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Photosensitizers for 1O2 Production

We offer a range of organic photosensitizers for the efficient generation of singlet Oxygen, 1O2.  Our photosensitizers typically have high extinction coefficients, triplet states of appropriate energies (ET > 95 kJ mol-1) to allow for efficient energy transfer to ground state oxygen[1], a high triplet state yield with long triplet state lifetimes.  We offer several sensitizer products over the visible spectral range.

Sensitizers at a glanceAbsorbance Region
Sensitizer Blue™ 260 - 240 nm
Methuselah Green Carboxy™ 280 - 360 nm
Rose Bengal 490 - 575 nm
Erythrosin B 470 - 530 nm
Methylene Blue 550 - 700 nm

 

Sensitizer Blue™

Sensitizer Blue™ is a water soluble fluorescent and phosphorescent probe with an absorbance from 260-350 nm, with λmax ≈ 320 nm.  The blue fluorescence band of Sensitizer Blue™ from 380-460 nm, can readily be excited in the range 300-350 nm.  The Phosphorescence spectra is centered around 510 nm which can readily excited from 280-320 nm, see Figure 1. The phosphorescence lifetime increases when the excitation wavelength is reduced from 320 to 280 nm, 2.81 and 3.07 ms respectively in air-equilibrated glycerol at 0 C.

Figure 1 v5

Figure 1. (A) Absorption spectra recorded for Sensitizer Blue™ dissolved in methanol (red solid line) and in glycerol (blue dash-dotted line). (B) Fluorescence contour plot recorded for Sensitizer Blue™ dissolved in glycerol at 0 C (+32 F). All samples were equilibrated with air.

 

Sensitizer Blue™ can readily and efficiently sensitize oxygen to produce singlet oxygen. Figure 2 shows the emission spectra recorded for Singlet Oxygen Sensor Green (SOSG) in the presence of Sensitizer Blue™, and illuminated for different time periods. The concentration of Sensor Green was ≈ 1 µM and Sensitizer Blue™ ≈ 11 µM.  As the illumination time increases then more singlet oxygen is produced by Sensitizer Blue™ and subsequently detected by the sensor green. Panel B shows the integrated area under the sensor green emission spectra (i.e. data of panel A).

Figure 2

Figure 2. (A) Emission spectra recorded for Singlet Oxygen Sensor Green™, excitation at 470 nm, as funcion of illumination times of the sensitizer Sensitizer Blue™. The sensitizer is illuminated at 320 nm. (B) Integrated fluorescence spectra, shown in panel A, as function of illumination time.

 

Methuselah Green Carboxy™

Methuselah Green Carboxy™ is a long lived, water-soluble phosphorescence probe, which can readily be conjugated to a range of biomolecules. Methuselah Green Carboxy can also be used as a sensitizer for singlet oxygen production.

Methuselah Green Carboxy™

Figure 3. (A) Emission spectra recorded for Singlet Oxygen Sensor Green™, excitation at 470 nm, as funcion of illumination times of the sensitizer Methuselah Green Carboxy™. The sensitizer is illuminated at 310 nm. (B) Integrated fluorescence spectra, shown in panel A, as function of illumination time.

 

Figure 3 A shows the emission spectra recorded for Singlet Oxygen Sensor Green (SOSG) in the presence of Methuselah Green Carboxy, and illuminated for different time periods.  The concentration of sensor green was ≈ 1 µM and Methuselah Green Carboxy ≈ 16.5 µM (ε= 5587 L mol-1 cm-1).  As the illumination time increases then more singlet oxygen is produced by Methuselah Green Carboxy and subsequently detected by the sensor green.  Panel 3B shows the integrated area under the sensor green emission spectra (i.e. data of panel A).  Note that the singlet oxygen generation declines after about 20 mins illumination at 310 nm, likely reflecting the consumption of the sensor green detection molecule in a non-reversible fashion.

Rose Bengal

We also offer the classic fluorophores, Rose Bengal and Methylene Blue, which are very effective photosensitizers, possessing appropriate energies for the sensitization of oxygen.  Rose Bengal has an intense absorption band in the range 480-550 nm, a quantum yield of 0.76 and produces singlet oxygen with high yields [2].

Figure 5 shows the emission spectra recorded for Singlet Oxygen Sensor Green (SOSG) in the presence of Rose Bengal in water, both at ≈ 1 uM concentration.  Figure 5 B shows the integrated area under the emission spectra of panel A, indicating the increase in singlet oxygen generation as a function of illumination time at 550 nm.

Figure 5v6

Figure 5. (A) Emission spectra recorded for Singlet Oxygen Sensor Green™, excitation at 470 nm, as funcion of illumination times of the sensitizer Rose Bengal. The sensitizer was illuminated at 550 nm. (B) Integrated and normalized fluorescence spectra shown in panel A plotted as function of illumination time.

