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911.
《印度化学会志》2022,99(11):100753
Density Functional Theory (DFT) computations were performed to investigate the optical properties of dihydropyrimidine (DHP) and metal clusters of copper (Cu), gold (Au), and silver (Ag). The charge transfers from the metal cluster to DHP through the NH group are revealed by molecular electrostatic potential (MEP) surface and Mulliken charge analysis. Bonding and antibonding orbitals of the DHP-adsorbed metal clusters are responsible for the surface resonance peak in the UV–Vis spectra of DHP adsorbed metal clusters. The polarizability values of DHP-adsorbed on metal clusters are very high in comparison with that of pristine DHP, which suggests an increase in the Non-linear optical (NLO) effect. Our study explores that the DHP adsorbed metal clusters could be used for the NLO materials. The vibrational modes of DHP are enhanced in the DHP adsorbed metal clusters due to surface-enhanced Raman scattering (SERS). Solvation energy is found to be ?21.01, ?29.37, and ?27.82 kcal/mol for DHP-Ag3/Au3/Cu3 which means the DHP-adsorbed metal clusters are stable in thr aqueous medium. The atom in molecule-reduced density gradient (AIM-RDG) isosurface shows weak non-covalent interactions in each DHP adsorbed metal clusters. 相似文献
912.
以液体端羧基氟橡胶(LTCFs)为原料, 硼氢化钠与金属氯化物(NaBH4/MCl x )为还原体系, 采用一锅法成功将LTCFs还原为液体端羟基氟橡胶(LTHFs). 研究了多种稀土金属氯化物(LaCl3, CeCl3, NdCl3和SmCl3)和过渡金属氯化物(MnCl2, NiCl2, CoCl2和CuCl2)对LTCFs还原效果的影响及变化规律. 采用傅里叶变换红外光谱(FTIR)、 核磁共振氢谱(1H NMR)、 核磁共振氟谱(19F NMR)和化学滴定法对原料和产物的分子链结构和官能团含量进行了表征. 结果表明, 稀土金属MCl x 还原体系对LTCFs的还原效果均高于过渡金属MCl x 还原体系, LTCFs中的—C=C—和—COOH均可以被还原为—C—C—和—OH, 其中NaBH4/SmCl3还原体系还原效率最高, 达到92%. 机理研究表明, NaBH4/MCl x 对—COOH的还原性能与MCl x 中金属阳离子和羰基氧间的结合力有关, 结合力越大越有利于—COOH的还原. 相似文献
913.
CuCo-MOF nanofibers are synthesized by one-step solvent blending process at room temperature. Then CuCo-MOF nanofibers are used as the precursors,carbon nanosheets(Cu(Ⅱ)Co(Ⅱ)@C)uniformly loaded with nano-sized copper oxide and cobalt oxide are obtained by calcination at high temperature in air. Cu(Ⅱ)Co(Ⅱ)@C is modified on the glassy carbon electrode to directly catalyze glucose in alkaline solution. Because CuO and CoO are uniformly and firmly embedded on the carbon nanosheets,the agglomeration of catalyst is prevented,which greatly improves the specific surface area,and increases the catalytic active site. Meanwhile,due to the synergistic effect of copper and cobalt bimetals in the carbon nanosheet material,the enzyme free glucose sensor has excellent electrical conductivity and excellent catalytic performance. The detection range of the non-enzymatic electrochemical glucose sensors for glucose is 0. 03 µμmol/L~13. 6 mmol/L, the detection limit is 0. 01 µμmol/L(S/N=3),and the sensitivity is 10. 56 mA·L/(cm2·mmol). In addition, the non-enzyme sensor also has good anti-interference and high stability. © 2022, Science Press (China). All rights reserved. 相似文献
914.
Metal nanoparticles in porous supports are of great importance for catalysis, separation and sensing, but their controllable preparation is still largely unmet. Herein, we describe a simple laser-induced synthesis of ultrafine gold nanoparticles in the covalent organic framework. Gold nanoparticles are well embedded, and they are about (1±0.1) nm in size. This work is universal for the preparation of well-dispersed and ultrafine metal nanoparticles in porous supports. 相似文献
915.
Energy production and environmental pollution are the two major problems the world is facing today. The depletion of fossil fuels and the emission of harmful gases into the atmosphere leads to the research on clean and renewable energy sources. In this context, hydrogen is considered an ideal fuel to meet global energy needs. Presently, hydrogen is produced from fossil fuels. However, the most desirable way is from clean and renewable energy sources, like water and sunlight. Sunlight is an abundant energy source for energy harvesting and utilization. Recent studies reveal that photoelectrochemical (PEC) water splitting has promise for solar to hydrogen (STH) conversion over the widely tested photocatalytic approach since hydrogen and oxygen gases can be quantified easily in PEC. For designing light-absorbing materials, semiconductors are the primary choice that undergoes excitation upon solar light irradiation to produce excitons (electron-hole pairs) to drive the electrolysis. Visible light active semiconductors are attractive to achieve high solar to chemical fuel conversion. However, pure semiconductor materials are far from practical applications because of charge carrier recombination, poor light-harvesting, and electrode degradation. Various heteronanostructures by the integration of metal plasmons overcome these issues. The incorporation of metal plasmons gained significance for improving the PEC water splitting performance. This review summarizes the possible main mechanisms such as plasmon-induced resonance energy transfer (PIRET), hot electron injection (HEI), and light scatting/trapping. It also deliberates the rational design of plasmonic structures for PEC water splitting. Furthermore, this review highlights the advantages of plasmonic metal-supported photoelectrodes for PEC water splitting. 相似文献
916.
Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in a wide variety of fields. The knowledge about the detailed interactions between MOFs and guest molecules is critical for the understanding of their structure-property relationships at working conditions. In this review, recent advances for solid-state NMR studies of host–guest chemistry of MOFs in the application fields of gaseous adsorption, chemical separation, drug delivery, chemical sensor, and heterogeneous catalysis were briefly introduced. The adsorption property and dynamic behavior of adsorbed gases confined inside the MOFs channels were elucidated from variable-temperature (VT) solid-state NMR. Moreover, the detailed mechanism of gas-phase and liquid-phase adsorptive separations on MOFs adsorbents was uncovered on the basis of solid-state NMR measurements. Multi-nuclear 1H, 13C, 15N, and 31P MAS NMR was utilized to explore the interactions between drug molecules and MOFs at the atomic scale to monitor the controlled release process of drugs. Furthermore, the investigation of the interactions between guest molecules and MOFs in the application areas of chemical sensor, toxic chemicals removal, and catalysis using solid-state NMR was briefly discussed as well. 相似文献
917.
《Arabian Journal of Chemistry》2022,15(7):103906
Environmental pollution and energy shortage are substantial fears to the modern world's long-term sustainability. Water splitting is an essential technique for eco - friendly and sustainable energy storage, as well as a pollution-free method to produce hydrogen. In this regards Metal–organic frameworks have emerged as the most competent multifunctional materials in recent times, due to its large surface areas, adjustable permeability, easy compositional alteration, and capability for usage as precursors with a wide range of morphological forms. Further, MOF-derived carbon-based nanomaterials also offer significant benefits in terms of tunable morphological features and hierarchical permeability, as well as ease of functionalization, making them extremely effective as catalysts or catalysts supports for a wide variety of important reactions. Recent developments in carbon-based MOFs as catalysts for overall water splitting are discussed in this review. We explore how MOFs and carbon-based MOFs might well be beneficial, as well as which methods should be explored for future development. We divided our review into two sections: photocatalytic and electrocatalytic water splitting, and we gathered published literature on carbon-based MOFs materials for their outstanding activity, offers helpful methods for catalysts design and analysis, as well as difficulties This study highlights the developments in MOF derived materials as photo and electro catalysts by explaining respective approaches for their use in overall water splitting. 相似文献
918.
《Comptes Rendus Physique》2015,16(8):731-738
After more than a decade of intensive research in the field of diluted magnetic semiconductors (DMS), the nature and origin of ferromagnetism, especially in III–V compounds, is still controversial. Many questions and open issues are under intensive debates. Why after so many years of investigations, Mn-doped GaAs remains the candidate with the highest Curie temperature among the broad family of III–V materials doped with transition metal (TM) impurities? How can one understand that these temperatures are almost two orders of magnitude larger than that of hole-doped (Zn,Mn)Te or (Cd,Mn)Se? Is there any intrinsic limitation or is there any hope to reach room-temperature ferromagnetism in the dilute regime? How can one explain the proximity of (Ga,Mn)As to the metal–insulator transition and the change from Ruderman–Kittel–Kasuya–Yosida (RKKY) couplings in II–VI compounds to double-exchange type in (Ga,Mn)N? In spite of the great success of density functional theory-based studies to provide accurately the critical temperatures in various compounds, till very lately a theory that provides a coherent picture and understanding of the underlying physics was still missing. Recently, within a minimal model, it has been possible to show that among the physical parameters, the key one is the position of the TM acceptor level. By tuning the value of that parameter, one is able to explain quantitatively both magnetic and transport properties in a broad family of DMS. We will see that this minimal model explains in particular the RKKY nature of the exchange in (Zn,Mn)Te/(Cd,Mn)Te and the double exchange type in (Ga,Mn)N and simultaneously the reason why (Ga,Mn)As exhibits the highest critical temperature among both II–VI and III–V DMS's. 相似文献
919.
《Comptes Rendus Chimie》2015,18(7):713-741
The purpose of this review is to analyze the different reaction mechanisms of the H/D exchange on organic substrates catalyzed by transition metal complexes in homogeneous phase. The metal-catalyzed H/D exchange is a multifaceted reaction whose mechanism depends strongly on the reaction conditions and on the metal complex used as a catalyst. It is possible to group the different mechanisms into three main families depending on the “role” and behavior of the catalyst: (i) Lewis acid–base catalysis; (ii) CH activation (iii) insertion/β-elimination. For each macro-group, several representative examples are discussed and critically evaluated in order to provide the reader with keys to the understanding of how the different catalytic systems act and how their modification may affect their performance in terms of activity and selectivity. This knowledge is fundamental for designing improved organometallic H/D catalysts for labeling organic products in greener conditions with more cost-effective processes. 相似文献
920.
Satoru Utsugi Yoshitaka Ehara Hidenori Tanaka Tomoaki Yamada Hiroshi Funakubo Hiroshi Uchida 《Journal of Crystal Growth》2010,312(21):3127-3130
Epitaxial (La0.07Sr0.93)SnO3 [LSSO] films were deposited on CaF2 substrates by pulse laser deposition. The (1 0 0)c orientation of LSSO films was observed only on (1 1 0)CaF2, whereas (1 1 0)c orientation was found on (1 1 1)CaF2 and (1 0 0)CaF2. (0 0 1) polar axis oriented tetragonal Pb(Zr0.35Ti0.65)O3 films were grown on the fabricated (1 0 0)cLSSO∥(1 1 0)CaF2 by pulsed metal organic chemical vapor deposition. The (0 0 1)Pb(Zr0.35Ti0.65)O3∥(1 0 0)cLSSO∥(1 1 0)CaF2 stack structure exhibited about 70% transparency with an adsorption edge of approximately 330 nm. 相似文献