The Effect of Co Content and Annealing Temperatures on the Resistivity in Ag-Co Films.

Ag-Co films with ultra-high resistivity were prepared on polyimide by magnetron sputtering. The effect of Co content and annealing temperatures on the resistivity and microstructure of Ag-Co films has been thoroughly investigated and the relation between resistivity and microstructure has been discussed. Results show that thicker Ag-Co films without annealing present lower resistivity due to better crystallinity. However, thin Ag-Co films (≤21 nm) annealed at 360 °C present ultra-high film resistivity because of the formation of diffusion pits on the film surface which blocks the transmission of electrons in films to increase film resistivity. Inversely, the resistivity of thick Ag-Co films (≥45 nm) annealed at 360 °C is much less than that annealed at lower than 260 °C owing to no diffusion pits. Furthermore, the addition of Co inhibits the growth of Ag grains and limits the migration of electrons in Ag-Co films further, also resulting in the increase of Ag-Co films' resistivity.

Development of organic-diffusive gradients in thin films technique for measuring freely dissolved concentrations of tetracyclines using a commercial SPE packing.

The freely dissolved concentrations (FDCs) of pollutants are related to their bioavailability in the environment, and the diffusive gradients in thin films technique (DGT) can obtain the FDC of an analyte. Aiming for the detection of the FDCs of tetracyclines (TCs), we used a polyacrylamide hydrogel comprising acrylamide and acrylaide agarose cross-linker as diffusive and binding gels, and a commercial solid-phase extraction (SPE) packing, namely polymer sorbent (PLS), as an adsorption material in the binding gel for the preparation of the organic-diffusive gradients in thin films (o-DGT) devices. The results showed that the diffusion coefficients of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in the diffusive gels were 1.08 × 10-6, 1.08 × 10-6 and 1.03 × 10-6 cm2/ s at 25 °C, respectively. The binding gel showed excellent performance with adsorption capacities of 534.88-569.42 µg/disc for TC, 527.18-565.98 µg/disc for OTC and 1320.12-1320.86 µg/disc for CTC, respectively. The uptake efficiencies were 94.21-111.12, 71.25-88.44 and 76.10-86.62% for TC, OTC and CTC, respectively, with the TCs concentration of 0.05-10 mg/L. The adsorption kinetics of TCs could be described with a pseudo-second-order model (POSM, R2 >0.97). According to the result of adsorption kinetics, the adsorption rate of TCs in the binding gel was not as fast as that of heavy metals, suggesting that the TCs concentrations at the boundary of binding gels in the o-DGT devices could not decrease to zero. After correction of the boundary concentration, the FDCs accounted for 30.30-56.90, 48.10-64.68 and 16.55-50.16% for TC, OTC and CTC, respectively, while their concentrations ranged from 0.2 to 10.0 mg/L. Our results suggested that SPE packing might be an ideal adsorption material for o-DGT binding gels, and that adsorption kinetics should be corrected when calculating the FDCs of organic pollutants.

Phytoremediation of cadmium contaminated alkaline soil using the ornamental hyperaccumulator Mirabilis jalapa L. enhanced by double harvesting: a field study.

Ornamental hyperaccumulators are considered ideal plants for phytoremediation of cadmium (Cd)-contaminated soils because of their high accumulation capacity and minimal potential to enter the food chain. Aiming to estimate the phytoremediation efficiency and explore the influence of double harvesting, a filed study was carried out in Cd-contaminated alkaline soil using the ornamental hyperaccumulator Mirabilis jalapa L. Seeds of M. jalapa were sawn with spacing in rows of 15 cm and in lines of 20 cm on April 20th. Three treatments with different harvesting strategies were arranged: all plants were harvested once on September 10th (marked with H0), and the plants were harvested on July 20th for the first time at a height above ground of 50 cm and 30 cm (marked with H1 and H2, respectively), and then, they were harvested on September 10th for the second time. The plant samples were digested with a mixture of HNO3 and HClO4 and determined using ICP-MS. The results showed that the total biomass of the shoots increased from 505.81 ± 8.29 g/m2 in the H0 treatment to 849.72 ± 59.73 and 933.14 ± 96.12 g/m2 in the H1 and H2 treatments, respectively, while the total Cd accumulation in the shoots was 42.32 ± 4.44, 52.99 ± 7.32, and 56.30 ± 6.95 g/ha in the H0, H1, and H2 treatments, respectively. Phytoremediation efficiencies increased by at least 20% after the application of double harvesting. However, double harvesting also decreased the translocation and bioconcentration factors with a reduction of 30-55% because the Cd concentration in the shoots was low at the first harvest. Our results suggested that double harvesting is a powerful method to improve phytoremediation efficiency with low costs and minimal risk, and other technologies should be applied together to address the accumulation and translocation of Cd.

