We did and

now he's going to be telling
us about some of the work

that he so I think.

Thank you.
Seth for this nice introduction.

Many thanks also for
actually inviting me here.

It's been a nice visit so far and I have
to say in comparison to our own campus

that I was showing my very last slide
you have a very very beautiful campus.

That is very green so
enjoy this as long as you can.

Because ours looks a little different.

Thanks to everybody for coming in our
group we do a number of different things

we work on car bridge now no
structures we work on conducting

devices from or thin films of
Christensen films of organic molecules.

But the story I would like to share
with you today is one specific

work we have recently been doing
on the relational structure and

charge tech transport in
self-assembly organic nano Why is and

if I were not to give a talk
about how to research.

Write a fancy research proposal I probably
started this proposal by saying like you

know organic nano wires are going
to be important as novel types of

charge percolation paths for
example in organic solar cells and

the like but as you probably know better
than I do all the Thames to put it.

And as a tropically Grohl nano crystals or
or

nano Why is into devices actually helped
to make the performance worse not better.

So far.

And so

the way I see it is that it's more like we
need to understand better what happens.

In the interaction between materials and
light and in terms of carrier generation.

If the material.

Is confined to nano Skopec structure is
and I think that self-assembly organic

not of why US might help us in that regard
to develop a better understanding but even

for this more more fundamental question
I think we still have a long way to go.

Typically synthetic chemists like I am one

would call any one dimensionally extended
aggregate of a pike conjugated molecule

in organic not a way of whether it
actually conducts anything or not.

In the better cases like in this
relatively recent elegant example by talk

of our at least they undertake an effort

to determine the electronic
The electric properties of

a obtained from the molecule
substituted with altered peptides they

are reasonably similar to the molecules
I'm going to talk about today.

As you will see.

But even in this case you know so
in the end they make Nano but they measure

the connectivity of a bulk thin film
of microfiber so also the thickness

of these fibers is much larger than
the Nano was they were originally claimed.

It's been processed from water.

There are some strange misses in the I.V.
curves and

I think that it is fair to say
that this molecule conducts but

what is actually the Nano structure that
is responsible for conduction and what is

the charge here is species is actually
not well understood in this regard.

Things might be might be a little better
in the case of tropically grown crystals

or Also police.

Fibers however in that case.

I think that it is off to the structural
understanding that is still a bit and so

what I hope to be able to show you
two days that we have a very simple

molecular design.

So I'm not an overdesigned molecule
that forms what we call a well defined.

Fibro swear by with well defined I mean
none of us with a molecular defined

diameter that have a single step of the
pie conjugated molecules at their core and

at the same time the core molecules
interact very strongly and

as a result we see for the first time
the full to use generational surprisingly

long lived polar on like charge carriers
in the absence of a dope and and

we can show that these charts
carers are actually responsible for

the microscopic connectivity
that these not a far will show.

So this is kind of the outline
of the story I would like

to present to you today.

And of course we first have to talk a
little bit about the molecular parameters

for for the self-assembly process and
also the synthesis.

So time does not permit me to
explain the basic concept of

the self-assembly process that
we're making use of in detail but

I can show you at least some
some general ideas behind it.

So here you have an audio peptide that is
a short article peptide that is linked

to a hydrophobic polymer So
it is known that these short all

go peptides like to align with one
another parallel to one another and

in this way they form tape like
structures such as shown here or

here however due to the combination of the
only the peptides molecular chorale A-T.

and the terminal polymer attachment
the resulting tapes actually

twist up into a healing superstructure and
this is what actually limits.

Let's really limits
the self-assembly process and

by by by means that I cannot explain
in detail today you can actually die

in whether you want to make
single tape structures or

tape Nama structures and so what we would
like to make use of is this kind of

single tape not a structure
in order to obtain our or

well defined not to fire drills
from pi conjugated molecules and

again something that I cannot explain
in detail the first class of molecules

we investigated were actually
DI acetylene as kind of.

Model compounds for pi conjugated systems.

Why did we choose Dyesebel
because now we could investigate

the Nano structure formation.

Not only by if any region which gives you
the Nano scope morphology just visually

not only by our spectroscopy which gives
you a good idea of how the other peptides

interact with their neighbors via an age
O.C. type hydrogen bonding we could

in addition also use the topo chemical
diacetyl in polymerization shown here.

As an additional tool to get an idea
about the internal structure and

the degree of alter inside because
this polarization this U.V.

induced polarization only works if
the dye settlings are present in a highly

altered and Crystal in one to at least
one dimensional Crystal in a ray

otherwise otherwise the polarization fails
and so this if the polarization works and

this tells you that the internal structure
is the same Ask medically shown here.

And so from the combination of these three
techniques and if and I are spectroscopy

in solution and diacetyl in
polymerization we determine for

a matrix of molecules where we vary both
the length of the polymer chains and

the length of the little peptide segments.

We determined what are the molecular
parameters needed in order to

arrive at a reliable self-assembly into
he little fiber like structure is the way

we wanted it and as you can see here it's
actually surprisingly small window of

polymer degrees of polarizations and

all of the peptide lengths that
are useful in that regard.

