supporting information for: recti cation of current ... · recti cation of current responds to...

Supporting information for:

Rectification of Current Responds to

Incorporation of Fullerenes into

Mixed-Monolayers of Alkanethiolates in

Tunneling Junctions

Li Qiu, Yanxi Zhang, Theodorus L. Krijger, Xinkai Qiu, Patrick van ’t Hof, Jan

C. Hummelen, and Ryan C. Chiechi∗

Stratingh Institute for Chemistry & Zernike Institute for Advanced Materials, University of

Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands

E-mail: [email protected]

S1

Electronic Supplementary Material (ESI) for Chemical Science.This journal is © The Royal Society of Chemistry 2017

[email protected]

Contents

1 Experimental details S2

1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S2

1.2 Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S4

2 Electrical Measurements S7

2.1 Histogram of log |R| and current density . . . . . . . . . . . . . . . . . . . . S7

2.2 Plots of log |R|, log |J | and log |I| versus V . . . . . . . . . . . . . . . . . . . S8

3 Characterization S8

3.1 Contact angle measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . S8

3.2 XPS thickness measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . S8

3.3 Estimation of LUPS of FSC11 . . . . . . . . . . . . . . . . . . . . . . . . . S11

3.4 NMR spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S18

References S22

1 Experimental details

1.1 General

General: Chemicals including 11-bromoundec-1-ene, 4-hydroxybenzaldehyde, thioacetic

acid, 1-decanethiol (SC10) were obtained from Sigma-Aldrich and used as received with

the exception of SC10 which was purified by column chromatography (silica, hexane). The

C60 used for the syntheses was 99.5 % (purchased from Solenne BV, Groningen, The Nether-

lands). All compounds were stored in nitrogen-flushed vials and in the dark. The Au

substrates used in this work are made by mechanic Template Stripping (mTS) described

in detail elsewhere.S1 In our case, we deposited 200 nm of Ag and 100 nm of Au (99.99%),

respectively, by thermal vacuum deposition onto a 3′′ Silicon wafer (with no-adhesion layer).

S2

Using UV-curable Optical Adhesive (OA) Norland 61, we glued 1 cm2 glass chips on the

metal surfaces. The mTS procedure provides ultra flat smooth surfaces, which allows self-

assembly process to achieve higher yields of working junctions.

Analytical TLC was performed on Merck silica gel 60/kieselguhr F254 and visualization

was accomplished by UV light. Column chromatography was performed using silica gel (Sil-

iaFlash P60 Type R12030B, 230-400 mesh). 1H-NMR and 13C-NMR were performed on a

Varian Unity Plus (400 MHz) instrument at 25 ◦C, using tetramethylsilane (TMS) as an in-

ternal standard. NMR shifts are reported in ppm, relative to the residual protonated solvent

signals of CDCl3 (δ = 7.26 ppm) or at the carbon absorption in CDCl3 (δ = 77.0 ppm),

and multiplicities are denoted as: s = singlet, d = doublet, t = triplet and m = multiplet.

IR measurements were performed on a Nicolet iS50 FT-IR spectrometer. UV-vis absorption

spectra were measured with a Jenway 6715 spectrophotometer. High Resolution Mass Spec-

troscopy (HRMS) was performed on a JEOL JMS 600 spectrometer. Contact Angles (CA)

were measured under ambient conditions on a SCA20 Dataphysics instrument with software

version 3.60.2. Equilibrium contact angles were obtained by applying 1 µL water droplets

on SAMs using the sessile drop method. The contact angle was measured at three different

locations on each surface and the results were averaged. XPS measurements were performed

using a VG Microtech spectrometer with a hemispherical electron analyzer, and a Mg Kα

(1253.6 eV) X-ray source. CP-AFM I-V measurements were performed on a Bruker AFM

Multimode MMAFM-2 equipped with a Peak Force TUNA Application Module (Bruker).

