The regulation of engineered nanoparticles requires a widely agreed definition of such particles. Nanoparticles are routinely defined as particles with sizes between about 1 and 100 nm that show properties that are not found in bulk samples of the same material. Here we argue that evidence for novel size-dependent properties alone, rather than particle size, should be the primary criterion in any definition of nanoparticles when making decisions about their regulation for environmental, health and safety reasons. We review the size-dependent properties of a variety of inorganic nanoparticles and find that particles larger than about 30 nm do not in general show properties that would require regulatory scrutiny beyond that required for their bulk counterparts.

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Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective

Three-dimensional high-resolution second-harmonic generation imaging of endogenous structural proteins in biological tissues.

The contribution that the technique of ferromagnetic resonance (FMR) has made to the understanding of the magnetic behaviour of ultrathin single films is reviewed. Experimental methods to measure FMR in situ in ultrahigh vacuum are presented. The temperature dependence of the magnetization, of the magnetic relaxation rate in the vicinity of the Curie temperature, and of the second- and fourth-order magnetic anisotropy energy (MAE) constants can be measured by FMR in situ for magnetic monolayers. Using the cases of Ni/Cu(001) and Gd/W(110) as examples, the role of the MAE for the quantitative description of temperature- and thickness-dependent reorientation transitions of the magnetization is discussed. Initial results for the anisotropy of the g-factor which is related to the anisotropy of the orbital moment (and the MAE) are presented.

https://iopscience.iop.org/article/10.1088/0034-4885/61/7/001/pdf

Ferromagnetic resonance of ultrathin metallic layers

Surface infrared spectroscopy

Physical and chemical properties of bimetallic surfaces

Calculation of chemisorption and absorption induced surface segregation

A theory for the size and structural dependence of the ionization and cohesive energy of transition-metal clusters

We calculate the nonlinear optical properties of small metallic spheres using electromagnetic theory and assuming that the local response of the conduction electrons is the same as for a plane surface. Electromagnetic Mie-resonances cause a strong increase of the second and higher harmonics in the reflected light. Detailed results are given for the second and third harmonic generation, its dependence on the frequency and polarization of the incident light, and on the cluster size. An enhancement of the second harmonic generation by a factor of about 5000 is obtained for small spherical metallic clusters. This is in good agreement with experiments on artificially roughened metal surfaces.

Theory of nonlinear optical properties of small metallic spheres

Electronic model for energies, relaxations and reconstruction trends at metal surfaces

La transformation ordre desordre peut etre du 1er ou du 2eme ordre selon la segregation de surface, la temperature de mise en desordre en surface pouvant etre superieure ou inferieure a la temperature de transition dans la masse

K.H. Bennemann

Papers

Calculation of chemisorption and absorption induced surface segregation

A theory for the size and structural dependence of the ionization and cohesive energy of transition-metal clusters

Theory of nonlinear optical properties of small metallic spheres

Electronic model for energies, relaxations and reconstruction trends at metal surfaces

Order-disorder transitions and segregation at the (100) surface of Cu-Au alloys