APPLIED CATALYSIS A-GENERAL
·
2011
·
IF 3.384
Hua Yang,Jia-Qi Chen,Jun Li,Ying Lv,Shuang Gao
Hydroxylation of benzene to phenol in the [(CH 3 ) 4 N] 4 PMo 11 VO 40 /ascorbic acid/TEMPO/O 2 catalytic system was carefully investigated. UV–vis, ESR and 1 H NMR studies showed ascorbic acid radicals were formed through the hydrogen exchange of ascorbic acid with TEMPO (2,2,6,6-tetramethyl-1-piperidine-N-oxyl radicals) during the reaction. In acetonitrile, the ascorbic acid would be partly oxidized to 2-hydroxy-2-buten-4-olide (α-tetronic acid, isotetronic acid, compound 1 ) without TEMPO. The interaction of TEMPO and ascorbic acid restrained the oxidative dissociation of ascorbic acid and promoted the rate of the hydroxylation. Aqueous acetic acid solvent can also restrain the oxidative dissociation of ascorbic acid. In aqueous acetic acid, the yield of phenol could reach 18.9% in the [(CH 3 ) 4 N] 4 PMo 11 VO 40 /ascorbic acid/TEMPO/O 2 catalytic system with sufficient ascorbic acid after 400 min.
研究领域:
催化化学
·
有机化学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2018
·
IF 4.439
Sizhao Zhang,Jian Feng,Junzong Feng,Yonggang Jiang,Feng Ding
Although carbon aerogels derived from naturally occurring materials have been developed extensively, a reasonable synthetic approach using cellulose-resource remains unclear. Here, we report a strategy to prepare carbon aerogels originated from cellulose position-selectively oxidized by TEMPO-oxidized process. Contrary to non-TEMPO-oxidized cellulose-derived carbon aerogels (NCCA) with relative loose structure, TEMPO-oxidized cellulose-derived carbon aerogels (TCCA) with tight fibrillar-continuous network are monitored, suggesting the importance of TEMPO-oxidized modification towards creating the architecture of subsequently produced carbon aerogels. TCCA endows a higher BET area despite owning slightly dense bulk density comparing with that of NCCA. The structural texture of TCCA could be maintained in a way in comparison to TEMPO-oxidized cellulose-derived aerogel, due to the integration and aggregation effect by losing the electric double layer repulsion via ionization of the surface carboxyl groups. FTIR and XPS analyses signify the evidence of non-functionalized carbon-skeleton network formation in terms of TCCA. Further, the mechanism concerning the creation of carbon aerogels is also established. These findings not only provide new insights into the production of carbon aerogels but also open up a new opportunity in the field of functional carbon materials.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2021
·
IF 6.953
Xiaotong Fu,Fulong Zhang,Cuihua Dong,Wenyuan Zhu,Kaifeng Xiong,Zhiqiang Pang
An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO 2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr·3.5H 2 O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO 2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13 C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CARBOHYDRATE POLYMERS
·
2012
·
IF 3.628
Xinwang Cao,Bin Ding,Jianyong Yu,Salem S. Al-Deyab
Cellulose nanowhiskers is a kind of renewable and biocompatible nanomaterials evoke much interest because of its versatility in various applications. Here, for the first time, a novel controllable fabrication of cellulose nanowhiskers from jute fibers with a high yield (over 80%) via a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO system selective oxidization combined with mechanical homogenization is reported. The versatile jute cellulose nanowhiskers with ultrathin diameters (3–10 nm) and high crystallinity (69.72%), contains C6 carboxylate groups converted from C6 primary hydroxyls, which would be particularly useful for applications in the nanocomposites as reinforcing phase, as well as in tissue engineering, pharmaceutical and optical industries as additives.
研究领域:
材料科学
·
生物医学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Processes
·
2024
·Vol. 12
·期 5
·1035
·
IF 2.8
Audrey Zahra,Virginia Ghita Firsty,Soo-Jeong Shin
Red ginseng extract is one of the most widely used herbal medicines to prevent and cure various diseases. Among the processed products derived from red ginseng, the water-insoluble part as red ginseng residual (RGR) becomes waste, even though it contains important ingredients. TEMPO-oxidation (TO) can be used as a pre-treatment with different degrees of oxidation (DO) (0 to 0.4) in red ginseng residual (RGR-TO) by introducing chemical oxidation and high-pressure homogenizer (HPH) as a nanofibrillation process.1H NMR was used to determine the carbohydrate composition and calculate DO, size was examined using a nanoparticle analyzer, and the zeta potential was used to determine surface charge density. RGR-TO with different concentrations had different compositions; glucose and uronic acid were the main ingredients. All treated RGR-TO showed higher oxidant levels than the untreated counterpart (RGR-TO 0). As the oxidant levels increased, the zeta potential and uronic acid increased, but the size of the nanofibril from RGR-TO decreased. The results of this study showed that TEMPO-oxidation pretreatment was effective in producing RGR cellulose nanofibril (CNF) with a variety of properties by adjusting the level of oxidation pretreatment and the number of HPH passes.
