V originále
Electrode materials are the key components of electrochemical sensors and due to diverse structural and morphological forms, carbon material is favored [1-3]. Undoubtedly, pencil leads belong to this category as they represent carbon-based material which is easily available at a very low cost. The aim of this investigation was to study pencil leads branded as “polymer” and to compare them with older types of pencil leads not marketed as “polymer”. Our observations indicate that polymer pencil graphite electrodes (PPeGE) show excellent electron transfer rates for common electrochemical standards and yield the significant improvement in current sensitivity in comparison with conventional graphite electrodes. In addition to electrochemical experiments, the pencil leads were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Good electron transfer properties observed for the best pencil leads are attributed to a unique composition of their surfaces, containing carbon with a low degree of oxidation and silicon monoxide (SiO). The high proportion of carbon (up to 80%) is sp3 hybridized. Advantages of PPeGE material in sensing are demonstrated on the surface quality sensitive assay - stripping analysis of purine derivatives in the absence and presence of Cu(II) ions [4, 5]. Best oxidation signals of both Cu(I)-purine complex and corresponding purine were obtained by using HB grade Tombow and Koh-i-Noor polymer leads.