Letter pubs.acs.org/JPCL
Cite This: J. Phys. Chem. Lett. 2018, 9, 3654−3659
Increased Transfer Efficiency from Molecular Photonic Wires on Solid Substrates and Cryogenic Conditions Sebastiań A. Díaz,*,†,⊥ Sean M. Oliver,‡,∥,⊥ David A. Hastman,†,§ Igor L. Medintz,† and Patrick M. Vora*,‡,∥
Downloaded via KAOHSIUNG MEDICAL UNIV on June 21, 2018 at 18:32:26 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
†
Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States ‡ Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, United States ∥ Quantum Materials Center, George Mason University, Fairfax, Virginia 22030, United States § Fischell Department of Bioengineering, University of Maryland, College Park, College Park, Maryland 20742, United States S Supporting Information *
ABSTRACT: Molecular photonic wires (MPWs) are tunable nanophotonic structures capable of capturing and directing light with high transfer efficiencies. DNA-based assembly techniques provide a simple and economical preparation method for MPWs that allows precise positioning of the molecular transfer components. Unfortunately, the longest DNA-based MPWs (∼30 nm) report only modest transfer efficiencies of ∼2% and have not been demonstrated on solid-state platforms. Here, we demonstrate that DNAbased MPWs can be spin-coated in a polymer matrix onto silicon wafers and exhibit a 5fold increase in photonic transfer efficiency over solution-phase MPWs. Cooling these MPWs to 5 K led to further efficiency increases ranging from ∼40 to 240% depending on the length of the MPW. The improvement of MPW energy transport efficiencies advances prospects for their incorporation in a variety of optoelectronics technologies and makes them an ideal test bed for further exploration of nanoscale energy transfer.
M
The longest currently reported DNA-based systems have been able to report only 2% transfer efficiency at slightly above 30 nm in length.18 Additionally, these values were reported at room temperature and in solution. For real translational applications, MPWs will need to work on solid substrates with much higher efficiencies. As such, we have investigated DNAbased MPWs spin-coated onto simple silicon wafers and, when samples were properly prepared, observed a 5-fold increase in transfer efficiency over the same sample measured in solution. Additionally, we utilized a cryogenic stage to investigate the temperature dependence and found that by cooling the MPW we could further increase the efficiency by ∼40−240% depending on the length of the MPW. This remarkable improvement of MPW energy transport efficiencies advances prospects for their incorporation into a variety of optoelectronics technologies and makes them an ideal test bed to explore FRET interactions. The DNA sequences and a list of relevant properties can be found in the Supporting Information. The overall structure has been reported in our previous work.18 In brief, it is based on a double-crossover tile motif19 using two scaffolding strands that are stapled together by shorter complementary strands (joined by ∼10 base pairs on each template). See Figure 1 for a
olecular photonic wires (MPWs) are defined by the collection of individual components positioned so as to allow directed and sequential energy transfer from one end to the other.1,2 Much investigation has gone into MPWs as they are promising components for capturing and directing photonic energy in next-generation optoelectronic systems.3−5 As a scaffolding material, DNA in particular has been a boon to investigators as it allows for the simple, economical, and varied preparation of MPWs with precise positioning of the active transfer components.6,7 DNA MPWs have shown the capability to direct light on the nanoscale with efficiencies above 80% in the 10 nm range.2,8−10 Though multiple transfer mechanisms are feasible (i.e., electron and spin transfer as well as coherent transfer),11−14 the mechanism most often utilized is Förster resonance energy transfer (FRET). As would be expected with FRET mechanisms, the cost of longer MPW is a loss in overall transfer efficiency.15,16 Most DNA-based MPWs are limited to 20 nm in length with single-digit transfer efficiencies. The directional requirement of heterogeneous FRET (different donor and acceptor dye) requires the involvement of many different dyes in an energetically downhill configuration, and unfortunately the available library is quickly depleted and only inefficient dyes remain (low quantum yield (QY), short fluorescence lifetimes, energy sinks).8,17 Recent publications have focused on exploiting homogeneous FRET (same donor and acceptor dye, HomoFRET) as a means of improving the length and efficiency of MPWs.6,18 © XXXX American Chemical Society
Received: March 26, 2018 Accepted: June 12, 2018 Published: June 12, 2018 3654
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
Letter
The Journal of Physical Chemistry Letters
Figure 1. Structure and photophysical characteristics of MPWs. (A) Schematic of DNA MPWs showing R1 and R4 lengths. Blue arrows are FRET steps, with black arrows denoting HomoFRET steps. (B) Extinction coefficients and relative fluorescence emission of dye components in MPWs. (C) Fluorescence spectra of Cy3, A647, R1, C1, and S1 MPWs measured on silica substrate. (D) R1 MPW with QD internal standard and spectral decomposition into components.