研究领域:
植物化学
·
药用植物学
·
纳米材料科学
✓ 已验证
产品关联
DOI
高影响因子
CELLULOSE
·
2021
·Vol. 29
·期 1
·213-222
·
IF 5.044
Fan Fangwei,Zhu Mengting,Fang Kaiyang,Cao Endi,Yang Yinzhi,Xie Jinpeng,Deng Zhongmin,Chen Yiren,Cao Xinwang
Cellulose nanowhiskers as one kind of renewable and biocompatible nanomaterials evoke much interest because of its versatility in various applications. Herein, the sisal cellulose nanowhiskers with ultrathin diameter of 5–10 nm, high crystallinity of 74% and C6 carboxylate groups converted from C6 primary hydroxyls were prepared via a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO system selective oxidization combined with mechanical homogenization. The effects of sodium hydroxide concentration in alkali pretreatment on the final sisal cellulose nanowhiskers were explored. It was found that with the increase of sodium hydroxide concentration, the sisal fiber crystalline type would change from cellulose I to cellulose II. The versatile sisal cellulose nanowhiskers would be particularly useful for applications in the nanocomposites as reinforcing phase, as well as in tissue engineering, filtration, pharmaceutical and optical industries as additives.
研究领域:
材料科学
·
生物材料学
✓ 已验证
产品关联
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2016
·
IF 4.219
Jie Hao,Jiaojiao Lu,Naiyu Xu,Robert J. Linhardt,Zhenqing Zhang
Oxidized starch, one of the most important starch derivatives, has many different properties and applications. Currently, there are two ways to produce oxidized starch, through specific and nonspecific oxidation. Specific oxidation using the stable nitroxyl radical, 2,2,6,6-tetramethyl preparidinloxy (TEMPO), with NaBr and NaClO can produce oxidized starches with different properties under good quality control. In the current study, we examine the products of specifically oxidized starch. As the amount of oxidant and the temperature, two critical factors impacting the oxidation of starch were thoroughly investigated. Analysis of the molecular weight (MW), degree of oxidization (DO) and the detailed structures of corresponding products was accomplished using gel permeation chromatography with multi-angle laser light scattering (GPC-MALLS), infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and quadrapole time-of-flight mass spectrometry (Q/TOF-MS). According to the analytical results, the oxidation patterns of starch treated with specific oxidant TEMPO-NaBr-NaClO were established. When high amounts of oxidant was applied, more glucose residues within starch were oxidized to glucuronic acids (higher DO) and substantial degradation to starch oligosaccharides was observed. By selecting a reaction temperature of 25 °C a high DO could be obtained for a given amount of oxidant. The reducing end sugar residue within oxidized starch was itself oxidized and ring opened in all TEMPO-NaBr-NaClO reactions. Furthermore, extra oxidant generated additional novel structures in the reducing end residues of some products, particularly in low temperature reactions.
研究领域:
食品科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Scientific Reports
·
2016
·Vol. 6
·期 1
·1-9
·
IF 5.228
Ji Lvlv,Dai Yuyu,Yan Shuanma,Lv Xiaojing,Su Chang,Xu Lihuan,Lv Yaokang,Ouyang Mi,Chen Zuofeng,Zhang Cheng
A novel strategy to obtain rapid electrochromic switching response by introducing 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) moiety into polytriphenylamine backbone has been developed. The electrochromic properties of the integrated polymer film are investigated and a possible mechanism is proposed with TEMPO as a counterion-reservoir group to rapidly balance the charges during electrochromic switching, which leads to significantly improved electrochromism performance.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACS Omega
·
2023
·
IF 4.1
Bei Jiang,Meilin Li,Shuoang Cao,Zining Wang,Lijun Huang,Xinyi Song,Yuanqiao Zhang,Quanping Yuan
In order to increase the number and contact probability of electric dipole on cellulose, acid and alkali treatment was employed to extract hemicellulose and lignin from original wood to gain a highly oriented cellulose frame. The combined means with 2,2,6,6-tetramethylpiperidine-1-oxyl–NaBr–NaClO oxidation and impregnation of PDMS with compression was subsequently used to enhance its mechanical performance and electromechanical conversion. The assembled wooden electromechanical device (10 mm × 10 mm × 1 mm) exhibits the maximum open-circuit voltage (VOC) of 11.75 V and short-circuit current (ISC) of 211.01 nA as stepped by foot. It can be sliced to fabricate a flexible sensor with high sensitivity displaying VOC of 2.88 V and ISC of 210.09 nA under the tapped state. Its highly oriented wood fiber makes it display significant anisotropy in terms of mechanical and electromechanical performance for multidirectional sense. This strategy will exactly provide reference for developing other high-performance piezoelectric devices.