So this this serves to then understand
the molecular parameters and

then transfer them onto the actual pipe
conjugated molecules all the Paralympics

emits that we wanted to investigate
before it come to that.

However I'll show you.

I'll share with you one little detail that
I don't talk about very often because

time on a call on a conference talk

typically doesn't permit to talk about
synthesis which is a bit sad big.

I mean realistically speaking my Ph D.

students spend probably more than
half of that time doing synthesis but

then it is rarely talked about the one
thing I would like to share with

you here is we didn't reinvent the wheel
in terms of chemistry we do standard.

Suzuki coupling still
a couplings we do with N.B.S.

and all Center chemistry we didn't
reinvent any new chemistry.

Why ever we found a very nice way
to overcome one of the drawbacks

that those of you in the audience
working synthetically foreshore know and

that is the loss of the ability of or
intermediates and

products they're designed to aggregate or
crystalized by pipe by stacking and

so at the same time that makes them
very little soluble and so my Ph D.

student who was working on the project
initially had the idea to use a new

very bulky polar chlorinated
protecting group derived from color and

acid and hydride So there is literally
almost no chemistry with this

with this compound it's been
used as a flame retardant.

It's produced in kilotons it's been used
as a flame retardant polymer materials but

it's not being made use of in terms of
chemistry a lot and so we use the chlorine

to acid and hide right as both an I
might protecting group for a terminal

I mean an active as the protecting group
or a terminal car books are like acid and

as you can see because now all
products are crystal in and

at the same time they're highly soluble in
organic solvents I'll comment on that on

the next slide as well we
could perform in the in our

regularly equipped since of these since
this on the multi doesn't gram scale even

towards the final compounds and we also
made use of the same style of protecting

group for the Paralympics in minutes which
we then could functionalize And so that

gave us a box of all the good side feen
and personally besom a diet means and I.

Yes it's for
further functionally ization And

as I said as I said you know all these
compounds are nicely Crystal and

actually they typically precipitate
from the reactor mixer.

Principle cooling after the reaction.

And we believe that the what is
responsible for the high solubility can

be combined with high Crystal linearity
is just the packing of the molecules in

the crystal and state that is somehow
enforced by these color and acid

side groups and groups because
they're much more bulky then

the typical pipe pipe
conjugated systems and so

you see that the system actually
resorts to a layout packing.

Which in the case of on symmetric
molecules isn't interested

of molecules coming from both sides but
the next layer is held together with

this one only by Helen Helen bonds
which are easily addressed by a pole

by a reasonably polar organic solve and
so they crystallize nicely but

at the same time they can be easily
dissolved and then the symmetric compounds

as you see here of course into detail you
did packing in this case is not possible.

And so some of the final
compounds actually give up

on the pipe by stacking completely
not the ones I've shown here.

Others like this one.

You don't see in this projection have
Sullivan channel Solvay channels going

through the crystal So I believe that
this is one other element responsible for

the high solubility all these components.

And so
as you see in some cases typical pipe by

stacking either between the rings of the
holding softens or between the rains and

the six in the middle residue is of
the chlorinated as said residue you.

But in most cases actually we see other
types of interactions that are dominant

for example as I said chlorine chlorine
interactions between the layers or

oxygen interactions.

Within the Laos and so I think that
this is kind of just a trick that

made our our whole synthetic pathway
very very convenient to pursue

then we take these building blocks for
example an acid and

just link it in a final peptide
coupling step to a polar

peptide that we did protected
on the mean side and we're done.

And so as as you can see here we took that
molecularly the molecular parameters we

previously determined transferred
them on this molecule.

We still made a series of different
molecules with differently long all

the peptide segments just to see what
would be the effect on the self-assembly.

And so after we had the molecular
than hands and after we had

kind of a tool chest of molecules that
we thought would be appropriate for

self-assembly we investigated
the formation of nano five rolls in

solution so the idea is just just to
repeat that we would like to take.

These molecules dissolve them
in an appropriate solvent

moderately polar organic solvent for three
to promote strong hydrogen bonding and

the molecules would ideally line
up schematically shown here with

aggregation strongly promoted by hydrogen
bonding between the peptides but

at the same time the little twisting

letter really limiting the aggregation so
that we don't see bundles and

from a variety of different
characterization techniques that.

Again time does not allow
me to go into in detail but

I would be very happy to
answer questions about it.

For example solution
phase I our spectroscopy

we could see that as soon as the legal
peptide segment was long enough

which coincided with our previous
investigations on the diacetyl.

We obtain a might a vibration which
is the N.H. stretching vibration or

also in a mud one by abrasion which
is the seal stretching vibration.

That is.
Very sharp and can be interpreted as

a highly ordered peril like aggregation
the way we wanted it to and if you do this

I are spectroscopy in solution temperature
dependent you see that there isn't

temperature in the range of like
one hundred degrees centigrade.

So the self-assembly process is
actually formally reversible and

can be performed under some of
dynamic conditions and solution.

