An Optical Chemical Sensor Based on Polymer Swelling and Shrinking using Dithiocarbamate-Polymer Microspheres
Files
Date
2009-03-18
Authors
Odeh, I.
Siam, S.
Khatib, M.
Shakhsher, Z.
Journal Title
Journal ISSN
Volume Title
Publisher
Deanship of Research and Graduate Studies, Yarmouk University, Irbid, Jordan
Abstract
In this work, an optical chemical sensor based on a swelling and shrinking polymer has been developed. A dithiocarbamate functional group was attached chemically to the backbone of
poly vinyl benzyl chloride which was lightly crosslinked with divinyl benzene. The derivatized polymer microspheres were dispersed in a hydrogel membrane to produce a sensing element. This modified membrane was used for sensing specific heavy metal ions, such as Hg2+. The response is based on the interaction between the metal cations with the negative
charges of the deprotonated dithiocarbamate functional group, whereby the swellable polymer undergoes shrinking as a result of neutralization of the negative charges of this functional group. This complex formation of a metal cation with a dithiocarbamate functionality causes significant changes in the optical properties of the sensing element. Shrinking of the polymer microspheres resulted in a decrease in the optical transmission through the sensing membrane. This is due to the increasing difference in refractive indices between the microspheres and the dispersing hydrogel membrane. This sensor showed a good response particularly to mercury ion. There was insignificant response to H+ in the pH range 2 -13. In addition, there was no detectable response towards alkali, alkaline earth metals and other heavy metal ions such as Pb2+, Zn2+, and Cd2+.