Direct excitation of tryptophan phosphorescence. A new method for triplet states investigation

Chavez, Jose; Ceresa, Luca; Reeks, John; Strzhemechny, Yuri M.; Kimball, Joseph; Kitchner, Emma; Gryczyński, Zygmunt; Gryczyński, Ignacy

doi:10.1088/2050-6120/ac4c9a

Cited by 7 publications

(5 citation statements)

References 23 publications

(29 reference statements)

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“…In far-field spectroscopy, tryptophan molecules have absorption bands in the UV range, around 280 nm. As it was recently reported (33, 34), tryptophan molecules demonstrate red-shifted bands both as phosphorescence and absorption. Here, we experimentally demonstrate that new optical transitions are possible under strong perturbation caused by the plasmonic nanoparticle (see details in section Tryptamine and pure dye molecules below).…”

Section: Introductionsupporting

confidence: 68%

Thermo-optoplasmonic single-molecule sensing on optical microcavities

Toropov,

Houghton,

et al. 2023

Preprint

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Whispering-gallery-mode (WGM) resonators are powerful instruments for single-molecule sensing in biological and biochemical investigations. WGM sensors leveraged by plasmonic nanostructures, known as optoplasmonic sensors, provide unprecedented sensitivity down to single atomic ions. In this article, we describe that the response of optoplasmonic sensors upon the attachment of single protein molecules strongly depends on the intensity of WGM. At low intensity, protein binding causes red shifts of WGM resonance wavelengths, known as the reactive sensing mechanism. By contrast, blue shifts are obtained at high intensities, which we explain as thermo-optoplasmonic (TOP) sensing, where molecules transform absorbed WGM radiation into heat. To support our conclusions, we experimentally investigated seven molecules and complexes; we observed blue shifts for dye molecules, amino acids and anomalous absorption of enzymes in the near-infrared spectral region. As an example of application, we propose a physical model of TOP sensing that can be used for the development of single-molecule absorption spectrometers.Significance StatementA notable contribution to the optical detection of single molecules has been brought about by using optical microcavities, specifically whispering-gallery-mode resonators that combine optical and plasmon resonances for the most sensitive single-molecule and ion detection. Adding absorption measurements to a single-molecule technique that operates in an aqueous solution would provide powerful new detection capabilities for sensing the properties of single molecules. We demonstrate here, for the first time, the detection of absorption cross-sections of protein molecules on optoplasmonic microcavities and validate the technique with seven different molecules and complexes. A proof-of-concept for single-molecule optoplasmonic absorption spectrometers is presented, based on a thermo-optoplasmonic sensing mechanism.

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Section: Introductionsupporting

confidence: 68%

Thermo-optoplasmonic single-molecule sensing on optical microcavities

Toropov,

Houghton,

et al. 2023

Preprint

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“…In summary, all our observations confirm the direct triplet state excitation. We also observed direct triplet state excitation for indole derivatives [16][17][18][19][20].…”

Section: Discussionmentioning

confidence: 61%

“…The PVA films are inert and do not dissolve in benzene. The refractive index of benzene matches well the refractive index of PVA film, making the film invisible [16,17]. Using a stack of films in the quartz cuvette, we measured a phosphorescence excitation spectrum with the observation set at 500 nm.…”

Section: Emission Measurements With Long-wavelength Excitationmentioning

confidence: 93%

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Room Temperature Phosphorescence of 5,6-Benzoquinoline

Chavez¹,

Ceresa²,

Kitchner³

et al. 2023

Methods Appl. Fluoresc.

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Phosphorescence emission of 5,6-Benzoquinoline embedded in poly (vinyl alcohol) film has been studied at room temperature. A strong green long-lived emission was observed in films doped with 5,6-Benzoquinoline while illuminated on a UV plate. A broad phosphorescence emission spectrum is centered at about 500 nm. The phosphorescence excitation spectrum follows the absorption spectrum of 5,6-Benzoquinoline, except for a long-wavelength part, which is well beyond the absorption band. This long-wavelength part of the absorption spectrum is responsible for the forbidden S0 – T1 transition. The excitation at 430 nm resulted in the long-lived emission with a spectrum similar to the phosphorescence spectrum obtained with UV excitation within the absorption of 5,6-Benzoquinoline. The phosphorescence anisotropy obtained with a direct S0 – T1 excitation is positive, while the UV excitation is negative. In contrast to fluorescence, the phosphorescence intensity strongly depends on temperature. Phosphorescence lifetimes with UV and long-wavelength excitation are similar, with a mean value of about 0.5 s.

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“…For a few years, we studied the RTP of different organic molecules embedded in PVA polymer excited directly to triplet states at longer wavelengths [5,[28][29][30][31][32][33][34]. The long-wavelength excitation (475 nm) of C106 in PVA samples is shown in 8.…”

Section: Effect Of Annealing On C106 In Pva Phosphorescencementioning

confidence: 99%

Effect of annealing on the room temperature luminescence of coumarin 106 in PVA films

Alexander,

Ceresa,

Pham

et al. 2023

Methods Appl. Fluoresc.

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We studied the effect of annealing on the luminescence of Coumarin 106 (C106) in poly (vinyl alcohol) films (PVA films). The samples and reference polymer films were treated at temperatures between 100 °C and 150 °C (212 F and 302 F) for various times. After cooling and smoothing, the samples and references were measured at room temperature. We observed that the PVA polymer (reference films) changes its optical properties with annealing at higher temperatures, affecting the baselines in absorption and the backgrounds in emission measurements. This requires precise background subtractions and control of the signal-to-noise ratio. Whereas the fluorescence intensity of C106 in PVA films modestly decreases with annealing, the phosphorescence depends dramatically and progressively increases by many folds. The fluorescence quantum yields and lifetimes decrease with the annealing, which suggests an increase in the non-radiative processes in the singlet excited state S1. The increase in the phosphorescence intensities results from increased intersystem crossing (ISC), which also decreases fluorescence. We also studied the effect of annealing on phosphorescence with the directly excited triplet state of C106. In this case, two processes are affected by annealing, S0→T 1 absorption and T1→S 0 phosphorescence. The long-wavelength excitation (475 nm) avoids PVA polymer excitation. The phosphorescence lifetime decreases with annealing while the phosphorescence intensity increases. These changes suggest that the radiative rate of T1 → S 0 increases with annealing.

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Direct excitation of tryptophan phosphorescence. A new method for triplet states investigation

Cited by 7 publications

References 23 publications

Thermo-optoplasmonic single-molecule sensing on optical microcavities

Thermo-optoplasmonic single-molecule sensing on optical microcavities

Room Temperature Phosphorescence of 5,6-Benzoquinoline

Effect of annealing on the room temperature luminescence of coumarin 106 in PVA films

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