What do you see in the airframe images
that you then know pain as you take

a solution and deposit a sample on it on
a substrate is that if the peptide seconds

are too short so that I.R. spectroscopy
shows its non aggregated molecules

you obtain a drop like features so
no defined aggregates of any sort.

But as soon as the illegal peptide segment
is long enough you will pertain very well

defined nano fiber lower structures
whereby well defined means all of

them have the same diameter and in those
cases where we can actually distinguish a.

All of them have the same
kind of morphology as well.

And this puts this even at
higher concentration so

what happens at higher concentrations
is you still do not form bundles.

You may see that a line
close to one another.

OK now by weak penetration
of their poem or shells.

However mainly your pain
the same kind of five rules

that are just crossing each other and
form a random spaghetti like network.

If you take a closer look
at the if I mean reduce and

vary a little bit the topping conditions.

You see that actually
the rules have a rigid

core with a height on the older three
to five not a meters that you can also

distinguish very nicely in the face
images and these three to five

nanometers correspond very well to
the all good peptide all good thought.

If you know all the peptide part of
the molecule where asked the soft material

seems to be placed along
the flanks of the.

Five rules and
we investigated all of this a little bit

more closely with the help of
a collaborator in chemists in Germany who

invented something he calls a multiset
point intermittent context mold.

So music.

To have a more catchy name for it and so
this is always used to obtain height and

face information and phase information
a different set points in a single

measurement run so that you're not so
much prone to two imaging artifacts and

what you can see in these images is
that the height image shows you periodic

corrugations which can be attributed
to the list of the of the five

bills in this case the contrast
doesn't show very much.

But the hard soft contrast shows you
that mainly the soft material shown

in dark here is actually placed
along the flanks of the rails and

I'll show you two more such images
just to give you a complete

kind of overview that this is
kind of a universal scheme.

So here we looked at a molecule that
had a qualifier phenotype peptide and

hydrogenated poly I supreme as
polymer segment we can change.

Most of these parameters so
we can go to a tetra peptide we can

exchange the polymer for poly as a
beautifully in again you can see very well

defined fi rules in this case even
the regular the conventional if any

shows nice helicity same morphology for
all.

Five rows and the music mold
shows height corrugations and

again soft material placed
along the edges and

we can finally even exchange
the core from a donor type molecule

to an accepted type of molecule and
again conventional F. I mean business.

Nicely defined fire drills again
with the heel equal morphology and

the music mold images in this case
again show what height corrugations And

in this case the how to fill it.

How to fall back image shows two lines
running diagonal where the bumps.

And so one can tentatively attribute
this to the hydrophilic hydrophobic

hydrophilic contrasts from the peptide
apparently invisible peptide segment.

Schematically shown here so

that you obtain these diagonal stripes and
to conclude this story.

This is really a universal power universal
method to obtain not in all cases

are they as well defined as I've shown you
we need to work on that these are very

fresh results from a new Ph D. student
in my group who sent me the results.

Two days ago.

So in this case we exchanged the core for

certain other core elements
which we want to use to

tune the electronic properties of the Nano
Y.O.O.'s But you see that a little bit.

This will also influence how these guys
self assemble So we need to play a little

bit more with like thermal and
the link in solution and the actual

preparation of the solutions in order to
obtain better defined rules in this case.

Good.

So I hope that so far I've been able to
demonstrate that we have a very nice and

universal method pain

not a fibro from pi conjugated molecules
with a defined superstructure formation.

We understood.

However a little bit better.

What the internal structure is
because we were able to prepare

hierarchically structure microfiber is
from the Nano fibers that then allowed us

to perform structural
characterization a little bit more so

in order to obtain the micro fibers.

We just took a solution
containing the Nano five rules.

And injected them from a solvent into a
non solvent by pulling out the needle here

you just see the tip of the needle of
the syringe by just pulling it out from

the non solvent your pain and hair like
object which is centimeters in length and

has a diameter on the order of a few
micro meters just just like a hair and.

At the same time we were
able to tune to tailor

the diameter of these micro fibers
just by using differently think.

So for example we could dial in or
here you can see it better.

We could dial in roughly six
micro meter ten micro meter or

eighteen micro meter
diameter microfiber us and

these were highly lined or
internally highly aligned

species as you can see from polarized
optical microscopy in diagonal position or

in an extinction position using
a reservation plate told us that the.

The the fast.

The.

Fast.

What is a reflection.

Is in fiber direction which
by analogy to the literature

tells you that the only
good peptide segments.

So the side groups are actually lining
up vertical to the fiber direction and

accordingly polarized I.R.
microscopy shown here for

the a mite to bend they might one band
that are already referred to earlier so

the C O O stretching vibration and the any
stretching vibration shows a systematic

variation depending on the angle of
the polarizer of the I.R. microscope and

again this tells you that
because the C.E.O. is

stretching vibration is smallest in ninety
degree position this tells you that again.

They only go to the car when the groups
are parallel to the final direction

the replies are perfect.

