Investigation of Morphology‐Controlled Ultrafast Relaxation Processes of Aggregated Porphyrin

Abstract

Here, we have synthesized rod and flake shaped morphology of porphyrin aggregates from 5, 10, 15, 20-tetra (4-n-octyloxyphenyl) porphyrin (4-opTPP) molecule which are evident from scanning electron microscopy (SEM). The formation of J-type aggregation is evident from steady state and time-resolved fluorescence spectroscopic studies. Ultrafast transient absorption spectroscopic studies reveal that the excited state lifetime is controlled by the morphology and the time constant for S 1 ! S 0 relaxation changes from 3.05 ps to 744 ps with changing the shape from rod to flake, respectively. In spite of similar exciton coupling energy in both the aggregates, the flake shaped aggregates undergo a faster exciton relaxation process and the non-radiative relaxation channels are found to depend on the shape of aggregates. The fundamental understanding of morphology controlled ultrafast relaxation processes of aggregated porphyrin is important for designing efficient light harvesting devices.

Biomimetic Approach toward Visible Light-Driven Hydrogen Generation Based on a Porphyrin-Based Coordination Polymer Gel

“…Photoexcitation was done with 400 nm laser flashes in the duration of ∼40 fs pulses. Similar to Ru-TPY-POR CPG reported in the previous study, the Fe 2 @CPG also displayed positive bands between 500 and 750 nm (Figure S13), ascribed to the characteristic of porphyrin triplet like absorption . Notably, the excited state dynamics of Fe 2 @CPG showed a fast decay component of ∼1.2 ps (Figure e), which is significantly shorter as compared to Ru-TPY-POR CPG (∼40 ps) and TPY-POR OG (∼255 ps), which are estimated in our previous report .…”

“…Similar to Ru-TPY-POR CPG reported in the previous study, 47 the Fe 2 @CPG also displayed positive bands between 500 and 750 nm (Figure S13), ascribed to the characteristic of porphyrin triplet like absorption. 58 Notably, the excited state dynamics of Fe 2 @CPG showed a fast decay component of ∼1.2 ps (Figure 4e), which is significantly shorter as compared to Ru-TPY-POR CPG (∼40 ps) and TPY-POR OG (∼255 ps), which are estimated in our previous report. 47 These results indicate that the Fe 2 @CPG hybrid gel system suppressed the charge recombination process and provided facile electron transfer to the catalytic sites.…”

Visible‐Light‐Driven Photocatalytic CO2 Reduction to CO/CH4 Using a Metal–Organic “Soft” Coordination Polymer Gel

“…The 40 ps component can be assigned to the fast singlet excited state quenching of the porphyrin unit. The long‐lived component with >3 ns can be attributed to the ultrafast generation of characteristic porphyrin triplet‐like absorption (Figure 5a) [27] . Comparing these dynamics to the pure TPY‐POR OG , we find that similar singlet and triplet features are observed at 500–750 nm although the dynamics of decay are much slower (Figure 5d).…”

Visible‐Light‐Driven Photocatalytic CO2 Reduction to CO/CH4 Using a Metal–Organic “Soft” Coordination Polymer Gel

“…The long-lived component with > 3 ns can be attributed to the ultrafast generation of characteristic porphyrin tripletlike absorption (Figure 5a). [27] Comparing these dynamics to the pure TPY-POR OG, we find that similar singlet and triplet features are observed at 500-750 nm although the dynamics of decay are much slower (Figure 5d). We find that the singlet excited state of TPY-POR OG decays with two time-constants of ~255 ps and > 3 ns, respectively.…”