Disposable Nafion-Coated Single-Walled Carbon Nanotube Test Strip for Electrochemical Quantitative Determination of Acetaminophen in a Finger-Prick Whole Blood Sample.

A disposable electrochemical test strip for the quantitative point-of-care (POC) determination of acetaminophen (paracetamol) in plasma and finger-prick whole blood was fabricated. The industrially scalable dry transfer process of single-walled carbon nanotubes (SWCNTs) and screen printing of silver were combined to produce integrated electrochemical test strips. Nafion coating stabilized the potential of the Ag reference electrode and enabled the selective detection in spiked plasma as well as in whole blood samples. The test strips were able to detect acetaminophen in small 40 µL samples with a detection limit of 0.8 µM and a wide linear range from 1 µM to 2 mM, well within the required clinical range. After a simple 1:1 dilution of plasma and whole blood, a quantitative detection with good recoveries of 79% in plasma and 74% in whole blood was achieved. These results strongly indicate that these electrodes can be used directly to determine the unbound acetaminophen fraction without the need for any additional steps. The developed test strip shows promise as a rapid and simple POC quantitative acetaminophen assay.

Effect of Surface Wear on Corrosion Protection of Steel by CrN Coatings Sealed with Atomic Layer Deposition.

Corrosion protection of steel obtained with physical vapor deposition (PVD) coatings can be further improved by sealing the intrinsic pinholes with atomic layer deposition (ALD) coatings. In this work, the effect of surface wear on corrosion protection obtained by a hybrid PVD CrN/ALD Al2O3/TiO2 nanolaminate coating was studied. The samples were investigated by alternating surface wear steps and exposure to salt solution and consecutively the progression of corrosion after each wear and each corrosion step was evaluated. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy showed that the rust spots were almost exclusively located on positions at which the wear steps had removed the top surface of the PVD CrN coating. Nevertheless, even after complete removal of the ALD nanolaminate from the top of the CrN surface by sandpaper grinding, the corrosion current density was less than half compared to the PVD CrN coating alone without surface wear. Cross-sectional SEM images obtained with focused ion beam milling showed not only the presence of the ALD coating at the CrN defects but also the opening of new pathways for the corrosion to attack the substrate. A mechanism for the effect of wear on the structure and corrosion protection of hybrid PVD/ALD coatings is proposed on the basis of this investigation.

Fabrication of dual-type nanowire arrays on a single substrate.

A novel method for fabricating dual-type nanowire (NW) arrays is presented. Two growth steps, selective-area epitaxy (SAE) in the first step and vapor-liquid-solid (VLS) in the second step, are used to grow two types of NWs on the same GaAs substrate. Different precursors can be used for the growth steps, resulting in sophisticated compositional control, as demonstrated for side-by-side grown GaAs and InP NWs. It was found that parasitic growth occurs on the NWs already present on the substrate during the second growth step and that the SAE NWs shadow the growth of the VLS NWs. Optical reflectance measurements revealed the dual-type array having improved light trapping properties compared to single-type arrays. Dual-type NW arrays could be practical for thermoelectric generation, photovoltaics and sensing where composition control of side-by-side NWs and complex configurations are beneficial.