The disclosed technology relates generally to material systems which include a plurality of particles and methods of making the same. The particles have a core and a shell which encapsulates the core and has at least one atomic element not included in the core. The cores of the particles have a median maximum dimension that is less than 10 microns and a median of at least one axial dimension that is between 10 nm and 500 nm. The shells of the particles have a median thickness that is less than 100 nm, a silicon concentration that is between 10% and 50% on the basis of the weight of the shells, and an aluminum concentration that is between 0.01% and 5% on the basis of the weight of the shells.

A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

The present invention concerns methods of forming metal-containing nanoparticles or oxide thereof, especially metal alloy nanoparticles. The method the steps of providing at least two different kinds of transition metal ion by providing at least two kinds of metal ion-containing compound; a heating step in which the at least two metal ion-containing compounds are subjected to a temperature of at least 300 C. to form the metal alloy nanoparticles; a cooling step comprising cooling the product of step b; and each metal ion-containing compound is a transition metal complex having ligands coordinated to a transition metal ion, the ligands being selected from the group consisting of glyoxime; a glyoxime derivative; salicylaldimine; and a salicylaldimine derivative. The preferred methods are solution-based methods. Products of the methods are also described, as are their uses as electrocatalysts, as well as uses of the metal ion-containing compounds for making nanoparticles.