Search

Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt–nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce the oxidized TMB (oxTMB). And the aromatic primary amino group of oxTMB reacts with nitrite (NO2−) to form diazo groups. Based on this background, we developed a cascade system of a Co-N-C-catalyzed oxidation reaction and a diazotization reaction for nitrite determination. The low detection limit (0.039 μM) indicates that Co-N-C is superior compared with the vast majority of previously reported nitrite assays. This study not only provides a novel nanozyme with sufficiently dispersed active sites, but it also further applies it to the determination of nitrite, which is expected to expand the application of nanozymes in colorimetric analysis. [ABSTRACT FROM AUTHOR]

High levels of uric acid (UA) in humans can cause a range of diseases, and traditional assays that rely on uric acid enzymes to break down uric acid are limited by the inherent deficiencies of natural enzymes. Fortunately, the rapid development of nanozymes in recent years is expected to solve the above-mentioned problems. Hence, we used a host–guest strategy to synthesize a platinum nanoparticle confined in a metal–organic framework (Pt NPs@ZIF) that can sensitively detect UA levels in human serum. Unlike previously reported free radical-catalyzed oxidation systems, its unique electron transfer mechanism confers excellent peroxidase-like activity to Pt NPs@ZIF. In addition, UA can selectively inhibit the chromogenic reaction of TMB, thus reducing the absorbance of the system. Therefore, using the peroxidase-like activity of Pt NPs@ZIF and using TMB as a chromogenic substrate, UA can be detected directly without relying on natural enzymes. The results showed a relatively wide detection range (10–1000 μM) and a low detection limit (0.2 μM). Satisfactory results were also obtained for UA in human serum. This study with simple operation and rapid detection offers a promising method for efficiently detecting UA in serum. [ABSTRACT FROM AUTHOR]

ZIF-8-induced photocatalytic CeO2/ZnO nanobelts with curled edges were synthesized by following a facile electrospinning method for low-cost photodecomposition of methylene blue (MB). Phase structure and morphological evolution of different samples can be dominantly adjusted by introducing appropriate amount of zeolitic imidazolate framework-8 (ZIF-8) into the precursor solution. CeO2/ZnO heterostructures exhibit the optimal 96.59% photodegradation of MB organic pollutant in 70 min, approximately 7.43 times than that of pure CeO2. The curled microstructure can produce tunable surface activity and a unique electron transport process, facilitating the cycling efficiency of Ce3+/Ce4+ pairs on the surface of materials. Meanwhile, the formation of CeO2-ZnO heterojunctions contributes to regulating the crystal nucleation and growth during the high-temperature reaction and reducing the recombination rate of electron/hole pairs during the photocatalytic degradation. Thus, the obtained CeO2/ZnO composites may be a promising candidate for MB degradation in industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

One-dimensional MoO3/ZnMoO4/CoMoO4 hierarchical structures with sequential layered and granulated constitutional units on surfaces have been successfully designed and fabricated, mainly derived through the introducing of bi-component MOF and the effective element migration mechanism. Based on the different adding ratios of Co and Zn sources, the obtained hierarchical structure can be composed of the central MoO3 nanobelts, the outer uniform ZnMoO4 shell, and the outermost tunable CoMoO4 nanoparticles. The well-organized ZnMoO4 shell and CoMoO4 nanoparticles grown on MoO3 surface provide favorable opportunities for improving the surface absorption and chemical reaction, electron transport paths, and electron transfer efficiency. Compared with MoO3 nanobelts and MoO3/ZnMoO4 composites, the optimal MoO3/ZnMoO4/CoMoO4 sensors exhibit superior gas-sensing response value of 505.67 for 10 ppm triethylamine (TEA) at 270 °C as well as excellent gas selectivity and long-term stability. The superior gas-sensing performance is mainly attributed to the combination of the designed multi-level effective heterojunctions, large specific surface area, the enhanced surface adsorption/reaction, and the particular surface/interface electron transport process. More importantly, the current work presents a new insight of original gas-sensing MoO3/ZnMoO4/CoMoO4 hierarchical structures for detecting the variation of freshness in shrimp storage, indicating the practical applications in chemical detector and biosensor fields. [ABSTRACT FROM AUTHOR]

Porous MoO3/V0.13Mo0.87O2.935 heterostructures self-assembled with 2D nanosheets have been primarily prepared by a facile method for effectively detecting ethanol at room temperature. The V0.13Mo0.87O2.935 phase contributes to modified microspheres and improved surface/interface structures. The enhanced sensing mechanism benefits from the effects of MoO3–V0.13Mo0.87O2.935 heterojunctions and tunable microstructure. [ABSTRACT FROM AUTHOR]

Tunable In2O3 hierarchical microstructures consisting of single crystalline octahedral particles and polycrystalline fibers have been synthesized by one-step electrospinning combined with a subsequent calcination process, in which their enhanced gas-sensing mechanism is mainly ascribed to the synergistic effect of two typical structural units. [ABSTRACT FROM AUTHOR]