Electronic Supporting Information

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1 Electronic Supporting Information Charge Transfer and Tunable Ambipolar Effect induced by the assembly of Cu(II) Binuclear Complexes on Carbon Nanotube Field Effect Transistor Devices Gurvan Magadur, 1, * Jean-Sébastien Lauret, 2 Gaëlle Charron, 1 Fatima Bouanis, 1,3 Evgeny Norman, 3 Vincent Huc, 1 Costel-Sorin Cojocaru, 3 Silvia Gómez-Coca, 4 Eliseo Ruiz, 4 Talal Mallah 1, * 1 Institut de Chimie Moléculaire et des Matériaux d Orsay, Université de Paris Sud 11, Bât. 420, 15 rue Georges Clemenceau, Orsay Cedex, France, 2 Laboratoire de Photonique Quantique et Moléculaire, 61, avenue du Président Wilson, Cachan, France, 3 Laboratoire de Physique des Interfaces et Couches Minces, Ecole Polytechnique, F Palaiseau, France, 4 Departament de Química Inorgànica and Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, Barcelona, Spain. 1. Materials and methods : Copper acetate monohydrate was obtained from Kanto Chemicals. Benzène-1,2,4,5-tetraamine and 3,5- diterbutylsalicylaldehyde were obtained from Aldrich. Deuterated solvents for NMR measurements were obtained from Cambridge Isotope Laboratories. HiPCo SWNT were obtained from Unidym TM, Inc, CA, US. 1 H NMR spectra were recorded at 360MHz in CDCl 3. Elemental analysis were performed at Service de Microanalyses, ICSN-CNRS, Gif-sur-Yvette, France. Infrared spectra were recorded on a FT-IR spectrometer Perkin Elmer spectrum 100. EPR spectra were recorded at 5K on a Bruker EleXsys 500 spectrometer equipped with a continuous-flow cryostat (Oxford Instruments). The concentration of the studied solution was 10-5 mol.l 1. Field effect transistors are homemade 1 (see below) and the electronic measurements were carried out on the semiconductor parametric analyzer Keithley 4200-SCS under ambient conditions. The wavelength used for the Raman studies is nm and the spectrometer is a T64000 Jobin- Yvon triple spectrometer, accessorized with an optical microscope. The diameter of the beam was equal to 2µm and the power set to 0.5 mw. The spectrum was calibrated using a silicium wafer prior to each acquisition. 2. Synthesis Bisalophen (Figure S1): To a suspension of benzene-1,2,4,5-tetraamine (284 mg, 1mmol) and triethylorthoformiate (2mL) in ethanol (10mL) under Ar was added 3,5-diterbutylsalicylaldehyde (1.3 g, 5.5mmol) and diisopropylethylamine (1.2 ml). The mixture was stirred at 70 C under Ar. The yellow precipitate was collected by filtration, washed with cold ethanol and dried under vacuum to give Bisalophen (656mg, 65%). 1 H NMR (CDCl 3 ): δ (ppm) 1.33 (s, 36H,t-Bu), 1.43 (s, 36H, t-bu), 7.14 (s, 2H, Ar-H), 7.24 (d, 4H, H-Ar, J=2Hz), 7.44 (d, 2H, H-Ar, J=2Hz), 8.76 (s, 4H, CH=N), (s, 4H, OH). IR (KBr pellet) : ν (cm -1 ) 1587 and 1612 (ν C=N ).Anal. Calcd for C 66 H 90 N 4 O 4 : C (79.00), H 8.76 (9.04), N 5.61 (5.58). Cu 2 bisalophen (1) (Figure S2): To a solution of Bisalophen (313mg, 0,3 mmol) in 5mL of dichloromethane was added a solution of copper (II) acetate ( 0,6 mmol) in 10 ml of methanol. The mixture was stirred under reflux for 30 minutes then filtered and washed with cold methanol to give 1 as a red solid (338 mg, 96%). Anal. Calcd for C 66 H 86 N 4 O 4 Cu 2 : C (70.37), H 7.38 (7.69), N 4.84 (4.96), Cu (11.28). S 1