Lots of it will come to that come
back to that in a in a second.

S. S.C.M. imaging off the microfiber shows
that they have some sort of a hierarchical

structure with like logic bundles that
are composed of smaller bundles and

if you zoom into these smaller bundles so
shown again here by A.F.M.

emerging You can see that actually
these smaller bundles comes.

Highly aligned array
of the Nano five rules

that we have processed from from solution
and so it is not a surprise that we get

data from from polarized optical
microscopy and I are microscopy five or

more importantly these microfiber and
then allowed us to do five X.

ray and you can see in the small and
wide angle X. ray region.

Mainly for peaks the least important
one is the biggest one which is just

the near all or peak of the butyl in this
case but then you see a six nanometer

peak which corresponds to the diameter
of the closely packed Nonna five rolls.

You see four point six six unstrung
peak which is the typical or

a little smaller I have
to say than the typical.

Into molecular distance in
like systems of peptides and

you see the three point four on stream
peak that one can assign to the stocking

inside the Nano five Well here you see
the distributions of these four peaks.

Sure enough you see that that the knot
of fibers are aligned parallel to

the microfiber direction as are the
polymer chains that are kind of sheared

along the direction when
we prepare the microfiber

it's interesting that you then the spacing

is oriented at ninety degrees and
two hundred seventy degrees so

again showing that all the peptides
are actually oriented perpendicular to

the fiber of the reaction and the pipe
by stacking distance has an immutable

angle at forty eight or
with a corner equal distribution.

Of the Paralympics and it's in this case

with an angle relative to the fiber
axis of around forty eight degrees.

And this is trigonometric Lee very

consistent with picture
that looks like this.

So if you have a stacking distance
of four point six on strong.

Peptides an angle of the parallel of forty
eight degrees with a microfiber axis.

Then the second distance that you derive
from that three going to metric least

three point four on storms in the case of
the three point five on streams and so

that is very well consistent with the data
we actually obtained from the X. rays.

OK now what is remarkable about
it is actually how close it is so

a three point four on surrounds you.

All you are you do find imperiling
besom in single crystals.

But it's actually already very close
to the distance and graphite and

three point five on streams for

the other is much closer than what
is typically observed in such as.

It is it is as there are a few
examples of similarly tight.

Stacked species in
the literature like certain.

Almost for a short to look at most of the
in that have shown as a similar distance.

So overall I hope that I've
been able to convince you.

So far that we have a very simple
molecular molecular design for

molecules that then form not a fiber by
a combination of pipe by stacking and

hydrogen bonding and
the way we've built these smaller Kulas

including a small flexible spacer
between the pipe conjugated second and

the hydrogen bomb and second actually
allow these two super molecular

interactions to enhance one another
rather than impede one another.

Despite the fact that they have
two very different characteristics

spacings a four point six and
three point five on Strom's and

because of that because of that
synergistic enhancement of pipe by

stacking with hydrogen bonding
all the electoral substitutions.

We all deserve very tight pipe
by stacking which presume.

Or so we hope in the Nano fiber also that
we've been characterized because we were

able to make these hierarchically
structured microfiber.

As I would like to show you.

Demonstrates you in the following this
tight pipe by stacking has profound

consequences for the question of
interaction of the not a why us with light

and the question of child care or
generation.

So let's first take a look at
the optical spectra of our

molecules both the aggregated
once in solution and

non aggregated molecules that I sold so
with all the knowledge of peptide that I

will always use a as a reference in
the following slides as you can see here

the non aggregated molecule have
you visibly option peak with

a maximum at around four hundred meters as
it is typical for molecularly disperse.

The aggregated molecule however has a peak
dramatically blueshifted much narrower and

with a certain let's say fine structure
that we are now pretty sure is

not a vibrant fine structure but results
from from something else at the same time

the see the spectra of the not aggregated
molecules show no city activity.

So the molecular karate of the molecules
is not sufficient to induce a CD activity

in our case but the aggregated
molecules have a very well defined

CD band by signal band with a zero
crossing at the position of

absorption maximum and positive cottony
fact that one would describe two

strongly interacting chorus stacked
in a P.C. legal or right handed.

He little fashion.

I'll skip over the fluorescence data for
now but

I would like to point out
that we did extensive or

the structural information we had from X.

ray allowed us to perform
well that the simulation.

In the group of skull number who then took
snapshots of the molecular dynamics and

simulations that she obtained and
perform D.F.T.

computations of the optical spectra.

And the optical spectra she obtained
in this case looked like this.

So we could reproduce the three bands
that we observe in the experimental

spectra which is weak
rich if that band name

a main band that is blue shifted
compared to the molar absorption and

also a third peak in the middle
that we named him on a more like.

Transition So what that means is that
the fact that we see these three bands is

a result of the the specific geometry of
the of the not a far as we obtain them.

The fact that we still see
a shoulder at the position of the or

roughly at the position of the monomer
doesn't mean that there is an equilibrium

with monomers with non aggregated species.

It's more like there is temporal
vibration like this all in the stack of

the in the stack of thought.

