Synthesis Of Au And AuPd “Superstructures” For Photothermal,Photoassisted Electrocatalytic Properties

Noble metal nanomaterials show unique physical and chemical properties,some of which,for some specific applications,need to be strengthened or weakened by changing the size and morphology of nanoparticles.In fact,single nanoparticles are extremely limited in practical applications,and more often,numerous nanoparticles work together as an entity.For example,Au nanomaterials with strong absorption in the near infrared region have been widely used in tumor therapy in recent years.However,the absorption spectrum of small-sized Au nanoparticles is mainly in the visible re gion,so their application in tumor therapy is limited.To efficiently use the collective effect of nanoparticles,controllable assembly of nanoparticles into an entity has become a“hot topic”in the field of nanotechnology.Therefore,to develop the assembly technology of nanoparticles,this thesis fabricates Au and AuPd nanoparticle superstructures by using Au and AuPd nanoparticles,respectively,and explores their corresponding properties and applications:(1)Three-dimensional sphere-like Au nanoparticle superstructures(Au NPST)were synthesized by using Au nanoparticles as building blocks via an oil-in-water(O/W)microemulsion assembly method.Also,to achieve stable Au NPST,dopamine was used to polymerize around Au NPST,forming Au NPST/polydopamine(PDA)core/shell structure(Au NPST/PDA).This study provides a new strategy for stabilizing nanoparticle superstructures.(2)Compared to naked Au NPST,Au NPST/PDA hybrid show much better tolerance to strong acid and alkali and exhibit satisfactory photothermal conversion effect,capable of working as photothermal therapy agent.The results indicate that Au NPST/PDA show a photothermal conversion efficiency of 33%,higher than that of Au NPST(23%).In vivo and in vitro photothermal treatment,Au NPST/PDA can kill 80%of cancer cells under the irradiation of laser(200 mg _Au L^-1,808 nm,1.2 W cm^-2).Tumor-bearing mice were used as a xenograft model.After i ntratumoral injection of Au NPST/PDA,the growth of the tumor was suppressed under the irradiation of 808 nm laser(1 W cm^-2),and the tumor was basically eliminated after two weeks.Also,Au NPST/PDA did not cause significant toxicity for the main organs and tissues of mice during the treatment.(3)Three-dimensional sphere-like AuPd nanoparticle superstructures(AuPd NPST)were synthesized by using AuPd nanoparticles as building blocks via an oil-in-water(O/W)microemulsion assembly method,and used for plasmon-assisted electrooxidation of methanol.The results indicate that as-prepared AuPd NPSTs show satisfactory electrocatalytic activity,?4.8 and 1.1 times better than AuPd nanoparticles and commercial Pd/C,respectively,suggesting that the synergistic effect between nanoparticles contributes for the improvement of the elect rocatlytic activity of AuPd NPST.When AuPd NPST were irradiated by full-wave sunlight with a power density of 40 m W cm^-2,AuPd NPST,compared with that under dark conditions,exhibit40%improvement of the catalytic current density towards methanol electrooxidation,indicative of its plasma-enhanced catalytic performance.Additionally,AuPd NPST show superior long-term catalytic stability than AuPd nanoparticles and Pd/C thanks to the regular arrangements of AuPd nanoparticles.