Electric field-induced transient pore formation (reversible electroporation
) in the bilayer membrane of synthetic large unilamellar vesicles (LUV) is
used as a novel method for the preparation of angstrom size quantum dots of
the indirect band gap semiconductor AgBr. With Ag+ ions encapsulated in 17
8 nm diameter LUVs of dioleoylphosphatidylcholine (DOPC) and Br- ions place
d in the bulk medium, the reaction Ag+ + Br- --> AgBr and subsequent cluste
ring of the product are initiated by the application of a 500 mu s long hig
h-voltage (E = 6 kV/cm) electric square pulse to the vesicular suspension.
The slow growth of clusters (taking several hours) on the exterior surface
of the vesicles is monitored through the blue-shift followed by a redshift
of their UV absorption band. At the turn-around point (269 nm) of the spect
ral band-shift, the size of the AgBr clusters is estimated to be similar to
5 Angstrom, the smallest achieved by colloid chemical methods.