Growth of CeO2 nanocubes showing size-dependent optical and oxygen evolution reaction behaviors.

CeO2 nanocubes with average sizes of 9, 13, and 18 nm have been synthesized by preparing a slightly basic aqueous mixture of Ce(NO3)3, Na2SO4, and NH4OH and heating the solution to 100 to 150 °C in 4 or 9 h. The nanocubes possess high crystalline quality. Their band gaps decrease gradually beyond the quantum confinement regime from 3.57 eV to 3.45 eV with increasing particle sizes. The 9 nm CeO2 nanocubes have the most positive valence band energy and correspondingly they exhibit the best electrochemical oxygen evolution reaction activity. Since band gaps of semiconductor nanocrystals can be tuned substantially through particle size control to yield different band energies, this fact can be utilized to enhance the electrochemical and photocatalytic properties.

[Study on quality standard of Mucuna pruriens var. utilis].

OBJECTIVE: To provide scientific basis for the utilization and development of Mucuna pruriens var. utilis by establishing its quality control standard. METHODS: The bioactive constituents were analyzed by TLC and HPLC. Moisture, ash and the extracts of Mucuna pruriens var. utilis were all determined. RESULTS: The TLC spots of levodopa had similar color with the control group at the same position. The results of HPLC quantitative analysis showed that the linear range of levodopa was 26.45 to approximately 132.25 microg/mL, r = 0.9992, and the average recovery rate was 103.8%, RSD = 1.85%. CONCLUSIONS: This method is convenient, accurate, reliable with good reproducibility, so it can be used to establish quality standard for the medicinal material.

Rapid mechanochemical encapsulation of biocatalysts into robust metal-organic frameworks.

Metal-organic frameworks (MOFs) have recently garnered consideration as an attractive solid substrate because the highly tunable MOF framework can not only serve as an inert host but also enhance the selectivity, stability, and/or activity of the enzymes. Herein, we demonstrate the advantages of using a mechanochemical strategy to encapsulate enzymes into robust MOFs. A range of enzymes, namely ß-glucosidase, invertase, ß-galactosidase, and catalase, are encapsulated in ZIF-8, UiO-66-NH2, or Zn-MOF-74 via a ball milling process. The solid-state mechanochemical strategy is rapid and minimizes the use of organic solvents and strong acids during synthesis, allowing the encapsulation of enzymes into three prototypical robust MOFs while maintaining enzymatic biological activity. The activity of encapsulated enzyme is demonstrated and shows increased resistance to proteases, even under acidic conditions. This work represents a step toward the creation of a suite of biomolecule-in-MOF composites for application in a variety of industrial processes.