Design and electrospinning synthesis of red luminescent-highly anisotropic conductive Janus nanobelt hydrogel array films†

Abstract

The preparation of anisotropic conducting hydrogels with high anisotropic conductivity using simple methods is a major challenge. Herein we present a new strategy for significantly enhancing the degree of anisotropic conductivity of hydrogel materials. Highly oriented Janus nanobelts are used as the building block to avoid undesirable interactions between conducting and insulating materials, resulting in highly conductive hydrogel materials. As a case study, in this paper, anisotropic conductive-luminescent bifunctional Janus nanobelt hydrogel array films (denoted as JAHFs) are prepared by parallel electrospinning and gelation, utilizing highly oriented Janus nanobelts, i.e. [Eu(TTA)₃(TPPO)₂/gelatin (GE)]//[carbon black (CB)/GE] Janus nanobelts, as building blocks. The high degree of integration between the highly oriented array film and the anisotropic conductive-luminescent materials endows the hydrogel material with high anisotropic conductivity and multifunctionality. The anisotropic conductivity of JAHFs is as high as 1.52 × 10⁵ when the mass ratio of CB/GE is 7%, which achieves a significant increase in anisotropic conductivity through a simple preparation method. JAHFs have a distinct red luminescence at 616 nm. The tunability of luminescence and conductive anisotropy is demonstrated by adjusting the contents of Eu(TTA)₃(TPPO)₂ and CB. The tensile strength and the elongation at break of JAHFs along the parallel direction of Janus nanobelts are 0.61 MPa and 80.75%. The good mechanical properties of JAHFs provide a guarantee for the assembly of strain sensors. JAHFs exhibited rapid responses under various tensile strains and temperatures, and the assembled strain sensors are utilized to detect human joint motion with good stability and sensitivity. This method is also applicable to the preparation of other multifunctional anisotropic conducting hydrogel materials. This study contributes new approaches and technical support for enhancing the anisotropic conductivity of hydrogel materials and sets the groundwork for developing other multifunctional conductive hydrogel materials.