Growth of single-walled carbon nanotubes from well-defined POSS nanoclusters structure

High-quality single-walled carbon nanotubes (SWNTs) with narrow diameter distribution can be generated from well-defined Si8O12 nanoclusters structure which form from thermal decomposition of chemically modified polyhedral oligomeric silsesquioxane (POSS). The nanosized SixOy particles were proved to be responsible for the SWNT growth and believed to be the reason for the narrow diameter distribution of the as-grown SWNTs. This could be extended to other POSS. The SWNTs grown from the nanosized SixOy particles were found to be semiconducting enriched SWNTs (s-SWNTs). A facile patterning technology, direct photolithography, was developed for generating SWNT pattern, which is compatible to industrial-level fabrication of SWNTs pattern for device applications. The metal-free growth together with preferential growth of s-SWNTs and patterning in large scale from the structure-defined silicon oxide nanoclusters not only represent a big step toward the control growth of SWNTs and fabrication of devices for applications particularly in nanoelectronics and biomedicine but also provide a system for further studying and understanding the growth mechanism of SWNTs from nanosized materials and the relationship between the structure of SWNT and nonmetal catalysts

Managing Residue Return Increases Soil Organic Carbon, Total Nitrogen in the Soil Aggregate, and the Grain Yield of Winter Wheat

Soil tillage and maize residues return are important practices for tackling and promoting soil quality and improving crop yield in the North China Plain (NCP), where winter wheat production is threatened by soil deterioration. Although maize residues incorporation with rotary tillage (RS) or deep plowing tillage (DS) is widespread in this region, only few studies have focused on rotation tillage. Four practices, namely RT (continuous rotary tillage without maize residues return), RS, DS, and RS/DS (rotary tillage every year and deep plowing interval of 2 years), were evaluated under field conditions lasting a period of 5 years. After a 5-year field experiment, the mean soil bulk density of the 0–30 cm soil layer decreased significantly with RS, DS, and RS/DS, i.e., by 4.19%, 6.33%, and 6.71% compared with RT, respectively. The treatments greatly improved the total soil porosity, soil aggregate size distribution, soil aggregate stability, and the root length density in the 0–30 cm soil layers. Residues return with DS and RS/DS treatments significantly increased the soil organic carbon (SOC) and total nitrogen (TN) storage in the 0–30 cm soil layer, mainly owed to the increases in the SOC and TN pool associated with the macro-aggregate. A positive trend in the grain yield was noted under both DS and RS/DS conditions, whereas a decreasing tendency was presented in continuous rotary treatments. In summary, RS/DS treatment significantly increased the amount of SOC and TN, improved the particle size distribution of soil aggregates, and thus improved the soil’s physicochemical properties, which is beneficial for wheat to achieve high yields. Our results suggested that RS/DS was a highly efficient practice to improve soil quality and increase crop production in the NCP

Pyrazino[2,3-g]quinoxaline-based conjugated copolymers with indolocarbazole coplanar moieties designed for efficient photovoltaic applications †

A series of low band gap copolymers consisting of electron-accepting pyrazino[2,3-g]quinoxaline (PQx) and an electron-donating indolo [3,2-b]carbazole and thiophene units have been designed and synthesized by Stille coupling polymerization. Their optical and electrical properties could also be facilely fine-modulated for photovoltaic application by adjusting the donor/acceptor ratios. UV-vis measurements showed that increasing the content of PQx units led to enhanced absorption. The band gaps obtained from UV-vis spectra, CV scanning, and DFT modeling all indicated a narrowing band gap with increasing the PQx content in the copolymer structure. The photovoltaic solar cells (PSCs) based on these copolymers were fabricated and tested with a structure of ITO/PEDOT:PSS/copolymer: PCBM/Ca/Al under the illumination of AM 1.5G, 100 mW cm À12 . The best performance was achieved using P3/[70]PCBM blend (1 : 3) with J sc ¼ 9.55 mA cm À2 , V oc ¼ 0.81 V, FF ¼ 0.42, and PCE ¼ 3.24%, which is the highest efficiency for the PQx and indolo [3,2-b]carbazole based devices. The present results also indicate that the efficient photovoltaic materials with suitable electronic and optical properties can be achieved by just fine-tuning the ratios of the strong electron-deficient accepters and large-p planar donors

