Measuring molecular singlet oxygen (1O2*) from atmospheric photosensitizers: Intercomparison of techniques, irradiation setups, data analysis and protocol recommendations
Abstract
Molecular singlet oxygen (1O∗2) is the first ex-cited state of molecular oxygen (O2) and can be formedthrough indirect photochemistry during irradiation of chromophoric organic matter. Once formed in the particle and droplet phases in the atmosphere, 1O∗2 can be a competitive oxidant in the photochemical processing of organic matter. Now, as more researchers study the atmospheric photo-chemistry of 1O∗2, establishing protocols by evaluating and comparing experimental setups across laboratories is becoming necessary. Here, we present 1O∗2 measurements from four photosensitizing molecules in four photoreactor setups at three research institutions, including two xenon lamps of different strengths and two multi-bulb UVA + UVB broad-band systems. The production of 1O∗2 was investigated from perinaphthenone, lignin, and juglone, which are photosensitizers with atmospherically relevant light absorbing moieties, as well as from Rose Bengal, a standard photosensitizer. Two chemical actinometers, 2-nitrobenzaldehyde and p-nitroanisole/pyridine, were used to quantify photon fluxes and calculate rates of light absorbance for photosensitizers for each photoreactor. We compared two commonly used 1O∗2 quantification methods, chemical probe method using furfuryl alcohol, as well as direct 1O∗2 phosphorescence detection at 1270 nm. Rates of light absorbance across ex perimental setups for each photosensitizer ranged between 0.2 and 62 × 10−5 molphotons L−1 s−1, while 1O∗2 steady-state concentrations ranged between 0.01 and 129 × 10−11 M. Despite order of magnitude differences in rate of light ab sorbance and 1O∗2 steady state concentrations, normalizingto 1O∗2 quantum yields showed good inter-laboratory agreement but only for the sensitizers with high quantum yields:perinaphthenone (94 % ± 9 %–112 % ± 17 %) and for Rose Bengal (67 % ± 15 %–87 % ± 5 %). 1O∗2 quantum yields for lignin and juglone increased with decreasing irradiation wavelength, highlighting a wavelength-dependence. Finally,we make five recommendations to improve the accuracy and reproducibility of 1O∗2 measurements for the atmospheric chemistry community. These recommendations include considering wavelength-dependent quantum yields, avoiding suppression of 1O∗2, controlling and reporting photoreactor temperature, considering light scattering from nanoparticles,and conducting control experiments. These recommendations can serve as guidelines to build future photoreactors as well as help standardize 1O∗2 measurements in studying photochemical processing of atmospheric aerosols and droplets.
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BibTeX
@article{gemmell2026measuring,
title = {{Measuring molecular singlet oxygen (1O2*) from atmospheric photosensitizers: Intercomparison of techniques, irradiation setups, data analysis and protocol recommendations}},
author = {K. Gemmell and L. Heinlein and E. Petersen-Sonn and C. Sardena and Z. Guo and N. Marino-Ocampo and B. Heyne and C. George and C. Anastasio and N. Borduas-Dedekind},
journal = {Atmospheric Measurement Techniques},
year = {2026},
month = jun,
doi = {10.5194/amt-19-3961-2026},
url = {https://hal.science/hal-05664574v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Measuring molecular singlet oxygen (1O2*) from atmospheric photosensitizers: Intercomparison of techniques, irradiation setups, data analysis and protocol recommendations
AU - K. Gemmell
AU - L. Heinlein
AU - E. Petersen-Sonn
AU - C. Sardena
AU - Z. Guo
AU - N. Marino-Ocampo
AU - B. Heyne
AU - C. George
AU - C. Anastasio
AU - N. Borduas-Dedekind
PY - 2026
DA - 2026/06/17
JO - Atmospheric Measurement Techniques
DO - 10.5194/amt-19-3961-2026
UR - https://hal.science/hal-05664574v1
AB - Molecular singlet oxygen (1O∗2) is the first ex-cited state of molecular oxygen (O2) and can be formedthrough indirect photochemistry during irradiation of chromophoric organic matter. Once formed in the particle and droplet phases in the atmosphere, 1O∗2 can be a competitive oxidant in the photochemical processing of organic matter. Now, as more researchers study the atmospheric photo-chemistry of 1O∗2, establishing protocols by evaluating and comparing experimental setups across laboratories is becoming necessary. Here, we present 1O∗2 measurements from four photosensitizing molecules in four photoreactor setups at three research institutions, including two xenon lamps of different strengths and two multi-bulb UVA + UVB broad-band systems. The production of 1O∗2 was investigated from perinaphthenone, lignin, and juglone, which are photosensitizers with atmospherically relevant light absorbing moieties, as well as from Rose Bengal, a standard photosensitizer. Two chemical actinometers, 2-nitrobenzaldehyde and p-nitroanisole/pyridine, were used to quantify photon fluxes and calculate rates of light absorbance for photosensitizers for each photoreactor. We compared two commonly used 1O∗2 quantification methods, chemical probe method using furfuryl alcohol, as well as direct 1O∗2 phosphorescence detection at 1270 nm. Rates of light absorbance across ex perimental setups for each photosensitizer ranged between 0.2 and 62 × 10−5 molphotons L−1 s−1, while 1O∗2 steady-state concentrations ranged between 0.01 and 129 × 10−11 M. Despite order of magnitude differences in rate of light ab sorbance and 1O∗2 steady state concentrations, normalizingto 1O∗2 quantum yields showed good inter-laboratory agreement but only for the sensitizers with high quantum yields:perinaphthenone (94 % ± 9 %–112 % ± 17 %) and for Rose Bengal (67 % ± 15 %–87 % ± 5 %). 1O∗2 quantum yields for lignin and juglone increased with decreasing irradiation wavelength, highlighting a wavelength-dependence. Finally,we make five recommendations to improve the accuracy and reproducibility of 1O∗2 measurements for the atmospheric chemistry community. These recommendations include considering wavelength-dependent quantum yields, avoiding suppression of 1O∗2, controlling and reporting photoreactor temperature, considering light scattering from nanoparticles,and conducting control experiments. These recommendations can serve as guidelines to build future photoreactors as well as help standardize 1O∗2 measurements in studying photochemical processing of atmospheric aerosols and droplets.
SN - 1867-1381
SN - 1867-8548
ER -