The SAMs were contacted with an Au-coated silicon nitride tip with a nominal radius of

30 nm (NPG-10, Bruker, tip A: resonant frequency 65 kHz, spring constant: 0.35 N/m;

tip B: resonant frequency: 23 kHz, spring constant: 0.12 N/m; tip D: resonant frequency:

18 kHz, spring constant: 0.06 N/m) in TUNA mode with loading force of 1.4 nN (tip A),

0.48 nN (tip B) and 0.24 nN (tip D), respectively. The AFM tip was grounded and for

loading force of 1.4 nN, the sample was biased from -1.5 V to +1.5 V and from +1.5 V

S3

to -1.5 V (while for loading force of 0.48 nN and 0.24 nN, the sample was biased from -2

V to +2 V and from +2 V to -2 V) to record the I-V curve (512 points per trace were

taken): a max of 30 trace/re-trace cycles per junction were performed. After every junc-

tion, the tip was withdrawn and moved to a different spot, and engaged again for a total

of 39 (for 1.4 nN of loading force), 20 (for 0.48 nN of loading force) and 10 (for 0.24 nN of

loading force) junctions per sample analyzed. Between different samples a new tip was used.

The data were analyzed with the same software used for EGaIn using the current I instead

of the current density J. The obtained log|I|(V ) plots and log|R|(V ) are shown in Figure S6.

1.2 Synthesis

The synthesis of compound FSC11 is straightforward, as shown in Scheme S1. By treat-

ing the commercially available 4-hydroxybenzaldehyde with 11-bromo-1-undecene under ba-

sic conditions, 4-(10-Undecenyloxy)benzaldehyde could be obtained in good yield, which

was then converted to the thioester 4-(11-thioacetoxyundecyl)benzaldehyde through a free

radical-mediated nucleophilic addition(azo-bis-isobutyronitrile (AIBN) as the radical initia-

tor). The Prato reactionS2 then gave the corresponding FSC11-Ac, which experienced

dibutyltin oxide-mediated transesterification with methanol to give the target C60-thiol

FSC11.S3 New compounds were all fully characterized by means of HRMS, NMR and IR.

4-(10-Undecenyloxy)benzaldehyde. The procedure for the synthesis of this compound

was taken from the literature.S4 11-Bromo-1-undecene (4.38 mL, 4.66 g, 20 mmol), 4-

hydroxybenzaldehyde (2.44g, 20 mmol), tetrabutylammonium iodide (catalytic amount, 0.20

g) and potassium carbonate (13.80 g, 100 mmol) were introduced into acetone (100 mL).

After refluxing for 6 h, the mixture was allowed to cool to room temperature and the solids

were filtered off. The filtrate was concentrated in vacuo and the crude product was purified

by column chromatography (ethyl acetate:hexane = 1:9) to give 5g product as a colorless oil

S4

O

O S

O

N OC11H22SHN OC11H22SAc

FSC11-Ac FSC11

9

H

Sarcosine, C60

Chlorobenzene, 100 oC, 24 h

Dibutyltin oxide

Chlorobenzene/MeOH

Reflux, 24 h

O

O9

H

Toluene, 25 oC, 6 h

O

OH

H

nBu4NI, K2CO3

Acetone, Reflux, 6 h

9Br

, AIBN

O

SH

Figure S1: Synthetic route of FSC11

(90%).

4-(11-Thioacetoxyundecyl)benzaldehyde. The procedure for the synthesis of this com-

pound was taken but lightly improved from the literature.S5 4-(10-Undecenyloxy)benzaldehyde

(2.74 g; 10 mmol), thioacetic acid (7.13 mL; 100 mmol), and azo-bis-isobutyronitrile (AIBN,

30 mg; 0.18 mmol) were dissolved in 40 mL of toluene. The mixture was degassed with a

stream of N2 and then stirred at room temperature for 8 h. The reaction was quenched with

5% aqueous NaHCO3 and extracted three times with ethyl acetate. The combined organic

layers were washed with 5% aqueous NaHCO3 and then brine and dried over MgSO4. Upon

filtration and removal of the solvent under reduced pressure, the yellow solid residue was

then purified by column chromatography on silica eluting with a gradient of pure toluene

to pure chloroform. The crude product obtained was recrystallized from methanol to afford

1.41 g (42%) of the title aldehyde as a white powder.

