So, first of all, thank you so much for that nice introduction.

Welcome everybody to my presentation.

Today I have the pleasure to tell you a little bit about what we're doing at the Institute

of Particle Technology in the direction of characterization of nanoparticles.

So today I will be talking about anisotropic silver nanoparticles and how we're actually

– the different approaches which we do in order to observe the growth mechanism.

So I would like to start by explaining a little bit about silver nanoparticles.

So you might already know something about those.

These are actually very well known due to their antibacterial properties.

So actually silver nanoparticles release silver ions which actually annihilate bacteria.

Beyond that, they're also used for hydrogen production catalysis, for sensing, and also

they're actually put into solar cells' nanostructures in order to increase solar cell efficiency.

So today I will be talking a little bit about isotropic particles.

So isotropic particles for those of you who don't know.

These are particles, these are spherical particles in where wherever we look in any radial dimension

we will actually find all the same properties.

So unlike isotropic particles, we have anisotropic particles which even though they have a certain

degree of symmetry, their properties will depend on the radial direction which we are

looking at.

And so these particles are known and they have a really nice feature which actually

allows us to control their surface plasmon resonance.

So I will be abbreviating that shortly today simply as LSPR.

Even though to date many methods are known to synthesize these particles, all of them

based on seed-mediated growth, still the growth mechanism remains not fully understood.

And so what we want to do is we actually were able to freeze our reaction or quench it and

we studied the species which we obtained at different reaction times.

So I brought here already a picture of my samples where you can see how simply the color

is changing, so similar to the quantum dots, not because we are using a different material,

this is all silver, but simply because we are changing the sizes and the geometries

of the particles.

So the way that we synthesize these particles, we actually start with a syringe pump and

we introduce a solution which contains our precursor, in this case it's silver nitrate,

and at the same time we introduce another solution which contains sodium borohydrate

which is our reducing agent.

Furthermore we also add water peroxide which actually promotes anisotropic growth in order

to have our desired particles.

So what we do, we introduce them, like I said, simultaneously into a tea mixer and we take

then at each different reaction times different aliquots and we are able to freeze the reaction

by introducing stabilizing molecules, in this case 11-mercapto-undekanoic acid, so I will

be simply saying MOA, and then we investigate each of these individual aliquots.

So I think that it's not necessary today to go into details about analytical ultracentrification,

but I would like to mention that at our institute we have a multi-wavelength detector which

allows us to retrieve coupled sedimentation coefficients but also the spectral data.

And so please keep in mind too that we, so typically we convert from sedimentation coefficients

to particle size through the Stokes equation, but this is only valid of course for spherical

particles.

So we will see at the modifications which we do.

Alright so the first thing which we did was after freezing the particles or freezing the

reaction we wanted to study at individual species, at individual bodies or geometries

which we have in there.