Tuning the Carbon Nanotube Selectivity Optimizing Reduction Potentials and Distortion Angles in Perylenediimides

Transcription

1 Tuning the Carbon Nanotube Selectivity Optimizing Reduction Potentials and Distortion Angles in Perylenediimides Peter W. Münich,, Christoph Schierl,, Konstantin Dirian, Michel Volland, Stefan Bauroth,, Leonie Wibmer, Zois Syrgiannis, # Timothy Clark, Maurizio Prato, #,, Dirk M. Guldi Department of Chemistry and Pharmacy and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, 918 Erlangen, Germany # Center of Excellence for Nanostructured Materials, Dipartimento di Scienze Chimiche e Farmaceutiche, INSTM unit of Trieste, University of Trieste, Piazzale Europa 1, 127 Trieste, Italy Computer-Chemie-Centrum, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstr. 2, 912 Erlangen, Germany Carbon Nanobiotechnology Laboratory, CIC biomagune, Paseo de Miramón 182, 29 Donostia-San Sebastian (Spain) Basque Fdn Sci, Ikerbasque, Bilbao 81, Spain Experimental Section Synthetic procedures PDIs 1- were synthesized according to the procedure described in reference 1. Preparation of CoMoCAT-SWCNT hybrids For the creation of stable CoMoCAT-SWCNT hybrids, typically solid CoMoCAT-SWCNT were added to solutions of PDI derivatives 1- (x1 - M) in D2O followed by several sonication and centrifugation (kg) steps. Materials and methods Chemicals SDBS was purchased from Sigma-Aldrich and used without further purification. D2O was purchased from Deutero. CoMoCAT-SWCNT with a broad chirality range (.7-.9 nm in diameter, >77% of carbon as SWCNT) were purchased from Sigma Aldrich. Spectroscopy UV/Vis/nIR absorption measurements were performed using either a Perkin Elmer Lambda 2 spectrometer or a Cary spectrometer (Varian). Dependent on the optical density either 1x1mm or 1x2mm quarz cuvettes were used. NIR fluorescence measurements were done with a FluoroLog spectrometer from HORIBA Yobin Yvon using a W Xenon lamp and a Symphony InGaAs array in combination with an ihr2 imaging spectrometer. For emission spectroscopy in the visible range, a Fluoromax spectrometer from HORIBA Yobin Yvon was used. Femtosecond transient absorption measurements were performed with the transient absorption pump probe system HELIOS from Ultrafast Systems. To generate laser pulses with a pulse width of 1 fs and a wavelength of 87 nm a CPA-211 titanium:sapphire laser system from Clark-MXR Inc was utilized. 87 nm excitation pulses were generated by second harmonic generation. All measurements were carried out in 2 mm OS quarz cuvettes. 1

2 Raman spectroscopy / microscopy For a typical Raman measurement a WiTec alphar confocal Raman microscope was used. Samples were deposited onto silica wafers by drop casting. A HeNe Laser with an output of 6 nm served was used for sample excitation. Transmission Electron Microscopy Transmission electron microscopy was conducted on a Zeiss Leo EM912 Omega with an acceleration voltage of 8 kv. Specimen were prepared by drop casting a suspension of 1/SWCNT, 2/SWCNT or /SWCNT on either Lacey Carbon supported ultrathin carbon/copper or Lacey Carbon/Copper grids. The sample grids were dried at C for min, put in a D2O bath for min, and finally dried again for min prior to microscoping. Electrochemistry and Spectroelectrochemistry Spectroelectrochemical measurements were done in a home-made three neck glass cell with a three-electrode setup comprised of a platinum mesh as working electrode, a Ag-wire as pseudo reference electrode, and a platinum wire as counter electrode. To control the applied potentials a Metrohm PGStat 11 was used. Electrochemical measurements were performed using a Methrom µautlobabfraiii equipped with an internal impedance unit. The latter was controlled by the software NOVA 1.1 provided by Methrom. Measurements were performed in a homemade cell (V= ml) with a glassy carbon working electrode (mm diameter), an Ag/AgCl (M NaCl) reference electrode and a Pt wire serving as counter electrode. NOVA 1.1 from Methrom served as control software. Measurements were performed in H2O at a ph of 2.. The latter has been adjusted by the dropwise addition of HCl. Atomic force Microscopy Atomic force microscopy measurements were conducted with a JPK Nanowizard Nanoscience microscope holding an ACTA cantilever from Applied Nanostructures APPNANO with a resonance frequency of khz and a tip radius below 1 nm. Samples were drop casted onto silica wafers. 2

