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Issue 16, 2006
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Large third-order nonlinear optical response of porphyrin J-aggregates oriented in self-assembled thin films

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Abstract

The preparation and characterization of a self-assembled material showing a high nonlinear response and good photostability to ultrashort laser pulses is presented. The material is built by alternate deposition of tetrakis(4-sulfonatophenyl)porphyrin diacid (H4TPPS2−) and poly(diallyldimethylammonium chloride) (PDDA) forming electrostatically self-assembled multilayers (ESAMs). UV-visible absorption and emission experiments show that in this matrix H4TPPS2− is present mainly in its J-aggregated form. Furthermore, linear dichroism experiments on a 3 bilayer film show a preferential alignment of the porphyrin aggregate with the J-band transition dipole moment parallel to the film surface. The two photon absorption (TPA) properties of these films are investigated with the Z-scan technique at 806 nm, employing 130 fs pulses. The samples exhibit strong nonlinearities with a very large two-photon absorption coefficient βTPA of 50 cm GW−1. The origin of this large response is investigated. It has been already demonstrated that aggregation enhances the molecular TPA cross section of H4TPPS2− from 30 to 1000 GM in water solution thanks to cooperative effects. In a 20 bilayer film a further increase by a factor of 1.7 is observed and explained in terms of preferential alignment of J-aggregates in the multilayers.

Graphical abstract: Large third-order nonlinear optical response of porphyrin J-aggregates oriented in self-assembled thin films

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Supplementary files

Article information


Submitted
12 Dec 2005
Accepted
07 Feb 2006
First published
13 Feb 2006

J. Mater. Chem., 2006,16, 1573-1578
Article type
Paper

Large third-order nonlinear optical response of porphyrin J-aggregates oriented in self-assembled thin films

E. Collini, C. Ferrante, R. Bozio, A. Lodi and G. Ponterini, J. Mater. Chem., 2006, 16, 1573
DOI: 10.1039/B517591G

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