DH6T and PCBM wt% loadings in MOF-177 computed from UV-vis calibration curves Using the standard equation from the calibration curves, the molarity of [DH6T] or [PCBM] in each sample can be calculated where y is the absorption intensity of the unknown sample at 433 nm. PCBM content (wt%) = mass of PCBM/ total mass of sample (PCBM + MOF).
Figure S4. Calibration standards curve for DH6T (top) and PCBM (bottom).
UV-Vis absorption spectra were collected using a Unico Spectro-Quest 3802 Spectrometer. UNICO SQ-3802 is a split beam design with 1.8 nm fixed bandwidth and a wavelength range from 190 -1100 nm. It uses a tungsten halogen/deuterium lamp and a solid silicon photodiode detector with a read-out of 320 x 240 pixels backlit LCD. Table S1. Elemental analysis of infiltrated MOF-177.
Additional evidence supporting the dynamic quenching mechanism was obtained from H3BTB and DH6T/PCBM absorption and luminescence spectra in solution. Comparison of these results with those of the guest@MOF-177 analysis is valid, at least on a qualitative basis, because the electronic structure of the H3BTB linker governs the MOF absorption and emission properties, as shown by the similarity of the MOF-177 and BTB/dilute solution luminescence spectra. UV-Vis absorption spectrum of H3BTB in solution with either DH6T or PCBM provide no evidence for the formation of a new ground state complex (SI Figure S8). Rather, the absorption spectra are a superposition of the H3BTB spectrum with that of either DH6T or PCBM. The concentration and temperature dependence of the MOF-177 linker quenching by DH6T (1.0x10-5 M) and PCBM (1.0 x 10-4 M) in solution are also consistent with dynamic quenching. Stern-Volmer analyses (SI Figure S9a) yield Stern–Volmer constants (Ksv) of 2.0 x 105 M-1 for DH6T and KSV = 8.9 x 104 M-1 for PCBM, which are an order of magnitude higher than results reported by Heeger et al and Zheng et al. with other polymer and PCBM systems.44, 45 Similar quenching is observed when the temperature of the mixed components in solution is increased from 0˚C to 70 ˚C at a fixed concentration (SI Figure S9b). At higher temperatures, KSV increases because thermal energy facilitates the diffusion of DH6T or PCBM. The results show that dynamic quenching (rather than static quenching) is responsible for the observed quenching in the infiltrated MOF-177.
Figure S5. Photoluminescence spectra of (a) a solution of H3BTB in DMF with addition of [DH6T] in chloroform; (b) a solution of H3BTB in DMF with addition of [PCBM] in chloroform λex= 345 nm.
Figure S7. UV-Vis absorbance spectra of (left) H3BTB [1.0 x 10-5 M] (blue curve), DH6T [1.0 x 10-5 M] (orange curve), and a mixed solution of H3BTB and DH6T (black curve) in chloroform; and (right) H3BTB [1.0 x 10-5 M] (blue curve), PCBM [1.0 x 10-4 M] (purple curve), and a mixed solution of H3BTB and PCBM (black curve).
Figure S8. (a) Stern-Volmer plot PL0/PL[Solution PL of H3BTB (PL0) without the quencher over the PL of H3BTB with DH6T or PCBM] versus [DH6T] (top) and [PCBM] (bottom). The solid line is the fit obtained from the Stern-Volmer equation. (b) Temperature dependent plot of H3BTB and DH6T (top) and of H3BTB and PCBM (bottom). The concentrations of H3BTB, DH6T, and PCBM are 1.0 x 10-4 M.
Fӧrster resonance energy transfer theory. The degree of spectral overlap between the donor’s emission and acceptor absorption plays a key role in determining if energy transfer can occur. The spectral overlap is defined as
J = ∫ FD (λ) ε (λ) λ4 ∂λ (Eq.S1)
where FD is the normalized donor emission spectrum; and ε (λ) is the extinction coefficient of the acceptor at λ calculated using Aλ = ε c L where Aλ is the absorbance, c is the molar concentration, and L is the path length = 1 cm. The distance between the donor and acceptor determines how efficient the process is since energy transfer is more likely between molecules that are close together than those that are further apart. The donor-acceptor distance is calculated using following equation
where r is the center-to-center distance between the donor and acceptor, R0 is the Förster distance, and Eff is the FRET efficiency. The Förster distance (R0) is the distance at which 50% FRET efficiency occurs and is determined from the following equation
R06 = 8.8 x1023 κ2 n-4 Φd J (Eq. S3)
where κ2 is the dipole orientation factor; n, the refractive index of the medium; Φd, the fluorescence quantum yield of the donor in the absence of the acceptor; and J is the Förster overlap integral, defined by equation 1. κ2 is assumed 2/3 which is appropriate for dynamic random averaging of the donor and acceptor.41 Measurements were done in air, n = 1. Spectral overlap and Förster distance were determined using the PhotoChemCAD software.46 The rate of energy transfer from a donor to an acceptor is given by the Fӧrster expression:
!T ! = 1!D !0!
6 (Eq. S4)
where τD is the decay time of the donor in the absence of acceptor. At this distance when r = R0, the donor emission would be decreased to half its intensity in the absence of acceptors. Once the value of R0 is known, the rate of energy transfer can be calculated.
Guest@MOF-177: Fluorescence quenching and lifetime relations
Table S2. Lifetimes of MOF-177 and Guest@MOF-177 A1
where kr and knr are the radiative and nonradiative decay constants. Using the average luminescent lifetime of MOF-177 (τavg), the radiative decay constant k0 for MOF-177 can be calculated:
20.9 ns = 1/ k0 k0 = 0.05 ns-1
The energy transfer rate constant (keng) is then given by:
τGuest@MOF = 1/(k0 + keng) (Eq.S6)
For example:
13.3 ns = 1/(0.05 + keng) keng = 0.03 ns-1
The quantum yield of energy transfer is then given by:
φeng = keng/(k0 + keng) (Eq.S7)
φeng = 0.03/(0.05 + 0.03) = 0.37 = 37%
The energy-transfer rate constant (1/keng) and φeng values for the infiltrated MOFs are tabulated below.
Table S2. Energy transfer rates and quantum yields of energy transfer of MOF-177 and Guest@MOF-177. τavg (ns) k0 (ns-1) keng (ns-1) 1/keng (ns-1) φeng
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