Thermal energy was shown to be efficiently converted into electrical power in a thermally regenerative ammonia-based battery (TRAB) using copper-based redox couples [Cu(NH 3 ) 4 2+ /Cu and Cu(II)/Cu].Ammonia addition to the anolyte (2 M ammonia in a copper-nitrate electrolyte) of a single TRAB cell produced a maximum power density of 115 AE 1 W m À2 (based on projected area of a single copper mesh electrode), with an energy density of 453 W h m À3 (normalized to the total electrolyte volume, under maximum power production conditions). Adding a second cell doubled both the voltage and maximum power. Increasing the anolyte ammonia concentration to 3 M further improved the maximum power density to 136 AE 3 W m À2 . Volatilization of ammonia from the spent anolyte by heating (simulating distillation), and re-addition of this ammonia to the spent catholyte chamber with subsequent operation of this chamber as the anode (to regenerate copper on the other electrode), produced a maximum power density of 60 AE 3 W m À2 , with an average discharge energy efficiency of $29%(electrical energy captured versus chemical energy in the starting solutions). Power was restored to 126 AE 5 W m À2 through acid addition to the regenerated catholyte to decrease pH and dissolve Cu(OH) 2 precipitates, suggesting that an inexpensive acid or a waste acid could be used to improve performance.These results demonstrated that TRABs using ammonia-based electrolytes and inexpensive copper electrodes can provide a practical method for efficient conversion of low-grade thermal energy into electricity. Broader contextThe utilization of waste heat for power production would enable additional electricity generation without any additional consumption of fossil fuels. Thermally regenerative batteries (TRBs) allow a carbon neutral approach for the storage and conversion of waste heat into electrical power, with potentially lower costs than solid-state devices. Here we present a highly efficient, inexpensive, and scalable ammonia-based TRB (TRAB) where electrical current is produced from the formation of copper ammonia complex. The ammonia can then be captured and concentrated by distillation of the anolyte, allowing recharge of the system. The voltage created by ammonia addition in the anolyte results in copper deposition onto the cathode, and loss of copper from the anode. However, by reversing the function of electrodes in the next cycle, there is no net loss of copper. With a 3 M anolyte ammonia, a TRAB produced the highest power density ever obtained for an aqueous-based, thermoelectrochemical system, of 136 AE 3 W m À2 . This power density was substantially higher than those produced using salinity gradient energy technologies based on generating salty and less-salty solutions using waste heat. This TRAB technology therefore represents a new and promising approach for efficient harvesting of low-grade waste heat as electrical power.

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Multimodal molecular imaging has shown promise as a complementary approach to thrombus detection. However, the simultaneous noninvasive detection and lysis of thrombi for cardiovascular diseases remain challenging. Herein, a perfluorohexane (PFH)-based biocompatible nanostructure was fabricated, namely, as-prepared Fe3O4-poly­(lactic-co-glycolic acid)-PFH-CREKA nanoparticles (NPs), which combine phase transition (PT) thrombolysis capabilities with properties conducive to multimodal imaging. This well-developed PT agent responded effectively to low-intensity focused ultrasound (LIFU) by triggering the vaporization of liquid PFH to achieve thrombolysis. The presence of the CREKA peptide, which binds to the fibrin of the thrombus, allows targeted imaging and efficacious thrombolysis. Then, we found that, compared with thrombolysis using a non-phase-transition agent, PT thrombolysis can produce a robust decrease in the thrombus burden regardless of the acoustic power density of LIFU. In particular, the reduced energy for LIFU-responsive PT during the lysis process guarantees the superior safety of PT thrombolysis. After injecting the NPs intravenously, we demonstrated that this lysis process can be monitored with ultrasound and photoacoustic imaging in vivo to evaluate its efficacy. Therefore, this nonpharmaceutical strategy departs from routine methods and reveals the potential use of PT thrombolysis as an effective and noninvasive alternative to current thrombolytic therapy.

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