Natural source derived carbon nano-onions as electrode material for sensing applications

Simple synthesis of water soluble carbon nano-onions (CNOs) from lycopene, extracted from tomatoes, and its use as an electrode material for sensing glucose are demonstrated. The carbon onions were synthesized by using extracted lycopene as the starting material and its subsequent treatment with sodium hydroxide, to induce polarity. The yield of purified carbon onions was similar to 29%. These nanomaterials were in the size range of similar to 30-60 nm with an interlayer spacing of 1.5 (+/- 0.1) nm. Taking glucose as a model system, amperometric sensing of the analyte with the synthesized carbon onions and its composite with multi-walled carbon nanotubes (MWNT) have also been tested. The composite was similar to 10 x and similar to 2 x more sensitive in detecting glucose when compared to free carbon onions and nanotube modified electrode surfaces, respectively, under alkaline conditions. Low sensitivity in glucose detection from carbon onion electrode surface could be attributed to the large size of the carbon onions which reduced the surface to volume ratio for effective electrostatic attraction of glucose molecules, and its non-metallic character. The natural source derived unmodified amorphous carbon onions are the first of their kind which served as a useful nanomaterial for sensing analyte important for biological function.