研究领域:
材料科学
·
生物工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Energy Material Advances
·
2021
·
IF 0
Shuzhi Hu,Liwen Wang,Xianzhi Yuan,Zhipeng Xiang,Mingbao Huang,Peng Luo,Yufeng Liu,Zhiyong Fu,Zhenxing Liang
A novel electroactive organic molecule, viz., 1-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-1′-(3-(trimethylammonio)propyl)-4,4′-bipyridinium trichloride ((TPABPy)Cl3), is synthesized by decorating 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) with viologen, which is used as the positive electrolyte in neutral aqueous redox flow battery (ARFB). Extensive characterizations are performed to investigate the composition/structure and the electrochemical behavior, revealing the favorable effect of introducing the cationic viologen group on the electroactive TEMPO. Salient findings are as follows. First, the redox potential is elevated from +0.745 V for TEMPO to +0.967 V for decorated TEMPO, favoring its use as the positive electrolyte. Such an elevation originates from the electron-withdrawing effect of the viologen unit, as evidenced by the nuclear magnetic resonance and single crystal structure analysis. Second, linear sweep voltammetry reveals that the diffusion coefficient is 2.97×10−6 cm2 s−1, and the rate constant of the one-electron transfer process is 7.50×10−2 cm s−1. The two values are sufficiently high as to ensure low concentration and kinetics polarization losses during the battery operation. Third, the permeability through anion-exchange membrane is as low as 1.80×10−11 cm2 s−1. It is understandable as the positive-charged viologen unit prevents the molecule from permeating through the anion exchange membrane by the Donnan effect. Fourth, the ionic nature features a decent conductivity and thus eliminates the use of additional supporting electrolyte. Finally, a flow battery is operated with 1.50 M (TPABPy)Cl3 as the positive electrolyte, which affords a high energy density of 19.0 Wh L-1 and a stable cycling performance with capacity retention of 99.98% per cycle.
研究领域:
化学
·
能源科学
✓ 已验证
DOI
Molecular Catalysis
·
2023
·
IF 4.6
Pei-Sen Gao,Chang-Wang Pan,Cheng Liu,Wen-Tong Chen
Asymmetric electrocatalysis is poised to provide a unique avenue for access to enantioenriched molecules that are difficult to obtain through more conventional approaches, but the development of efficient electrocatalysts capable of highly enantioselective transformations remains elusive. Towards this enviable end, bifunctional electrocatalyst capable of both redox mediation and delivery of high stereocontrol is needed. Here we disclose a novel TEMPO-BOX-ligated copper electrocatalyst that enables oxidative kinetic resolution of racemic 1,4-diols, affording diverse chiral 1,4-diols and γ-lactones with good or excellent chemo-, regio, and enantioselectivity. We also show that this cooperative Cu/TEMPO-BOX catalytic strategy is applicable to the electro-oxidative kinetic resolution of 1,2- and 1,3-amino alcohols. This work demonstrates the potential of bifunctional electrocatalysis for asymmetric synthetic methods and we anticipate that it will spur the development of new hybrid electrocatalysts to realize novel asymmetric electrocatalytic methods.
研究领域:
有机化学
·
电化学
·
催化
·
合成化学
✓ 已验证
DOI
高影响因子
ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2021
·
IF 9.028
Honglong Zhang,Zhenyu Shi,Ruopeng Bai,Dingxiang Wang,Fuyi Cui,Jing Zhang,Timothy J. Strathmann
Permanganate (Mn(VII)) has been widely applied as an oxidant in water treatment plants. However, compared with ozone, Fenton, and other advanced oxidation processes, the reaction rates of some trace organic contaminants (TrOCs) with Mn(VII) are relatively low. Therefore, further studies on the strategies for enhancing the oxidation of organic contaminants by Mn(VII) are valuable. In this work, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), as an electron shuttle, enhanced Mn(VII) oxidation toward various TrOCs (i.e., bisphenol A (BPA), phenol, estrone, sulfisoxazole, etc.). TEMPO sped up the oxidative kinetics of BPA by Mn(VII) greatly, and this enhancement was observed at a wide pH range of 4.0–11.0. The exact mechanism of TEMPO in Mn(VII) oxidation was described briefly as follows: (i) TEMPO was oxidized by Mn(VII) to its oxoammonium cation (TEMPO+) by electron transfer, which was the reactive species responsible for the accelerated degradation of TrOCs and (ii) TEMPO+ could decompose TrOCs rapidly with itself back to TEMPO or TEMPOH (TEMPO hydroxylamine). To further illustrate the interaction between TEMPO and target TrOCs, we explored the transformation pathways of BPA in Mn(VII)/TEMPO oxidation. Compared to Mn(VII) alone, adding TEMPO into the Mn(VII) solution significantly suppressed BPA’s self-coupling and promoted hydroxylation, ring-opening, and decarboxylation. Moreover, the Mn(VII)/TEMPO system was promising for the abatement of TrOCs in real waters for humic acid, and ubiquitous cations/anions had no adverse or even beneficial impact on the Mn(VII)/TEMPO system.
研究领域:
环境科学
·
化学工程
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）