Freezing single molecule dynamics on interfaces and in polymers

Abstract

Heterogeneous line broadening and spectral diffusion of the fluorescence emission spectra of perylene diimide molecules have been investigated by means of time dependent single molecule spectroscopy. The influence of temperature and environment has been studied and reveals strong correlation to spectral diffusion processes. We followed the freezing of the molecular mobility of quasi free molecules on the surface upon temperature lowering and by embedding into a poly(methyl methacrylate) (PMMA) polymer. Thereby changes of optical transition energies as a result of both intramolecular changes of conformation and external induced dynamics by the surrounding polymer matrix could be observed. Simulations of spectral fluctuations within a two-level system (TLS) model showed good agreement with the experimental findings.

Disentangling optically activated delayed fluorescence and upconversion fluorescence in DNA stabilized silver nanoclusters

“…3A–C). In PVA, the cause of the red-shift with longer NIR excitation wavelength is mainly due to freezing of a large range of spectral (conformational) states of the DNA-AgNCs during the immobilization process in PVA – a process which is well known for organic dyes 23,24. The findings in PVA can be explained with the wavelength dependence of UCF shown in Fig.…”

Single Molecule Studies on Dynamics in Liquid Crystals

“…This renders nonlinear optical effects negligible which otherwise have been observed for dye concentrations of 1% in liquid crystal [21]. Since their implementation, SM methods have been used in a broad field of soft matter materials [18,19] including dynamics in ultrathin films [22–27] or nanopores [28,29] and on surfaces [30,31]. Corresponding investigations in the field of LC are rare.…”

Probing heterogeneity of NIR induced secondary fluorescence from DNA-stabilized silver nanoclusters at the single molecule level

“…Similar conformational immobilization has been previously observed for single dye molecules in polymers. 24,25 Further studies changing parameters like viscosity, dielectric constant, and temperature could provide insight in which parameters affect the SF/PF ratio. Fig.…”