| Nanomaterial, a kind of novel material, was developed in the20st century. It has unique photoelectric properties and excellent biocompatibility. Based on the above features, nanomaterials have been widely used in its electrical, optical, catalytic, biochemistry, cell imaging and medical fields. The thesis has designed a series of high sensitivity, good selectivity, low cost of biological fluorescent sensors for the detection of biological molecules and heavy metal based on the excellent optical properties of gold nanoparticles and silicon quantum dots. The main contents are as follows:(1) Here we report a novel label-free fluorescent sensor for ultrasensitive detection of protamine and heparin based on the high quenching ability of gold nanoparticles to the fluorescence of fluorescein. The fluorescence was significantly quenched when fluorescein molecules were attached to the surface of gold nanoparticles by electrostatic interaction. Upon addition of protamine, the fluorescein molecules were detached from the surface of the gold nanoparticles due to the stronger adsorption of protamine on the surface of AuNPs, and resulting in the recovery of the fluorescein molecules fluorescence. Heparin is able to bind with protamine specifically. In the presence of heparin, the interaction of heparin with protamine makes the AuNPs de-aggregate and the fluorescein molecules re-attach to the AuNPs, which lead to marked fluorescence quench again. By measuring the changes in the fluorescence of the fluorescein molecules, the concentration of protamine and heparin were sequentially determined. Under optimal conditions, the detection limit for protamine and heparin is6.7ng/mL and1.3ng/mL (S/N=3), respectively.(2) A switch mode fluorescent sensor based on AuNPs and a new probe to detect melamine was designed and prepared in this study. This new fluorescent sensor has good optical stability and high fluorescence intensity. Compared the traditional fluorophore, such as fluorescein, it is less dependence on the value of pH. And it has a very strong fluorescence emission peak at550nm, which has larger overlap with the ultraviolet absorption peak of AuNPs. When the probe was incubated with the AuNPs, the fluorescence intensity of the probe can be effectively quenched by AuNPs. Adding melamine into probe-AuNPs mixture caused aggregation and color change due to the electrostatic interaction between melamine and AuNPs. And ultraviolet absorption peak position of AuNPs was changed, thus the overlapping peak area between probe and AuNPs was reduced, the fluorescence intensty of probe was restored. By measuring the changes of fluorescence intensity of the probe, the detection of melamine was realized. Under optimized conditions, the linear response to melamine in the range of0.2-4μmol/L and lower detection limit down to3.3nmol/L (S/N=3) with the sensor. And this method can realize the milk powder and other real samples of melamine detection.(3) In this work, label-free silicon quantum dots (SiQDs) were used as a novel fluorescence probe for the sensitive and selective detection of Cu2+. The fluorescence of the SiQDs was effectively quenched by H2O2from the reaction of ascorbic acid with O2, and hydroxyl radicals from Fenton reaction between H2O2and Cu+. In the testing system, the recycling of Cu2+may dramatically amplify the quench processes of SiQDs fluorescence. After optimize the experimental conditions, the fluorescence intensity of SiQDs was linearly dependent on the Cu2+concentration ranging from25to600nM with the limit of detection as low as8nM (S/N=3). Moreover, the probe was successfully applied to the determination of Cu2+in real sample. |
PDF Full Text Request