3 Supplementary Section 7.x1-6 6.x1-6 - (-.8) x1-6 - (-.8) x1-6 7.x1-6 6.x1-6.x1-6 Current / A.x1-6.x1-6 Current / A.x1-6.x1-6 Current /.x1 A -6.8-(-.8) / PDI / PDI-.x1-6.x1-6 2.x1-6 2.x1-6 2.x1-6 1.x1-6 1.x1-6 1.x Applied Potential / V vs Ag/AgCl Applied Potential / V vs Ag/AgCl Applied Potential / V vs Ag/AgCl Figure S1: Left: Square wave voltammogram of 1. Middle: Square wave voltammogram of 2. Right: Square wave voltammogram of. All voltammograms were recorded in H2O (ph 2. adjusted by HCl) vs Ag/AgCl. Arrows indicate scan direction OD / norm.. Emission / norm Figure S1. Left: Normalized absorption spectra of 1 (black), 2 (red) and (grey) recorded in D2O. Right: Normalized emission spectra of 1 (black), 2 (red) and (grey) recorded following 8 nm excitation in D2O OD / norm I / norm. OD / norm I / norm. OD / norm I / norm Figure S: Left: Normalized spectra of 1. Middle: Normalized spectra of 2. Right: Normalized spectra of. Shown are the normalized absorption (black), excitation (grey), and fluorescence (red) recorded in D2O nm 9 nm Time / ps Figure S: Left: Differential absorption spectra of 1 obtained upon femto second flash photolysis (λex = 87 nm) in D2O with different time delays from 2 (red) to 7 ps (violet). Right: Corresponding time absorption profiles at 2 nm (black) and 9 nm (red).

4 nm 6 nm Time / ps Figure S: Left: Differential absorption spectra of 2 obtained upon femto second flash photolysis (λex = 87 nm) in D2O with different time delays from 2 (red) to 7 ps (violet). Right: Corresponding time absorption profiles at 2 nm (black) and 6 nm (red) nm 121 nm Figure S6: Left: Differential absorption spectra of obtained upon femto second flash photolysis (λex = 87 nm) in D2O with different time delays from 2 (red) to 7 ps (violet). Right: Corresponding time absorption profiles at 8 nm (black) and 121 nm (red) OD OD OD Figure S7: Left: UV/Vis/nIR absorption spectra of 1 (red) and 1/SWCNT (black). Middle: UV/Vis/nIR absorption spectra of 2 (red) and 2/SWCNT (black). Right: UV/Vis/nIR absorption spectra of (red) and /SWCNT (black). The insets show a zoom into the S11 region. All Spectra were recorded in D2O. 9.x1 6 2.x1 7 7x1 7 7.x x1 7 6x1 7 6.x1 6 Emission /.x1 6.x1 6 1.x x1 7 Emission / 8.x1 6.x1 6 x1 7 x1 Emission / 7 x1 7 2x1 7 1x Figure S8: Left: Fluorescence spectra of 1 (red) and 1/SWCNT (black). Middle: Fluorescence spectra of 2 (red) and 2/SWCNT (black). Right: Fluorescence spectra of (red) and /SWCNT (black). All Spectra were recorded in D2O following 7 nm excitation.

5 a b c d Figure S9: TEM images of 1/SWCNT drop casted on either Lacey Carbon supported ultrathin carbon/copper (a-c) or Lacey Carbon/Copper (d) grids, washed with D2O. The scale bars are 2 nm (a), 1 nm (b, c), or 2 nm (d). (b) shows a magnification of the marked space in (a). (d) shows a free-standing SWCNT. The thin lines are the desired well unbundled SWCNTs. The thicker dark structures are the supporting Lacey Carbon film. The several nm thick spots are either PDI aggregates, impurities on the films, which are also present on untreated grids and could not be removed by washing with D2O, or a combination of both. a b c d Figure S1: TEM images of 2/SWCNT drop casted on Lacey Carbon supported ultrathin carbon/copper grids, washed with D2O. The scale bars are 2 nm (a, b), or 1 nm (c, d). The thin lines are the desired well unbundled SWCNTs. The thicker dark structures are the supporting Lacey Carbon film. The several nm thick spots are either PDI aggregates, impurities on the films, which are also present on untreated grids and could not be removed by washing with D2O, or a combination of both. a b c d Figure S11: TEM images of /SWCNT drop casted on Lacey Carbon supported ultrathin carbon/copper grids, washed with D2O. (b) shows a magnification of the marked space in (a). The scale bars are 1 nm (a-d). The thin lines are the desired well unbundled SWCNTs. The thicker dark structures are the supporting Lacey Carbon film. The several nm thick spots are either PDI aggregates, impurities on the films, which are also present on untreated grids and could not be removed by washing with D2O, or a combination of both.

