Synthesis, Structure, Properties, and Applications of Bimetallic Nanoparticles of Noble Metals

Abstract

Bimetallic nanoparticles of noble metals are of high interest in imaging, biomedical devices, including nanomedicine, and heterogeneous catalysis. Synthesis, properties, characterization, biological properties, and practical applicability of nanoparticles on the basis of platinum group metals and the coin metals Ag and Au are discussed, also in comparison with the corresponding monometallic nanoparticles. In addition to the parameters that are required to characterize monometallic nanoparticles (mainly size, size distribution, shape, crystallographic nature, surface functionalization, charge), further information is required for a full characterization of bimetallic nanoparticles. This concerns the overall elemental composition of a bimetallic nanoparticle population (ratio of the two metals) and the internal distribution of the elements in individual nanoparticles (e.g., the presence of homogeneous alloys, core-shell systems, and possible intermediate stages). It is also important to ensure that all particles are identical in terms of elemental composition, that is, that the homogeneity of the particle population is given. Macroscopic properties like light absorption, antibacterial effects, and catalytic activity depend on these properties. The currently available methods for a full characterization of bimetallic nanoparticles are discussed, and future developments in this field are outlined.

Versatile and robust synthesis process for the fine control of the chemical composition and core-crystallinity of spherical core–shell Au@Ag nanoparticles

“…It is based on the use of oleylamine to solubilize and reduce the silver metallic precursor for the shell under annealing for a controlled time at the surface of the Au seed, which is itself synthesized by different pathways in an organic medium. The resulting Au@Ag core-shell NPs are of controlled crystallinity and composition; factors that play a fundamental role in their optical and catalytic properties [13,30,31]. Furthermore, they have a narrow size distribution that facilitates their 3D assembly after deposition on a solid substrate for further applications as new SERS platforms with tunable optical properties [32].…”

Ultrasmall gold and silver/gold nanoparticles (2 nm) as autofluorescent labels for poly(D,L-lactide-co-glycolide) nanoparticles (140 nm)

“…Liu et al prepared gold nanoparticles with a size of 2.5 nm by reducing the gold in the presence of glutathione with different ratios of gold to ligand and found different emission maxima for the resulting nanoparticles [54]. However, it must be stressed not all ultrasmall nanoparticles of noble metals show autofluorescence [55][56][57]. Gold nanoparticles and clusters are especially useful for this purpose.…”

Synthesis, Properties, and Biological Applications of Metallic Alloy Nanoparticles

“…The catalytic properties of bimetallic nanoparticles depend on the structures that are different between the core–shell structure and the disordered structure and composition of alloy nanoparticles. Pt–Ni alloy nanoparticles catalyze the oxygen reduction reaction ten times faster than Pt nanoparticle [ 200 ]. Another report showed that Pt–Ru alloy and Pt–Ru core–shell nanoparticles show differences in catalytic reactions [ 201 ].…”