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排序方式: 共有187条查询结果,搜索用时 15 毫秒
171.
Nemat Tahmasbi Somayeh Madmoli Parisa Farahnak Shahram Barzegar Hamze Moayeri 《Russian Journal of Applied Chemistry》2017,90(9):1488-1493
In the paper cesium tungstate nanofibers for the first time have been fabricated successfully by a simple electrospinning technique followed by heat treatment. The cesium tungstate nanofibers have been characterized by XRD, SEM, and FTIR techniques. The results indicated the morphology and quality of the annealed electrospun samples are strongly dependent on the citric acid content within electrospinning solution. It is found with increasing the citric acid content from 7 to 22% the samples morphology changed from a particle structure to a fibrous structure. The average diameter of nanofibers was ~350 nm. XRD analysis reveals that all of the samples have good crystallinity with the same diffraction peaks that can be indexed to the tetragonal phase of Cs2W3O10. Furthermore, the photocatalyst properties of cesium tungstate has not been reported to date. In the work the synthesized Cs2W3O10 nanofibers were found to exhibit photocatalytic performance in the photodegradation of RhB aqueous solution used as a pollutant model. 相似文献
172.
Esmail Vessally Mehdi D. Esrafili Roghaye Nurazar Parisa Nematollahi Ahmadreza Bekhradnia 《Structural chemistry》2017,28(3):735-748
In this work, the interaction of an aspirin (AS) molecule with the external surface of a boron nitride fullerene-like nanocage (B12N12) is studied by means of density functional theory (DFT) calculations. Equilibrium geometry, electronic properties, adsorption energy and thermodynamic stability are identified for all of the adsorbed configurations. Four stable configurations are obtained for the interaction of AS molecule with the B12N12 nanocage, with adsorption energies in the range of ?10.1 to ?37.7 kcal/mol (at the M06-2X/6-31 + G** level). Our results clearly indicate that Al-doping of the B12N12 tends to increase the adsorption energy and thermodynamic stability of AS molecule over this nanocage. We further study the adsorption of AS over the B12N12 and B11N12Al in the presence of a protic (water) or aprotic (benzene) solvent. It is found that the calculated binding distances and adsorption energies by the PCM and CPCM solvent models are very similar, especially for the B12N12 complexes. According to time-dependent DFT calculations, the Al-doping can shift estimated λ max values toward longer wavelengths (redshift). Solvent effects also have an important influence on the calculated electronic absorption spectra of AS-B12N12 complexes. 相似文献
173.
Somayeh Tajik Hadi Beitollahi Zahra Dourandish Peyman Mohammadzadeh Jahani Iran Sheikhshoaie Mohammad Bagher Askari Parisa Salarizadeh Fariba Garkani Nejad Dokyoon Kim Soo Young Kim Rajender S. Varma Mohammadreza Shokouhimehr 《Electroanalysis》2022,34(7):1065-1091
Non-precious transition metal oxide nanomaterials offer numerous opportunities for various cost-effective electrochemical applications. This review article features the design and advancement of such nanomaterials with unique features applied for the fabrication of electrochemical devices. Also, it discusses various new syntheses of transition metal oxide nanoparticles (TMO NPs) via multiple chemicophysical and biological procedures. Further, the novel appliances of the TMO NPs with varying sizes and morphologies are appraised. The advantages and challenges of a number of investigations on the TMO NPs towards electrochemical applications are addressed with their standpoint of cost-effectiveness, applicability, and the efficiency of the introduced nanostructures for the industrial applications. 相似文献
174.
A methodology for controlling aggregation in highly active and isoselective indium catalysts for the ring opening polymerization of racemic lactide is reported. A series of racemic and enantiopure dinuclear indium ethoxide complexes bearing salen ligands [(ONNOR)InOEt]2 (R = Br, Me, admantyl, cumyl, t-Bu) were synthesized and fully characterized. Mononuclear analogues (ONNOR)InOCH2Pyr (R = Br, t-Bu, SiPh3) were synthesized by controlling aggregation with the use of chelating 2-pyridinemethoxide functionality. The nuclearity of metal complexes was confirmed using PGSE NMR spectroscopy. Detailed kinetic studies show a clear initiation period for these dinuclear catalysts, which is lacking in their mononuclear analogues. The polymerization behavior of analogous dinuclear and mononuclear compounds is identical and consistent with a mononuclear propagating species. The isotacticity of the resulting polymers was investigated using direct integration and peak deconvolution methodologies and the two were compared. 相似文献
175.
