Preparation Of Au And Cu Nanoparticles And Its Applied Research On The Assay And Testing

Metallic nanomaterials are widely used in the detection of nucleic acids, proteins and metal ions. It’s mainly due to its unique structure and has excellent physical and chemical properties. In this paper, we obtained several metal nano-materials and applied them to build colorimetric and fluorescent sensors to sensitive and selective detection of DNA methylation, sulfide (S2-), nitrite ions (NO2-) and biothiols. At the same time, we also studied the formation mechanism of the relevant materials, the main contents are as follows:1. We used the obtained gold nanorods (Au NRs) as the optical sensing probes to detecte DNA methylation and assay the activity of methyltransferase (Dam). Dam and DNA methylation sensitive restriction enzyme endonuclease (Dpn I) were used as the models, a particular sequence comprising 5’-GATC-3’of 15 base double-stranded DNA (dsDNA) was utilized as probe. In the present of Dam and Dpn 1, the dsDNA contained the sequence of 5’-GATC-3’can be methylated, and followed be identified and sheared by Dpn I in the specific sequence. Thus, the dsDNA were cleavaged into single-stranded DNA (ssDNA) fragments, these ssDNA fragments were insufficient to neutralize the positive charges on the surface of Au NRs, the Au NRs remain dispersed state. While, in the present of only Dpn I, Dpn I can not recognize specific sites, DNA is still double-stranded with a large number of negative charges, they can neutralize the positive charges on the surface of Au NRs, and make Au NRs gathered in the situation of lossing protection, thus we can determine whether the dsDNA were methylated according to the color changes of Au NRs, and assay the activity of Dam. The detection limit of Dam with 0.14 U mL-1 was obtained. In addition, the method can be directly used for screening and assessing Dam inhibitors.2. Using AA as the reductant, the blue fluorescent copper nanoclusters (Cu NCs) can be synthesized under the condition of free template, free surfactant and protecting ligands. When adding the buffer of Tris-HCl, we can be observed the transform of the micron tetrahedron nanocrystals to hundred nanometers spherical nanoparticles. When the the reaction time reached 240 min, a large number of fluorescent Cu NCs generated. Thus according to the above experimental facts, the formation mechanism of Cu NCs was proposed with "nucleation-dissolution-clustering". In addition, using UV and FL spectra, we monitored spectral changes in the process of formation in order to further understand the luminescent mechanism of produced Cu NCs.Using the above mentioned Cu NCs as the fluorescent probes, a method of detecting NO2- in manner of simple and rapid was proposed. The resulting detection limit was 3.6 nM, which was less than the most of the currently reported methods. At the same time, this approach can be further applied in the determination of actual water samples. And thus a portable, convenient and sensitive test strips method to assay of NO2 online was developed.3 Application of the green fluorescent Cu NCs which were obtained by using the DA as the reducing agent, we builded S2-fluorescent sensors based on the behavior of the fluorescence quenching of the Cu NCs. Further studies have shown that quenching mechanism lie in the dynamic quenching by S2-.Based on this fluorescence quenching behavior, we obtained S2- linear response range 2.5～200μM, the detection limit can reach 0.75 μM, which is well below the maximum level of S2-in drinking water provision 15μM by the World Health Organization (WHO). Furthermore, the constructed S2- fluorescent sensor is simple and suitable for practical application.4 With SA as the reducing agent, we obtained the blue fluorescent AuCu NCs by the template-free method. When added the biothiols, the fluorescence of AuCu NCs will gradually enhance with increasing the concentration of biothiols, and then the concentrations of biothiols can be detected. Further study of experiments mechanism showed that the fluorescence enhancement phenomenon was caused by the aggregation of AuCu NCs by the biothiols, namely aggregation of induced fluorescence enhancement effect (AIEE).