Lignosulfonate-Based Conducting Flexible Polymeric Membranes for Liquid Sensing Applications

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Lignosulfonate (LS) is a byproduct of wood pulping.
• Developing advanced materials for chemical sensors is crucial.
• Conducting polymer composites offer unique properties for sensing applications.

Purpose of the Study:

• To synthesize and characterize LS-based polyurethanes (PUs) doped with multiwalled carbon nanotubes (MWCNTs).
• To evaluate the performance of these composites as sensitive materials in all-solid-state potentiometric chemical sensors.
• To investigate the sensor's response to various transition metals and ionic liquids.

Main Methods:

• Synthesis of LS-based PUs doped with MWCNTs at varying concentrations (0.1-1.4% w/w).
• Fabrication of all-solid-state potentiometric chemical sensors using the synthesized composite.
• Electrochemical characterization and performance testing of the sensors with different analytes (transition metals, ionic liquids) at various pH levels.

Main Results:

• LS-based PUs doped with 1.0% w/w MWCNTs achieved suitable electrical conductivity for sensor applications.
• The developed potentiometric sensor exhibited near-Nernstian or super-Nernstian responses to a wide range of transition metals (Cu(II), Zn(II), Cd(II), Cr(III), Cr(VI), Hg(II), Ag(I)) at pH 7 and Cr(VI) at pH 2.
• The sensor demonstrated a redox response to Fe(II)/(III) at pH 2 and showed no irreversible complexation with Hg(II), unlike other lignin-based sensors.
• Composites doped with graphene oxide (GO), reduced GO (rGO), and graphite (Gr) did not achieve comparable electrical conductivity.

Conclusions:

• LS-based PUs doped with MWCNTs form a unique conducting copolymer composite suitable for sensitive material in potentiometric chemical sensors.
• The developed sensor offers high sensitivity and selectivity for various transition metals and exhibits improved stability compared to existing lignin-based sensors.
• MWCNTs are superior fillers compared to GO, rGO, and Gr for enhancing the electrical conductivity of LS-based polymer composites for sensor applications.