We present a useful ammonia gas sensor based on chemically reduced graphene oxide (rGO) sheets by self-assembly technique to create conductive networks between parallel Au electrodes. Negative graphene oxide (GO) sheets with large sizes (>10 μm) can be easily electrostatically attracted onto positive Au electrodes modified with cysteamine hydrochloride in aqueous solution. The assembled GO sheets on Au electrodes can be directly reduced into rGO sheets by hydrazine or pyrrole vapor and consequently provide the sensing devices based on self-assembled rGO sheets. Preliminary results, which have been presented on the detection of ammonia (NH₃) gas using this facile and scalable fabrication method for practical devices, suggest that pyrrole-vapor-reduced rGO exhibits much better (more than 2.7 times with the concentration of NH₃ at 50 ppm) response to NH₃ than that of rGO reduced from hydrazine vapor. Furthermore, this novel gas sensor based on rGO reduced from pyrrole shows excellent responsive repeatability to NH₃. Overall, the facile electrostatic self-assembly technique in aqueous solution facilitates device fabrication, the resultant self-assembled rGO-based sensing devices, with miniature, low-cost portable characteristics and outstanding sensing performances, which can ensure potential application in gas sensing fields.

Slonczewski-like torque and the Dzyaloshinskii–Moriya interaction (DMI) are important factors in current-induced magnetization switching and domain-wall motion seen in ferromagnetic metal (FM)/heavy metal (HM) structures. We demonstrate the tuning of both factors by inserting a thin Pt layer between Ta and CoFeB in the Ta/CoFeB/MgO structures. The results suggest that the Slonczewski-like torque and DMI decreases with increasing Pt thickness (t_Pt) in the range 0–1 nm. In consequence, the critical switching current density from the induced spin-orbit torque (SOT) increases whereas the required in-plane field for deterministic switching decreases. The sign of the DMI reverses around t_Pt = 1 nm, confirming that D has the opposite sign at the Ta/CoFeB and Pt/CoFeB interfaces; but its intensity saturates at t_Pt = 3 nm, suggesting that several interface monolayers may contribute to the DMI. Our results verifies that a thin HM interlayer may be a suitable route to tailor the SOTs and DMI at the HM/FM interface, as well as the current-induced magnetization switching in these structures.

A facile synthesis route of cuprous oxide (Cu₂O) hollow spheres under different temperatures without the aid of a surfactant was introduced. Morphology and structure varied as functions of reaction temperature and duration. A bubble template-mediated formation mechanism was proposed, which explained the reason of morphology changing with reaction temperature. The obtained Cu₂O hollow spheres were active photocatalyst for the degradation of methyl orange under visible light. A self-designed equipment of light emitting diode (LED) cold light sources with the wavelength of 450, 550, and 700 nm, respectively, was used for the first time in the photocatalysis experiment with no extra heat introduced. The most suitable wavelength for Cu₂O to photocatalytic degradation is 550 nm, because the light energy (2.25 eV) is closest to the band gap of Cu₂O (2.17 eV). These surfactant-free synthesized Cu₂O hollow spheres would be highly attractive for practical applications in water pollutant removal and environmental remediation.

Planar anisotropy Nd₂Co₁₇ flakes fractured along c crystal plane were fabricated by surfactant-assisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5–20 μm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd₂Co₁₇ epoxy resin composite has been investigated in the frequency range of 0.1–18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd₂Co₁₇. The planar anisotropic Nd₂Co₁₇ flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz.