CELLULOSE
·
2018
·Vol. 25
·期 3
·1809-1819
·
IF 3.809
Xiao He,Zhang Weibo,Wei Yicui,Chen Lihui
Zinc oxide (ZnO) is among the most interesting metal oxide with remarkable performance in electronics, semiconducting materials and photocatalysis, specially as nanomaterials. In this work, carbon/ZnO nanocomposites were designed using a low temperature precipitation process and TEMPO-oxidized (2,2,6,6-Tetramethyl-1-piperidinyloxy as TEMPO) cellulose as a reactive template. The resulting nanomaterials were characterized by XRD, SEM, TEM, BET, EDX and UV–vis spectroscopy analysis. It was found that the formation of carbon/ZnO nanocomposites with various morphologies not only involved the structure of TEMPO-oxidized cellulose but also depended on the content of the carboxyl groups of TEMPO-oxidized cellulose. In this approach, TEMPO-oxidized cellulose is not only a template provider, but is a C-provider leading to a compound into the ZnO nanocrystals which were decreased the band gaps of samples. ZnO-T12 exhibited a significant photodegradation on methyl orange with 96.11% within 120 min and good reusability.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
RESEARCH ON CHEMICAL INTERMEDIATES
·
2018
·Vol. 45
·期 2
·549-561
·
IF 1.674
Liu Wanghui,Yang Jianhong,Cai Jun
An environmentally benign CuO-rectorite was prepared by calcining the co-precipitation product of Cu 2+ with an acid-activated rectorite at pH 6. It could be well dispersed in water and used as a co-catalyst with TEMPO to selectively aerobically oxidize alcohols to aldehydes. The conversion of most primary benzylic alcohols was very high under optimized conditions. Interestingly, the oxidation protocol also allowed highly selective transformation of benzylic alcohols containing a phenolic hydroxyl group into the corresponding aldehydes. Additionally, very little copper was leached from the catalyst during the catalytic reaction. CuO-rectorite could be reused by centrifugation and washed with acetonitrile and water. At the same time, its catalytic activity remained high.
研究领域:
催化
·
有机化学
·
环境科学
✓ 已验证
DOI
高影响因子
CELLULOSE
·
2017
·Vol. 24
·期 6
·2415-2425
·
IF 3.417
Sang Xiankui,Qin Chengrong,Tong Zhangfa,Kong Song,Jia Zhuan,Wan Guangcong,Liu Xinliang
2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) can selectively oxidize primary hydroxyl groups of cellulose to carboxyl groups. However, the depolymerization also occurs during the process. The kinetics and mechanism of carboxyl group formation on the surface of cellulose fiber oxidized by TEMPO/NaClO 2 /NaClO were discussed. The oxidization and depolymerization of cellulose occurred simultaneously, according to analysis of FTIR and 13 C CP/MAS NMR. The glucuronic acid and some small molecular fragments, formed by hydrolysis or β-elimination during the oxidation, are also discussed. The crystallization index increased and crystal size decreased, as shown by X-ray analysis. The degradation steps in the TEMPO/NaClO 2 /NaClO system was discussed, according to carbon conversion analyzed by 13 C CP/MAS NMR. The oxidation of cellulose can be described well by the kinetics model established based on the degradation of cellulose. It was found that temperature is one of the key parameters for controlling the oxdation and degradation level. The possible mechanism for oxidation of cellulose was composed.
研究领域:
化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
TETRAHEDRON
·
2023
·
IF 2.1
Zhiwei Wang,Rong Zhao,Jia Lin,Chaoyang Liu,Qiang Jia,Changhu Chu
A highly efficient and Tempo-free catalytic aerobic alcohol oxidation method has been developed using charcoal-supported Cu 0 nanoparticles（Cu-A） in conjunction with pyridine. Various alcohols, bearing different functional groups, can be readily oxidized to their corresponding ketones and aldehydes under mild conditions.
研究领域:
化学
·
催化
·
有机合成
✓ 已验证
DOI
高影响因子
Journal of Macromolecular Science Part A-Pure and Applied Chemistry
·
2019
·
IF 1.163
Weitao He,Qi Sun,Xianliang Song
In this study, the agricultural by-products of corn production (corncobs) were ground into a powder form. Then, the powder was treated with sodium chlorite to remove the lignin, and the remaining holocellulose was optionally modified with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated oxidation. The resulting product was examined using an elemental analysis, along with Fourier transform infrared spectroscopy (FTIR). The effects of the oxidation time and dosages of the TEMPO on the paper’s physical properties were investigated. The results indicated that the TEMPO-mediated oxidized corncob holocellulose had the ability to improve the properties of both paper and recycled paper. When 1.0% oxidized holocellulose was used, the resulting tensile index, burst index, and folding endurance were increased by 4.16%, 8.63%, and 50.71%, respectively, compared with the control paper. The SEM analysis indicated that the bonding between fibers was improved by adding oxidized corncob holocellulose. Compared with the control paper, it was determined that the proportion of mesopore within the fibers increased and the bonding of the C–O bonds increased in the paper with the oxidized corncob holocellulose. The results of this study may potentially provide guidance for the future high value-added application of corncobs as a paper strengthening agent.
