Ni/Co/Co3O4@C nanorods derived from a MOF@MOF hybrid for efficient overall water splitting.

The design of nanostructured materials for efficient bifunctional electrocatalysts has gained tremendous attention, yet developing a fast and effective synthesis strategy remains a challenge. Here, we present a fast and scalable synthetic method of Ni/Co/Co3O4@C nanorods for efficient overall water splitting. Using microwave synthesis, we first produced a unique Ni-MOF@Co-MOF in a few minutes. Subsequently, we transformed the MOF@MOF into hybrid Ni/Co/Co3O4 nanoparticles covered with graphitic carbon in a few seconds using laser-scribing. The prepared bimetallic catalysts showed remarkably low overpotentials of 246 mV for the oxygen evolution reaction (OER) and 143 mV for the hydrogen evolution reaction (HER) at a current density of 30 mA cm-2. An electrolyzer assembled with the bimetallic catalysts delivered a high current density of 20 mA cm-2 at a voltage of 1.6 V and exhibited good durability (nearly 91.6% retention even after a long-running operation of 24 h at a voltage of 1.52 V). Our proposed method could serve as a powerful method for creating various multimetallic hybrid nanocatalysts with unique hierarchical structures from diverse MOFs.

Graphitic Carbon with MnO/Mn7 C3 Prepared by Laser-Scribing of MOF for Versatile Supercapacitor Electrodes.

Pseudocapacitive materials encapsulated in conductive carbon matrix are of paramount importance to develop energy storage devices with high performance and long lifespan. Here, via simple laser-scribing, the Mn-based metal-organic framework [EG-MOF-74(Mn)] is transformed into pseudocapacitive hybrid MnO/Mn7 C3 encapsulated in highly conductive graphitic carbon. It is revealed that the rapid carbothermic reduction of MnO (C + MnO → C' + Mn7 C3 + CO) leads to the formation of the intermediate pseudocapacitive MnO/Mn7 C3 and the concurrent catalytic graphitization of disordered carbon. This reaction produces a new type of pseudocapacitive material in the form of MnO/Mn7 C3 fully embedded in highly conductive graphitic carbon. Thanks to the synergistic effect of the MnO/Mn7 C3 nanoparticles and the graphitic carbon, the composite exhibits a high specific capacitance of 403 F g-1 with excellent stability. Asymmetric coin-cell supercapacitors based on the composite demonstrate high energy (29.2 Wh kg-1 ) and power densities (8000 W kg-1 ) with a long lifespan. Prototypes of flexible paper-based supercapacitors made of the composite also show great potential toward applications of flexible electronics.

Micellization-induced amplified fluorescence response for highly sensitive detection of heparin in serum.

Fluorescence-based assays should be feasible in aqueous media for effectively detecting the biological factors. However, numerous sensors have limited signal transductions and low fluorescence quantum yields due to the ingerently reduced excited state energy of fluorophores in aqueous solution, which reduces their sensitivity. This necessitates a smart sensing approach with an amplified fluorescence response for analytes in aqueous solution. Herein, a new building block which self-assembles in aqueous media, giving a micellar sturcuture with the hydrophobic π-extended conjugated system at the core and hydrophilic groups at the periphery, was devised for the first time. We demonstrated that the aggregated fluorophores in a micelle induce amplified fluorescence quenching, in which the excited electron efficiently migrates through π-extended conjugated system in a micelle, as in a polymeric system. Such feature differentiates this sensing approach from the numerous fluorescence-based tools previously developed for sensitive detection. This new system exhibited highly sensitive signal transduction for specific analytes even under actual bioanalytical conditions.