A turn-on fluorescent sensing platform based on an ultralow concentration of Al-metal organic frameworks for the detection of aflatoxin B 1 has been developed for the first time. This fluorescence turn-on sensor exhibits the largest fluorescence enhancement (or quenching) constant value of 179404 M −1 among all luminescence-based chemical sensors reported till date. Moreover, the sensor afforded a rapid detection of aflatoxin B 1 , with a linear response in the concentration range of 0.05–9.61 μM and a low detection limit of 11.67 ppb. Additionally, the fabricated sensor showed good repeatability, reproducibility, stability, and selectivity. Most importantly, the practical application of this sensor has been demonstrated by detecting aflatoxin B 1 in complex tea samples with low relative standard deviation (≤7.72%; n = 3) and satisfactory recoveries. In summary, the proposed method has great potential as a simple, sensitive and selective strategy for monitoring aflatoxin B 1 in food samples.
Yan Zhang,Yu Zhou,Zonghua Wang,Shenlong Zhao,Chunhui Tan,Jishi Chen
Exploring cheap and stable electrocatalyst for the oxygen reduction reaction (ORR) is now an important issue for the large-scale application of fuel cells. Herein, we have demonstrated a facile synthesis of Nitrogen-doped porous carbons (NPC-MILs) for oxygen reduction reaction by using an amine functionalized Al-MOFs (NH 2 -MIL-53(Al)) as the precursor with both nitrogen source and carbon source. NPC-MILs as metal-free electrocatalysts are demonstrated promising potential for ORR. The optimized NPC-MIL-900 (carbonized at 900 °C) exhibits a likeness four-electron process and its ORR catalytic activity can be comparable to commercial Pt/C. Furthermore, chronoamperometric measurement shows that only 13% loss at the current density is occurred after 40000 s, whereas the corresponding current density loss at the Pt/C (20wt%) is as high as 31%. Chronoamperometric responses also show the NPC-MIL-900 catalyst has higher resistance to methanol in alkaline electrolyte than Pt/C. Those indicate that the NPC-MIL-900 has potential application in fuel cells.
MOFs (metal-organic frameworks) are stable materials with both organic and inorganic pores, and possess high surface area fascinating structures. Owing to the unique octahedral of aluminum center and strong Al–O bonds, Al-based MOFs show excellent thermal stability. In this paper, MIL-96(Al) is proved to be effective at dispersing Pt particles evenly and sparsely as it is employed as catalyst support. MIL-96(Al) is synthesized via a water based route and different contents of Pt particles are directly deposited on the surface of MIL-96 in one step by hydrothermal method to prepare Pt X MIL-96 (x represents Pt content) catalysts. The catalyst are sprayed evenly on carbon paper, with Pt content of 0.03%, 0.11%, 0.27% and 0.41%, respectively, and are applied in a gas diffusion reactor with snakelike flow field for low temperature H 2 -SCR. For Pt 5 MIL-96/CP, the NO removal efficiency can reach up to 100% at 60 °C. Electron transfer between Pt and MIL-96 is observed via X-ray photoelectron spectron (XPS). It reveals that the deposited Pt is in metallic state. Meanwhile, the electronic structure of MIL-96 is kept intact in the process of Pt depositing. The excellent performance of Pt 5 MIL-96/CP catalyst strongly suggests its potential application.
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