Studies On Synthesis And Sensing Properties Of Fluorescent Metal Nanoclusters

In recent years, the fluorescence labeling technique has been involved in all aspects of human research, such as the bio-medical field, etc. The luminescent labeled materials include organic dyes, semiconductor quantum dots, fluorescent nanoparticle composite and precious metal nanoclusters; the latter three fluorescent materials are well collectively used as novel fluorescent labeling of nano materials, owing to their nanometer particle size. They have recently received considerable attention of the majority researchers because of their excellent photochemical, and become a new generation of fluorescence labeled material. Metal nanoclusters are defined by a new class of fluorescent nanomaterial which contain from a few to roughly several tens of atoms of a metal such as Au, Ag or Cu. Their particle size is generally less than 2nm, and they have outstanding spectral and photophysical properties and have received widespread concern by scientists.Among them, up to date, the synthetic noble metal nanoclusters using deoxyribonucleic acid (DNA) as a basic skeleton have been widely used in fluorescence imaging, biological chemical sensing, nano devices, antibacterial agent, environmental monitoring and many other fields. In this article, we use different DNA as templates to synthesize silver nanoclusters, and realize the methods of selective recognition of DNA sequences. In addition, we also use fluorescent sliver nanoclusters to detect mercury ion, and preliminary research the fluorescent copper nanoparticles. The main research contents and experimental conclusions are summarized as follows:1. The sequences of (CNG)n were employed as capping scaffolds to synthesize fluorescent silver nanoclusters using NaBH4 as reductant, which is a fast, valid, conventional method of synthesis of fluorescent silver nanoclusters. We studied the properties of this style of fluorescent Ag NCs by some characterization methods, such as fluorescence spectroscopy, UV-visible absorption spectroscopy, and further improved the selectivity and sensitivity of the synthesis of fluorescent silver nanoclusters which used DNA as templates by using organic molecular crowding conditions. It provided a new possibility for the detection of (CGG)-sequence. The experimental results show that:the selection dependency of fluorescence emission of the silver nanoclusters which used (CNG) sequence as templates on the DNA sequence is according to the order of G> C> T≈A, and this selective order also applies on different lengths of (CNG)n. In addition, this method has the advantage that using organic molecule can improve the sensitivity of Ag NCs selective recognition of (CGG), and further illustrates that the experimental method is efficient, convenient and rationality.2. We mainly employed three-way DNAs as templates and used NaBH4 as reducing agent to synthesize fluorescent silver nanoclusters, and optimized the synthesis conditions such as the molar ratios of the reactants and the reaction time. We studied the properties of this style of fluorescent Ag NCs by some characterization methods, such as fluorescence spectroscopy, and simply introduced the DNA/Ag NCs application in the detection of mercury ion. The results of experiment demonstate that:silver nanoclusters can be more effectively produced when the branch points are cytosine bases in the DNA three-way junctions, which further illustrates that the synthesis of silver nanoclusters strongly depends on the DNA sequence; what’s more, the synthesized nanoclusters can also be used as fluorescent porbes for Hg2+ion detection.3. Some homopolymers-single-stranded DNAs composed of multiple, same bases, were used as templates and sodium ascorbate was used as the reducing agent to synthesize luminescent copper nanoparticles. We use fluorescent steady-state method to study the effect of DNA base on selectivity and stability of the growth of fluorescent copper nanoparticles. The results of experiment demonstate that:the fluorescent copper nanoparticles can be effectively synthesized using a plurality of thymine bases as templates, and the fluorescent intensity increases depending on the increasing length of the bases.