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 (similar to 15 times), and this value is increased further in the presence of Nd-CDs (similar to 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 degrees 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.