Nanofibrillar Cellulose‐Chitosan Composite Film Electrodes: Competitive Binding of Triclosan, Fe(CN) 6 3−/4− , and SDS Surfactant

Glassy carbon electrodes are modified with a thin film of a cellulose‐chitosan nanocomposite. Cellulose nanofibrils (of ca. 4 nm diameter and 250 nm length) are employed as an inert backbone and chitosan (poly‐ D ‐glucosamine, low molecular weight, 75–85% deacetylated) is introduced as a structural binder and “receptor” or molecular binding site. The composite films are formed in a solvent evaporation method and prepared in approximately 0.8 μm thickness. The adsorption of three molecular systems into the cellulose‐chitosan films is investigated and approximate Langmuirian binding constants are evaluated: i) Fe(CN) 6 4− ( K Ferrocyanide =2.2×10 3 mol −1 dm 3 in 0.1 M phosphate buffer at pH 6) is observed to bind to ammonium chitosan functionalities (present at pH<7), ii) triclosan ( K Triclosan =2.6×10 3 mol −1 dm 3 in 0.1 M phosphate buffer pH 9.5) is shown to bind only weakly and under alkaline conditions, and iii) the anionic surfactant dodecylsulfate ( K SDS =3.3×10 4 mol −1 dm 3 in 0.1 M phosphate buffer pH 6) is shown to bind relatively more strongly in acidic media. The competitive binding of Fe(CN) 6 4− and dodecylsulfate anions is proposed as a way to accumulate and indirectly determine the anionic surfactant.