Preparation Of Carbon Quantum Dots/Metal Nanohybrids And Their Application In Chemical Sensors

Carbon quantum dots, a new class of zero-dimensional carbon nanomaterials that have recently received a great deal of attention because of their advantageous characteristics, such as remarkable conductivity, excellent water solubility, good chemical properties, simple synthesis and high photostability in the fields of materials,chemistry, physics. Metal nanomaterials exhibit properties that large specific surface area, a lot of active sites, the unique redox reaction activity, selectivity and good biological compatibility and thus have stimulated great interests for their applications.Metal nanoparticles modified electrodes were always high selectivity and high sensitivity. We are committed to develop novel carbon quantum dots/metal composite with excellent performance in terms of combining the advantages of carbon quantum dots and metal materials.In this paper, the novel nitrite and hydrogen peroxide sensor is constructed by using gold, platinum and nickel metal. The following research was carried out :(1) A facile and effective strategy is developed for the fabrication of Carbon quantum dots/Au(Au-CQDs) nanohybrids. The nanohybrids were synthesized throuth a one-pot method under alkaline conditions, without adding any additional surfactant, stabilizing agent and reducing agents. The obtained nanohybrids were characterized by UV-vis spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and so on. Electrochemical measurements demonstrated that the Au-CQDs modified electrode exhibited excellent electrocatalytic activity toward the oxidation of nitrite and decreased its overpotential significantly attributed to the synergistic effect of carbon quantum dots and Au. Then a simple and highly sensitive amperometric sensor for nitrite had been developed. The linear relationships were obtained from 0.1 μmol/L to 2000 μmol/L and the the detection limit was estimated to be 0.06 μmol/L(S/N=3). Furthermore, experimental results indicated that the Au-CQDs modified electrode performed a good reproducibility, nice stability and remarkable selective toward the detection nitrite and showed a satisfactory recovery for the detection of nitrite in real water sample.(2) Based on the previous experiment, the carbon quantum dots/platinum/nickel nanohybrids(NiPt-CQDs) were prepared and their morphology and composition were characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy(EDS). The electrochemical active of NiPt-CQDs modified electrodes was investigated by cyclic voltammetry, the results showed that the modified electrode exhibited excellent electrocatalytic activity toward hydrogen peroxide. The linear relationship between the concentration of hydrogen peroxide and reduction peak current was investigated by cyclic voltammetry and current time curves respectively. For the cyclic voltammetry, in the range from 30 μmol/L to 10000μmol/L with the detection limit of 6.0 μmol/L, and the range from 10 μmol/L to 800μmol/L with the detection limit of 8.397 μmol/L for current-time curves. In addition,the modified electrode displayed remarkable reproducibility and selectivity.