| Nanodiamond (ND), synthesized by explosive detonation, possesses many unique properties of diamond and nanomaterials, thereby exhiting great potential of applications in both traditional and new fields, such as lubrication, polishing, reinforcement, bio-sensing and bio-chips. However, the application of ND is greatly limited as ND aggregates easily to form large particles and loses the properties of nanomaterial. Introduction of functional groups to the surface of ND could not only improve the dispersion of the ND particles, but also could expand the application area of ND. In this paper, various functional groups were introduced onto the ND surface by modification, stable ND colloidal solution was obtained, ND coating and capsule composed of well dispersed ND particles were fabricated, and the anti cancer drug delivery system based on ND was developed. In addition, boron-doped diamond (BDD) has been widely used in electrochemistry such as electrochemical analysis and electrochemical synthesis, as it possesses excellent electrochemical properties. Fluorinated modification of the BDD surface would further improve the properties of BDD, therefore fluorination of BDD surface was also investigated in this paper. The main research is listed as follows:1. Firstly, the structure and basic properties of ND including particle size, structure defects, charged properties, and surface functional groups were investigated; then, based on the surface properties of ND, carboxyl, amino, hydroxyl and other functional groups were introduced onto the ND surface with modification by hydrogen reduction, mixed acid oxidation and silane coupling agents, which facilitated further modification of other groups to improve its performance in applications.2. When dispersed the oxidized ND in water, the particles could be stabilized by the repulsion interaction of the double layers formed by the ionization of the surface groups. Stable ND colloid solution with different particle sizes could be obtained by centrifuging the ND-water suspension at different centrifuging speed. A colloid with the particle size of about 10nm could be prepared with the centrifuging speed of 8000 rpm. A nanodiamond coating was fabricated by self-assembly of ND on amine active glassy carbon, and nanodiamond capsules were prepared by self-assembly of ND on spherical temples. ND particles dispersed well in these two structures, so aggregation of the ND powder could be avoided in the applications. The ND coating and capsules are suitable for carriers of catalyst and bio-moleculars.3. Cis-dichlorodiammineplatinum (II) (CDDP, cisplatin) was successfully loaded onto ND. The release property of the CDDP-ND composite was investigated with dialysis method and the results showed that CDDP was released from the composite in phosphate buffered saline (PBS, pH 6.0) at a rate higher than in PBS (pH 7.4). Therefore, it is predicted that the ND vehicle would delivery low concentration of CDDP in the blood, while release much more drug after integration into the acidic cancer cells, thereby reducing toxic side effects. The complexation between CDDP and the carboxyl groups on the ND surface is responsible for the pH-responsive release property. In addition, the drug released from the composite retains the same cytotoxicity as free CDDP against human cervical cancer cells, HeLa. The above results suggest the possibility of fabrication of new drug delivery systems with ND.4. An easy route was presented for fluorinated modification of BDD surface by electrochemical reaction with perfluorooctanoic acid (PFOA). In the present electrochemical system, PFOA decomposed on BDD anode to generate radicals containing fluorine, which reacted with the BDD surface and then were bonded to the surface. This material may exhibit longer service life, and the poor adsorption of the fluorinated surface suggests interesting applications in electrochemical analysis and synthesis. Furthermore, this easy route may be also suitable for the fluorination of other materials.
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