temperature of 4 °C was reached. After solution-phase characterization, the internal standard QD was added (see below). The QD was prepared by coating 800 nm emitting organic CuInS/ZnS (NN-Laboratories, Fayetteville, AR) with an amphiphilic polymer as detailed previously.21,22 The polymer provided a thick coating as well as an overall negative charge that minimized interaction with the MPW, therefore not modifying the FRET pathways. This was confirmed by the fact that no changes were observed in the MPW fluorescence spectra upon addition of the QD (see the Supporting Information). The focus within this work was in determining the capability of these MPWs to transfer photonic excitations under varying conditions. As such they were characterized by the end-to-end efficiency (Eee), determined experimentally by considering the output (A647) dye emission as a function of the excitations of the initial dye (Cy3). We then correct using the Cx structures for direct excitation of the A647 as well as for transfer from Cy3.5 dyes excited by the laser.20
schematic and the Supporting Information for greater detail. The short strands were labeled with the dyes that composed the MPW, and equivalent unlabeled strands could be used to create control structures. Cy3 dye was considered the input dye; Cy3.5 was used as the relay dye with a modulatable HomoFRET repeating section, and A647 dye was used as the final readout. Two copies of the input and output dyes were added to maximize initial excitation of the input and transfer efficiency of the relay step, respectively. The relay section was kept as a single dye to minimize traps in the HomoFRET section. Dye separation was 10 base pairs (∼3.4 nm), meant to correspond to ∼0.5 times the Förster distance (R0, the distance at which a FRET pair has 50% transfer efficiency), with a previously determined experimental range of 3.2 ± 0.3 nm.18 The MPWs were modular with an extended central HomoFRET region (Cy3.5) that could extend from 1 Cy3.5 to 6 Cy3.5 repeats. The chosen nomenclature was Rx MPW for the whole MPW (Cy3-Cy3.5-A647), in which x represents the number of repeat (HomoFRET) Cy3.5 sections. As stated, these could range from 1 to 6 repeats. The control structures were labeled Cx (correction x) which had only the final two dyes (□-Cy3.5-A647) to correct for direct excitation and Sx (skip x) which had the first and last dye (Cy3-□-A647) and determined the possibility of transfer directly from the input to the output dye (see the Supporting Information for all schematics).20 Stock solutions of all the labeled and unlabeled DNA strands were prepared as 10 μM solutions in 2.5× PBS (phosphate buffered saline) and 4 mM Mg2+. All samples were annealed in a PCR cycler by heating to 94 °C, holding for 4 min, and then decreasing the temperature by 1 °C every minute until a final
T T T ji Φ − Φ zy ICy3 Eee = 100jjjj Rx T Cx zzzz/ T k QYA647 { QYCy3
ΦTRx
(1)
ΦTCx
The variables and are the photon counts emitted by A647 at a temperature T, in kelvin, from the Rx or Cx MPW, respectively. QY are the fluorescence quantum yields of the dyes at T, and ITCy3 is the photon counts from a MPW that contains only Cy3 at T. The fluorophore QYs are summarized in the Supporting Information. The other measure of transfer efficiency is simply the total photon production of the output (A647). This measure does 3655
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
Letter
The Journal of Physical Chemistry Letters
Figure 2. Spectral comparison of MPWs in varying conditions. (A) Fluorescence spectra of R1 MPW (normalized to Cy3.5 peak) excited at 532 nm in solution or on a solid silicon substrate spin-coated with water (solid) or a PVA matrix (PVA). (B) Fluorescence spectra of PVA samples of MPWs of varying lengths. (C) Eee of the MPWs as a function of MPW length in solution (T = 300 K) or as a PVA sample measured at either 300 or 5 K.