2 Figure S1. Synthesis route for Bisalophen Figure S2. Synthesis route for M 2 Bisalophen complexes 3. Purification of the SWNT for EPR measurements The purification process of HiPCo SWNT was realized according to a method developed by Charron et al.[2]. The resulting nanotubes were obtained catalyst free as shown on Figures S3 and S4. a) b) Figure S3. TEM images (high resolution, bright) of the carbon nanotubes before (a) and after (b) the purification process. S 2

3 Figure S4. Raman spectrum of the purified HiPCo SWNT (almost no D-band). 4. UV-Vis and photoluminescence spectra Spectroscopic Measurements: Optical absorption spectra are recorded with a spectrophotometer (Lambda 900 Perkin Elmer). A laser diode emitting at 532 nm is used as excitation source for photoluminescence experiments. The signal is dispersed in a spectrograph (Spectrapro 2300i, Roper Scientific) and detected by an IR CCD (OMA V, PI Acton). A UV/Vis Xe lamp and a monochromator (Spectrapro 2150i, Roper Scientific) are used as tunable light source for the photoluminescence excitation experiments. UV-Vis spectra of Bisalophen and 1: 1 mg of Bisalophen and 1,13 mg of 1 were dissolved in 10 ml of dichloromethane giving respectively a yellow and a red solution (10-5 mol.l -1 ) which were analyzed (Fig. S5).. Figure S5. UV-Visible spectra of Bisalophen ligand (black curve) and 1 (red curve) in CH 2 Cl 2 (10-5 mol.l -1 ). The nanotube suspensions are prepared according to Roquelet et al.[3] by adding raw nanotubes at 0.15 mg.ml -1 in a ph 8 Normadose buffer (10-2 M, Prolabo) plus 2 wt% of sodium cholate (Sigma Aldrich). The mixture is sonicated for 1.5h with an ultrasonic tip and ultracentrifuged at g for 1h. Then, the supernatant is drawn out. It consists in a suspension of isolated nanotubes (Fig. S6). Nanotube functionalization is achieved by mixing the nanotube suspension with a solution of 1(0,6 µmol) in DCM. S 3

4 After adding the complex solution to the nanotube suspension, the mixture is sonicated for 2 h with an ultrasonic tip. The sample is placed in a thermostat at 12 C during sonication. The phase corresponding to DCM evaporates slowly. The resulting suspension of SWNT/1 is obtained and put to analysis (Fig. S7 and S8)). Figure S6. The nanotube is encapsulated in micelles. Some solvent molecules (DCM) are dragging 1 into the micelles. The volatile solvent evaporates, enabling the complexes to stack onto the SWNT wall. Figure S7. UV-Visible spectra of 1 (black curve, MLCT bands between 400 and 600 nm), 1 and SWNT in a ph 8 buffer with 2 wt% sodium cholate after evaporation of CH 2 Cl 2 (red curve), 1 and SWNT in a ph 8 buffer with 2 wt% sodium cholate after evaporation of CH 2 Cl 2 (blue curve) with a concentration of 1 three times higher. Photoluminescence excitation map of a HiPCO SWNT sample in a ph 8 buffer with 2 wt% sodium cholate. Figure S8. Variation of the intensity of a HiPCO SWNT sample in a ph 8 buffer with 2 wt% sodium cholate with the excitation and emission wavelength. S 4

