Carbon-Dot-Containing Poly(methyl methacrylate) for Highly Dielectric Nanomaterials

In this paper, we report a massive enhancement of the relative permittivity of PMMA-based nanodielectrics in the presence of carbon dots (CDs) and neodymium-doped carbon dots (Nd-CDs). Different weight percentages (0.5, 5, and 10 wt %) of CDs and Nd-CDs were composited with PMMA to form PMMA@CD and PMMA@Nd-CD nanocomposite films, and films were characterized by different techniques. The dielectric response study indicates the significant enhancement of the relative permittivity of PMMA in the presence of CDs (∼15 times), and this value is increased further in the presence of Nd-CDs (∼153 times). The presence of many interfaces inside the PMMA@CD composites due to nanofillers is the cause of this significant enhancement in dielectric permittivity, which is further increased in the presence of Nd-CDs. As the temperature increases, the effective dipolar polarization of the composites increases, which in turn helps enhance relative permittivity. Nevertheless, at 75 °C and 100 Hz, the relative permittivity value for PMMA@Nd-CD composites reaches nearly 1242 (234 times), the highest reported for PMMA composites to date. Moreover, the AC conductivity for PMMA@Nd-CD is higher than that for PMMA@CD, possibly as a result of more charge conduction from the valence band to the conduction band for PMMA@Nd-CD. The conductivity is also increased as a function of temperatures for all composites as a result of the decrement of electronic resistance inside semiconductor nanofillers. In this study, a unique and sensitive change in dielectric and electrical properties of PMMA-based nanodielectrics was observed, which is helpful in the commercial use of PMMA nanodielectrics inside capacitors.