6 Figure S12: Left: Overview AFM image of 1/SWCNT drop casted onto silicon wafers. Middle: Zoom-in AFM image of 1/SWCNT. Right: Exemplary height profile of 1/SWCNT. Figure S1: Left: Overview AFM image of 2/SWCNT drop casted onto silicon wafers. Middle: Zoom-in AFM image of 2/SWCNT. Right: Exemplary height profile of 2/SWCNT. Figure S1: Left: Overview AFM image of /SWCNT drop casted onto silicon wafers. Middle: Zoom-in AFM image of /SWCNT. Right: Exemplary height profile of /SWCNT. 6

7 Intensity / norm Intensity / norm Raman shift / cm Raman shift / cm -1 Figure S1: Left: Normalized averaged Raman spectra of 1/SWCNT (black), 2/SWCNT (red), and /SWCNT (grey) showing the D- and G-mode regions. The inset displays the maxima of the G-mode. Right: Normalized averaged Raman spectra of 1/SWCNT (black), 2/SWCNT (red), and /SWCNT (grey) showing the 2D- mode region. 7

8 Replacement Titrations The sample preparation for replacement of 1- from their respective SWCNT hybrids involved the addition of.2 mg pristine SWCNTs to ml of a 1- M solution of 1-. After an initial sonication period of 2 min an absorption spectrum of the resulting homogenous, yet metastable dispersion, was taken as reference point for the uptake determination. Subsequently, the samples were centrifuged for 1 minutes at kg followed by a separation of the supernatant from any precipitated material in three cycles for every sample to yield stable dispersions of 1/SWCNT, 2/SWCNT or /SWCNT. In each case it was possible to determine the exact uptake of SWCNTs into the solution by a simple comparison of the absorption spectrum before and after the centrifugation cycles. Starting from the prepared samples, which show an almost quantitative quenching of SWCNT fluorescence, we added a. M solution of cetyltrimethylammoniumbromid (CTAB) in D2O as cationic surfactant in -1 µl steps. Background emission stemming from free 1 and in the dispersion was subtracted for the respective 7 nm excitation spectra of 1/SWCNT and /SWCNT Emission / 6 Corrected Emission / Emission / 6 Emission / Figure S16: Top left: Fluorescence spectra of 1/SWCNT following 7 nm excitation with increasing amounts of CTAB added. Top right: Fluorescence spectra of 1/SWCNT following 66 nm with increasing amounts of CTAB added. The legend indicates the ratio of CTAB to SWCNT. Bottom left: Corresponding fluorescence spectra of (6,) SWCNTs derived from applying multiple gauss fits to the upper spectra. Bottom right: Corresponding fluorescence spectra of (7,) and (7,6) SWCNTs derived from applying multiple gauss fits to the upper spectra Emission / Emission / Emission / 16 Emission / Figure S17: Top left: Fluorescence spectra of 2/SWCNT following 7 nm excitation with increasing amounts of CTAB added. Top right: Fluorescence spectra of 2/SWCNT following 66 nm with increasing amounts of CTAB added. The legend indicates the ratio of CTAB to SWCNT. Bottom left: Corresponding fluorescence spectra of (6,) SWCNTs derived from applying multiple gauss fits to the upper spectra. Bottom right: Corresponding fluorescence spectra of (7,) and (7,6) SWCNTs derived from applying multiple gauss fits to the upper spectra. 8

9 Gauss Model y=y + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2) Equation Peak1( ) Peak2( ) y xc w A Plot Adj. R-Square Emission / 8 Emission / R-Square(COD) Reduced Chi-Sqr Emission / Corrected Emission / Figure S18: Top left: Fluorescence spectra of /SWCNT following 7 nm excitation with increasing amounts of CTAB added. Top right: Fluorescence spectra of /SWCNT following 66 nm with increasing amounts of CTAB added. The legend indicates the ratio of CTAB to SWCNT. Bottom left: Corresponding fluorescence spectra of (6,) SWCNTs derived from applying multiple gauss fits to the upper spectra. Bottom right: Corresponding fluorescence spectra of (7,) and (7,6) SWCNTs derived from applying multiple gauss fits to the upper spectra Emission / norm Figure S19: Plot of the emission recovery vs. the [CTAB]/[SWCNT] ratio in 2/SWCNT dependent on the SWCNT chirality, i.e. 6, (black cycles and traces), 7, (grey cycles and traces), and 7,6 (red cycles and traces) SWCNTs. 9

