Search

Ultrasmall and homogeneous bimetallic PdxBi nanoalloys are well distributed on a Vulcan carbon support by a facile, low-cost synthetic strategy. The electrochemical activity of the as-prepared homogeneous PdxBi nanoalloy/carbon black nanocomposites is closely related to the content of Bi, revealing their excellent electrocatalytic performance for selective oxidation of monohydric alcohols and vicinal diols in alkali medium. [ABSTRACT FROM AUTHOR]

A highly sensitive triple-amplification assay for the detection of microRNA (miRNA) let-7a is reported in this work. The assay relies on the formation of magnetic two-dimensional DNA/Fe3O4 nanosheet networks initiated by the target miRNA-associated hybridization chain reaction. The Fe3O4 nanosheets in the DNA/Fe3O4 networks display peroxidase-like catalytic activity towards a colorimetric reaction, thereby producing a highly sensitive signal for the quantification of let-7a. Under optimal conditions, the assay achieved a detection limit of 13 aM at a signal-to-noise ratio of 3 and a linear calibration plot between 0.05 fM and 12 nM. Successful attempts were made in the quantification of let-7a in serum samples. [ABSTRACT FROM AUTHOR]

Mesoporous NiO nanosheets with a single-crystalline structure were investigated as an oxygen electrode catalyst in a non-aqueous Li–O2 battery. The recharge voltage plateau achieved for the NiO-based Li–O2 battery was ca. 3.95 V, ca. 200 mV negatively shifted compared with that for β-Ni(OH)2 and acetylene black. The reaction mechanism during the charge process for the NiO-based Li–O2 battery was intensively researched. The results of X-ray photoelectron spectroscopy characterization indicated that Li2O2 and Li2CO3 were formed during the discharge process, which can be decomposed after recharge. These demonstrated that the NiO nanosheet exhibited a good activity for the decomposition of Li2O2 and Li2CO3. Furthermore, the results of the gas chromatography-mass spectrometry test reflected two steps of the recharge process, i.e., the oxidation of Li2O2 when the potential was below 4.0 V and the decomposition of Li2O2 and Li2CO3 when the potential was above 4.0 V. Moreover, no obvious performance decay was observed in the NiO-based battery even after 40 cycles when the capacity was limited to 500 mA h g−1, indicating an impressive cycling performance. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) carbonaceous aerogel derived from sustainable bacterial cellulose (BC) is introduced as a flexible framework for sulfur in lithium–sulfur batteries. The 3D carbonized BC (CBC) with highly interconnected nanofibrous structure exhibits good electrical conductivity and mechanical stability. The intrinsic macroporous structure of CBC contributes to a high sulfur loading of 81 wt%. Microstructure and morphology characterization results demonstrate that the sulfur species wrapped around CBC nanofibers are well dispersed. Even at such a high loading, the S/CBC composite still contains sufficient free space to accommodate the volume expansion of sulfur during lithiation. Furthermore, with an ultralight CBC interlayer inserted between the sulfur cathode and separator, significant improvement is achieved in active material utilization, cycling stability, and coulombic efficiency. The CBC interlayer can provide an extra conductive framework and adsorb migrating polysulfides to a certain degree. The CBC interlayer can also act as an additional collector for sulfur and thus could prevent the over-aggregation of insulated sulfur on the cathode surface. The good electrochemical performance reported in this work can be ascribed to the flexible 3D-interconnected nanostructure of the carbon framework and the rational design of battery configuration. [ABSTRACT FROM AUTHOR]

Porous activated carbon with a ultrahigh specific surface area (3164 m2 g-1) and large pore volume (1.88 cm3 g-1) was prepared from waste litchi shells with channel-like macropores via a KOH activation method. The macroporous structure of litchi shells is believed to be conducive to distribute the activation agent, which enables sufficient activation. The as-prepared activated carbon was developed as a conducting framework for lithium-sulfur battery cathode materials. The resulting activated carbon/sulfur composite cathode possesses a high specific capacity, good rate capability, and long-term cycling performance. At 200 mA g-1 current density, the initial discharge capacity of the activated carbon/sulfur composite cathode with 60 wt% sulfur content is 1105 mA h g-1 At a current density of 800 mA g-1, the activated carbon/sulfur composite cathode shows 51% capacity retention over 800 cycles with a fade rate of 0.06% per cycle. The coulombic efficiency of the cell remains at approximately 95%. By adding LiNO3 in the electrolyte, the activated carbon/sulfur composite electrode tested at 800 mA g-1 shows a high coulombic efficiency (>99%). The activated carbon/sulfur composites exhibited similar capacity value and cycling trends with an increase in sulfur content from 60% to 68%. The good electrochemical performance can be attributed to the excellent structural parameters of the activated carbon. The ultrahigh specific surface area and large pore volume not only enhances the sulfur content but also ensures dispersion of elemental sulfur in the conducting framework, thereby improving sulfur utilization. The small nanopores of the activated carbon can effectively inhibit the diffusion of polysulfides during the charge/discharge process. [ABSTRACT FROM AUTHOR]

Ultrasmall and homogeneous bimetallic PdxBi nanoalloys are well distributed on a Vulcan carbon support by a facile, low-cost synthetic strategy. The electrochemical activity of the as-prepared homogeneous PdxBi nanoalloy/carbon black nanocomposites is closely related to the content of Bi, revealing their excellent electrocatalytic performance for selective oxidation of monohydric alcohols and vicinal diols in alkali medium.

A highly sensitive triple-amplification assay for the detection of microRNA (miRNA) let-7a is reported in this work. The assay relies on the formation of magnetic two-dimensional DNA/Fe 3 O 4 nanosheet networks initiated by the target miRNA-associated hybridization chain reaction. The Fe 3 O 4 nanosheets in the DNA/Fe 3 O 4 networks display peroxidase-like catalytic activity towards a colorimetric reaction, thereby producing a highly sensitive signal for the quantification of let-7a. Under optimal conditions, the assay achieved a detection limit of 13 aM at a signal-to-noise ratio of 3 and a linear calibration plot between 0.05 fM and 12 nM. Successful attempts were made in the quantification of let-7a in serum samples.

Network structured carbonized bacterial cellulose-supported Ru nanoparticles (CBC/Ru), which provide sufficient space for Li2O2 deposition without a significant volume effect and improve the transport of oxygen and electrons, were used as the binder-free oxygen electrode in a Li-O2 battery. The CBC/Ru exhibited high activities and good stability during discharge-recharge processes.