Characterization of Engineered Nanomaterials

Chemicals such as N-acetylcysteine (NAC) were purchased from Sigma-Aldrich (St. Louis, MO, USA). UV light-responsive pure TiO₂ NPs (Degussa P25; Evonik, Germany) were used as previously described^{12 (link),19 (link),32 (link)}. The crystal structure of P25 TiO₂ was a mixture of 75% anatase and 25% rutile TiO₂. The purity was at least 99.5% TiO₂ and primary particle size was 21 nm ± 10 nm, with a specific surface area of 50 ± 15 m²/g. Carbon-containing TiO₂ NPs [TiO₂(C)] were prepared using a sol–gel method^{19 (link),33 (link)}. The powders were subjected to calcination at 200 °C, and named C200; the detailed preparation of C200 has been reported elsewhere^{19 (link),33 (link)}. By photoreduction process using H₂PtCl₆ and TiO₂ NPs as a platinum precursor and a pristine photocatalyst, respectively, platinum-containing TiO₂ NPs [TiO₂(Pt)] were prepared and characterized following previously described methods^{13 (link),15 (link)}. The NPs of zinc oxide (ZnO; < 40 nm)^{9 (link)} single-walled carbon nanotubes (CNTs), and silicon dioxide (SiO₂; 10–20 nm) were purchased from Sigma–Aldrich. Nanodiamond (ND) NPs, with average sizes of 5 and 100 nm^{9 (link),34 (link),35 (link)}, were purchased from Kay Diamond Products (Boca Raton, FL, USA).