Two-Photon Absorbing Block Copolymer as a Nanocarrier for Porphyrin: Energy Transfer and Singlet Oxygen Generation in Micellar Aqueous Solution

A novel amphiphilic water-soluble 2PA-chromophore-containing block copolymer was designed and synthesized. Micelles (nanostructures) were generated in the aqueous solution using the block copolymer and characterized using dynamic light scattering (DLS) and atomic force microscopy (AFM). We demonstrated that hydrophobic porphyrin could be incorporated into aqueous solution with the assistance of micelles. The results from DLS showed that the average diameters are in the range of 59−77 nm. Efficient energy transfer (as high as 96%) from the 2PA chromophore to porphyrin was observed in micellar aqueous solution even though the donor and acceptor were not covalently bonded. Furthermore, the energy transfer contributes to the efficient generation of the singlet oxygen (by a factor of 2.6 at 800 nm) from the porphyrin guest molecules

2-(2′-Hydroxyphenyl)benzoxazole-Containing Two-Photon-Absorbing Chromophores as Sensors for Zinc and Hydroxide Ions

Three new two-photon-absorbing (2PA) chromophores derived from 2-(2′-hydroxyphenyl)benzoxazole (HPBO), having two-photon absorption cross sections up to 530 GM (δ, expressed in GM; 1 GM = 1 × 10−50 cm4 s photon−1 molecule−1), were synthesized and investigated as metal ion and pH sensors. These chromophores were designed with an increasing number (0, 1, and 2) of HPBO(s) groups as binding sites for metal ions. Such variations provide a systematic approach to correlate structures with their linear photophysical, sensing, and two-photon absorption properties. The HPBO-containing sensors show unique response for zinc ion. Significant zinc ion stimulated photophysical properties with evident enhancements in fluorescence intensities from both one- and two-photon processes were detected. Moreover, one chromophore having HPBO groups in both terminal ends exhibits significant modulation of fluorescence intensities in response to the phenol group deprotonation in the HPBO moiety. A very large two-photon absorption cross section of 4120 GM, the highest reported for bisphenolate-containing 2PA materials, was measured for the chromophore under basic conditions. The molecular structures have a significant influence on the 2PA properties, which follows a trend of the substitution groups on the HPBO moiety in the order of −O− > −OZn > −OCH2R. The present study provides a protocol for elucidating the relationship between the photophysical properties and molecular structures