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排序方式: 共有4266条查询结果,搜索用时 31 毫秒
61.
Dr. Ting Ouyang Sheng Huang Xiao-Tong Wang Prof. Zhao-Qing Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(62):14024-14035
One of the most effective ways to cope with the problems of global warming and the energy shortage crisis is to develop renewable and clean energy sources. To achieve a carbon-neutral energy cycle, advanced carbon sequestration technologies are urgently needed, but because CO2 is a thermodynamically stable molecule with the highest carbon valence state of +4, this process faces many challenges. In recent years, electrochemical CO2 reduction has become a promising approach to fix and convert CO2 into high-value-added fuels and chemical feedstock. However, the large-scale commercial use of electrochemical CO2 reduction systems is hindered by poor electrocatalyst activity, large overpotential, low energy conversion efficiency, and product selectivity in reducing CO2. Therefore, there is an urgent need to rationally design highly efficient, stable, and scalable electrocatalysts to alleviate these problems. This minireview also aims to classify heterogeneous nanostructured electrocatalysts for the CO2 reduction reaction (CDRR). 相似文献
62.
在新陈代谢过程中, 机体会产生大量以自由基为主要形式的氧化活性物质, 而抗氧化剂可以通过电子转移的方式捕获并中和自由基, 从而有效抵御自由基引起的细胞损害, 以保障和维护人体健康. 食品作为人体外源性抗氧化剂的重要来源可以有效补充因体内代谢及体液排出而损失的抗氧化物质, 因此对食品中抗氧化物质消除自由基的能力即抗氧化能力的测定和评价具有重要意义. 光电化学技术作为一种简单快捷、 低成本、 低背景且高灵敏度的测定方法, 能够有效克服光学法、 色谱法和电化学法等传统测试手段在抗氧化容量分析中的不足. 本文综述了基于半导体及其复合材料的光电化学传感平台的构建及食品体系抗氧化容量分析的研究进展, 评论了多种检测体系的特点并对其研究前景进行了展望. 相似文献
63.
《中国化学快报》2020,31(8):2099-2102
In this work, the two-dimensional MoS2 film was prepared by sulfuring the molybdenum atomic layer on SiO2/Si substrate. The reaction temperature, heating rate, holding time and carrier gas flow rate were investigated comprehensively. The quality of MoS2 film was characterized by optical microscopy, atomic force microscopy, Raman and photoluminescence spectroscopy. The characterization results showed that the optimum synthesis parameters were heating rate of 25 °C/min, reaction temperature of 750 °C, holding time of 30 min and carrier gas velocity of 100 sccm. The MoS2 gas sensor was fabricated and its gas sensing performance was tested. The test results indicated that the sensor had a good response to both reducing gas (NH3) and oxidizing gas (NO2) at room temperature. The sensitivity to 100 ppm of NO2 was 31.3%, and the response/recovery times were 4 s and 5 s, respectively. In addition, the limit of detection could be as low as 1 ppm. This work helps us to develop low power and integrable room temperature NO2 sensors. 相似文献
64.
《中国化学快报》2020,31(8):2155-2158
Detection of trace-level hydrogen sulfide (H2S) gas is of great importance whether in industrial production or disease diagnosis. This research presents a novel H2S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H2S in real-time. The sensor consists of two integrated resonant microcantilever sensors with different functions. One cantilever sensor can identify H2S by outputting positive frequency shift signals, while the other cantilever sensor will detect H2S as a normally used cantilever sensor with negative frequency shifts. Combined the two cantilever sensors, the proposed gas sensor can distinguish H2S from a variety of common gases, and the detection limit to H2S of the sensor is as sensitive as below 1 ppb. 相似文献
65.
Guifang Ju Yihua Hu Li Chen Xiaojuan Wang Lihua Hung 《Applied Physics A: Materials Science & Processing》2014,114(3):867-874
We investigate the persistent luminescence in europium-doped SrMg2(PO4)2 upon codoping with auxiliary terbium. Luminescence properties of the phosphors, including photoluminescence, luminescence decay and thermoluminescence, are systematically studied. SrMg2(PO4)2:Eu2+ shows only a weak persistent luminescence, and codoping with Tb3+ is necessary to obtain considerable persistent luminescence. An energy level scheme is constructed to convey reasonable trapping and detrapping processes in the material. 相似文献
66.
67.
