High quality metastable wurtzite γ-MnS nanowires were synthesized via solution–solid–solid (SSS) growth in a mixed solvent of 1-dodecylamine and 1-dodecanethiol at a specified volume ratio. The length of the γ-MnS nanowires can be conveniently and well controlled by adjusting the amount ratio of [(C4H9)2NCS2]2Mn precursors to Ag2S catalysts. The results suggest the great potential of the SSS growth in the synthesis of high quality metastable chalcogenide nanowires.

High volumetric energy density combined with high power density is highly desired for electrical double-layer capacitors. Usually the volumetric performance is improved by compressing carbon material to increase density but at the much expense of power density due to the deviation of the compressed porous structure from the ideal one. Herein the authors report an efficient approach to increase the density and optimize the porous structure by collapsing the carbon nanocages via capillarity. Three samples with decreasing sizes of meso- and macropores provide us an ideal model system to demonstrate the correlation of volumetric performance with porous structure. The results indicate that reducing the surplus macropores and, more importantly, the surplus mesopores is an efficient strategy to enhance the volumetric energy density while keeping the high power density. The optimized sample achieves a record-high stack volumetric energy density of 73 Wh L−1 in ionic liquid with superb power density and cycling stability.

The unique hierarchical nitrogen-doped carbon nanocages (hNCNC) are used as a new support to homogeneously immobilize spinel CoFe2O4 nanoparticles by a facile solvothermal method. The so-constructed hierarchical CoFe2O4/hNCNC catalyst exhibits a high oxygen reduction activity with an onset potential of 0.966 V and half-wave potential of 0.819 V versus reversible hydrogen electrode, far superior to the corresponding 0.846 and 0.742 V for its counterpart of CoFe2O4/hCNC with undoped hierarchical carbon nanocages (hCNC) as the support, which locates at the top level for spinel-based catalysts to date. Consequently, the CoFe2O4/hNCNC displays the superior performance to the CoFe2O4/hCNC, when used as the cathode catalysts in the home-made Al-air batteries. X-ray photoelectron spectroscopy characterizations reveal the more charge transfer from CoFe2O4 to hNCNC than to hCNC, indicating the stronger interaction between CoFe2O4 and hNCNC due to the nitrogen participation. The enhanced interaction and hierarchical morphology favor the high dispersion and modification of electronic states for the active species as well as the mass transport during the oxygen reduction process, which plays a significant role in boosting the electrocatalytic performances. In addition, we noticed the high sensitivity of O 1s spectrum to the particle size and chemical environment for spinel oxides, which is used as an indicator to understand the evolution of ORR activities for all the CoFe2O4-related contrast catalysts. Accordingly, the well-defined structure-performance relationship is demonstrated by the combination of experimental characterizations with theoretical calculations. This study provides a promising strategy to develop efficient, inexpensive and durable oxygen reduction electrocatalysts by tuning the interaction between spinel metal oxides and the carbon-based supports.Download high-res image (195KB)Download full-size image

Pt-based electrocatalysts are the most popular for direct alcohol fuel cells, but their performances easily deteriorate for the oxygen reduction reaction (ORR) at the cathode because of the alcohol crossover effect. Herein, we report the novel Pt electrocatalyst encapsulated inside nitrogen-doped carbon nanocages (Pt@NCNC), which presents excellent alcohol-tolerant ORR activity and durability in acidic media, far superior to the Pt counterpart immobilized outside the nanocages (Pt/NCNC). The superb performance is correlated with the molecule-sieving effect of the micropores penetrating through the shells of the nanocages, which admit the small-sized oxygen and ions but block the large-sized alcohols into the nanocages. This mechanism is confirmed by examining the size dependence of ORR and alcohol oxidation activities by regulating the micropores sizes. This study provides a promising strategy to develop the superior alcohol-tolerant Pt-based ORR electrocatalyst in acidic media.

α- and β-Si3N4 belts with tunable width were synthesized by regulating the partial pressure of NH3/N2 in gaseous mixtures of Ar and NH3/N2 during the nitridation of silicon powders, which demonstrated tunable photoluminescence properties.

