RSC Advances
·
2015
·Vol. 5
·期 56
·44783-44791
·
IF 3.84
Rui Zhang,Baochang Zhang,Shuqing Sun
In this paper, we report on the successful preparation of high-quality graphene sheets with a large-size in N,N-dimethylformamide (DMF) solvent by sonication-free liquid-phase exfoliation (LPE) of graphite assisted with urea as the precursor of the intercalating agent melamine. Through the characterizations of the graphene sheets obtained with transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and XPS, these graphene sheets were found to be high-quality, defect-free, single or-few-layer with areas in the range of 100–1000 μm2. The influences of reflux time and the mass ratio of urea to graphite on the graphene concentration (CG) in the resulting dispersions were investigated. The graphene dispersions were fabricated into flexible films that show comparable conductivity. The exfoliation mechanism of graphite in our new sonication-free LPE method is also discussed.
研究领域:
材料科学
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纳米技术
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产品关联
DOI
高影响因子
CHEMISTRY OF MATERIALS
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2020
·
IF 9.567
Stephen V. Kershaw,Wai Kin Yiu,Aleksandr Sergeev,Andrey L. Rogach
Most successful syntheses of long-wavelength infrared (IR)-absorbing/emitting Hg-chalcogenide quantum dots (QDs) use either aqueous- or organic-solvent-based methods. Accounts of IR QD growth in aprotic solvents such as dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) are much less common, and yet, producing QDs in such solvents can be useful from the perspective of further reactions to conjugate or incorporate the QDs with other materials since such solvents can be a useful meeting ground for both organic and ionic solutes. Here, we start by demonstrating long-wavelength infrared emission (across the wide spectral range of up to 4500 nm) in HgTe QDs grown in DMF under basic conditions. While many existing synthetic approaches use soluble chalcogen precursors in adduct, salt, or organo-chalcogenide forms, we have opted to take the approach of using slow addition of gaseous H2Te generated under programmed control, which allowed us to investigate the growth kinetics to manipulate the different competing processes and to obtain larger HgTe QDs with the best size distributions on a repeatable and controlled basis. We demonstrate how the nucleation process of HgTe QDs can be carried out analogously to the way that it occurs in classic hot injection syntheses but in our case at a far lower (subambient) temperature, owing to the use of a much more labile Te precursor. We also demonstrate the use of a two-stage, seeded QD growth process, which allows the synthesis conditions for the initial nucleation step and the subsequent enlargement stage to be decoupled; in other words, the QD concentration during the enlargement phase need not be forced to be excessively large by the choice of nucleation conditions. This approach should eventually be extendable to making >5000 nm emitting HgTe QD-based materials, and the use of aprotic solvents will offer compatibility with other nanomaterial chemistries, e.g., oxide glass formers, etc., for the synthesis of composites. By comparing the emission spectra of HgTe QDs grown in DMF with the spectra of those grown in DMSO, we show that polaron-mediated coupling to ligands and solvents, previously seen when using DMSO, can be substantially suppressed using our new synthetic method.
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
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2021
·
IF 10.588
Jiaxin Zhu,Yihua Chen,Yurong Gu,Hang Ma,Mingyue Hu,Xinlei Gao,Tongzhou Liu
The discharge of widely used per- and poly-fluorinated compounds (PFCs) leads to their environmental prevalence, bioaccumulation and biotoxicity; and attracts researches focusing on their treatment in wastewater. Electrochemical reductive treatment is a promising alternative due to its milder reaction conditions and easy operation. The feasibility of electrochemical reductive decomposition of PFOA using a Rh/Ni cathode was explored. The Rh/Ni cathode was fabricated by coating Rh 3+ on Ni foil through electrodeposition . The Rh coating was primarily elemental and in a Rh(111) crystalline form. PFOA decomposition and defluorination were observed when using the Rh/Ni cathode where DMF was the solvent and the cathode potential was −1.25 V. A hydrodefluorination reaction was considered having occurred. Because possessing d electrons and empty d orbitals, the Rh coating enhanced PFOA adsorption onto the cathode surface and facilitated C F bond activation through Rh···F interactions. Moreover, the Rh(111) crystal helped chemisorb the generated H* and supply it participating in PFOA decomposition. With the continuous interaction of cathode-supplied electrons, C F bond would ultimately dissociate and transform to C H bond by H* substitution. Adding FeCp 2 * as a supporting electrolyte enhanced PFOA decomposition by working as the shuttle facilitating PFOA migration to the cathode surface.
