| Summary: | 碩士 === 淡江大學 === 化學學系碩士班 === 106 === Gold Nanorods (AuNRs) with aspect ratio 5 (50 nm × 10 nm) are synthesized with an improved seed-mediated growth method, and gold nanodumbbells (AuDBs) with aspect ratio 5.7 (57 nm × 10 nm) are prepared via the second reduction of gold ions on the AuNRs. Further, the surfaces of AuNRs and AuDBs are modified by L-cysteine, and they are subsequently employed in the synthesis of gold-silver core-shell nanoparticles through the reduction of silver ion onto their surfaces. Effect of surface modification with different reaction conditions such as surfactants and temperatures are studied. In the cationic surfactants, silver shells grow on the surfaces of AuNRs and AuDBs in a one‐step process. For the anionic surfactants system, silver shells grow on AuNRs and AuDBs in a multi‐step processes at room temperature. At high temperature (75 oC), chelating agent and metal salts such as NaCl and NaBr as additives can assist the silver shells grow because the reduction rate of silver ions can be modulated via the competitive reaction. Surface modification of AuNRs and AuDBs is contributed to better monodispersity of the silver shells in anionic surfactants system; however, L-cysteine modified AuNRs and AuDBs would inhibit the silver shell grow on the surfaces at the ends of them.
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