Substrate Effects of Noble Metal Nanostructures Prepared by Sputtering

Cathode sputtering is a well-established technique for preparation of metal nanostructures. However, the substrate properties are very important in this process. On glass substrates, there is a difficulty with poor adhesion of the metal layers, but thanks to this, metal nanostructures can be produced using solid state dewetting process. Thin metal films on polymer substrates are strongly influenced by the surface properties of the polymers, which originate in the method of their preparation. A recent focus is direct sputtering of metal nanoparticles (NPs) into liquid substrates and their characterizations and applications. Polyethylene glycol (PEG) is one of the most commonly used liquid, which provides “stealth” character to nanostructures. Recent results in this area are reviewed in this chapter. PEGylated NPs could find application in drug delivery systems, therapy, imaging, biosensing, and tissue regeneration

Physicochemical Properties of Gold Nanostructures Deposited on Glass

Properties of gold films sputtered onto borosilicate glass substrate were studied. UV-Vis absorption spectra were used to investigate optical parameters. XRD analysis provided information about the gold crystalline nanostructure, the texture, and lattice parameter and biaxial tension was also determined by the XRD method. The surface morphology was examined by atomic force microscopy (AFM); chemical structure of sputtered gold nanostructures was examined by X-ray photoelectron spectroscopy (ARXPS). The gold crystallites are preferentially [111] oriented on the sputtered samples. Gold deposition leads to dramatic changes in the surface morphology in comparison to pristine glass substrate. Oxygen is not incorporated into the gold layer during gold deposition. Experimental data on lattice parameter were also confirmed by theoretical investigations of nanoclusters using tight-binding potentials

Photochemical Preparation of Silver Colloids in Hydroxypropyl Methylcellulose for Antibacterial Materials with Controlled Release of Silver

Silver nanoparticles (AgNPs) possess strong antibacterial effect. The current trend is to incorporate AgNPs into functional materials that benefit from their bactericidal capabilities. Hydroxypropyl methylcellulose (HPMC) is routinely used for the controlled release of medicine thanks to its slow dissolution in water and could be used as a matrix for the controlled release of AgNPs, if a method to produce such a material without the need of other reactants was developed. We proposed such a method in a photochemical reduction of AgNO3 in hydroxypropyl methylcellulose (HPMC) solutions by the illumination of the mixture with the light emitting diode bulb for about 2 h. These AgNPs were characterized by transmission electron microscopy and their diameter was found to be mostly under 100 nm. The colloids were then easily transformed into solid samples by drying, lyophilization and spin-coating. The slowly soluble HPMC was found to be able to release the AgNPs gradually over the duration of several hours. Antibacterial activity of the prepared colloids and the solid samples was tested against Escherichia coli and Staphylococcus epidermidis and was found to be very high, reaching the total elimination of the bacteria in the studied systems

Stability and biological response of PEGylated gold nanoparticles

Stability and cytotoxicity of PEGylated Au NPs is crucial for biomedical application. In this study, we have focused on thermal stability of PEGylated Au NPs at 4 and 37 °C and after sterilization in autoclave. Gold nanoparticles were prepared by direct sputtering of gold into PEG and PEG-NH2. Transmission electron microscopy revealed that NPs exhibit a spherical shape with average dimensions 3.8 nm for both AuNP_PEG and AuNP_PEG-NH2. The single LSPR band at wavelength of 509 nm also confirmed presence of spherical Au NPs in both cases. Moreover, according to UV–Vis spectra, the Au NPs were overall stable during aging or thermal stressing and even after sterilization in autoclave. Based on gel electrophoresis results, the higher density of functionalizing ligands and the higher stability is assumed on AuNP_PEG-NH2. Changes in concentration of gold did not occur after thermal stress or with aging. pH values have to be adjusted to be suitable for bioapplications – original pH values are either too alkaline (AuNP_PEG-NH2, pH 10) or too acidic (AuNP_PEG, pH 5). Cytotoxicity was tested on human osteoblasts and fibroblasts. Overall, both Au NPs have shown good cytocompatibility either freshly prepared or even after Au NPs′ sterilization in the autoclave. Prepared Au NP dispersions were also examined for their antiviral activity, however no significant effect was observed. We have synthesized highly stable, non-cytotoxic PEGylated Au NPs, which are ready for preclinical testing