Lignin-AuNp modified carbon paste electrodes—Preparation, characterization, and applications

Carbon paste modified electrodes (CPME) were prepared from composites containing lignin or oxidized lignin adsorbed onto graphite, but no voltammetric signal was observed in K4[Fe(CN)6] solutions, probably due to the low conductivity of these composites. Gold nanoparticles were produced on both composites using the reducing properties of the lignin, which was able to reduce Au3+, from HAuCl4 at pH 4.7, although only Au/graphite/lignin(oxi) composite has shown better characteristics to the electrochemical purposes. There were differences in FTIR spectra between lignin and lignin(oxi) and TEM images were used to explain the results. The better composite to prepare CPME was that containing 0.2% of gold and 2.5% of oxidized lignin, with the percentages expressed in relation to the graphite mass, and admitting that the Au3+ reduction, from the HAuCl4 solution, was quantitative. The proportion of 2:1 (w/w) of Au/lignin(oxi)/graphite composite to the mineral oil (nujol) was used to prepare the CPME with catalytic properties toward the oxidation of dopamine and ascorbic acid and reduction of nitrite and iodate in the positive potential range.

Figure optionsDownload as PowerPoint slide