Metal–Organic Framework-Derived Hollow Hierarchical Co₃O₄ Nanocages with Tunable Size and Morphology: Ultrasensitive and Highly Selective Detection of Methylbenzenes

Nearly monodisperse hollow hierarchical Co₃O₄ nanocages of four different sizes (∼0.3, 1.0, 2.0, and 4.0 μm) consisting of nanosheets were prepared by controlled precipitation of zeolitic imidazolate framework-67 (ZIF-67) rhombic dodecahedra, followed by solvothermal synthesis of Co₃O₄ nanocages using ZIF-67 self-sacrificial templates, and subsequent heat treatment for the development of high-performance methylbenzene sensors. The sensor based on hollow hierarchical Co₃O₄ nanocages with the size of ∼1.0 μm exhibited not only ultrahigh responses (resistance ratios) to 5 ppm <i>p</i>-xylene (78.6) and toluene (43.8) but also a remarkably high selectivity to methylbenzene over the interference of ubiquitous ethanol at 225 °C. The unprecedented and high response and selectivity to methylbenzenes are attributed to the highly gas-accessible hollow hierarchical morphology with thin shells, abundant mesopores, and high surface area per unit volume as well as the high catalytic activity of Co₃O₄. Moreover, the size, shell thickness, mesopores, and hollow/hierarchical morphology of the nanocages, the key parameters determining the gas response and selectivity, could be well-controlled by tuning the precipitation of ZIF-67 rhombic dodecahedra and solvothermal reaction. This method can pave a new pathway for the design of high-performance methylbenzene sensors for monitoring the quality of indoor air

Inhibitive effect of bithiophene carbonitrile derivatives on carbon steel corrosion in 1 M HCl solution: experimental and theoretical approaches

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. The effect of [2,2':5',2?-terthiophene]-5-carbonitrile and its derivatives on carbon steel surface in 1 M HCl solution was deliberated at (25 °C) using weight loss technique in addition to electrochemical techniques such as electrochemical frequency modulation, potentiodynamic polarization, and electrochemical impedance spectroscopy. Results gained from all techniques employed are in good coincidence with each other. Results illustrate that [2,2':5',2?-terthiophene]-5-carbonitrile is considered as the best inhibition efficiency at 18 × 10-6 M additive concentration. Efficiency was found to rise with rising concentration and decrease with rising temperature. Adsorptions of organic derivatives on the carbon steel surface follow the Langmuir isotherm. Polarization studies showed that inhibitors are mixed type. From weight loss technique at different temperature data, we calculated the thermodynamic functions of adsorption process and analyze the mechanism between inhibitor and carbon steel surface. The morphology of steel surface was estimated by using SEM, EDX, AFM, and FT-IR. The inhibition performance had been discussed also using theoretical study by quantum chemical calculations and molecular dynamic simulation. [Figure not available: see fulltext.]