In situ synthesis of CuS nanoparticle with a distinguishable SPR peak in NIR region

In this article we report the synthesis of CuS nanoparticle with distinguishable surface plasmonic resonance (SPR) peaks in near infrared region. For this purpose in situ synthesis (one-step fabrication) has been used to prepare CuS nanoparticles in PMMA polymer matrix at room temperature. The X-ray diffraction spectrum confirms the formation of CuS nanoparticles. The transmittance spectra of nano-composite samples reveal that the samples have a good transparency. The absorption spectra show a broad absorption peak in the wavelength region from 570 to 980 nm which is a characteristic SPR peak for CuS nanoparticle. An increase of refractive index was observed for the samples containing CuS nanoparticles. The linear relationship between the refractive index and volume fraction was observed. The appearance of SPR peak in refractive index spectra was attributed to CuS nanoparticles. Shifting of absorption edge to lower photon energy has been observed for nano-composite samples. The direct energy bandgap of nano-composite samples are reduced compare to pure PMMA polymer. The plot between the direct energy band gap and refractive index reveals that the decrease in bandgap energy is associated with the increase in index of refraction. The increase of optical dielectric constant can be ascribed to the formation of CuS nanoparticles. The low band gap of CuS nanoparticles in the present work reveals their importance for applications in optoelectronic devices.