No abstract

Molybdate-based inorganic-organic hybrid disks with a highly ordered layered structure were synthesized via an acid-base reaction of white molybdic acid (MoO 3 $H 2 O) with n-octylamine (C 8 H 17 NH 2 ) in ethanol at room temperature. The thermal treatment of the as-obtained molybdatebased inorganic-organic hybrid disks at 550 C in air led to formation of orthorhombic a-MoO 3 nanoplates. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal analysis (TG-DTA), Fourier-transform infrared (FT-IR) spectra, Raman spectra, and a laser-diffraction grain-size analyzer were used to characterize the starting materials, the intermediate hybrid precursors and the final a-MoO 3 nanoplates. The XRD, FT-IR and TG-DTA results suggested that the molybdate-based inorganic-organic hybrid compound, with a possible composition of (C 8 H 17 NH 3 ) 2 MoO 4 , was of a highly ordered lamellar structure with an interlayer distance of 2.306(1) nm, and the n-alkyl chains in the interlayer places took a double-layer arrangement with a tilt angle of 51 against the inorganic MoO 6 octahedra layers. The SEM images indicated that the molybdate-based inorganic-organic hybrids took on a well-dispersed disk-like morphology, which differed distinctly from the severely aggregated morphology of their starting MoO 3 $H 2 O powders. During the calcining process, the disk-like morphology of the hybrid compounds was well inherited into the orthorhombic a-MoO 3 nanocrystals, showing a definite plate-like shape. The a-MoO 3 nanoplates obtained were of a single-crystalline structure, with a side-length of 1-2 mm and a thickness of several nanometres, along a thickness direction of [010]. The above a-MoO 3 nanoplates were of a loose aggregating texture and high dispersibility. The chemical sensors derived from the as-obtained a-MoO 3 nanoplates showed an enhanced and selective gas-sensing performance towards ethanol vapors. The a-MoO 3 nanoplate sensors reached a high sensitivity of 44-58 for an 800 ppm ethanol vapor operating at 260-400 C, and their response times were less than 15 s.

The hierarchical photocatalysts of Ag/AgCl@plate-WO₃ have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO₃ nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO₃ suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO₃ composites, which were then photoreduced to form Ag/AgCl@WO₃ nanostructures in situ. WO₃ nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO₃ photocatalysts, and the effects of the WO₃ contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N₂ adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO₃ nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO₃ photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO₃ and TiO₂ (P25). The contents and morphologies of the WO₃ substrates in the Ag/AgCl@plate-WO₃ photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.

No abstract

No abstract

Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple redox reaction between Sn(2+) ions and graphene oxide (GO) nanosheets under microwave irradiation. XRD, SEM, TEM, XPS, TG-DTA and N2 adsorption-desorption are used to characterize the compositions and microstructures of the SnO2@rGO samples obtained. The SnO2@rGO nanostructures are used as gas-sensing and electroactive materials to evaluate their property-microstructure relationship. The results show that SnO2 nanoparticles (NPs) with particle sizes of 3-5 nm are uniformly anchored on the surfaces of reduced graphene oxide (rGO) nanosheets through a heteronucleation and growth process. The as-obtained SnO2@rGO sample with a hierarchically sesame cake-like microstructure and a superhigh specific surface area of 2110.9 m(2) g(-1) consists of 92 mass% SnO2 NPs and ∼8 mass% rGO nanosheets. The sensitivity of the SnO2@rGO sensor upon exposure to 10 ppm H2S is up to 78 at the optimal operating temperature of 100 °C, and its response time is as short as 7 s. Compared with SnO2 nanocrystals (5-10 nm), the hierarchical SnO2@rGO nanostructures have enhanced gas-sensing behaviors (i.e., high sensitivity, rapid response and good selectivity). The SnO2@rGO nanostructures also show excellent electroactivity in detecting sunset yellow (SY) in 0.1 M phosphate buffer solution (pH = 2.0). The enhancement in gas-sensing and electroactive performance is mainly attributed to the unique hierarchical microstructure, high surface areas and the synergistic effect of SnO2 NPs and rGO nanosheets.

No abstract

An artificial bio-capacitor system is established, consisting of the proton-pump protein proteorhodopsin and a modified alumina nanochannel, inspired by the capacitor-like behavior of plasma membranes realized through the cooperation of ion-pump and ion-channel proteins. Capacitor-like features of this simplified system are realized and identified, and the photocurrent duration time can be modulated by nanochannel modification to obtain favorable square-wave currents.