FSC11-Ac. An oven-dried three-necked, 500 mL round-bottom flask was charged with C60

S5

(1.44 g, 2 mmol), 4-(11-thioacetoxyundecyl)benzaldehyde (700 mg, 2 mmol), sarcosine (720

mg, 8 mmol) and chlorobenzene (200 mL). The reaction mixture was stirred under N2 at

100 ◦C for 24 h. The mixture was concentrated in vacuo to 15 mL, and the crude residue

was purified by column chromatography (Silica gel; CS2 followed by toluene) to afford the

pure compound as a brown solid. The product was redissolved in 7 mL of chlorobenzene,

precipitated with MeOH, washed repeatedly with MeOH and pentane, and dried in vacuo

at 50 ◦C. This procedure gave 600 mg (0.55 mmol, 27%) of FSC11-Ac.

1H-NMR (400 MHz, CS2 / D2O) δ 7.84 (s, 2H), 7.05 (d, J = 8.1 Hz, 2H), 5.16 (d, J = 9.2

Hz, 1H), 5.07 (s, 1H), 4.46 (d, J = 9.2 Hz, 1H), 4.11 (t, J = 6.3 Hz, 2H), 3.01 (s, 3H), 2.48 (s,

3H), 2.06 1.92 (m, 2H), 1.80 1.64 (m, 4H), 1.52 (s, 14H). 13C-NMR (100 MHz, CS2 / D2O) δ

162.1, 159.1, 156.8, 156.4, 156.3, 150.0, 149.6, 149.3, 149.2, 149.1, 149.0, 148.9, 148.7, 148.6,

148.5, 148.3, 148.2, 148.1, 148.0, 147.5, 147.2, 146.0, 145.9, 145.5, 145.4, 145.1, 145.0, 144.9,

144.8, 144.7, 144.5, 144.4, 143.1, 143.0, 142.8, 142.5, 139.6, 139.5, 138.6, 133.1, 131.2, 117.5,

86.0, 80.2, 72.9, 71.7, 70.6, 42.9, 33.1, 33.0, 32.9, 32.8, 32.7, 32.5, 32.3, 32.2, 29.5. IR (cm−1):

2923, 2849, 2777, 2326, 1687, 1609, 1506, 1461, 1330, 1243, 1171, 1105, 1029, 946, 831, 702.

HRMS(ESI) calcd. for C82H36NO2S[M+H]+: 1098.24613, found: 1098.24992.

FSC11. The solution of FSC11-Ac (300 mg, 0.27mmol) and dibutyltin oxide (3.42mg,

0.014mmol, 5mol%) in chlorobenzene (60 ml) and methanol (30 ml) was heated to reflux for

24 h under N2. The mixture was concentrated in vacuo to 15 mL, and the crude residue was

purified by column chromatography (Silica gel; toluene/hexane=1/1 followed by toluene)

to afford the pure compound as a brown solid. The product was redissolved in 7 mL of

chlorobenzene, precipitated with MeOH, washed repeatedly with MeOH and pentane, and

dried in vacuo at 50 ◦C. This procedure gave 88 mg (0.55 mmol, 30%) of FSC11.

1H-NMR (400 MHz, CDCl3) δ 7.69 (s, 2H), 6.94 (d, J = 8.2 Hz, 2H), 4.97 (d, J = 8.7 Hz,

1H), 4.88 (s, 1H), 4.24 (d, J = 9.1 Hz, 1H), 3.95 (t, J = 6.5 Hz, 2H), 2.79 (s, 3H), 2.51 (dd,

J = 14.7, 7.4 Hz, 2H), 1.83 1.71 (m, 2H), 1.68 1.52 (m, 3H), 1.50 1.21 (m, 14H). 13C-NMR

S6

(100 MHz, CDCl3) δ 161.9, 159.0, 156.8, 156.3, 150.0, 149.9, 149.5, 149.2, 149.0, 148.9, 148.8,

148.7, 148.6, 148.4, 148.2, 148.1, 148.0, 147.9, 147.8, 147.4, 147.3, 147.0, 145.8, 145.6, 145.3,

145.2, 144.9, 144.8, 144.7, 144.6, 144.5, 144.3, 144.2, 142.8, 142.6, 142.2, 139.5, 139.3, 138.4,

133.1, 131.3, 117.2, 85.9, 72.6, 71.6, 70.6, 42.7, 36.7, 32.2, 32.1, 32.0, 31.7, 31.0, 28.7, 27.3.

