Carbon nanostructures may be protected and functionalized using a layer-by-layer method whereby functional groups on the carbon nanostructure surface may be further derivatized to incorporate additional functional moieties. Exemplary moieties include redox mediator molecules, crown ethers, catalysts, boric acids, carbohydrates, oligonucleotides, DNA or RNA aptamers, peptide aptamers, proteins such as enzymes and antibodies, quantum dots and nanoparticles, cells, cell organelles, or other cellular components. The density of functional groups or functional moieties on carbon nanostructure surfaces may also be controlled as well as the degree of surface hydrophilicity of the nanostructure. Carbon nanostructures functionalized using such a layer-by-layer method may be used to disperse, sort, separate and purify carbon nanostructures and may be used as sensing elements such as voltammetric, amperometric, and potentiometric pH sensors or as biometric sensing elements and electrodes and intracorporeal sensors and electrode.
