NMR evidence for energy gap opening in thiol-capped platinum nanoparticles

Possibilities and limitations of solution-state NMR spectroscopy to analyze the ligand shell of ultrasmall metal nanoparticles

“…38,39 For example, metallic behavior has been observed for thiol-capped Pt nanoparticles with a diameter of 2.8 nm, Ag particles of 3.0 nm and Pd particles of 5.0 nm, while spheres smaller than 2 nm are usually considered as non-metallic. 55,56 Recent studies on atom-precise nanoclusters 57,58 gave a detailed look on this transition; others show that the core electronics can be affected by the surface chemistry and even the solvent. 59,60 However, calculations and the lacking Korringa relationship of spin-lattice relaxation and temperature indicate that the observed shis of the ligand signals cannot be attributed to a Knight-shi type mechanism such as in metals.…”

“…59,60 However, calculations and the lacking Korringa relationship of spin-lattice relaxation and temperature indicate that the observed shis of the ligand signals cannot be attributed to a Knight-shi type mechanism such as in metals. 56,61,62 Nevertheless, the increase of the paramagnetic contribution to the chemical shi has been assigned to the electronic properties of the metal particles. 63,64 The broadening of the resonance lines of nuclei close to the surface and its particle size-dependence are commonly understood as a result of the restricted mobility of the nanoparticle and the increasing heterogeneity on the particle surface, i.e.…”

“…59,60 However, calculations and the lacking Korringa relationship of spin-lattice relaxation and temperature indicate that the observed shifts of the ligand signals cannot be attributed to a Knight-shift type mechanism such as in metals. 56,61,62 Nevertheless, the increase of the paramagnetic contribution to the chemical shift has been assigned to the electronic properties of the metal particles. 63,64…”

Breakdown of Kubo relation in Pt-Cu nanoparticles

“…Even though there has been much research on nanoparticles [11][12][13][14][15][16][17], it is still challenging to identify the QSE. This is because the surface effect, different from the bulk behavior, is similar to that expected by the QSE.…”