8. Solubilization and Dispersion of Carbon Allotropes and Their Metal-Complex Composites

Currently, the area of carbon allotropes, in particular nanocarbons, is one of the most developing fields in chemistry and nanotechnology, where carbon nanotubes and graphene are leaders in the number of publications. Taking into account their existing and potential technical, biological, medical applications (in particular for drug delivery purposes), and many others, we note that the main difficulty to integrate such materials into devices and biological systems derives from their lack of solubility in organic and physiological solutions. Functionalization of carbon allotropes with the assistance of biological molecules remarkably improves their solubility in aqueous or organic environment and, thus, facilitates the development of novel biotechnology, biomedicine, and bioengineering. For example, the nanodiamonds (NDs) have got a series of distinct applications in various areas, in particular medicine, electrochemistry and creation of novel materials. Biomedical applications of NDs are well-developed and related with the recently established fact that carbon NDs are much more biocompatible than most other carbon nanomaterials, including carbon blacks, fullerenes, and carbon nanotubes [1]. Their tiny size, large surface area, and ease functionalization with biomolecules make NDs attractive for various biomedical applications both in vitro and in vivo, for instance, for single particle imaging in cells, drug delivery, protein separation, and biosensing [2, 3]. Similarly, water-soluble carbon nanoonions (CNOs) are used for biological imaging [4] and as promising theranostic agents [5].