Optical Sensing Properties of Dithiocarbamate-Functionalized Microspheres, Using a Polyvinylpyridine-Polyvinylbenzyl Chloride Copolymer
Date
2010-10-08
Authors
Shakhsher, Ziad M.
Odeh, Imad M.A.
Rajabi, Inas M.S.
Khatib, Mahmoud K.
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
In this study, a new modified optical chemical sensor based on swellable
polymer microspheres is developed using a 5% copolymer of polyvinylpyridine-polyvinyl
-benzyl chloride microspheres functionalized as the corresponding dithiocarbamate. This
sensor demonstrated significant enhancements in sensitivity, dynamic range and response
time. These improvements are related to the presence of pyridine in the polymer backbone,
which is believed to increase the space between the groups, thus decreasing steric
hindrance, and hence increasing substitution of the dithiocarbamate group. The
hydrophilicity of pyridine also allows free movement of the solvent and analyte to and
from the inside of the microspheres. These dithiocarbamate-derivatized polymer
microspheres were embedded in a hydrogel matrix of polyvinylalcohol cross-linked with
glutaraldehyde. This sensor responded selectively to Hg2+ solutions of different
concentrations (1 × 10−5 M to 0.1 M). The observed turbidity measured as absorbance
varied between 1.05 and 1.75 units at a wavelength of 700 nm. The response is based on
the interaction between the metal cations with the negative charges of the deprotonated
dithiocarbamate functional group, which led to neutratization of the charges and thus to
polymer shrinking. As a result, an increase in the turbidity of the sensing element due to a
change in the refractive index between the hydrogel and the polymer microspheres
occured. The changes in the turbidity of the sensing element were measured as absorbance
using a conventional spectrophotometer.
Description
Keywords
optical sensor , dithiocarbamate-copolymer , polymer swelling