摘要： Chemical functionalization of nanomaterials is important to control their physical properties. Since their applications frequently require the homogeneity in the physical properties of the components, many precise functionalization methods for nanomaterials have been developed in view of their applications from electronics and optics to biomedicine. Nanomedicine has been attracting growing interest in terms of therapy and diagnosis, or so called theranostics. In the field, nanomaterials play a key role and hence they are chemically functionalized frequently to meet the requirements for the purpose. In the nanomaterial‐based drug delivery system (DDS), for example, the following functions are required: the nanodrug has to disperse well in the blood to avoid embolism; circulate throughout the body to avoid leaking from the pores in the blood vessel and trapping in the reticuloendothelial system; accumulate in the targeting organ or tissue; and finally, release the loaded drug. Among the nanomaterials in the DDS, carbon nanomaterials have the following characteristic properties: (i) basically inert, but functionizable at the functional groups such as carboxylic and hydroxyl ones on the surface, edge, and defect through organic transformation; (ii) variety of options in terms of shapes including zero‐dimensional (0D, fullerenes), one‐dimensional (1D, carbon nanotubes, CNTs), two‐dimensional (2D, graphene, G), and three‐dimensional (3D, nanodiamond, ND); (iii) commercially available; and (iv) fluorescence emission from semiconducting SWNTs, relatively small size graphenes and color center in ND. The carbon nanomaterials discussed in this chapter are graphene (Section 10.2) and ND (Sections 10.3 and 10.4). Graphene has a flat and hydrophobic surface consisting of sp2 carbons. It exhibits high affinity to the flat molecules, including π‐electrons such as triphenylene, as we reported quite recently. Therefore, it has been utilized as carrier for anti‐cancer drugs with flat and hydrophobic properties. In addition, it can work as photosensitizer in photothermal therapy, making it more fascinating as a bifunctional material in cancer therapy. However, the graphene‐based carriers that have been used so far are graphene oxide (GO), because the carrier is required to have sufficient dispersibility in a physiological environment. The direct use of pristine graphene as a drug carrier, which will be described below, is the first example, as far as we know. On the other hand, ND has been reported to be low toxicity or even nontoxic nanomaterial. It is composed of the curved surface and core, not the flat surface and edge for graphene. As in the case of edge and defect in graphene, the ND surface is covered with various functional groups such as carboxylic and hydroxyl groups. Although ND is categorized as an inorganic nanomaterial due to its robustness and chemical stability, the surface functionalities impart the organic characteristics to ND, enabling the control of the physical property by controlling the surface functionality. Recently, surface chemical functionalization of ND has been actively investigated in view of its applications. In this chapter (Sections 10.3 and 10.4), chemical functionalization on ND for drug carrier will be described; the requisite functions of aqueous dispersibility, targeting specificity, and cytotoxicity are imparted to ND through stepwise surface chemical functionalization. This chapter covers synthesis, characterization, and evaluation of the following three nanodrugs: chlorin e6 (Ce6)‐loaded graphene for cancer phototherapy; Pt drug‐loaded nanodiamond for cancer chemotherapy; and DNA‐loaded nanodiamond for gene therapy.