Wei Qinghua Li Zi Yang Xi Chen Jianghui Liu Xiaohua Hu Wenhao Liu Shunying 《Molecular diversity》2019,23(4):997-1010
Molecular Diversity - A Rh(I)/Sc(III) co-catalyzed synthesis of highly valuable functionalized 1,4-diketone derivatives in good yields and with an excellent diastereoselectivity. The established... 相似文献
68.
Jiahao Liu Weikang Li Dr. Yinwu Li Prof. Dr. Yan Liu Prof. Dr. Zhuofeng Ke 《化学:亚洲杂志》2021,16(20):3124-3128
The first implementation of a molybdenum complex with an easily accessible bis-N-heterocyclic carbene ligand to catalyze β-alkylation of secondary alcohols via borrowing-hydrogen (BH) strategy using alcohols as alkylating agents is reported. Remarkably high activity, excellent selectivity, and broad substrate scope compatibility with advantages of catalyst usage low to 0.5 mol%, a catalytic amount of NaOH as the base, and H2O as the by-product are demonstrated in this green and step-economical protocol. Mechanistic studies indicate a plausible outer-sphere mechanism in which the alcohol dehydrogenation is the rate-determining step. 相似文献
69.
Yujie Hua Xican Li Wenhui Zhang Ban Chen Yamei Liu Xiaojun Zhao Hong Xie Dongfeng Chen 《Journal of Saudi Chemical Society》2021,25(7):101272
Folium Hibisci Mutabilis, a new member of Chinese Pharmacopoeia, can treat some diseases induced by reactive oxygen species. The study prepared a lyophilized aqueous extract of Folium Hibisci Mutabilis (LAFHM). LAFHM was found to enrich eight flavonoids (i.e., quercetin, luteolin, hyperoside, isoquercitrin, rutin, kaempferol, tiliroside, and vitexin) by HPLC analysis. These flavonoids were further compared using antioxidant assays, where triliroside and vitexin always exhibited higher IC50 values than the others. In ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis, these flavonoids could basically give two characteristic m/z values (226 and 196) and their corresponding double m/z values (i.e., 602, 570, 926, 926, 570, 1186, and 862), when treated by 1,1-diphenyl-2-picryl-hydrazl radical (DPPH?). Finally, the coupling products of DPPH?-treated triliroside were investigated using computational chemistry. It was found that the –OH in para-coumaroyl moiety to have the lowest bond disassociation energy among all phenolic -OHs in the triliroside. In conclusion, Folium Hibisci Mutabilis contains the above eight antioxidant flavonoids. Despite of the different antioxidant levels, they can generally produce flavonoid-radical coupling product and flavonoid-flavonoid homodimer during antioxidant process. Especially, tiliroside uses para-coumaroyl as linker to construct a tiliroside-radical coupling product at the meta-carbon atom. 相似文献
70.
Bo Wang Dr. Wencheng Du Dr. Yang Yang Dr. Yufei Zhang Dr. Qi Zhang Prof. Xianhong Rui Dr. Hongbo Geng Prof. Cheng Chao Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6554-6560
Lithium ion batteries (LIBs) at present still suffer from low rate capability and poor cycle life during fast ion insertion/extraction processes. Searching for high-capacity and stable anode materials is still an ongoing challenge. Herein, a facile strategy for the synthesis of ultrathin GeS2 nanosheets with the thickness of 1.1 nm is reported. When used as anodes for LIBs, the two-dimensional (2D) structure can effectively increase the electrode/electrolyte interface area, facilitate the ion transport, and buffer the volume expansion. Benefiting from these merits, the as-synthesized GeS2 nanosheets deliver high specific capacity (1335 mAh g−1 at 0.15 A g−1), extraordinary rate performance (337 mAh g−1 at 15 A g−1) and stable cycling performance (974 mAh g−1 after 200 cycles at 0.5 A g−1). Importantly, our fabricated Li-ion full cells manifest an impressive specific capacity of 577 mAh g−1 after 50 cycles at 0.1 A g−1 and a high energy density of 361 Wh kg−1 at a power density of 346 W kg−1. Furthermore, the electrochemical reaction mechanism is investigated by the means of ex-situ high-resolution transmission electron microscopy. These results suggest that GeS2 can use to be an alternative anode material and encourage more efforts to develop other high-performance LIBs anodes. 相似文献