Erratum: Permanent Magnetism, Magnetic Anisotropy, and Hysteresis of Thiol-Capped Gold Nanoparticles [Phys. Rev. Lett.93, 087204 (2004)]

Surface plasmon resonance of capped Au nanoparticles

“…TEM analysis of the samples studied here showed that there was no aggregation. 9 Moreover, it is well known that NP aggregation shifts the position of the resonance toward lower energies ͑the red and infrared part of the spectrum͒ while the plasmons analyzed here showed the resonance located at the position that correspond to well-dispersed nanoparticles. We also measured the optical absorption in the red and infrared part of the spectrum but we found no signal in this region, so we can discard aggregation effects in our samples.…”

“…However, several extended x-ray absorption fine structure Extended X-ray Fine Absorption Spectroscopy ͑EX-AFS͒ experiments of thiol-capped Au NPs showed that the charge transfer at the Au-S bond is about 0.04 electron per atom. 7,9 Although the calculations reproduce the experimental results, the parameters used have no physical meaning and therefore the electron density decrease cannot be invoked as the unique reason for the changes in the SPR.…”

“…[7][8][9][10][11][12][13] As a consequence of these changes in the electron configuration, the physical properties of the NPs change significantly; the most outstanding one is the ferromagneticlike behavior of thiol-capped Au NPs despite the diamagnetic character of bulk gold. 9 Thiol-capped Au NPs also exhibit a wider SPR than bare NPs, which is associated with an extra dampìng due to the interaction of conduction electrons with the thiols. 2, 14,15 In some cases, thiol capping even yields to the absence of a SPR absorption band in the spectrum.…”

“…2, 14,15 In some cases, thiol capping even yields to the absence of a SPR absorption band in the spectrum. 8,9 The mechanism responsible for these changes in the optical properties of Au NPs induced by the thiols is not clear. Furthermore, there is a controversy even about the metallic or insulating character of small ͑below 2 nm size͒ thiol-capped Au NPs.…”

Magnetic Properties of ZnO Nanoparticles

“…It is evident that not any alteration of the electronic structure of ZnO will arise the ferromagnetism but only under certain circumstances. Actually, we found that slight modifications in the preparation conditions and size of thiol-capped Au NPs lead to important variations in their magnetic properties [13], and for DMS small differences in the preparation methods also lead to apparently 9/11 irreconciliable results, suggesting that slight variation of the electronic structure can lead to large variation of the magnetic properties. Thus, it is possible that the different preparation method used by Kittilstved and Gamelin, yield reduced values of magnetization for their samples that make the magnetic moments undetectable (note that the magnetization value we measured for AMINE is fairly small and close to the detection limit of the SQUID).…”