Effects of ultrasonic treatment on aqueous suspensions of diamond nanopowders

It has been found that ultrasonic treatment of diamond nanopowders contributes to surface cleaning due to the removal of non-diamond carbon and impurities from the surface boundary of nanodiamond grains (from 0.4 and 0.32 % for ASUD-99 and 0.67 and 0.55 % for ASUD 75, respectively). It does not affect the total sorption volume and the values of the specific surface of the studied samples do not change, but it changes the composition of groups on the surface of diamond nanoparticles, which affect its hydrophilicity. In the samples of АSUD-75 after ultrasonic treatment, a redistribution of the ratio of the intensities of valence vibrations of С=О bonds in the lactone (anhydride) group (1742 cm–1) and the quinone (carboxyl) group (1683 cm–1) is observed, which indicates the decay of the lactone ring and its transformation into carbonyl and carboxyl groups. All samples of АSUD-99 have a hydroxyl group O-H (3400 cm−1), which does not change significantly under the influence of ultrasound. This explains the noticeable change in agglomeration for ASUD-75 in contrast to ASUD 99.