Large piezoelectric strain in sub-10 nanometer two-dimensional polyvinylidene fluoride nanoflakes

Naveed Hussain, Mao-Hua Zhang, Qingyun Zhang, Zhen Zhou, Xingya Xu, Muhammad Murtaza, Ruoyu Zhang, Hehe Wei, Gang Ou, Dong Wang, Ke Wang (Corresponding author), Jing-Feng Li (Corresponding author), Hui Wu (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)

Abstract

Functional polymers such as polyvinylidene fluoride (PVDF) and its copolymers, which exhibit room-temperature piezoelectricity and ferroelectricity in two-dimensional (2D) limit, are promising candidates to substitute hazardous lead-based piezoceramics for flexible nanoelectronic and electromechanical energy-harvesting applications. However, realization of many polymers including PVDF in ultrathin 2D nanostructures with desired crystal phases and tunable properties remains challenging due to ineffective conventional synthesis methods. Consequently, it has remained elusive to obtain optimized piezoelectric performance of PVDF particularly in sub-10 nm regimes. Taking advantage of its high flexibility and easy processing, we fabricate ultrathin PVDF nanoflakes with thicknesses down to 7 nm by using a hot-pressing method. This thermo-mechanical strategy simultaneously induces robust thermodynamic α to electroactive β-phase transformation, with β fraction as high as 92.8% in sub-10 nm flakes. Subsequently, piezoelectric studies performed by using piezoresponse force microscopy reveal an excellent piezoelectric strain of 0.7% in 7 nm film and the highest piezoelectric coefficient (d33) achieved is −68 pm/V for 50 nm-thick nanoflakes, which is 13% higher than the piezoresponse from 50 nm-thick PZT nanofilms. Our results further suggest thickness modulation as an effective strategy to tune the piezoelectric performance of PVDF and affirm its supremacy over conventional piezoceramics especially at nanoscale. This work aims not only to help understand fundamental piezoelectricity of pure PVDF in sub-10 nm regimes but also provides an opportunity to realize other polymer-based 2D nanocrystals.
Original languageEnglish
Pages (from-to)4496-4506
Number of pages11
JournalACS Nano
Volume13
Issue number4
DOIs
Publication statusPublished - 23 Apr 2019
Externally publishedYes

Keywords

  • hot-pressing
  • piezoelectricity
  • polyvinylidene fluoride
  • sub-10 nm nanoflakes
  • two-dimensional nanomaterials

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