photochemically deoxygenating solvents for triplet-triplet ... · using xe lamp light as excitation...

1

Photochemically deoxygenating solvents for triplet-triplet

annihilation photon upconversion operating under air

Shigang Wan,a Jinxiong Lin,a Huimin Su,b Junfeng Daib and Wei Lu*a

a Department of Chemistry, South University of Science and Technology of China,

Shenzhen, Guangdong 518055, P. R. China

E-mail: [email protected]

b Department of Physics, South University of Science and Technology of China, Shenzhen,

Guangdong 518055, P. R. China

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2018

mailto:[email protected]

2

Materials. All reagents and solvents were used as received unless otherwise indicated.

Platinum(II) octaethylporphyrin (Pt(OEP)) and Platinum(II) meso-tetraphenyl

tetrabenzoporphine (Pt(TPBP)) were purchased from Frontier Scientific, Inc. 9,10-

diphenylanthracene (DPA) was purchased from Alfa Aesar. 9,10-

Bis(phenylethynyl)anthracene (BPEA) and Rhodamine B were purchased from Tokyo

Chemical Industry (Shanghai). Spectroscopic grade dimethyl sulfoxide (DMSO), analytical

grade tetramethylene sulfoxide (TMSO), 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone

(DMPU), and 1,3-dimethyl-2-imidazolidinone (DMI) were purchased from J&K Scientific

Ltd.

Spectroscopic characterization. UV-Vis absorption spectra were recorded on a Thermo

Scientific Evolution 201 UV-Visible Spectrophotometer. Photo-emission, excitation spectra

and lifetimes for solutions were recorded on Edinburg spectrometer FLS-980 equipped with a

Xe light source, an MCP-PMT detector in a cooled housing (20 oC) which covers a range of

200–870 nm, and an NIR-PMT detector in a cooled housing (80 oC, cooled by liquid

nitrogen) which covers a range from 600–1700 nm. Upon the measurements of NIR emission

of singlet oxygen, an 850 nm long-pass filter was inserted in-between the sample and the

detector to avoid many high-order diffraction from the visible emission. Lifetime data were

analyzed with F980 software package. For triplet-triplet annihilation upconversion (TTA-

UC), the steady-state photoluminescence (PL) was recorded on Edinburg spectrometer FLS-

980 with a coherent cw laser at 532 nm as excitation source (Beijing Viasho Technology Co.

Ltd.). Time-resolved PL measurements have been excited at 532 nm of a Nd:YAG/OPO

(YAG stands for yttrium aluminum garnet) laser system and detected in photon counting

mode on Edinburg spectrometer LP-920 with ICCD and PMT detectors. All the

measurements have been done at room temperature (RT).

Using Xe lamp light as excitation source, emission traces of Pt(OEP) and TTA-UC in

aerated DMSO, TMSO, DMPU and DMI solutions were recorded on FLS-980 by using the

multiple scan mode and the shutter was set as always open. Emission intensity at fixed

wavelength versus time elapsed were recorded on FLS-980 by using the kinetic scan mode

and the shutter was set as always open.

Upconversion quantum yield determination. Upconversion quantum yield of

Pt(OEP)/DPA couple in different solvents and conditions was determined by the relative

method using Eq. S1,1

1 T. N. Singh-Rachford, A. Nayak, M. L. Muro-Small, S. Goeb, M. J. Therien and F. N. Castellano, J. Am. Chem. Soc., 2010, 132, 14203−14211.

