*6.4. Composites of Nanocellulose and Carbon Black*

Carbon black is a form of paracrystalline carbon, produced industrially by partial combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. Carbon black has a high surface-area-to-volume ratio, though not so high as that of activated carbon. Although it is considered to have low toxicity, the International Agency for Research on Cancer has classified it as possibly carcinogenic to humans. In addition, as a component of environmental pollution, carbon black can cause oxidative damage and an inflammatory reaction, which further mediate genotoxicity, reproductive toxicity, neurotoxicity and diseases of the respiratory and cardiovascular systems [166,167]. Nevertheless, carbon black is currently used as a filler in tires and in other rubber products, and as a pigment in inks, paints and plastics.

Composites of nanocellulose and carbon black have been used mainly for constructing biosensors, particularly wearable sensors for strain and human body motion, e.g., motion of the fingers, the elbow joint and the throat. A strain-sensing device with excellent waterproof, self-cleaning and anticorrosion properties was based on a superhydrophobic electrically conductive paper. This paper fabricated by dip-coating a printing paper into a carbon black/carbon nanotube/methyl cellulose suspension and into a hydrophobic fumed silica suspension [33]. Another strain-sensing device was fabricated by printing carbon black conductive nanostructures on cellulose acetate paper. At the same time, this material had electrochemical properties promising for the detection of hydrogen peroxide [31]. An electrochemical aptasensor for detecting *Staphylococcus aureus*, e.g., in human blood serum, was designed as a nanocomposite of Au nanoparticles, carbon black nanoparticles and cellulose nanofibers, and was endowed with a thiolated specific *S. aureus* aptamer as a sensing element [32].
