有機染料光分解
Tsai et al. prepared flexible photocatalytic paper comprised of Cu2O and Ag nanoparticle decorated ZnO nanorods. Figure 1a shows photographs of a 10 × 10 cm2 kraft paper and the paper with as-grown ZnO nanorods. Figure 1b is a scanning electron microscopy (SEM) image of the ZnO paper. Figure 1c is a SEM image of the ZnO nanorods. The nanorods have a hexagonal shape with diameters ranging between 50 and 300 nm. SEM images of Cu2O/ZnO, Ag/ZnO, and Ag/Cu2O/ZnO nanorods are shown in Fig. 1 d, e, and f, respectively. A small amount of Cu2O and Ag nanoparticles can be seen on the surfaces of nanorods.
Fig 1. a Photographs of a kraft paper substrate (left) and the paper with as-grown ZnO NRs (right). b SEM images of the ZnO NR paper. c–f SEM images of ZnO, Cu2O/ZnO, Ag/ZnO, and Ag/Cu2O/ZnO NRs, respectively.
Photocatalytic performance was evaluated by degrading a 100 mL, 10 μM (~ 4.8 ppm) RhB solution under the illumination of a 300 W halogen lamp. The employed photocatalytic paper was first immersed in an RhB solution in the dark for 1 h, and a new solution was used for photodegradation. A small motor was employed to stir the solution. A 50 μL drop was taken every 10 min during photodegradation. Absorption spectra of the drops collected at different times were measured with the use of an optical microscope equipped with a fiber-connected Si photodiode array spectrometer.
Fig 2. a, b Absorption spectra of the RhB solution as a function of time (at a 10-min interval) resulting from the photocatalysis of the ZnO and the Ag/Cu2O/ZnO papers, respectively. c Plots of ln(Ct/C0) for the ZnO paper in the dark and the four photocatalytic papers under the light. d Plots of ln(Ct/C0) for the Ag/Cu2O/ZnO paper under the illumination of a halogen lamp and direct sunlight.
In another study, Chiang et al. reported the enhanced photocatalytic activity of ZnO nanowires (NWs) co-modified with Cu2O and Ag nanoparticles (NPs). (Fig. 3)
Fig. 3. SEM images of (a)as-grown, (b) Cu2O NP modified, (c) Ag NP modified, and (d)Cu2O and Ag NPs co-modified ZnO NWs. The insets are enlarged NW images
The photocatalytic activity of the NWs is evaluated by degrading a 50 μM rhodamine B solution under the illumination of a halogen lamp. All NP modified NWs show better efficiencies than as-grown ones and co-modified NWs have the best performance. The zeroth-order kinetic constant of the co-modified NWs is 0.32 μM min-1, which is 3.2 times as high as that of as-grown ones. (Fig. 4)
Fig. 4 Photographs of a photocatalysis experiment by using co-modified ZnO NWs under direct sunlight (a) at the beginning and (b) after 80 min. (c) Concentration ratios as a function of time due to the photocatalysis of co-modified ZnO NWs under a 100 W halogen lamp (same as in Fig. 4) and direct sunlight. The obtained zeroth-order kinetic constants are 0.32 and 0.73 μM min-1, respectively.
抗菌效應
The time-dependent survival ratios of the two samples were also measured. The calculated first-order kinetic constants of the ZnO and CuxO/ZnO samples are 0.084 min–1 and 0.097 min–1 in dark, respectively, and 0.14 min–1 and 0.25 min–1 under light, respectively. With its excellent antibacterial activity, the CuxO/ZnO nanocomposite has good potential for practical applications.
