Time-domain Vernier effect-based optical fiber sensor.

In this Letter, we demonstrate an easy-to-fabricate time-domain Vernier-effect-based sensor. An all-fiber variable optical delay line (VODL) is utilized to drive an OPD scan of two interferometers simultaneously, and fiber Bragg gratings are used to filter out two slightly detuned time-domain interferometric signals. Then two normalized interferograms with different spatial frequencies can be achieved and utilized to generate an envelope modulation, viz., a Vernier envelope, with enhanced sensitivity in comparison to the native state of the interferometers used. The sensitivity magnification factor of our structure can be regulated simply via altering the resonant wavelength difference of FBGs rather than optimizing the OPDs of the interferometers. The proposed sensor is independent of the precise and complicated fabrication procedures. The Vernier signal can be demodulated without a broadband light source and spectrometer. We argue that the proposed structure may inspire a new concept for constructing simple and cheap Vernier effect-based sensors that are well suited for practical applications.

Visible light-driven H2O2 synthesis over Au/C3N4: medium-sized Au nanoparticles exhibiting suitable built-in electric fields and inhibiting reverse H2O2 decomposition.

Visible light-driven H2O2 production presents the unique merits of sustainability and environmental friendliness. The size of noble metal nanoparticles (NPs) determines their dispersion and electronic structure and greatly affects their photocatalytic activity. In this work, a series of sized Au NPs over C3N4 were modulated for H2O2 production. The results show that there is a volcanic trend in H2O2 with the decrease of Au particle size, and the highest H2O2 production rate of 1052 µmol g-1 h-1 is obtained from medium-sized Au particles (∼8.7 nm). The relationship between structure and catalytic performance is supported by experimental and theoretical methods. (1) First, medium-sized Au NPs promote photon absorption, and have a suitable built-in electric field at the heterojunction, which can be successfully tuned to achieve a more efficient h+-e- spatial separation. (2) Second, medium-sized Au NPs enhance O2 adsorption, and create selective 2e- O2 reduction reaction sites. (3) Particularly, medium-sized Au NPs promote the desorption of produced H2O2 and inhibit H2O2 decomposition, finally leading to the highest H2O2 selectivity. Excellent catalytic performance will be obtained by finely optimizing the particle size in a certain range. This work provides a new idea for preparing high efficiently photocatalysts for H2O2 production.

Current understanding of the role of DDX21 in orchestrating gene expression in health and diseases.

RNA helicases are involved in almost all biological events, and the DDXs family is one of the largest subfamilies of RNA helicases. Recently, studies have reported that RNA helicase DDX21 is involved in several biological events, specifically in orchestrating gene expression. Hence, in this review, we provide a comprehensive overview of the function of DDX21 in health and diseases. In the genome, DDX21 contributes to genome stability by promoting DNA damage repair and resolving R-loops. It also facilitates transcriptional regulation by directly binding to promoter regions, interacting with transcription factors, and enhancing transcription through non-coding RNA. Moreover, DDX21 is involved in various RNA metabolism such as RNA processing, translation, and decay. Interestingly, the activity and function of DDX21 are regulated by post-translational modifications, which affect the localization and degradation of DDX21. Except for its role of RNA helicase, DDX21 also acts as a non-enzymatic function in unwinding RNA, regulating transcriptional modifications and promoting transcription. Next, we discuss the potential application of DDX21 as a clinical predictor for diseases, which may facilitate providing novel pharmacological targets for molecular therapy.

Effects and Mechanisms of Cu Species in Fe-MOFs on Fenton-Like Catalytic Activity and Stability.

Fe-based MOFs (Fe-MOFs) are deemed promising Fenton-like catalysts due to their well-developed pores and accessible active sites. However, their inferior catalytic activity, iron leaching, and low H2O2 utilization always hinder their application as Fe-based MOF catalysts. In this work, we manipulated the structure of Fe-oxo nodes in MIL-88B(Fe) via a CuI species substitution method, affording a mixed-valence (Cu-incorporated Fe-MOFs) with highly improved Fenton-like performance. It is found that the CuI serves as a shuttle to promote transfer between FeII/FeIII, inducing the formation of a larger amount of stable FeII sites, which was proven by experimental and DFT calculation results. A linear relationship was observed for the Fenton-like performance and the amount of CuI species for the catalysts. The corresponding value of the •OH formation is 2.17 eV for Cu-incorporated MIL-88B(Fe), which is significantly lower than that of MIL-88B(Fe) (2.69 eV). Meanwhile, the enriched CuI species suppress Fe species leaching during the catalytic reaction. The Fe-ion leakage of 0.4Cu@MIL-88B is very tiny (0.01-0.03 mg/L), significantly less than that of MIL-88B (2.00-3.02 mg/L). At the same time, H2O2 utilization for 0.4Cu@ MIL-88B(Fe) is 88%, which is almost 4.4 times that of pure MIL-88B(Fe). This work provides insights into the rational design of Fe-MOFs as promising Fenton-like catalysts for wastewater treatment.