Prof. Mehdi D. Esrafili Ramin Mohammad‐Valipour Prof. Seyed Morteza Mousavi‐Khoshdel Parisa Nematollahi 《Chemphyschem》2015,16(17):3719-3727
The geometry, electronic structure, and catalytic properties of nitrogen‐ and phosphorus‐doped graphene (N‐/P‐graphene) are investigated by density functional theory calculations. The reaction between adsorbed O2 and CO molecules on N‐ and P‐graphene is comparably studied via Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms. The results indicate that a two‐step process can occur, namely, CO+O2→CO2+Oads and CO+Oads→CO2. The calculated energy barriers of the first step are 15.8 and 12.4 kcal mol?1 for N‐ and P‐graphene, respectively. The second step of the oxidation reaction on N‐graphene proceeds with an energy barrier of about 4 kcal mol?1. It is noteworthy that this reaction step was not observed on P‐graphene because of the strong binding of Oads species on the P atoms. Thus, it can be concluded that low‐cost N‐graphene can be used as a promising green catalyst for low‐temperature CO oxidation. 相似文献
176.
177.
Melodie Christensen Lars P. E. Yunker Parisa Shiri Tara Zepel Paloma L. Prieto Shad Grunert Finn Bork Jason E. Hein 《Chemical science》2021,12(47):15473
Automation has become an increasingly popular tool for synthetic chemists over the past decade. Recent advances in robotics and computer science have led to the emergence of automated systems that execute common laboratory procedures including parallel synthesis, reaction discovery, reaction optimization, time course studies, and crystallization development. While such systems offer many potential benefits, their implementation is rarely automatic due to the highly specialized nature of synthetic procedures. Each reaction category requires careful execution of a particular sequence of steps, the specifics of which change with different conditions and chemical systems. Careful assessment of these critical procedural requirements and identification of the tools suitable for effective experimental execution are key to developing effective automation workflows. Even then, it is often difficult to get all the components of an automated system integrated and operational. Data flows and specialized equipment present yet another level of challenge. Unfortunately, the pain points and process of implementing automated systems are often not shared or remain buried deep in the SI. This perspective provides an overview of the current state of automation of synthetic chemistry at the benchtop scale with a particular emphasis on core considerations and the ensuing challenges of deploying a system. Importantly, we aim to reframe automation as decidedly not automatic but rather an iterative process that involves a series of careful decisions (both human and computational) and constant adjustment.The process of automating chemistry involves a wide variety of considerations that are often overlooked. 相似文献
178.
We report the alternating copolymerization of caprolactone and epoxide through the in situ formation of pre-sequenced spiroorthoester monomer. The reaction is catalyzed by the temperature triggered, bifunctional cationic indium complex (±)-[(NNiOtBu)In(CH2SiMe3)][B(C6F5)4] (1). 1 can catalyze the coupling of epoxide and lactone to form spiroorthoester at 60 °C and its double ring-opening polymerization at 110 °C to form poly(ether-alt-ester). The post-polymerization modification and degradation of the poly(ether-alt-ester) are further investigated.We report the alternating copolymerization of caprolactone and epoxide through the in situ formation of pre-sequenced spiroorthoester monomer. 相似文献
179.
Hamid Entezar Mehdi Parisa Esmaili Mehdi Nasiri Sarvi Somayeh Asgary 《Optical and Quantum Electronics》2018,50(9):344
Silver oxide nano layers were prepared by RF magnetron sputtering on amorphous SiO2 substrates. O2 pressure in chamber was varied from 1 to 4 and 7 mTorr during growth process. The effects of different O2 pressure on structural, morphological and optical properties of the films were investigated by means of X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV–Vis spectroscopy analyses. Optical reflectance measured in the wavelength of 350–950 nm by spectroscopy. Other optical properties and optical band gaps were calculated using Kramers–Kronig relations. The X-ray diffraction measurements showed change in crystalline structure with increasing O2 pressure. Preferred orientation has been changed to another growth orientation at 4 mTorr O2 pressure. The Atomic force microscope images showed increasing in roughness consistently by increasing oxygen pressure. The thickness of the thin films decreases (from 217 to 180 nm) with increasing O2 pressure. Optical results revealed that the highest optical band gap of 3.1 eV and the highest transmittance of?~?80% were achieved at lower O2 pressure (1 mTorr). 相似文献
180.
Since its innovation in 2006, the dispersive liquid-liquid microextraction (DLLME) method has attracted the attention of analytical chemists in the field of sample preparation. This method has been successfully applied to determine trace amounts of pollutants in various matrices, but the restriction in the choice of suitable disperser and extraction solvents, and high disperser solvent consumption leading to decreased partition coefficients of the analytes between aqueous phase and extractant are its problems. To solve these drawbacks and develop environmentally friendly techniques, various alternatives for the conventional DLLME have been presented. The current review will begin with an introduction to the sample preparation, implementation of DLLME, and its advantages. Then, we focus on its drawbacks, which result mainly from the use of disperser solvent. Afterward, some of the most interesting approaches that have been employed and published until now are reviewed. Finally, an outlook on the future of these techniques will be given. 相似文献