structure as is (diluted in H2O before spin-coating). The fluorescence of the samples could be observed, but there were variances in concentrations both between MPWs as well as oftentimes within sections of the substrate. Addition of the QD internal standard (see above) could be used to correct for differences in concentration. Using overall MPW intensity was not possible as FRET changes may modify peak intensities. As the interaction with the MPW was minimal and the QD concentration added to each sample was consistent (120 nM), the number of photons from the QD should correlate directly with the concentration of the sample on the silica surface. Further improvements in sample preparation were obtained by including a 1% w/v PVA (poly vinyl alcohol Mw 31 000− 50 000, Sigma-Aldrich) solution as the diluting agent for spincoating. This greatly improved the homogeneity of all the samples both within and between different substrates. Additionally, the PVA creates a planar film with a thickness below 50 nm.26 All other conditions remained the same. The addition of PVA had another benefit beyond those observed in sample preparation. As seen in Figure 2A, it greatly increased the Eee of the MPW. As has been seen in other systems, fixing fluorophores on a substrate can quench fluorescence due to exposure to ambient oxygen and modified dielectric environments,27,28 which was observed in the “solid” sample that was diluted with water. In the case of the PVA sample, it had a greater A647 peak, even compared to the solution spectra at the same T. Quantification of the Eee for R1 in solution, on the substrate without PVA, and on the substrate with PVA yielded values of 7.8 ± 1.3, 2.1 ± 1.0, and 39.0 ± 1.6, respectively (the data are shown in Figure 2A). The PVA values were 5 times higher than the solution values and ∼2 times higher than the most efficient equivalent 3-dye MPW reported.18 As the PVA-treated samples were also ∼20 times more efficient than the substrate or water solution without PVA, we chose to prepare all subsequent samples in this manner. The increase of dye QY in the PVA film was consistent through all three dyes (see the Supporting Information for data) and at all T. This effect has been seen in other dyes, such as nile red or diphenylhexatriene, upon integration into PVA films.29,30 In general, these effects are due to changes in environmental polarity, increased rigidity, and inhibition of dimer formation.31 This applies to cyanine dyes as well, as recent studies showed that DNA conjugated Cy3 dimers increased their fluorescence upon increasing the
not consider QY changes or where the MPW was excited and is given simply as ΦTMPW,A647. Spectra were deconstructed into linear combinations of the dye components (see Figure 1D), which were obtained at each T and condition by creating a MPW which contained only the respective dye of interest.23 When the MPW spectra were fit, specific dyes that were not added were fixed as zero. Length is the other parameter of importance, which we report as the distance “travelled” by the excitation, independent of any additional structural length the MPW might present. Transfers that might have occurred in the “backwards direction” within the HomoFRET sections, due to HomoFRET nondirectionality, were not considered as they were not constructive displacements. For simplicity, we used the estimated dsDNA length, which was assumed to be temperature-independent as well as independent of whether it is found in solution or on substrate, which is consistent with the pre-existing literature.24,25 Solution measurements were obtained on a Tecan Infinite M1000 Dual Monochromator Multifunction Microtiter Plate Reader (Tecan, Research Triangle Park, NC), collected with a 532 nm, 400 Hz flash frequency excitation source at 27 °C. Cryogenic fluorescence measurements were performed from 5 to 300 K on a home-built, confocal microscope integrated with a close-cycle cryostat (Montana Instruments Corporation, Bozeman, MT). The excitation source was a 532 nm laser focused through a 0.42 NA long working distance objective with a 50× magnification. The laser spot diameter was determined to be ∼2.4 μm, and the laser power was fixed at 10 μW measured before the objective (estimated 8 μW on sample). To avoid any effects resulting from spatial variations in sample concentration, we raster-scanned the laser over a 50 × 50 μm2 area in 5 μm steps creating a hypermap. The resulting 100 scans were then averaged to remove the effects of spatial variation. Fluorescence signal from the sample was directed to a 500 mm focal length spectrometer with a liquid nitrogen-cooled CCD (Princeton Instruments, Trenton, NJ). The spectrometer and camera were calibrated using a Hg−Ar atomic line source. Samples were spin-coated on plasma-cleaned SiO2/Si substrates with a 90 nm oxide thickness (University Wafer, Boston, MA) at a final MPW concentration of 285 nM. Spincoating was performed by adding 22 μL of solution to the SiO2/Si substrate and then spinning the sample for 10 s at 1000 rpm (500 rpm/s ramp) followed by 30 s at 3000 rpm (1000 rpm/s ramp). Initial experiments were realized with 3656