Hydrogen release from carbon steel in chloride solution under anodic polarization

The hydrogen permeation current increase was noticed for carbon steel in 0.5 mol/L NaCl solution under strong anodic potentials, which is contrary to the common understanding. Hydrogen permeation under cathodic potentials has been widely studied because of possible hydrogen embrittlement failures of high strength steels in seawater, but investigations of anodic polarization on hydrogen permeation are fairly rare, as the hydrogen evolution reaction shall be retarded. To corroborate the observed phenomenon, experiments were conducted using both as-received and vacuum-annealed sheet specimens. It was verified that the observed phenomena originated from the released hydrogen in traps by metal dissolution under anodic polarization

interzeolitetransformationfromfautochaandmfizeolitesmonitoredbyuvramanspectroscopy

As a powerful and sensitive tool for the characterization of zeolite building units, UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites. The results show that the behavior of double 6-membered rings (D6Rs) in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation. For the transformation of FAU to CHA, because both zeolites contain the same D6R units, direct transformation occurs, in which the D6Rs were largely unchanged. In contrast, for the transformation of FAU to MFI, the D6Rs can be divided into two single 6-membered rings (S6Rs), which further assembled into the MFI structure. In this crystallization, 5-membered rings (5Rs) are only observed in the MFI framework formation, suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs. These insights will be helpful for further understanding of the interzeolite transformation

interzeolitetransformationfromfautochaandmfizeolitesmonitoredbyuvramanspectroscopy

As a powerful and sensitive tool for the characterization of zeolite building units, UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites. The results show that the behavior of double 6-membered rings (D6Rs) in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation. For the transformation of FAU to CHA, because both zeolites contain the same D6R units, direct transformation occurs, in which the D6Rs were largely unchanged. In contrast, for the transformation of FAU to MFI, the D6Rs can be divided into two single 6-membered rings (S6Rs), which further assembled into the MFI structure. In this crystallization, 5-membered rings (5Rs) are only observed in the MFI framework formation, suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs. These insights will be helpful for further understanding of the interzeolite transformation

A lightweight multifunctional interlayer of sulfur-nitrogen dual-doped graphene for ultrafast, long-life lithium-sulfur batteries

Lithium-sulfur batteries are a promising candidate for next-generation battery systems owing to their low cost and high theoretical capacity and energy density. However, the notorious shuttle effect of the intermediate polysulfides as well as low conductivity of sulfur greatly limits their practical applications. Here, we introduce a new design that uses a porous-CNT/S cathode (PCNT-S) coupled with a lightweight multifunctional porous sulfur-nitrogen dual-doped graphene (SNGE) interlayer. It is confirmed that the introduced SNGE has outstanding conductivity, high ability to trap polysulfides, ability to modulate Li2S2/Li2S growth, and the functionality to protect separator integrity. With such rich functionalities, the SNGE interlayer enables the PCNT-S cathode to deliver a reversible specific capacity of ∼1460 mA h g-1 at 0.25C and a much higher rate performance, up to 40C, with a capacity retention of 130 mA h g-1. Critically, these cathodes exhibited ultrahigh cyclability when cycled at 8C for 1000 cycles, exhibiting a capacity degradation rate of 0.01% per cycle. To the best of our knowledge, such a low capacity degradation rate beyond 5C in the cathodes of advanced Li-S batteries has been reported only rarely. These results impressively revealed the outstanding high-power output performance of the Li-S batteries

Sustainable Synthesis of Pure Silica Zeolites from a Combined Strategy of Zeolite Seeding and Alcohol Filling

Currently, the synthesis of pure silica zeolites always requires the presence of organic structure-directing agents (OSDAs), which direct the assembly pathway and ultimately fill the pore space. A sustainable route is now reported for synthesizing pure silica zeolites in the absence of OSDAs from a combined strategy of zeolite seeding and alcohol filling, where the zeolite seeds direct crystallization of zeolite crystals from amorphous silica, while the alcohol is served as pore filling in the zeolites. Very importantly, the alcohol could be fully washed out from zeolite pores by water at room temperature, which completely avoids calcination at high temperature for removal of OSDAs in the synthesis of pure silica zeolites