Biosensors can convert the concentration of biological analytes into an electrical signal or other signals for detection. They are widely used in medical diagnostics, food safety, process control, and environmental monitoring fields. In recent years, new schemes of stable biosensor interfaces have attracted much attention. Interface design is a vital part of biosensor development, since its stability can be directly related to the quality of sensing performance such as sensitivity, stability, and linearity. This review summarized the latest methods and materials used to construct stable biosensor interfaces and pointed some future perspectives and challenges of them. From the literature, we found that nanomaterials, polymers, and their composites such as chitosan, cellulose, and conducting polymers are the most common materials used in the biosensor interface design. Apart from materials, there are increasing developments in monolayer membrane techniques, three-dimensional constructions, and other interface techniques. This review is a study of the latest progress in biosensor interface stability solutions, which may provide some references and innovative directions of biosensor interface design for researchers in biosensor fields and encourage people to further explore new materials and methods.

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The depth profiles of metamorphic In x Al 1−x As ͑0.05Ͻ x Ͻ 1͒ buffer layers grown on GaAs substrates were characterized using the x-ray reciprocal space mapping. Three types of metamorphic samples were investigated and compared: step grade, single-slope linear grade, and dual-slope linear grade. The lattice mismatch, residual strain, crystallographic tilt, tilt azimuth, and the full width at half maximum were obtained from the reciprocal space maps. The tilt angle of linearly graded buffer layers stayed low at low In compositions until InϷ 60%, at which composition the tilt angle increased abruptly. All linear-grade samples had an untilted relaxed structure in the low In region ͑below 60% In͒ and a tilted structure in the upper, high In region ͑above 60% In͒. The average lattice mismatch between the untilted relaxed structure and the tilted structure determines the tilt angle. The tilt angle of the step-graded layers increased at a near-linear rate as the In composition was increased. The tilt azimuth was intermediate between the ͗100͘ and ͗110͘ in-plane directions. The x-ray full width at half maximum generally increased with the In composition, but tended lower toward surface. We suggest a possible design strategy for the linear-grade metamorphic buffer layer based on our result.

Studies of ferromagnetic MnAs in recent years have revealed a wide range of properties desirable for spintronic applications. Previously studied MnAs spin-light-emitting-diodes exhibited a low value of spin injection into the device active region. In this work, we have investigated injection of spin polarized electrons from MnAs into AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p structures. The band-edge electroluminescence emitted from these devices has a saturation circular polarization of 26% at 7 K and B=2 T. Using optical pumping measurements the corresponding electron spin polarization was determined to be 52%. Emission persists up to room temperature, with a saturation circular polarization of 6% at B=2 T.

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This paper proposes an effective strategy of material system optimization to improve acetone gas sensing performance based on hydrothermally processed transition metal (Fe, Co or Ni)-doped WO3 materials. A detailed comparison of the capability of pure WO3 and X:WO3 (X = Fe, Co, Ni) to sense acetone gas at room temperature was performed. It was found that the sensitivity of Ni:WO3 nanoflowers to acetone was much higher than that of pure WO3, Fe:WO3 and Co:WO3 under white light irradiation. To obtain a highly sensitive acetone gas sensor, the molar doping ratio of Ni to WO3 was further optimized. It was found that 3%Ni:WO3 had the highest response–recovery speed and the best target gas selectivity. Acetone with a concentration as low as 2 ppm can be detected at room temperature (20 °C). The sensitivity enhancement mechanism of the Ni:WO3 gas sensor is also discussed. It is expected that under white light irradiation the proposed Ni-doped WO3 can be used as a highly sensitive and selective acetone gas sensor at room temperature.

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