The spectroscopic and electrochemical behavior as well as electrogenerated chemiluminescence (ECL) of a series of donor-π-donor derivatives bearing triphenylamine groups as donor connected to a fluorene, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9'-dimethylfluorene (1), or spirobifluorene core, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9'-spirobifluorene (2) and 2,2',7,7'-tetrakis(4-(N,N-diphenylamino)phen-1-yl)-9,9'-spirobifluorene (3), were investigated. Besides a high photoluminescence (PL) quantum yield in solution (between 81 and 87%), an efficient radical ions annihilation process induces intense greenish blue ECL emission that could be seen with the naked eye. Only the tetrasubstituted spirobifluorene derivative (compound 3) shows weak ECL obtained by a direct annihilation mechanism. Because the energy of the annihilation reaction is higher than the energy required to form the singlet excited state, the S-route could be considered the pathway followed by the ECL process in these molecules. The ECL emissions recorded by direct ion-ion annihilation show two bands compared to the single structureless PL band. The ECL spectra obtained by a coreactant approach using benzoylperoxide as a coreagent show no differences relative to that produced by annihilation, except for an increasing of ECL intensity for all compounds.

Strong-acid dissociation was studied in alcohols. Optical excitation of the cationic photoacid N-methyl-6-hydroxyquinolinium triggers proton transfer to the solvent, which was probed by spectral reconstruction of picosecond fluorescence traces. The process fulfills the classical Eigen-Weller mechanism in two stages: (a) solvent-controlled reversible dissociation inside the solvent shell and (b) barrierless splitting of the encounter complex. This can be appreciated only when fluorescence band integrals are used to monitor the time evolution of the reactant and product concentrations. Band integrals are insensitive to solvent dynamics and report relative concentrations directly. This was demonstrated by first measuring the fluorescence decay of the conjugate base across the full emission band, independently of the proton-transfer reaction. Multiexponential decay curves at single wavelengths result from a dynamic red shift of fluorescence in the course of solvent relaxation, whereas clean single exponential decays are obtained if the band integral is monitored instead. The extent of the shift is consistent with previously reported femtosecond transient absorption measurements, continuum theory of solvatochromism, and molecular properties derived from quantum chemical calculations. In turn, band integrals show clean biexponential decay of the photoacid and triexponential evolution of the conjugate base in the course of the proton transfer to solvent reaction. The dissociation step follows the slowest stage of solvation, which was measured here independently by picosecond fluorescence spectroscopy in five aliphatic alcohols. Also, the rate constant of the encounter-complex splitting stage is compatible with proton diffusion. Thus, for this photoacid, both stages reach the highest possible rates: solvation and diffusion control. Under these conditions, the concentration of the encounter complex is substantial during the earliest nanosecond.

Many complex luminescent emitters such as fluorescent proteins exhibit multiple emitting states that result in rapid fluctuations of their excited-state lifetime. Here, we apply fluorescence lifetime correlation spectroscopy (FLCS) to resolve the photophysical state dynamics of the prototypical fluorescence protein enhanced green fluorescent protein (EGFP). We quantify the microsecond transition rates between its two fluorescent states, which have otherwise highly overlapping emission spectra. We relate these transitions to a room-temperature angstrom-scale rotational isomerism of an amino acid next to its fluorescent center. With this study, we demonstrate the power of FLCS for studying the rapid transition dynamics of a broad range of light-emitting systems with complex multistate photophysics, which cannot be easily done by other methods.

An optical‐tweezers assembly‐line is presented, which has high potential for the construction of complex structures of zeolite L crystals and other microscopic building blocks. Different examples of assembled 2D and 3D zeolite structures are discussed. These include well‐oriented monolayers, microtowers, and angle‐aligned dye‐loaded zeolites, which suggests exciting applications, for example as microscopic polarization sensors.

Holographically shaped light fields can be employed to create highly ordered structures of various kinds of microscopic and nanoscopic particles. M. Woerdemann and co‐workers demonstrate an opticaltweezers assembly‐line that utilizes such light fields in combination with microfluidics and colloidal interactions to construct complex and functional assemblies of Zeolite L crystals, which exhibit exciting photonic properties.