Efficient and tight self-assembly from CNF@ZnO synthesized via an one-step hydrothermal method to fabricate cellulose based piezoelectric composite

Cellulose nanofibril (CNF) with various oxidation degree, had been applied to manufacture high-performance piezoelectric composite for generator and sensor via a two-step hydrothermal method. To elevate the preparation efficiency, CNF was utilized as substrate for in-situ polymerization of ZnO to prepare a flexible piezoelectric composite by an improved one-step and one-pot hydrothermal method in this work. The effect of oxidation degree, Zn 2+ concentration and reaction time on the structure and performance of the composite were discussed in depth. The CNF-assisted one-step hydrothermal can be used to achieve directed nucleation of ZnO along the c-axis for strong anchoring effect of the abundant carboxyl and hydroxyl groups. Notably, with the moderate increase in the degree of oxidation, the ZnO's structure, dispersity are enhanced, improving composite film performance. Therefore, the ZnO in the 10CNF@4ZnO-6 composite film has a crystallinity of 89.64 % and favorable (002) facet ratio of I(002)/I(101) (0.91). The obtained composite film exhibits well tensile strength of 16.12 ± 2.35 MPa and elongation at break of 16.21 ± 2.17 % for the tight self-assembly by CNF@ZnO with the regulatorily reserved oxygen-containing groups. Surprisingly, the measured longitudinal piezoelectric coefficient reaches as high as 17.6 ± 1.7 pC·N −1 , along with the generated V OC and I SC of 5.61 V and 277.55 nA (50 N, 2 Hz), respectively. The optimized piezoelectric devices can sensitively detect weak vibration from knocking pipe and glass window. This ingenious strategy will provide actual reference for the optimization fabrication of cellulose and ZnO based functional composite. • The controlled growth of ZnO on the CNF was realized by one-step hydrothermal. • The controlled morphology and structure of ZnO was obtained via in-situ synthesis. • CNF@ZnO can be self-assembled into composite film by simple filtration. • The self-assembled CNF@ZnO composite film displays the tensile strength of 17.45 ± 2.34 MPa. • CNF@ZnO nanogenerator can generate a voltage of 5.61 V along with the d₃₃ of 17.6 ± 1.7 pC·N −1 .