Highly efficient ethanol vapour detection using g-C3N4/ZnO micro flower-like heterostructural composites.

This work proposes precursor pyrolysis, ultrasonic exfoliation and hydrothermal methods as well as high-temperature calcination strategies to fabricate heterostructured g-C3N4/ZnO composites with excellent ethanol vapour sensing properties. The structure, composition and morphology of the as-prepared g-C3N4/ZnO composites were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Then, the sensing properties of the g-C3N4/ZnO composites for ethanol (C2H5OH) were studied, and g-C3N4 doping with different mass ratios was used to control the gas-sensing properties of the composites. Compared with pure ZnO and g-C3N4, the performance of g-C3N4 with 1% doping content is the best, and the gas sensing activity of the 1% g-C3N4/ZnO composite is greatly improved at the optimal working temperature (280 °C). The response to 100 ppm ethanol reaches 81.4, which is 3.7 times that of the pure ZnO-based sensor under the same conditions. In addition, the sensor has good selectivity as well as fast response and recovery speeds (24 s and 63 s, respectively). Finally, a reasonable gas sensing enhancement mechanism is proposed, and it is believed that the constructed g-C3N4/ZnO micro flower-like heterostructure and the distinct positions of the valence and conduction bands of ZnO and g-C3N4 lead to the obtained sensor exhibiting a large specific surface area and increased conductivity, thereby improving the g-C3N4/ZnO-based sensor sensing performance.

Rationally engineering a hierarchical porous carbon and reduced graphene oxide supported magnetite composite with boosted lithium-ion storage performances.

Ferric gallate (Fe-GA), an ancient metal-organic framework (MOF) material, has been recently employed as an eco-friendly and cost-effective precursor sample to synthesize a porous carbon confined nano-iron composite (Fe/RPC), and the Fe element in the Fe/RPC sample could be further oxidized to Fe3O4 nanocrystals in a 180 °C hydrothermal condition. On this foundation, this work reports an optimized approach to engineering a hierarchical one-dimensional porous carbon and two-dimensional reduced graphene oxide (RGO) supporting framework with Fe3O4 nanoparticles well dispersed. Under mild hydrothermal condition, the redox reaction between metal iron atoms from Fe/RPC and surface functional radicals from few-layered graphene oxide sheets (GO) is triggered. As a result, reinforced microstructure and improved atomic efficiency have been achieved for the Fe3O4@RPC/RGO sample. The homogeneously dispersed Fe3O4 nanoparticles with controlled size are anchored on the surface of the larger sized RGO coating layers while the smaller sized RPC domains are embedded between the RGO sheets as spacer. Challenges including spontaneous aggregation of RPC, over exposure of Fe3O4 nanoparticles and excessive restacking of RGO have been significantly inhibited. Furthermore, micro-sized carbon fiber (CF) is chosen as a structural reinforcement additive during electrode fabrication, and the Fe3O4@RPC/RGO sample delivers a good specific capacity of 1170.5 mAh·g-1 under a current rate of 1000 mA·g-1 for 500 cycles in the half cell form. The reasons for superior electrochemical behaviors have been revealed and the lithium-ion storage performances of the Fe3O4@RPC/RGO sample in the full cell form have been preliminarily investigated.

Selective Doping to Controllably Tailor Maximum Unit-Cell-Volume Change of Intercalating Li+ -Storage Materials: A Case Study of γ Phase Li3 VO4.

Capacity decay of an intercalating Li+ -storage material is mainly due to the its particle microcracks from stress-causing volume change. To extend its cycle life, its unit-cell-volume change has to be minimized as much as possible. Here, based on a γ-Li3 VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit-cell-volume change, then clarify the relationship between its crystal-structure openness and maximum unit-cell-volume change, and finally demonstrate the superiority of "zero-strain" materials within 25-60 °C (especially at 60 °C). With increasing the large-sized Ge4+ dopant, the unit-cell volume of γ-Li3+ x Gex V1- x O4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit-cell-volume change. In contrast, the doping with small-sized Si4+ shows a reverse trend. The tailoring reveals that γ-Li3.09 Ge0.09 V0.91 O4 owns the smallest maximum unit-cell-volume change of 0.016% in the research field of intercalating Li+ -storage materials. Consequently, γ-Li3.09 Ge0.09 V0.91 O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity-retention percentages after 1800/1500 cycles at 2 A g-1 . This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long-life lithium-ion batteries.

Facile synthesis of boronic acid-decorated carbon nanodots as optical nanoprobes for glycoprotein sensing.

In this article, we proposed new nitrogen-doped boronic acid-decorated carbon nanodots (CNDs) for the recognition and detection of glycoproteins. These doped, decorated CNDs were obtained by a one-step hydrothermal carbonization method using phenylboronic acid and ethylenediamine as precursors. Compared to traditional synthesized and then functionalized nanoscale sensing systems, this method is more facile and efficient. The as-prepared nitrogen-doped CNDs possessed a quasi-spherical morphology and a high quantum yield of approximately 14.5%. The added glycoproteins (taking horseradish peroxidase as a model protein) can selectively induce the assembly and fluorescence quenching of CNDs through the formation of cyclic boronate esters, because the boronic acid groups on the CND surfaces can covalently interact with cis-diol-containing glycoproteins. These fluorescence responses can be used to properly quantify horseradish peroxidase in the range of 3.3-333.3 µg mL-1 with a detection limit of 0.52 µg mL-1, and the selectivity assay with functionalized CNDs was further investigated using various proteins with different quantities of glycosylation sites as well as using smaller molecules. The results show that the nanosensing system possesses favorable selectivity. Due to its simplicity and effectiveness, the system has great application prospects as a practical platform for glycoprotein sensing.

Facile synthesis of ZnO nanorod arrays and hierarchical nanostructures for photocatalysis and gas sensor applications.

A facile one-step hydrothermal route was demonstrated to grow ZnO nanorod arrays and hierarchical nanostructures on arbitrary substrates without any catalysts and seeds coated before the reaction, which are prerequisite in the current two-step protocol. Meanwhile, ZnO nanoflowers composed of nanorods were obtained at the bottom of the autoclaves in the absence of substrates. An in situ spontaneous-seeds-assisted growth mechanism was tentatively proposed on the basis of the experimental data to explain the growth process of ZnO nanostructures. Moreover, the obtained ZnO nanorod arrays exhibited superior photocatalytic activity for decomposing methyl orange, and the nanoflowers showed better gas sensing performance towards some flammable gases and corrosive vapors with high sensitivity, rapid response-recovery characteristics, good selectivity and long-term stability.