Research On Synthesis Of Cd-doped ZnO Quantum Dots And Mark Of Bisphenol A Antibodies

Semiconductor quantum dots (QDs), also known as semiconductor nanocrystals, are semiconductor materials with a particle size similar to that of the exciton Bohr radius or the de Broglie wavelength. These QDs have attracted considerable attention from researchers because of their unique optical and electronic properties and have become a bright spot in nanotechnology research. In the present work, different polymer modified QDs have been prepared by the sol-gel method, and the performance of the QDs have been investigated. The synthesised water-soluble QDs could be used as a biological fluorescent probe to determine the levels of a substance in the environment. The main works are as the following:(1) First, the effect of Cd concentration on the structural and luminescent properties of the QDs, as well as the effect of the mass ratio of trioctylphosphine oxide (TOPO)/octadecylamine (ODA), has been investigated. The ZnO and Cd-doped ZnO QDs have hexagonal wurtzite structures and are3-6nm in diameter. When the Cd content was increased, the QD particle size was reduced; this effect was confirmed in the corresponding ultraviolet-visible (UV) spectra. The fluorescence intensity was simultaneously enhanced significantly. Both the UV and fluorescence spectra were blue-shifted. The luminous intensity was further enhanced when the QDs were modified with TOPO/ODA. FTIR and XRD techniques proved that the polymer successfully coated the surfaces of the QDs. A TOPO/ODA mass ratio of1:2was determined to result in the best optical performance among the different ratios examined. The results showed that the described synthetic method is appropriate for the preparation of doped QDs with a high fluorescence quantum efficiency.(2) Cd-doped ZnO QDs were functionalized with poly(amidoamine)(PAMAM) dendrimers, as evidenced by ultraviolet absorption spectrum and fluorescence emission spectra analyses, and this led to their successful transfer into aqueous solution. Ultraviolet absorption spectrum reveals that a small blue shift of water-soluble QDs was observed in contrast to that of the oil-soluble Cd-doped ZnO QDs and the intensity of exciton absorption peak of water-soluble QDs were weaker compare to Cd-doped ZnO QDs. The emission peak of QDs functionalized with PAMAM about350nm was significantly enhanced relative to the emission peak of Cd-doped ZnO QDs, while the emission peak intensity about525nm of QDs functionalized with PAMAM was decreased compare to Cd-doped ZnO QDs in fluorescence emission spectra.(3) A rapid and sensitive cFLISA was developed by utilizing novel QD coupling method and validated for use in aquaeous samples. The biological mass spectrometry prove that the QDs successfully labeled BPA antibodies and this provides strong support for the further application for this type of fluorescent probes in biology. The cFLISA method allowed for BPA determination in a linear working range of20.8-330.3ng/mL with the limit of detection (LOD) of13.1ng/mL. The recoveries of BPA from water samples were from85.92%to109.62%. This water-soluble QDs-based cFLISA method is sensitive, rapid and cost-effective, and therefore has a great potential for biological and medical applications.