Facile Method for the Controllable Synthesis of Cs_<i>x</i>Pb_<i>y</i>Br_<i>z</i>‑Based Perovskites

We report a facile method to realize the selective synthesis of Cs_<i>x</i>Pb_<i>y</i>Br_<i>z</i>-based perovskites, including CsPbBr₃, Cs₄PbBr₆ and CsPb₂Br₅. The use of an appropriate amount of <i>N</i>,<i>N</i>-dimethylformamide (DMF) solvent is experimentally determined to play a critical role in the controlled formation of various perovskite products. With continuously increasing DMF concentration, first CsPbBr₃ nanocrystals with tunable size can be achieved, and then the production of Cs₄PbBr₆ and CsPb₂Br₅ perovskite analogues is successively realized. Our findings present a novel path for the controlled synthesis of other perovskite analogues for specific applications

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