Molecular Dipole Optimized Hybrid Metal Halide for Piezoelectric Ultrasound Monitoring of Aquatic Organisms.

Zhao, Chen; Gong, Yong-Ji; An, Lian-Cai; Zhang, Ying; Yang, Hai-Run; Li, Zhi-Gang; Qin, Jun; Li, Wei et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Piezoelectric hybrid metal halides are promising materials for energy conversion and sensing, yet their design has largely relied on empirical approaches. Here, we report the design and synthesis of a zero-dimensional piezoelectric hybrid metal halide, (HP-MeV)SnCl<sub>6</sub> (HP-MeV = N-(3-hydroxypropyl)-N'-methyl-4,4'-bipyridinium), via amplification of the dipole moment of the organic amine cation. Substituting MeV with HP-MeV increases the molecular dipole from 3.17 to 12.07 debye, transforming centrosymmetric (MeV)SnCl<sub>6</sub> into a noncentrosymmetric structure. Density functional theory reveals that (HP-MeV)SnCl<sub>6</sub> exhibits low elastic moduli, high piezoelectric strain coefficients, and reduced acoustic impedance. Composite devices with (HP-MeV)SnCl<sub>6</sub>/polydimethylsiloxane demonstrate efficient energy harvesting and sensitive human motion sensing. Notably, these devices achieve >90% fidelity in underwater ultrasound detection, enabling ultrasound monitoring of aquatic biological activity. This work establishes a rational molecular engineering route for piezoelectric hybrid metal halides and expands their potential for biological and environmental sensing applications.