Isostructural lanthanide organic frameworks (Me2NH2)3[Ln3(FDC)4(NO3)4]·4H2O (Ln = Eu (1), Gd (2), Tb (3), H2FDC = 9‐fluorenone‐2,7‐dicarboxylic acid), synthesized under solvothermal conditions, feature a Ln‐O‐C rod‐packing 3D framework. Time‐resolved luminescence studies show that in 1 the energy difference between the H2FDC triplet excited state (17794 cm−1) and the 5D0 Eu3+ level (17241 cm−1) is small enough to allow a strong thermally activated ion‐to‐ligand back energy transfer. Whereas the emission of the ligand is essentially constant the 5D0→7F2 intensity is quenched when the temperature increases from 12 to 320 K, rendering 1 the first single‐lanthanide organic framework ratiometric luminescent thermometer based on ion‐to‐ligand back energy transfer. More importantly, this material is also the first example of a metal organic framework thermometer operative over a wide temperature range including the physiological (12‐320 K), upon excitation with visible light (450 nm).

demonstrated by using piezoelectric, electrostatic, electromagnetic, and triboelectric mechanisms for vibration energy harvesting. Even though the harvested power from these methods are small, it is sufficient to power small electronic devices, including light-emitting diodes, laser diodes, pH sensors, speed sensors, and toxic pollutant sensors. [6][7][8][9][10][11] Piezoelectric nanogenerator (PENG) has been most intensively studied because of its high conversion efficiency and compatible manufacturing process. [12][13][14][15][16][17][18] And it is found that piezoelectric materials polyvinylidene fluoride (PVDF) has demonstrated to be the largest piezoelectric constants in polymer. [19][20][21][22] To further this PVDF research for energy harvesting, Lee and co-workers introduced an enhanced piezoelectric energy harvesting by using graphene oxide which output voltage could reach to 4 V. [20] Wang and co-workers reported another enhanced sponge-like piezoelectric using PVDF, however the processing of this prototype is complicated and constrained in lab. [9] Recently, hybrid nanogenerators have attracted more and more attention. [23][24][25] Wang first described a hybrid triboelectric and electromagnetic harvester for the harsh environment. [23] Lee and co-workers reported a broadband nonlinear electromagnetic and triboelectric hybrid energy harvester. [24] However, the existing research using both electromagnetic and triboelectric method could harvest limited power due to the impedance mismatch. In this paper, we proposed a hybrid method using the piezoelectric and triboelectric method for energy harvesting. The designed PENG could greatly enhance the collection efficiency of mechanical energy with PVDF nanoparticles and PVDF/PTFE film, and the leaf-shaped woven fiber benefited the electric output for the TENG. In the end, a random test using finger tap was demonstrated the mechanical energy conversion performance by using eight light-emitting diodes (LED).

This paper reports zinc oxide (ZnO)-coated piezoelectret polypropylene (PP) microfibers with a structure of two opposite arc-shaped braces for enhanced mechanical energy harvesting. The ZnO film was coated onto PP microfibers via magnetron sputtering to form a ZnO/PP compound structure. Triboelectric Nanogenerator (TENG) based on ZnO/PP microfiber compound film was carefully designed with two opposite arc-shaped braces. The results of this study demonstrated that the mechanical energy collection efficiency of TENG based on piezoelectret PP microfiber was greatly enhanced by the coated ZnO and high-voltage corona charging method. We found that, with the step-increased distance of traveling for the movable carbon black electrode, an electrical power with an approximately quadratic function of distance was generated by this mechanical-electrical energy conversion, because more PP microfibers were connected to the electrode. Further, with a full contact condition, the peak of the generated voltage, current, and charges based on the ZnO/PP microfibers by this mechanical-electrical energy conversion with 1 m/s reached 120 V, 3 μA, and 49 nC, respectively. Moreover, a finger-tapping test was used to demonstrate that the ZnO/PP microfiber TENG is capable of lighting eight light-emitting diodes.

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