Metal–organic frameworks (MOFs) have been widely used as supporting materials to load or encapsulate metal nanoparticles for electrochemical sensing. Herein, the influences of morphology on the electrocatalytic activity of Co-containing zeolite imidazolate framework-67 (ZIF-67) as supporting materials were studied. Three types of morphologies of MOF ZIF-67 were facilely synthesized by changing the solvent because of the influence of the polar solvent on the nucleation and preferential crystal growth. Two-dimensional (2D) ZIF-67 with microplate morphology and 2D ultrathin ZIF-67 nanosheets were obtained from pure H2O (H-ZIF-67) and a mixed solution of dimethylformamide and H2O (D-ZIF-67), respectively. Three-dimensional ZIF-67 with rhombic dodecahedron morphology was obtained from pure methanol (M-ZIF-67). Then, one-step electrodeposition of silver nanostructures on ZIF-67-modified glassy carbon electrode (Ag/ZIF-67/GCE) was performed for the reduction of hydrogen peroxide (H2O2). Cyclic voltammetry can be used to investigate the electrocatalytic activity of Ag/ZIF-67/GCE, and Ag/H-ZIF-67/GCE displayed the best electrocatalytic property than Ag/D-ZIF-67/GCE and Ag/M-ZIF-67/GCE. The electrochemical H2O2 sensor showed two wide linear ranges of 5 μM to 7 mM and 7 to 67 mM with the sensitivities of 421.4 and 337.7 μA mM–1 cm–2 and a low detection limit of 1.1 μM. In addition, the sensor exhibited good selectivity, high reproducibility, and stability. Furthermore, it has been utilized for real-time detection of H2O2 from HepG2 human liver cancer cells. This work provides a novel strategy for enhancing the detection performance of electrochemical sensors by changing the crystalline morphologies of supporting materials.

No abstract

Over the past decade, the use of metal–organic framework derived materials has emerged as a novel direction to prepare high performance polymer composites. In this work, nickel based metal–organic framework (Ni-MOF) was synthesized via a cost-effective and environmentally acceptable approach. Ni-MOF derived hierarchically mesoporous nickel phosphate was prepared via a facile hydrothermal method. Morphological evolution from Ni-MOF to nickel phosphate during the synthesis was clearly revealed. The microsized rod-like nickel phosphate was evaluated in both smoke suppression and mechanical enhancement of intumescent flame retardant wood fiber/poly­(lactic acid) system. The cone calorimeter test showed a 43% reduction in total smoke production when 5 wt % ammonium polyphosphate was substituted by nickel phosphate. More importantly, both tensile and impact strength of the composites were improved with the addition of nickel phosphate. The as-synthesized nickel phosphate proved to be a promising substitution for ammonium polyphosphate in wood fiber/poly­(lactic acid) composites.

No abstract

SnO2 and SnO2@C have been successfully synthesized with a simple hydrothermal procedure combined with heat treatment, and their performance as cathode catalysts of Li-air batteries has been comparatively evaluated and discussed. The results show that both SnO2 and SnO2@C are capable of catalyzing oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) at the cathode of Li-air batteries, but the battery with SnO2@C displays better performance due to its unique higher conductivity, larger surface area, complex pore distribution, and huge internal space.