That gives rise to this band but
mainly we see an H.

type aggregate which results in the blue
shift combined with weakly allowed J.

type transition due to the specifics of
the geometry inside or not of five rows.

More specifically if you
look at the positions

of this blue shifted band and the richest
it down by means of fifty computations.

And you perform a scan of of how
they how the two different bands so

here is the blue shifted component use the
rich if the components vary as a function

of the displacement of two
neighboring all the relative to one

another along their long axis X.
their short axis Y..

So in these directions and
also the Z. direction so

the actual spacing you see that
we are in or we can only read.

Produced the experimental spectra
very well if we assume that the Z.

direction has a spacing on the order of
three point five to three point six So

this coincides very well with our X.
ray determinations and

with a long it will displacement
on the order of two and a half.

That's roughly one thousand feeling and

lateral displacement that is pretty
much nonexistent that is negligible.

So we haven't.

In terms of lateral displacement and

almost call facial stacking with a bit
off longer too and all of this placement

at a very tight pipe by sucking distance
of three point five on streams.

As a result preliminary trends in
absorption spectroscopy data suggests that

there must be additional
pathway all through the case.

So here you see molecule versus
an aggregated molecule and

you see that that after
the initial Taishan the peak

decays relatively quickly into
what is a triplet state of

the molecules in the aggregated state the
spectra look different and we don't know

what is what is the reason for for
that in detail but more importantly

the exit Taishan decay is much faster
in the case of one as compared to two.

And secondly the intensity of the final
triplet state species that is formed decay

is much smaller please consider that the
axes are actually different in this case.

So how we interpret that is that there
must be after initial expectations

an additional pathway for decay.

We could so far exclude that it's
the elation or energy transfer.

So we believe it's charge transfer
the nature of which we're not

sure entirely sure as of yet but I I can I
will comment on that a little bit more in.

At a later point.

Now importantly as you as I
already mentioned from the I.R.

spectroscopy the aggregation in

solution is thermally reversible and
this you also see in the you review is and

the CD spectra So you take a solution of
containing the knot of fire rules and

you heat the solution and you convert
the aggregate the age aggregate

peak into the molecular peak and you
cool the solution again and you go back.

So everything is nice and
stormily reversible.

But what we noticed at the same time
is that in addition to this main U.V.

visible option.

We see two additional bands of relatively
high intensity compared to any other

system in the literature.

So this is about one tenth of
the height of the main optical

absorption in the red and
near infrared region and

these peaks are actually typical for a
quarter thought I feel radical Catalin And

as you can see these peaks actually
completely this disappear as we heat

the solution and
the aggregate not of five rolls and

as we cool the solutions and Raef
reassemble the Nano five rolls these peaks

slowly come back up even in the dark even
under a careful exclusion of oxygen.

As you can see from that space from
those series of spectral ready.

The disassembled molecules do not show
this the not aggregated molecules do not

show this nor do I know of any other
example in the literature where a quarter

siphon has shown as a spontaneous quote
unquote radical could i information

in the absence of an oxidant
sure enough these

bands are the result of
a radical cut ion So

if we take our original solution we
had a reduction we can quench them.

If we had an accident we can reestablish
them and we all saw the same

bands in solid films of our material
that are have to and carefully.

Kept on there are gone.

We have then investigated.

The what could be the generation
we excluded oxygen we.

We tried our best to exclude other
inadvertently present accidents and we

then found that actually these peaks are
generated in a light induced process so

as you take a solution that
has been just cooled so

that the not a fire will form but
not given a lot of time yet.

Then you see and
you expose it to white light and

you see that these peaks actually
drastically increase in intensity.

Whereas they increase much much slower
if you keep it in the dark as as well

as possible.

If you then as you say then
switch off the white light

intensity of the singles De Kaser again.

But as you can see here
the decay is actually very slow.

So this is a time frame
on the order of one week

until it finally returns
to its final state.

So I think we can say we have
a surprisingly long lived

radical kid I only expect.

That old only probably due to
some follow up chemistry then and

then slowly disappears.

Sure enough if it's a radical cat
ion It should also show an E.S.R.

signal and it does.

And so whereas the not aggregated
molecule shown in black does not have

a signal our aggregated molecules
in the not of fog rolls show

a nice Yes our signal both in solution and
in solid films shown here with the gals

factor of two point zero zero twenty four
which is typical for a radical cat eye and

it's also close to the free electrons
frequency and a surprising density of

overall three point six times ten to
the sixteen per cubic centimeter.

Now if you consider the fact that
probably the polymer part and

the only good peptide
part are in Nokia's so

it's only the quarter that are responsible
for that radical can i information.

This actually translates
into a spin density.

On the order of ten to the nineteen
in the in the water siphon part

which is two to three hours.

Well actually three orders of
magnitude higher than what is also for

materials on or under similar conditions
again the yes our signal can be quenched

with a reduction it can be formed
adding an oxidant we tried to exclude

the role of the chlorinated solvent
by going to a method cycle hexane but

we also have the signal in
the solid film so we're pretty sure

it's actually an inherent feature and not
a result of some some oxidation process.

