Synthesis and multifunctional applications of quantum nanobeads for label-free and selective metal chemosensing

Due to the importance of quantum dots (QDs), fervent research continues for new preparations, surface modification and investigation of further applications. The facile preparation of CdS QDs embedded in chitosan nanoparticles (CTS) was synthesized, characterized and has been applied for various applications such as hydrogen peroxide (H2O2) and selective detection of metals such as Cu(II) and Mn(II). CdS@ CTS was characterized by TEM, SEM, UV-vis absorption, fluorescence, Fourier transform infrared (FTIR), and Raman spectroscopy. It was found that hydrogen peroxide (H2O2) could directly oxidize CdS QDs and quench the fluorescence emission. The method is non-enzymatic, simple, direct, and sensitive. CdS@ CTS was also applied for metal ion chemosensing such as Mn(II) and Cu(II). Among the different metal, CdS@ CTS showed selectivity toward Cu(II) with a limit of detection of 50 nM and linear range of 30-330 mu M. The detection could take place by the naked eye. Mechanistic studies were refuted using TEM and Raman spectroscopy.