Spin—lattice relaxation in the phosphorescent triplet state of acridine and phenanthrene in zero-magnetic field

Antheunis, D.A.; Botter, B.J.; Schmidt, Jan; Verbeek, P.J.F.; Waals, J.H. van der

doi:10.1016/0009-2614(75)87021-7

Cited by 31 publications

(6 citation statements)

References 5 publications

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“…Thus, due to the fast spin relaxation characterizing the interacting system S 1 S 2 , during the continuous wave LEPR (CW-LEPR) measurement it is simply observed as a net effect, the disappearance of a part of the TEMPO signal under UV light. In fact, the resonance line width in the interacting system, , becomes so large and the resonance signal so broad that its resonance features becomes undetected due to the shortening of T 1 and T 2 …”

Section: Resultsmentioning

confidence: 88%

“…, becomes so large and the resonance signal so broad that its resonance features becomes undetected due to the shortening of T 1 and T 2 . 59 Kinetic Model of CD Fluorescence. To support the picture revealed by the LEPR measurements, we attempted to reproduce the experimentally observed time evolution of the fluorescence intensity after irradiation (at 372 nm) of CDs in different environments displayed in Figure 2d.…”

Section: [D + •••mentioning

confidence: 99%

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Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism

et al. 2021

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Highly fluorescent carbon nanoparticles called carbon dots (CDs) have been the focus of intense research due to their simple chemical synthesis, nontoxic nature, and broad application potential including optoelectronics, photocatalysis, biomedicine, and energy-related technologies. Although a detailed elucidation of the mechanism of their photoluminescence (PL) remains an unmet challenge, the CDs exhibit robust, reproducible, and environment-sensitive PL signals, enabling us to monitor selected chemical phenomena including phase transitions or detection of ultralow concentrations of molecular species in solution. Herein, we report the PL turn-off/on behavior of aqueous CDs allowing the reversible monitoring of the water–ice phase transition. The bright PL attributable to molecular fluorophores present on the CD surface was quenched by changing the liquid aqueous environment to solid phase (ice). Based on light-induced electron paramagnetic resonance (LEPR) measurements and density functional theory (DFT) calculations, the proposed kinetic model assuming the presence of charge-separated trap states rationalized the observed sensitivity of PL lifetimes to the environment. Importantly, the PL quenching induced by freezing could be suppressed by adding a small amount of alcohols. This was attributed to a high tendency of alcohol to increase its concentration at the CD/solvent interface, as revealed by all-atom molecular dynamics simulations. Based on this behavior, a fluorescence “turn-on” alcohol sensor for exhaled breath condensate (EBC) analysis has been developed. This provided an easy method to detect alcohols among other common interferents in EBC with a low detection limit (100 ppm), which has a potential to become an inexpensive and noninvasive clinically useful diagnostic tool for early stage lung cancer screening.

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Section: Resultsmentioning

confidence: 88%

Section: [D + •••mentioning

confidence: 99%

Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism

et al. 2021

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“…Much of the early work on SLR was carried out on transition metal ions and free radicals , in crystalline solids. SLR measurements of the photoexcited triplet states of aromatic molecules in crystals were first reported by Wolfe, and subsequently by other investigators. − …”

Section: Introductionmentioning

confidence: 91%

“…SLR measurements of the photoexcited triplet states of aromatic molecules in crystals were first reported by Wolfe, 5 and subsequently by other investigators. [6][7][8][9][10] Although the interpretation of SLR in crystals follows from ideas elaborated by van Vleck, 2,11 the process differs significantly in disordered solids. SLR of free radicals in a frozen glass matrix at cryogenic temperature is orders of magnitude more efficient than it is in a crystalline matrix; 12 this also is the case for photoexcited triplet states of aromatic molecules.…”

Section: Introductionmentioning

confidence: 99%

“…SLR of free radicals in a frozen glass matrix at cryogenic temperature is orders of magnitude more efficient than it is in a crystalline matrix; 12 this also is the case for photoexcited triplet states of aromatic molecules. [13][14][15][16] In low temperature glasses, SLR follows an approximately T 2 dependence rather than T 1 (direct phonon process) and T 5 or T 7 (phonon scattering process) found in crystalline samples. 1,2 SLR in glasses is believed to be dominated by coupling of the spins to disorder (tunneling) modes that modulate the electron-(solvent) nuclear dipole (END) interaction in the case of free radicals 12 or the electron-electron dipolar (EED) coupling in the case of triplet states.…”

Section: Introductionmentioning

confidence: 99%

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Spin−Lattice Relaxation of the Tryptophan Triplet State Varies with Its Protein Environment

et al. 2002

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Spin-lattice relaxation (SLR) has been studied at 1.2 K in the photoexcited triplet state of tryptophan (Trp) in a number of protein sites in zero applied magnetic field. We find that there is a distribution of SLR rate constants in every case that indicates the partitioning into two populations, n s 0 and n f 0 , with differing behavior. n s 0 undergoes slow SLR with rate constants in the range found in crystalline matrixes, while the SLR of n f 0 is at least 1-2 orders of magnitude faster. The former population has considerable spin alignment during optical pumping, decays nonexponentially, and gives rise to optically detected magnetic resonance (ODMR) responses at 1.2 K. The latter has negligible spin alignment, decays largely as a single exponential, and is ODMR silent. The rapid SLR of n f 0 is attributed to coupling with disorder (tunneling) modes that modulate the electron-electron dipolar coupling, and whose efficiency varies with protein site. The less efficient SLR of n s 0 is the result of direct interaction with lattice phonons. We find no correlation of the distribution of populations with the heterogeneity of the protein site as determined by ODMR bandwidth. It is suggested that more efficient disorder mode-induced SLR is associated with decreased rigidity of the local environment.

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Spin-Lattice and Spin-Spin Relaxation in Photo-Excited Triplet States in Molecular Crystals

Schmidt¹

1989

Relaxation Processes in Molecular Excited States

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Spin—lattice relaxation in the phosphorescent triplet state of acridine and phenanthrene in zero-magnetic field

Cited by 31 publications

References 5 publications

Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism

Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism

Spin−Lattice Relaxation of the Tryptophan Triplet State Varies with Its Protein Environment

Spin-Lattice and Spin-Spin Relaxation in Photo-Excited Triplet States in Molecular Crystals

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