研究领域:
生物质材料
·
造纸工程
·
高分子化学
·
农业资源利用
·
绿色化学
✓ 已验证
DOI
高影响因子
Journal of Physical Chemistry C
·
2019
·
IF 4.309
Kecheng Hu,Jun Tang,Shixiong Cao,Qi Zhang,Jianli Wang,Zhibin Ye
We report in this paper the design and synthesis of a pH-responsive polymeric interfacial catalyst (PIC) via one-step grafting of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) onto a polyaryletherketone having pendant benzimidazole groups (SCBI-PAEK-6F). The TEMPO-functionalized polymer has been systematically characterized with 1H nuclear magnetic resonance, Fourier-transform infrared spectroscopy, elemental analysis, contact angle, and transmission electron microscopy. Moreover, this well-designed polymer has been applied in the oxidation of alcohols under Montanari conditions. It is found that the functionalized polymer can aggregate at the water–oil interface and act as an efficient stabilizer to facilitate the formation of a stable Pickering emulsion, which shows outstanding catalytic activity for alcohol oxidation through the microreactor mechanism. Moreover, the PIC is featured with desirable high pH responsiveness due to the valuable benzimidazole groups. De-emulsification of the Pickering emulsion reaction system can be conveniently triggered by simply tuning the system pH value to 3, thus facilitating the facile recovery of the PIC. In addition, the sustainable catalyst can be reused for subsequent cycles of alcohol oxidation without appreciable loss in catalytic activity or selectivity.
研究领域:
材料化学
·
催化化学
·
有机合成
✓ 已验证
产品关联
DOI
高影响因子
CELLULOSE
·
2014
·Vol. 21
·期 6
·4557-4567
·
IF 3.033
Feng Jin,Shi Qingshan,Li Wenru,Shu Xiulin,Chen Aimei,Xie Xiaobao,Huang Xiaomo
In order to improve the antimicrobial activity of bacterial cellulose (BC), the silver nanoparticles (Ag NPs) were in situ fabricated on the BC membranes, affording BC and Ag hybrid antimicrobial materials, BC + Ag, which possesses excellent antimicrobial performance. Typically, carboxyl groups were firstly introduced into BC by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation. Then, the carboxyl-functionalized BC was performed with ion-exchange reaction to change the sodium ions into Ag + by immersing in AgNO 3 aqueous solution, generating Ag + anchored BC. Finally, two types of distinct reductive reagents including NaBH 4 and sodium citrate were employed to transform Ag + into Ag NPs to fabricate BC + Ag. The diameters of Ag NPs were determined to be 3.8 nm for NaBH 4 -reduced BC + Ag, and 22.0 nm for sodium citrate-reduced one, respectively. The silver content of BC + Ag were determined to be 1.944 and 2.895 wt% for NaBH 4 -reduced sample and sodium citrate-reduced one, respectively. Two types of BC + Ag both showed a slow and persistent Ag + release profile, but the NaBH 4 -reduced one released much more Ag + than that of sodium citrate under the same measurement condition. In-depth antibacterial analysis via the disc diffusion and colony forming count method disclosed that BC + Ag exhibited strong bactericidal effects against both Escherichia coli and Staphylococcus aureus . And the antibacterial activity of NaBH 4 -reduced BC + Ag was higher than the sodium citrate-reduced one. Overall, this study would further improve the antibacterial efficiency of BC + Ag.
研究领域:
材料科学
·
微生物学
✓ 已验证
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2012
·
IF 3.628
Xinwang Cao,Bin Ding,Jianyong Yu,Salem S. Al-Deyab
Cellulose fibers deposited with metallic nanoparticles as one kind of renewable, biocompatible and antimicrobial nanomaterials evoke much interest because of their versatility in various applications. Herein, for the first time, a facile, simple and rapid method was developed to fabricate TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) selectively oxidized jute fibers in situ deposited with silver nanoparticles in the absence of reducing reagents. The average size of silver nanoparticles deposited on the fibers is 50.0 ± 2.0 nm by microwave heating for 5 min and 90.0 ± 4.7 nm for 10 min heating sample, respectively. The versatile jute–silver nanoparticles nanocomposites with superior thermal stability and high crystallinity would be particularly useful for applications in the public health care and biomedical fields.