IR (cm−1): 2918, 2848, 2773, 1604, 1510, 1461, 1424, 1330, 1243, 1168, 1103, 1025, 908, 829,

702. HRMS(ESI) calcd. for C80H34NOS[M+H]+: 1056.23556, found: 1056.23989.

2 Electrical Measurements

2.1 Histogram of log |R| and current density

0 . 0 0 . 5 1 . 0 1 . 5 2 . 00

1 0

2 0

3 0

4 0

5 0

coun

ts

F S C 1 1 P u r e S A M s

l o g | R |

Figure S2: Histograms of log |R| for pure SAMs and FSC11 on AgTS obtained by dividingeach value of J at positive bias into the corresponding value at negative bias for every valueof |V | for 567 and 650 J/V traces, respectively. While log |R| for FSC11 SAMs (mixedmonolayers) produced a single Gaussian centered near 1.5, the data of the pure SAMs aredistributed from 0 − 2 and likely comprise multiple peaks. We interpret this difference tocompetition from the strong fullerene-fullerene and fullerene-Ag interactions (discussed inthe main text) that preclude the formation of a well-ordered SAM.

S7

- 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0- 0 . 0 20 . 0 00 . 0 20 . 0 40 . 0 60 . 0 80 . 1 00 . 1 2

o n p u r e S A M s

l o g | R | @ 0 . 8 5 V = 2 . 1 0

r e vf w d

Curre

nt (A)

r e v

f w d

P o t e n t i a l ( V )- 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0

- 0 . 0 2

0 . 0 0

0 . 0 2

0 . 0 4

0 . 0 6

0 . 0 8

o n F S C 1 1 S A M s l o g | R | @ 0 . 9 5 V = 2 . 7 9

r e v

f w d

f w d

Curre

nt (A)

P o t e n t i a l ( V )

r e v

Figure S3: I/V data for representative junctions that produce stable I/V curves above 0.5 Vshowing typical degrees of hysteresis based both on pure FSC11 SAMs (left) and on mixedFSC11 SAMs (right) on AgTS.

2.2 Plots of log |R|, log |J | and log |I| versus V

3 Characterization

3.1 Contact angle measurement

The SAM of FSC11 was evaluated with water contact angle measurements, before the

exchanging, the SAM of SC10 (left) was determined to be more hydrophobic and showed

an average contact angle of 94 ± 1◦, while after exchanging, the fullerene SAM of FSC11

was formed with an average contact angle of 68 ± 1◦, which is corresponding closely to values

of C60-SAM reported by Tsukruk and co-workers.S6

3.2 XPS thickness measurement

To measure the thickness of the SAM we acquire the Ag3p3/2 and Ag3d peaks with the sample

rotated under 0, 10, 20, 30, 40, and 50 degrees. A Gaussian fit with background is made

to the peaks to obtain their intensities. To correct for slow fluctuations in the X-ray source

intensity we acquire a spectrum for each peak at 0 degrees in between the measurements

where the sample is rotated. These measurements are used to obtain a correction factor γI .

S8

- 5 - 4 - 3 - 2 - 1 00

3 06 09 0

1 2 01 5 01 8 02 1 0

l o g | J |

A f t e r e x c h a n g e B e f o r e e x c h a n g e

01 02 03 04 05 06 07 0

coun

ts

coun

tsA t - 0 . 5 V

- 4 - 3 - 2 - 1 00

4 08 0

1 2 01 6 02 0 02 4 0

A f t e r e x c h a n g e B e f o r e e x c h a n g e

coun

ts

coun

ts

l o g | J |

A t + 0 . 5 V

01 02 03 04 05 06 0

Figure S4: Histograms of current density of FSC11 and SC10 at - 0.5 V (left) and + 0.5V (right) in the AgTS/FSC11 or SC10//Ga2O3/EGaIn junctions. The maximum value oflog |J | at −0.5 V drops below −3, while the value at 0.5 V remains almost equal to thatof SC10. The suppression of leakage current (at negative bias) compared to the SAM ofpure SC10 is caused by the increase in tunneling distance imposed by the fullerene group.At positive bias, the LUPS is sufficiently close to Ef of Ag electrode that charges can bemediated by LUPS of C60 cage and tunneling occurs only through the aliphatic portion ofthe SAM (followed by hopping between C60 cage and EGaIn), leading to a nearly equalmagnitude of J for SAMs of SC10 and FSC11 at 0.5 V. This asymmetry results in anobvious current rectification.

