Pristine nanodiamonds (NDs) obtained by detonation, or functionalized by different treatments, namely oxidation, hydrogenation and amination, were used to synthesize composites by insertion in TiO₂ matrixes. The different treatments of the NDs lead to materials containing diverse texture properties and surface chemistry functionalities, particularly concerning the insertion of nitrogen and oxygen groups. The photocatalytic activity of the prepared composites was evaluated for the oxidative degradation of two water soluble pharmaceuticals – diphenhydramine and amoxicillin – under near-UV/Vis irradiation. The most active photocatalyst in what concerns both pollutants degradation under near-UV/Vis irradiation was the composite containing pristine NDs (NDDT). The photocatalytic performances were dependent on the specific surface area and on the amount of functional groups incorporated over the NDs. The influence of ND in the composites activity is well correlated with the observed photoluminescence quenching of TiO₂, which corresponds to a delay in the recombination rate of charge carriers that benefices the photocatalytic reaction. Scavenging of photogenerated holes and radicals by employing sacrificial hole and radical agents revealed that the holes played the main role on both pollutants degradation under UV/Vis irradiation. Reutilization experiments proved that the ND composites have good stability and reusability.

In this work, the use of nanodiamonds (NDs; 2-10 nm) in the seeding of diamond films grown by chemical vapor deposition (CVD) and in the synthesis of composite TiO₂-nanodiamond photocatalysts is discussed. First, enhanced growth of faceted, nanocrystalline diamond (NCD) films by hot filament CVD at moderate substrate temperature (650°C) and carbon-lean gas chemistry (1.0% CH₄ in H₂) is demonstrated. The enhancement of diamond nucleation and growth on Si substrates is achieved by using a sputter deposition of different metallic (Cr, Nb, Ti, V, and W) nanolayers and an ultrasonic seeding with NDs. We conclude that the kinetics of diamond nucleation in the NCD film growth is determined by the number density of NDs embedded on the nanorough metallic surfaces after ultrasonic pretreatment and by the specific surface chemistry (i.e., carbon diffusivity and carburization) during diamond growth. Second., the synthesis and application of composites based on microdiamonds and NDs for the photocatalytic degradation of diphenhydramine pharmaceutical water pollutant is demonstrated. Micro- A nd nanodiamond powders were combined with TiO₂, varying the carbon phase content and tested as composite photocatalysts under near UV-Vis irradiation. The thus prepared composites exhibited higher photocatalytic activity than the respective bare materials. Best photocatalytic performance was observed in the case of using composites with 15 wt.% of NDs oxidized in air at 703 K.