The sensitivity of gravitational-wave detectors is limited by the mechanical loss associated with the amorphous coatings of the detectors' mirrors. Amorphous silicon has higher refraction index and ...lower mechanical loss than current high-index coatings, but its optical absorption at the wavelength used for the detectors is at present large. The addition of hydrogen to the amorphous silicon network reduces both optical absorption and mechanical loss for films prepared under a range of conditions at all measured wavelengths and temperatures, with a particularly large effect on films grown at room temperature. The uptake of hydrogen is greatest in the films grown at room temperature, but still below 1.5 at.% H, which show an ultralow optical absorption (below 10 ppm) measured at 2000 nm for 500-nm-thick films. These results show that hydrogenation is a promising strategy to reduce both optical absorption and mechanical loss in amorphous silicon, and may enable fabrication of mirror coatings for gravitational-wave detectors with improved sensitivity.
We present the first demonstration of bioelectrodes made from laser-reduced graphene oxide (rGO) on flexible polyethylene terephthalate (PET) substrates that overcome two main issues: using hydrogel ...on skin interface with standard Ag/AgCl bioelectrodes vs. low signal to noise ratio with capacitance or dry electrodes. Today we develop a dry rGO bioelectrode technology with long-term stability for 100 h in harsh environments and when in contact with skin. Reliability tests in different buffer solutions with pH from 4.8 to 9.2 tested over 24 h showed the robustness of rGO electrodes. In terms of signal to noise ratio, our bioelectrodes performance is comparable to that of commercial ones. The bioelectrodes demonstrate an excellent signal to noise ratio, with a signal match of over 98% with respect to state-of-the-art electrodes used as a benchmark. We attribute the unique stability of our bioelectrodes to the rGO/PET interface modification and composite formation during laser processing used for GO reduction. The rGO/PET composite formation assertion is confirmed by mechanical stripping experiments and visual examination of re-exposed PET. The method developed here is simple, cost-effective, maskless, and can be scaled-up, allowing sustainable manufacture of arbitrary-shaped flexible electrodes for biomedical sensors and wearables.
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•Laser-reduced GO is investigated for bioelectronics.•Robust, safe, scalable, and environmentally-friendly GO/PET integration.•Laser processing GO/PET make excellent bioelectrodes for in-vivo applications.•Our electrodes show record performance in comparison to Ag/AgCl.
This paper considers the synthesis of a novel nanocomposite based on reduced graphene oxide and oxidized carbon nanotubes modified with polyaniline and phenol-formaldehyde resin and developed through ...the carbonization of a pristine aerogel. It was tested as an efficient adsorbent to purify aquatic media from toxic Pb(II). Diagnostic assessment of the samples was carried out through X-ray diffractometry, Raman spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and infrared spectroscopy. The carbonized aerogel was found to preserve the carbon framework structure. The sample porosity was estimated through nitrogen adsorption at 77 K. It was found that the carbonized aerogel predominantly represented a mesoporous material having a specific surface area of 315 m
/g. After carbonization, an increase in smaller micropores occurred. According to the electron images, the highly porous structure of the carbonized composite was preserved. The adsorption capacity of the carbonized material was studied for liquid-phase Pb(II) extraction in static mode. The experiment results showed that the maximum Pb(II) adsorption capacity of the carbonized aerogel was 185 mg/g (at pH 6.0). The results of the desorption studies showed a very low desorption rate (0.3%) at pH 6.5 and a rate of about 40% in a strongly acidic medium.
A novel sorption nanocomposite material is synthesized. A method for manufacturing of a nanocomposite based on graphene oxide (GO) modified with a natural sulfo derivative of lignin (lignosulfonate ...(LS)) followed by lyophilization is developed. The modification is aimed at an increase in the sorption capacity of the final material and a decrease in the content of expensive GO. Several variants of the nanocomposite with different contents of the original components are synthesized. The properties of the resulting nanocomposite are studied with the aid of transmission electron microscopy, Raman and IR spectroscopy, X-ray diffraction, and thermogravimetry. The parameters of the porous space were determined using nitrogen adsorption. The sorption capacity of the nanocomposite is assessed using sorption study with extraction of two types of pollutants from aqueous solutions: organic (synthetic dye methylene blue (MB)) and inorganic (lead ions). The adsorption is performed under static conditions in a limited volume. The experimental results show that a GO/LS ratio of 2:1 provides the best sorption capacity with respect to lead ions (179 mg/g) and MB molecules (1822.3 mg/g) at a contact time of 20 min. Thus, the experimental study proves the expediency of manufacturing of the GO/LS nanocomposite as a sorption material for removing of organic and inorganic contaminants.
Abstract
Sensitivity in instruments such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) is limited by a noise originating from fluctuations linked to internal mechanical ...dissipation (IMD) in the amorphous thin films of their Bragg reflectors. We investigate the correlation between IMD, characterized by a loss angle, and the hydrogen concentration in a thin film made of Zr-doped tantalum oxide after annealing at different temperatures. The film was deposited by magnetron sputtering and the loss angle measured by gentle nodal suspension. The concentration of heavier elements was obtained by Rutherford backscattering spectrometry (RBS). The hydrogen concentration in the as-deposited and annealed samples was obtained by elastic recoil detection (ERD). We observe that the hydrogen atomic concentration gradually decreases from 2.0 ± 0.1% down to the detection limit at 0.2 ± 0.1% as we anneal to 650°C. We also find that the loss angle decreases by a factor of two over the same annealing temperature range, suggesting that the loss angle is correlated with the hydrogen concentration. However, the loss angle remains relatively high even when most of the hydrogen is desorbed. We conclude that the presence of hydrogen is not the main limiting factor for further reducing the IMD.
Synopsis We report on the resonant coherent excitation (RCE) of the 2s-2p3 2 transition in Li-like U89+ with an enhanced energy resolution, which was achieved by reducing the projectiles momentum ...spread. The kinetic temperature of the beam was decreased by electron cooling in the ESR, and the collisional momentum broadening in the target was suppressed by the use of thin crystal (1.0 and 2.5 μm-thick). The resonance width was observed to be ∼1.4 eV in FWHM, which is three-times narrower than that from the previous work.
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