Reverse Intersystem Crossing of Single Deuterated Perylene Molecules in a Dibenzothiophene Matrix

Abstract

Intersystem crossing to the long‐lived metastable triplet state is often a strong limitation on fluorescence brightness of single molecules, particularly for perylene in various matrices. In this paper, we report on a strong excitation‐induced reverse intersystem crossing (rISC), a process where single perylene molecules in a dibenzothiophene matrix recover faster from the triplet state, turning into bright emitters at saturated excitation powers. With a detailed study of single‐molecule fluorescence autocorrelations, we quantify the effect of rISC. The intrinsic lifetimes found for the two effective triplet states (8.5±0.4 ms and 64±12 ms) become significantly shorter, into the sub‐millisecond range, as the excitation power increases and fluorescence brightness is ultimately enhanced at least fourfold. Our results are relevant for the understanding of triplet state manipulation of single‐molecule quantum emitters and for markedly improving their brightness.

Future Paths in Cryogenic Single-Molecule Fluorescence Spectroscopy

“…Moradi et al investigated a new guest–host system, DBT in DBN discussed earlier, which demonstrated a strong linear Stark effect . Smit et al recently reported the reverse intersystem crossing (rISC) of deuterated perylene in dibenzothiophene, which helped in recovering the fluorescence loss by the ISC process. Such a mechanism is promising for controlling the triplet state lifetime, specifically for the purpose of super-resolution imaging under cryogenic conditions. , Apart from investigating the electronic states of a molecule, the study of a vibrational energy state and its higher-resolution spectroscopic investigation are important steps for quantum-optical applications.…”

“…Therefore, the molecules have to be excited by the S 0 → S 1 transition, which for perylene has a wavelength between 440 and 450 nm. Once in the excited state, a small fraction of the excitations are converted to the triplet excited state, , with a typical yield of about 10 –6 . The radiative quantum yield of the triplet would be expected to be around 10 –2 –10 –3 , thus reducing the yield of phosphorescence photons to 10 –8 –10 –9 .…”

Light-Induced Forward and Reverse Intersystem Crossing in Green Fluorescent Proteins at Cryogenic Temperatures

“…The former is the one that served to establish room-temperature triplet state characteristics; the latter has recently been proposed as a suitable candidate for cryoactivation-based microscopy . Both prototypical FPs serve as benchmarks for the performance characterization of a steady stream of newly developed FPs of various colors and enhanced properties. , Here, we provide insight into two processes that decisively determine the performances of EGFP and rsEGFP2: light-induced formation and decay of the first excited triplet state T 1 (forward and reverse intersystem crossing, denoted FISC and RISC, respectively). − Strategies to enhance photostability by RISC enhancement have been proposed . In EGFP, T 1 has been shown to live few milliseconds at room temperature (RT), and a T 1 absorption spectrum at RT has been measured, but the dominant contribution of ground-state bleaching prevented the determination of the T 1 absorption coefficient at the popular excitation wavelength 488 nm .…”

“…18−21 Strategies to enhance photostability by RISC enhancement have been proposed. 20 In EGFP, T 1 has been shown to live few milliseconds at room temperature (RT), and a T 1 absorption spectrum at RT has been measured, 11 but the dominant contribution of ground-state bleaching prevented the determination of the T 1 absorption coefficient at the popular excitation wavelength 488 nm. 11 Here, we make use of the cooling-induced lifetime prolongation of T 1 to measure its complete NUV−vis−NIR absorption spectrum at CT, immediately after a saturating pulse of 488 nm laser excitation.…”