Modulation And Applications Of Localized Surface Plasmon Resonance Performance Of Cu_2-xS Nanodisks

Localized surface plasmon resonance(LSPR)is an optical phenomena in which the incident light wave causes the free carrier resonance oscillation,which results in the enhancement of the surface electromagnetic field.It has been found that LSPR can enhance the light absorption,luminous efficiency and photothermal conversion efficiency of functional nanocrystals,which showing important application potentials in the fields of optical communication,photoelectric sensing,biosensing and photothermal therapy.Due to the intrinsic high carrier concentration,the LSPR absorption peak of traditional noble metal nanomaterials such as Au and Ag nanoparticles is in the visible band,which is difficult to match the optical window of biological optical window(650-1350 nm)and communication optical window(850nm,1310 nm,and 1550 nm).In addition,the raw materials and preparation costs of Au and other nobel metal nanostructures are relatively high,making it difficult to be widely used.In this paper,the octadecene was used as the high-temperature organic phase synthesis solvent,Oleylamine was used as the surface ligand,to synthesize the Cu_2-xS(x=0,0.25,1)nanodisks at 180? high-temperature organic phase,and research the LSPR effect in the NIR.Cu_2-xS nanocapsules and thin films were assembled to study the enhancement effects of photothermal ablation and photoelectric sensing,and explore new NIR photothermal sensitizers and photoelectric detector.The main research contents and research results were as follows:(1)Synthesis and optical properties of Cu_2-xS nanodisks.Thre hydrophobic copper sulfide nanodisks were prepared by high-temperature oil phase method.It was found that the size,crystal phase,copper sulfide ratio and solvent dielectric constant were the main factors affecting the optical properties of LSPR.The Cu_2-xS nanodisks have strong light absorption in the near-infrared region of 750-1600 nm,which can effective match the 808 nm biological tissue optical window and the 1310 nm communication optical window.(2)The LSPR effect and mechanism of Cu_2-xS nanodisks were analyzed by Finite Difference Time Domain(FDTD)numerical method.Analysis by the Drude model revealed that Cu defects produced a large amount of holes(2.85�10²¹cm^-3-5.4�10²¹cm^-3)in the Cu_2-xS nanodisks.Furthermore,the FDTD simulation results show that there are two in-plane and out-of-plane LSPR modes in the CuS nanodisks,and the LSPR absorption peak with the nanodisks size and solvent refractive index increase the red shift.(3)Mechanism and application of Cu_2-xS nanodisk LSPR to enhance photothermal effect.The FDTD simulation analysis shows that the assembly form of the nanodisks directly affects the localized electric field distribution and the photothermal enhancement effect.The multi-disk coupling localized electric field strength is twice the coupling electric field strength of a single nanodisk,and the distance between the nanodisk and the nanodisk will be directly affecting the mode coupling efficiency,the coupling between the disks produces a"hot spot"that affects its localized electric field distribution and photothermal effect.For theoretical analysis,Cetyltrimethyl Ammonium Bromide(CTAB)and polyoxyethylene polyoxypropylene ether block copolymer(Pluronic,F127)were used to synthesis Cu_2-xS/SiO₂composite.Controllable single or multi-load assembly of capsules.Comparing the photothermal efficiency of single-disk-loaded S-Cu_2-xS/SiO₂ nanocapsules and multi-plate surface-surface self-assembled A-Cu_2-xS/SiO₂ nanocapsules,it was found that under808 nm near-infrared laser irradiation,two kinds the photothermal conversion efficiencies of the capsules were 21%and 30.2%,respectively,and the photothermal efficiency was increased by 1.44 times.It also verified the theoretical result that there have a stronger localized electric field.At the same time,the Cu_2-xS nanomaterials were tested for photothermal cancer cell killing in vitro.The results showed that the multi-disk surface-surface self-assembly killing rate was about 70%,which proved to have good photothermal ablation effect.(4)Research of Cu_2-xS nanodisks LSPR enhanced near-infrared photodetector.PbS semiconductor quantum dots with an average particle size of 5.4 nm were synthesized by hot injection,and the exciton absorption peaks were located at 1300nm.The FDTD Solutions simulated CuS nanodisks array haace LSPR absorption in the PMMA environment,and a strong electric field near the surface of the nanodisks in the 1310 nm band,especially at the coupling between the disk and the disk,produces a"hot"point,and its relative electric field strength ?E/E₀?² reaches 80.The photocurrent of the Cu_2-xS/PMMA/PbS composite thin film photodetector is improved by 4.3 times that of the PbS quantum dot photodetector.