Transfer of electronic energy in micellar solutions

307

OF ELECTRONIC

TRANSFER

N.

Roessler

and

Department

of

systems

of detergent

incorporated

either

enriched

double

layer

acceptor

ionic

in the

of the

transfer

and within

are

individual

water.

Following

pyrene

excimer.

determined

enter

excitation

by monitoring

trimethyl

fluoresceine

anions

charge

so that

anions

e.g.

sodium dodecyl

with

the

In further

radiative

sulfate,

experiments

transfer

we have studied

fluoresceine

(donor)

these

dyes are not

incorporated

on shape or size

is

and cosine into

solutions

energy

transfer

It

and thus

core, are

of

turned

detergents

like

which attract

the

was out

a repulsion

anionic

micelles,

can no longer

compete

between two anionic

in CTAB solutions.

the micellar

in

of transfer

Conversely,

transfer

dye

occurs

of pyrene,

containing excirner.

con-

the anionic

The rate

pyrene

of the micelle

in

low solubility

emissions

fast.

(acceptor)

determined

practically

Cationic

in solutions

from the

phase boundary,

is

decay of the donor.

SDS. Here energy

transition

the

because

CTAB, form micelles

place

of donor and electronic

extremely

of the micelle.

are

solution.

pyrene

the

ions

by the solution

acrOss

were observed.

energy

takes

dyes,

influenc6

of pyrene,

asnnonium bromide,

of fluoresceine

whereas

the fluorescence

location

of micellar

because of its

an

while

of transfer

(acceptor),

the micelle.

with

hydrocarbons

Accordingly,

fluorescence

and of fluoresceine

to depend on the surface cetyl

the

in the micelles flash

the

the micelle,

and fluoresceine

as two phase

in the electric

determined

of the micellar

(donor)

cannot

Thus is

structure

we have studied

solubilized

charge)

species.

within

1 ike

aggre-

phenomena.

of the micelles

The rate

taining

fluoresceine

transfer

COllDidal

paraffin

substances

of the micelle.

As an example,

only

of liquid

on their

molecular

place

energy

can be considered

surface.

energy

cases by the specific

pyrene

i.e.

transfer

interior

the micellar

surface

form micelles,

droplets

(depending

(F.R.G.)

Siegen

unusual

micelles

hydrophobic

can take

the

to

of

Water insoluble

or depleted

in dipole-dipole

properties

all

molecules

charge.

defining

University

to investigate

containing

surface

SOLUTIONS

MICELIAR

Chemistry,

in which the micelles

appreciable

energy

IN

B&au

can be exploited

Aqueous solutions

are

von

Physical

The tendency gates,

G.

ENERGY

they ideal

should

Since have no

probe molecules.

308

Furthermore,

the maximum of the

most exactly

with

energy

transfer

paration

ions

to establish is

large

are

energy

comparable

the concentratfons

possible ccl les

to compete effectively

distances

Keeping

located

conditions

in the

Stern

layer

of the average

Because of the peculiar

which

separations tance

this is

finding

electric

depends directly

of the Stern mation

layer.

a significantly the

micelle

anIonic rather

all

of

from the

value,

dyes are rigidly

i.e.

angle about

adsorbed

at constant

concentration

of micelles turned

constant

x-ray

in the dfffuse core.

This

and on the or light

diameters layer

Stern-

donor-acceptor

core

micelle

be

Separation

data was 6 nm. This

5 nm. Therefore,

on its

imply

the mfcelle.

diffraction

at con-

out to

ratios.

an effective

the micelle

to determine

distributed

of

the possible

diameter

by small

in the environment

can be done

surrounding

obtained

lower than

over

on the

were used previously

as

does not necessarily

layer

the

this

of the data

us to define

an-

yield

the concentration

The value

is not obtainable

methods that

average

is

between mi-

emission

solutions

the same rate

double

it

Experimentally.

molecules

of the

transfer

at se-

low.

distance

sama micelle.

plots

enables

a weighted

in the

emission

alallows

when donor and acceptor

of the acceptor

Stern-Volmer

the mechanism of energy kinetics,

distance

that

nature

in both cases and to furnish

Although

which

of the mice1 les.

the fluoresceine

number of acceptor

or by varyjng

dye concentration.

average

only

of the

the concentration

of donor and of micelles.

Volmer

spontaneous

dimensfons

the

occurs

by studying

a micelle.

linear

coincides

band of eosine,

the

external

such that

transfer

was monitored

by varying

with

to the

a function

stant

band of fluoresceIne

of the dyes and of CTAB sufffciently

and energy

transfer

either

emission

the maximum of the absorption

dlsextent

inforscattering

and yielded

our results surrounding

indicate the