| Antibiotics have made great contribution to improve the ability to resist disease for human. As they have been widely used in agriculture and animal husbandry, antibiotics are inevitably existing in animal food and agricultural products as a kinds of residual poison. Through the food chain, human will be passive uptake of these antibiotics for a long time, it will seriously affect people’s physical health, especially for infants and young children. Therefore, the analysis of antibiotic residues in food has important social significance.Semiconductor nanocrystals Cd Te has excellent performances as the unique optical properties of nano materials, such as strong fluorescence, light stability, water soluble and so on, which make it widely research and applications in the fileds of biological and chemical, etc. In this paper, visible and near-infrared Cd Te quantum dots were synthesised using carbohydrazide as reducing agent and new procedure. Furthermore, these quantum dots were used as fluorescent probes for the detection of moroxydine, penicillin, streptomycin and 6-mercaptopurine. The main contents are summarised as follows:(1) Synthesis of Cd Te quantum dots with carbohydrazide as reducing agentA novel, simple and economical method was established for synthesis of Cd Te quantum dots(QDs) in an aqueous medium using carbohydrazide as reduction, thioglycolic acid(TGA) as the ligand, cadmium chloride as a source of cadmium and tellurium dioxide as a source of tellurium.The prepared Cd Te quantum dots with stable performance and uniform particle size distribution. The influence of experimental conditions, including acidity, reaction tempreture, reaction time and the amount of ammonia were systematically investigated, and optimum conditions were determined. Carbon hydrazine was used as an environmental friendly reducing agent in this method has proposed for the preparation of Cd Te quantum dots. Finally, the difficult problems, such as using high activity and high toxicity as reducing agent which results difficult to control and environmental pollutionin, were overcome in the traditional process to prepare Cd Te quantum dots.(2)The synthesis of Near-infrared Cd Te quantum dotsA one-step method was developed for the synthesis of near-infrared Cd Te quantum dots with sodium sulfite as reduction by programmed temperature hydrothermal methods. The influence of experimental conditions, including acidity,reaction tempreture, reaction time and the amount of sodium sulfite were systematically investigated, and the optimum conditions were determined. Under the opyimum conditions, a green method for synthesis of near-infrared Cd Te quantum dots was establised. Furthermore, this method can solve the problems which the fluorescence emission of CDTe quantum dots prepared by the conventional refluxing methods is usually hard to reach more than 700 nm, at the same time, it needs to prepare step by step.(3)Determination of moroxydine residue in tomatoes using Cd Te quantum dots as fluorescence probesA novel method for the detection of moroxydine(ABOB) residue in tomatoes was developed based on the enhancement of the fluorescence intensity of Cd Te quantum dots(QDs) in the presence of ABOB. The factors influencing the performance of the QDs fluorescent probes were investigated and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity increases linearly proportional to the ABOB concentration over the range of 1.0×10-12~5.0×10-10 mol/L with a limit of detection of 5.2×10-13 mol/L,R=0.9944, the recovery was 97%~106%. This is a fast, simple, high selective and sensitive method. The proposed method has been successfully applied in the detection of trace moroxydine hydrochloride residue in tomatoes.(4)Determination of penicillin residues in milk by using Cd Te quantum dots as fluorescent probeHerein, a new sensitive and selective method has established for determination for trace penicillin in milk by using thioglycolic acid-capped Cd Te quantum dots. This method based on the recovered fluorescence of the Cd Te quantum dots(QDs)-Hg(II) system is reported. The factors influencing the performance of the QDs fluorescent probes were investigated and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity increases linearly proportional to the penicillin concentration over the range of 1.0×10-7~1.0×10-3 mol/L with a limit of detection of 2.5×10-8 mol/L,R=0.9982, the recovery was 96% ~105%. This is a fast,simple, high selective and sensitive method. The proposed method has been successfully applied in the detection of trace penicillin residue in milk.(5)Determination of streptomycin residue in cucumbers by using Cd Te quantum dots as fluorescence probesA novel method for the detection of streptomycin(SM) residue in cucumbers was developed based on the enhancement of the fluorescence intensity of Cd Te quantum dots(QDs) in the presence of SM. The factors that influence the detection of SM have been investigated, and the optimum conditions were determined. Under the optimum conditions, a linear correlation is found between the concentration of streptomycin and relative fluorescence intensity of the system in the range of 5.0×10-12~1.0×10-10 mol/L with linear correlation coefficient(r)of 0.9990. The proposed method has been successfully applied in the detection of trace streptomycin residue in cucumbers.(6)Determination of trace 6-mercaptopurine using near-infrared Cd Te Quantum dots as fluorescence probesBased on the recovered fluorescence of the Cd Te quantum dots(QDs)-Cu(II) system, a new sensitive and selective method was established for determination for trace 6-mercaptopurine by using near-infrared Cd Te quantum dots as fluorescence probes is reported. The factors influencing the performance of the QDs fluorescent probes were investigated and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity increases linearly proportional to the 6-Mercaptopurine concentration over the range of 1.0×10-12~1.0×10-10 mol/L with a limit of detection of 6.0×10-13 mol/L,R=0.9947.The coexistence of the common substances show no significant interference on the determination results.The method used for the determination of 6-MP residue in the low alcohol wine with good results. |
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