Synthesis Of Silver Nanoclusters And Copper Nanoclusters And Their Applications In Biochemical Analysis

Metal nanoclusters (MNCs), consisting of a few to tens of metal atoms, have received considerable attention due to their unique physical, electrical, and optical properties. Among the reported noble metal clusters, oligonucleotide-templated silver nanoclusters (DNA-AgNCs) are of tremendous interest due to their low toxicity, facile synthesis, tunable emission spectrum, high quantum yield and good photostability. Compared with gold nanoclusters (AuNCs) and silver nanoclusters (AgNCs), copper nanoclusters (CuNCs) also have similar photochemical properties. Moreover, copper is extremely cheap and highly conductive. CuNCs, as potential materials, can be used in various industries such as catalysis and sensing. In this thesis, the synthesis of the DNA-AgNCs and CuNCs, and the applications of them in the fields of biochemical analysis were investigated as follows,1. A new approach for respiratory syncytial virus (RSV) gene sequence detection was described based on the fluorescence resonance energy transfer (FRET) from DNA-AgNCs to multi-walled carbon nanotubes (MWCNTs). The specific DNA scaffold combines two fragments, one is rich in cytosine sequence fragment (C12) that can result in DNA-AgNCs with high quantum yield via a chemical reduction method, and the other is the probe fragment (5’-AAA AAT GGG GCA AAT A-3’) which can selectively bind to the gene for RSV. Thus, the as-prepared AgNCs can exhibit enhanced fluorescence when binding to the target DNA sequence and forming a double helix. Because of the introduction of MWCNTs, which can quench the fluorescence of DNA-AgNCs with extraordinarily high quenching efficiency (85.8%), a relatively high signal-to-background ratio was achieved. Therefore, by combining DNA-AgNCs with MWCNTS we can achieve label-free analysis of gene sequences of RSV with a high selectivity. The fluorescence ratio of DNA-AgNCs was linearly proportional enhanced to the concentration of the target in the range of31.25nM to2.00μM with the detection limit (3σ) of24.00nM.2. A one-step synthesis of water soluble and pH-responsive trypsin-stabilized fluorescent CuNCs was developed without using additional protective or reducing agents. This method was extremely simple. To be specific, by refluxing the mixed solution of trypsin and CuCl2for12h, the trypsin stabilized CuNCs were obtained. Additionally, the as-prepared CuNCs exhibited highly stable properties including oxidation resistance, thermal stability and photostability. In acidic media, the fluorescence intensity of CuNCs was enhanced because of the better dispersibility. On the contrary, in alkaline media, the fluorescence intensity of CuNCs was quenched owing to the aggregation of CuNCs. Thus,. For this reason, the as-prepared CuNCs could served as reversible pH indicators. Moreover, the fluorescence intensity of CuNCs exhibited a linear fashion over the pH range of2.02-12.14. The linear equation is F=-197.0pH+2741.1and the corresponding correlation coefficient is0.994.3. A novel and selective method for the detection of pyrophosphate (PPi) in aqueous solution has been developed based on the fluorescence enhancement of trypsin stabilized CuNCs. It was confirmed that the introduction of PPi into CuNCs solution resulted in the dispersion of CuNCs leading to the increasing fluorescence intensity of CuNCs. A good linear relationship in the range of78μM-20mM was achieved between the fluorescence intensity of CuNCs at455nm and the logarithm of the PPi’s concentration with the detection limit (3σ) of101nM. The linear equation is F=752.7log c+1142.1. By this approach, the purpose of simple, fast and inexpensive detection of PPi can be realized.In summary, in this research, we successfully achieved a sensitive analysis of viral genes sequence by combining DNA-AgNCs with MWCNTs. Subsequently, a new method for the synthesis of fluorescent CuNCs was established which solved the difficulties of CuNCs synthesis. The innovation of this research was reflected in that a universal method was establish for detecting gene sequence by using DNA-AgNCs and MWCNTs. Additionally, the application scope of CuNCs was expanded and their theoretical studies were also deepened.