1CREOL & FPCE, The College of Optics and Photonics, University of Central Florida, Orlando, FL, 32816. 2Institute of Organic Chemistry, National Academy of ...
OSA / CLEO/QELS 2010 a1457_1.pdf CTuR5.pdf
Effective Generation of Triplet States and Singlet Oxygen by Sulfur-Containing Squaraines: Experimental and Theoretical Study Davorin Peceli1, Andriy O. Gerasov2,3, Scott Webster1, Honghua Hu1, Lazaro A. Padilha1,Volodymyr V. Kurdyukov2, Yuriy L. Slominsky2, Oleksandr O. Viniychuk2, Alexey D. Kachkovski2, Artem E. Masunov3, Olga V. Przhonska1,4, David J. Hagan1 , Eric W. Van Stryland1 1
CREOL & FPCE, The College of Optics and Photonics, University of Central Florida, Orlando, FL, 32816 2 Institute of Organic Chemistry, National Academy of Sciences, Kiev, 03094, Ukraine 3 NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826 4 Institute of Physics, National Academy of Sciences, Kiev, 03028, Ukraine
Abstract: Efficiency of singlet oxygen generation is investigated for a series of new sulfurcontaining squaraines molecules. Experimental results, in agreement with quantum calculations, show both large triplet quantum yield and quantum yield of singlet oxygen generation. ©2010 Optical Society of America OCIS codes: (160.4330) Nonlinear optical material, (170.5180) Photodynamic therapy, (300.6420) Nonlinear spectroscopy
1. Introduction The unique chemical properties of molecular singlet oxygen, O2 (1Δg), allows its use in many applications such as photodynamic therapy, water disinfection and purification, and organic synthesis. The most common method of producing O2 (1Δg) is through photosensitization. Excitation of a photosensitizer, by one- or two-photons, to its triplet state can allow for energy transfer to molecular oxygen which then produces O2 (1Δg). Identifying photosensitizing molecules with both large triplet quantum yields and quantum yields of singlet oxygen generation has been difficult [1-4]. One approach for creating photosensitizers has been to utilize “heavy atoms” in the molecular structure such as metal containing porphyrins, but this does not appear to be universally successful for other molecular classes. Recent interest has shifted to cyanine-like molecules such as squaraine dyes [5] which are known for their large two-photon absorption [6]. We are working towards understanding the mechanisms responsible for the increased rate of intersystem crossing seen in these molecules and engineering the molecular systems through an iterative process, utilizing extensive quantum chemical calculations and experimental measurements, to produce efficient triplet quantum yields. In this work we experimentally and theoretically study a series of squarylium molecules where two oxygen atoms are replaced with two sulfur atoms as seen in Fig. 1a. The sulfur atom substitutions lowers the energy difference between singlet and triplet states, as predicted by quantum chemical calculations, increasing intersystem crossing rate without the use of “heavy atoms”. With picosecond and femtosecond pump-probe spectroscopy, large values for triplet quantum yield and quantum yield of singlet oxygen generation (≈1) are measured. Results are compared to an identically structured oxygen-containing squaraine molecule shown in Fig. 1a. 2. Results and discussion Molecular structures and molar absorptivity spectra of dyes SD2405, SD7508 and SD7543 are shown in Fig. 1. The measured fluorescence quantum yield (ФF) for SD2405 is almost 1.0, while for SD7508 and SD7543, Ф F is