Effect of Annealing on the Microstructure and SERS Performance of Mo-48.2% Ag Films.

Mo-48.2% Ag films were fabricated by direct current (DC) magnetron sputtering and annealed in an argon atmosphere. The effects of annealing on the surface morphology, resistivity and surface-enhanced Raman scattering (SERS) performance of Mo-48.2% Ag films were investigated. Results show a mass of polyhedral Ag particles grown on the annealed Mo-48.2% Ag films' surface, which are different from that of as-deposited Mo-Ag film. Moreover, the thickness and the resistivity of Mo-48.2% Ag films gradually decrease as the annealing temperature increases. Furthermore, finite-difference time-domain (FDTD) simulations proved that the re-deposition Ag layer increases the "hot spots" between adjacent Ag nanoparticles, thereby greatly enhancing the local electromagnetic (EM) field. The Ag layer/annealed Mo-48.2% Ag films can identify crystal violet (CV) with concentration lower than 5 × 10-10 M (1 mol/L = 1 M), which indicated that this novel type of particles/films can be applied as ultrasensitive SERS substrates.

Discrepancies in the Microstructures of Annealed Cu-Zr Bulk Alloy and Cu-Zr Alloy Films.

Copper-zirconium bulk alloy and Cu-Zr alloy films are prepared by vacuum smelting and magnetron sputtering, respectively, and subsequently annealing is conducted. Results show that Cu-Zr bulk alloy and alloy films exhibit significantly different microstructure evolution behaviors after annealing due to different microstructures and residual stress states. CuxZr alloy compounds disperse at the grain boundary of Cu grains in as-cast and annealed Cu-Zr bulk alloys. However, unlike bulk alloys, a large number of polyhedral Cu particles are formed on the Cu-Zr thin films' surface upon thermal annealing. Kinetically, the residual compressive stress in the Cu-Zr films promotes the formation of Cu particles. The influencing factors and the path for mass transport in the formation of the particles are discussed. The large-specific surface area particles/film composite structure has potential applications in Surface-Enhanced Raman Scattering, catalysis, and other fields.

A bilinear pairing based anonymous authentication scheme in wireless body area networks for mHealth.

Wireless body area networks (WBANs) have become one of the key components of mobile health (mHealth) which provides 24/7 health monitoring service and greatly improves the quality and efficiency of healthcare. However, users' concern about the security and privacy of their health information has become one of the major obstacles that impede the wide adoption of WBANs. Anonymous and unlinkable authentication is critical to protect the security and privacy of sensitive physiological information in transit from the client to the application provider. We first show that the anonymous authentication scheme of Wang and Zhang based on bilinear pairing is prone to client impersonation attack. Then, we propose an enhanced anonymous authentication scheme to remedy the flaw in Wang and Zhang's scheme. We give the security analysis to demonstrate that the enhanced scheme achieves the desired security features and withstands various known attacks.

Surface properties of polyurethanes modified by bioactive polysaccharide-based polyelectrolyte multilayers.

Lentinan, a mushroom polysaccharide, isolated from Lentinus edodes (Shiitake mushroom) was sulfated in dimethylsulfoxide to obtain a water-soluble derivative coded as LS. Then, two polysaccharide-based polyelectrolytes, polyanionic lentinan sulfate (LS) and polycationic chitosan (CS), were alternatively deposited onto the surfaces of polyurethane (PU) via layer-by-layer (LbL) assembly technique. The surfaces modified by polysaccharide-based multilayers were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. The fibrinogen adsorption and platelet adhesion to the surfaces, cytocompatibility to L-929 cells, and antibacterial activity against Pseudomonas aeruginosa of unmodified PU and LbL-modified PU were tested in vitro, respectively. The results showed that the water contact angle decreased gradually during the successive buildup of the polysaccharide-based multilayers, and decreased slowly after four bilayers were assembled. The surface roughness of PU modified by five bilayers (LS as topmost layer) increased compared with that of unmodified PU. The fibrinogen adsorption on the surface decreased 81% after assembly of five bilayers (LS as topmost layer). The number of adherent platelets on the surface modified by five bilayers (LS as topmost layer) is reduced, in comparison with that of the unmodified PU. The tests of L-929 cells indicated that LbL-modified PU surfaces had better cytocompatibility than unmodified PU. In addition, PU modified by polysaccharide-based multilayers showed antibacterial activity against P. aeruginosa.