The Study On Controllable Synthesis Of MoO_x Nanostructure And Their Localized Surface Plasmon Resonances Characteristics

Localized surface plasmon resonance?LSPR?is the collective oscillation of charges on the nanomaterial surface motivated by the alternative electromagnetic field of induced light,which also causes the near-field enhancement for nanomaterial.This novel optoelectronic characteristic has been widely applied in different fields,such as optoelectronic devices,biology,chemistry and medical treatment.The existence of LSPR characteristic is mainly decided by the carrier concentration of a certain material.Noble metals,as well as heavily-doped semiconductors,are the typical and most studied materials with LSPR features and their LSPR wavelength locate at visible and infrared range,respectively,due to the different carrier concentrations.However,these materials can hardly exhibit strong LSPR in the near-infrared range,so-called biological window?700-1200 nm?because of the intrinsic deficiency and high fabrication cost,which limit the application of LSPR in the biological field.In this thesis,molybdenum oxides?MoO_x?with various nanostructures such as MoO₂ nanorod and MoO₃ nanosheet were fabricated through the combination of laser ablation in liquid?LAL?and solvothermal?ST?synthesis.The growth and transformation rules of these MoO_x nanostructures were also investigated from morphology,crystal structure,chemical composition and other aspects.It is concluded that both ethanol and the interaction between laser and oxygen released from H2O₂ have a reduction effect on the Mo ions,which resulted in the existence of Mo4+.On the other hand,metastable MoO₂.68 nanospheres gradually assemble into MoO_x cubes as the ablation time extends while the well-assembled cubes transformed into sheet-like orthorhombicMoO₃ nanostructures.When the ablation time further extended,all the cubes had transformed into stacked MoO₃ nanosheets.That is,metastable MoO₂.68 nanospheres assembled into crystalline orthorhombicMoO₃ nanosheets as the laser ablation duration extended.The LSPR characteristic of synthesized MoO₂ nanostructures were observed from experimental absorption spectrum and further confirmed by theoretical calculation.Both MoO₂ nanorods and MoO₂ nanoparticles exhibit strong LSPR in the NIR region,with the LSPR peaks locating around 800 nm.The obvious dependence of MoO₂ LSPR wavelength on the surrounding media and material morphology were also observed for the first time that the LSPR peak of MoO₂ nanostructure showed red-shift from 800-1010 nm according to the permittivity increase of surrounding media,as well as aspect ratio decrease of nanostructures.These varying trends were in line with the theoretical simulation results.These influence are of great meaning for the regulation and optimization of MoO₂ LSPR characteristics.The LSPR characteristic of our synthesized MoO₂ nanostructures is right in the biological window,which offers a solid theoretical basis for its application in the biological field.Finally,as-synthesized MoO₂ nanoparticles were used as a photothermal treatment?PTT?agent for cancer therapy.The photothermal temperature elevation ablity,biocompatibility,in-vitro photothermal therapy performance and in-vivo tumor inhibition ability of MoO₂ nanoparticles were investigated successively to reveal its performance as a PTT agent.The MoO₂ nanoparticles showed an excellent temperature elevation of up to 37.5? laser irradiation for 5 min and in-vivo MoO₂ PTT treatment showed a maximum tumor inhibition rate of 80.45%.The excellent PTT performance of MoO₂ offers a new method for seeking a stable,effective photothermal treatment with lower cost.