## 11 Nanotechnology for Sustainable Environment, Agriculture and Food Safety
### Effects of Urea Coated with Zinc Oxide Nanoparticles on Tomato Plants in Greenhouse  
[PERSON] 1, [PERSON] 2, [PERSON] 2, [PERSON] 3 and [PERSON] 2,3,4,5  
1 Burnett Honors College, University of Central Florida, Orlando, FL 32826, USA  
2 Departments of Chemistry, University of Central Florida, Orlando, FL 32826, USA  
3 NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA  
4 Burnett School of Biomedical Science, University of Central Florida, Orlando, FL 32826, USA  
5 Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USAZinc (Zn) is a micronutrient vital for plant function and structure. Deficiency of this micronutrient will not only lead to nutrient quality and yield decrease but can also lead to pH change and pathogen susceptibility. Due to their reliance on plants for nutrients, many cases of Zn deficiency in people in developing countries in South East Asia and Sub-Saharan Africa exhibit growth retardation, immunology and cognitive problems, and even pregnancy complications as well as congenital disabilities. Zinc oxide (ZnO) nanoparticles were prepared with different combinations of two capping agents (sodium salicate (SAL), n-acetyl cysteine (NAC), and urea) in order to improve ZnO solubility and Zn bioavailability in soil. Then, these nanoparticles were used to coat urea granules. A Greenhouse experiment was carried out to compare the effects of urea coated with different ZnO nanoparticles on the phenotypic development of tomato plants against those controls (bulk ZnO, no zinc, and no urea and zinc). A seed germination experiment also was conducted to test the effects of ZnO nanoparticles on the rate of seed germination and root length. The study found that tomato plants treated with urea coated with NAC-SAL ZnO nanoparticles showed a higher number of leaves and number of fruits set compared to controls. For the seed germination experiment, NAC-SAL ZnO nanoparticles also improved the number of germinated seeds and the root elongation in respect to the controls. Therefore, dual capped ZnO nanoparticles have great potential for application in agriculture. Interaction of Salicylate with Zinc Oxide Nanoparticle: Combined Reactive Force Field Molecular Dynamics and Density Functional Study  
[PERSON], [PERSON] and [PERSON]  
Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA  
Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA  
Capping agents are often employed to control the nanoparticles' size and aggregation and to tailor their properties. Mechanistic insights into the interaction between nanoparticles and capping agents can be used to guide the design of improved nanomaterials. Here, we employ density functional theory (DFT) and reactive force-field molecular dynamics (ReaxFF MD) simulations to study the interaction between zinc oxide (ZnO) nanoparticle and salicate, a capping agent. We find that salicate strongly interacts with ZnO through the formation of chemical bonds between O atoms of salicate and surface Zn atoms, and that the resulting interface becomes a part of a distorted, hexagonal-type structure. At very reactive Zn sites, which are near to very active O atoms having localized O 2p electronic states near Fermi level [1], the salicate undergoes dissociative adsorption. Our combined ReaxFF MD and DFT simulations indicate that there is a delicate interplay between concentrations of salicate and water for a decisive role of salicate to control the nanoparticles' growth and agglomeration in aqueous solution. From frequency analysis, we find that C=O stretching mode of salicate softens upon its adsorption. The interaction also leads to the shifting of the ZnO's Fermi energy, and such shift is facilitated by the charge transfer.