Optical and dielectric features of CMC/PVA/PVP nanocomposite films via hybrid MnW 0.9 Ti 0.1 O 4 and carbon nanoparticle fillers

This study fabricated nanocomposite films based on a ternary polymer blend of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), reinforced with a constant concentration of titanium-doped manganese tungstate (MnW0.9T0.1O4) and varying amounts of carbon nanoparticles (CNPs: 0, 0.2, 0.4, 0.6, 0.8 wt%) via solution casting method. At 1 kHz, the sample containing 0.2 wt% CNPs exhibits a dielectric constant ε′ = 20.44 and a dielectric loss = 0.72, representing the optimal balance between energy storage and dissipation. X-ray diffraction confirmed successful filler integration into the polymer matrix, and scanning electron microscopy revealed sub-micron filler dispersion. The direct optical bandgap increased from 4.71 eV (pristine blend) to 4.99 eV with MnW0.9T0.1O4 addition, then decreased to 4.87–4.93 eV upon CNPs incorporation, demonstrating tunable bandgap engineering. Calculated nonlinear optical parameters (Χ⁽1⁾, Χ⁽3⁾, n₂), obtained from empirical bandgap–refractive index relations, exhibited composition-dependent trends fluorescence exhibited excitation-dependent colour tunability from deep blue to orange-yellow, as validated by CIE coordinates. Although higher CNP loadings (0.4–0.8 wt%) gave larger dielectric constants (28.5–29.0), their loss and conductivity were 2–2.7 times higher, which would reduce breakdown strength and efficiency. Thus, the 0.2 wt% CNPs composite shows promising dielectric properties (moderate ε′, low dielectric loss, low σac) that warrant further investigation for optoelectronic devices and dielectric energy storage applications.