This factor was used to normalize the peak intensities to acquire I∗ = γII, which was used

to fit the thickness of the layer. The values are given in Table S1.

Table S1: measured XPS peak intensities (I), correction factor γI , and the corrected peakintensities (I∗) for the Ag3d and Ag3p peaks.

sample Ag3d Ag3p3/2rotation (◦) I γI I∗ I γI I∗

0 8358 1.00 8358 3775 1.00 377510 7945 1.01 8044 2972 0.91 271520 7349 1.00 7333 3663 0.95 347130 6479 0.96 6230 3029 0.93 282040 5050 0.94 4748 1732 0.88 152250 3086 0.93 2880 1121 0.86 965

We measure the intensity of the peaks of electrons that make it from the silver through

the SAM, without scattering. The intensity therefore depends on the length of the path

through the overlayer, and the inelastic mean free path of the electrons. The intensity at a

S9

0 . 4 0 . 8 1 . 2 1 . 6 2 . 00

1 0

2 0

3 0

4 0

5 0 A u T S A g T S

01 02 03 04 05 06 07 0

coun

ts

coun

tsl o g | R |

Figure S5: Histograms of log |R| for FSC11 on AgTS and AuTS obtained by dividing eachvalue of J at positive bias into the corresponding value at negative bias for every value of |V |for 650 and 366 J/V traces, respectively. The blue and red lines are Gaussian fits with peaksand standard deviations of 1.46±0.018 and 0.92±0.017 for AgTS and AuTS respectively.

given angle can be expressed as:

I∗(φ) = I0 exp(−Lλ

) = I0 exp(−d

λ cos(φ))

ln(I∗) = ln(I0)−d

λ

1

cos(φ)

(S1)

with L the length of the path through the layer, d the thickness of the layer, λ the inelastic

mean free path, and φ the angle of rotation of the sample with respect to the analyzer. λ

depends on the kinetic energy of the observed electrons and the material the electrons have

to move through. We have determined the values of λ, for electrons originating from the

Ag3d and Ag3p levels, from measurements on a SAM of SC10 on silver, whose thickness was

well studied ((12± 3) A).S7 The values were found to be 8 A−1 and 8.8 A−1 for Ag3d and Ag3p

respectively. With these values of λ we can make a fit to the corrected intensities to find

the thickness of the FSC11 SAM, which was found to be d = 1.8± 0.3 nm. This treatment

assumes the inelastic mean free path in the FSC11 SAM to be equal to that in the SC10

SAM. The lower packing density of FSC11 could lead to a slight underestimation of the

thickness of the layer.

S10

3.3 Estimation of LUPS of FSC11

LUPS energy of FSC11 was determined using a combination of optical and photoelectron

spectroscopy. The UV-vis absorption spectrum (Figure S14) of FSC11, which enables the

estimation of HOMO-LUMO gap (Eg). Inset shows the determination of onset wavelength

to be 718.13 nm, from which Eg is extrapolated to be 1.73 eV.

Ultraviolet photoelectron spectroscopy (UPS, Figure S15) analysis of the SAM bound to

AgTS is used to find the Fermi level of the silver, and the HOPS level of the FSC11 relative

to the Fermi level. Binding energies are calculated with respect to the vacuum level. The

vacuum level is found by summing the secondary electron cutoff and the photon energy

(He I, hν =21.2 eV). In Figure S15 the valence band spectrum is shown as measured by

UPS, showing the characteristic double peak of HOMO and HOMO-1 of C60. For this

data a smooth background function has been subtracted. A multiple Gaussian peak fit is

performed on the data and the width (σ) and center (µ) of the peaks are found from the fit.

We take the value of µ+ 2σ as the onset of the HOMO, which is found to be -5.45 eV. From

the equation ELUMO = EHOMO + Eg (eV), ELUMO is extropolated to be -3.72 eV.

