Abstract:The size distribution and ESR of uniform platinum microcrystals have been investigated. The mean size is typically about 20 Å, with a standard deviation of less than 4 Å. The sizes follow a log-normal distribution, with σ =1.2 ± 0.02. An ESR signal has been observed in the range 17-291 K and is attributed to the platinum microcrystals. The g-factor is 2.001 9 ± 0.000 2, and the width is about 20 G. The temperature dependence of the ESR susceptibility is in good agreement with a Curie law. The lineshape, g-fact… Show more
“…It is clearly seen that Δ g 2 and Δ H rise dramatically with an increasing amount of the coating thiol layer on the particles. Indeed, for the Pt-1.05 nanoparticles with full coverage, Δ g and Δ H are very large, with the value of 0.335 and 111 mT, respectively, which are contrasted with 0.0004 and 2 mT for the naked Pt nanoparticles, suggesting orders-of-magnitude increases. The large Δ g and Δ H values indicate the generation of the fast spin−lattice relaxation centers in the octadecanethiol-monolayer-coated Pt particles.…”
Section: Resultsmentioning
confidence: 90%
“… 9 The thiol/Pt ratio dependence of Δ g 2 and Δ H measured at room temperature for the thiol-coated Pt nanoparticles. The data for the naked Pt particle (thiol/Pt = 0) is obtained from ref .…”
The structure and electronic properties are investigated for Pt nanoparticles coated with octadecanethiol selfassembled monolayer. The increase in the octadecanethiol/Pt ratio from 0 to full coverage reduces the average particle size from 2.2 to 0.9 nm. The temperature-independent spin susceptibility rises upon the increase in the particle size, quantum size effect being suggested to govern the magnetism. The low-temperature susceptibility shows a large Curie-type divergence, which cannot be explained simply by the even electron state of Pt. XPS spectra suggest an electron deficiency in the interior Pt nanoparticles, which is brought about by charge transfer from nanoparticle to coating thiol monolayer. The ESR line width and the g-value deviation increase as the octadecanethiol/Pt ratio is elevated, which are associated with the enhancement of spin-orbit interaction at the interface between the interior nanoparticle and coating thiol monolayer. This change at the interface works to make first spin-lattice relaxation centers in the carrier scattering process.
“…It is clearly seen that Δ g 2 and Δ H rise dramatically with an increasing amount of the coating thiol layer on the particles. Indeed, for the Pt-1.05 nanoparticles with full coverage, Δ g and Δ H are very large, with the value of 0.335 and 111 mT, respectively, which are contrasted with 0.0004 and 2 mT for the naked Pt nanoparticles, suggesting orders-of-magnitude increases. The large Δ g and Δ H values indicate the generation of the fast spin−lattice relaxation centers in the octadecanethiol-monolayer-coated Pt particles.…”
Section: Resultsmentioning
confidence: 90%
“… 9 The thiol/Pt ratio dependence of Δ g 2 and Δ H measured at room temperature for the thiol-coated Pt nanoparticles. The data for the naked Pt particle (thiol/Pt = 0) is obtained from ref .…”
The structure and electronic properties are investigated for Pt nanoparticles coated with octadecanethiol selfassembled monolayer. The increase in the octadecanethiol/Pt ratio from 0 to full coverage reduces the average particle size from 2.2 to 0.9 nm. The temperature-independent spin susceptibility rises upon the increase in the particle size, quantum size effect being suggested to govern the magnetism. The low-temperature susceptibility shows a large Curie-type divergence, which cannot be explained simply by the even electron state of Pt. XPS spectra suggest an electron deficiency in the interior Pt nanoparticles, which is brought about by charge transfer from nanoparticle to coating thiol monolayer. The ESR line width and the g-value deviation increase as the octadecanethiol/Pt ratio is elevated, which are associated with the enhancement of spin-orbit interaction at the interface between the interior nanoparticle and coating thiol monolayer. This change at the interface works to make first spin-lattice relaxation centers in the carrier scattering process.
“…ESR measurements also give detailed insight into the location of the unpaired electrons. The squared g ‐value deviation Δ g 2 [= ( g – g 0 ) 2 , g 0 = 2.0023 is the g ‐value of free electron spin] and the line width Δ H of the ESR absorption at room temperature are significantly larger than those in naked Pt nanoparticles 21. These values are nearly independent of temperature and significantly rise as the mean particle diameter decreases (Figure 4, c).…”
Section: Interface Effects On the Electronic Structure Of Metal Nanopmentioning
confidence: 96%
“… The particle diameter ( d ) dependence of (a) the Pauli paramagnetic susceptibility χ 0 , (b) the spin concentration N s and (c) the g ‐value [Δ g 2 (circles)] and line width Δ H (triangles) in ESR spectra. The open symbols denote data for Pt nanoparticles without capping molecules 21…”
Section: Interface Effects On the Electronic Structure Of Metal Nanopmentioning
Keywords:Metal nanoparticles / Quantum-size effect / Metal-organic interface / Exchange enhancement / Single particle magnetAlkanethiol-coated metal nanoparticles are fascinating materials for designing unconventional electronic and magnetic functions. Novel classes of magnetic nanosystems can be created using Pd and Pt nanoparticles and their alloys with a 3d transition metal using quantum size, interface and exchange enhancement effects. The charge transfer at the metal-organic interface and the quantum size effect render Pt and Pd nanoparticles magnetic with localised moments. The substitution of capping molecules with a TTF derivative having a
“…For the same reason, significant deviations of the g-factor from the bare-electron value have been observed in platinum metal structures [37] (and refs. therein), including Pt nanoclusters [38] (we are aware of only one work [39] whose results do not agree with this trend). Therefore, our g-factor measurement provides an experimental indication against the hypothesis of a cluster consisting of pure platinum.…”
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