Preparation Of Copper Nanocluster Based On Framework Nucleic Acid And Its Application

Copper nanoclusters(CuNCs)are generally constructed from a few to hundreds of copper atoms,and they have received extensive attention from researchers because of their excellent properties.For quantum dots and organic dyes,CuNCs is a water-soluble nanomaterial with large Stokes shift,excellent optical properties,low biotoxicity and strong biocompatibility.These advantages enable CuNCs to be applied to the construction of biosensors and bioimaging.At the same time,the green and gentle preparation method,low price and abundant precursors have also successfully expanded the application range of CuNCs.However,CuNCs still have shortcomings such as low quantum yield and poor stability in terms of synthesis and application.The addition of ligands can effectively improve the optical emission intensity,quantum yield and stability of CuNCs.Therefore,in order to obtain CuNCs with excellent optical performance and favorable stability for biological imaging and sensing,we have carried out the following research work,which includes the following aspects:1.Research on the design,synthesis,characterization and property of copper clusters based on framework nucleic acidsSingle CuNCs have low quantum yield and poor stability.In order to improve the optical performance and stability of CuNCs copper nanoclusters,we designed one-dimensional DNA nanoribbons(DNR)and two-dimensional DNA nanosheets(DNS)for the construction of CuNCs.The CuNCs with DNR as template(DNR/CuNCs)and the CuNCs with DNS as template(DNS/CuNCs)were synthesized,and the length and spacing of specific sequences were different.We characterized the morphology of CuNCs and proved that CuNCs with DNA nanostructures as templates were successfully synthesized.To study the influence of different DNA nanostructures on the optical properties of CuNCs,the length of the specific sequence will control the binding site of CuNCs.As the binding site increases,the emission intensity and quantum yield increase.We also found that too small spacing between specific sequences will cause fluorescence quenching and decrease quantum yield.In terms of quantum yield,DNS/CuNCs is 62 times that of single CuNCs and 4.7 times that of DNR/CuNCs with similar specific sequence lengths,indicating that the two-dimensional ordered assembly of CuNCs is more helpful to improve optical emission and quantum yield.2.Electrochemiluminescence based on DNR/CuNCsThe electrochemiluminescence(ECL)signal of CuNCs is low.In order to enhance the intensity of its ECL signal,we use DNR/CuNCs as the ECL group to construct an electrochemiluminescence sensor.The ECL performance of DNR/CuNCs was experimentally studied,and it was found that DNR/CuNCs has an electron injection process at the cathode and has a cathode ECL signal,and the ECL intensity of DNR/CuNCs is higher than that of a single CuNCs,which proves that the orderly assembly of CuNCs is beneficial to increase the ECL intensity.By changing the direction of the potential scan,it is found that DNR/CuNCs will be oxidized and then reduced,which will help to obtain a higher ECL signal.For different DNR/CuNCs,the ECL signal intensity increases with the increase of the specific sequence length,while a smaller distance will reduce the ECL signal intensity.For annihilation and co-reaction ECL,the ECL signal intensity of co-reaction is stronger than that of annihilation.Based on the above research,we selected DNR F/CuNCs with the longest specific sequence to detect dopamine using the principle of co-reactive ECL,and designed a label-free "signal off" ECL sensor,which effectively improved the detection sensitivity.3.Fluorescence imaging based on DNS/CuNCsIn the fluorescence imaging of live cells,it is usually necessary to wash excess probes to obtain a high signal-to-background ratio.However,washing cells is not only tedious and time-consuming,but also affects the cell environment and causes apoptosis.We choose DNS/CuNCs as the donor and the near-infrared fluorescent dye Cy5.5 as the acceptor to construct an fluorescence energy resonance transfer system(called DNS/CuNCs-Cy5.5)to remove the background signal to achieve wash-free imaging.Researching antenna effect of DNS/CuNCs-Cy5.5,we found that the system can also achieve the effect of signal amplification.Exploring the influence of DNS/CuNCs-Cy5.5 on the fluorescence performance,we found that the improved photobleaching resistance of the system can be applied to long-term dynamic imaging,and it also improves the fluorescence quantum yield and fluorescence lifetime.