 
Rose Bengal

Figure 6. Absorption (blue solid line) and fluorescence spectra (red dotted line) recorded for Rose Bengal dissolved in water. The absorption spectra for Singlet Oxygen Sensor Green™ (SOSG) is also shown. The chemical structure of Rose Bengal (RB) is shown in the right panel. When RB is illuminated at ~550 nm singlet oxygen, 1O2, is efficiently formed.

 

 

Methylene Blue

Methylene Blue is a phenothiazinium dye with a strong absorbance in the range 550-700 nm and a quantum yield of 0.52. [2].  The absorption peak is significantly different than that of the singlet oxygen sensor green molecule, which is widely used for the visible fluorescence-based detection of 1O2.

Methylene Blue

Figure 7. (A) Emission spectra recorded for Singlet Oxygen Sensor Green™, excitation at 470 nm, as funcion of illumination times of the sensitizer Methylene Blue. The sensitizer was illuminated at 650 nm. (B) Integrated and normalized fluorescence spectra shown in panel A plotted as function of illumination time.

 

Figure 7 A shows the emission spectra recorded for the Singlet Oxygen Sensor Green (SOSG) in the presence of Methylene Blue as a function of illumination time.  The excitation wavelength for the SOSG was 470 nm and the illumination wavelength for singlet oxygen generation by the Methylene Blue was 650 nm.  Figure 7B shows the integrated area under the emission spectra shown in Figure 7A.  From the figure we can see that the amount of singlet oxygen, as generated by the Methylene Blue, increases as a function of the illumination time. The absorbance spectra for Methylene Blue and Singlet Oxygen Sensor Green is shown in Figure 8. The chemical structure of Methylene Blue (MB) and a schematic of the siglet oxygen generation process is also outlined.

Methylene Blue and Singlet Oxygen Sensor Green

Figure 8. Absorption spectra recorded for Methylene Blue and Singlet Oxygen Sensor Green dissolved in water. The chemical structure of Methylene Blue (MB) is also shown. When MB is illuminated at ~650 nm singlet oxygen is efficiently formed in the solution.

 

 

Erythrosin B

Erythrosin B (Blue) is a well-known and very useful and efficient sensitizer of singlet oxygen, similar to Rose Bengal and other halogenated xanthene derivatives. In water, Erythrosin B has an absorption maximum of ~530 nm, separated from that of the well know singlet oxygen sensor green, SOSG, Figure 9, with a quantum yield of 0.63 in water, and 0.69 in ethanol [1]. Erythrosin B is water, methanol, ethanol and glycerol soluble, making this probe an ideal choice for your singlet oxygen studies.

Absorption spectra for Erythrosin B and Singlet Oxygen Sensor Green dissolved in water.

Figure 9. Absorbance spectra recorded for Erythrosin B (blue solid line) and for Singlet Oxygen Sensor Green (green dash dot line) dissolved in water.

 

Figure 10 A shows the emission spectra recorded for the Singlet Oxygen Sensor Green (SOSG) in the presence of Erythrosin B as a function of illumination time.  The excitation wavelength for the SOSG was 470 nm and the illumination wavelength for singlet oxygen generation by the Erythrosine B was 540 nm.  Figure 10 B shows the integrated area under the emission spectra shown in Figure  10 A.  From the figure we can see that the amount of singlet oxygen, as generated by the Erythrosin B, increases as a function of the illumination time. The SOSG is detecting the singlet oxygen generated by the Erythrosin B.

Erythrosin B int vs time

Figure 10. (A) Emission spectra recorded for Single Oxygen Sensor Green (SOSG) in presence of Erythrosin B as function of illumination time. The excitation wavelength for SOSG was 470 nm and the illumination wavelength for singlet oxygen generation by Erythrosin B was 540 nm. (B) Area under the emission band, panel A, plotted as function of illumination time at 540 nm.

 

Cited References

[1] DeRosa, M.C., and Crutchley, R.J., Photosensitized Singlet Oxygen and its Applications, Coordination Chemistry Reviews, 233-234, 351-371, 2002.
[2] Redmond, R.W., and Gamlin, J.N., A Compilation of Singlet Oxygen Yields from Biologically relevant Molecules, Photochem. Photobiol., 70, 391, 1999.

 

 

Single oxygen sensor green

Illustration of the detection mechanism of singlet oxygen, 1O2, by Singlet Oxygen Sensor Green (SOSG).

 

Single oxygen sensor green

Illustration of Ursa's sensitizing molecules. The left cuvette contains a sensitizer, e.g. Sensitizer Blue™, which upon illumination at 320 nm efficiently generates singlet oxygen. The singlet oxygen reacts with SOSG, mechanism shown in the box above, that fluoresces strongly when excited at 470 nm. The cuvette to the right contains no sensitizer, only SOSG, and is used as a reference, i.e. control sample. By recording the emission intensity of SOSG it is possible to quantify the singlet oxygen generation efficiency.

 

 Structures sensitizers