## 4 Conclusions  
In summary, we are able to achieve a paint preserving based on ZnO nanoparticles and modified clay. The ZnO/Clay composite formation by a dry dispersion allows obtaining a controlled and uniform surface coating of ZnO. The addition of ZnO nanoparticles improves the antifungal properties of modified clay against a common fungus, _A. niger_. The use of ZnO/Clay composite as a fungicide is in accordance with the established guidelines to find alternatives from natural resources. To evaluate the effectiveness of ZnO/Clay composite as a preservative, we introduce the composite in a waterborne paint matrix. The antifungal test shows the improved response in both fresh and dry paint with the ZnO/Clay composite addition. It is worth noting that the combination of modified clay and ZnO nanoparticles in one preservative composite product and at a low concentration, such as 0.5 wt.%, optimizes the cost production and the amount of material required, besides tolerating the incorporation in other matrixes. Therefore, this composite is a strong candidate for a huge range of applications such as coatings in outdoor environments, the formation of antifungal textile fibers or integration into polymers.  
Figure 4: Antifungal activity test of waterborne paint with 0.5% of ZnO/Clay composite. (**a**) Bauer-Kirby disk diffusion assay of fresh paint (I), fresh paint with ZnO/Clay (II), dry paint (III) and dry paint with ZnO/Clay (IV). Panel (**b**) shows sporulation inhibition diameter data of (I) fresh paint, (II) fresh paint with ZnO/Clay, (III) dry paint and (IV) dry paint with ZnO/Clay. The mean and standard deviation (s.d.) from the three experiments is shown.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/10/4/1322/s1](http://www.mdpi.com/2076-3417/10/4/1322/s1)]([http://www.mdpi.com/2076-3417/10/4/1322/s1](http://www.mdpi.com/2076-3417/10/4/1322/s1)), Supplementary Information 1. Size modification process of the micrometric ZnO via chemical route; Supplementary Information 2. Structural and morphological characterization of the nanoparticulated ZnO; Supplementary Information 3. XRD pattern of modified bentonite clay; Supplementary Information 4. Morphological characterization of inorganic composite precursors; and Supplementary Information 5. Replicas of Bauer-Kirby disk diffusion assay in the paint matrix.  
**Author Contributions:** [PERSON], and [PERSON] conceived the idea and designed the experiments. [PERSON] prepared the samples. [PERSON], and [PERSON] performed the XRD and FE-SEM characterization. [PERSON] performed the HR-TEM characterization. [PERSON] and [PERSON] performed the antifungal activity test. Data processing was carried out by [PERSON], [PERSON], [PERSON], and [PERSON]. All the authors contributed to the discussion of the results [PERSON] and [PERSON] wrote the manuscript with input from [PERSON]. The work was supervised by [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
**Acknowledgments:** This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under the projects MAT2017-86450-C4-1-R, and the Spanish National Research Council (CSIC) under the project NANOMIND CSIC 201560E068. [PERSON] is indebted to MINECO for a \"Ramon y Cajal\" contract (ref: RyC-2015-18626), which is co-financed by the European Social Fund.  
**Conflicts of Interest:** The authors declare the following competing financial interest(s): [PERSON] is an employee of Encapsulae, S.L.