The electroactive β-phase formation in Poly(vinylidene fluoride) by gold nanoparticles doping

doi:10.1016/j.matlet.2011.11.117

Materials Letters

Volume 73, 15 April 2012, Pages 123-125

https://doi.org/10.1016/j.matlet.2011.11.117 Get rights and content

Abstract

In this work we report on the preparation and characterization of a Poly(vinylidene fluoride) (PVDF) film doped with gold nano-particles (Au-NPs) prepared by a one step procedure. The preparation of Au-NPs without any external reduction agent is in the focus of interest when PVDF is used as a polymer stabilizer. It is found that a desirable amount of Au-NPs within the polymer matrix can enhance the electroactive β-phase in PVDF. The melting behavior of the crystalline polymorph of PVDF is examined by in-situ thermal FT-IR study. Spherulitic features in Au-NPs doped PVDF film are observed in the topographic images indicating a probable existence of spherulitic structures also in the β-phase (β-spherulite).

Graphical abstract

The electroactive β-phase is induced in PVDF by doping with Au-NPs. The synthesis of Au-NPs and its doping was performed in a single step procedure. For the first time, we are reporting with experimental evidences that β-phase also has spherulitic features (β-spherulite).

Introduction

Poly(vinylidene fluoride) (PVDF) is widely used in a variety of electro-optical, electromechanical, and biomedical applications. It exhibits at least four crystalline phases (α-, β-, γ-, and δ-phase). Among them the α-phase is non-polar, whereas the others are electroactive [1]. However, only the β-phase (all-trans (TTTT) conformation) has a stronger ferro-, piezo-, and pyroelectric response due to its largest spontaneous polarization (7 × 10^− 30 Cm per unit cell) [2]. Therefore several efforts have been taken in order to induce the β-phase into PVDF, e.g. mechanical stretching, the application of high pressure or the poling under high pressure [2]. Nevertheless, these methods normally induce undesired structural deformations or structural limitations which may not be feasible for several applications, in particular for electro-optical sensors and non volatile memories [3], [4]. Hence, an alternative methodology is required. In this work, we have induced the β-phase into PVDF by doping it with gold nano-particles (Au-NPs) via a single step procedure.

Section snippets

Experimental procedure

In our preparation procedure we have chosen N,N-Dimethylformamide (DMF) for two reasons i) as the best known solvent for PVDF and ii) as a reduction agent for Au-NPs [5] in order to avoid unnecessary additives when Au-NPs is reduced from chloroauric acid (HAuCl₄·3H₂O). First, 0.2 and 1.5 mM of HAuCl₄·3H₂O (Sigma-Aldrich, Germany) were separately added to 6 wt.% (w/v) PVDF-DMF (Sigma-Aldrich, Germany) solutions which were afterwards vigorously stirred at 60 °C for 4 h. Then the solutions were cast

Results and discussion

The FE-SEM image of Au-NPs doped PVDF film is illustrated in Fig. 1. It reveals that Au-NPs are distributed in different shapes (spherical, triangular, octahedron, square and rod type) and sizes. A photograph of the film is shown in the inset (a) of Fig. 1. The apparently transparent pink color of the film ensures the Au-NPs formation and its doping into the PVDF matrix. From UV–vis spectra (inset (b) of Fig. 1) the characteristic plasmon bands of Au-NPs at 550 nm is evident [5], [6]. The little

Conclusion

In summary, the synthesis of Au-NPs is performed by a facile technique where PVDF acts as stabilizer. The desirable amount of Au-NPs doping in PVDF can induce the electroactive β-phase, which is in the main focus of attraction because of its polar nature. Therefore, the traditional stretching method can be avoided. The spherulitic structure of the β-phase is observed in the Au-NPs doped PVDF film emphasizing a new feature of PVDF.

Acknowledgment

This work was partially supported by funding from the Jadavpur University (Ref. No. P-1/1169/08) and German Research Foundation (DFG) within the priority program SPP 1157 (grant No. Schm 745/11-1-2).

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The electroactive β-phase formation in Poly(vinylidene fluoride) by gold nanoparticles doping

Abstract

Graphical abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusion

Acknowledgment

Polymer

Science

Phase Transitions

IEEE Sens J

J Vac Sci Technol B

Langmuir