S11

- 1 . 5 - 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5- 8 . 6- 8 . 4- 8 . 2- 8 . 0- 7 . 8- 7 . 6- 7 . 4- 7 . 2- 7 . 0- 6 . 8

l o a d i n g f o r c e : 1 . 4 n N

log|I |

P o t e n t i a l ( V )- 1 . 5 - 1 . 2 - 0 . 9 - 0 . 6 - 0 . 3 0 . 0

- 1 . 6

- 1 . 2

- 0 . 8

- 0 . 4

0 . 0

0 . 4

log|R|


l o a d i n g f o r c e : 1 . 4 n N

- 2 . 0 - 1 . 5 - 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0- 8 . 7- 8 . 4- 8 . 1- 7 . 8- 7 . 5- 7 . 2- 6 . 9- 6 . 6

log|I |


l o a d i n g f o r c e : 0 . 4 8 n N

- 2 . 1 - 1 . 8 - 1 . 5 - 1 . 2 - 0 . 9 - 0 . 6 - 0 . 3 0 . 0- 1 . 6- 1 . 2- 0 . 8- 0 . 40 . 00 . 4 l o a d i n g f o r c e : 0 . 4 8 n N

log|R|


- 2 . 0 - 1 . 5 - 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0- 8 . 7- 8 . 4- 8 . 1- 7 . 8- 7 . 5- 7 . 2- 6 . 9- 6 . 6- 6 . 3- 6 . 0 l o a d i n g f o r c e : 0 . 2 4 n N

log|I |

P o t e n t i a l ( V )- 1 . 8 - 1 . 5 - 1 . 2 - 0 . 9 - 0 . 6 - 0 . 3 0 . 0

- 3 . 0- 2 . 5- 2 . 0- 1 . 5- 1 . 0- 0 . 50 . 00 . 51 . 0 l o a d i n g f o r c e : 0 . 2 4 n N

log|R|


Figure S6: Plots of log |I| (left) log |R| (right) versus V of FSC11 SAM for CP-AFMmeasurements at different loading forces of 1.4 nN (up) 0.48 nN (middle) and 0.24 nN (down)(the units of I are mA). CP-AFM measurements employing a rigid Au electrode insteadof a conformal, liquid-metal electrode (EGaIn) shows an obvious rectification with log |R|greater than 1, meaning that the origin of rectification for the AgTS/FSC11//Ga2O3/EGaInjunction is the SAM and not AgTS or EGaIn. The error bars are standard deviations.

S12

0 . 0 0 . 5 1 . 0 1 . 5 2 . 0

0

1

2

3

4 C P - A F M - 1 . 4 n N C P - A F M - 0 . 4 8 n N C P - A F M - 0 . 2 4 n N

|log|R

||


E G a I n ( p u r e S A M s ) E G a I n ( F S C 1 1 )

Figure S7: Comparison of log |R| vs. |V | plots of EGaIn (black squares and red dots) andCP-AFM (blue, green and magenta symbols) measurements. Each data point is the peak ofa Gaussian fit to a histogram of log |R| at that value of |V |. The error bars are the standarddeviations of those fits. This same plot is shown without error bars in the Main Text forclarity.

- 0 . 6 - 0 . 4 - 0 . 2 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8- 8

- 6

- 4

- 2

0 h 6 h 1 2 h 2 4 h 3 6 h 6 0 h

log|J|

P o t e n t i a l ( V )0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5

0 . 0

0 . 4

0 . 8

1 . 2

1 . 6

2 . 0

log|R|


0 h 6 h 1 2 h 2 4 h 3 6 h 6 0 h

Figure S8: Plots of log|J | (left) and log|R| (right) versus the exchange time for the prepara-tion of FSC11 SAM. The magnitude of log|R| increased gradually with the exchange timebelow 24 h, while remained almost unchanged since then, indicating the nearly completeFSC11 SAM was achieved after 24 h later (we did not perform the measurement for longerthan 60 h because the optical adhesive began to swell).

S13

- 0 . 6 - 0 . 4 - 0 . 2 0 . 0 0 . 2 0 . 4 0 . 6- 7- 6- 5- 4- 3- 2- 1

log|J|


C 8 S H - F S C 1 1 C 1 0 S H - F S C 1 1 C 1 2 S H - F S C 1 1

Figure S9: Plots of log|J | (left) versus the magnitude of applied bias after 24 h exchange forFSC11 SAM preparation using different passivating thiols with different length of alkanechain. The magnitudes of log|J | are not significantly, which again supporting the mechanismproposed in the manuscript.