10 Molecular Modelling As the dimerization energy of the supramolecular binding between various PDI s and the SWCNT s is strongly dependent on the binding geometry two different approaches were used to evaluate the different hybrid systems. On the one hand side, DFT optimizations of one hybrid structure for every diasteriomere were carried out using Gaussian9 software package. On the other hand Dreiding forcefield molecular dynamic simulations were used to study a variety of binding geometrys in gasphase. Concerning the DFT-calculations PBE functional with 6-1G(d,p) basis set was used including Grimme empirical dispersion correction. Water solvation was simulated using polarizable continuum model (PCM). Hydrogen terminated SWCNTs fragments of 2 Å length were used for the calculation and the different PDI s were placed along vector a1 or a2 of the SWCNT. Upon successful optimization, the binding energy and electrostatic potential fitted point charges (ESP-charge) was analysed and the latter was compared to those of the non-interacting moieties. In the second more statistical approach the Dreiding molecular forcefield was used. Hydrogen terminated SWCNT fragments containing three unit cells were optimized. The as well optimized PDI structures were placed in.2 Å distance and molecular dynamic simulation were carried out. Please note that the SWCNT structure was frozen during the MD simulation. Furthermore, the solubilizing Ethylammonium groups were removed from the PDI to avoid a change in energy due to their movement. Berendsen thermostat was used at room temperature. The first out of 11 ns in total was used as equilibration time and not further analysed. Out of the remaining 1 ns snapshot structures were statistical analysed by their potential energy. Main goal is to correlate geometric parameters, like the van der Waals bond distance, the PDI bay twist angle as well as the relative orientation towards the carbon lattice (rotation) with the potential energy. Table S1: PDI-SWCNT binding energy determined by: E B=E hybrid - E purepdi - E CNT in kcal mol -1. 6, 7, 7, _ anti _ anti_ _ Table S2: PDI-SWCNT binding energy relative to the corresponding PDI 7,6-SWCNT hybrid. 6, 7, 7, _ anti _ anti_ _

11 Figure S2: Top: PDI-SWCNT binding energy determined by: E B=E hybrid - E purepdi - E SWCNT in kcal mol -1, averaged for all diasteriomers. Bottom: PDI-SWCNT binding energy relative to the corresponding PDI-7,6-SWCNT DE B=E B - E B(7,6-SWCNT) hybrid, averaged for all diasteriomers. 11

12 Figure S21: Top: PDI-SWCNT binding energy determined by: E B=E hybrid - E purepdi - E CNT in kcal mol -1. Bottom: PDI-SWCNT binding energy relative to the corresponding PDI-7,6-SWCNT hybrid. 12

13 Figure S22: Averaged electrostatic potential fitted point charges for the different PDI-SWCNT hybrids. Top: Charge on PDI. Center: Charge on SWCNT. Bottom: Charge difference on PDI core atoms (excluding solubilizing groups) determined by subtracting the pure PDI charges from the PDI-SWCNT hybrid charges. 1

14 8 PDI Br2 Br 7 6 DE / kcal mol twist / PDI Br2 Br 2 DE / kcal mol twist / Figure S2: DFT relaxed potential energy surface scan showing the energetic dependency upon variation of the bay twist angle of 1 (black), 2 (red) and (blue). 1

15 Dreiding Force field results 1 6PDI.csv 7PDI 76PDI 7 Count binding energy / kcal mol -1 Figure S2: Distribution of the interaction energy for hybrids of PDI 1 with 6,- (black), 7,- (grey) and 7,6-SWCNT (red) Br2.csv 6Br22.csv 7Br2 7Br22 76Br2 76Br22 Count binding energy / kcal mol -1 Figure S2: Distribution of the interaction energy for hybrids of PDI 2 with 6,- (black), 7,- (grey) and 7,6-SWCNT (red). The starting geometry was along a1 (circles) or a2 (squares) of the SWCNT carbon lattice. 1

16 Br2anti.csv 6Br2anti2.csv 7Br2anti 7Br2anti2 76Br2anti 76Br2anti2 Count binding energy / kcal mol -1 Figure S26: Distribution of the interaction energy for hybrids of PDI 2 with 6,- (black), 7,- (grey) and 7,6-SWCNT (red). Here the brominated bay positions are facing distal. The starting geometry was along a1 (circles) or a2 (squares) of the SWCNT carbon lattice. 6Br.csv 6Br2.csv 7Br 7Br2 76Br 76Br2 Count binding energy / kcal mol -1 Figure S27: Distribution of the interaction energy for hybrids of PDI with 6,- (black), 7,- (grey) and 7,6-SWCNT (red). The starting geometry was along a1 (circles) or a2 (squares) of the SWCNT carbon lattice. 16

