# Polymer-Stabilized Silver (Gold)-Zinc Oxide Nanoheterodimer Structures as Antimicrobials
## 3 Results  
Colloidal nanoheterostructures containing silver (or gold) and zinc oxide were prepared using the one-pot method and were used as potential bactericidal agents (Scheme 1). Maleic acid-containing alternating copolymers with N-vinyl-2-pyrrolidone (VM), ethylene (EM), and styrene (SM) were used as matrices for binding precursor metal ions and stabilizing the resulting nanoparticles. The transformation of metal cations into nanoparticles was carried out by the hydrothermal method in an alkaline medium. For the production ZnO/Ag\({}^{0}\) and ZnO/Au\({}^{0}\) composites, the numbers of entered metal cations in terms of each maleic acid residue in the copolymers were practically equivalent: Zn\({}^{2+}\)/Ag\({}^{+}\) = 0.15/0.3 and Zn\({}^{2+}\)/Au\({}^{3+}\) = 0.23/0.15 (mol/mol). The amount of zinc cations introduced into the composite was limited by the solubility of the polymer salt obtained and depends on the structure of the copolymer used. In addition, this limit turned out to be different for the initial copolymers and polymer complexes containing AgNPs. In the first case, the limit of salt stability is reached when 0.25 mol of zinc cations is introduced onto the copolymer link. When zinc cations are introduced into a solution of silver-containing nanocomplexes, this limit increases, and the ratio reaches 0.5 for VM and SM, and 1.0 for EM. This is due to the different conformation of the initial copolymers and nanocomplexes. In our previous study [85], using the EM copolymer, we showed by diffuse light scattering (DLS) that this copolymer was characterized by a wide and bimodal particle size distribution (hydrodynamic radius, Rh = 50-300 nm, depending on ionic strength and pH) and an intermolecular association. In the study of the complex of this copolymer with EM/Ag\({}^{0}\) silver nanoparticles by DLS, well-formed and narrowly dispersed (Rh = 105 nm) micelles were detected [85]. Simultaneous production of silver (gold) and zinc oxide nanoparticles was recorded by heating an alkaline solution containing noble metal and zinc salts. The course of conversion of metal cations to reaction products was monitored by UV-visible spectra. Metal oxide and noble metal nanoparticles have specific absorption bands in the visible region [86; 87; 88]. Figure 1 shows UV-Vis spectra of reaction products. The broad absorption band at 365-375 nm indicates the presence of ZnO; the peak at 406 nm and the band at 520 nm appeared due to surface plasmon resonance corresponding to the Ag\({}^{0}\) and Au\({}^{0}\) states, respectively. In the presence of copolymer stabilizer VM, Au, and Zn cations under the conditions used, the formation of nanoparticles was almost complete after 2 h. In the case of use of Ag and Zn cations, and the VM copolymer, the reaction was practically completed in 6 h; for EM and SM, the reaction was practically completed after 7 h. Figure S1a-c (Supplementary Materials) shows FTIR spectra of polymer-stabilized heterostructures in comparison with those of the initial copolymers. This method allows you to make sure qualitatively that the preparations contain zinc oxide. The Zn-O stretching mode was observed in the 400-700 cm\({}^{-1}\) range for ZnO crystals [87; 89; 90; 91; 92], so the region of 400-800 cm\({}^{-1}\) is presented in detail. The bands at 625, 624, 551, and 544 cm\({}^{-1}\) are stretching vibrations of Zn-O and Ag-ZnO bonds [87; 89; 90; 91; 92]. TEM micrographs of colloidal solutions of all prepared Au\({}^{0}\)/ZnO and Ag\({}^{0}\)/ZnO composites show relatively monodispersed nanoparticles, predominantly 6-20 nm in size with a shape close to a sphere (Figure 2). The size and shape of the particles shown in the micrographs did not depend on the nature of the polymers used as stabilizers of nanoparticles. Previously, similar images were recorded for heterodimers obtained in a different way [76]. In addition to the TEM, the XRD gives a more detailed qualitative and quantitative composition of the crystal phases of the heterodimers.