Study On The Regulation And Performance Of Gold,Silver And Copper Plasma Resonance

Gold,silver,copper and other precious metal nanoparticles have local surface plasmon resonance(LSPR)effect,which can strongly absorb light and change the distribution of electromagnetic field around nanoparticles.The LSPR effect can be used to achieve fluorescence enhancement,Raman enhancement and photothermal conversion.However,the influencing factors of LSPR are still lack of systematic and in-depth investigation.In this thesis,gold,silver and copper(Au,Ag,Cu)nanoparticles(NPs)with different compositions,shapes and sizes were prepared by chemical reduction method.FDTD Solutions were used to simulate and analyze the changes of electromagnetic field distribution.The precious metal nanoparticles were applied to fluorescence enhancement of carbon quantum dots(CDs),Raman signal enhancement of organic molecules,and photothermal conversion of water,respectively.Firstly,Au,Ag and Cu based NPs were prepared to enhance the fluorescence performance of CDs,and the distance between CDs and metal nanoparticles was controlled by adjusting the thickness of Si O₂ layer and the surface charge.It was found that the LSPR electromagnetic field was reduced and the fluorescence enhancement effect was decreased with the increase of Si O₂ thickness.Au and Ag NPs can increase the emission intensity of green emission CDs(GCDs)by 1.6 times and 2 times,respectively.FDTD simulation disclosed that LSPR field of Ag NPs is stronger than that of Ag NPs.Au@Ag core-shell NPs and Au Ag alloy nanoflower can enhance the intensity of red emitting CDs(RCDs)with 1.2 times and 2 times,respectively.The difference in enhancement effect is due to the fact that the strongest LSPR electromagnetic spot of Au@Ag NPs is too close to the surface of Au@Ag NPs,while the electromagnetic field of Au Ag alloy nanoflower tips is stronger.The fluorescence lifetime is basically unchanged,so the enhancement mechanism is induced by excitation field enhancement.The absorption of Cu O nanosheet overlaps with yellow emitting CDs(YCDs),and the fluorescence intensity of YCDs can be increased by 1.63 times,which is attributed to stronger excitation energy.Secondly,Au,Ag and porous Au Ag alloy NPs were synthesized to enhance the Raman signal of rhodamine 6G(R6G).Ag NPs has better performance on Raman enhancement than Au NPs with same size,because Ag NPs has stronger LSPR electromagnetic fields.The detection limit of Au/R6G and Ag/R6G is 10^-8 M and 10^-12 M,respectively.In addition,Au Ag alloy NPs also have good Raman enhancement.It was found that the Raman signal of R6G is first enhanced and then weakened with the increase of Au content.Au_0.23Ag_0.77 alloy NPs have the best Raman enhancement effect,and the detection limit is up to 10^-14 M.Through FDTD simulation,it was found that the porous Au Ag alloy NPs have the highest LSPR electromagnetic intensity,a large number of hot spots and high specific surface area.Finally,Au,Ag and Cu NPs with strong spectral absorption characteristics were used to photothermal conversion of water,and the photothermal conversion efficiency was calculated by measuring the temperature and mass change of water.Under a Xe lamp with a light intensity of 150 m W/cm²,the photothermal efficiency of pure water is 1.34%.With the addition of metal nanoparticles,the photothermal efficiency is obviously increased.The photothermal efficiency can be enhanced with the increase of metal nanoparticle size.In addition,the photothermal efficiency of Au nanostar and nanorods is9.01%and 5.39%,respectively,which is due to their strong LSPR electromagnetic field.Moreover,the wide spectral absorption range also helps to improve the photothermal efficiency.The efficiency of Au@Ag NPs is 5.93%,which is better than that of Au or Ag NPs.The photothermal efficiency can also be improved by recombination with organic molecule PVA.After the recombination of Au NPs and PVA,the heat diffusion is inhibited,and the photothermal efficiency is improved by 1.5 times.