Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Self-assembled polymer/porous silicon nanocomposites overcome intracellular and systemic barriers for in vivo application of peptide nucleic acid (PNA) anti-microRNA therapeutics. Porous silicon (PSi) is leveraged as a biodegradable scaffold with high drug cargo loading capacity. Functionalization with a diblock polymer improves PSi nanoparticle colloidal stability, in vivo pharmacokinetics, and intracellular bioavailability through endosomal escape, enabling PNA to inhibit miR-122 in vivo.

Amorphous Zn1−xMgxO (α-Zn1−xMgxO) ternary alloy thin films across the full compositional range were synthesized by a low-cost sol-gel method on quartz substrates. The amorphous property of the α-Zn1−xMgxO films was verified by x-ray diffraction, and atomic force microscopy revealed a smooth surface with sub-nanometer root-mean square roughness. The current phase segregation issue limiting application of crystalline Zn1−xMgxO with 38% < x < 75% was completely eliminated by growing amorphous films. Optical transmission measurements showed high transmissivity of more than 90% in the visible and near infrared regions, with optical bandgap tunability from 3.3 eV to more than 6.5 eV by varying the Mg content.

The thermal stability of CdZnO / ZnO multi-quantum-well ͑MQW͒ structures was studied using rapid thermal annealing in nitrogen from 300 to 750°C. Photoluminescence ͑PL͒ emission from the MQWs was studied while varying the annealing temperature and time. For 15 min annealings, the PL center wavelength showed a 7 nm reduction for temperatures up to 650°C. Above 650°C, the wavelength changed rapidly, with a 50 nm reduction at 750°C. Annealing at 700°C for up to 20 min produced a systematic reduction in PL wavelength up to 39 nm. The data suggest that CdZnO / ZnO MQWs are relatively stable for nitrogen annealing below 650°C for times up to 15 min.

Articles you may be interested inThe effect of oxygen flow rate and radio frequency plasma power on cubic ZnMgO ultraviolet sensors grown by plasma-enhanced molecular beam epitaxy Appl. Phys. Lett. 103, 031114 (2013); 10.1063/1.4815995 Molecular beam epitaxy-grown wurtzite MgS thin films for solar-blind ultra-violet detection Appl. Phys. Lett. 102, 171104 (2013); 10.1063/1.4803000 Realization of Mg ( x = 0.15 ) Zn ( 1 − x = 0.85 ) O -based metal-semiconductor-metal UV detector on quartz and sapphire