Application of Buffon‘s needle on molecular fluorescence probability

Fluorescence of extended and collective quantum systems (SWCNTs) Fluorescence emitter density from fluorescence images Monte Carlo simulations for molecular fluorescence quenching Applications of Buffon's needle </p

Application of Buffon’s needle on concentration- and lengthdependent fluorescence probability of single-wall carbon nanotubes down to the single-molecule regime

Fluorescence spectroscopy on the single-molecule level can contribute enormously to the mechanistic understanding of molecular photo processes. For this purpose fluorescence-based single-molecule microscopy is a suitable technique. Here we present an analysis that can help establish whether single-particle experimental conditions are reached. This requires emitter with a sufficiently large dipole moment such as singlewalled carbon nanotubes (SWCNTs) in an ultra-diluted concentration. For SWCNTs, quantum yield (QY) dependency on tube orientation, defects and bundles was reported previously [1-2]. However, additional information on the QY’s density and length dependence is crucial. If a metallic tube (Fig. 1, B) interacts with a semiconducting tube (Fig. 1, A), a short circuit occurs and emission is quenched [3-4]. Even if several semi-conducting SWCNTs’ intersections are present on one tube, the QY is decreased drastically. We model this dependency by fluorescence analysis-based on stochastic simulations, and connect the problem to an analytical solution of Buffon’s needle in the case of isotropically distributed molecules. References: [1] Lee, Andrea J., et al., Nano Lett. 11, Nr. 4: 1636–40 (2011) [2] Tsyboulski, et al., Nano Lett. 5, Nr. 5: 975–79 (2005) [3] Carlson, et al., Acc. Chem. Res. 41, Nr. 2: 235–4 (2008) [4] O’Connell, M. J., et al., Science 297, Nr. 5581: 593–96 (2002)</p

Ultrafast coherent 2D fluorescence micro-spectroscopy on semiconducting carbon nanotubes at room temperature: Breaking the limits for single molecule investigation

Experimental setup for breaking the limits for single molecule investigation with fluorescence-based two-dimensional spectroscopy (F-2DES) Proofing single molecule investigation  F-2DES on individual semiconducting single-walled carbon nanotubes (SWCNTs)  </ul

Ultrafast coherent 2D fluorescence micro-spectroscopy on semiconducting carbon nanotubes at room temperature

Further developments in nano- and molecular electronics would benefit strongly from the possibility of the spatio-temporal evolution of molecular processes. Non-linear ultrafast techniques provide insights into energy transfer pathways, e.g., mediated via electronic coupling. A comprehensive way to observe these dynamics is ultrafast coherent 2D fluorescence micro-spectroscopy [1]. This method is a generalization of transient absorption spectroscopy with frequency resolution both for the pump and the probe step, combined with spatial resolution in an optical microscope. This provides the capability to observe, e.g., inhomogeneous line broading as well as the formation and annihilation dynamics of excitons on the femtosecond timescale. Here, we utilize the third-order 2D signal for monitoring electronic coupling and energy transfer processes in semiconducting single-walled carbon nanotubes. To this end, an LCD-shaped four pulse sequence with 13 fs temporal encoding of each puls is focused through an NA = 1.4 objective and the fluores-cence is detected as a function of inter-pulse time delays and phases. [1] S. Goetz, et al., Optics Express 26, Nr. 4: 3915-25 (2018)</p