3

∅𝑢𝑛𝑘 = 2∅𝑠𝑡𝑑(𝐴𝑠𝑡𝑑

𝐴𝑢𝑛𝑘)(𝐼𝑢𝑛𝑘

𝐼𝑠𝑡𝑑)(𝜂𝑢𝑛𝑘

𝜂𝑠𝑡𝑑)2 (S1)

where Φ, A, I and η represent the upconversion quantum yield, absorbance, integrated

photoluminescence intensity from the spectra and refractive index, respectively. Subscript std

denotes a reference fluorophore of known quantum yield and subscript unk denotes the

sample to be determined. Rhodamine B is used as the reference standard in this study. The

quantum yield of rhodamine B is Φstd = 0.65 in ethanol at room temperature under 532 nm

excitation.2 The refractive indices of ethanol, DMSO, TMSO, DMI and DMPU at 532 nm are

η(EtOH) = 1.361, η(DMSO) = 1.477, η(TMSO) = 1.52, η(DMI) = 1.471 and η(DMPU) =

1.488.3,4 The integrated intensity of the upconversion was measured in the region of 380-525

nm while that of rhodamine B was measured in the region of 540-750 nm. All measurements

were carried out under the same experimental conditions.

UV flashlight and portable UV lamp were used as light sources in the photo-activation

processes. The optical power densities of these UV light sources were measured with a CEL-

NP2000 optical power meter (Beijing CeauLight Sci. & Technol. Ltd.).

2 R. F. Kubin and A. N. Fletcher, J. Lumin., 1982, 27, 455−462.

3 T. M. Aminabhavi and B. Gopalakrishna, J. Chem. Eng. Data, 1995, 40, 856−861.

4 E. W. Washburn, C. J. West, N. E. Dorsey and M. D. Ring, International Critical Tables of Numerical Data. Physics, Chemistry, and Technology, 1st ed., 1930, Vol. 7.

4

Table S1. ФUC and Ith of Pt(OEP)/DPA in a variety of solvents at different conditions.

Solvent

ФUC / % Ith / mW cm2

Under

air

Deoxygenated by

N2-bubbling

Deoxygenated by

Photo-irradiation

Under

air

Deoxygenated by

N2-bubbling

Deoxygenated by

Photo-irradiation

DMSO 6.5 8.0 8.0 260 177 197

TMSO 6.9 6.5 8.6 - - 398

DMPU 5.2 7.0 6.9 310 212 190

DMI 6.3 7.5 4.7 475 180 251

Chart S1. Organic solvents under screening for photo-activated phosphorescence.

Figure S1. Absorption spectrum and emission traces of an aerated DMSO solution of

Pt(OEP) (~5.0106 mol dm3) upon continuous excitation at 385 nm at 298 K.

0

5

10

15

20

25

300 400 500 600 700 800

/ 10

4 d

m3 m

ol

1cm

1

Absorption

385 nm

Excitation

Em

issio

n Inte

nsity / A

. U

.

/ nm

0 min

18 min

3 min

Intervals

Photoactivated

Phosphorescence

5

Figure S2. (A) Photoluminescence spectra of the Pt(OEP) and DPA in aerated and deaerated

toluene (A), DMF (B) and THF (C) solutions with CW 532 nm laser as light source (296 mW

cm−2).

400 500 600 700

0

1x106

2x106

3x106

Em

issio

n I

nte

nsity /

A.

U.

/ nm

Under Air

Under Nitrogen

BA

400 500 600 700

0.0

2.0x106

4.0x106

6.0x106

8.0x106

Em

issio

n I

nte

nsity /

A.

U.

/ nm

Under Air

Under Nitrogen

C

400 500 600 700

0

1x105

2x105

3x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

Under Air

Under Nitrogen

6

Figure S3. Absorption spectra and emission traces of aerated TMSO solutions of Pt(OEP)

(~1.0105 mol dm3) upon continuous excitation at 390 nm (A) and 532 nm (B) at 298 K; (C)

Plots of photon counts at 645 nm against time elapsed for an aerated TMSO solution

containing Pt(OEP) (~1.0105 mol dm3) upon 532 nm excitation in a number of photo-

activation cycles.

0 360 720 1080 1440 1800 2160

0.0

2.0x106

4.0x106

6.0x106

8.0x106

4th Round for Photoactivation

3rd Round for Photoactivation

2nd

Round for Photoactivation

1st Round for Photoactivation

Photo

n C

ounts

@ 6

45 n

m

Time Elapsed for 532 nm Excitation / s

300 400 500 600 700 800

0

5

10

15

20

25

/ 10

4 d

m3m

ol

1cm

1

/ nm

Absorption

Em

issio

n Inte

nsity / A

. U

.