•Novel 3D hierarchical carbon nanocages with high pore volume, network geometry and good conductivity.•High-loading confinement of ~80 wt% sulfur inside the nanocages.•Much alleviated polysulfides dissolution due to the confinement.•The high-rate performance for the high-sulfur-loading carbon-sulfur composites.•Well established correlation between the high performance and unique structure.Lithium–sulfur batteries are hindered by the low utilization of sulfur, short cycle life and poor rate capability which are severe challenges today. Herein we report a new kind of carbon–sulfur composites by infusing sulfur into the novel hierarchical carbon nanocages (hCNC) with high pore volume, network geometry and good conductivity. The designed S@hCNC composite with a high sulfur loading of 79.8 wt% presents the large capacity, high-rate capability and long cycle life, which could shorten the charging time for mobile devices from hours to minutes. The excellent performance derives from the unique mesostructure of hCNC that enables the encapsulation of high-loading sulfur inside the carbon nanocages to alleviate polysulfide dissolution, meanwhile much enhance the electron conduction and Li-ion diffusion.

Novel hierarchical carbon nanocages (hCNCs) are proposed as high-rate anodes for Li- and Na-ion batteries. The unique structure of the porous network for hCNCs greatly favors electrolyte penetration, ion diffusion, electron conduction, and structural stability, resulting in high rate capability and excellent cyclability. For lithium storage, the corresponding electrode stores a steady reversible capacity of 970 mAh·g−1 at a rate of 0.1 A·g−1 after 10 cycles, and stabilizes at 229 mAh·g−1 after 10,000 cycles at a high rate of 25 A·g−1 (33 s for full-charging) while delivering a large specific power of \(37 kW \cdot kg_{electrode^{ - 1} }\) and specific energy of \(339 Wh \cdot kg_{electrode^{ - 1} }\). For sodium storage, the hCNC reaches a high discharge capacity of ∼50 mAh·g−1 even at a high rate of 10 A·g−1.

Fischer–Tropsch synthesis (FTS) is a classical topic of great significance because of the approach of post-petroleum times. For decades, people have attempted to develop iron-based FTS catalysts with high selectivity for lower olefins. By means of the anchoring effect and the intrinsic basicity of nitrogen-doped carbon nanotubes (NCNTs), iron nanoparticles were conveniently immobilized on NCNTs without surface premodification. The so-constructed Fe/NCNTs catalyst presents superb catalytic performance in FTS with high selectivity for lower olefins of up to 46.7% as well as high activity and stability. The excellent performance is well-correlated with enhanced dissociative CO adsorption, inhibition of secondary hydrogenation of lower olefins, and promoted formation of the active phase of χ-Fe5C2. All of these merits result from participation of the nitrogen, as revealed by our experimental characterization. These results may lead to a new strategy for exploring advanced FTS catalysts with abundant N-doped carbon nanostructures.Keywords: basicity; Fischer−Tropsch synthesis; heterogeneous catalysis; iron nanoparticles; lower-olefin selectivity; nitrogen-doped carbon nanotubes

The synthesis of heterostructures with branched morphology is of great importance for exploiting novel physical and chemical properties in nanoscience and nanotechnology fields. In this study, by combining the extended vapor–liquid–solid (EVLS) and vapor–solid (VS) growth methods, we successfully fabricate three-dimensional (3D) AlN–Si3N4 branched heterostructures with the core of Si3N4 nanostructures and branched AlN nanocones with adjustable diameter and length. The photoluminescence (PL) spectra of the AlN–Si3N4 branched heterostructures display new emission bands besides those of the as-synthesized Si3N4 nanostructures, which may be ascribed to the emission bands of AlN in the deep- or trap-level state. From these results we propose a general strategy for designing and preparing 3D branched heterostructures for novel optoelectronic devices.

•We fabricated OTFTs with CuPc films grown under different deposition pressures.•Enhanced device performance was obtained at high deposition pressure.•Deposition pressure modulated CuPc molecular packing and orientation.•Contact resistance decreased when deposition pressure increased.Copper phthalocyanine (CuPc)-based thin film transistors were fabricated using CuPc films grown under different deposition pressure (Pdep) (ranging from 1.8 × 10−4 Pa to 1.0 × 10−1 Pa). The transistor performance highly depended on Pdep. A field-effect mobility of 2.1 × 10−2 cm2/(V s) was achieved under 1.0 × 10−1 Pa. Detailed investigations revealed that Pdep modulates the molecular packing and orientation of the organic films grown on a SiO2/Si substrate and influences the charge transport. Furthermore, from a device physics point of view, contact resistance of the fabricated transistors decreased when Pdep increased, which was beneficial in reducing energy consumption.Graphical abstract

