V 750

Example 4

Photocatalytic Activity

The photocatalytic activity of zinc oxide nanoflowers and nanospheres was evaluated through the photocatalytic degradation of methyl orange under UV light irradiation for 120 min using a xenon lamp (300 W) as the light source. In each experiment, 10 mg, 30 mg, and 50 mg of catalyst (zinc oxide nanoflowers or nanospheres) was dispersed in 100 mL of an aqueous solution of methyl orange dye, the dye having a concentration of 10 mg/L. In order to ensure the adsorption-desorption equilibrium between catalyst and dye, the solution was stirred in the dark for 1 h before irradiating with the xenon lamp. At 15 min time intervals, 4 mL samples of the suspension were collected and centrifuged to remove the zinc oxide nanoflowers or nanospheres, and the concentration of dye in the supernatant was assessed with a UV-Visible spectrophotometer (JASCO V-750) by measuring the absorbance at 465 nm. The change in 200-800 nm absorbance over time is shown in FIGS. 10 and 11. The degradation efficiency was calculated as:
Degradation efficiency (%)=(C₀−C)/C₀×100%,where C₀ is the initial concentration of the methyl orange dye, and C is the time-dependent concentration of methyl orange upon irradiation. The change in degradation efficiency over time is shown in FIGS. 6-9.

Example 3

Physical Characterization

The morphologies of the zinc oxide nanoflowers and nanospheres were examined by scanning electron microscopy (SEM, FEI INSPECT S50), as shown in FIGS. 2A-2B and FIGS. 3A-3B, respectively. The crystallinity and crystal phases of the zinc oxide nanoflowers or nanospheres were studied by an X-ray diffractometer (XRD Rigaku, Japan) using Cu-Kα radiation (λ=1.5418 {acute over (Å)}) in the range of 10°-80° with 1°/min scanning speed. The XRD patterns for both nanoflowers and nanospheres arc shown in FIG. 1. UV-Vis diffuse reflectance spectra of zinc oxide nanoflowers and nanospheres, as shown in FIG. 4, were recorded on a diffuse reflectance UV-Vis spectrophotometer (JASCO V-750). Micromeritics ASAP 2020 PLUS nitrogen adsorption apparatus (USA) was employed for BET surface area determination. Before surface area analysis, samples were degassed at 180° C., and the surface area was then determined using N₂ adsorption data in the relative pressure (P/P₀) range of 0.05-0.3, as shown in FIG. 5. The BET surface area of zinc oxide nanoflowers was observed as 22.54 m²/g (pore size: 22.92 nm; pore volume 0.1291 cm³/g) while for nanospheres, the surface area was 9.51 m²/g (pore size: 30.74 nm; pore volume 0.0780 cm³/g).