Journal of Photochemistry and Photobiology A: Chemistry 2014, 295, p. 53-56;

The two-photon absorption of the photosensitizers 5,10,15,20-tetrakis(m-hydroxyphenyl) porphyrin and

the corresponding chlorin has been studied in the near infrared (IR) range using open-aperture z-scan

technique. We found cross sections of 10–40 GM in the Q-band region, comparable to values in the

Soret-band. Both photosensitizers are promising candidates for IR two-photon photodynamic therapy

given the better penetration of IR light into tissue.