CuS/SnS quantum dot-nanorod composites: Ferromagnetic and gigantic dielectric characteristics

In this study, new CuS/SnS nanocomposites were simply synthesized by coprecipitation route for capacitive energy storage applications. The results of the XRD analysis confirmed the formation of hexagonal CuS and orthorhombic α-SnS phases. The TEM images of CuS/SnS (1:1) and CuS/SnS (1:3) composites showed the formation of quantum dot particles (2–3 nm) besides nanorods particles (length 56–80 nm and diameter 9–16 nm). The TEM images of CuS/SnS (3:1) sample illustrated the formation of only quantum dot particles (2–3 nm). Infrared band gap energies of 0.8, 0.95 and 1.25 eV were measured for CuS/SnS (1:1), CuS/SnS (3:1) and CuS/SnS (1:3) composites, respectively. CuS/SnS (1:1) composite has a wide hysteresis loop until magnetic field of ±3500 Oe with magnetization (Ms) and coercivity (Hc) values of 0.009 emu/g and 1000 Oe, respectively. For CuS/SnS (1:3) composite, the hysteresis loop possesses a semi-ferromagnetic shape with measured magnetization value of 0.018 emu/g and Hc of 551 Oe. The ferromagnetic order can be attributed to defects as well as the surface interface interaction between CuS and SnS particles. Remarkably, CuS/SnS composites exhibit a giant dielectric constant (>106) with low temperature dependent, making them promising compositions for capacitive energy storage applications. At room temperature, CuS/SnS (1:1), CuS/SnS (3:1) and CuS/SnS (1:3) composites possess colossal dielectric constant values of ∼2.9 × 106, 5.5 × 105 and 6.3 × 106 at frequency of 42 Hz, respectively.