Narrow Results

To explore the practicability of C₆₀ synthesis under extreme conditions (high pressure and high temperature), trinitrotoluene (TNT), trinitramine (RDX) and graphite mixtures of different proportions were detonated in a vacuum container, and the detonation products were collected for detecting. The results of mass spectroscopy, high performance liquid chromatography showed significant signals of C₆₀, which proved that C₆₀ could be synthesized by detonating the mixture of TNT and graphite (in 6:4 and 7:3 mass ratio, respectively), the detonation pressure and temperature were calculated around 13 GPa and 2000 K, respectively. Both experiment results and theoretical analysis showed the importance of detonation pressure and cooling temperature in detonation synthesis of C₆₀.

In this paper, we report strong variations in the Raman spectra of different carbon allotropes samples, for temperatures ranging from 83 K to 1123 K. The temperature dependence of D and G peak frequencies in the Raman spectrum of diamond, graphite, graphene, and carbon nanoparticles (CNPs) with 20 nm dot-size were investigated. These effects caused by temperature can be estimated from the changes in position and in linewidth of peak full width at half maximum (FWHM) G in the Raman spectrum of each sample. The broadening for each allotrope under the same conditions of temperature were: diamond ~ 4 cm^-1, graphite ~ 50 cm^-1, graphene ~ 5 cm^-1 and nanoparticles ~ 7 cm^-1. We also used scanning electron microscopy (SEM) to study the morphology and determine the size of the samples. According to the experimental data, the residual structural disorder and stress present in the samples are enhanced with temperature and responds for the observed changes in the Raman spectra. We present a systematic study of the temperature-dependent Raman spectra of four carbon allotropes.

A systematic investigation of structural, mechanical, elastic anisotropy and electronic properties of a recently reported novel superhard material orthorhombic $C_{20}$ ($o$-$C_{20}$) under pressure is performed utilizing the density functional theory in this work. The crystal structure parameters are obtained at zero as well as at high pressure. Pressure induced elastic constants $C_{ij}$, polycrystalline aggregate elastic modulus $(B,G,E)$, $B/G$ ratio, and Debye temperature changes for $o$-$C_{20}$ have been determined. The crystal elastic anisotropies of the ultra-incompressible $o$-$C_{20}$ are investigated in the pressure range of 0–100 GPa. The Lyakhov–Oganov model is applied to predict the hardness as functions of pressure. The calculated results reveal that $o$-$C_{20}$ possesses high elastic anisotropy under zero pressure and high pressure, and the hardness of $o$-$C_{20}$ decreases with pressure, while the Debye temperature behaves with the opposite trend. The results of electronic structure indicate that $o$-$C_{20}$ exhibits insulator characteristics, and the band gap increases with pressure. This work is expected to provide a useful guide for the future synthesis and application of $o$-$C_{20}$.

This paper reports the synthesis and characterization of ternary nanocomposites consisting of polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and manganese dioxide (MnO₂) at different MWCNT–MnO₂ loadings. The composite electrical percolation threshold is investigated as well. The in situ nanocomposites were characterized by UV-visible, Fourier transform and Raman spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and electrical conductivity measurements. The conductivity of the nanocomposite reached up to 78.79 Scm^-1 with 50 wt.% addition of MWCNT–MnO₂ with good conduction stability and reversibility. The percolation threshold of this nanocomposite was achieved at 0.5 wt.%. Using the scaling law of the percolation theory, it was found that the theoretical conductivity of the nanocomposite exhibited an exponential factor, (t) of 1.38 instead of the universal t value of 2.

In this study, silver orthophosphate@carbon layer (Ag₃PO₄@C) core/shell heterostructure photocatalyst was prepared for the first time. The results showed that a uniform carbon layer was formed around the Ag₃PO₄. By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer could be easily controlled. Furthermore, the Ag₃PO₄@C had remarkable light absorption in the visible region. Photocatalytic tests displayed that the Ag₃PO₄@C heterostructures possessed a much higher degradation rate of phenol than pure Ag₃PO₄ under visible light. The enhanced photocatalytic activity could be attributed to high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon as a sensitizer and Ag₃PO₄. Recycle tests showed that the Ag₃PO₄@C core/shell heterostructures maintained high stability over several cycles. The good stability could be attributed to the protection of insoluble carbon layer on the surfaces of Ag₃PO₄ crystals in aqueous solution.

