Preparation and Effect of Lighting on Structures and Properties of GSH Capped ZnSe QDs

Preparation of high-quality graphene oxide-carbon quantum dots composites and their application for electrochemical sensing of uric acid and ascorbic acid

Graphene oxide-quantum dots systems are emerging as a new class of materials that hold promise for biochemical sensing applications. In this paper, the eco-friendly carbon quantum dots (CQDs) are prepared with cheap and recyclable coke powders as carbon source. The graphene oxide-carbon quantum dots (GO-CQDs) composites are synthesized using graphene oxide as the conductive skeleton to load the CQDs by a one-step calcination method. The obtained GO-CQDs composites demonstrate the successful decoration of CQDs on GO nanosheets. The CQDs acting as spacers create gaps between GO sheets, resulting in a high surface area, which electively increases the electrolyte accessibility and electronic transmission. The electrocatalytic activity and reversibility of GO-CQDs composites can be effectively enhanced by tuning the mass ratio of GO to CQDs and the heating process. Furthermore, a highly sensitive and selective electrochemical sensor for determining uric acid (UA) and ascorbic acid (AA) was developed by modifying GO-CQDs composites onto a glassy carbon electrode. The results show that the linear range, minimum detection limit, and sensitivity of the GO-CQDs electrode for UA detection are 1-150 μM, 0.01 μM, and 2319.4 μA mM^-1 cm^-2, respectively, and those for AA detection are 800-9000 μM, 31.57 μM, and 53.1 μA mM^-1 cm^-2, respectively. The GO-CQDs are employed as the electrode materials for the serum and urine samples electrochemical sensing, the results indicate that the sensor can be used for the analysis of real biological samples.

Novel synthesis of Mn: ZnSe@ZnS core-shell quantum dots based on photoinduced fluorescence enhancement

A novel Type-I Mn: ZnSe@ZnS core-shell quantum dots (QDs) was reported through a two-step procedure by using low-cost inorganic salts and naturalbiomacromolecule as raw materials. Based on a designed structure of L-cysteine-capped Mn: ZnSe QDs in aqueous media with the controllable surface, Mn: ZnSe@ZnS core-shell QDs were formed due to photoactive ions and defect curing under continuous constant light. The influences of experimental variables, including synthesis conditions of Mn: ZnSe QDs, different types and affecting factors of photo irradiation had been systematically investigated. Under the effect of photoinduced fluorescence enhancement, the photoluminescence (PL) intensity increases significantly by about 5-10 times after 1-3 h of UV irradiation. The position of the fluorescence peak was red-shifted by about 17 nm, emitting orange-red fluorescence. The photoluminescence quantum yield (PL QY) was markedly improved (up to 35%). The structure and morphology of Mn: ZnSe@ZnS core-shell QDs were also confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) in detail. The mechanism of photoinduced fluorescence enhancement was attributed to L-cysteine allowed to release S^2- to form a ZnS shell, and the passivated surface non-radiative relaxation centers of Mn: ZnSe@ZnS QDs was successfully synthesized with highuniform size, excellent photoluminescence performance, and good stability, all ofwhichmakethemgood potential candidates for white LEDs, and biological labels.