BaTiO3 nanocrystal-mediated micro pseudo-electrochemical cells with ultrasound-driven piezotronic enhancement for polymerization

Highlights: • A micro pseudo-electrochemical polymerization reaction was proposed. • Two end-to-end BaTiO₃ nanocubes can work as a micro electrochemical cell. • The electric potential is derived from the opposite spontaneous polarized charges. • Ultrasonic excitation is introduced to enhance and renew the piezoelectric charges. Conventional electrochemical polymerization is performed on electrodes driven by a direct current power source. It is impossible to realize an electrochemical polymerization reaction on the surfaces of individual nanocrystals in an aqueous system due to the difficulty of connecting all of the nanocrystals to a power source with wires or with the aid of microfabrication, especially in the environment of liquid. In this work, a micro pseudo-electrochemical polymerization reaction was proposed for in situ synthesis of polyaniline (PANI) on the surface of BaTiO₃ nanocubes to form BaTiO₃@PANI core-shell nanocubes. The electric potential of the micro pseudo-electrochemical polymerization originates from the opposite spontaneous polarized charges on the surface of a pair of adjacent BaTiO₃ nanocubes, which form a micro-scale electrochemical cell in reaction solution. Based on the piezotronic effect of the BaTiO₃ nanocubes, ultrasonic excitation was introduced to renew the piezoelectric charges on the surfaces of the BaTiO₃ nanocubes, and enhance the polymerization reaction. The ferroelectric electric potential and piezotronic effect-induced micro pseudo-electrochemical reactions can also be used in other nanomaterials-based electrochemical applications, such as micro-electrochemical water splitting, micro-electrophotocatalysis, and ultrasonic therapy.