Correlative microscopy of morphology and luminescence of Cu porphyrin aggregates

Abstract

Transfer of energy and information through molecule aggregates requires as one important building block anisotropic, cable-like structures. Knowledge on the spatial correlation of luminescence and morphology represents a prerequisite in the understanding of internal processes and will be important for architecting suitable landscapes. In this context we study the morphology, fluorescence and phosphorescence of molecule aggregate structures on surfaces in a spatially correlative way. We consider as two morphologies, lengthy strands and isotropic islands. It turns out that phosphorescence is quite strong compared to fluorescence and the spatial variation of the observed intensities is largely in line with the amount of dye. However in proportion, the strands exhibit more fluorescence than the isotropic islands suggesting weaker non-radiative channels. The ratio fluorescence to phosphorescence appears to be correlated with the degree of aggregation or internal order. The heights at which luminescence saturates is explained in the context of attenuation and emission multireflection, inside the dye. This is supported by correlative photoemission electron microscopy which is more sensitive to the surface region. The lengthy structures exhibit a pronounced polarization dependence of the luminescence with a relative dichroism up to about 60%, revealing substantial perpendicular orientation preference of the molecules with respect to the substrate and parallel with respect to the strands.

Active sites modulation with Runge–Gross theorem: CO2 capture by porphyrinic metal–organic frameworks at excited states

“…Owing to forbidden transition between the FES (i.e., T 1 state for a closed‐shell system) and the GS (i.e., S 0 state for a closed‐shell system), there would be a long‐life FES for porphyrins and the derived MOFs 22 . Moreover, the porphyrin aggregates like MOFs would have more abundant stable FESs due to the increased probabilities of radiationless transitions 23,24 . The phosphor decay profiles of the solid PCN‐H and PCN‐ M s tested at ambient temperature demonstrate that the effective lifetimes of their FESs averagely persist for more than 40 μs (Figure 1C,D), 25–27 which is durable enough to meet the molecular adsorption equilibrium over the modulated ASs.…”

“…22 Moreover, the porphyrin aggregates like MOFs would have more abundant stable FESs due to the increased probabilities of radiationless transitions. 23,24 The phosphor decay profiles of the solid PCN-H and PCN-Ms tested at ambient temperature demonstrate that the effective lifetimes of their FESs averagely persist for more than 40 μs (Figure 1C,D), [25][26][27] which is durable enough to meet the molecular adsorption equilibrium over the modulated ASs. This means that, once the external excited light source is continuous, abundant FES-modulated ASs should emerge and work, and the in situ application of the FESs must be possible.…”

The pH Influence on the Water-Splitting Electrocatalytic Activity of Graphite Electrodes Modified with Symmetrically Substituted Metalloporphyrins

“…It has been reported that complex porphyrin architectures comprise simpler ones, resulting from the side-by-side or face-to-face positioning of the molecules [ 50 ]. In the case of 3D aggregates—such as the ones observed for this specimen—these two types of assemblies, referred to as J-type and H-type arrangements, are both present [ 51 ].…”