| Recently, due to its excellent optical properties and great sensibility, nanosensors have been widely used in many fields such as biology, environmental science, medicine and so on. Nanomaterials are of vital importance to nanosensors in improving their sensitivity, specificity and stability. So, the combination of new nanomaterials including quantum dots(QDs) and gold clusters(Au NCs) with conventional sensors has been exploited in the construction of ideal nanosensors. The new nanosensors could be used for on-site detection of pesticide residues in environmental sample and agricultural food, especially for traditional Chinese medicine. The sensitive monitoring of clinical medicines not only greatly promote the development of nanotechnology, but also provide good perspective for researchers to develop economic and efficient analysis strategies. So far, various analytical methods such as chromatography, electrochemical sensor and enzyme-linked immunosorbent assay have been used for the detection of paraquat, heparin, trypsin and folic acid. However,the mentioned methods have some drawbacks, such as vulnerable interference,difficult extraction, tedious detection steps, time-consuming, poor stability, low detection sensitivity, expensive equipment, or lack of practical value, which limited their point-of-care application. With the increasing of human living condition and the development of science, people realize the importance of the environment security,food security and clinical medication security to their health. Thus, it is urgent to develop a fast, facile and convenient nanosensor with high sensitivity for the detection of those substances, such as pesticide, natural plant/animal source drug and important protein, which are closely related to human health. Moreover, the developed seneors will provide reference for clinical diagnosis and evaluation. Enlightened by the aforementioned facts, a series of fluorescent nanosensors with excellent sensitivity and high selectivity have been developed to detect paraquat in environment,agricultural food and pharmacognosy production and to real-time monitoring natural anticoagulant heparin, folic acid and trypsin. Our major progress has been made:The first chapter, we introduced the synthesis of QDs and AuNCs. Furthermore, we focused on their applications in the analysis of environmentical and agricultural pollutants, protein and bioimaging. Finally, we explored the significance and main content of this dissertation.In the chapter two, in order to meet the requriment of rapid detection and screening of paraquat in environment, agriculture and medicinal plants, we established a convenient method for sensitive detection of paraquat by using quantum dots as a fluorescent probe. In this part, the water-soluble Cd S QDs were synthesized in optimizing conditions within 15 min. Paraquat as a cationic salt could quench the fluorescence of QDs through electron transfer effect. Based on the changes of fluorescence intensity, we could easily detect the paraquat in environmental samples,agricultural food and medicinal plants. The detection linear of paraquat is in the range from 0.025 to 1.5?g m L-1 with a lower detection limit of 0.01?g m L-1. Compared with conventional detection methods, the proposed strategy did not require expensive biological reagents, such as enzymes and antibodies. The method provided a certain technical support and reliable basis for the specific detection of pesticide residues in the environment, agricultural products and Chinese medicinal herbs.In the chapter three, we developed a novel and sensitive nanosensor for the detection of natural anticoagulant heparin and protamine. Bovine serum albumin-capped Cd S QDs could be obviously quenched by gold nanoparticles(Au NPs) via the inner-filter effect(IFE). Protamine could effectively turn on the fluorescence of QDs due to electrostatic attraction between protamine and Au NPs. On the addition of both heparin and protamine, the IFE system formed owing to the stronger interaction between protamine and heparin than that with Au NPs, leading to a marked fluorescence quenching of QDs again. By measuring the fluorescence of QDs, the concentration of protamine and heparin was evaluated. This method could effectively shield the interference of some proteins and amino acids for heparin detection in the blood. The detection line ranged from 10 to 300 ng m L-1, and the minimum detection limit was2.2 ng m L-1. The established method performed a certain guiding significance and reference value for the clinical monitoring and quantitative detection of the content of natural anticoagulant heparin in serum and its clinical application.In the chapter four, to provid the diagnosis basis of the pancreatic diseases, we developed a facile and sensitive Au NCs-based label-free fluorescence assay for real-time monitoring of trypsin activity. The fluorescence of the Au NCs was well quenched because of electron transfer from Au NCs to Cyt C. In the presence of trypsin, Cyt C could be catalyzly hydrolyzed into small peptide fragments. Then, the electron transfer between Au NCs and Cyt C was switched off, leading to the recovery of fluorescence of Au NCs. The procedure had been successfully applied to the detection of trypsin in hunman urine samples with good selectivity and anti-interference ability. The linear range and detection limit was 0.001-0.2 mg m L-1and 0.3 ?g m L-1, respectively. This method would provide a certain technical platform for detection and analysis of the pancreatic protease in clinic amplication.In the chapter five, we describe a sensitive fluorometric and colorimetric dual-readout probe with Au NCs and cysteamine modified gold nanoparticles(cyst-Au NPs) for sensitive detection of folic acid(FA). In this work, the fluorescence intensity of Au NCs showed dramatic decrease in the presence of cyst-Au NPs due to the surface plasmon enhanced energy transfer process. FA could induce the aggregation of cyst-Au NPs. Thus, the surface plasmon enhanced energy transfer between cyst-Au NPs and Au NCs was weakened, resulting in the recovery of fluorescence intensity of Au NCs. This dual-readout probe reported here is successfully applied to the detection of FA, which not only has good selectivity, but also has both absorbance and fluorescence double signal output function. That is, on the one hand, we could semi-quantitative detect the folic acid based on the color changes of the system solution. On the other hand, we could accurately detect FA by fluorescence method.The linear range is 0.11-2.27 ?mol L-1, and the detection limit is 0.065 ?mol L-1.Through the above five chapters, we designed a series of nanosensors for different targets based on the excellent optical properties of QDs and Au NCs. Then, we systematically evaluate their functions and verify the detection effect for the chemicals in real samples, such as water, rice, cabbage, ginkgobiloba, ginkgo, human blood and urine. Those nanosensors provided a feasible scheme and a reliable basis for the rapid and sensitive detection of many chemicals and proteins. Furthermore, it could provide new idea for further study of functionalised nanomaterials. |
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