Control of Exciton Migration Efficiency in Disordered J-Aggregates

Abstract

Using luminescent exciton traps, an efficiency of the exciton migration in J-aggregates of an amphiphilic analogue of pseudoisocyanine (amphi-PIC) dye in solutions, has been investigated. Applying a modified Stern−Volmer equation for analysis of the J-aggregate luminescence quenching by the trap, the quenching of 50% of amphi-PIC J-aggregate luminescence accessible for trapping at the ratio amphi-PIC/DiD = 120:1 has been revealed. To increase the exciton migration efficiency, the J-aggregate structure was improved by the formation of a “J-aggregate−surfactant” complex. The J-aggregate structure improvement is confirmed by the about 3 times increase in the exciton delocalization length that leads to the 1.3 times enhancement in the exciton migration efficiency in solutions with the surfactant. To the best of our knowledge, such a control of the exciton transport parameters in J-aggregates in solutions has not been demonstrated yet.

Manifestation of Exciton-Lattice Interaction in J-Aggregates

“…These rings are composed from 25-30 dye molecules [15]. As was shown earlier, the exciton ST in amphi-PIC J-aggregates strongly depends on the static disorder degree which can be changed, by varying the water content in a DMF=water binary solution [12][13][14]16].…”

“…Recently, we have shown that the presence of cationic surfactant CPB in a DMF=water binary solution at room temperatures causes drastic changes in the optical properties of amphi-PIC J-aggregate: the J-band intensity increases, the J-band becomes narrow, the value of N del grows (from 4 monomers in solutions without CPB up to 11 monomers in solutions with CPB), and the luminescence quantum yield increases slightly (from 0.3 up to 0.5) [15]. In a frozen matrix at the liquid nitrogen temperature, the CPB addition causes the same effect: the J-band becomes more intense and narrower (Dn FWHM ¼ 415 cm À1 as compared with Dn CPB FWHM ¼ 320 cm À1 ) and shifts to a longer wavelength (from k max ¼ 579 nm to k CPB max ¼ 580.5 nm) (Fig.…”

“…The calculation of the exciton-lattice coupling constant g within this approach is complicated due to the uncertainty of the steepness index s. Indeed, an exciton in amphi-PIC J-aggregates is delocalized on a strongly curved segment of the molecular ring consisting on 25-30 molecules [15]. In such case, the value of s should lie between those for 1D and 2D cases and requires separate numerical calculations, similar to [18].…”

Plasmon Controlled Exciton Fluorescence of Molecular Aggregates

“…By estimating Δν fwhm mon = 1220 cm −1 for the main electronic transition of the TC monomer band ( Figure 1, the blue dashed curve), we obtain N c ≈ 4 monomers similarly to the case of strongly disordered amphi-PIC J-aggregates. 26,27 It should be noted that the fluorescence decay curve of TC J-aggregates appeared to be very short with the lifetime less than 20 ps, and consequently, it could not be correctly resolved with our lifetime instrument (see Supporting Information Figure S2). Hence, in the present work the lifetime changes have not been analyzed.…”

Exciton‐Coupled Charge‐Transfer Dynamics in a Porphyrin J‐Aggregate/TiO2 Complex

“…[10, 11b] In addition, the aggregation defect (exciton trap) due to molecular displacement introduces nonradiative loss of photoexcitation energy. [12] These factors collectively restrict porphyrin antenna functionality for interfacial charge-separation phenomenon which also take place in the ultrafast time domain. [13] As a result, porphyrin aggregates are less studied [7,14] due to the complicacy of exciton sensitization.…”