Preparation, Characterization And Properties Of Metal And Semiconductor Nanoparticles

(1). 3.5 G PAMAM and 4.5 G PAMAM were firstly synthesized and were used asstabilizing agents, Au nanoparticles have been prepared by reducing HAuCl₄ withmicrowave irradiation method. The influence of microwave irradiation time at the sameratio of 3.5 G PAMAM (4.5 G PAMAM) to HAuCl₄ and the different ratios of 3.5GPAMAM (4.5 G PAMAM) to HAuCl₄ for the same irradiation time on Au nanoparticles'size and shape has been studied. Au nanoparticles were characterized by UV-vis spectra,TEM and XRD. At the same ratio of 3.5 G PAMAM (4.5 G PAMAM) to HAuCl₄, themicrowave irradiation time had a little influence on the Au nanoparticles' size and shape,meanwhile monodispersed Au nanoparticles were obtained with the appropriate increase ofreactive time. Under the same irradiation time, bigger and more aggregative Aunanoparticles were acquired as the ratio of 3.5 G PAMAM (4.5 G PAMAM) to HAuCl₄was decreased.(2). Palladium nanoparticles protected by PVP were obtained firstly by reducingPdCl₂ with NaBH₄ solution. Then, different size palladium nanoparticles with a large sizerange (1.49 nm-23.26 nm) were prepared by the multi-step reduction of PdCl₂ byhydrogen absorbed on the surface of palladium nanoparticles. It's worthy to mention thatthe size increment-step of palladium nanoparticles was relatively larger than that ofplatinum nanoparticles using the same method, which reflected the palladium nanoparticleshad higher hydrogen absorption capacity.(3). CdS nanoparticles protected by 3.5 G PAMAM (4.5 G PAMAM) were prepared.CdS/Au nanocomposites were synthesized by reducing HAuCl₄ with the microwaveirradiation on the CdS seeds. UV-vis,TEM and fluorescence spectra were used tocharacterize the nanoparticles. The results indicated that CdS nanoparticles' size grewmuch larger and fluorescence spectra was stronger as the ratio of 3.5 G PAMAM (4.5GPAMAM) to HAuCl₄ was decreased. CdS/Au nanocomposites' size was larger and fluorescence spectra was weaker as the ratio of CdS to Au was decreased.(4). Au-core/Pt-shell bimetal nanoparticles were successfully synthesized by a simpletwo-step method. Au colloids with an average diameter of 13.9 nm were prepared by theTurkevich method, reducing HAuCI4 with Na₃C₆H₅O₇ solution. Then, as a protectivereagent, PVP was added into Au colloids in order to replace the C₆H₅O₇^3-. After that,Au-core/Pt-shell bimetal nanoparticles were prepared by reducing H₂PtCl₆ with H₂ afterH₂C₂O₄ solution was added into the mixture. UV-vis spectra, TEM and XRD were used tocharacterize the nanoparticles. The results identified that the core-shell bimetalnanoparticles could be obtained under the optimizedly reactive condition. In the formationof Au-core/Pt-sheU bimetal nanoparticles, the poly (N-vinyl-2-pyrrolidone) replacement ofcitrate and the existence of H₂C₂O₄ play key roles in this synthetic process.Key words: Gold nanoparticles, Palladium nanoparticles, Microwave irradiation, 3.5 GPAMAM, 4.5 G PAMAM, CdS nanoparticles, CdS/Au nanocomposites, Au@Pt bimetalnanoparticles...