectroscopy of the dispersions such as change in minimum wavelength and change in absorbance at 1.5 nm to visual changes in color. Interestingly, we found that visual determination of changes in color may be more sensitive than monitoring changes in the UV spectroscopy of the dispersions. It was determined that polyanaline synthesized in the interfacial method tended to require less time to visually detect equivalent amounts of HRP when compared to the sterically stabilized polyanaline.
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