Bleu

vignette|Le ciel et la mer dans diverses nuances de bleu. Le bleu est un champ chromatique, regroupant les teintes rappelant celles du ciel et de la mer par temps clair. C'est aujourd'hui la couleur la plus appréciée d'un grand nombre de personnes. Colorimétrie et perception des couleurs Champ chromatique bleu Le champ chromatique « bleu » comprend de nombreuses nuances soit saturées, comme le bleu outremer, soit pâles comme le bleu ciel ou foncées comme le bleu nuit. Il s'étend des bleu-verts ou turquoise aux bleus violacés. Les longueurs d'onde dominantes des lumières bleues s'étendent de environ ; la norme AFNOR X08-010 « Classification méthodique générale des couleurs » (annulée le 30 août 2014) fixait ces limites de , et de en incluant les bleu-violet et les bleu-vert. Au contraire des rouges qui deviennent roses, les couleurs les plus lavées de blanc s'appellent toujours bleu, jusqu'à la limite avec les gris. La lumière monochromatique centrale du cham

Manganese doped ZnS nanoparticles

Yvonne Axmann

Nanostructured materials can be defined as those materials whose structural elements - clusters, crystallites or molecules - have dimensions in the 1-100 nm range. The explosion in both academic and industrial interest over the past 20 years arises from the remarkable variations in fundamental electrical, optical and magnetic properties that occur as one progresses from an "infinitely extended" solid to a particle of material consisting of a countable number of atoms. In this work the attention was laid on the optical properties of Mn2+ doped ZnS nanoparticles with respect to a possible application as bio sensor in medical and biological analytics. A synthesis for this type of particles has been developed and the nanocrystals obtained have been investigated in terms of their composition, particle size and optical properties. The particles synthesized were stabilized with the amino acid L-cysteine and showed the typical ZnS:Mn emission spectrum with its orange emission due to the 4T1 –> 6A1 transition within the d-orbitals of the Mn2+ at 585 nm and its blue emission due to recombination over the ZnS band gap from shallow electron traps at 380 nm. The onset of the absorption was blue shifted from 340 nm (bulk) to 310 nm, indicating a quantum size effect. The particle sizes and particle size distributions were determined with methods such as transmission electron microscopy, photon correlation spectroscopy, analytical ultra centrifugation and field flow fractionation. The particle size has also been calculated from the shift in the band gap with the help of the effective mass approximation. The limits of the applied techniques are discussed and the particle size distribution determined to go from 3-20 nm with a first maximum at about 5 nm and a second maximum at about 17 nm. The particles' luminescence quantum yields have been determined between 1.5-2 %. They could be enhanced by a factor of three by coating the particles with a SiO2 shell. The quantum yields showed a strong dependence on the dispersion concentration and Mn2+ content. These effects have been investigated with quantum yield measurements at different temperatures and Mn2+ contents, and lifetime measurements. The lifetime measurements showed decay times in the ns region for the blue and in the μs-ms region for the orange emission, indicating a florescence mechanism for the ZnS and a phosphorescence mechanism for the Mn2+ radiation.

EPFL2004

Full Color Generation Using Silver Tandem Nanodisks

Olivier Martin, Christian Santschi, Xiaolong Wang, Hao Wang, Chen Yan, Jingwen Zhang, Hua Zhao

Plasmonic effects associated with metallic nanostructures have been widely studied for color generation. It became apparent that highly saturated and bright colors are hard to obtain, and very small nanostructures need to be fabricated. To address this issue, in this study, we employ metal−insulator−metal sandwich nanodisks that support enhanced in-phase electric dipole modes, which are blue- shifted with respect to a single metal disk. The blue shift enables the generation of short wavelength colors with larger nanostructures. The radiation modes hybridize with the Wood’s anomaly in periodic structures, creating narrow and high-resonance peaks in the reflection and deep valleys in the transmission spectra, thus producing vivid complementary colors in both cases. Full colors can be achieved by tuning the radius of the nanodisks and the periodicity of the arrays. Good agreement between simulations and experiments is demonstrated and analyzed in CIE1931, sRGB, and HSV color spaces. The presented method has potential for applications in imaging, data storage, ultra fine displays, and plasmon-based biosensors.

2017

Manganese doped ZnS nanoparticles

Yvonne Axmann

EPFL2004

Manganese doped ZnS nanoparticles

Full Color Generation Using Silver Tandem Nanodisks

Signalisation routière : recherche d’une base théorique des formes et des couleurs utilisées

Signalisation routière : recherche d’une base théorique des formes et des couleurs utilisées

Manganese doped ZnS nanoparticles

Full Color Generation Using Silver Tandem Nanodisks