Sodium Borohydride Modified Nanodiamond

As a promising new type of carbon nanometer materials,nanodiamond(ND)has attracted wide attention in various fields,due to their biocompatibility,small size,low toxicity,strong surface adsorption capacity,fluorescence effect and abrasion resistance.Nanodiamonds are synthesized by various techniques,including detonation,chemical vapor deposition,high-pressure high-temperature,etc.,as detonation method,many kinds of groups and some impurities were exposed on the surface of nanodiamond.In order to remove these impurities,improve the dispersion stability of nanodiamonds,and expand the application field of nanodiamond,the surface modification of nanodiamond was urgent.The agglomerated state existed,because of its high specific surface area and high surface activity.It would have difficulties in practical application,if this phenomenon was not figure out.Therefore,the long-term goal of nanodiamond is to make its surface groups homogeneous.The surface functional groups of nanodiamond are generally modified by chemical modification,so as to provide more possibilities for its future applications.The surface of the nanodiamond is modified as reduced nanodiamond,which can make its dispersion in solvent more stable,so that the reduced nanodiamond can be better applied to other fields.In this paper,surface-reduced nanodiamond was prepared by sodium borohydride using mechanical-chemical method.The orthogonal experiment was designed by changing the grinding time,the mass ratio of nanodiamond to reducing reagent,grinding medium ratio,grinding speed and the ball to material ratio.The experimental scheme of optimal mechanical-chemical modification was obtained:grinding time is 2h,the ratio of reducing reagent is 1:1,the ratio of grinding medium is 1:5,the grinding speed is 580rpm,the ratio of ball to material is 1:100,the surface carboxyl content of nanodiamond obtained by the optimal scheme decreased from 447.3?mol/g to 189.6 ?mol/g,and the yield of reduced nanodiamond was over 90%.First,the detonation nanodiamond was purified,and then the nanodiamond was modified by mechanical-chemical modification with sodium borohydride so as to achieve a good dispersion effect.In the mechanical-chemical modification process,the mechanical force gives enough energy to dissociate BH4-from hydrogen ions,hydrogen ions are transferred to the carbonyl carbon atom,and BH3 reacts with the carbonyl oxygen anion to reduce the carbonyl group.The surface structure of nanodiamond before and after reduction were analyzed by infrared spectroscopy.The dispersion properties of nanodiamond before and after reduction were analyzed by particle size test and zeta potential test.The comparative nanodiamond of chemical modification and mechanical-chemical modification were compared and analyzed.The factors of mechanical-chemical modification were analyzed.The effects of various factors on the reduction of nanodiamond were investigated.Under the optimal conditions,the colloidal dispersion of the reduced nanodiamond in the aqueous phase has a minimum particle size of 34.45 nm and it can be stably stored for more than three months.After drying,the reduced nanodiamond powder can be redispersed into water,DMSO,DMF,ethylene glycol and other solvents.