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Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of the TiO2-Ag composite was proved using a methyl orange (MO) solution (c = 10−5 M) and a crude oil emulsion (c = 50 mg·L−1). The TiO2-Ag-coated membrane reduced the MO concentration by 87%, whereas the TiO2-modified membrane reached only a 46% decomposition. The photocatalytic reduction in the chemical oxygen demand of the emulsion was also ~50% higher using the TiO2-Ag-coated membrane compared to that of the TiO2-coated membrane. The photoluminescence measurements demonstrated a reduced electron/hole recombination, achieved by the Ag nanoparticle addition (TiO2-Ag), which also explained the enhanced photocatalytic activity. A significant improvement in the oil separation performance with the TiO2-Ag-coated membrane was also demonstrated: a substantial increase in the flux and flux recovery ratio (up to 92.4%) was achieved, together with a notable reduction in the flux decay ratio and the irreversible filtration resistance. Furthermore, the purification efficiency was also enhanced (achieving 98.5% and 99.9% COD and turbidity reductions, respectively). Contact angle, zeta potential, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements were carried out to explain the results. SEM and AFM images revealed that on the TiO2-Ag-coated membrane, a less aggregated, more continuous, homogeneous, and smoother nanolayer was formed due to the ~50% more negative zeta potential of the TiO2-Ag nanocomposite compared to that of the TiO2. In summary, via Ag addition, a sufficiently hydrophilic, beneficially negatively charged, and homogeneous TiO2-Ag-coated PVDF membrane surface was achieved, which resulted in the presented advantageous filtration properties beyond the photocatalytic activity enhancement. [ABSTRACT FROM AUTHOR]

Antibacterial surfaces have been in the focus of research for years, driven by an unmet clinical need to manage an increasing incidence of implant-associated infections. The use of silver has become a topic of interest because of its proven broad-spectrum antibacterial activity and track record as a coating agent of soft tissue implants and catheters. However, for the time being, the translation of these technological achievements for the improvement of the antibacterial property of hard tissue titanium (Ti) implants remains unsolved. In our study, we focused on the investigation of the photocatalysis mediated antibacterial activity of silver (Ag), and Ti nanoparticles instead of their pharmacological effects. We found that the photosensitisation of commercially pure titanium discs by coating them with an acrylate-based copolymer that embeds coupled Ag/Ti nanoparticles can initiate the photocatalytic decomposition of adsorbed S. salivarius after the irradiation with an ordinary visible light source. The clinical isolate of S. salivarius was characterised with MALDI-TOF mass spectrometer, while the multiplication of the bacteria on the surface of the discs was followed-up by MTT assay. Concerning practical relevance, the infected implant surfaces can be made accessible and irradiated by dental curing units with LED and plasma arc light sources, our research suggests that photocatalytic copolymer coating films may offer a promising solution for the improvement of the antibacterial properties of dental implants. [ABSTRACT FROM AUTHOR]

Nanostructure formation on bulk metals (copper, gold, and silver) by picosecond (FWHM = 10 ps) Nd:YAG laser irradiation was studied aiming at the production of low-reflectivity surfaces. The experiments were performed at two distinct wavelengths (λ = 355 and 1064 nm) using 20 kHz repetition frequency. The fluence was varied in the 1-11 J/cm2 range, while the samples were shot by an average pulse number from 0 to 50 depending on the scanning speed of the applied galvanometric scanner. The reflectivity of the treated surfaces was recorded with a visible near-infrared microspectrometer in the 450-800 nm range. Morphological investigations of the irradiated metal surfaces were performed with scanning electron microscope, which showed that mainly two types of nanostructures can be responsible for the reflectivity decrease depending on the type of the illuminated metal. Finite element modeling was performed to simulate the laser absorption-induced heating of the illuminated samples, which helps in the understanding of the structure formation process. It was found that two main processes take place in the production of micro- and nanostructures on the surface; the ejection and falling back of molten metal droplets, and the back scattering and aggregation of nanoparticles [ABSTRACT FROM AUTHOR]

The influence of experimental conditions (wavelength, liquid environment) on the properties of Ni-Ti nanoparticles generated by nanosecond laser ablation of NiTinol (Shape Memory Alloy) target and the elemental distribution of the irradiated surface were investigated. The studied laser wavelengths were 248 (KrF) and 1064 nm (Q-switched Nd:YAG). Nitinol targets were covered with thin liquid layer of distilled water and ethanol, respectively. The samples were irradiated with various numbers of pulses (500 in case of the investigation of the alloy surface and 20000 for the particle generation) and fluences (2 and 5 J/cm2). The morphology of laser treated NiTi surface and the size of the generated nanoparticles were studied as a function of both the laser ?uence and the type of the applied liquids using scanning electron microscopy (SEM). Element mappings were realized by energy-dispersive X-ray spectroscopy (EDX). Our results clearly show that when using ethanol both the laser treated surface and the generated particles had a relatively homogeneous elemental distribution. However, under distilled water the irradiated surface and the generated particles showed a separated presence of Ni and Ti elements. For the higher fluence, formation of core-shell structured particles were observed in water environment. [ABSTRACT FROM AUTHOR]

Our aim was to produce metal-wire grating polarizers by a simple two-step method. First, fused silica surface relief gratings were generated by two-beam interferometric laser-induced backside wet etching (TWIN-LIBWE) technique. The grating period was varied from 150 nm to 860 nm (p=150, 280, 460, 860 nm) by the changing of the incident angle of interfering beams. In the second step the gratings were selectively evaporated by thin silver (Ag) film using near grazing incidence (80°) arrangement to produce narrow metal wires. The thickness of metal film was 30±5 nm. The morphology of fabricated metal-wire structures were studied by scanning electron microscopy. The polarizers were tested in infrared wavelength range (λ=1532 nm). According to our measurements, the polarisation contrast of 280 nm period structures was 1:10 for TE:TM transmitted modes. In this case the filling factor of metallic stripes are close to 0.7. [ABSTRACT FROM AUTHOR]