The interaction of calixarenes and amines in CH3CN solution is postulated to involve a two-step process, viz., proton transfer from the calixarene to the amine to form the amine cation and the calixarene anion followed by association of the ions to form a complex. The overall association complex for p-allylcalix[4]arene and ZerZ-butylamine, as a typical example, is about 106, the larger part of this arising from the proton transfer, as measured from UV spectral observations, and the smaller part arising from the association of the ions, as measured from *H NMR observations. A 2D NOE spectrum of this complex indicates that the methyl groups of the amine and the allyl groups of the calixarene are proximate, in agreement with an emfo-calix structure for the complex.
Electrochemical CO 2 reduction on Cu electrode has attracted the attention of many researchers in the last decades, because of its potential to generate significant amounts of hydrocarbons at high reaction rates over sustained periods of time. As a result, substantial effort has been devoted to determining the unique catalytic performance of Cu and to elucidate the mechanism through which hydrocarbons are formed. Here we report new insights into CO 2 reduction on Cu by electrochemical impedance spectroscopy (EIS) in terms of adsorption/desorption of the reduction intermediates. The potential dependence of charge transfer kinetics is discussed on the basis of EIS results. We revisit the mechanism of the formation of hydrocarbons, taking into account the pH adjacent to the electrode surface, adsorption of HCO 3 − and CO 3 2− , and the role of active hydrogen. In addition to the enol-like intermediate, proposed previously, we proposed that *COOH • radicals, originating from the active involvement of HCO 3 − and/or CO 3 2− upon reduction are key intermediates for the formation of a variety of C2 and C3 products. Thus, our results provide an additional crucial guideline for the design of future catalysts that can efficiently and selectively reduce CO 2 into value-added chemicals.
The coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is considered as serious global threat of this time and greatest challenge for recent days. Several approaches have been carried out in this direction to fight against COVID‐19. Among these, nanotechnology is one of the promising approach to face these challenges in the current situation. Recently, graphene‐based nanomaterials have been explored for COVID‐19 due to its unique physicochemical properties. This mini review provides a recent progress in graphene‐based nanomaterials and its applications for diagnosis, detection, decontamination, and protection against COVID‐19. Further, main challenges and perspective for fundamental design and development of technologies based on graphene‐based materials are discussed and suitable directions to improve these technologies are suggested. This article will provide timely knowledge and future direction about this wonder materials in various biological applications.
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