## 3 Results and Discussion
### Photocatalytic Activity  
The photocatalytic performance of CdS, Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanoflowers and P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposite is assessed by the degradation of Rh-B molecules under visible light irradiation, as shown in Figure 5. All of the experiments are carried out under the similar conditions or otherwise mentioned. The Rh-B concentrations (C\({}_{0}\)) are determined from its absorption peak at 553 nm, and 80 mg of the catalysts are used. The reaction mixture containing the photocatalysts and Rh-B is stirred in dark for 30 min prior to the light irradiation, to establish the adsorption-desorption equilibrium between the  
Figure 4: High resolution X-ray photoelectron spectra (XPS) of pure CdS nanoparticles and P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposite (1-5), (a) survey spectra, (b) Cd 3d, (c) S 2p, (d) Ti 2p, (e) O 1s, and (f) Zn 2p.  
Rh-B and the photocatalysts. It can be clearly seen that the sample of P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposite with P25:Cd ratio of 1:5 shows a strong adsorption ability towards the Rh-B with the adsorption up to 65% in dark, which is higher than those of the samples of pure CdS (25%) and Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanoflowers (32%). The adsorption capacity of nanocomposite materials depends on the crystallinity, the phase alignment and the surface area [43], thus the high adsorption performance of P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposite with P25:Cd ratio of 1:5 can be attributed to its high surface area as compared to the pure CdS and Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanoflowers. After the absorption process, the photocatalytic degradation activities of the samples are investigated, and the results show that all of the samples have the high efficiency for degradation Rh-B under visible light irritations. The P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposite with P25:Cd ratio of 1:5 shows the highest activity for the degradation of Rh-B and it takes about 60 min to completely degrade Rh-B, while the activities for degradation of Rh-B take about 180 min, 150 min, 120 min and 150 min in case of pure CdS, Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanoflowers, P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S 1-10 and P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S 1-3, respectively (Figure 5a). In order to minimize the impact of the physical adsorption on the photo-degradation, the photocatalysts amount is changed from 80 mg to 50 mg. Then, the photocatalytic degradation activities of the samples are investigated, all of the samples show better photocatalytic activities than pure CdS. The P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S with P25:Cd ratio of 1:5 also shows the best performance towards Rh-B degradation and it could be completely degraded within 60 min of photoirradiation, as shown in Figure 5b. It is obvious from the results that under visible light irradiation, P25/Zn\({}_{0.15}\)Cd\({}_{0.85}\)S nanocomposites possess efficient separation of hole and electron, which would enhance the photo-degradation of dye. The results reveal that the photocatalytic ability of CdS nanoparticles towards degradation Rh-B is greatly enhanced after doping with Zn and decoration with P25, this could be due to the reason that the Zn doped CdS surface will create the flower-like structure with many small particles, which may favor the enhanced light absorption ability, as well as the fast electron transfer to avoid the recombination of the photo-induced electrons and holes between CdS and P25.