The increasing energy crisis promotes the study on novel electrode materials with high performance for supercapacitive storage and energy conversion. Transition metal phosphates have been reported as a potential candidate due to the unique coordination and corresponding electronic structure. Herein, we adopted a facile method for preparing NaCoPO₄@C derived from a metal organic framework (MOF) as a bifunctional electrode. ZIF-67 was synthesized before a refluxing process with Na₂HPO₄ to form a precursor, which is transformed into the final product via calcination in different atmospheres. Specifically, the resultant NaCoPO₄@C exhibits a high specific capacitance of 1178.7Fg${}^{-1}$ at a current density of 1Ag${}^{-1}$ for a supercapacitor. An asymmetric supercapacitor (ASC) assembled with active carbon displays a high capacitance of 163.7Fg${}^{-1}$ at 1Ag${}^{-1}$. In addition, as an oxygen evolution reaction (OER) catalyst, the NaCoPO₄@C electrode requires only 299mV to drive a current density of 10mAcm${}^{-2}$. These results suggest that the rational design of MOF-derived NaCoPO₄@C provides a variety of practical applications in electrochemical energy conversion and storage.

Multi-element doped porous carbon materials are considered as one of the most promising electrode materials for supercapacitors due to their large specific surface area, abundant mesoporous structure, heteroatom doping and good conductivity. Herein, we propose a very simple and effective strategy to prepare nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) by one-step pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. The optimized N-S-HPC-2 possesses a typical hierarchically porous framework (micropores, mesopores and macropores) with a large specific surface area (1284.87m² g${}^{-1})$ and N (4.63 atomic %), S (0.53 atomic %) doping. As a result, the N-S-HPC-2 exhibits excellent charge storage capacity with a high gravimetric capacitance of 360F g${}^{-1}$ (1 A g${}^{-1})$ in three-electrode systems and 178F g${}^{-1}$ in two-electrode system and long-term cycling life with 87% retention after 10,000 cycles in KOH electrolyte.

Nanofluids are promising in solar harvesting and solar thermal utilization. Ethylene glycol (EG) nanofluids have the advantages of high boiling point and low volatility, and therefore are highly desired in some circumstances. In this study, the solar harvesting and solar thermal conversion properties of EG were significantly enhanced by carbon chain nanostructures (CCNSs). The prepared CCNSs/EG nanofluids showed greater optical absorption compared to EG in the wavelength range from 250nm to 1400nm. The solar weighted absorption factor (Am) of the CCNSs/EG nanofluids was 95.9% at the mass fraction of 0.05 wt.%. The enhancement was 649.2% compared to that of EG. The photothermal conversion efficiency was determined to be 97.7% and the enhancement of 83.0% was achieved. An enhancement of 1.2% in thermal conductivity was also been observed. These enhancements can be ascribed to the special architectures of the CCNSs that provide fast transfer path for the generated heat.

Carbon quantum dots (C QDs) were synthesized using lemon juices as a precursor by hydrothermal method. The impact of C QDs on the biomass, density of spores, and morphology of Aspergillus oryzae (A. oryzae) was studied for the first time. The results revealed that C QDs had a graphite structure, and their average size was about 4.25nm. As a carbon source, C QDs were more beneficial to A. oryzae growth than glucose. It has been observed that C QDs worked as an activator to improve the yield of A. oryzae, and the biomass and density of spores of A. oryzae cultured with 15mg C QDs were about 1.46 and 2.00 times higher than that in control medium (without C QDs). Our work can give a new idea for improving the yield of A. oryzae or microorganisms and satisfy industrial requirements.