Review of the synthesis and properties of colloidal quantum dots: the evolving role of coordinating surface ligands

This review highlights the developments in synthetic methods for colloidal quantum dots that have expanded the range of achievable sizes, shapes, materials, and surface chemistries over the past 30 years, and how these methods have enabled optimization of properties like photoluminescence quantum yield, monodisperse size distributions, and conductivity in the solid state.     

Synthesis of Heterocyclic Compounds Catalyzed by Metal/Metal Oxide‐Multiwall Carbon Nanotube Nanocomposites

Metal/metal oxide‐decorated multiwalled carbon nanotubes (MWCNTs ) have been found to be effective over various catalysts because of the synergistic, hybrid, physical, and chemical properties of such nanotubes. These properties make them highly active catalytic tools with excellent chemoselectivity, low catalyst loading, and high recyclability of the catalyst. Here, we discuss some recent findings related to the following topics: (1) synthesis of metal/metal oxide‐decorated MWCNTs , (2) characterization techniques of heterogeneous nanocomposites, and (3) application of these metal/metal oxide nanocomposites for the synthesis of heterocyclic compounds. This review emphasizes the main requirements for developing new nanocomposites for the synthesis of pharmaceutically important heterocycles.     

Atmospheric pressure chemical vapour deposition of NbSe2-TiSe2 composite thin films

Atmospheric pressure chemical vapour deposition of titanium tetrachloride and niobium pentachloride with di-tert-butyl selenide at 550 °C was investigated for different precursors’ flow rates. Scanning electron microscopy of the films showed that they were composed of two different kinds of plate-like crystallites. Point wavelength dispersive X-ray (WDX) analyses of the crystallites revealed that they either had the NbSe₂ or the TiSe₂ composition. The presence of the two phases was confirmed by X-ray diffraction (XRD) and the calculated cell parameters indicate that niobium or titanium was not incorporated into each others’ lattice. WDX and XRD analyses highlighted how the NbSe₂:TiSe₂ ratio in the composite films could be controlled by precursor flow rate.     

Liquid injection field desorption/ionization of transition metal fluoride complexes

Metal fluoride complexes that are extremely sensitive to air and water have been characterized by liquid injection field desorption/ionization (LIFDI) mass spectrometry. Dilute solutions of fluoride complexes of nickel, rhodium, titanium, zirconium and ruthenium in toluene and tetrahydrofuran were examined by LIFDI methods on a time-of-flight mass spectrometer. All the spectra of nickel, titanium and zirconium complexes exhibited the molecular ion as base peak. The ruthenium and rhodium complexes showed [M−HF]⁺ as base peaks but the molecular ions were easily detected. The nickel complexes do not provide useful mass spectra by EI or ESI methods. Only the titanium and zirconium species showed evidence of the fluoride ligands in the ESI spectra. Two new nickel fluoride complexes are formed by C-F activation reactions with 2,3,5,6-tetrafluoro-4-dimethylaminopyridine and 2,3,5,6-tetrafluoro-4-methoxypyridine yielding trans-NiF{2-C₅NF₃(4-NMe₂)}(PEt₃)₂ and trans-NiF{2-C₅NF₃(4-OMe)}(PEt₃)₂, respectively. The crystal structure of trans-NiF{2-C₅NF₃(4-NMe₂)}(PEt₃)₂ shows typical square planar coordination at nickel with an Ni-F distance of 1.8521(9) Å.     

Synthesis,structure, spectral and coordination properties of a crown ether derivative of 1,3-indandione. A new structural evidence for the versatile reactivity of 2-acetyl-1,3-indandione

The current study describes the synthesis of a new 1,3-indandione derivative with conjugated N-phenylaza-15-crown-5 moiety (4). The crystal structure of compound 4 was solved and its optical properties were studied in various solvents and in presence of alkaline and alkaline-earth metal ions. Quantum chemical (DFT) methods were employed to describe the structure and the optical properties of the studied compound and its complexes. The obtained results indicated that the synthesis of compound 4 using acid-catalyzed aldol reaction between 2-acetyl-1,3-indandione and the corresponding aldehyde is accompanied with an unexpected deacetylation step. In this way, the N-phenylaza-15-crown-5 moiety is directly conjugated with the 1,3-indandione fragment, known as a very strong electron acceptor. Therefore, the absorption spectra of 4 are only slightly influenced by complexation with Ba²⁺ and Sr²⁺ ions.     

Characterization of Fluorescence Induced by Side Illumination of Rhodamine B Doped Plastic Optical Fibers

The impact of a post-OTDM-demultiplexing optical filter on the performance of dense on-off keying (OOK) optical time division multiplexing (OTDM)—wavelength division multiplexing (WDM) systems was studied. For return-to-zero (RZ) modulation, it was found that the additional filter working in a double-tier filter configuration did not offer any significant improvements to performance when the signal pulse width is optimized. Improvements generally increase only when the signal pulse width deviates from its optimal value and only for low spectral densities. For ideal non-return-to-zero (NRZ) modulation, however, significant improvements of around 1 dB are obtained using the double-tier configuration over a large range of spectral densities.     

Lubrication studies of aqueous mixtures of inversely soluble components

Phase and aggregational behavior of model metal working formulations of the inversely soluble type was studied with the aid of a new analytical tool. Correlations between these data and measured anti-wear performance data are discussed. The aim was to gain some insight into the mode of variation of the anti-wear effect with temperature and concentration depending on composition of inversely soluble formulations, despite the complexity of the systems. A comparison with a conventional synthetic metal working fluid indicated inherent advantages of inversely soluble concepts at elevated temperatures. Thus, as temperature is increased, as occurs in a friction contact, wear is more effectively mitigated with a suitable formulated inversely soluble system. Typically, as shown experimentally in this paper, the behavior is different from data observed with a conventional metal working fluid formulation. A substantial dependence of the anti-wear effect on the adsorption of boundary lubricating components is inferred from a study of correlation between monomer concentration and extent of wear. These experiments were conducted on surfactant concentrations exceeding critical micelle concentration (CMC) to various degrees. Findings also indicate a particular potential to optimize lubrication performance by exploiting synergetic effects observed in a combination of two different types of alkoxylated compounds. The investigated types of formulations offer particularly good prospects for effective contaminant removal without loss of active matter. This is favorable from an occupational health and environmental standpoint, due to the possibility to exchange biocides with mechanical means of microbial control and an improved potential for a long service life.     

DFT,solvation effects,reactivity and SERS analysis on structural,optical, and vibrational properties of a biomolecule of pyrimidine derivative adsorbed on metal clusters of Ag/Au/Cu

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.     

NaBH4/MCl x 体系对液体端羧基氟橡胶的还原及还原机理

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.     

Study of Electrochemical Non-enzyme Glucose Sensor Based on Cu(Ⅱ)Co(Ⅱ) Bimetallic Carbon Nanosheets北大核心CSCD

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.