Chemoselective Synthesis of 3‑Bromomethyloxindoles via Visible-Light-Induced Radical Cascade Bromocyclization of Alkenes

A novel visible-light-induced radical cascade bromocyclization of N-arylacrylamides has been accomplished. This reaction overcomes the overbromination at the benzene rings suffered in traditional electrophilic reactions, thus enabling the first highly chemoselective synthesis of valuable 3-bromomethyloxindoles. The combination of pyridine and anhydrous medium is identified as the key factor for the high chemoselectivity in the current photoreaction system, which might work by suppressing the in situ generation of low-concentration Br2 from N-bromosuccinimide. Moreover, the mild reaction conditions ensure the generation of a wide range of the new desired products with excellent functional group tolerance

Large-Scale Fabrication of Suspended, Aligned, and Strained Single-Walled Carbon Nanotube Networks

Large-scale fabrication of suspended single-walled carbon nanotubes remains a challenge, especially at specific locations and in specific directions. In this work, we demonstrate an effective, fast and large-scale technique to fabricate suspended, strained, and aligned SWNT networks, which is based on a dynamic motion of silver liquid to suspend and align the SWNTs between each two prefabricated palladium patterns in high temperature. The SWNTs are aligned in eight directions: up, down, left, right, upper right, lower right, upper left, and lower left. The simulated calculations show that the driving force leading the silver liquid motion on the substrate is around 0.66 μN. The Raman spectra of the SWNTs network were measured, and the downshift of the G+ band indicates that, for the suspended SWNTs, the uniaxial strain is around 0.13%. This technique could be extended to two-dimensional material systems and open the pathway toward better optoelectronic and nanoelectromechanical systems

Energy Harvesting from the Mixture of Water and Ethanol Flowing through Three-Dimensional Graphene Foam

In this work, the electrical conductance and induced current of three-dimensional graphene foam (GF) are investigated when the mixture of water and ethanol flows through it. When different mixing ratios of ethanol:water (ethanol:water = 25:75, 50:50, 75:25, and 100:0 by volume) flow through the GFs, their electrical conductance is almost the same as that of the original GF. Meanwhile, the induced current can be obtained when the mixture flows through the GF. The direction of induced current depends on that of the flow of the mixture, the value of induced current has no dependence on the flow direction of the mixture but is closely related to the flow velocity and polarity of the mixture. The mechanism of the induced electricity is discussed, which is attributed to the coupling of flowing solution molecules with the charge carriers of graphene at the solid/liquid interface. These results indicate that GFs have a bright potential application in realizing the self-powered function of nano/micro electromechanical systems (N/MEMS) in many special environments