Four typical-shaped organic molecules including disk-, rod-, branch-, and sphere-like semiconductors are selected to investigate the influence of deposition pressure (Pdep) on the film morphologies, molecular packing, and mobilities. Different correlations of the microstructures and mobilities with Pdep are obtained, which are closely related with the corresponding molecular shapes. For disk-like F16CuPc and rod-like pentacene, higher Pdep leads to the lager interplanar spacing (D value) and grain sizes of the films which are beneficial to the charge transport and mobilities. For the branch-like TIPS-pentacene and sphere-like C60, the D values of the films keep unchanged and the grain sizes increase with increasing Pdep, presenting the unchanged or even decreased mobilities, respectively. The Pdep-dependence should be correlated with the interactions between the collisional N2 and organic molecules, the organic molecules and substrate, as well as among the organic molecules themselves, which is closely associated with the molecular shapes as partly understood by our theoretical simulations. This study suggests a convenient approach to optimize high-performance organic thin film transistors (OTFTs) according to the molecular shapes by regulating deposition pressure, and is also helpful for understanding the charge transport and performance of OTFTs.

Nitrogen-doped carbon nanotubes (NCNTs) have been catalytically synthesized from five different nitrogen-containing aromatic precursors by injection chemical vapor deposition (CVD) in the temperature range of 550–850 °C. The doped nitrogen mainly exists as pyridinic or graphitic nitrogen with the total content of 2–9 at. % depending on the precursor and preparation condition. Over 60% carbon and nitrogen atoms could be converted to NCNTs products for all the precursors, indicating the high efficiency and potential for scale-up of the injection CVD method. The oxidation processes of the NCNTs products have been illustrated in detail with the in-situ thermogravimetry–differential scanning calorimetry–mass spectrum coupling technique, and the results clearly indicate the successful incorporation of nitrogen into the nanotubes as supported by X-ray photoelectron spectroscopy. There is a dependent correlation between the pre-existing C–N bond in the precursor and the N incorporation in the corresponding NCNTs product. This suggests a general preparation strategy of NCNTs for scale-up and regulation of nitrogen content and status.

Copper phthalocyanine (CuPc) films have been prepared on SiO2 and octadecyltrichlorosilane (OTS)-treated SiO2 (OTS/SiO2) substrates by vacuum deposition under different deposition pressures (Pdep) ranging from 10–4 to 10–1 Pa. Experimental results indicate that Pdep has an obvious influence on the morphologies and molecular packing structures of the CuPc films and, therefore, the performance of the resulting thin-film transistors (TFTs). Specifically, the grain sizes of the CuPc films keep almost unchanged for Pdep below 10–2 Pa and significantly increase for further increasing Pdep to 10–1 Pa on both SiO2 and OTS/SiO2. The interplanar spacings (D values) of the films increase on SiO2 and keep unchanged on OTS/SiO2 with increasing Pdep, which has also been rationalized by the molecular dynamics simulation. Field-effect measurements indicate that the electronic properties of the CuPc thin films are closely correlated with their microstructures, and the film prepared at higher Pdep gives the higher mobility. In addition to the general results that larger grain size favors the higher mobility similar to literature reports, both our experimental and theoretical results reveal that the interplanar spacing of the film also has a sensitive influence on the mobility of the CuPc TFTs, and the larger D value leads to the higher mobility. This study provides a convenient way to tune the morphology and molecular packing of the CuPc films to optimize the performance simply by regulating Pdep and discloses an important parameter, that is, the D value, associated with the device performance, which is significant for basic understanding and potential applications.

We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon dioxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drain electrodes and the pentacene active layer. The threshold voltage decreased remarkably from ca. −20 V to a few volts (below −7.6 V) while the mobility increased 1.5–3 times after the insertion of the interlayer of only ca. 2 nm, which could be attributed to the reduction of the carrier injection barrier. The results suggest a simple and effective way to achieve low-threshold-voltage pentacene-based organic thin film transistors with high mobility on silicon dioxide dielectric.

High quality metastable wurtzite γ-MnS nanowires were synthesized via solution–solid–solid (SSS) growth in a mixed solvent of 1-dodecylamine and 1-dodecanethiol at a specified volume ratio. The length of the γ-MnS nanowires can be conveniently and well controlled by adjusting the amount ratio of [(C4H9)2NCS2]2Mn precursors to Ag2S catalysts. The results suggest the great potential of the SSS growth in the synthesis of high quality metastable chalcogenide nanowires.