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排序方式: 共有3182条查询结果,搜索用时 15 毫秒
1.
Yaoli Wang Yan Liang Huixiang Sheng Jin Wang Junjie Wang Shunhao He Mengdan Guan Yaqi Chen Prof. Gang Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202103709
Surface plasmon can trigger or accelerate many photochemical reactions, especially useful in energy and environmental industries. Recently, molecular adsorption has proven effective in modulating plasmon-mediated photochemistry, however the realized chemical reactions are limited and the underlying mechanism is still unclear. Herein, by using in situ dark-field optical microscopy, the plasmon-mediated oxidative etching of silver nanoparticles (Ag NPs), a typical hot-hole-driven reaction, is monitored continuously and quantitatively. The presence of thiol or thiophenol molecules is found essential in the silver oxidation. In addition, the rate of silver oxidation is modulated by the choice of different thiol or thiophenol molecules. Compared with the molecules having electron donating groups, the ones having electron accepting groups accelerate the silver oxidation dramatically. The thiol/thiophenol modulation is attributed to the modulation of the charge separation between the Ag NPs and the adsorbed thiol or thiophenol molecules. This work demonstrates the great potential of molecular adsorption in modulating the plasmon-mediated photochemistry, which will pave a new way for developing highly efficient plasmonic photocatalysts. 相似文献
2.
Xinyu Zhang Linxuan Li Prof. Giuseppe Zanoni Xinyue Han Prof. Xihe Bi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(22):e202200280
The direct gem-difluoroalkenylation of X−H bonds represents the most straightforward approach to access heteroatomic gem-difluoroalkenes that, as the isostere of the carbonyl group, have great potency in drug discovery. However, the construction of tetrasubstituted heteroatomic gem-difluoroalkenes by this strategy is still an unsolved problem. Here, we report the first direct X−H bond gem-difluoroalkenylation of amines and alcohols with trifluoromethyl ketone N-triftosylhydrazones under silver (for (hetero)aryl hydrazones) or rhodium (for alkyl hydrazones), thereby providing a most powerful method for the synthesis of tetrasubstituted heteroatomic gem-difluoroalkenes. This method features a broad substrate scope, high product yield, excellent functional group tolerance, and operational simplicity (open air conditions). Moreover, the site-specific replacement of the carbonyl group with a gem-difluorovinyl ether bioisostere in drug Trimebutine and the post-modification of bioactive molecules demonstrates potential use in medicinal research. Finally, the reaction mechanism was investigated by combining experiments and DFT calculations, and disclosed that the key step of HF elimination occurred via five-membered ring transition state, and the difference in the electrophilicity of Ag- and Rh-carbenes as well as the multiple intermolecular interactions rendered the effectiveness of Rh catalyst selectively for alkyl hydrazones. 相似文献
3.
以青霉胺(DPA)为还原剂和稳定剂,通过一锅法一步制备了青霉胺稳定的铜/银双金属纳米簇(DPA-Cu/Ag NCs),并将其作为一种传感器用于检测水样中的银离子。该银离子传感器具有价格低廉、分析速度快速、选择性高等特点。采用透射电子显微镜(TEM)等方法表征了DPA-Cu/Ag NCs的结构及其化学组成,并通过荧光光谱和紫外-可见光谱法研究了DPA-Cu/Ag NCs的光学性质。结果表明,该DPA-Cu/Ag NCs在激发波长为300 nm时的最大发射波长为555 nm,其溶液在可见光照射下呈现乳白色,在紫外灯照射下则呈现出明亮的黄色荧光。在DPA-Cu/Ag NCs的制备条件达到最优化的情况下,可以将其作为探针,用来高选择性、高灵敏性地检测银离子。该探针检测银离子的检测限为0.3μmol/L,线性范围为0~500μmol/L。该DPA-Cu/Ag NCs探针还可应用于自然环境水样(湖水、瓶装矿泉水和实验室自来水)中银离子浓度的检测,其检测性能十分优异且具有良好的准确度和重现性,表明DPA-Cu/Ag NCs探针在环境检测方面有非常高的应用价值。 相似文献
4.
采用时域有限差分方法(FDTD)研究金、银纳米结构的非局域吸收。对金属材料的Drude-Lorentz模型进行离散差分,详细推导各项迭代系数。研究一维、二维、三维金、银纳米结构的吸收特性。讨论一维分层纳米薄膜吸收率与材料的关系。结果表明:非局域分层介质板仍然符合等效介质理论。在一维、二维情况下,金、银纳米结构的非局域吸收峰只与纳米尺度相关而与材料无关。三维纳米结构的非局域吸收特性不仅与纳米尺度相关还与材料特性相关。三维纳米结构尺度更小,非局域效应表现也更为明显,吸收峰的蓝移也更大。因此,三维纳米颗粒有望在纳米材料以及纳米器件的研究中发挥更大的作用。 相似文献
5.
