Hello everyone and welcome to my talk.

I will start my talk with a brief introduction of our AUCs.

After that I will move on to the experimental results which are about the colloidal stability

of C-TAP functionalised superparamagnetic iron oxide nanoparticles in dependence of

the amount of adsorbed C-TAP as well as the agglomeration behaviour of nanoparticle mixtures

in dependence of the critical coagulation concentration of each nanoparticle type.

And in the end I will sum up the most important content.

So here you can see an overview of our AUCs.

We have three AUCs in our laboratory.

Two of them were self-constructed by our chemical engineers.

One of them works with a multi-wavelength extinction detector while the other one works

with a multi-wavelength emission detector.

The third one is commercially available from Beckmann-Colter.

It works with a single-wavelength extinction detector and an interference detector.

And we also have our AUCs, the LUMI-sizes, which work with a transmission detector.

And now let's come to the C-TAP functionalised spions.

Yeah, what's so special about spions?

They have widespread applications like in the fields of hypothermia therapy, diagnostic

biosensing, magnetic imaging techniques, water purification, signal carriers for magnetic

identification purposes and so on and so forth.

And this type of nanoparticles can be studied by MPS, the magnetic particle spectroscopy.

It is a fast and easy to use characterisation method to determine surface functionalities

of typically dark magnetic materials.

And by MPS, the changes in the magnetic interactions of spions can be resolved within seconds at

ambient conditions in dried or liquid samples.

And in our particular case, the MPS was used to study the different agglomeration degrees

and with this colloidal stability, which defines their magnetic properties.

And furthermore, the different agglomeration behaviours were studied by AUC and CryoTEM.

So here in the picture, you can already gain an impression about the different agglomeration

states of spions in dependence on the different amounts of added C-TAP.

And we can distinguish between dispersed spions, large agglomerates, medium agglomerates and

small agglomerates.

So initially, the spions are functionalised with citric acid.

They have a strong negative C-TAP potential and are mainly single individualised in water.

By a small addition of C-TAP, the positively charged head group of C-TAP interacts with

the negatively charged surface of the spions, where the apolar moiety points outwards to

the water phase and induces agglomeration due to this hydrophilic hydrophobic interface.

By further addition of C-TAP, the large agglomerates transformed to medium agglomerates.

Since a second layer of C-TAP was formed, various polar moiety points now outwards to

the water phase, various lipophilic moiety incorporates into the first ligand shell and

this creates dispersibility in water.

And this stability, of course.

By further addition of C-TAP, the second layer gets fully covered and we can again decrease

the agglomerate sizes from medium agglomerates to small agglomerates.

And this hypothesis was furthermore evaluated by cryotemp measurements.

And here you can see the pictures of the cryotemp measurements.

So these are the dispersed spions.

The medium agglomerates, the small agglomerates, and in case of the large agglomerates, we

just observed very huge clusters of particles.

Yeah, in the next step, we also studied the reversibility of the agglomeration by MPS