Shape memory polymers (SMPs) are a class of smart materials that respond dynamically to external stimuli like heat, 1À11 electric field, 12À14 magnetic field, 15 infrared radiation, 16À18 and UV radiation. 19,20 Because SMPs can store a temporal shape and return to their original (permanent) shape simply by applying the proper stimulus, these materials have acquired application relevance in a variety of technological fields ranging from medical 2À5,21À25 to aeronautics. 26 These smart materials have offered technological promise since first reported by the end of the 1970s, where SMPs included cross-linked polyolefins and highly entangled polymers such as polynorbornene (ca. 3 Â 10 6 g/mol). 27 Gradually, the field migrated from the cross-linking of common polymers toward novel compositions and architectures suitable to a wide range of stimuli and even biodegradability. For example, one of us has reported hybrid and biodegradable SMPs from end-linking of low molecular weight (ca. 2000À4000 g/mol) network chains incorporating nanometer size hybrid moieties based on polyhedral oligosilsesquioxanes (POSS). 1À3 Here, POSS is an
The design of alternative earth-abundant van der Waals (vdW) nanoheterostructures for bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysis is of paramount importance to fabricate energy-related devices. Herein, we report a simple metal−organic framework (MOF)-derived synthetic strategy to fabricate low-dimensional (LD) nanohybrids formed by zerodimensional (0D) ZrO 2 nanoparticles (NPs) and heteroatomdoped two-dimensional (2D) carbon nanostructures. The 2D platforms controlled the electronic structures of interfacial Zr atoms, thus producing optimized electron polarization for boron and nitrogen-doped carbon (BCN)/ZrO 2 nanohybrids. X-ray photoelectron spectroscopy (XPS) and theoretical studies revealed the key role of the synergistic couple effect of boron (B) and nitrogen (N) in interfacial electronic polarization. The BCN/ZrO 2 nanohybrid showed excellent bifunctional electrocatalytic activity, delivering an overpotential (η 10 ) of 301 mV to reach a current density of 10 mA−cm −2 for the OER process and a half-wave potential (E 1/2 ) of 0.85 V vs reversible hydrogen electrode (RHE) for the ORR process, which are comparable to the state-of-the-art LD nanohybrids. Furthermore, BCN/ZrO 2 also showed competitive performances for water-splitting and zinc−air battery devices. This work establishes a new route to fabricate highly efficient multifunctional electrocatalysts by tuning the electronic polarization properties of 0D−2D electrochemical interfaces.
The rational design of high-performance trifunctional catalysts for oxygen reduction, oxygen and hydrogen evolution reactions is of vital importance for the implementation of green energy conversion technologies. Herein, trifunctional electrocatalysts...
Urease is a nickel-dependent amidohydrolase that catalyses the decomposition of urea into carbamate and ammonia, a reaction that constitutes an important source of nitrogen for bacteria, fungi and plants. It is recognized as a potential antimicrobial target with an impact on medicine, agriculture, and the environment. The list of possible urease inhibitors is continuously increasing, with a special interest in those that interact with and block the flexible active site flap. We show that disulfiram inhibits urease in Citrullus vulgaris (CVU), following a non-competitive mechanism, and may be one of this kind of inhibitors. Disulfiram is a well-known thiol reagent that has been approved by the FDA for treatment of chronic alcoholism. We also found that other thiol reactive compounds (L-captopril and Bithionol) and quercetin inhibits CVU. These inhibitors protect the enzyme against its full inactivation by the thiol-specific reagent Aldrithiol (2,2 -dipyridyl disulphide, DPS), suggesting that the three drugs bind to the same subsite. Enzyme kinetics, competing inhibition experiments, auto-fluorescence binding experiments, and docking suggest that the disulfiram reactive site is Cys592, which has been proposed as a "hinge" located in the flexible active site flap. This study presents the basis for the use of disulfiram as one potential inhibitor to control urease activity.
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