0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5- 1 . 0- 0 . 50 . 00 . 51 . 01 . 52 . 02 . 53 . 0

R @ 1 V i s d e d u c e d a s 9 4 0E x c h a n g e t i m e : 2 4 h


log|R|

l o g | R | l i n e a r f i t o f l o g | R |

Equation y = a + b*xAdj. R-Square 0.99435

Value Standard Errorlog |R| Intercept 0.1087 0.01858log |R| Slope 2.86467 0.07196

Figure S10: A plot and linear fitting of log|R| versus the magnitude of applied bias after 24h exchange for FSC11 SAM preparation. The linear dependence of log |R| on |V | enablesthe extrapolation of the value of R at any specific |V |, e.g., ±0.95 V. Comparing deducedvalue of R = 676 at ±0.95 V to R = 617 from a single ‘hero junction’ that survived sweepingto ±0.95 V offered a close agreement.

S14

0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5- 1 . 0- 0 . 50 . 00 . 51 . 01 . 52 . 02 . 5

R @ 1 V i s d e d u c e d a s 8 3 3


log|R|



Value Standard Errorlog |R| Intercept 0.12158 0.01754log |R| Slope 2.79887 0.14058

Figure S11: A plot and linear fitting of log|R| versus the magnitude of applied bias forpure SAMs. The linear dependence of log |R| on |V | gave almost the same slope and similardeduced value of R (833) at ±1.0 V.

0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5- 1 . 5- 1 . 0- 0 . 50 . 00 . 51 . 01 . 52 . 02 . 53 . 0

R @ 1 V i s d e d u c e d a s 7 6 4


log|R|



Value Standard Errorlog |R| Intercept -0.04564 0.03077log |R| Slope 2.92856 0.19334

E x c h a n g e t i m e : 3 6 h

0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5

- 1

0

1

2

3

4

R @ 1 V i s d e d u c e d a s 1 4 5 2E x c h a n g e t i m e : 6 0 h



log|R|


Value Standard Errorlog |R| Intercept -0.00409 0.02097log |R| Slope 3.16607 0.11006

Figure S12: Plots and linear fits of log|R| versus the magnitude of applied bias after 36 hand 60 h exchange for FSC11 SAM preparation. The plots of log |R| versus |V | for SAMsof FSC11 at different exchange times (i.e., 36 h and 60 h) gave almost the same slope andsimilar deduced value of R at ±1.0 V, validating the extrapolated value of |R|obsd = 940employed in the main text.

S15

Figure S13: profiles of water contact angle of SC10 SAM (left, before exchange) and FSC11SAM (right, after exchange).

Figure S14: UV-vis absorption spectrum of FSC11, which enabled the estimation of HOMO-LUMO gap (Ef). Inset shows the determination of onset wavelength to be 718.13 nm, fromwhich Ef is extrapolated to be 1.73 eV.

S16

UPS data (bg subtracted)

multiple peak fit

fit HOMO

fit HOMO-1

9 8 7 6 5 4 30

500

1000

1500

2000

2500

3000

3500

Binding energy (eV)

Intensity

(counts/s)

EfermiHOMO

HOMOonset

Figure S15: UPS of the FSC11 SAM, relevant energy levels are determined to be: Vacuumlevel: 0 eV; Fermi level: -3.57 eV; HOMO onset: -5.45 eV.

Figure S16: AFM height profiles of (left) the pure alkanethiol SAM (that is before exchange)and (right) FSC11 SAM (after exchange, the surface of which is comparable to that in thepaper.S8 Both films looks like relatively smooth (Ra ≈ 1nm). Although the differencebefore and after exchange is obvious, One could hardly draw definitive conclusions aboutthe distribution of fullerenes since, in our hands, AFM is only barely capable of resolving 15nm-wide protein complexesS9 and C60 is nominally 1 nm in diameter. There are qualitativedifferences before and after exchange, certainly, and there are randomly-distributed spheroidsin the post-exchange AFM, which could not be overinterpreted thus far.

