In recent years, heteroatom-incorporated specially structured metal-free carbon nanomaterials have drawn huge attention among researchers. In comparison to the undoped carbon nanomaterials, heteroatoms such as nitrogen-, sulphur-, boron-, phosphorous-, etc., incorporated nanomaterials have become well-accepted as potential electrocatalysts in water splitting, supercapacitors and dye-sensitized solar cells. This review puts special emphasis on the most popular synthetic strategies of heteroatom-doped and co-doped metal-free carbon nanomaterials, viz., chemical vapor deposition, pyrolysis, solvothermal process, etc., utilized in last two decades. These specially structured nanomaterials’ extensive applications as potential electrocatalysts are taken into consideration in this article. Their comparative enhancement of electrocatalytic performance with incorporation of heteroatoms has also been discussed. 相似文献
Room‐temperature nanosecond/microsecond laser‐flash photolysis and low‐temperature phosphorescence studies reveal that two different triplets coexist during the twisted intramolecular charge transfer (TICT) of 4‐(dimethylamino)benzonitrile in polar solvents. 相似文献
Structural transition can be induced in charged micelles by increasing the ionic strength of the medium. Thus, spherical micelles of sodium dodecyl sulfate (SDS) that exist in water at concentrations higher than the critical micelle concentration assume an elongated rod-like structure in the presence of an increased electrolyte concentration. This is known as sphere-to-rod transition. In this paper, we characterize the change in organization and dynamics that is accompanied by the salt-induced sphere-to-rod transition in SDS micelles using wavelength-selective fluorescence and other steady-state and time-resolved fluorescence parameters. Since the change in micelle organization during such structural transition may not be limited to one region of the micelle, we have selectively introduced fluorophores in two distinct regions of the micelle. We used two probes, N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (NBD-PE) and 25-[N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-methyl]amino]-27-norcholesterol (NBD-cholesterol), for monitoring the two regions of the micelle. NBD-PE monitors the interfacial region of the micellar assembly, while NBD-cholesterol acts as a reporter for the deeper regions of the micellar interior. Our results show that wavelength-selective fluorescence, in combination with other fluorescence parameters, offers a powerful way to monitor structural transitions induced in charged micelles. These results could be significant to changes in membrane morphology observed under certain physiological conditions. 相似文献
Summary: We consider the shape of strongly adsorbed polymer chains in poor solvents. Using both SCF theory and Monte Carlo simulations, we find these chains undergo an instability which is driven, surprisingly, by polymer entropy. This instability occurs above some critical grafting separation and the intermediate segregation regime. An analytical calculation also suggests that this instability occurs for strongly adsorbed polymer chains. We proceed to study multi‐chain systems and observe a number of novel morphological structures including circular polymer droplets, lamellae and a polymer layer with a solvent‐filled hole.
Shape of strongly adsorbed multi‐chain polymer globules. 相似文献
Reaction of Ru(PPh3)2Br2 with the NNS chelating tridentate ligand 2-pyridyl-N-(2′-methylthiophenyl)methyleneimine (L) led to the isolation of the ruthenium(II) complex [Ru(L)(PPh3)Br2]. Reactivity of this complex with different bidentate chelating ligands revealed that the products are quite different from those obtained by reacting Ru(L)(PPh3)Cl2 (the corresponding cis dichloro complex) with the same ligands under comparable conditions. The mixed chelates were isolated and characterised by elemental analysis, magnetic moment measurement and by different spectroscopic methods along with their precursor. Electrochemistry of the complexes was examined by cyclic voltammetry using a platinum working electrode and a Ag/AgCl electrode as reference. The crystal structure of [Ru(L)(PPh3)Br2] disclosed that, unlike Ru(L)(PPh3)Cl2, the two bromo ligands are in trans position and this explained the difference in its reactivity pattern from the corresponding chloro complex. 相似文献
The present paper deals with the problem of nonselective harvesting in a partly infected prey and predator system in which both the susceptible prey and the predator follow the law of logistic growth and some preys avoid predation by hiding. The dynamical behaviour of the system has been studied in both the local and global sense. The optimal policy of exploitation has been derived by using Pontraygin’s maximal principle. Numerical analysis and computer simulation of the results have been performed to investigate the global properties of the system. 相似文献
Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [CuII(L1)Cl]ClO4 (1), [CuII(L2)Cl]ClO4 (2) and [CuII2(L3)2Cl2](ClO4)2 (3) were synthesized and isolated in pure form [where L1 = 1,2-bis(2-pyridylmethylthio)ethane, L2 = 1,3-bis(2-pyridylmethylthio)propane and L3 = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [CuI2(L3)2](ClO4)2,0.5H2O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes 1 and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral. 相似文献
The magnetic structure of one of the two ordered phases has been determined at 5 K. The magnetic structure is found to be antiferromagnetic with a cell doubling in the c direction of the monoclinic nuclear cell. The centering in the nuclear cell is replaced by anticentering. The collinear magnetic moments are parallel to the b axis. The magnetic moment per Eu atom has been found to be 5.74(6)μB which leads to the saturation magnetic moment of 6.5μB. 相似文献
A review on the studies of chemical consequences of recoil sulfur,3 5S, produced by the nuclear reaction3 5Cl(n, p)3 5 S in alkali chloride matrices is presented. 相似文献