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
Letter
The Journal of Physical Chemistry Letters
Figure 3. Temperature dependence of MPW Eee. (A) Summed fluorescence spectra of R1 MPW at varying T. (B) Eee of MPWs at different T. (C) Eee values (normalized to 5K) of MPWs at different T. (D) ΦTMPW,A647 (normalized to R1 5K) of MPWs at different T.
solution viscosity with glycerol.32 The general increase of dye QYs is likely correlated to the increased Eee. We note that the detectors in the microscope setup are not normalized for the spectral response of the optics, while the solution-based system is. This was not an issue in the analysis as each system was corrected by control samples taken in the same condition and setup; additionally, the focus of the analysis is based on the relative changes in the systems. As mentioned, the cost for extended length in an MPW is decreased Eee; it has been shown that HomoFRET sections of “good” transfer dyes (good spectral overlap and high QYs) are preferable to MPWs with inferior HeteroFRET passes, even though the HomoFRET section is nondirectional.17,18 The inclusion of a repeat HomoFRET section (Cy3.5 dyes) extended the MPW from 6.8 nm (R1) up to 23.8 nm (R6) in length. The spectra and resulting Eee can be seen in Figure 2B,C. In solution, the Eee decreased in the order 7.8 ± 1.3 (R1), 5.5 ± 0.8 (R2), 2.8 ± 1.2 (R4), and 2.5 ± 1.6 (R6), while the PVA samples at the same temperature decreased as 39.0 ± 1.6 (R1), 16.6 ± 2.4 (R2), 5.0 ± 1.4 (R4), and 0 (R6). For R1, R2, and R4, the Eee was higher on the silica surface while the R6 value was 0 (within the experimental uncertainty). The solution R6 had some residual transfer not observed on solid substrates that may be explained by the long dye-linkers adding flexibility to the system.18 In the case of the solution, the free dye rotation and flexibility allows for residual transfer that is not detected in the more rigid PVA solid-matrix. Tests of the Sx samples showed that some transfer directly from Cy3 to A647 was possible for S1 and S2, though this was less than that observed for full MPWs, but S4 and S6 showed null transfer at all temperatures in the PVA samples. The temperature dependence of fluorescence is a wellknown occurrence; by lowering the T, a suppression of
vibrations and the corresponding phonon-mediated nonradiative relaxation pathways is achieved.33 As such, the QY of the organic dyes increases at lower T. It is also clear from the FRET equations that a higher donor QY should result in higher efficiency.34 An initial test in solution of the R1 spectra (see the Supporting Information for data) clearly demonstrated the decrease in overall emission counts at higher T. More importantly, ample changes in the spectral shape were observed. These arose in part due to changes in FRET, but principally because the melting temperature of the DNA was approached and the MPW dehybridized. Our interest was in increasing the transfer efficiency, we therefore investigated the MPWs at lower (cryogenic) T to observe whether higher Eee could be obtained. Because of the inability to study aqueous solutions at cryogenic temperatures, we focused on PVA spincoated silica substrate samples. Temperature-dependent fluorescence measurements of the PVA samples showed an increase in total photon count with a decrease in T, which correlated with the increased dye QY. Additionally, the peaks were found to blue-shift and sharpen with decreasing T, accompanied by a decrease in intensity of red-shifted shoulder emissions as seen in Figure 3A. As all these changes occurred independent of any FRET modifications within the MPW, it was not sufficient to merely observe peak ratio changes. For all MPW, the complete set of spectra were obtained at each T, the spectra were deconstructed (Figure 1D), and the fits were used in eq 1 to determine Eee. The resulting values can be observed in Figure 3B. As expected, R1 > R2 > R4 > R6 for all T, but of greater relevance was that the T dependence of Eee followed a similar trend for all MPWs. Eee increased as T decreased below freezing from 300 to 250 K, it then held steady within the uncertainty down to 50 K, with another increase observed from there until 3657
