Preparation of glassy carbon microspheres for use in electrochemical analysis

The article considers a new method for producing glassy carbon microspheres in solutions containing furfuryl alcohol, ethylene glycol, iso-octylphenol decaethylene glycol (OP-10) and sulfuric acid. The morphology of the microspheres is presented, as well as the results of their electrochemical testing in a solution of 0.1 M KCl, 0.005 M K3[Fe(CN)6], 0.005 M K4[Fe(CN)6]. Using a non-contact thermometer, the dependence of the solution temperature during synthesis (the heat released during the polycondensation reaction) on the volume of added acid was established. The polymer microspheres obtained in the solution were washed, dried, and calcined at 900 °C. The obtained materials were investigated using scanning electron microscopy and X-ray fluorescence elemental analysis. The elemental analysis showed that the materials contained about 98 % carbon, as well as less than 2 % potassium, copper, oxygen, sulfur, and iron. Scanning electron microscopy revealed that the microspheres had a regular spherical shape, well-developed surface and a diameter ranging from 0.5 to 10 microns. On the basis of the data summarizing the characteristic sizes of the microspheres determined by dynamic light scattering, the dependences of their sizes on the ratio of reagents during synthesis were constructed. The microspheres were used for preparation of the paste for an electrode with a mass ratio of microspheres : vacuum oil = 80 : 10. This mixture was stirred into a homogeneous paste and stuffed into a tubular electrode with the 3 mm diameter. The peak current and peak potential values of the electrode with pure microspheres were determined using cyclic voltammetry, with addition of barium hexaferrite as an electrochemical catalyst for the best sample. Among the nineteen solutions studied during synthesis, the most promising is the solution containing 100 mL of ethylene glycol, 5 mL of furfuryl alcohol, 5 mL of OP-10, and 50 m> of sulfuric acid.