Photoactivated

Phosphorescence

532 nm

Excitation

0 min

20 min

2 min

Intervals

B

Under Air, 365 nm UV Torch

A

300 400 500 600 700 800

0

5

10

15

20

25

/ 10

4 d

m3m

ol

1cm

1

/ nm

Absorption

Em

issio

n Inte

nsity / A

. U

.

Photoactivated

Phosphorescence

390 nm

Excitation

0 min

20 min

2 min

Intervals

C

7

Figure S4. Absorption spectra and emission traces of aerated DMPU solutions of Pt(OEP)

(~1.0105 mol dm3) upon continuous excitation at 390 nm (A) and 532 nm (B) at 298 K.

Figure S5. Absorption spectra and emission traces of aerated DMI solutions of Pt(OEP)


B

Under Air, 365 nm UV Torch

0 s 15 s

A

300 400 500 600 700 8000

5

10

15

20

25

Em

issio

n I

nte

nsity /

A.

U.

/ nm

/

10

4 d

m3 m

ol

1cm

1

Absorption Photoactivated

Phosphorescence

390 nm

Excitation

0 min

30 min

3 min

Intervals

0

5

10

15

20

25

300 400 500 600 700 800

/ 10

4 d

m3 m

ol

1cm

1

Absorption

532 nm

Excitation

0 min

20 min

2.5 min

Intervals

Em

issio

n Inte

nsity / A

. U

.

/ nm

Photoactivated

Phosphorescence

B

0 s 15 s

A

0

5

10

15

20

300 400 500 600 700 800

/

10

4 d

m3m

ol

1cm

1

Absorption

Em

issio

n I

nte

nsity /

A.

U.

/ nm

380 nm

Excitation

Photoactivated

Phosphorescence

0 min

45 min

3 min

Intervals

0

5

10

15

20

300 400 500 600 700 800

/

10

4 d

m3m

ol

1cm

1

Absorption

Em

issio

n I

nte

nsity /

A.

U.

/ nm

0 min

25 min

2.5 min

Intervals

Photoactivated

Phosphorescence

532 nm

Excitation

8

Figure S6. Emission traces of aerated solutions of Pt(OEP) (~1.0105 mol dm3) and DPA

(~1.0103 mol dm3) upon continuous excitation at 532 nm (no-coherent light) at 298 K: (A)

TMSO, (B) DMPU and (C) DMI; (D) Plots of photon count at 434 and 645 nm against time

elapsed for 532 nm excitation for a TMSO solution of Pt(OEP) (~1.0105 mol dm3) and

DPA (~1.0103 mol dm3) upon continuous excitation at 532 nm at 298 K under air and after

nitrogen-bubbling.

400 500 600 700 800

Em

issio

n In

ten

sity /

A.

U.

/ nm

0 min

27 min

3 min

Intervals

532 nm

Excitation

400 500 600 700 800

400 450 500

0

500

1000

1500

2000

Em

issio

n I

nte

nsity /

A.

U.

/ nm

20 min

0 min

2 min

Intervals

532 nm

Excitation

400 500 600 700 800

Em

issio

n Inte

nsity / A

. U

.

/ nm

0 min

30 min

2 min

Intervals

532 nm

Excitation

BA

C D

0 480 960 1440 1920 2400 2880

0

1x106

2x106

3x106

4x106

5x106

@434 nm, Under Air

@645 nm, Under Air

@434 nm, N2-Bubbled

@645 nm, N2-Bubbled

Photo

n C

ounts


9

Figure S7. Emission traces of DMSO solutions of Pt(OEP) (~5.0106 mol dm3) and DPA

(~1.0103 mol dm3) upon irradiation with a CW 532 nm laser at a variety of optical power

densities at 298 K and under different conditions: (A) under air, (C) deoxygenation by

nitrogen bubbling and (E) deoxygenation by photo-irradiation. Double logarithm plots of

integrated emission intensity of the upconverted fluorescence of DPA against laser power

under different conditions: (B) under air, (D) deoxygenation by nitrogen bubbling and (F)

deoxygenation by photo-irradiation.