5 5. Calculations Theoretical calculations were performed with the Siesta code [4] using numerical functions and PBE+U (U = 4.0 ev)[5, 6] and DRSLL functionals [7] using a (7,6) nanotube for the study of the molecule-nanotube interaction effects. The DRSLL functional was specially created to take into account dispersion terms while the PBE+U functional gives better estimation of the physical properties. These calculations allow to obtain qualitative results and also to perform the optimizations of the geometry for the whole molecule nanotube system. In order to obtain more quantitative results of the physical magnitudes, we also carried out calculations just for the [Cu 2 Bisalophen] complex using hybrid functionals [8] and all electron triple-ζ basis set[9] with the Gaussian code[10]. We considered two possible starting geometries (parallel and perpendicular, Cu Cu orientation with the nanotube) for the optimization structure, being the perpendicular one the more stable (at numerical PBE+U and DRSLL levels 7.1 and 16.2 kcal/mol, respectively, see Fig. 5) with an interaction 1 SWNT energy of kcal/mol with the PBE+U functional and kcal/mol with the DRSLL functional. Despite the large difference in the interaction energies the equilibrium geometries and the nanotube-molecule distances are almost identical with both functionals. The central aromatic ring of 1 has a shifted stacking orientation respect to the closest hexagon of the nanotube with the shortest C C and Cu C distances around 4.1 and 4.7 Å, respectively. In order to study the spectral modifications, we performed time-dependent DFT calculations[11] (Gaussian code including in some cases solvent effect using the CPCM approach[12]) to determine the vertical excitations of the 1 molecule using the hybrid PBE0 functional[13] together a triple-ζ basis set. The comparison of values has been done between the experimental structure of the 1 molecule and its structure in the optimized 1@(7,6)SWNT system. The nanotube was not included in the TDDFT due to the limitations of the code. The experimental values for the isolated 1 molecule are 507 and 535 nm that are red-shifted for the interaction with the nanotube to 514 and 550 nm, respectively. The TDDFT calculations confirm such experimental trend with the structural change of the 1 molecule due to the interaction with the nanotube. Thus, without solvent the excitation values for 1 are 487 and 523 nm and for the interacting 1 molecule 520 and 568 nm (including water solvent, red-shift from 484 and 502 nm to 508 and 520 nm). 6. Fabrication of the FET devices SWNTs were grown by double hot filament assisted chemical vapor deposition (HFCVD) on 100 nm silicon oxide films on silicon substrates, using a new strategy for catalyst preparation based on Self Assembled Monolayer (SAM) which have been previously described. Random nanotubes networks, consisting of isolated carbon nanotubes, were obtained with excellent selectivity and high quality and uniformity. Their diameters varied from 1 to 2 nm. These networks were used for CNFETs device fabrication. Source-drain palladium contacts with a thickness of 40 nm were fabricated using standard UV lithography, e-beam evaporation and lift-off processes. It is generally accepted that Pd yields very good contacts for SWCNTsmetal contacts because of its high work function and corrosion resistance. The device geometry was varied with the source-drain channel length (L SD ) ranging from 2 to 20 µm and the channel width (W) ranging from 1 to 5mm were deposited to form an array of 4000 TFTs. Only the 2µm and few of the 5µm channel length devices were functional, suggesting that the CNTFET channel in this case consist of random but directly contacted isolated SWNT (little or no tube-tube percolation). The highly doped silicon substrate was used as common back-gate for all transistors. (Fig. S9). Finally, the metallic nanotubes were burned using the method proposed by IBM, semi-conducting SWNT being better suited for ultrasensitive detection (Fig. S10). S 5

6 Interdigitate Interdigitated d Pd electrodes electrodes S D a) b) SiO 2 Doped Si c) Gate (unbiased) As grown CNTs Figure S9. a) Schematic view of the SWNT-FET with a Si/SiO 2 (100 nm) back-gate. b) Photo of SWNT- FET, (c) Scanning electron microscope (SEM) image showing the gate region of a representative device consisting of a large number of SWNTs Figure S10. I d vs. V g curves for a CNFET device before (red curve) and after (blue curve) the burning process of the metallic SWNT. 7. Electronic measurements Conduction measurements were realized at room temperature. No change in the behavior of the CNFET was observed after washing the circuits with DCE and drying them as reported in Fig S11. Several CNFET S 6

7 (twelve) were submitted to molecular grafting, leading to similar results as reported in Fig S12. The obtained I on /I off ratio can be up to almost 8 decades. Figure S11. I d vs. V g curves for a CNFET device before (black curve) and after (red curve) the washing with DCE. The experimental starting gate potential is - 20 V. V ds = 2V. Figure S12. I d vs. V g curves for a CNFET device before (black curve) and after a different number of grafting-rinsing cycles with 1. The experimental starting gate potential is - 20 V. V bias = 2 V. S 7

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