S17

3.4 NMR spectra

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5f1 (ppm)

PC11SAc-H

14.0

04.

442.

58

2.62

3.19

2.35

1.22

1.17

1.26

2.28

2.34

1.52

1.69

1.73

1.75

1.97

1.98

2.00

2.48

3.01

4.10

4.11

4.13

4.45

4.47

5.07

5.15

5.17

7.04

7.06

7.84

Figure S17: 1H NMR spectrum of FSC11-Ac

S18

-100102030405060708090100110120130140150160170180190200210220f1 (ppm)

PC11SAcC_d2o_CARBON_20160828112617

29.5

432

.20

32.3

232

.54

32.7

432

.84

32.9

032

.94

32.9

933

.07

33.1

342

.88

70.6

071

.67

72.8

680

.20

85.9

7

117.

5013

1.24

133.

1313

8.63

139.

4813

9.64

142.

4614

2.84

143.

0014

3.06

144.

8614

4.94

144.

9814

5.42

147.

2114

7.52

148.

7414

8.93

150.

0815

6.34

156.

4315

6.77

159.

1316

2.07

Figure S18: 13C NMR spectrum of FSC11

S19

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

PC11SH-H

12.3

22.

032.

832.

21

2.00

3.09

2.23

1.17

1.16

1.02

2.14

2.22

1.27

1.30

1.32

1.34

1.42

1.44

1.56

1.57

1.59

1.61

1.73

1.74

1.76

1.78

1.80

2.48

2.50

2.52

2.54

2.79

3.93

3.95

3.96

4.23

4.25

4.88

4.96

4.98

6.93

6.95

7.69

Figure S19: 1H NMR spectrum of FSC11

S20

-100102030405060708090100110120130140150160170180190200210220f1 (ppm)

PC11SHC_cdcl3_CARBON_20160603171611

27.3

328

.73

31.0

331

.72

31.9

832

.07

32.1

532

.16

32.1

936

.69

42.6

6

70.6

471

.60

72.6

1

85.8

6

133.

1113

8.42

142.

2214

2.55

144.

6214

4.76

144.

8114

5.20

145.

2114

5.23

147.

0414

8.59

149.

9414

9.95

156.

3115

6.75

159.

0216

1.86

Figure S20: 13C NMR spectrum of FSC11

S21

References

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(S2) Maggini, M.; Scorrano, G.; Prato, M. Addition of Azomethine Ylides to C60: Synthesis,

Characterization, and Functionalization of Fullerene Pyrrolidines. J. Am. Chem. Soc.

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(S3) Baumhof, P.; Mazitschek, R.; Giannis, A. A Mild and Effective Method for the Trans-

esterification of Carboxylic Acid Esters. Angew. Chem., Int. Ed. 2001, 40, 3672–3674.

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Gold Electrode Incorporating Corrole as an Ion-Channel Mimetic Sensor for Determi-

nation of Dopamine. Analytical chemistry 2009, 81, 7397–7405.

(S6) Tsukruk, V. V.; Lander, L. M.; Brittain, W. J. Atomic Force Microscopy of C60 Tethered

to a Self-Assembled Monolayer. Langmuir 1994, 10, 996–999.

(S7) Li, W.; Virtanen, J. A.; Penner, R. M. Self-Assembly of N-Alkanethiolate Monolayers on

Silver Nanostructures: Determination of the Apparent Thickness of the Monolayer by

Scanning Tunneling Microscopy. The Journal of Physical Chemistry 1994, 98, 11751–

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(S8) Itoh, Y.; Kim, B.; Gearba, R. I.; Tremblay, N. J.; Pindak, R.; Matsuo, Y.; Naka-

mura, E.; Nuckolls, C. Simple formation of C60 and C60-ferrocene conjugated mono-

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layers anchored onto silicon oxide with five carboxylic acids and their transistor appli-

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(S9) Castaneda Ocampo, O. E.; Gordiichuk, P.; Catarci, S.; Gautier, D. A.; Herrmann, A.;

Chiechi, R. C. Mechanism of Orientation-Dependent Asymmetric Charge Transport in

Tunneling Junctions Comprising Photosystem I. J. Am. Chem. Soc. 2015, 137, 8419–

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