| In addition to Ag and Au, Cu is another metal known to exhibit localized surface plasmon resonance (LSPR) peaks in the visible or near-infrared region when it is prepared as nanostructures. Moreover, low cost copper nanostructures with different shapes are also of great interest and importance for applications in microelectronics and catalysis. All of these fundamental studies and applications would greatly benefit from the availability of Cu nanocrystals with well-defined and controllable shapes, as well as in large quantity and good uniformity. However, the susceptibility of Cu upon exposure to air complicates the synthesis and applications of Cu nanocrystals. Therefore, many researchers have tried to combine one or more metals inert in the air (such as Au, Pd) and Cu. On the one hand, that will ameliorate the instability of Cu towards oxidization. On the other hand, this combination will predictably pull down the high cost of noble metals and change the surface electronic states of metal nanocrystals which will endow the nanocrystals high activities or particular properties. This dissertation aims to describe the synthesis of some copper based nanoalloys. We integrated various shape controlled methods to carefully design and synthesize some structures, for example, planar tetrapods with symmetry reduction and hypercubes with high atom utilization. The successfully synthesized nanostructures not only expand the train of thought of design in the field of basic research, but also show superior performance in the optical and catalytic fields. This dissertation contains four chapters and the contents are outlined as following.In chapter one, we briefly introduce the theory of crystal growth and several methods for the synthesis of metal nanocrystals, and illustrate the influence of some experimental parameters on the morphology control. Then we describe how to use the utility to design and synthesize some special metal nanostructures which make a significant contribution to the research on basic theory, or we can carefully design metal nanostructures considering that the nanostructures with high index facets or branches have significant performance in the field of catalysis, optics, etc.In chapter two, we first introduce several influence factors in the formation of branched nanostructures. Then, we emphatically analyzed the influence of kinetic control and core-shell lattice mismatch on crystal growth in the seeded growth process. Combining the above two methods, Pd@AuCu core-shell planar tetrapods with reduced symmetry were successfully achieved. By simply adjusting the amounts of the Pd cubic seeds, the sizes of nanocrystals could be well-controlled in the range from 33 to 70 nm. Through size control, the peak position corresponding to the in-plane dipole mode shifted from visible to near-infrared region with the elongated pods. Owing to the unique branched structure with tips and edges, the obtained Pd@AuCu core-shell planar tetrapods exhibited excellent performance in SERS applications with a high enhancement factor.In chapter three, we first analyzed several important influence factors in the formation of the nanoframe structures. Then, we described the synthesis of Pd@PdCu nanocubes using seeded growth method, and finally got Pd@PdCu hypercubic nanostructures by means of oxidation etching at room temperature. We analyzed the structure and composition of an individual Pd@PdCu hypercube in detail. Moreover, we analyzed the changes of the composition and valence state on the metal surfaces before and after oxidation etching. Lastely, we explored the application of the nanocrystals with 3D open structure in the CO2 electrochemistry reduction.In chapter four, we firstly describe the application prospect of metal nanocrystals. Then, we expound the some opportunities and challenges existing in the research of metal nanocrystals, considering how to improve synthesis methods and explore the function mechanism of morphology control factors in the formation process of metal nanostructures. |
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