Two-Photon Photosensitized Production of Singlet Oxygen

Abstract

Singlet molecular oxygen (a(1)Delta(g)) has been produced and optically detected upon two-photon nonlinear excitation of a sensitizer with a focused laser beam. The experiments were performed using toluene solutions with either a substituted difuranonaphthalene or a substituted distyryl benzene as the sensitizer. The data indicate that the two-photon absorption cross sections of the difuranonaphthalenes are comparatively large and depend significantly on the functional groups attached to the chromophore. The time-resolved 1270 nm phosphorescence signals used to characterize the production of singlet oxygen are limited in much the same way as signals from other two-photon spectroscopic studies (e.g., weak signals that can be masked by scattered radiation). Nevertheless, the two-photon singlet oxygen signals also reflect the unique advantages of this nonlinear optical technique (e.g., depth penetration in the sample afforded by irradiation in a spectral region void of the more dominant one-photon linear transitions and spatial resolution afforded by irradiation with a focused laser beam).

Effects of (Multi)branching of Dipolar Chromophores on Photophysical Properties and Two-Photon Absorption

“…In the quest of improving NLO properties, attention has been essentially focused on dipolar molecules for several decades. [1][2][3] More recently, quadrupolar systems have been designed and investigated [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and have shown improved properties, in particular with respect to the trade-off between optical transparency and NLO performance. Lately, attention has turned toward multipolar [22][23][24][25][26][27][28][29][30][31][32][33] and branched structures including dendrimers.…”

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

“…These groups constitute an attractive trigger because UV light induced Wolff rearrangement of DNQ to a 3-indenecarboxylic acid group with hydrophilic properties enhancing water solubility of that compound. Moreover, infrared light can be applied in photodynamic therapy [217][218][219][220] and liposome degradation [221]. Furthermore, mechanopores along the polymer poly(methyl acrylate) backbone (e.g., cyclobutane mechanopores) can be activated in polymers containing a coumarin dimer probe by mechanochemical scisson under pulsed ultrasound conditions (sonochemical) in solid state [222].…”

Significant effects of branches and bromine substitution of near-infrared two-photon photosensitizers on the generation of singlet oxygen

“…Near-infrared photon has remarkable advantage, such as low energy, excellent penetration and negligible damage to normal biological tissues. Hence, the utilization of near-IR laser to irradiate two-photon triplet photosensitizers to generate singlet oxygen receives considerable attentions [12][13][14][15][16][17][18]. While unfortunately, near-infrared TPA photodynamic therapy has never reached its full potentials due to the absence of the criteria for the design of photosensitizers with large twophoton absorption cross sections and high singlet oxygen quantum yields.…”

“…While unfortunately, near-infrared TPA photodynamic therapy has never reached its full potentials due to the absence of the criteria for the design of photosensitizers with large twophoton absorption cross sections and high singlet oxygen quantum yields. Bromine substitution is considered to be efficient approach to increase the quantum yields of singlet oxygen of TPA photosensitizers [16]. To our limited knowledge, it is unclear if bromine substitution has effects on the TPA properties of triplet photosenstitizers so far (if yes, how big and why?).…”

“…Tables 1 and 2 also showed that the absorption maxima, one-and two-photon emission maxima of the branched photosensitizers were red-shifted with respect to the linear ones respectively, which could be ascribed to the larger dipole moment changes and the lower HOMO-LUMO gaps of the branched photosensitizers in G2 as well (Table S1). According to Kasha's rule, the production of singlet oxygen is irrespective of the method by which initial excitation is realized, and thus the quantum yield of singlet oxygen generated upon two-photon excitation is considered to be the same as that produced upon one-photon excitation [16,17,20]. One-photon singlet oxygen quantum yields of the photosensitizers were determined by the photobleaching method of 9,10-diphenylanthracene (DPA) in this experiment (see the Supporting Information), and the data were also listed in Table 2.…”