Noble Metal Nanoparticles Prepared by Metal Sputtering into Glycerol and their Grafting to Polymer Surface

This chapter summarizes the basic information about elementary characteristics and tech‐ nology of preparation of noble metal nanoparticles. The introduction gives some basic in‐ formation on the history of development in this area, especially in terms of dimensionality of metal nanostructures and their possible applications.The first subsec‐ tion is devoted to the preparation and characterization of Au, Ag, Pt, and Pd nanoparti‐ cles (NPs), which were synthesized by direct metal sputtering in liquid propane-1,2,3,-triole (glycerol). This method provides an interesting alternative to time-consuming, wet- based chemical synthesis techniques. Moreover, the suggested technique allows targeted variation of metal nanoparticle size, which is demonstrated in detail in case of AuNPs by variation of capturing media temperature. Nanoparticle size and shape were studied by transmission electron microscopy and dynamic light scattering. Optical properties of nanoparticle solution were determined by measuring its UV–Vis spectra. Concentration of metal nanoparticles in prepared solutions was determined by atomic absorption spec‐ troscopy. Antibacterial properties were tested against two common pollutants ( Escherichia coli , a Gram-negative bacteria, and Staphylococcus epidermidis , a Gram-positive bacteria). In the presence of Ag nanoparticles, the growth of E. coli and S. epidermidis was complete‐ ly inhibited after 24 h. Any growth inhibition of E. coli was observed neither in the pres‐ ence of “smaller” (4–6 nm, AuNP 4–6 ) nor “bigger” (9–12 nm, AuNP 8–12 ) AuNPs during the whole examination period. AuNP 4–6 , but not AuNP 8–12 , was able to inhibit the growth of. S epidermidis . We also observed significant difference in biological activities of Pt and PdNPs. More specifically, PdNPs exhibited considerable inhibitory potential against both E. coli and S. epidermidis , which was in contrast to ineffective PtNPs. Our results indicate that Ag, Pd, and partially AuNPs have high potential to combat both Gram-positive and Gram-negative bacterial strains.The second subsection describes the effort to anchor met‐ al nanoparticles onto polyethyleneterephthalate (PET) carrier. Two different procedures of grafting of polymeric carrier, activated by plasma treatment, with Au and AgNPs are described. In the first procedure, the PET foil was grafted with biphenyl-4,4’-dithiol (BPD) and subsequently with Au and AgNPs. In the second one, the PET foil was grafted with Au and AgNPs previously coated by the same BPD. X-ray photoelectron spectrosco‐ py, Fourier transform infrared spectroscopy, and electrokinetic analysis were used for characterization of the polymer surface at different modification steps. Au and AgNPs were characterized by UV–Vis spectroscopy. In case of both types of nanoparticles, the first procedure was found to be more effective. It was proved that the BPD was chemical‐ ly bonded to the surface of the plasma-activated PET and it mediates subsequent grafting of the AuNPs. Generally, two major aspects determine whether the growth of NPs during metal sputtering into liquids will take a place rather than formation of thin film on the liquid surface [52]. Firstly, the kinetic energy of sputtered atoms or clusters must be sufficient to penetrate the surface of capturing media. Secondly, the first condition may be fulfilled only in the limited range of media viscosity; thus, the liquid media cannot be too viscous. When those conditions are met, the formation of NPs occurs. Figure 5 shows TEM and HRTEM images of diluted aqueous solutions of Pt and PdNPs. Image analysis of more than 500 particles from 10 different areas of TEM pictures proved that prepared PtNPs and PdNPs have average diameter of (1.7 ± 0.3) nm and (2.4 ± 0.4) nm, respectively. Apparent aggregation of particles is due to the preparation method of samples for TEM (HRTEM) analysis. Observed discrepancy in particle size is probably due to different sputtering yield of both metals (Pt ~ 1.27, Pd ~ 2.09) [87], which is in accordance with supposed growth mechanism causes considerably slower growth of Pt particles (lower concentration gradient). characteristics and technology of preparation of those man-made materials. The introduction gives some basic information on the history of development in this area, especially in terms of dimensionality of metal nanostructures and their possible applications. General overview is supported by the specific research of the author team in this field. Presented findings support the hypothesis that Au, Ag, Pd, and PtNPs can be prepared in a simple and cost-effective manner and are suitable for formulation of new types of bactericidal materials. Presented approach is based on temperature control of capturing media during the sputtering deposition process into propane-1,2,3-triol, allowing targeted variation of NPs size. Bactericidal action of such synthesized NPs was examined against two common pollutants ( E. coli and S. epidermi‐ dis ). While AgNP 4–6 exhibit strong potential to completely inhibit both bacterial strains after 24 h, AuNPs showed pronounced inhibition selectivity regarding the specific NP size. Regardless of AuNP size, any growth inhibition of E. coli was observed. Contrary to that, AuNP 4–6 were able to inhibit the growth of S. epidermidis . We have also illustrated a significant difference in biological activities of Pt and PdNPs. More specifically, PdNPs exhibited considerable inhibitory potential against both E. coli and S. epidermidis , which was in contrast to ineffective PtNPs. Those findings indicate that palladium has high potential to combat both Gram-positive and Gram-negative bacterial strains. Understanding of nanoparticle–bacteria inter‐ actions is a key issue in their potential applications in clinics on everyday basis. Observed discrepancy in bactericidal action between Pt and Pd nanoparticles could be attributed to different size of individual particles. Finally, we have introduced procedures for PET surface coating with noble metal nanoparticles. The techniques were based on activation of PET surface with Ar plasma discharge and consequent application of dithiol as binding reagent between Au and Ag nanoparticles and plasma-treated PET. The introduction of gold and silver nanoparticle–thiol layer on the activated PET surface was confirmed with XPS analysis. Higher concentration of Au and AgNPs was achieved by deposition on PET grafted beforehand with dithiol.