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
Letter
The Journal of Physical Chemistry Letters reaching the maximum Eee at 5 K. Slight noise in the trends (particularly R2 and R4 at 100 and 150 K), may have been a result of undetected experimental issues, such as laser focusing and/or shifts in stage positioning. R6 had the distinction of having only a positive Eee at 5 K with all other measurements ≥50 K resulting in 0 Eee values. Of particular interest is the inference offered by Figure 3C, which shows relative changes of Eee. As the length of the MPW increases, the MPW Eee exhibits a larger response over the T range. This is consistent with the random-walk model of HomoFRET and a successful relay being dependent on the efficiency of each individual step.35 Estimates obtained from R4 suggest that the average number of Cy3.5↔Cy3.5 HomoFRET steps an exciton can take before decaying increased from 8 to 17 as the temperature decreased from 300 to 5 K (for a detailed discussion, see the Supporting Information). The average number of available HomoFRET steps is determined by the ratio of the excitation lifetime divided by the transfer rate (for greater discussion, see the Supporting Information), but it appears that the transfer rate is not changed much with T. Therefore, the excitation lifetime of the Cy3.5 would have to slightly more than double at 5 K as compared to 300 K; this is a reasonable number considering the highly static conditions and decrease in molecular movement at 5 K.33 It can be concluded that longer MPWs will be more susceptible to Eee increases by lowering the T as the relatively small increase in each individual transfer step has a multiplicative effect for MPWs with many relay steps, be they Hetero or HomoFRET. Further still, because of the randomwalk nature of HomoFRET sections and the pass/no-pass component they add to the relay, these should be even more prone to improvements by cooling. This is seen in that R6 has null transfer except at 5 K, and R1 and R2 increase the Eee 39% and 43%, respectively, but R4 has an increase of ∼240%. If we wish to look at the MPW as merely an antennae or light harvester whose aim is to optimize output of the final emitter, an approach with possible applications in artificial photosynthesis or controlled photochemistry, then the parameter of interest is the ΦTMPW,A647 (total photons emitted by A647) shown in Figure 3D. For simplicity the data has been normalized to R1 5K, and it can be observed that the light harvesting is more efficient at lower T for all MPWs. In general, an approximate 2-fold increase is obtained for all MPWs as the T decreases, this is expected considering the increase in Eee (seen in Figure 3B) as well as in the QY of the A647. Further still it is clear that the longer MPWs (R4 and R6) are more efficient at harvesting light, because of the considerable increase in absorption cross-section, than the shorter R1 and R2. Perhaps slightly more surprising, R1 > R2 and R4 > R6 even though the absorption favors the longer MPWs,; this is most likely due to the diminishing returns of increasing photon absorption at the cost of transfer efficiency, which was recently discussed for more expansive dendrimeric light harvesters.20 We have shown that the transition from solution to surface, or solid, phase can increase the transfer efficiency of DNAbased MPW. When properly prepared, in this case as simple as spin-coating with PVA, the efficiency increased by ∼5-fold. The use of cryogenic stages confirmed that further efficiencies can be achieved by cooling the MPW. Environments of 5 K allow for efficiency increases of ∼40% in the shorter MPWs, with longer MPWs demonstrating even greater increases up to 240%, with the longest MPW (R6) only showing transfer at 5 K. Along with chemical and structural design optimization,
solid-phase integration will be a crucial stepping-stone in improving MPW energy transport efficiencies for their incorporation into new photonic technologies. Additionally, this methodology suggests itself as an ideal system to explore FRET interactions within complex dye−DNA structures and how environment effects transfer efficiency.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpclett.8b00931.