研究领域:
材料科学
·
生物医学
✓ 已验证
DOI
PubMed
高影响因子
MACROMOLECULES
·
2017
·
IF 5.835
Jiaxing Zhang,Hongying Shen,Wenguang Song,Guowei Wang
A series of novel linear and hyperbranched copolymers with different topological structures and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical distributions were synthesized, and their paramagnetic property was systematically investigated. Based on the ring-opening polymerization (ROP) mechanism of GTEMPO, glycidol (Gly) or ethylene oxide (EO) monomers, the linear Poly(EO-co-GTEMPO) and hyperbranched Poly(Gly-co-GTEMPO) copolymers were obtained from a bifunctional 2,2-dimethyl-1,3-propanediol initiator and a tetrafunctional pentaerythritol initiator, respectively. Alternatively, from the multifunctional macroinitiator of hyperbranched polyglycerol (HPG), the hyperbranched HPG-g-Poly(Gly-co-GTEMPO) and HPG-g-PGTEMPO copolymers were also targeted. The copolymers were characterized by GPC, DSC, and UV–vis analysis. The paramagnetic property of the copolymers was studied and compared by EPR analysis at different concentrations of copolymers and temperatures. The results displayed that the concentrations of copolymers majorly manipulated the signal intensity of EPR spectra, and the temperature majorly modulated the shape of EPR spectra. Essentially, the TEMPO radical distributions in copolymers played an important role: the higher regional density tended to give the EPR spectra with intense, broad peaks, while the lower one led to the regular, well-pronounced EPR spectra. The difference was rationalized to different intramolecular spin–spin exchange and dipole–dipole interaction modulated by the topological structures and the corresponding TEMPO radical distributions.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
CELLULOSE
·
2025
·
IF 4.8
Zhao Yao,Wang Xueping,Li Bowen,Si Tian,Gao Xin,Peng Lincai,Zhang Heng
The cellulose catalytic oxidation system mainly comprises inorganic ion-based oxidants. Hence, the selective oxidation of C 6- primary hydroxy groups (C 6 -OH) of cellulose, catalyzed by piperidine free radicals, was limited to the homogeneous cellulosic system containing protic solvents or heterogeneous system. In this work, the use of the catalytic system containing 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (4-AcNH-TEMPO) was extended to the cellulosic solution in N, N-dimethylacetamide (DMAc) and combined with chlorine dioxide. Results showed that the carboxyl content was 0.832 mmol/g. Meanwhile, the degree of polymerization decreased from 900 to 489. This study provides an effective route for the homogeneous selective oxidation of primary hydroxy groups in cellulose and explored its oxidation mechanism in DMAc solvent. Furthermore, studies showed that the reactive chlorine species- ClO·, Cl·, and ClO 2 played a crucial role in the oxidation process. The methodology developed here displayed great potential to be utilized to various biomolecules in aprotic solvents homogeneous system based on 4-AcNH-TEMPO as oxidation catalysts.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Jing Luo,Chenghao Zhang,Wei Liu,Bingqi Xie,Jisong Zhang
2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has vital applications in the field of multiphase reaction, especially for the aerobic oxidation of alcohols. Activated carbon (AC) has a porous structure, rigid surface property, and low cost, which was the prominent carrier for TEMPO immobilization to produce the heterogeneous catalyst. However, the brilliant strategy of TEMPO immobilization on AC for long-term aerobic oxidation of alcohols was still challenging. In this work, surface-formylation and reductive amination were conducted to achieve the covalent TEMPO grafting on AC, which opened up a novel routine for surface modification and preparing heterogeneous catalysts based on carbon materials. The catalysts were packed in a micro-packed bed reactor to perform continuous aerobic oxidation of various alcohols. The catalytic performance of benzyl alcohol to benzaldehyde (turnover number: 1160.6, turnover frequency: 99.6 h −1 ) was much superior to those in the literature by using covalently grafted heterogeneous TEMPO catalysts.
研究领域:
化学工程
·
催化材料
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NANOPARTICLE RESEARCH
·
2020
·Vol. 22
·期 6
·1-11
·
IF 2.132
Sun Tingting,Liang Huazhe,Liu Shaojie,Tang Erjun,Fu Cuiyan
Magnetic nanoparticles (MNPs) modified by polyamidoamine (PAMAM)-immobilized 2,2,6,6-tetramethyl-1-piperidinyl-oxyl (TEMPO) as recoverable catalysts for catalytic oxidation of polyethylene glycol were designed and prepared, which were expected to combine the advantages of easy recovery of MNPs and high activity of PAMAM-immobilized TEMPO. The catalysts of MNPs modified by PAMAM-immobilized TEMPO (MNPs-PAMAM-T) were characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analyzer (TGA), and transmission electron microscopy (TEM). The mean particle size of MNPs was about 10 nm. MNPs-PAMAM-T/NaBr/NaClO was used as catalytic system for catalytic oxidation of monomethoxy poly (ethylene glycol). The catalytic performances were affected by the loading amounts of TEMPO and PAMAM generations. It was shown that the catalyst with TEMPO loading of 5.198 mmol/g using G2.0 PAMAM-modified MNPs as carrier had the best catalytic performance, which could be up to 94% of the free TEMPO level. The efficient recovery of catalyst could be achieved by magnetic separation and the recycling performance was good.
研究领域:
化学工程
·
材料科学
·
催化反应
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）