**4. Conclusions**

This study presented a novel method for successfully achieving high ε and low tanδ in three-phase PVDF polymer-matrix nanocomposites. The dielectric properties of a PVDF polymer improved significantly by incorporating conductive Au nanoparticles and semiconductive TNRs with enlarged interfacial areas. The Au nanoparticles were discretely attached to the TNR surfaces to enhance interfacial polarization and simultaneously prevent the formation of conducting pathways in the insulative PVDF matrix. As a result, a high ε (~157) and low tanδ (~0.05) were obtained in the three-phase nanocomposite filled with 1.8 vol% Au and 47.4 vol% TNRs. The dielectric response in the two-phase TNR/PVDF composite increased by more than a factor of two after introducing small amounts of Au nanoparticles. This dielectric behavior is described using the EMPT model. The results indicate that Au nanoparticles significantly contribute to enhancing interfacial polarization and creating a more polar β-PVDF phase, which increases ε . In contrast, due to the small amount of Au nanoparticles used and their discrete growth on the TNRs, the value of tanδ remained low. To further investigate the possible use of the Au-TNR/PVDF nanocomposites in capacitor applications, fabrication conditions that produce nanocomposite thin films need be studied.

**Author Contributions:** Conceptualization, P.K.-o., and P.T.; Formal analysis, P.K.-o. and P.T.; Funding acquisition, P.C.; Investigation, P.K.-o., N.C., J.M., V.H., and N.P.; Methodology, P.K.-o.; Visualization, P.K.-o.; Writing–original draft, P.K.-o. and P.T.; Writing–review & editing, P.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Research and Graduate Studies and the Basic Research Fund of Khon Kaen University, grant number 1500147. This work was funded by the Synchrotron Light Research Institute, Khon Kaen University, and the Thailand Research Fund (TRF), grant number BRG6180003 and the Post–doctoral Program from Research Affairs and Graduate School, Khon Kaen University, grant number 60170. It was partially supported by the Research Network NANOTEC (RNN) program of the National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Higher Education, Science, Research, and Innovation (MHESI), grant number P1851882.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available in article.

**Acknowledgments:** This research was supported by Research and Graduate Studies and the Basic Research Fund of Khon Kaen University (Grant No. 1500147). This work was partially supported by the Synchrotron Light Research Institute, Khon Kaen University, and the Thailand Research Fund (TRF) (Grant No. BRG6180003). This work also received a scholarship under the Post–doctoral Program from Research Affairs and Graduate School, Khon Kaen University (60170). It was partially supported by the Research Network NANOTEC (RNN) program of the National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Higher Education, Science, Research, and Innovation (MHESI) (Grant No. P1851882), and Khon Kaen University, Thailand. P.K. would like to thank the Science Achievement Scholarship of Thailand (SAST).

**Conflicts of Interest:** The authors declare no conflict of interest.