Ana Elisa Ferreira Oliveira Arnaldo César Pereira Mayra Asevedo Campos de Resende Lucas Franco Ferreira 《Electroanalysis》2022,34(5):809-819
In this work, a silver/silver chloride ink is fabricated using two steps. First the silver ink is prepare using silver, nail polish and acetone. Then the silver ink is painted in a paper substrate and a silver chloride layer is deposited using a bleach solution. The result is the silver/silver chloride conductive ink. The silver ink is cheap ($2.49/g), well-dispersive and very easy to fabricate. The materials were characterized by SEM and XRD. The Ag ink showed the formation of a continuous network throughout the silver ink film with fewer agglomeration. The effective chlorination process was also observed in the Ag/AgCl characterization. Since the Ag/AgCl substrate will be used as a quasi-reference electrode, it is important to investigate the electrical properties. The Ag ink showed an average ohmic resistance of 2.27 Ω. The addition of the AgCl layer decreases the conductivity, as expected. In summary, the Ag/Ag/Cl ink developed is simple, well-dispersed, cheap and with good conductivity. Therefore, it can be used as a conductive ink in the fabrication of quasi-reference electrodes. 相似文献
6.
以双(2?氯乙基)氨基甲酸叔丁酯、2,2?(乙烷?1,2?二丁基(氧基))二乙硫醇和N?乙基咔唑为起始原料,设计、合成了一种含有杂冠醚基团的新型荧光探针分子L,其结构经1H NMR、13C NMR及高分辨质谱进行了表征。随后利用荧光光谱在水/乙醇溶剂(4∶1,V/V)中研究了探针L对Ag+的选择性识别。研究结果表明,探针L与Ag+以1∶1的比例配位。通过计算得到配位常数Ka为2.01×105 L·mol-1,检测限为4.13μmol·L-1。通过实验证明,该探针分子可应用于河流等环境水样中Ag+的检测。 相似文献
7.
Photoelectrochemical activity of ZnO:Ag/rGO photo-anodes synthesized by two-steps sol-gel method 下载免费PDF全文
D Ben Jemia M Karyaoui M A Wederni A Bardaoui M V Martinez-Huerta M Amlouk and R Chtourou 《中国物理 B》2022,31(5):58201-058201
This work investigated the influence of silver plasmon and reduced graphene oxide (rGO) on the photoelectrochemical performance (PEC) of ZnO thin films synthesized by the sol-gel method. The physicochemical properties of the obtained photo-anodes were systematically studied by using several characterization techniques. The x-ray diffraction analysis showed that all samples presented hexagonal wurtzite structure with a polycrystalline nature. Raman and energy dispersive x-ray (EDX) studies confirmed the existence of both Ag and rGO in ZnO:Ag/rGO thin films. The estimated grain size obtained from scanning electron microscopy (SEM) analysis decreased with Ag doping, then increased to a maximum value after rGO addition. The UV-vis transmission spectra of the as-prepared ZnO:Ag and ZnO:Ag/rGO thin films have shown a reduction in the visible range with a redshift at the absorption edges. The bandgaps were estimated to be around 3.17 eV, 2.7 eV, and 2.52 eV for ZnO, ZnO:Ag, and ZnO:Ag/rGO, respectively. Moreover, the electrical measurements revealed that the charge exchange processes were enhanced at the ZnO:Ag/rGO/electrolyte interface, accompanied by an increase in the (PEC) performance compared to ZnO and ZnO:Ag photo-anodes. Consequently, the photocurrent density of ZnO:Ag/rGO (0.2 mA·cm-2) was around 4 and 2.22 times higher than photo-anodes based on undoped ZnO (0.05 mA·cm-2) and ZnO:Ag (0.09 mA·cm-2), respectively. Finally, from the flat band potential and donor density, deduced from the Mott-Schottky, it was clear that all the samples were n-type semiconductors with the highest carrier density for the ZnO:Ag/rGO photo-anode. 相似文献
8.
Mohammad Reza Kashefi Alasl Mahmoud Reza Sohrabi Mehran Davallo 《Journal of separation science》2019,42(9):1777-1785
In this work, a fast and simple magnetic dispersive solid phase extraction methodology was developed utilizing Ag@magnetite nanoparticles@graphene nanocomposite as an efficient magnetic nanosorbent for preconcentration and determine of five aromatic amines in water samples. The sorbent was characterized by diverse characterization techniques. After the extraction, high‐performance liquid chromatography with UV detection was utilized to analysis the aromatic amines. The effects of different factors on the extraction process were studied thoroughly via design of experiment and desirability function. Detection limits and linear dynamic ranges were obtained in the range of 0.10–0.20 and 0.3–300 μg/L, respectively. The relative standard deviations (n = 5) were in the range of 4.3–6.5%. Eventually, the method was employed for determination of target aromatic amines in various water samples. 相似文献
9.
Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted. 相似文献
10.