Nanoshel alloy nanoparticles are having chemical and physical properties which can be tuned by varying the composition and atomic ordering as well as the size of the clusters. In fact, nanoalloys may display not only magic sizes but also magic compositions, i.e., compositions at which the alloy nanoclusters present a special stability. Surface structures, compositions, and segregation properties of nanoalloys are of interest as they are important in determining chemical reactivity and especially catalytic activity.

Nanoalloys are also of interest as they may display structures and properties which are distinct from those of the pure elemental clusters: the structures of binary clusters may be quite different from the structures of the corresponding pure clusters of the same size; synergism is sometimes observed in catalysis by bimetallic nanoalloys. They may also display properties which are distinct from the corresponding bulk alloys due to finite size effects, e.g., there are examples of pairs of elements (such as iron and silver) which are immiscible in the bulk but readily mix in finite clusters.

Nanoshel nanoalloys with well-defined, controllable properties and structures on the nanometer scale coupled with the flexibility afforded by intermetallic materials has generated interest in bimetallic and trimetallic nanoclusters, which will be referred to as alloy nanoclusters or nanoalloys. As for bulk alloys, a very wide range of combinations and compositions are possible for nanoalloys. Bimetallic nanoalloys can be generated with, more or less, controlled size and composition.

Nanoshel Nanoalloys are interesting from a basic science point-of-view due to the complexity of their structures and properties. Nanoalloys are presently a very lively research area, with impressive developments in the last ten years. Nanoalloys can find an application in biosensing and nanomedicine.

The colloidal metal alloy NPs, especially platinum-based alloys have been the choice of catalysts in many important chemical and electrochemical reactions including oxygen reduction reaction (ORR) and direct methanol oxidation reaction (MOR). Also nanoalloys catalysts have tunable parameters, such as particle size and atomic composition, which affect critical atomic-scale structural features