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The goal of this work is to study the antibacterial activity of acrylic polymer/ZnO–Ag nanocomposite coating. First, in the presence of UV light ($\lambda =253.7$ nm), Ag nanoparticles (NPs; derived from AgNO₃ precursor) were photoreduced and deposited on the surface of nano-ZnO. Field emission scanning electron microscope (FE-SEM) images indicated that the AgNPs (5–15 nm) were deposited on the surface of nano-ZnO (20–40 nm). These ZnO–Ag nanohybrids (0.1–0.2 wt.%) were incorporated into the acrylic polymer matrix using ultrasonication to form the nanocomposite coating ($\sim 25$$\mu$m thick). Nano-ZnO hybridized with AgNPs resulted in a decrease in the energy gap ($E_g)$ of ZnO from 3.2 eV to 2.7 eV, as observed by diffused reflectance UV–Vis spectrum analysis. The abrasion resistance test indicated that the incorporation of hybrid NPs enhanced the abrasion resistance of the polymer coating (from 81 to 125 l/mil). Moreover, the polymer nanocomposite coating showed high antibacterial efficacy against $E$. coli and $S$. aureus in antibacterial tests and achieved 1.8 and 1.2 log after 24 h, respectively. These findings endorse that the ZnO–Ag nanohybrid-based water-borne nanocomposite coatings offer exceptional antibacterial efficiency and would be promising in this application.

Drinking colloidal gold as elixir of life is an age-old practice worldwide. A large body of data containing patients' experiences after intake of colloidal gold for long duration would be available in the medical records of hospitals. ZnO has been approved by FDA for topical use and not for oral intake. Drosophila melanogaster (wild type) strains were fed with physiologically relevant concentrations of nano-gold and nano-ZnO along with appropriate controls. Citrate-capped nano-gold (average particle size is 15–20 nm) synthesized by reducing hydrogen tetrachloroaurate with 1% trisodium citrate and custom-made nano-ZnO, purchased from M K Implex, Canada (average particle size 50 nm) were used as treatments. Microarray studies revealed that fly trehalose receptor genes, Tre and Tre1, are both unaffected after nano-gold and nano-ZnO treatment. Gr64 subfamily members (encoding sugar receptors like glucose, sucrose, and maltose), for example, Gr64a-b become downregulated, but Gr64c, Gr64d, Gr64f remain unaltered in case of both the treatments. Among bitter receptor genes, Gr66a is the most well studied and shows significant downregulation by nano-gold and not by nano-ZnO. Ppk11 and Ppk19 are gustatory ion channel genes which modulate salt perception. Ppk11 was found to be downregulated by both nano-gold and nano-ZnO, while ppk19 expression is suppressed by nano-gold treatment but not by nano-ZnO. The effects of these two nanoparticles on pheromone receptors (Gr32a, Gr39a, and Gr68a) and _CO2 receptors (Gr21a and Gr63a) are presented. To the best of our knowledge, this is the first report on the effect of pure nanoparticles on gustation. Data has been analyzed in the light of the age-old tradition of oral administration of the nano-gold viz-a-viz topical use of nano-ZnO. These results would have far reaching implications in the design of nano-gold mediated oral drug delivery of cancer and other drugs as well as nano-ZnO coated drugs/cosmetics and nano-ZnO carrier based drug delivery in skins and in other topical applications.

Studying the thermodynamic properties of the reaction of nanoparticle with organic substance is significant for the application of nanomaterial in organic fields. In this work, by using the reaction of nano-ZnO with different particle sizes with benzoic acid as a research system, the size-dependent standard equilibrium constant and reaction thermodynamic properties were analyzed theoretically, and the influence regularities of the particle size on the standard equilibrium constant and the reaction thermodynamic properties were studied. The excellent agreement between the experimental results and theoretical analysis shows that the particle size has remarkable influence on the standard equilibrium constant and the thermodynamic properties of the reaction; with the decrease of the particle size, the standard equilibrium constant increases, while the standard molar reaction Gibbs energy, the standard molar reaction enthalpy and the standard molar reaction entropy decrease. Furthermore, the logarithm of the standard equilibrium constant and the thermodynamic properties present linear relations with the reciprocal of the particle diameter, respectively. The theory and the influence regularities will provide useful tools to lead better and broader application of nanomaterial in organic fields.