Thank you, Mr Chairman. First of all, grateful to the organizers for this chance to present

our research here. I work for Professor Francisco's Strategy in his laboratory, rather interdisciplinary

so today I'm presenting to you the two techniques I put together to study gold nanoparticles in

his group. So in our group, gold nanoparticles composed of a metallic core and covered by a

ligand shell. Actually the ligand shell is the heart of the nanoparticles. It dictates how the

nanoparticles interact with themselves and with the surrounding. And the ligand shell can be

modulated by the chemistry of the components and the composition of the components. So for a while

we have been focusing on understanding the spatial distribution of the molecules of the

component in the ligand shell and correlated with their bio-interfaces property and surfaces

Only during the pandemic we lacked a lot of access to core facilities and synchro labs and

everything that we asked the question why don't we study colloidal chemistry or colloidal

interaction of the nanoparticles. In the colloidal interaction the particles simply described,

if you put it simplistically, described by DLVL theory which tells us that the total interaction

energy is composed of is a summation of two parts van der Waals and the electrostatic parts. Now if

we looked into literature there are plenty of ways to look at interaction of nanoparticle in

general and gold nanoparticle in particular. This is not a comprehensive list but you can see that

the main two thermodynamic parameters they studied are the second V-ray coefficient and the two

interaction potential. Now one prominent or one very feature that gave us difficulty is that gold

nanoparticle absorbs strongly in quite a broad range of UVV spectral range. So to deal with that

we need to study their interaction, we need to put them closer to feel more interaction among them

and then we need to deal with their contraption. So the first one I designed is to revise the very

old techniques for sedimentation equilibrium and the second one is a cryogenic anitrombography

and today I'm telling you what information we can obtain from these two techniques. So regarding the

first one now this is not new from the contraption profile at equilibrium we can convert it into

osmotic pressure and we can display osmotic pressure as a function of particle density. So

anything any function that deviates from the van't Hoff's law which tells us that osmotic pressure

is a linear function of the particle contraption the deviation can be used to extract second V-ray

coefficient. As I mentioned obviously we cannot use the commercial centerpieces for our experiments

then we used an old trick that developed in 1972 and it was brought back by Su Fang Shu

a PhD from conference lab so we inherited this from his lab and he's super good and taught me

how to run this. Now his trick is to replace this one with the plastic gasket and those people who

buy centerpieces from Nanolytics or aluminum centerpieces from Beckman they use this every day so we

simply replace this one with one of them and the operation the whole setup is very simple.

You put one window down to the cell housing and then put the gasket on top and one side you put

your sample the other side you put your buffer here for demonstration because the gold has very

strong color I just put them on two sides for demonstration and then you cap the whole thing

with the top windows the all the components here are loosely attached to each other you have to

slide them down the cell housing all together and once successful you can obtain the two droplets

on the two sides of the gasket and once you turn on the centrifuge you will get the capillary cells

with very thin path length in our lab we use it about 80 micrometers thick. Now Su Fang Shu

optimized the whole operation him and me we can operate it at a volume about 1.2 micro liters of

our sample and the problem is we cannot convince even any member of the group to try this even at

one sample when we add additive to gold nanoparticle solution and because the viscosity is reduced

it's spread everywhere so the whole afternoon Su Fang and I took turn to assemble one cell so

it was really really bad experience and most of the time you see that once it fails the second

time is harder because the hydration layer on the window will keep spreading your sample so it's

pretty disappointing if you keep trying and trying and get worse so in general

in our lab in our hands only we can claim there are several issues with this there's low flexibility

to change the column length and to to deal with different kinds of solution of gold nanoparticle

obviously ethanol, methanol forget about them and of course with that we have very low productivity