BA

DC

FE

400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

Em

issio

n Inte

nsity / A

. U

.

/ nm

1.757

1.547

1.291

1.240

0.173

0.140

0.103

0.092

Power density: W/cm2

100 1000

105

106

UC

PL

In

ten

sity /

A.

U.

Power density / mW cm2

Slope = 1.9

Slope = 1.2

Ith = 260 mW cm

2

400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

Em

issio

n Inte

nsity / A

. U

.

/ nm

1.757

1.547

1.240

1.107

0.103

0.061

0.054

0.028

532 nm

Excitation


100 100010

3

104

105

106

UC

PL Inte

nsity / A

. U

.


Slope = 1.9

Slope = 1.3

Ith = 177 mW cm

2

400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

1.757

1.547

1.291

1.240

0.092

0.061

0.054

0.028


532 nm

Excitation

100 1000

104

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 1.9

Slope = 1.2

Ith = 197 mW cm

10

Figure S8. Emission traces of TMSO solutions of Pt(OEP) (~1.0105 mol dm3) and DPA







100 100010

3

104

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 2.4

BA

DC

FE

100 100010

2

103

104

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 2.2

100 100010

4

105

106

UC

PL Inte

nsity / A

. U

.


Slope = 1.9

Slope = 1.1

Ith = 398 mW cm

2

400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

1.5x105

Em

issio

n Inte

nsity / A

. U

.

/ nm

1.222

1.107

1.084

0.975

0.140

0.118

0.092

0.061


532 nm

Laser

400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

1.107

1.084

0.975

0.954

0.244

0.209

0.173

0.140

532 nm

Laser


400 500 600 700 800

0.0

3.0x104

6.0x104

9.0x104

1.2x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

1.222

1.107

1.084

0.955

0.118

0.092

0.061

0.054


532 nm

Laser

11

Figure S9. Emission traces of DMPU solutions of Pt(OEP) (~1.0105 mol dm3) and DPA







BA

DC

FE

100 1000

105

106

UC

PL

In

ten

sity /

A.

U.


Slope= 2.0

Slope = 0.98

Ith = 310 mW cm

100 1000

104

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 1.9

Slope = 1.0

Ith = 212 mW cm

2

100 100010

4

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 2.0

Slope = 0.99

Ith = 190 mW cm

2

400 500 600 700 800

0.0

2.0x104

4.0x104

6.0x104

8.0x104

Em

issio

n I

nte

nsity /

A.

U.

/ nm

1.324

1.291

1.222

1.107

0.244

0.205

0.173

0.140

532 nm

Laser


400 500 600 700 8000

1x104

2x104

3x104

4x104

Em

issio

n Inte

nsity / A

. U

.

/ nm

0.890

0.859

0.789

0.700

0.103

0.061

0.054

0.028


532 nm

Laser

400 500 600 700 8000

1x104

2x104

3x104

4x104

5x104

6x104

Em

issio

n Inte

nsity / A

. U

.

/ nm

0.890

0.859

0.789

0.700

0.118

0.103

0.092

0.061


532 nm

Laser

12

Figure S10. Emission traces of DMI solutions of Pt(OEP) (~1.0105 mol dm3) and DPA







BA

DC

FE

100 100010

4

105

106

UC

PL

In

ten

sity /

A.

U.


Slope = 2.0

Slope = 1.0

Ith = 475 mW cm

2

100 1000

104

105

106

UC

PL Inte

nsity / A

. U

.


Slope = 2.2

Slope = 1.1

Ith = 180 mW cm

2

100 100010

4

105

106

UC

PL Inte

nsity / A

. U

.