Not even involving
the chlorinated solvent.

As we did the E.S.R.
spectroscopy in solid films

temperature dependent you see
the original spectra here.

And as you plot the doubly integrated line

line as a function of temperature
which is a measure for

the power magnetic use are accessible
apartment attic susceptibility of

the system you obtain a plot
that looks like this.

So in a low temperature regime up to sixty
Kelvin wheels up one over to a relation

which is true can be
attributed to the behavior of

localized spin carrier so in this
case in this low temperature regime.

This means that we're actually
dealing with localized radical

the way an organic
chemist would draw them.

But then we switch to another regime that
looks like it's weakly thermally activated

and so this actually suggests that here
in this temperature regime the spin

carriers become mobile and consistent with
that picture a plot of the line width

as a function of temperature shows
a consistent decrease in line with

over the whole temperature range which
can be ascribed to motional narrowing.

Now as we plot our data.

According to different models that
assume localized charge carrier species.

For example variable range hopping
following what's the equation.

We'll take in typically
group relations but

we obtain at the same time physical
parameters that are parameters that

are physically impossible for
example in the case of not situation.

The localization length on the order
of microns which is just impossible.

So it just shows that this very
real range shopping model or

any other localised childcare model for

that matter is probably not a very
appropriate description in our case and

this can also be seen from the fact that
if you're doing the radius plot of our

data again we'll take a good relation
albeit over a relatively small range of

physical values that we obtain a an
activation energy which is six million

dollars which in this case I would say
it's not physically impossible but

it's actually very small compared
to typical police often materials

which is more on the order
of fifty million dollars or

higher probably even rather like two
hundred million dollars So we have a.

An only very weakly thermally
activated process and so

this is what what makes us believe that
we have a charge carrier mobility that is

on the on the border between localized For
example following a helping mechanism and

a very narrow band like
conduction mechanisms and

a similar kind of a similar borderline
case has recently been reported for

carbon nanotube networks where people
have similar data as as we did using

Anderson's model for emotional narrowing
combined with a whopping way function

which was then termed Wilson's model and
again if we fit we actually get a nice

fit the parameters we obtain you
are obtained different time frames out of

this data actually fits to the data
reported in the literature but

again we have a very low activation
energy that point sides pretty well.

With activation energy we observe from
the power magnetic susceptibility data.

So that is where we are what
we believe is happening.

And here we come back to the charge
transfer process is that

upon initial acceptation the excited
Alex Wellen is transferred.

Somewhere quote unquote To
me the most likely culprit.

Is the cardinal functions of the all
the peptides adjustment to the molecule.

That could be reduced to a Keep feel
like species or something like that and

we believe that what helps
us in this case is that

the have shown that between
the blue shifted and the rich if

the transitions there are two of
the transitions that are totally dark so

there is no probability for
returning to the ground state.

Once you enter these transitions and

we believe that there is some
way of funneling the excited.

The excited Alex on into one of those dark
states where they then have sufficient

time to do followup chemistry such as
a reduction in any case it's once again

universal process so it's true for
all donor molecules or for example here.

If I show you all three dollar
molecules I've shown you before.

Again they can be disassembled and
reassembled by simple heating

in solution like the molecules I've shown
you before and all three of them show.

Long lived polar on like species in
the in the near infrared region.

What is what is interesting to all see and

we don't understand the details
of the spectra at all.

I have to admit is that.

The different molecules show very
different properties in terms of

the broadness of the peak which would
if it's a polar on like level kind

of translate into
the broadness of the pole or

on like bands in the middle of the of
the material in the aggregated state.

Whereas others are very narrow but
about on the other hand very intense.

So I hope that we can exploit this.

How about How about accept are molecules
Well these do not spontaneously

form radical and ions because they would
be then Alex one from somewhere and

there is no reduction species anywhere
to be seen in these molecules.

However in this case as you can see here
this is a set up a cell we made for doing

and I are spectroscopy on thin films
where we can expose the vapors.

And as you can see of course
we can generate radical and

ions of of these molecules
by exposure to hydrazine and

if you then open the chamber
to where it goes back and so

I think we can exploit this although
I have to say that in this case we

haven't made the controlled experiment
with non aggregated molecules at all.

So so far everything is nice and
I would even say

remarkable and
we understand many things pretty well but

we don't understand one Dieter that
I would like to expose you to.

And this is if you go to the molecule that
is a Cairo where we replace that Alan

means that we typically use with
simple glycine the I.R. spectra

shows that the molecule more or less on
a local scale assembles in a similar way.

So we obtain a nice beat a sheet like
band of a highly all that aggregate.

The U.V. this absorption spectrum shows
the maximum advertently the same position.

So we seem to have H.

aggregates in this case as well but notice
the absence of any structure in this case

however in the absence of Karate the
molecule of course doesn't make five rows.

It makes more like films
the height of these

films corresponds to the the diameter
of the fibers we typically observe.

