Presentation on theme: "Gold for Plasmotics By Tom Heinrich. Why is gold so special ?"— Presentation transcript:
Gold for Plasmotics By Tom Heinrich
Why is gold so special ?
More facts about gold metal bonding Cubic-face-centered (111) lattice constant a~0,4 nm electron-dense n~5,98 E 28 m^(-3) [Xe] 4f->14 5d->10 6s->1 mean free path lamda = 42nm
Which elements do you use normaly for Nanopartikels ? The biggest manufacter produces nanoparticels out of nobel / royal metals. - Gold Nanoparticles - Silver Nanoparticles - Copper nanoparticles - Platinum and Palladium nanoparticles.
What makes a metal nobel ?.... are metals that are particularly resistant to corrosion. Better solution for us : nobel metal = copper, silver, gold, completely filled d-bands no contribute to the conductivity and reactivity
Let us have a closer look at copper, silver and gold. The 3 metals withe the most distinctive shining.
How could it be that silver and gold have neary the same atomic radius ? Remember gold have 32 more protons than silver !
Sire pleace, the answer is : Relativistic quantum effect in chemistry
What is the Relativistic quantum effect ? Properties of heavy atoms s-orbital electros have nearly speed of light mass growth --> contraction of the s orbitals s-electrons shild the nuclear charge the energy levels of the other orbitals is lifted up
What does this mean for us ? Valence and conductor band approaching easier to stimulate elektros from d to s aka "Interbandanregung" for gold start at 520 nm (~ 2,38 eV) nearly free electrons in 6sp orbital
Band-stucture of Gold
Dielectric function Model of Drude-Sommerfeld electrons = findependent, point-like and effectively- free accelerate by external electric field decelerate Collisions with metal ions Г = T^( -1) with T = time between two hits --> Variancefactor --> only effectively-free electrons g
OK, but now seriosly why do the most of physicy use gold for thier experiments and not silver or copper ? Ask yourself with which spoon do you eat your "sunday-morning-egg" copper, silver or gold ?
Problem : We were talking about Bluks ! bar.jpg
Solution : let´s shrink to nanopartikel Über neue Synthesewege für ultrakleine, fluoreszente Gold-Nanopartikel und deren Einbau in Materialien by Andre Schäfer
Effects of shrinking to nanoscale Bigger surface by a minimum of volumina -> surface-energy lifted up -> other wavelength of the surface plasmos -> other absorbation of light discrete energy levels excited electron gas -> aktive chemical Gold nanostructures: engineering their plasmonic properties for biomedical applications
Influence of the surface
Where is the use ? Yesterday Coulering "Glas" Today Medicin, marking, Tomorrow Next generation of super-computers
Contrast enhancement for optical imaging Spatially resolved spectra biological sample(Phantom) Hauptquelle Gold nanostructures: engineering their plasmonic properties for biomedical applications
Contrast enhancement for optical imaging Gold nanostructures: engineering their plasmonic properties for biomedical applications