Jiří Kratochvíl

Fully substituted pyranones via quasi-heterogeneous genuinely ligand-free Migita-Stille coupling of iodoacrylates.

Migita-Stille coupling of (Z)-β-iodoacrylates with (E)-α-stannyl allylic alcohols to furnish 5-alkylidene-4-substituted-5,6-dihydro-2H-pyran-2-ones is efficiently catalyzed by 2% Pd black in DMF, while Pd(PPh3)4 is inactive. Heterogeneous Pd released in solution is most likely responsible for the catalysis. The reaction is applicable to other substrates, without having to resort to ligands, additives, and/or solid support for Pd. The resulting pyranones can be rearranged to fully functionalized pyranones in another single step.

Large-scale Ag nanoislands stabilized by a magnetron-sputtered polytetrafluoroethylene film as substrates for highly sensitive and reproducible surface-enhanced Raman scattering (SERS)

Fabrication of surface-enhanced Raman scattering (SERS) nanostructures with both high sensitivity and spectral reproducibility, which are key requirements for routine SERS quantitative (sensing) applications, is a great challenge. Here we report on the multilayered design of SERS-active substrates formed by uniform Ag nanoislands stabilized by a magnetron-sputtered polytetrafluoroethylene (msPTFE) film of nanometre thickness. The preparation of large scale (∼20 cm2) nanostructures with long (∼months) time stability was fast (∼minutes), cheap and repeatable. SERS performance of our substrates was subsequently improved by step-by-step optimisation of the fabrication procedure and introduction of the additional silver layer, separating the supporting glass from the msPTFE film, which contributed to the total enhancement factor by another order of magnitude. Such substrates provided high SERS sensitivity with a SERS enhancement factor of about 2 orders of magnitude larger than commonly reported in the literature for Ag nanoislands grown directly on glass. The limits of detection were determined as ∼1 × 10−10 M, 1 × 10−7 M and 1 × 10−6 M for testing analytes methylene blue (MB), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)porphyrin (H2TMPyP) and cysteine, respectively. SERS substrates showed excellent spectral reproducibility both across a single substrate and different substrate batches. The relative standard deviation (RSD) of the SERS signal did not exceed 20% for different concentrations of MB and H2TMPyP, respectively. Therefore, Ag nanoislands stabilized by the msPTFE film are due to high sensitivity, stability and excellent spectral reproducibility very promising substrates for SERS biomolecular quantitative (sensing) applications.

Ag/C:F Antibacterial and hydrophobic nanocomposite coatings

Silver-based nanomaterials that exhibit antibacterial character are intensively studied as they represent promising weapon against multi-drug resistant bacteria. Equally important class of materials represent coatings that have highly water repellent nature. Such materials may be used for fabrication of anti-fogging or self-cleaning surfaces. The aim of this study is to combine both of these valuable material characteristics. Antibacterial and highly hydrophobic Ag/C:F nanocomposite films were fabricated by means of gas aggregation source of Ag nanoparticles and sputter deposition of C:F matrix. The nanocomposite coatings had three-layer structure C:F base layer/Ag nanoparticles/C:F top layer. It is shown that the increasing number of Ag nanoparticles in produced coatings leads not only in enhancement of their antibacterial activity, but also causes substantial increase of their hydrophobicity. Under optimized conditions, the coatings are super-hydrophobic with water contact angle equal to 165∘ and are ca...

State-of-the-Art, and Perspectives of, Silver/Plasma Polymer Antibacterial Nanocomposites

Urgent need for innovative and effective antibacterial coatings in different fields seems to have triggered the development of numerous strategies for the production of such materials. As shown in this short overview, plasma based techniques arouse considerable attention that is connected with the possibility to use these techniques for the production of advanced antibacterial Ag/plasma polymer coatings with tailor-made functional properties. In addition, the plasma-based deposition is believed to be well-suited for the production of novel multi-functional or stimuli-responsive antibacterial films.