Single atom catalysts (SACs) have received considerable
attention
due to their high-atomic-utilization efficiency and tunable activity
and selectivity. Here, in combination of experiments and calculations,
we demonstrated that the electronic structures and the oxygen evolution
reaction (OER) activity of the confined Ni SAC in a nitrogen-doped
carbon nanotube are modulated by the encapsulated Ni nanoparticle
(Ni@NiNCNT). The synergistic interaction between Ni SAC and Ni nanoparticle
endows the Ni@NiNCNT with a satisfactory OER performance of 358 mV
to achieve 10 mA cm–2 current density and a Tafel
slope of 89 mV dec–1, superior to the control samples
and commercial RuO2. In addition, when employed as an air-cathode
catalyst for rechargeable zinc–air batteries (ZABs), a Ni@NiNCNT
modified battery outperformed a Pt/C+RuO2 modified battery,
with a higher power density and superior constant current charge–discharge
cycle stability for 40 h. Theoretical simulations further revealed
that the Ni nanoparticle can remarkably optimize the adsorption strength
of oxygen atom on Ni SAC, leading to a small overpotential of 0.22
V for the rate-limiting step of *O formation. Furthermore, the charge
transfer from Ni nanoparticle to Ni SAC, which handles Ni-d orbital
characters of Ni SAC and accordingly the adsorption strength toward
oxygenates, is responsible for the origin of the OER activity. Our
results provide a new way to tune electronic structures of the SAC
and thus to tune its catalytic activity and should be insightful for
designing new type electrocatalysts based on SAC.
Monitoring food quality throughout the food supply chain is critical to ensuring global food safety and minimizing food losses. Here we find that simply by mixing an aqueous solution of sugar-stabilized Ag+ and amines in an open vessel leads to the generation of Ag NPs and an intelligent evaluation system based on a colorimetric Ag+ probe is developed for real-time visual monitoring of food freshness. The self-assembly reaction between methylamine (MA) generated during meat storage and the colorimetric Ag+ probe produces different color changes that indicate changes in the quality of the meat. The colorimetric Ag+ probe was integrated into food packaging systems for real-time monitoring of chilled broiler meat freshness. The proposed evaluation system provides a versatile approach for detecting biogenic amines and monitoring chilled broiler meat freshness and it has the advantages of high selectivity, real-time and on-site measurements, sensitivity, economy, and safety and holds great public health significance.
Herein, we design and prepare large-area silver nanoparticle (Ag NP) films based on evaporation-induced self-assembly, which offers the visual and real-time detection of chilled broiler meat freshness. The color change is based on the fact that an increase in the biogenic amine (BA) concentration causes a change in the absorption wavelength of Ag NPs caused by aggregation and etch of the Ag NPs, resulting in a yellow to brown color change, thus enabling a naked-eye readout of the BA exposure. The Ag NP films exhibit a rapid, sensitive, and linear response to BAs in a wide detection range of 2 µM to 100 µM. The Ag NP films are successfully applied as a quick-response, online, high-contrasting colorimetric sensor for visual detection of the freshness of chilled broiler meat.
Meat waste is widely associated with spoilage caused by microbial growth and metabolism. Volatile compounds produced by microbial growth such as volatile sulfides could directly indicate the freshness of meat during distribution and storage. Herein, silver−iron nanotriangles (Ag-Fe NTs) for hydrogen sulfide (H 2 S) detection were developed via one-pot facile reflux reactions. The Ag-Fe NTs were integrated into food packaging systems for the rapid, real-time, and nondestructive detection of the freshness of chilled broiler poultry. The principle of color development is that an increase in the volatile sulfide content leads to a change in the absorption wavelength caused by the etching of the Ag-Fe NTs, resulting in a color change (yellow to brown). The minimum H 2 S concentrations detected by the naked eye and UV−vis spectrophotometer were 4 and 2 mg/m 3 , respectively. This label is economical and practical and can monitor the spoilage of chilled broiler meat products in real-time.
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