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Triplet-State Photochemistry of Dissolved Organic Matter: Triplet-State Energy Distribution and Surface Electric Charge Conditions
摘要： Excited triplet states of chromophoric dissolved organic matter (3CDOM*) are highly reactive species in sunlit surface waters and play a critical role in reactive oxygen species (ROS) formation and pollutant attenuation. In the present study, a series of chemical probes, including sorbic acid, sorbic alcohol, sorbic amine, trimethylphenol, and furfuryl alcohol, were employed to quantitatively determine 3CDOM* and 1O2 in various organic matters. Using a high concentration of sorbic alcohol as high-energy triplet states quencher, 3CDOM* can be first distinguished as high-energy triplet states (>250 kJ mol?1) and low-energy triplet states (<250 kJ mol?1). The terrestrial-origin natural organic matter (NOM) was found to mainly consist of low-energy triplet states, while high-energy triplet states were predominant in autochthonous-origin NOM and effluent/wastewater organic matter (EfOM/WWOM). The 1O2 quantum yields and electron transfer quantum yield coefficients (f TMP) generated from low-energy triplet states remained constant in all tested organic matters. External phenolic compound showed quenching effects on triplet-state formation and tended to have a higher quenching efficiency for aromatic ketone triplet states, which are the main high-energy triplet states. In comparison with terrestrial-origin NOM, autochthonous-origin NOM and EfOM/WWOM presented lower reaction rate constants for sorbic amines and higher reaction rate constants for sorbic acid, and these differences are likely due to dissimilar surface electric charge conditions. Understanding the triplet-state photochemistry of CDOM is essential for providing useful insights into their photochemical effects in aquatic systems.
关键词： surface charge,triplet-state photochemistry,energy distribution,dissolved organic matter,reactive oxygen species,chemical probes
更新于2025-11-19 16:56:35
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Photonics of tetramethoxy-1,4-distyrylbenzene
摘要： Photonics of tetramethoxy-1,4-distyrylbenzene in MeCN was studied by absorption, luminescence, and laser kinetic spectroscopies. Photoinduced transformations of the compound in question involve cis—trans-isomerization, intersystem crossing, fast and delayed fluorescence, and electron transfer. The ground-state structure and vibrational spectrum, as well as the energies and structures of excited singlet and triplet states were calculated by the DFT/PBE and TDDFT/PBE0 methods. The assignment of vibronic bands in the absorption spectra was made and the energies of corresponding transitions were calculated.
关键词： triplet state,trans—cis-photoisomerization,electron transfer,delayed fluorescence
更新于2025-09-23 15:23:52
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Photochemical Processes in Molecular Polymethine Dye Probes in the Presence of Bile Salts
摘要： Primary photochemical processes in polymethine dye probes 3,3′-di(γ-sulfopropyl)-4,5,4′,5′-dibenzo-9-ethylthiacarbocyanine betaine (DEC) and 3,3′,9-trimethylthiacarbocyanine iodide (Cyan 2) in micellar systems of bile-acid salts (BASs) sodium cholate, deoxycholate, and taurocholate and sodium dodecyl sulfate (SDS) as a reference are studied by flash photolysis. Signals due to photoisomerization of dye trans-isomers and dark reverse isomerization of the resulting cis-photoisomers are observed during pulse photolysis of air-saturated aqueous dye solutions in the presence of BAS and SDS micelles. The lifetimes of the photoisomers are 60–190 μs. Pulse photolysis of Cyan 2 and DEC solutions without oxygen and with BAS and SDS micelles induced photoisomerization and transition of the dyes into an excited triplet state followed by the reverse transition (intersystem crossing) into the initial singlet state. Triplet–triplet absorption spectra of these dyes isomers in polar (EtOH, i-PrOH) and nonpolar (dioxane) solvents were obtained for comparison using triplet–triplet energy transfer from anthracene. The conclusion was drawn that the photochemical behavior of the dyes in BAS and SDS micellar systems were similar.
