# Polymer-Stabilized Silver (Gold)-Zinc Oxide Nanoheterodimer Structures as Antimicrobials
## 1 Introduction
It should be noted here that ZnO NPs have a minimal impact on human cells and have a highly specific toxicity against planktonic forms of bacteria and biofilms. The mechanism of the bacteriolytic action of ZnO NPs is explained by the formation of ROS, which damages the cell wall of the pathogen [38]. The use of ZnO micro- and nanoparticles in biotechnology, the food industry, and medicine is well known [39; 40; 41]. For example, they are used as a food additive and packaging component to protect against spoilage [42], in remedies for fungal infections or acne [43], and as a wound-healing stimulant that also keeps wounds moist and clean. Zinc cations are less bactericidal but less toxic compared to Ag cations and are also used in biomedicine [24]. Zinc sulfate and chloride are used in dental materials, such as cements, filling and impression materials, and dendrimice pastes [44]. The combination of zinc ions with a cholera vaccine containing a recombinant cholera toxin subunit had a positive effect on the course of both cholera and diarrhea in children [45]. The mechanism of action of ZnO NPs on microbial cells is similar to that of AgNPs. They can also be considered as a source of metal cations, which can be released under physiological conditions. Zinc ions released from ZnO NPs in the acidic environment of lysosomes interact with biomolecules in the bacterial cell, causing its death. Thus, these cations are bioactive, and the apoptosis of pathogen cells is associated with them [46; 47]. Another hypothesis suggests that the death of microbial cells exposed to zinc oxide nanoparticles is due to the breakdown of proteins and lipids by ZnO NPs, which leads to the destruction of bacterial cells due to the leakage of intracellular contents [48]. It is known that zinc ions are essential nutrients for microbial growth [49]. However, under certain conditions, concentrations and combinations with a number of components, zinc cations are able to exhibit an antiviral and antibacterial effect [50; 51; 52]. Therefore, the combination of pyrithione (PT) and Zn\({}^{2+}\) at concentrations of 2 uM Zn\({}^{2+}\) and 2 uM PT inhibits the replication of RNA viruses: poliovirus, influenza virus, and SARS-CoV-2 (coronavirus). Zinc complexes with compounds of the fluoroquinolones such as levofloxacin and ciprofloxacin have higher bactericidal activity against _K. pneumoniae_, _S. aureus_, _E. coli_,and _B. dysenteriae_ than original antibiotics [53; 54]. Zinc-bound vancomycin implements were found to increase activity against bacteria which were resistant to vancomycin itself [55]. A combination of Ag\({}^{+}\) and Zn\({}^{2+}\) ions led to a synergistic antibacterial effect against _E. faecalis_[56]. When combining various antibacterial components, their additive or synergistic complicity is often revealed, which leads to a decrease in the therapeutic dose of the preparation and in some cases, to a cheaper drug due to the introduction of a cheaper bioactive component into the composites [57; 58; 59; 60; 61]. Similar effects were observed when using heterostructures, in particular Ag/ZnO composites. Various complexes based on Ag/ZnO have not only bactericidal [62; 63; 64; 65] but also antiviral [66] activity. As for the ways for obtaining such heterostructures, the one-pot method seems attractive, in which precursors (metal cations) are simultaneously introduced into the reaction system. One-pot syntheses of Au/ZnO hybrids at high temperature in the presence of hexamethylenetetramine, oleylamine, hydrazine hydrate, or in 1-dodecanol have been described previously [67; 68; 69; 70; 71]. Thus, the above-mentioned processes for the formation of Ag(Au)/ZnO heterodimer systems are quite laborious: high temperature and pressure, and a long synthesis time are used. As a rule, when using these methods, spontaneous formation of cluster structures occurs and, as a result, water-insoluble composites are obtained.