But we have the letter like a geisha
into these film like structures nicely

enough we see kind of a sergeant and
soldier effect.

So as we add ten percent or
thirty percent of the chiral molecule to

the system we go from these
mono they are like the.

Too undefined to actually produce
surprisingly well defined five rules but

what struck us is that if we
leave away the the the carle

component entirely We do not observe any
formation of the radical kid ions So

there is a top a logical effect that we
do not understand very well in play here.

It's not only important that the high
conjugated segments inside the Nano

fibers are closely packed which I hope
I've been able to convince you that they

are it's also important that
they are heal equally packed and

that somehow this core of the rules
is surrounded by something else.

It seems to me that it is like this if we
add ten percent of the chiral molecule

then we're back to a situation
where we can form.

The radical by exposure to white light and

the intensity of that peak actually scales
with the amount of chiral additive.

So far for childcare generation
in the last five minutes

I'll quickly show you our results for
four connectivity of the system so for

this we mainly build two point
devices where we have ep or

a TO GOLD contact on top of a very thin
film of a film of our nano fibro thier For

example showing the device with
a five micro meter channel length.

We try to build transistors and
they showed some connectivity but

they did not show a gate effect which
if I'm optimistic I can say well

if there are already all these charts
curious present in the in the system it's

probably not a surprise that we cannot use
the gate to induce charge care formation.

But we actually did not
close copy connectivity

as soon as the channelings
was five micro meters or

below which is nice in the sense that
it actually correlates to the length of

the average length of the micro fibers
which is on the order of microns.

So what it means to us is that actually.

Church transport is possible if a single
nano federal is contacted by the two

gold electrodes but it becomes impossible
if the charge has to help from one nano.

To another one.

The observed currents on the old are off
nominal and pair may seem small at

the beginning but
I need to tell you here that we actually

counted from the if any midges the number
of fiber between the electrodes and it's

roughly one hundred even if it were two or
three hundred it wouldn't really matter.

It translates into current densities
that are actually exceedingly high

inside the now in a while as on the order
of ten to the four M M pair per per square

centimeter and
then we could actually fit our data for

different devices with
different channel lengths with

one comprehensive model the faller nor
time model which assumes

contact resistance a limited injection
into an organic semiconductor.

And from the high voltage
branches we could estimate come

up with a lower estimate of the mobility
inside these quarter thought if the Nano

wires on the old zero zero point two
wealth centimeter square provokes

second which compares to some of the the
best values reported in the literature for

a quarter five hundred single crystals.

We also try to do the same with the
parallel systems except their system but

in this case I already showed you that

we did not observe a radical
i information spontaneously.

So I hear what you see the five
micro meter channel lengths device

you see an F.M. image of the channel

with a nod of foggles running here these
are the gold electrodes evaporated on top.

So in this case we indeed we observed

in the absence of hydrazine we
observed virtually no current at all.

So the scale here is a little small I'm
sorry for that is on the order of pass so

there is no current but as soon.

We expose the system to
to hide as in vapor.

We actually get decent current
voltage curves which in the case

of the five my community by seem
to level off at about at about

what is it ten not on pair for
twenty volts voltage

the two micro meter device shows an almost
contect Resistance three current but

in this case we have to work on this
experiment a little further because we're

not entirely sure that there is not gold
that is actually spanning the channel we

need to make sure that it isn't and
then finally with a parallel system.

We then also were finally successful
with building transistors in this case

we use commercially available
bottom gate bottom contact

transistors with into detail
source drain electrodes and

we just spin coded nano wire fill
a dense nano why a film on top and

we obtained a decent transistor
characteristics as you can

see here the output course the transfer
curve and the first lower estimate

of the mobility in the electron mobility
in this case inside these parallel.

Would be on the order of ten to
the negative three centimeters square Paul

the second which I find is a decent value
but again these are very fresh results

from the beginning of this week so
I hope that indeed I've

been able to make full circle
starting with synthesis and

the molecular parameters needed in order
to assemble molecules by a combination

of hydrogen bonding and pipe by stacking
so that you obtain where they find

with a defined with defined letter of
the mentions and more importantly a very

tight stacking of a single stock of
conjugated molecules at their core.

I hope I've been able to show you
that this is then responsible for

the unprecedented formation

of long lived radical kid ion charge
carriers in the absence of a dope and.

And that these can then be attributed or
that the microscopic connectivity

observed in these cases can be
attributed to those systems.

This is my last slide.

You may ask is this relevant or not to
be honest I don't know I think it's not

it's a study that elucidates
Church care or generation and

transport under nano scopic confinement
whether this is useful for devices

per say the Nano why us I mean I don't
know probably it's much too much work.

Probably there are too many parts in
the molecule that do not contribute to to

conduction However I would like to
show you one slide about another

project in our group that would
give rise to hold you talk.

I would like to show you that you
can apply the same principles

once you understood the role of hydrogen
bonding and pipe stacking connecting

a hydrogen bomb that substitution to
the pipe conjugated short flexible space.

