The term lignin is used to describe both naturally occurring biopolymer binding cellulose fibers together in plant cells and a byproduct from paper/pulp industry which in fact is a variety of chemical derivatives of the former characterized by lower molecular weight, altered chemical structure and solubility in aqueous and/or organic phases. From chemical point of view, the parent lignin is an amorphous, polyphenolic material arising from an enzyme-mediated dehydrogenative polymerization of three phenylpropanoid monomers, coumaryl, coniferyl and sinapyl alcohol [1]. Being polyphenolic compounds lignin derivatives show substantial electrochemical activity especially in the range of anodic potentials. This talk will focus on the electrochemical properties of two types of technical lignins i.e. kraft lignin and lignosulfonates obtained from sulfide pulping and sulfite pulping respectively. As it will be shown, the two materials as redox active biopolymers with some polyelectrolyte surfactant properties could be applied as:

• dopands of conducting polymers,
• constituents of oxide based nanocomposites based on ZnO and SiO₂,
• dispersing and stabilizing agents of carbon nanotubes [2],
• dispersing and stabilizing agents of metal nanoparticles e.g. silver or gold.

Fig. 1. Photographs of a glassy carbon electrode before (A) and after electrophoretic deposition of silica/lignin biocomposite (B). (C) – SEM pictures of electrophoretic silica/lignin deposit at two magnifications

Many examples of the application of such materials in electrochemical sensing  will be presented and discussed.

Acknowledgement

This work was financially supported by Ministry of Science and Higher Education (Poland)under project No. N N209 450939.

References

[1] Donaldson, L. A. Phytochem. 2001, 57, 859.

[2] Milczarek, G., J. Electronal. Chem. 2010, 638, 178.

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