Matrix‐induced Linear Stark Effect of Single Dibenzoterrylene Molecules in 2,3‐Dibromonaphthalene Crystal

Abstract

Absorption and fluorescence from single molecules can be tuned by applying an external electric field – a phenomenon known as the Stark effect. A linear Stark effect is associated to a lack of centrosymmetry of the guest in the host matrix. Centrosymmetric guests can display a linear Stark effect in disordered matrices, but the response of individual guest molecules is often relatively weak and non‐uniform, with a broad distribution of the Stark coefficients. Here we introduce a novel single‐molecule host‐guest system, dibenzoterrylene (DBT) in 2,3‐dibromonaphthalene (DBN) crystal. Fluorescent DBT molecules show excellent spectral stability with a large linear Stark effect, of the order of 1.5 GHz/kVcm −1 , corresponding to an electric dipole moment change of around 2 D. Remarkably, when the electric field is aligned with the a crystal axis, nearly all DBT molecules show either positive or negative Stark shifts with similar absolute values. These results are consistent with quantum chemistry calculations. Those indicate that DBT substitutes three DBN molecules along the a ‐axis, giving rise to eight equivalent embedding sites, related by the three glide planes of the orthorhombic crystal. The static dipole moment of DBT molecules is created by host‐induced breaking of the inversion symmetry. This new host–guest system is promising for applications that require a high sensitivity of fluorescent emitters to electric fields, for example to probe weak electric fields.

High-resolution vibronic spectroscopy of a single molecule embedded in a crystal

“…56,57 For terrylene molecules, the appearance of several strong new lines could be explained by a non-planar deformation in various crystals. 58,59 In the case of DBT, however, the experimental observation of three characteristic strong lines in the < 300 cm −1 wavenumber region 52,53,60,61 as well as simulations in anthracene 61,62 , dimethylnaphtphalene 60 , and dibromonaphthalene 63 indicate that DBT does not change its conformation drastically as compared to its isolated case. A quantitative calculation of how embedding DBT in a matrix affects the FC factors of its vibrational modes has not been previously reported and will be presented for pDCB later in this article.…”

Roadmap on bio-nano-photonics

“…Using single molecules as two-level systems for QT has motivated the investigation of their nonlinear properties [70]. Highly sensitive energy tuning via external electric fields in novel host-guest system, enabled by a symmetry breaking of host, is promising for probing weak electric fields [71]. Placing such molecules into a narrowlinewidth and small optical cavity, their radiative rate was enhanced by a Purcell factor of 40 [72], resulting in a system at the onset of strong coupling.…”

Internal Stark effect of single-molecule fluorescence

“…In these examples, ISE occurs in complex landscapes composed of a large number of interacting organic systems. Scaling down these effects to single-molecules would be a step towards understanding the intimate interaction between biological pigments and their electrostatic environment, but has been so far limited to the spectroscopy of molecules in frozen matrices 11 – 14 and scanning-tunneling microscopy (STM) experiments 15 – 18 where external electric fields were used to shift the molecular states. The effect of an electric field generated by an elementary charge located within a chromophore on its optical properties remains up to now a Gedankenexperiment.…”