Plasmon Coupling-Enhanced Raman Sensing Platform Integrated with Exonuclease-Assisted Target Recycling Amplification for Ultrasensitive and Selective Detection of microRNA-21.

A "signal-off" surface-enhanced Raman scattering (SERS) platform has been constructed for ultrasensitive detection of miRNA-21 by integrating exonuclease-assisted target recycling amplification with a plasmon coupling enhancement effect. On this platform, Raman-labeled Au nanostar (AuNS) probes can be covalently linked with the thiolated aptamer (Apt) on the Au-decorated silicon nanowire arrays (SiNWAs/Au) substrate, creating a coupled electromagnetic field between the substrate and the probes to enhance Raman signal. In the presence of miRNA-21, T7 exonuclease specifically hydrolyzed Apt on Apt/miRNA duplex to release miRNA-21. The regenerated element could then initiate another cycle of Apt/miRNA duplex formation and Apt cleavage. Correspondingly, the capture ability of substrate toward probes and the plasmon coupling effect between them were both diminished, giving a prominent attenuation of Raman intensity that can work as the detection signal. Due to the cascading integration between the target cycle process and the plasmon coupling effect, the present platform displayed a very low detection limit (0.34 fM, 3σ) for miRNA-21 detection. Furthermore, it was proven to be effective for analyzing miRNA-21 in biological samples and distinguishing the expression levels of miRNA-21 in MCF-7 cells and NIH3T3 cells, which became a promising tool to monitor miRNA-21 in cancer auxiliary diagnosis and drug screening.

Nickel Molybdenum Nitride Nanorods Grown on Ni Foam as Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splitting.

Non-noble-metal electrocatalysts for water splitting hold great promises for developing sustainable and clean energy sources. Herein, a highly efficient bifunctional electrode consisting of Ni-doped molybdenum nitride nanorods on Ni foam is prepared through topotactic transformation of NiMoO4 nanorods that are in situ hydrothermally grown on Ni foam. The electrode not only contains rich, accessible, electrochemically active sites but also possesses extraordinary chemical stability. It exhibits excellent hydrogen evolution reaction and oxygen evolution reaction performance in 1.0 M KOH with low overpotentials of 15 and 218 mV, respectively, at a current density of 10 mA cm-2, superior to the commercial benchmark materials Pt/C and RuO2 under the same condition. A simple water electrolyzer using the obtained electrode as both the anode and cathode needs a very low cell potential of 1.49 V to reach a current density of 10 mA cm-2 and maintains stability for 110 h without degradation. The excellent performance of the electrode could be attributed to the formation of highly conductive, corrosion- and oxidation-resistant metal nitrides and the synergetic effect between intimately interconnected, electrochemically active nickel molybdenum nitride and Ni or NiO nanoparticles. This study shows that the use of transition metal nitrides in combination of nanostructured heterojunctions of multiple active components enables one to develop highly stable and efficient water electrolyzers without precious metals. The preparative strategy used in this work could be applied to devise new electrocatalysts.