Slope = 2.0

Slope = 1.0

Ith = 251 mW cm

2

400 500 600 700 800

0.0

2.0x104

4.0x104

6.0x104

8.0x104

1.0x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

1.757

1.291

0.222

1.107

0.205

0.173

0.140

0.118

532 nm

Laser


400 500 600 700 800

0.0

2.0x104

4.0x104

6.0x104

8.0x104

Em

issio

n Inte

nsity / A

. U

.

/ nm

0.975

0.954

0.889

0.789

0.092

0.061

0.053

0.028


532 nm

Laser

400 500 600 700 8000

1x104

2x104

3x104

4x104

5x104

Em

issio

n Inte

nsity / A

. U

.

/ nm

1.547

1.324

1.107

0.975

0.173

0.118

0.103

0.092


532 nm

Laser

13

Time-resolved emission spectra of Pt(OEP)/DPA in DMSO, TMSO, DMPU and DMI

solutions: The pulse time of the laser is too short (~7 ns) to allow the photochemical

deoxygenation of the solution. So, in aerated solutions, no UC emission was observed. In

deoxygenated solutions, we observed that Pt(OEP) phosphorescence at long wavelengths

decayed while the upconverted DPA fluorescence was produced as a function of time. The

results demonstrate that anti-Stokes delayed DPA fluorescence is indeed sensitized through

triplet state quenching of Pt(OEP) in the solution.

Figure S11. Time-resolved emission spectra of Pt(OEP) (~5.0106 mol dm3) and DPA

(~2.0104 mol dm3) in DMSO solutions: (A) under air, (B) deoxygenation by nitrogen

bubbling and (C) deoxygenation by photo-irradiation.


(~2.0104 mol dm3) in TMSO solutions: (A) under air, (B) deoxygenation by nitrogen


400500

600700

800

0.350.75

1.151.55

1.95

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

400500

600700

800

818

2838

48

Em

issio

n I

nte

nsity /

A.

U.

Time /

sW

avelength / nm

BA

400

500600

700800

818

2838

48

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

C

400

500600

700800

1022

3446

5870

Time /

s

Em

issio

n Inte

nsity / A

. U

.

Wavelength / nm 400

500600

700800

1022

3446

5870

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

400

500600

700800

0.350.75

1.151.55

1.95

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

BA C

14


(~2.0104 mol dm3) in DMPU solutions: (A) under air, (B) deoxygenation by nitrogen



(~2.0104 mol dm3) in DMI solutions: (A) under air, (B) deoxygenation by nitrogen


400

500600

700800

1022

3446

5870

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

400

500600

700800

0.350.75

1.151.55

1.95

Tim

e / s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm 400

500600

700800

1022

3446

5870

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

BA C

400

500600

700800

818

2838

48

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

400

500600

700800

818

2838

48

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

400

500600

700800

0.350.75

1.151.55

1.95

Time /

s

Em

issio

n I

nte

nsity /

A.

U.

Wavelength / nm

BA C

15

Figure S15. Phosphorescence of singlet oxygen in DMSO (A), TMSO (B), DMPU (C) and

DMI (D) solutions using Pt(OEP) as sensitizer. Black line: freshly prepared solutions; Red

line: solutions after photochemical deoxygenation.

1200 1250 1300 1350

0

20

40

60

80

Em

issio

n Inte

nsity / A

. U

.

/ nm

Freshly prepared solution

Photo-activation on

1200 1240 1280 1320

0

10

20

30

Em

issio

n Inte

nsity / A

. U

.

/ nm


Photo-activation on

1200 1240 1280 1320

0

10

20

30

Em

issio

n I

nte

nsity /

A.

U.

/ nm


Photo-activation on

BA

DC

1200 1240 1280 1320-10

0

10

20

30

40

Em

issio

n Inte

nsity / A

. U

.