17 Correlation energy in dependence of the main geometric parameters Figure S28: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 6,-SWCNT with PDI. Figure S29: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 7,-SWCNT with PDI. 17

18 Figure S: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 7,6-SWCNT with PDI. Figure S1: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 6,-SWCNT with PDI 1. 18

19 Figure S2: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 7,-SWCNT with PDI correlation energy / kcal m ol twist / Y-Achsentitel Figure S: Correlation energy in dependence of the bay twist angle and the rotation on the SWCNT lattice for 7,6-SWCNT with PDI 1. 19

20 Figure S: Left: Differential absorption spectra of 1/SWCNT. Right: Differential absorption spectra of 2/SWCNT. Both spectra were obtained upon femto second flash photolysis (λex = 87 nm) in D2O with different time delays from 2 (red) to 7 ps (violet) after ps after ps after ps Figure S: Left: Comparison of the differential absorption spectrum of the one electron reduced form of 1 (red) with the respective transient absorption spectrum (black). Middle: Comparison of the differential absorption spectrum of the one electron reduced form of 2 (red) with the respective transient absorption spectrum (black). Right: Comparison of the differential absorption spectrum of the one electron reduced form of (red) with the respective transient absorption spectrum (black). The differential absorption spectra of the one electron reduced form of recorded PDIs were obtained in D2O containing. M Na2SO under reductive conditions vs. Ag-wire. The respective transient absorption spectra (black) were obtained upon femto second flash photolysis (λex = 87 nm) in D2O at a time delay of ps Time / ps Time / ps Time / ps Time / ps Time / ps Time / ps 2

21 Time / ps Time / ps Time / ps Figure S6: Top: Time absorption profiles and corresponding fits of 1/SWCNT at 1 nm, 1 and 11 nm (left to right). Center: Time absorption profiles and corresponding fits of 2/SWCNT at 1 nm, 1 and 11 nm (left to right). Bottom: Time absorption profiles and corresponding fits of /SWCNT at 1 nm, 1 and 11 nm (left to right). t CSS1 / ps (7,6) (6,) (7,6) (7,) (6,) 8 6 (7,) (7,6)(7,) DG ET / ev Figure S7: Driving force dependence of the lifetimes determined for CSS2 in 1/SWCNT (black), 2/SWCNT (red) and /SWCNT (grey). Table S: Lifetimes derived from multiexponential fittings of the respective femtosecond transient absorption kinetics of 1/SWCNT, 2/SWCNT, and /SWCNT at 7 nm. 1/SWCNT 2/SWCNT /SWCNT τ1 / ps A1 %.% 6% τ2 / ps A2 % 1% 19% τ / ps A 11% 6% 16% 21

22 Table S: Lifetimes derived from multiexponential fittings of the respective femtosecond transient absorption kinetics of 1/SWCNT, 2/SWCNT, and /SWCNT at 1 nm. 1/SWCNT 2/SWCNT /SWCNT τ1 / ps A1 7% % % τ2 / ps.6.2. A2 % 6% 27% τ / ps A 2% 26% 2% τ / ps A % % 18% Table S: Lifetimes derived from multiexponential fittings of the respective femtosecond transient absorption kinetics of 1/SWCNT, 2/SWCNT, and /SWCNT at 1 nm. 1/SWCNT 2/SWCNT /SWCNT τ1 / ps A1 6% 1% % τ2 / ps A2 % % 29% τ / ps A 17% 1% 16% τ / ps A % % % 22

23 Table S6: Lifetimes derived from multiexponential fittings of the respective femtosecond transient absorption kinetics of 1/SWCNT, 2/SWCNT, and /SWCNT at 11 nm. 1/SWCNT 2/SWCNT /SWCNT τ1 / ps.6..8 A1 % 6% 6% τ2 / ps A2 6% % 28% τ / ps A 17% 16% 21% τ / ps A % % % Table S7: Calculated energy of the charge-separated states in 1/SWCNT, 2/SWCNT and /SWCNT based on the experimentally determined first reduction potentials of 1- and the oxidation potentials of 6, SWCNT, 7, SWCNT, and 7,6 SWCNT. 1 2 (6,).98 ev.79 ev.68 ev (7,).88 ev.69 ev.8 ev (7,6).8 ev.6 ev. ev 2