Selective Naked-eyes Chemosensing of Cu2+ ions using Chitosan-CdS Quantum Dots Biohybrid

Cadmium sulfide (CdS) quantum dots (QDs) were homogeneously embedded into chitosan (CTS), denoted as CdS/CTS, via an in-situ solvothermal method. The intact structure of the synthesized materials was preserved via separating the materials using freeze-drying. The materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), high-resolution TEM (HR-TEM), scanning TEM (STEM), dispersive energy X-ray (EDX) for elemental analysis and mapping, Fourier transform infrared (FT-IR), nitrogen adsorp-tion-desorption isotherms, thermogravimetric analysis, UV-Vis spectroscopy, and diffuse reflectance spectroscopy (DRS). The synthesis procedure offered CdS QDs with 1-7 nm (average particle size of 3.2 nm). The functional groups of CTS modulate the in-situ growth of CdS QDs and prevent the agglomeration of CdS QDs, offering homogenous distribution inside CTS. CdS/CTS QDs can also be used for naked-eye detection of heavy metals with high selectivity toward copper (Cu2+) ions. The mechanism of interactions between Cu2+ ions and CdS/CTS QDs was further studied