gold for plasmotics by tom heinrich. why is gold so special ?
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
www.ww.tu-freiberg.de/mk/Dokumente/.../Vorlesung15.ppt
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 !
http://www.businessinsider.com/biography-of-albert-einstein-2013-1
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
http://upload.wikimedia.org/wikipedia/commons/4/4d/Electrona_in_crystallo_fluentia.svg
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 !
http://www.vanillabanking.de/wp-content/uploads/2012/10/goldbarren-gold-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
http://www.sigmaaldrich.com/content/dam/sigma-aldrich/materials-science/nanomaterials/gold-nanostructures/figure-1.jpg
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
All good things come to an end ...
And so
Fin
My feelings about all of this.