The Construction And Application Of Chemical Sensors Based On Silicon/Graphene Quantum Dot

A chemical sensor is an electrical signal component that responds specifically to a chemically active substance and converts the relevant information into detectable and recordable.The unique optoelectronic properties of nanomaterials make it a boom in the field of sensors.The quantum dots,as one of nanomaterials,is becoming more and more mature on sensors.In this paper,a sensor for detecting human blood glucose and urine iodine content is constructed based on silicon/graphene quantum dots.including the following three parts.Part Ⅰ: The amino functionalized silicon quantum dots(NH2@Si QDs)with an average particle size of 2 nm were prepared by simple microemulsion method.Their structures and properties were characterized by transmission electron microscopy,infrared,ultraviolet visible and fluorescence spectroscopy,which proved that NH2@Si QDs has good water solubility,high fluorescence quantum yield and optical stability.Based on the fluorescence quenching response of glucose to NH2@Si QD,a non-enzymatic glucose sensor was developed.The quenching mechanism is attributed to the fact that glucose molecules connect NH2@Si QDs together through hydrogen bonding and hydrophobic interaction to cause self-aggregation of quantum dots,which lead to fluorescence quenching.The glucose was detected after optimization of reaction temperature,time and p H.The fluorescence intensity was linear with glucose in the range of 1.0×10-6 ~ 9.0×10-5 mol/L,and the detection limit was 3.0×10-7 mol/L.The sensor not only has good selectivity,but also is successfully applied to blood glucose analysis of human serum,and the recovery rate is between 92.5 % and 98.7 %.Part Ⅱ: Graphene quantum dots(GQDs)with an average particle size of 2.25 nm were prepared by citric acid carbonization.The structure and properties were characterized by transmission electron microscopy,infrared,ultraviolet-visible and fluorescence spectroscopy.After the addition of Hg(II)ions to the quantum dots,significant fluorescence quenching of GQDs occurs due to the photoinduced electron transfer mechanism,and the strong interaction between Hg(II)and iodide after I-addition leads to Hg(II)ions released from the complex,allowing fluorescence GQDs to be recovered and the iodide to be determined in the range of 1.0 × 10-5 to 9.9 × 10-5 mol/L.The detection limit is 3×10-7 mol/L.GQDs/Hg2+ has excellent selectivity for some common anions and has been successfully used for the determination of iodide in human urine.The recovery rate is between 96 and 102 %.Part Ⅲ: Selecting polyethyleneimine(PEI)functionalized graphene quantum dots to obtain aminated graphene quantum dots(GQDs@PEI),which are combined with palladium chloride and reduced by sodium borohydride to obtain aminated graphene Quantum dot palladium nanocomposites(GQDs@PEI/Pd).It was characterized by transmission electron microscopy,energy spectrum analysis,cyclic voltammetry and current-time method,and it was first proved that the nanomaterial had obvious electrochemical response to glucose.Based on the composite material,an enzyme-free glucose electrochemical sensor was constructed.The glucose concentration in the range of 1-220 μM showed a good linear relationship with the current signal.The linear equation consisted of high and low concentrations.The lowest detection line was 0.30 μM.Its sensitivity is up to 1405.2 μA·m M-1·cm-2.The sensor has the advantages of high selectivity,sensitivity and long-term stability,and can provide a new method for detecting human serum glucose.