/ nm


Photoactivation on

16

Figure S16. Absorption spectra and emission traces of aerated DMSO solutions of Pt(TPBP)


Figure S17. (A) Emission traces of an aerated DMSO solution of Pt(TPBP) (~1.0105 mol

dm3) and BPEA (~1.0103 mol dm3) upon continuous excitation at 615 nm (optical power

density 0.98 mW cm2) at 298 K; (B) Plots of photon count at 512 and 770 nm against time

elapsed for 615 nm excitation under air and after nitrogen-bubbling; (C) Snapshots of an

aerated DMSO solution of Pt(TPBP) and BPEA upon irradiation with a 635 nm portable laser

at 298 K.

300 400 500 600 700 800

0

3

6

9

12

15

Em

issio

n I

nte

nsity /

A.

U.

/ nm

0 min

16 min

2 min

Intervals

Photoactivated

Phosphorescence

438 nm

Excitation

/

10

4 d

m3m

ol

1cm

1

Absorption

B

0 s 15 s

A

300 400 500 600 700 800

0

3

6

9

12

15

Em

issio

n Inte

nsity / A

. U

.

/ nm

0 min

16 min

2 min

Intervals

615 nm

Excitation

Photoactivated

Phosphorescence

/ 10

4 d

m3m

ol

1cm

1

Absoption

500 600 700 800

0

1x105

2x105

3x105

4x105

Em

issio

n I

nte

nsity /

A.

U.

/ nm

A

C

B

0 300 600 900 1200 1500 1800

0.0

2.0x106

4.0x106

6.0x106

8.0x106

@512 nm, Aerated

@512 nm, N2-Bubbled

@770 nm, Aerated

@770 nm, N2-Bubbled

Photo

n C

ounts


Laser on

0 min

14 min

2 min

Intervals615 nm

Excitation

17

Figure S18. KI-Starch test for qualitative analysis of the oxidized products in DMPU

solutions of Pt(OEP) after 365 nm photo-irradiation under air: DMPU (0.1 mL), Pt(OEP)

(5.0×10−6 M), saturated aqueous solution of starch (1.4 mL), and KI (0.1 M), where

applicable. h means that the solution was irradiated with 365 nm UV torch and then exposed

to air for ten cycles.

Figure S19. KI-Starch test for qualitative analysis of the oxidized products in DMSO

solutions of Pt(OEP) after 365 nm photo-irradiation under air: DMSO (0.1 mL), Pt(OEP)

(5.0×10−6 M), saturated aqueous solution of starch (1.4 mL), and KI (0.1 M), where

applicable. h means that the solution was irradiated with 365 nm UV torch and then exposed

to air for ten cycles. This result revealed that the mechanism of photochemical deoxygenation

in sulfoxides is different from that in cyclic ureas.

+ +

− +

− −

DMPU

Pt(OEP)

hν

+

++

KI-starch test

+ +

− +

− −

DMSO

Pt(OEP)

hν

+

++

KI-starch test

18

Photoactivation phosphorescence process on FLS-980: In this paper, the photo-activation

time recorded is 18-45 minutes for phosphorescence maximizing on FLS-980. It doesn't mean

that the photochemical deoxygenation is slow. For completely phosphorescence photo-

activation, several seconds is enough. Prolonging the photo-activation time is just for clearly

observing and recording the photo-activation process. For a given solution, the photo-

activation time is determined by two factors on the FLS-980 spectrofluorometer: i) The

optical power density of the excitation, and ii) the photo-activation rate of the solution that is

exposed to the excitation light, as shown in Figure S20.

Figure S20. When light beam hits the solution from right to left, the power of the light will

decrease gradually from right to the left. The intensity of the light is enough to completely

photo-activate the right part of the solution and the photo-activation time is short. With the

decreasing of the intensity and diffusion of oxygen, the left part of the solution can only be

partially photo-activated and the photo-activation time is long. The spectrofluorometer

records only the emission intensity at the middle point of the light path.

Excitation

Photoactivation

phosphorescence

photochemically deoxygenating solvents for triplet-triplet ... · using xe lamp light as excitation...

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