研究领域:
环境科学
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电化学
·
污染治理
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产品关联
DOI
PubMed
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2018
·
IF 3.141
Yongwei Chen,Houxiao Wu,Zewei Liu,Xuejiao Sun,Qibin Xia,Zhong Li
Mechanochemical synthesis, driven the chemical transformation by mechanical force, has been a rapid and efficient strategy to prepare metal–organic frameworks (MOFs). In this work, a liquid-assisted mechanochemical method has been successfully applied to the synthesis of copper based MOF-505. The crystallinity and porosity of MOF-505 were investigated by adjusting the synthesis parameters, such as added solvent (type and amount) and grinding time. Results showed that the type and amount of added solvent were crucial parameters for the mechanochemical synthesis of MOF-505. Furthermore, the optimizations of MOF-505 synthesis were carried out: grinding Cu(OAc)2·H2O and H4bptc as starting materials for 80 min with 0.4 mL of DMF assisted, giving MOF-505-K with Brunauer–Emmett–Teller (BET) surface area of 977 m2/g. Meanwhile, MOF-505-K had moderate CO2 adsorption capacity of 2.01 mmol/g at 298 K and 100 kPa. The adsorptive selectivity determined from ideal adsorbed solution theory (IAST) indicated that MOF-505-K had high CO2/N2 and CO2/CH4 selectivities (26.6 and 5.5) at 298 K. Highly efficient mechanochemical synthesis of MOF-505 provides the promise to facilitate the industrial application of CO2 capture.
研究领域:
材料科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
ENERGY & FUELS
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2017
·
IF 3.091
Jun Cheng,Yannan Li,Leiqing Hu,Jianzhong Liu,Junhu Zhou,Kefa Cen
A phase-change solvent for CO2 absorption was prepared by mixing N-methyl-1,3-diaminopropane (MAPA) and N,N-dimethylformamide (DMF). In this MAPA/DMF solvent, MAPA-carbamate precipitate was formed after CO2 absorption to facilitate reducing energy consumption of amine regeneration. The CO2 uptake of MAPA/DMF solvent (14.8 mg/g solvent) was increased by 22% compared with that of MAPA/water solvent (12.1 mg/g solvent). For MAPA/DMF solvent, time was reduced by 22% to reach the CO2 absorption equilibrium. The maximum CO2 uptake rate of MAPA/DMF solvent was 30% higher than that of MAPA/water solvent because DMF displayed higher CO2 solubility and lower MAPA-carbamate solubility than water. Differential scanning calorimetry and thermogravimetry experiments revealed that MAPA(H+)2 and MAPA(CO2–)2 compositions in MAPA-carbamate precipitate first decomposed (peak temperature = 59.9 °C). Subsequently, the MAPACO2 compositions in precipitate also decomposed (peak temperature = 124.2 °C).
研究领域:
化学工程
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环境科学
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DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2021
·
IF 8.271
Lutian Zhao,Yangge Guo,Cehuang Fu,Liuxuan Luo,Guanghua Wei,Shuiyun Shen,Junliang Zhang
In this work, highly monodispersed Pt-Ni alloy nanoparticles were directly deposited on carbon substrate through a facile electrodeposition strategy in the solvent system of N,N -dimethylformamide (DMF). A series of carbon supported Pt-Ni alloy electrocatalysts were synthesized under different applied electrode potentials. Among all as-obtained samples, the Pt-Ni/C electrocatalyst deposited at –1.73 V exhibits the optimal specific activity up to 1.850 mA cm −2 at 0.9 V vs . RHE, which is 6.85 times higher than that of the commercial Pt/C. Comprehensive physiochemical characterizations and computational evaluations via density functional theory were conducted to unveil the nucleation and growth mechanism of PtNi alloy formation. Compared to the aqueous solution, DMF solvent molecule must not be neglected in avoiding particle agglomeration and synthesis of monodispersed nanoparticles. During the alloy co-deposition process, Ni sites produced through the reduction of Ni(II) precursor not only facilitates Pt-Ni alloy crystal nucleation but also in favor of further Pt reduction on the Ni-inserted Pt surface. As for the deposition potential, it adjusts the final particle size. This work provides a hopeful extended Pt-based catalyst layer production strategy for proton exchange membrane fuel cells and a new idea for the nucleation and growth mechanism exploration for electrodeposited Pt alloy.
研究领域:
材料科学
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催化化学
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燃料电池研究
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产品关联
DOI
高影响因子
ChemSusChem
·
2025
·
IF 6.6
Umar Farooq,Boyang Han,Usman Ali Shah,Fa Yang,Sheng Li,Yanping Song,Ali Hassan,Zhengquan Li,Jin Wang
The efficiency of earth-abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells has been lagging behind the Shockley-Queisser limit primarily due to the presence of deep-level defects. These deep-level defects cause critical issues such as short carrier diffusion length, significant band tailing, and a large open-circuit voltage (VOC) deficit, ultimately leading to low device efficiency. To address these issues, we propose a post-fabrication defect healing strategy by dip-coating the CZTSSe film in dimethylformamide (DMF) solvent. Immersing the absorber layer in DMF (a polar solvent), neutralizes CuSn antisite defects through chemical bonding and facilitates the formation of a dense, smooth CZTSSe film with larger grain size. Deep-level transient spectroscopy revealed a remarkable increase in carrier diffusion length from 93 nm (control device) to 142 nm (champion device), confirming the beneficial effect of solvent-assisted post-treatment on mitigating CuSn antisite defects. The reduction in defect densities led to a decrease in VOC deficit by up to 289 mV, accompanied by an increased champion device efficiency of 11.4%. This work highlights the huge potential of the DMF post-treatment strategy for defect healing in CZTSSe solar cells.
研究领域:
材料科学
·
能源工程
·
半导体物理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）