Renewable and cheap materials in electrodes could meet the need for low-cost, intermittent electrical energy storage in a renewable energy system if sufficient charge density is obtained. Brown liquor, the waste product from paper processing, contains lignin derivatives. Polymer cathodes can be prepared by electrochemical oxidation of pyrrole to polypyrrole in solutions of lignin derivatives. The quinone group in lignin is used for electron and proton storage and exchange during redox cycling, thus combining charge storage in lignin and polypyrrole in an interpenetrating polypyrrole/lignin composite.

A platinum electrode was modified with electropolymerized films of 4-allyl-2-methoxyphenol (eugenol) by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was than used to determine dopamine (DA) in an excess of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity DA/AA were affected by the potential window applied for the polymerization. For polymerization between 0 and 2.2 V, the peak potentials recorded in a phosphate buffer solution (pH 7.4) were -61 and +152 mV vs Ag/AgCl for AA and DA, respectively. After a 5-min equilibration, relative sensitivity DA/AA was 164 and the current sensitivity for DA was 7.9 nA μM(-)(1). The detection limit for S/N = 3 is 0.1 μM. The high selectivity and sensitivity for DA was found to be due to charge discrimination/analyte accumulation and an effect of catalytic mediation of redox sites. Chronocoulometric data reveal that DA is accumulated on the electrode as a monolayer. The electrode is stable, reversible, and free of fouling problems.

Huge advances achieved recently in elucidating the role of NO in plants have been made possible by the application of NO donors. However, the application of NO to plants in various forms and doses should be subjected to detailed verification criteria. Not all metabolic responses induced by NO donors are reliable and reproducible in other experimental designs. The aim of the presented studies was to investigate the half-life of the most frequently applied donors (SNP, SNAP and GSNO), the rate of NO release under the influence of light and reducing agents. At a comparable donor concentration (500 microM) and under light conditions the highest rate of NO generation was found for SNAP, followed by GSNO and SNP. The measured half-life of the donor in the solution was 3 h for SNAP, 7 h for GSNO and 12 h for SNP. A temporary lack of light inhibited NO release from SNP, both in the solution and SNP-treated leaf tissue, which was measured by the electrochemical method. Also a NO, selective fluorescence indicator DAF-2DA in leaves supplied with different donors showed green fluorescence spots in the epidermal cells mainly in the light. SNP as a NO donor was the most photosensitive. The activity of PAL, which plays an important role in plant defence, was also activated by SNP in the light, not in the dark. S-nitrosothiols (SNAP and GSNO) also underwent photodegradation, although to a lesser degree than SNP. Additionally, NO generation capacity from S-nitrosothiols was shown in the presence of reducing agents, i.e. ascorbic acid and GSH, and the absence of light. The authors of this paper would like to polemicize with the commonly cited statement that "donors are compounds that spontaneously break down to release NO" and wish to point out the fact that the process of donor decomposition depends on the numerous external factors. It may be additionally stimulated or inhibited by live plant tissue, thus it is necessary to take into consideration these aspects and monitor the amount of NO released by the donor.

Renewable materials are requested for large scale electrical storage, a coming necessity with the growth of intermittent solar and wind renewable electricity generation. Biopolymers are a source of inexpensive materials, in particular through the use of black liquor from paper production, a waste product. Interpenetrating networks of the biopolymer lignosulfonate (Lig) and conjugated polymer polypyrrole (Ppy) are synthesized by galvanostatic polymerization from pyrrole/lignosulfonate mixture in acidic aqueous electrolyte. Methoxy and phenolic functional group present in the non‐conducting lignosulfonate are converted to quinone groups. The redox chemistry of quinones is used for charge storage, along with charge storage in polypyrrole. A large variation of the electrochemical activity between lignosulfonates obtained from different sources is observed. The charge storage capacities are significantly enhanced by also including another electroactive dopant, anthraquinone sulfonate (AQS). AQS redox peaks act as an internal reference (standard) to probe the redox electrochemistry of Lig. The synthesized Ppy(Lig) and Ppy(Lig‐AQS) electrodes are characterized by cyclic voltammetry, galvanostatic charge‐discharge cycling, electrochemical quartz crystal microbalance, and atomic force microscopy.

Lignosulfonic acid (LS1) and partially desulfonated lignosulfonic acid (LS2) were oxidatively deposited on a preactivated glassy carbon (GC) electrode, giving rise to redox active films showing three distinct redox couples at midpeak potentials (E degrees ') of 0.22, 0.44, and 0.53 V (vs Ag/AgCl in 0.1 M H(2)SO(4)). The redox activity was assigned to quinone moieties of different degrees of substitution, formed upon the oxidation of electroactive groups in the lignosulfonate structure. The most predominant couple (E degrees ' = 0.44 V) shifted negatively with pH at a rate of 59.5 mV per pH unit. In neutral electrolytes, the LS1- and LS2-modified electrodes behaved as anionic coatings, showing an increase in the charge transfer resistance (R(ct)) for the ferrocyanide/ferricyanide redox couple. The change in R(ct) was highly dependent on the LS sulfonation degree, and in comparison to an unmodified electrode it increased by ca. 490% for LS1-modified electrodes and by only 53% for LS2-modified electrodes. The LS-modified electrodes showed high electrocatalytic activity toward oxidation of reduced nicotinamide adenine dinucleotide (NADH). Electrocatalysis was studied in TRIS-HNO(3) buffers having pH of 5.0, 7.5, and 8.5 in the absence and presence of 20 mM Mg(2+), using the rotating disk electrode technique. Determined kinetic constants revealed that the impact of electrocatalysis depended strongly on the pH, the LS sulfonation degree, and the presence of bivalent metal ions. At fixed pH, the observed oxidation rate constant was lower for LS1-based electrodes than for LS2-based electrodes. On the other hand, the relative enhancement of this constant caused by the presence of Mg(2+) ions was much higher for LS1-based electrodes than for LS2-based electrodes. This phenomenon was explained by the participation of sulfonic groups in the formation of a ternary complex between quinone moiety, metal ions, and NADH. The values of other kinetic constants, including the Michaelis-Menten constant (K(M)), suggested that the formation of such a complex is preferred in alkaline pHs.