Study On The Colorimetric Assay Based On Etching Of Gold Nanorods

Because people forcast and prevent insufficiently the negative effects of the highly developed industry for environment, it lead to three global crisis: resource shortage, environment pollution and ecological destruction. Although the three crisis has been a serious threat to people's life, our paper is mainly concerned about the environment pollution problems. Environment pollution refers to natural or man-made destruction, adding so much substance into the environment that it exceeds the environment self-purification capability. In order to control the environment, in the first place, we should understand environmental pollution factors or matter and need the help of analytical chemistry. Therefore, we urgently need a kind of method which can test the present environment situation quickly and conveniently. Because of its unique physical and chemical properties, noble metal nanoparticles(especially gold nanoparticles) have been widely used for environmental and biological detection. Based on the predecessors' efforts, we have proposed three methods for detecting environment ions and biological molecules using noble metal nanoparticles(especially gold nanoparticles).(1) Ultrasensitive visual sensing of molybdate based on enzymatic-like etching of gold nanorods.Based on the catalytic properties of molybdate and iodine-mediated nanorods etching, we have developed a novel approach to visual detection of molybdate with high sensitivity and selectivity. In weak acid solution, molybdate can catalyze the reaction between H2O2 and I– to produce I2, a moderate oxidant, which then etches gold nanorods preferentially along the longitudinal direction in the presence of hexadecyltrimethylammonium bromide. Therefore, the color of solution changed. According to the relationship between this solution color change and molybdenum, we establish a method to detect molybdate.(2) Iodine-mediated etching of gold nanorods for plasmonic sensing of dissolved oxygen and salt iodine.We have carefully investigated iodine-mediated etching of gold nanorods(AuNRs) in the presence of iodate and applied this phenomenon to on-site detection of dissolved oxygen(DO). Under given conditions, the quantitative conversion of target analytes DO to iodine leads to the etching of AuNRs along logitudinal direction with the aid of cetyltrimethylammonium and the color of solution changed. Based on this principle, we established a method to visually detect dissolved oxygen. We also studied the iodine ion catalytic mechanism of potassium iodate etching nanorods. The reach between potassium iodate and iodine ions can produced iodine(the following mechanism is similar to those of dissolved oxygen). According to the two mechanisms, we put forward the dissolved oxygen and salt iodine detection.(3)A highly sensitive colorimetric metalloimmunoassay based on copper-mediated etching of gold nanorodsBased on the copper ion mediated gold nanorods etching, we put forward a highly sensitive visible immune analysis. On the basis of the traditional sandwich method(classic method of enzyme-linked immunoassay), we mainly improved the color process. It reduced the blank of traditional sandwich method and improved the sensitivity. In our method, the detection limit of human IgG reached 0.15 ng/mL(detection limit of traditional sandwich method is only up to 1 ng/mL) and it is more sensitive than traditional ELISA, electrochemical metalloimmunoassay and HRP mimic nanomaterial tags-based immunoassay.