RESUMO
This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter.
RESUMO
Enhanced antibacterial properties of nanomaterials such as TiO2 nanotubes (TNTs) and silver nanoparticles (AgNPs) have attracted much attention in biomedicine and industry. The antibacterial properties of nanoparticles depend, among others, on the functionalization layer of the nanoparticles. However, the more complex information about the influence of different functionalization layers on antibacterial properties of nanoparticle decorated surfaces is still missing. Here we show the array of â¼50 nm diameter TNTs decorated with â¼50 nm AgNPs having different functionalization layers such as polyvinylpyrrolidone, branched polyethyleneimine, citrate, lipoic acid, and polyethylene glycol. To assess the antibacterial properties, the viability of Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) has been assessed. Our results showed that the functional layer of nanoparticles plays an important role in antibacterial properties and the synergistic effect such nanoparticles and TiO2 nanotubes have had different effects on adhesion and viability of G- and G+ bacteria. These findings could help researchers to optimally design any surfaces to be used as an antibacterial including the implantable titanium biomaterials.
RESUMO
Optofluidic devices combining optics and microfluidics have recently attracted attention for biomolecular analysis due to their high detection sensitivity. Here, we show a silicon chip with tubular microchannels buried inside the substrate featuring temperature gradient (∇T) along the microchannel. We set up an optical fluorescence system consisting of a power-modulated laser light source of 470 nm coupled to the microchannel serving as a light guide via optical fiber. Fluorescence was detected on the other side of the microchannel using a photomultiplier tube connected to an optical fiber via a fluorescein isothiocyanate filter. The PMT output was connected to a lock-in amplifier for signal processing. We performed a melting curve analysis of a short dsDNA - SYBR Green I complex with a known melting temperature (TM) in a flow-through configuration without gradient to verify the functionality of the proposed detection system. We then used the segmented flow configuration and measured the fluorescence amplitude of a droplet exposed to ∇T of ≈ 2.31 °C mm-1, determining the heat transfer time as ≈ 554 ms. The proposed platform can be used as a fast and cost-effective system for performing either MCA of dsDNAs or for measuring protein unfolding for drug-screening applications.