Marcin Holdynski

Graphene Oxide vs. Reduced Graphene Oxide as saturable absorbers for Er-doped passively mode-locked fiber laser

In this work we demonstrate comprehensive studies on graphene oxide (GO) and reduced graphene oxide (rGO) based saturable absorbers (SA) for mode-locking of Er-doped fiber lasers. The paper describes the fabrication process of both saturable absorbers and detailed comparison of their parameters. Our results show, that there is no significant difference in the laser performance between the investigated SA. Both provided stable, mode-locked operation with sub-400 fs soliton pulses and more than 9 nm optical bandwidth at 1560 nm center wavelength. It has been shown that GO might be successfully used as an efficient SA without the need of its reduction to rGO. Taking into account simpler manufacturing technology and the possibility of mass production, GO seems to be a good candidate as a cost-effective material for saturable absorbers for Er-doped fiber lasers.

Morphology of TiO2 nanotubes revealed through electron tomography

In this work, scanning-transmission electron microscopy (STEM) tomography was successfully applied to characterize the three-dimensional structure of titanium oxide nanotubes prepared by the electrochemical anodization of the Ti substrate. The results provided detailed information about the morphology of nanotubes as well as insight into their growth. The segmentation of reconstructed images made it possible to estimate the surface area and volume of the nanotubes. The highest specific surface area was obtained for the lowest anodization voltage of 10V, and corresponds closely to that obtained using the porosimetry technique.

Influence of the silver deposition method on the activity of platforms for chemometric surface-enhanced Raman scattering measurements: Silver films on ZrO2 nanopore arrays

Deposition of plazmonic metal nanoparticles on nanostructured oxide templates is an important part in preparation and design of suitable substrates for surface-enhanced Raman scattering (SERS) measurements. In this contribution we analyze the influence of the Ag deposition methods (magnetron sputtering and evaporation in vacuum, which are often used interchangeably) on SERS activity of the resultant Ag-n/ZrO2/Zr composite samples fabricated. We found that deposition of the same amount of Ag (0.020mg/cm2) on the ZrO2 nanoporous layers using magnetron sputtering and evaporation in vacuum leads to formation of two different surface morphologies, which can be distinguished on the basis of high-resolution scanning electron microscopy (HR-SEM) measurements. Those differences distinctly affect SERS intensity measured for probe molecules: pyridine and sodium 2-mercaptoethanesulfonate. SERS substrates obtained using evaporation technique are ca. 1.5 times more efficient than substrates prepared using magnetron sputtering.

VO2/TiO2 bilayer films for energy efficient windows with multifunctional properties

Vanadium dioxide/titanium dioxide bilayer films have been investigated as a thermochromic coating for application as intelligent window glazings for buildings. The nanostructured VO2 and TiO2 films were deposited on fluorine doped tin oxide coated glass substrates using electric field assisted aerosol assisted chemical vapour deposition (ElFi-AACVD) and sol–gel spin coating, respectively. Their thermochromic properties were investigated using scanning electron microscopy, X-ray diffraction, variable temperature UV/Vis/NIR and X-ray photoelectron spectroscopies. Compared to bare VO2 films, the VO2/TiO2 bilayer films exhibit an increase in visible light transmittance of up to 30%, an increase in integrated luminous transmittance, with values up to 66%, and a higher transmittance modulation in the near infrared of up to 20% at the thermochromic transition temperature. The TiO2 top layer not only enhances visible light transmittance, but also serves to protect the VO2 bottom layer from oxidation. The bilayer films are shown to exhibit photo-induced super-hydrophilicity. These properties are affected by the morphology of the VO2 under-layer.

Metal TiO2 Nanotube Layers for the Treatment of Dental Implant Infections

Titanium oxide nanotube layers with silver and zinc nanoparticles are attracting increasing attention in the design of bone and dental implants due to their antimicrobial potential and their ability to control host cell adhesion, growth, and differentiation. However, recent reports indicate that the etiology of dental infections is more complex than has been previously considered. Therefore, the antimicrobial potential of dental implants should be evaluated against at least several different microorganisms cooperating in human mouth colonization. In this study, Ag and Zn nanoparticles incorporated into titanium oxide nanotubular layers were studied with regard to how they affect Candida albicans, Candida parapsilosis, and Streptococcus mutans. Layers of titanium oxide nanotubes with an average diameter of 110 nm were fabricated by electrochemical anodization, annealed at 650 °C, and modified with approx. 5 wt % Ag or Zn nanoparticles. The surfaces were examined with the scanning electron microscopy-energy dispersive X-ray analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy techniques and subjected to evaluation of microbial-killing and microbial adhesion-inhibiting potency. In a 1.5 h long adhesion test, the samples were found more effective toward yeast strains than toward S. mutans. In a release-killing test, the microorganisms were almost completely eliminated by the samples, either within 3 h of contact (for S. mutans) or 24 h of contact (for both yeast strains). Although further improvement is advisable, it seems that Ag and Zn nanoparticles incorporated into TiO2 nanotubular surfaces provide a powerful tool for reducing the incidence of bone implant infections. Their high bidirectional activity (against both Candida species and S. mutans) makes the layers tested particularly promising for the design of dental implants.