Role of precursors in controlling the size, shape and morphology in the synthesis of copper sulfide nanoparticles and their application for fluorescence detection

Synthesis of well controlled pure phase of CuS with defined shapes and sizes remains a challenge for effective applications. We studied the role of copper and sulfur source precursors in controlling the size, shape and morphology of CuS nanostructures using synthesized refluxing method. CuS nanoparticles are synthesized by varying Cu(CH3COO)2·H2O, Cu(NO3)2·3H2O, CuSO4·5H2O as copper precursors and CH4N2S, Na2S2O3·5H2O, Na2S as sulfur precursors. As synthesized copper sulfide nanoparticles were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray (EDX), Ultra Violet - visible spectrophotometer (UV–Vis), Fourier transform infrared spectroscopy (FT-IR), and micro Raman spectroscopy. All precursors result into nano-size single phase covellite copper sulfide, except sodium sulfide as a sulfur source which resulted into mixed phases. Morphology of nano-systems varies (hexagonal plate like, tube like, cluster of nanoparticles, plate like and ball like nanostructures) with varying precursors. TEM images show particle size variation (particle size 20–25 nm). Elemental analysis using EDX confirm that stoichiometric ratio of Cu/S is approximately 1:1 which is in good agreement with the starting molar ratio. FT-IR and Raman spectra confirm the absence of Cu2S and the band width of S-S stretch mode is correlated with particle size. Optical energy band gap varies in the range 1.80–2.31 eV and is also correlated with crystalline size. The release rate of S2− ions in sulfur source and polarization of counter anion in copper source are found to be the deciding factors in controlling the size, shape and morphology.