poster iap-pai 2010
TRANSCRIPT
An amphiphilic PPV
Mn = 27000 g/mol (945 monomers), P.D.I. = 3.2
THF: good solvent, H2O: non-solvent
→ Investigated in solution for different ratios of THF/H2O
→ Coalescence at low temp (0° to 10° C) for intermediate ratios
(but completely absent for 10/0 and 1/9 THF/H2O)
Organic Qdots from an amphiphilic PPV?
Arvid Cloet(1)*, Els Braeken(1), Jan Duchateau(2),
Dirk Vanderzande(2), Johan Hofkens(1), Mark Van der Auweraer(1)
(1)K.U.Leuven (P2) and (2)U.Hasselt (P11)*K.U.Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Heverlee). E-mail: [email protected]
Stationary spectra1.25x10-5 M monomer, 1.32x10-8 M polymer
Absorption
Emission
Single-molecule measurements
3 different species can be distinguished:
•intermediate intensity, continuous bleaching:
open conformation
•low intensity, blinking: collapsed chain
•very high intensity, continuous bleaching:
multiple chains in a single dot?
All measured samples showed 2 species
→ but different fractions for different THF/H2O- ratios
10/0 to 7/2: decrease of open conformation
increase of collapsed chain
1/9: mainly multiple chains, some collapsed chains
Open conformationSpin coated from 1x10-9 M 10/0 THF/H2O (2000 rpm) + PVA coating (1000 rpm)
Collapsed chainSpin coated from 1x10-9 M 10/0 THF/H2O (2000 rpm) + PVA coating (1000 rpm)
Multiple chains in a single dotSpin coated from 1x10-7 M 1/9 THF/aqueous PVA (1g/L) (1500 rpm)
Conclusion
By varying solvent quality through changing the solvent/non-
solvent-ratio, it was found that a special kind of organic Qdot can
be obtained. This organic Qdot is thought to exist of multiple
chains collapsed into a single small dot (5 to 30 nm)[1]. It likely
arises from a strong, irreversible collapse[2] due to the low solvent
quality related to the high non-solvent fraction.
The extremely high emission intensity and the absence of blinking
make this kind of Qdot an interesting candidate for new types of
chromophores.
References
[1] Wu, C.; Bull, B.; Szymanski, C.; Christensen, K.; McNeill, J. ACS
Nano 2008, 2, 2415-2423.
[2] Yang, Z.; Huck, W.; Clarke, S.; Tajbakhsh, A.; Terentjev, E. Nature
Materials 2005, 4, 486-490.
lexc= 488 nm @ 100 W/cm2
Increasing
H20 fraction
lexc= 500 nm
1st species2nd species
3rd species?
Increasing
H20 fraction