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17 + 3 nm (see Supporting Information Figure $1) and maximum of a plasmonic band at A, = 523 nm (Figure 2). Figure 2. Absorption spectra of Au NPs in the aqueous solution (blue curve) and in the LbL film (red curve).

Figure 2 17 + 3 nm (see Supporting Information Figure $1) and maximum of a plasmonic band at A, = 523 nm (Figure 2). Figure 2. Absorption spectra of Au NPs in the aqueous solution (blue curve) and in the LbL film (red curve).

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There are two main ways to form J-aggregates in polymer films: spin-coating’’~'® and layer-by-layer assembly (LbL).’7~' Unfortunately, both ways cause a significant decrease in J- aggregate fluorescence quantum yield."”'®”? So, special efforts should be made to increase the fluorescence quantum yield of J- aggregates formed in polymer films.
There are two main ways to form J-aggregates in polymer films: spin-coating’’~'® and layer-by-layer assembly (LbL).’7~' Unfortunately, both ways cause a significant decrease in J- aggregate fluorescence quantum yield."”'®”? So, special efforts should be made to increase the fluorescence quantum yield of J- aggregates formed in polymer films.
cm7'), clearly distinguishable H-band (A,,.. = 493 nm), and a monomer band (Amax = 525 nm) (Figure la, blue curve). Figure 1. Absorption (a) and fluorescence (b) spectra and fluorescence decay curves (c) of PIC J-aggregates in an aqueous solution (blue curves) and in a LbL film (red curves). Green curve in section (c) is IRF.
cm7'), clearly distinguishable H-band (A,,.. = 493 nm), and a monomer band (Amax = 525 nm) (Figure la, blue curve). Figure 1. Absorption (a) and fluorescence (b) spectra and fluorescence decay curves (c) of PIC J-aggregates in an aqueous solution (blue curves) and in a LbL film (red curves). Green curve in section (c) is IRF.
Figure 3. Fluorescence spectra (a) and fluorescence enhancement (at Amax = 576 nm) graph (b) of PIC J-aggregates in the LbL films depending on a distance between Au NPs and the J-aggregates. So, we prepared a number of LbL films containing PIC J- aggregates and Au NPs with varying PDDA-—PSS bilayer number between the NPs and the J-aggregate layers and analyzed their fluorescence spectra (Figure 3).
Figure 3. Fluorescence spectra (a) and fluorescence enhancement (at Amax = 576 nm) graph (b) of PIC J-aggregates in the LbL films depending on a distance between Au NPs and the J-aggregates. So, we prepared a number of LbL films containing PIC J- aggregates and Au NPs with varying PDDA-—PSS bilayer number between the NPs and the J-aggregate layers and analyzed their fluorescence spectra (Figure 3).
Figure 4. Absorption spectra (a) and fluorescence decay curves (b) of PIC J-aggregates in the LbL films in the absence (blue curves) and presence (red curves) of Au NPs for the case of five-bilayer spacer. Green curve in section (b) is IRF. The exciton—plasmon interaction in the system under study results in unusual changes in the absorption spectrum and fluorescence decay curve (Figure 4). The comparison of the
Figure 4. Absorption spectra (a) and fluorescence decay curves (b) of PIC J-aggregates in the LbL films in the absence (blue curves) and presence (red curves) of Au NPs for the case of five-bilayer spacer. Green curve in section (b) is IRF. The exciton—plasmon interaction in the system under study results in unusual changes in the absorption spectrum and fluorescence decay curve (Figure 4). The comparison of the
We assume that the plane medium under investigation consists of a large number of elementary composed systems, in which a single NP with radius R locates near the stright J- aggregates, as shown in Figure S. Figure 5. Scheme of the elementary composed system under investigation. The NP is represented by a semicircle. The monomers in a bundle of molecular J-aggregates are shown by the small cycles.
We assume that the plane medium under investigation consists of a large number of elementary composed systems, in which a single NP with radius R locates near the stright J- aggregates, as shown in Figure S. Figure 5. Scheme of the elementary composed system under investigation. The NP is represented by a semicircle. The monomers in a bundle of molecular J-aggregates are shown by the small cycles.
To describe the J-aggregate interaction with the electro- magnetic field, we use a two-level model of the exciton transition. Polarization of the exciton transition of the monomer is P, = d(p, + p*), where d = (d cos @, d sin @). Here ¢ is an angle between the projection of the external field polarization and the z-axis, and d, p,, are the dipole moment and the off-diagonal part of density matrix of 2 two-level system, respectively. Thus, the local field Ege = = (E)”, ES”) acting to the NP is the sum of the external field and the field radiated by the dipoles of the monomers forming the J-aggregate bundles
To describe the J-aggregate interaction with the electro- magnetic field, we use a two-level model of the exciton transition. Polarization of the exciton transition of the monomer is P, = d(p, + p*), where d = (d cos @, d sin @). Here ¢ is an angle between the projection of the external field polarization and the z-axis, and d, p,, are the dipole moment and the off-diagonal part of density matrix of 2 two-level system, respectively. Thus, the local field Ege = = (E)”, ES”) acting to the NP is the sum of the external field and the field radiated by the dipoles of the monomers forming the J-aggregate bundles
Figure 6. Modeling the Au NP absorption spectrum shown in Figure 2b. The dependence Im éyp(A)/(42R°A) on A is depicted by the blue line. Red line shows the corrected form of €yp(A). where constants A@yp = 2.353 eV and hyyp = 0.23 eV are found to be the best fit of the experimental data depicted in Figure 6. We used a quasi-monochromatic presentation of the functions
Figure 6. Modeling the Au NP absorption spectrum shown in Figure 2b. The dependence Im éyp(A)/(42R°A) on A is depicted by the blue line. Red line shows the corrected form of €yp(A). where constants A@yp = 2.353 eV and hyyp = 0.23 eV are found to be the best fit of the experimental data depicted in Figure 6. We used a quasi-monochromatic presentation of the functions
center of a spherical NP is shown in Figure 7. The position of the FI maximum depends on various parameters, including Nj. Figure 7. Dependence of the relative fluorescence intensity on the wavelength and the distance between the J-aggregate and NP.
center of a spherical NP is shown in Figure 7. The position of the FI maximum depends on various parameters, including Nj. Figure 7. Dependence of the relative fluorescence intensity on the wavelength and the distance between the J-aggregate and NP.
Both the maximum of the fluorescence intensity and its position are found to be dependent on the NPs size (Figure 8). Figure 8. Dependence of the relative fluorescence intensity F(a) on the distance between the J-aggregate and the NP for different NP’s radii: R = 7.5 nm (red line), 8.5 nm (blue line), and 9.5 nm (green line). A = 576.8 nm.
Both the maximum of the fluorescence intensity and its position are found to be dependent on the NPs size (Figure 8). Figure 8. Dependence of the relative fluorescence intensity F(a) on the distance between the J-aggregate and the NP for different NP’s radii: R = 7.5 nm (red line), 8.5 nm (blue line), and 9.5 nm (green line). A = 576.8 nm.
Figure 9. Dependence of the relative fluorescence intensity on the distance between the J-aggregate and the NP for a different number of monomers Nj interacting with the NP: Nj = 30 (red line), 40 (blue line), and 50 (green line). 2 = $76.8 nm.
Figure 9. Dependence of the relative fluorescence intensity on the distance between the J-aggregate and the NP for a different number of monomers Nj interacting with the NP: Nj = 30 (red line), 40 (blue line), and 50 (green line). 2 = $76.8 nm.
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