# Photocatalytic Activity of Monosized AuZnO Composite Nanoparticles
## 4 Conclusions  
In conclusion, we propose a simple method to prepare AuZnO composite nanoparticles coated with PEO-PPO-PEO, which has better photocatalytic efficiency than pure ZnO under appropriate Au loading. The FTIR evaluation showed that PEO-PPO-PEO molecules are present on the surface of the AuZnO composite nanoparticles. The structural and morphological analysis showed that the composite nanoparticles have a narrow particle size distribution and high crystallinity. UV-Vis and PL analyses show that AuZnO composite nanoparticles have good dispersibility and excellent optical properties, which are beneficial for photocatalytic activity. The evaluation of the photocatalytic activity of AuZnO composite nanoparticles of different compositions is achieved by degrading RhB under UV and visible light irradiation conditions, revealing that the AuZnO composite nanoparticles with proper Au loading possess enhanced photocatalytic activity. The photocatalytic activities order of AuZnO composite nanoparticles under both UV and visible light is S3 \(<\) S2 \(<\) S1. Samples S1 and S2 reveal better capability than pure ZnO under UV irradiation, while only S1 shows better capability than ZnO under visible light. The photocatalytic efficiency of the AuZnO composite nanoparticles (S1-S3) was found to be unaltered after three cycles of use under UV irradiation, revealing that the PEO-PPO-PEO-coated AuZnO composite nanoparticles are stable and environmentally friendlier and greener. **Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/9/1/111/s1](http://www.mdpi.com/2076-3417/9/1/111/s1)]([http://www.mdpi.com/2076-3417/9/1/111/s1](http://www.mdpi.com/2076-3417/9/1/111/s1)), Figure S1: TEM image of AuZnO composite nanoparticles (S2), (a) Bright-field TEM, particle size distribution (histogram) with Gaussian function fit (in curve) of the composite nanoparticles, (b) HRTEM of single nanoparticle, (c) Point-detection EDX analysis chart, (d) selected-area electron diffraction pattern of the composite nanoparticles, Figure S2: TEM image of AuZnO composite nanoparticles (S3), (a) Bright-field TEM, particle size distribution (histogram) with Gaussian function fit (in curve) of the composite nanoparticles, (b) HRTEM of single nanoparticle,  
Figure 9: Photocatalytic mechanisms for RhB degradation by AuZnO composite nanoparticles. (**a**) AuZnO composite nanoparticle degradation of RhB under visible light irradiation, and (**b**) AuZnO composite nanoparticle degradation of RhB under UV irradiation. (c) Point-detection EDX analysis chart, (d) selected-area electron diffraction pattern of the composite nanoparticles, Figure S3: TEM image of ZnO nanoparticles, (a) Bright-field TEM, particle size distribution (histogram) with Gaussian function fit (in curve) of the composite nanoparticles, (b) HRTEM of single nanoparticle, Figure S4: Degradation of RhB by AuZnO composite nanoparticles for 3 cycles under UV irradiation (a) S2, (b) S3, Figure S5: XRD patterns for the AuZnO composite nanoparticles, (a) S3 after the cycle test, (b) S3, inverted triangles indicate the positions of Au peaks, and squares indicate the positions of ZnO peaks, Figure S6: TEM elemental mapping analysis of the AuZnO(S1) composite nanoparticles, (a) Bright field imaging, (b) O elemental mapping, (c) Au elemental mapping, (d) Zn elemental mapping, Figure S7: TG-DTA analysis of PEO-PPO-PEO coated AuZnO(S2) composite nanoparticles from 25 to 600 \({}^{\circ}\)C.  
Conceptualization, C.M., X.W., and H.L. ; data curation, C.M., X.W., and S.Z. ; formal analysis, C.M., X.W., S.Z., X.L. ([PERSON]), X.L. ([PERSON]), and H.L. ; investigation, Y.C. ; resources, X.L. ([PERSON]), Y.C. and R.X. ; software, X.L. ([PERSON]); writing-original draft, C.M. and X.W. ; writing-review and editing, H.L. This work was supported in part by the National Natural Science Foundation of China (No. 51172064), and the Key Scientific Research Projects of Henan Province Colleges and Universities, Foundation of Education Department of Henan Province, China (No.