Research Of Lead Ions Detection Method Based On Aunps And LC

With the development of industry and agriculture, lead pollution is getting worse. biological degradation is hard for lead ions which are absorbed into the human body through the food chain and threatened human health. However, the available detection methods have a variety of problems, therefore,the new rapid, sensitive, specific, repeatable Pb2+ detect method are needed to meet people’s increasingly high quality requirements on sanitation. Based on this, the researchs have been carried on to explore new Pb2+detection methods from the following three aspects. The specific contents are as follows:(1)A colorimetric method was presented to determine Pb2+ concentration in water based on the different adsorption ability of ssDNA and G-quartet on AuNPs. The guanine-rich ssDNA can be easily adsorbed onto the surface of AuNPs protecting them from aggregation in high ionic strength solution. In the presence of Pb2+, the conformation of ssDNA changed from random coil to rigid G-quartet structure, which can’t bind to AuNPs, lead to the aggregation of AuNPs, accompanied by color changing from red to blue and red shift of the maximum absorption wavelength. Under the optimal conditions, the absorption ratio of A630/A520 was proportional to Pb2+ concentration in the range of 100 nM-10 μM with a detection limit (3a) of 50 nM. The method has adventages of simple, fast, high sensitivity and selectivity.(2) It is the key to design liquid crystal alignment layer for builting a liquid crystal biosensor. The ssDNA have similar long-chain structure with DMOAP, which is a commonly used liquid crystal aligning agent. The amino functionalized ssDNA were modified on the surface of glass substrate with 3-APTES and cross-linking reagents GA. By studying the effect of ionic strength, DNA concentration and the length of DNA chain on the vertical alignment of the liquid crystal to obtain the optimal conditions for preparing DNA orientation film, which provides a new extremely important method to build high sensitivity, high selectivity, high stability of the LC biosensor, and the method was used for the detection of Pb2+, the detection limit can reach 1 nM.(3)DMOAP was used as liquid crystal aligning agent, which inducing homeotropic alignment of the liquid crystal and the G-rich ssDNA was used as recognition molecule to built a LC biosensor.Pb2+could specifically bind with G-rich ssDNA to form Pb2+-G-quadruple structure, which greatly enhanced the interference ability of LC molecules and produced an obvious response in optical textures, thus can achieve the sensitive LC sensing detection of low concentration of Pb2+ with the detection limit of 10 nM. This detection method has the advantages of simple operation, rapid and high sensitivity, therefore, LC biosensor based on the method has good development potential.