So we made these very simple small
molecules that crystallized very nicely

into a layered structure with a
herringbone packing of the pie conjugated

segments very similar to the ones
you know from the parents.

Quarter siphon or Also however.

The lettuce parameters are roughly ten
percent smaller in all directions.

Supposedly because of the molecules are
quote unquote stitched together by let's

roll hydrogen bonding and

in collaboration again with clear most
common birth doing the fifty computations.

We have been able to show
that this leads to improve.

Overlap and not only that it also
helps to grow very nice and large

domains of the molecules and as a result
we obtain in this particular case and

mobility on the order of I'm sorry.

This should have been one actually on
the order of zero point forty five

centimeter square Provost
second which to those of

you are actually into those numbers that
you would say OK that's still not a good

performance compared to other
types of similar conductors.

But mind you that this is three times
higher than any other value reported for

quarter so if you.

Systems in the literature and I have to
admit that we're really not experts in

device making so I would consider
these devices highly optimized and

still the effect of local structure and

also more sinful morphology helps
to improve performance and I think

that this is something that needs to be
exploited in much more in the future.

So I would like to think
the guys that are responsible for

the project which is mainly
the young fight yeah.

Who has done all the work on the present.

If you just defended in April and
now does a postdoc in Germany.

This is home on ma to
you is responsible for

the work on the Paralympics emits young
who does all sorts of spectroscopy for us.

Hartman who is our electron microscopy and

force microscopy expert with device
manufacturing without using He's a and

engineer with forty eight years
of working at E.P.A. fell.

Imagine this.

I would not have been able
to start this work without

in a number of collaborators the guys
in blue actually contributed to

the project a number of funding
agencies and of course.

I need to thank you for
your attention and also for my for

your patience with me being
five minutes over time so.

And some cultural trivia and

this is our campus which is extremely
nicely located at Lake Geneva.

You see the friend French side the high
Alps the highest mountain in Europe

over here.

So that's very nice but the problem
is really the density of buildings so

we have literally no trees and this is
what I enjoy about your campus here.

You have

an easier time remodeling
the place of trees.

Built out from concrete you mean.

OK my own personal opinion.

So.

It's.

So there.

It's something that I forgot to mention Or

maybe I didn't mention it because where
were entering the realm of speculation.

There is an interesting
relation to elicit.

And maybe this is where
this Carol it Carol.

Thing comes into play.

It's actually one spin per
one hundred twenty molecules.

Which means one spin Perth sixty
nine meters which happens to be very

close to the HE little pitch.

It's roughly one spin per He little pitch.

Yeah.

So so I've only shown the region
of the region of the spectra

that is a kind of assigns to the region
where you would expect a radical.

However I can assure you that we made
very broad scans and we did not see

any other signatures for example we
also we cannot find the radical and ion.

And we don't see any kind of
triplet signature either.

So we tried our best to kind of you know
find other species but there is none.

So what do you see there
in fact is the radical.

This is a very sad story because
we need to redo the experiments.

Initially we thought we did and
you would expect that you do.

But we could in fact show in
controlled experiments that what we

saw was really just photoelectric
effect from the gold and so

we saw an increase with light but
it is really just the gold electrodes and

photoelectric effect in vacuum and we need
to redo the experiments in a better way.

I don't know whether we would have
to use other electrode materials or

something like that.

So I haven't until if you had you
seen my talking three months ago I

would at the very end have shown you
a nice slide where you can see you know

like increase of intensity with light but

an increase with current increase of
current with intensity of light but

unfortunately so far we did not
do this experiment in a good way.

I have every

year.

Like.

I'm really

sorry.

Very highly.

It should actually be the other way
around it should be the other way around.

If it if it did know it would narrow it
would narrow due to marshal narrowing.

And so what we actually assume North
rather the opposite is that we don't.

See the radical and ion because it
could be in the same region where we

see the other peak but it's so broad that
we don't actually see it underneath.

That's what we assume but
you're SOL It is still interesting because

I was discussing this with with
Richard friend and so he believes that

the high spin density that we see and the
fact that we only see it in the healing

system is first of all because we
if you think about it as a coral.

Surrounded by an all the peptide shell
roughly a quarter shell structure

but roughly it's a core shell structure
you generate these and ions in the shell

which shield the charge in the core and

this might be the reason why it's
only possible in the Nano why us and

not in the films of
the a coral molecule and

it might also explain why we can
generate such a high density of them.

That was his thought you
know you don't think that.

It might be de localized but
still not you know the question is why do

we see this and why has nobody people have
made quarter saw a few people have made

and estimates and the like but
they have never reported this.

So the question is why do we see it and

I personally I follow your line of thought
and I would think that due to the fact

that the cardinals are actually integrated
into this hydrogen bonded array.

This might give rise to the localization
once they are reduced and

this might be the reason why
their energy is so much or

the accessibility to towards reduction is
so much better than for other systems.

I believe that could be true but
I have no means or

I cannot think of a good
way of proving it.

So it's it's speculation.

We haven't

we haven't systematically looked
at that we haven't looked at them.