Zetasizer ht

AgNPs were prepared by the reduction of silver nitrate solution with aniline in the presence of CTAB. A series of experiments was performed in which variances were made in the concentrations of oxidant, reductant, and stabilizer in order to obtain a perfectly transparent silver solution. In a typical procedure, 8 mL of a 0.01 mol/dm³ solution of silver nitrate was mixed with 5 mL of a 0.01 mol/dm³ CTAB solution. The colorless reaction mixture slowly converted to the characteristic pale yellow color when 20 mL of a 0.01 mol/dm³ solution of aniline was added in the solution of silver nitrate and CTAB. The total volume of the reaction mixture was always 50 mL. The whole solution had a pH of 10.2. The appearance of color indicated the formation of AgNPs.11
AgNPs were suspended in Milli-Q water at a concentration of 10 mg/10 mL. The stock suspension was probe sonicated at 40 W for 15 minutes. The hydrodynamic size and zeta potential of the suspension of AgNPs in water were measured by dynamic light scattering (Zeta sizer-HT; Malvern Instruments, Malvern, UK). Samples for transmission electron microscopy (TEM) analysis were prepared by drop-coating carbon-coated copper TEM grids with AgNP solution. The films on the TEM grids were allowed to dry prior to measurement. TEM measurements were performed on a JEOL model 2100F instrument operated at an accelerating voltage at 200 kV.

ZnO NPs (<100 nm; 99.7% metal basis; specific surface area, 15–25 m²/g) were purchased from Sigma-Aldrich Co. (St Louis, MO, USA). For scanning electron microscopy (SEM) (S3400N; Hitachi, Tokyo, Japan) analysis, the samples were fixed onto metallic studs with double-sided conductive tape and sputtered with gold. SEM micrographs were analyzed with ImageJ (National Institutes of Health, Bethesda, MD, USA) software to obtain the mean size of pristine ZnO NPs. The hydrodynamic size and zeta potential of ZnO NPs in cell culture medium were determined by dynamic light scattering (DLS) (ZetaSizer-HT; Malvern Instruments, Malvern, UK). The samples of ZnO NPs in powder form were suspended in cell culture medium at a concentration of 1 mg/mL and were sonicated in a water bath at 4°C for 30 minutes at 30 W to form a homogeneous suspension. This stock solution of ZnO NPs was diluted to a 10–100 μg/mL working solution for DLS size measurement.