关键词： triplet state,surfactants,polymethine dye probes,bile-acid salts,trans–cis photoisomerization,micelle
更新于2025-09-19 17:15:36
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On the impact of competing intra- and intermolecular triplet-state quenching on photobleaching and photoswitching kinetics of organic fluorophores
摘要： While buffer cocktails remain the most commonly used method for photostabilization and photoswitching of fluorescent markers, intramolecular triplet-state quenchers emerge as an alternative strategy to impart fluorophores with 'self-healing' or even functional properties such as photoswitching. In this contribution, we evaluated combinations of both approaches and show that inter- and intramolecular triplet-state quenching processes compete with each other. We find that although the rate of triplet-state quenching is additive, the photostability is limited by the faster pathway. Often intramolecular processes dominate the photophysical situation for combinations of covalently-linked and solution-based photostabilizers and photoswitching agents. Furthermore we show that intramolecular photostabilizers can protect fluorophores from reversible off-switching events caused by solution-additives, which was previously misinterpreted as photobleaching. Our studies also provide practical guidance for usage of photostabilizer–dye conjugates for STORM-type super-resolution microscopy permitting the exploitation of their improved photophysics for increased spatio-temporal resolution. Finally, we provide evidence that the biochemical environment, e.g., proximity of aromatic amino-acids such as tryptophan, reduces the photostabilization efficiency of commonly used buffer cocktails. Not only have our results important implications for a deeper mechanistic understanding of self-healing dyes, but they will provide a general framework to select label positions for optimal and reproducible photostability or photoswitching kinetics in different biochemical environments.
关键词： photoswitching,intramolecular quenching,self-healing dyes,super-resolution microscopy,intermolecular quenching,photostabilization,fluorophores,triplet-state quenching,STORM
更新于2025-09-19 17:15:36
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Similarity and Specificity of Chlorophyll <i>b</i> Triplet State in Comparison to Chlorophyll <i>a</i> , as Revealed by EPR/ENDOR and DFT Calculations.
摘要： An investigation of the photoexcited triplet state of chlorophyll (Chl) b has been carried out by means of Electron Nuclear Double Resonance (ENDOR), both in frozen organic solvent and in protein environment provided by the Water-Soluble Chlorophyll Protein of Lepidium virginicum. Density functional theory (DFT) calculations have allowed the complete assignment of the observed hyperfine couplings corresponding to the methine protons and the methyl groups, leading to a complete picture of the spin density distribution of the triplet state in the tetrapyrrole macrocycle. The triplet state properties of Chl b were found to be similar in many respects to those previously reported for Chl a, although some specificities have been highlighted. Concerning the spin density distribution, the differences are manly localized on the carbon atoms close to the formyl group which, in Chl b, replaces the methyl group of Chl a.
关键词： EPR/ENDOR,triplet state,DFT calculations,Chlorophyll b,spin density distribution
更新于2025-09-11 14:15:04
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A systematic investigation on the bactericidal transient species generated by photo-sensitization of natural organic matter (NOM) during solar and photo-Fenton disinfection of surface waters
摘要： In this work, the role of dissolved oxygen in the solar and the photo-Fenton-mediated E. coli inactivation process was put under scrutiny. The effect of transient species that were produced in the Nordic Reservoir (NR) NOM, SR Humic acid (SRHA), and SR Fulvic acid (SRFA) was studied in presence of various natural organic matter isolates (NOM), namely Suwannee River (SR) NOM, detail. The role of 1??2 in this reaction was systematically evaluated by modifying the O2 concentration (N2/O2 purging) and the matrix composition (10, 50, and 100% deuterium oxide (D2O) v/v). In the presence of NOM, 1??2 was generated and the enhancement of E. coli inactivation rate due to charge transfer from triplet state to molecular oxygen. The comparison between SR and NR NOM showed that for these compounds, triplet state of NOM (3NOM*), and 1??2 were the more favorable active species in E. coli inactivation, respectively. Also, the second order rate constants (????.???????? 2???? ) of E. coli with 3NOM*, and 1??2 were calculated by using the steady state approximation. The obtained results showed that the rate values of 1??2 related to NR NOM was ~ 5.6 times higher than SR NOM, while the rate values of 3NOM* for SR NOM was ~ 8.7 times higher than NR NOM. We also determined the effect of these organic matter isolates in the photo-Fenton process and its constituents (solar/Fe2+, solar/H2O2, and solar/Fe2+/H2O2). In presence of NOM, the photo-Fenton process inactivation rates increased which confirmed that the combined processes has additional pathways generated with disinfecting effect during solar exposure of bacteria.
关键词： solar disinfection (SODIS),singlet oxygen,triplet state,Advanced oxidation process (AOPs),E. coli
更新于2025-09-09 09:28:46
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A Pentacene-based Nanotube Displaying Enriched Electro/Photochemical Activities
摘要： This article reports the synthesis and characterization of a pentacene-based nanotube that exhibits enriched electrochemical and photochemical activities. The nanotube is constructed from a pentacene chromophore and features a tubular conformation with a triangular cross-section, enabling unique electronic and photophysical properties. The study demonstrates the nanotube's ability to facilitate efficient intramolecular charge transfer and triplet-state generation, highlighting its potential for applications in optoelectronic devices and photocatalysis.
关键词： nanotube,electrochemical,pentacene,triplet-state,charge transfer,photochemical
更新于2025-09-04 15:30:14