Na2hpo4 2h2o

All chemicals, i.e., 2,6-dihydroxynaphthalene (Aldrich, Steinheim, Germany), Na₂HPO₄·2H₂O (Riedel-de Haën, Seelze, Germany), NaH₂PO₄·2 H₂O (Merck), KCl (Sigma-Aldrich, Darmstadt, Germany), NaOH (Sigma, Darmstadt, Germany), NaNO₂ (Riedel-de Haën, Seelze, Germany), H₂O₂ 30% (Sigma-Aldrich), MnO₂ (Merck, Darmstadt, Germany), HCl (Merck) and ascorbic acid (Sigma-Aldrich) were used without any further purification. Bidistilled water was used to prepare all solutions. Screen printed carbon electrodes (SPCE, Product code: DRP-110) from DropSens, (Llanera, Asturias, Spain) were used in all electrochemical experiments.

Sapwood of spruce wood (Picea abies) from Switzerland was used. For wood functionalization, succinic anhydride and acetone were purchased from Sigma-Aldrich (St. Louis, MI, USA). Pyridine (anhydrous grade) was obtained from VWR (Radnor, PA, USA). Tip functionalization required 11-mercaptoundecanoic acid (HOOC(CH₂)₁₀SH, ≥ 95%, Sigma-Aldrich), 11-mercapto-1-undecanol (OH(CH₂)₁₁SH, ≥ 97%, Sigma-Aldrich) and ethanol (HPLC grade, ≥ 99.8%, Sigma-Aldrich). Buffer preparation in the pH range from pH 2 to pH 12 required water (HPLC plus grade, Sigma Aldrich), monobasic sodium phosphate (NaH₂PO₄ anhydrous, ≥ 99.0%, Sigma-Aldrich), phosphoric acid (H₃PO₄, 85wt%, Sigma-Aldrich), sodium phosphate dibasic dihydrate (Na₂HPO₄*2H2O, ≥ 99.5%, Riedel-de Haën, Seelze, Germany) and trisodium phosphate dodecahydrate (Na₃PO₄*12H₂O, ≥ 98%, Sigma-Aldrich).

Aniline (Sigma-Aldrich, Saint Louis, MO, USA) was distilled in vacuo before use. Na₂HPO₄‧2H₂O (Riedel-de Haën, Seelze, Germany), 2,2-azino-bis(3-ethyl-benzthiazoline-6-sulfonate (ABTS), citric acid anhydrous, sodium dodecylbenzenesulfonate (DBSNa), potassium octacyanomolybdate (IV) hydrate (Sigma-Aldrich, Steinheim, Germany), ammonium peroxodisulfate (Carl Roth GmbH, Karlsruhe, Germany), and tetrahydrofurane (Lab-Scan, Gliwice, Poland) were used without further purification. All the solutions were prepared using water purified with a Simplicity^® Water Purification System (Merck KGaA, Darmstadt, Germany).