Unexpected magnetism in gold nanostructures: making gold even more attractive

Abstract

Gold nanostructures have attracted widespread attention due to their novel optical, electronic, and biocompatible properties. These make gold nanostructures (and in particular nanoparticles) very attractive for a variety of applications, including catalysis, therapeutics, diagnostics, sensing, and nanoelectronics. In this topical review, the newly discovered magnetic properties of gold nanostructures are highlighted. This unexpected magnetism in gold nanoparticles is a result of (1) the predominant effect of surfaces at the nanoscale, (2) the electronic modification to gold from strongly capping molecules, and (3) the strong spin-orbit coupling of gold. This review discusses the salient experimental results, a theoretical model, and closes by highlighting possible industrial applications of magnetic gold nanostructures.

Giant Magnetic Susceptibility of Gold Nanorods Detected by Magnetic Alignment

“…Several explanations were suggested, such as competing magnetic contributions of the NP core and surface [3], the formation of a magnetic moment due to the exchange of charges at the Au-ligand interface [5,6,8], the creation of large orbital moments due to electron motion within surface clusters [9], and the occurrence of persistent currents in the Au core [2]. However, so far, the origin of this unexpected magnetism and why it differs strongly between different types of NPs is not yet understood [2,10,11].We employ a novel magnetic alignment technique to measure the magnetic properties of rod-shaped Au NPs in solution. We focus on relatively large NPs (all dimensions >7 nm) that are single crystalline.…”

Chemically Induced Magnetism in Atomically Precise Gold Clusters

“…nonmagnetic) in their bulk phase. [ 1 ] Most prominent among these are ligand stabilized ferromagnetic noble metal nanoparticles such as Au, Ag, Cu and Pt. [ 2,3 ] A number of gold nanoparticles stabilized by different ligands have been investigated for their magnetic behavior and it is now well documented that the magnetism is chemically-induced and strongly sizedependent.…”

Strong Paramagnetism of Gold Nanoparticles Deposited on aSulfolobus acidocaldariusSLayer

“…Gold nanoparticles (NPs) are being actively investigated because of their importance for medicine as antitumoral or antirheumatic vectors, on one hand, and, on the other hand, because of the fascinating size effects that their optical and, more recently, magnetic properties show under special conditions [1,2]. Thiol functionalized templates [3] can be used to promote the growth of Au NPs in organized arrays and to enhance the surface to volume ratio of atoms in the NP.…”

“…In recent studies [1,2] of Au NPs, paramagnetic (P) and spontaneous (S) magnetization are recognized as general features in most samples measured. For example, Au NPs capped with dodecanethiol show a small S component, usually persisting to high temperature, which yields a minute XMCD Au L 2;3 signal (XMCD $10 À5 ) [13], although the authors propose a large moment per atom, m Au ¼ 0:33 B , by assigning the signal only to surface atoms.…”