■
DNA sequences, a detailed description of MPWs, MPW formation efficiency, QD and MPW interaction, fluorophore QYs, comparison of H2O and PVA spincoated samples, variance over spatially resolved fluorescence maps, comparison of Rx and Sx MPWs, random-walk and lifetime discussion, and MPW dehybridization (PDF)
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Sebastián A. Díaz: 0000-0002-5568-0512 Igor L. Medintz: 0000-0002-8902-4687 Patrick M. Vora: 0000-0003-3967-8137 Author Contributions ⊥
S.A.D. and S.M.O. contributed equally to this work.
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS S.A.D. acknowledges a Karles Research Fellowship awarded by the NISE initiative. The authors acknowledge the NRL Nanosciences Institute and a LUCI project through the OSD in support of the VBFF. S.M.O. and P.M.V. acknowledge support from the George Mason University Presidential Scholar Fellowship Program.
■
REFERENCES
(1) Burley, G. A. DNA-Based Construction of Molecular Photonic Devices. In DNA in Supramolecular Chemistry and Nanotechnology; John Wiley & Sons, Ltd, 2014; pp 1−21. (2) Wagner, R. W.; Lindsey, J. S. A Molecular Photonic Wire. J. Am. Chem. Soc. 1994, 116, 9759−9760. (3) Mamangun, D.; Navarathne, D.; Sotzing, G. A.; Lombardi, J. P.; Bartsch, C. M.; Heckman, E. M.; Singh, K. M.; Grote, J. G.; Nelson, T. R. Optoelectronics Using DNA as a Template for Dyes; SPIE NanoScience + Engineering; SPIE: San Diego, CA, 2012; p 6. (4) Li, Y.; Liu, T.; Liu, H.; Tian, M.-Z.; Li, Y. Self-Assembly of Intramolecular Charge-Transfer Compounds into Functional Molecular Systems. Acc. Chem. Res. 2014, 47, 1186−1198. (5) Wohlgamuth, C. H.; McWilliams, M. A.; Slinker, J. D. DNA as a Molecular Wire: Distance and Sequence Dependence. Anal. Chem. 2013, 85, 8634−8640. (6) Nicoli, F.; Barth, A.; Bae, W.; Neukirchinger, F.; Crevenna, A. H.; Lamb, D. C.; Liedl, T. Directional Photonic Wire Mediated by Homo-Förster Resonance Energy Transfer on a DNA Origami Platform. ACS Nano 2017, 11, 11264−11272.
