title: Ferromagnetism exhibited by nanoparticles of noble metals.
abstract: Gold nanoparticles with average diameters in the range 2.5-15 nm, prepared at the organic/aqueous interface by using tetrakis(hydroxymethyl)phosphonium chloride (THPC) as reducing agent, exhibit ferromagnetism whereby the saturation magnetization M(S) increases with decreasing diameter and varies linearly with the fraction of surface atoms. The value of M(S) is higher when the particles are present as a film instead of as a sol. Capping with strongly interacting ligands such as alkane thiols results in a higher M(S) value, which varies with the strength of the metal-sulfur bond. Ferromagnetism is also found in Pt and Ag nanoparticles prepared as sols, and the M(S) values vary as Pt>Au>Ag. A careful study of the temperature variation of the magnetization of Au nanoparticles, along with certain other observations, suggests that small bare nanoparticles of noble metals could indeed possess ferromagnetism, albeit weak, which is accentuated in the presence of capping agents, specially alkane thiols which form strong metal-sulfur bonds.
authors: CSIR Centre of Excellence in Chemistry, International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore, India.
authors: Urmimala
authors: U
authors: Maitra
authors: Barun
authors: B
authors: Das
authors: Nitesh
authors: N
authors: Kumar
authors: Athinarayanan
authors: A
authors: Sundaresan
authors: C N R
authors: CN
authors: Rao
mesh_terms: D006046:Gold / Q000737:chemistry*; D060328:Magnetic Phenomena; D059346:Magnets; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D009943:Organophosphorus Compounds / Q000737:chemistry; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D009943:Organophosphorus Compounds; D013438:Sulfhydryl Compounds; C014850:tetramethylolphosphonium chloride; D012834:Silver; D010984:Platinum; D006046:Gold