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Z. Li, A. Ajami, E. Stankevičius, W. Husinsky, G. Račiukaitis, J. Stampfl, R. Liska, A. Ovsianikov:
"3D photografting with aromatic azides: A comparison between three-photon and two-photon case";
Optical Materials, 35 (2013), 1846 - 1851.

Photografting is a method utilizing light activation for covalent incorporation of functional molecules into
a polymer surface or polymer matrix. It has been widely applied as a simple and versatile method for tailoring
physical-chemical properties of various surfaces. Grafting induced via multi-photon absorption
provides additional advantages of spatial and temporal control of the process. Here, a novel fluoroaryl
azide photografting compound (AFA) was synthesized and compared with the commercially available
azide BAC-M. Using Z-scan technique, it was determined that AFA is a two-photon absorber at 798 nm,
whereas BAC-M is a three-photon absorber at this wavelength. Both azides were employed for 3D photografting
within a PEG-based matrix using femtosecond laser pulses. Both Z-scan measurements and 3D
photografting tests indicated that, the intensity threshold for nonlinear absorption and photografting
process is lower for AFA. As a result the processing window of AFA is much broader than that of BACM.
But on the other hand, since BAC-M is characterized by the three-photon absorption (3PA) process,
patterns with finer features can be produced using this molecule. The choice of the appropriate compound
for 3D grafting will depend on the final application and the requirements associated with the resolution
and post-modification protocol.

Femtosecond Multi-photon Patterning Functionalization Microfabrication Grafting