3658
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
Letter
The Journal of Physical Chemistry Letters (7) Hannestad, J. K.; Gerrard, S. R.; Brown, T.; Albinsson, B. SelfAssembled DNA-Based Fluorescence Waveguide with Selectable Output. Small 2011, 7, 3178−3185. (8) Spillmann, C. M.; Buckhout-White, S.; Oh, E.; Goldman, E. R.; Ancona, M. G.; Medintz, I. L. Extending FRET Cascades on Linear DNA Photonic Wires. Chem. Commun. 2014, 50, 7246−7249. (9) Buckhout-White, S.; Spillmann, C. M.; Algar, W. R.; Khachatrian, A.; Melinger, J. S.; Goldman, E. R.; Ancona, M. G.; Medintz, I. L. Assembling Programmable FRET-Based Photonic Networks Using Designer DNA Scaffolds. Nat. Commun. 2014, 5, 5615. (10) Hannestad, J. K.; Sandin, P.; Albinsson, B. Self-Assembled DNA Photonic Wire for Long-Range Energy Transfer. J. Am. Chem. Soc. 2008, 130, 15889−15895. (11) Cunningham, P. D.; Bricker, W. P.; Díaz, S. A.; Medintz, I. L.; Bathe, M.; Melinger, J. S. Optical Determination of the Electronic Coupling and Intercalation Geometry of Thiazole Orange Homodimer in DNA. J. Chem. Phys. 2017, 147, 055101. (12) Banal, J. L.; Kondo, T.; Veneziano, R.; Bathe, M.; SchlauCohen, G. S. Photophysics of J-Aggregate-Mediated Energy Transfer on DNA. J. Phys. Chem. Lett. 2017, 8, 5827−5833. (13) Weiss, E. A.; Ahrens, M. J.; Sinks, L. E.; Gusev, A. V.; Ratner, M. A.; Wasielewski, M. R. Making a Molecular Wire: Charge and Spin Transport through Para-Phenylene Oligomers. J. Am. Chem. Soc. 2004, 126, 5577−5584. (14) Boulais, É .; Sawaya, N. P. D.; Veneziano, R.; Andreoni, A.; Banal, J. L.; Kondo, T.; Mandal, S.; Lin, S.; Schlau-Cohen, G. S.; Woodbury, N. W.; Yan, H.; Aspuru-Guzik, A.; Bathe, M. Programmed Coherent Coupling in a Synthetic DNA-Based Excitonic Circuit. Nat. Mater. 2017, 17, 159. (15) Spillmann, C. M.; Ancona, M. G.; Buckhout-White, S.; Algar, W. R.; Stewart, M. H.; Susumu, K.; Huston, A. L.; Goldman, E. R.; Medintz, I. L. Achieving Effective Terminal Exciton Delivery in Quantum Dot Antenna-Sensitized Multistep DNA Photonic Wires. ACS Nano 2013, 7, 7101−7118. (16) Moroz, P.; Klein, W. P.; Akers, K.; Vore, A.; Kholmicheva, N.; Razgoniaeva, N.; Khon, D.; Díaz, S. A.; Medintz, I. L.; Zamkov, M. Lifting the Spectral Crosstalk in Multifluorophore Assemblies. J. Phys. Chem. C 2017, 121, 26226−26232. (17) Díaz, S. A.; Buckhout-White, S.; Brown, C. W.; Samanta, A.; Klein, W. P.; Ancona, M. G.; Dwyer, C. L.; Goldman, E. R.; Melinger, J. S.; Cunningham, P. D.; Spillmann, C. M.; Medintz, I. L. Using DNA Nanostructures to Harvest Light and Create Energy Transfer and Harvesting Systems; SPIE BioPhotonics Australasia; SPIE: Adelaide, Australia, 2016; p 10. (18) Díaz, S. A.; Buckhout-White, S.; Ancona, M. G.; Spillmann, C. M.; Goldman, E. R.; Melinger, J. S.; Medintz, I. L. Extending DNABased Molecular Photonic Wires with Homogeneous Fö rster Resonance Energy Transfer. Adv. Opt. Mater. 2016, 4, 399−412. (19) Fu, T. J.; Seeman, N. C. DNA Double-Crossover Molecules. Biochemistry 1993, 32, 3211−20. (20) Klein, W. P.; Díaz, S. A.; Buckhout-White, S.; Melinger, J. S.; Cunningham, P. D.; Goldman, E. R.; Ancona, M. G.; Kuang, W.; Medintz, I. L. Utilizing HomoFRET to Extend DNA-Scaffolded Photonic Networks and Increase Light-Harvesting Capability. Adv. Opt. Mater. 2018, 6, 1700679. (21) Díaz, S. A.; Gillanders, F.; Susumu, K.; Oh, E.; Medintz, I. L.; Jovin, T. M. Water-Soluble, Thermostable, Photomodulated ColorSwitching Quantum Dots. Chem. - Eur. J. 2017, 23, 263−267. (22) Azcarate, J. C.; Díaz, S. A.; Fauerbach, J. A.; Gillanders, F.; Rubert, A. A.; Jares-Erijman, E. A.; Jovin, T. M.; Fonticelli, M. H. ESIPT and FRET Probes for Monitoring Nanoparticle Polymer Coating Stability. Nanoscale 2017, 9, 8647−8656. (23) Ae Uv-Vis-Ir, Spectral Software 1.2; Fluortools; www.fluortools. com. (24) Luzzati, V.; Mathis, A.; Masson, F.; Witz, J. Structure Transitions Observed in DNA and Poly A in Solution as a Function of Temperature and pH. J. Mol. Biol. 1964, 10, 28−41.
(25) Sánchez-Mosteiro, G.; van Dijk, E. M. H. P.; Hernando, J.; Heilemann, M.; Tinnefeld, P.; Sauer, M.; Koberlin, F.; Patting, M.; Wahl, M.; Erdmann, R.; van Hulst, N. F.; García-Parajó, M. F. DNABased Molecular Wires: Multiple Emission Pathways of Individual Constructs. J. Phys. Chem. B 2006, 110, 26349−26353. (26) Salim, B.; Jaisree Meenaa Pria, K. N. J.; Alagappan, M.; Kandaswamy, A. Fabrication of Poly (Methyl Methacrylate) and Poly(Vinyl Alcohol) Thin Film Capacitors on Flexible Substrates. IOP Conf. Ser.: Mater. Sci. Eng. 2015, 99, 012026. (27) Peterson, J. I.; Fitzgerald, R. V. New Technique of Surface Flow Visualization Based on Oxygen Quenching of Fluorescence. Rev. Sci. Instrum. 1980, 51, 670−671. (28) Vyshkvarko, A. A.; Kiselev, V. F.; Paschenko, V. Z.; Plotnikov, G. S. Luminescence Quenching Kinetics of Photo-Excited Adsorbed Dye Molecules in Insulators and Insulator-Semiconductor Structures. J. Lumin. 1991, 47, 327−334. (29) Dutta, A. K.; Kamada, K.; Ohta, K. Spectroscopic Studies of Nile Red in Organic Solvents and Polymers. J. Photochem. Photobiol., A 1996, 93, 57−64. (30) Kawski, A.; Kubicki, A.; Kukliński, B.; Gryczyński, I. Unusual Absorption and Fluorescence Properties of 1,6-Diphenyl- 1,3,5Hexatriene in Poly(Vinyl Alcohol) Film. J. Photochem. Photobiol., A 1993, 71, 161−167. (31) Hou, Y.; Bardo, A. M.; Martinez, C.; Higgins, D. A. Characterization of Molecular Scale Environments in Polymer Films by Single Molecule Spectroscopy. J. Phys. Chem. B 2000, 104, 212− 219. (32) Cunningham, P. D.; Kim, Y. C.; Díaz, S. A.; Buckhout-White, S.; Mathur, D.; Medintz, I. L.; Melinger, J. S. Optical Properties of Vibronically Coupled Cy3 Dimers on DNA Scaffolds. J. Phys. Chem. B 2018, 122, 5020. (33) Aramendia, P. F.; Negri, R. M.; Roman, E. S. Temperature Dependence of Fluorescence and Photoisomerization in Symmetric Carbocyanines. Influence of Medium Viscosity and Molecular Structure. J. Phys. Chem. 1994, 98, 3165−3173. (34) Lakowicz, J. R. Principles of Fluorescence Spectroscopy; Springer: New York, 2006. (35) Hardin, J. C.; Sweet, A. L. Moments of the Time to Absorption in the Random Walk between a Reflecting and an Absorbing Barrier. SIAM Rev. 1970, 12, 140−142.
3659
DOI: 10.1021/acs.jpclett.8b00931 J. Phys. Chem. Lett. 2018, 9, 3654−3659
