“Clickable” graphene nanoribbons for biosensor interfaces

We report on the synthesis of “clickable” graphene nanoribbons (GNRs) and their application as a versatile interface for electrochemical biosensors. GNRs are successfully deposited on gold-coated working electrodes and serve as a platform for the covalent anchoring of a bioreceptor (i.e., a DNA aptamer), enabling selective and sensitive detection of Interleukin 6 (IL6). Moreover, when applied as the intermediate linker on reduced graphene oxide (rGO)-based field-effect transistors (FETs), the GNRs provide improved robustness compared to conventional aromatic bi-functional linker molecules. GNRs enable an orthogonal and covalent attachment of a recognition unit with a considerably higher probe density than previously established methods. Interestingly, we demonstrate that GNRs introduce photoluminescence (PL) when applied to rGO-based FETs, paving the way toward the simultaneous optical and electronic probing of the attached biointerface.


TIPS-GNR (10)
GNR 9 (23.0 mg, 22.6 µmol) and CuI (0.429 mg, 2.25 µmol, 0.1 eq) were dissolved in a solvent mixture of dry and oxygen-free THF (9 mL)and NEt3 (6 mL).The dispersion was treated by sonication for 5 minutes and then the catalyst Pd(PPh3)4 (3.91 mg, 3.38 µmol, 0.15 eq) was added under argon flow.The mixture was degassed for 10 minutes, followed by the addition of ethynyltriisopropylsilane (20.6 mg, 0.113 mmol, 5 eq).The reaction mixture was stirred at 70 °C for 72 hours.The solution was cooled to room temperature, and the resulting material was subjected to filtration and subsequently washed with tetrahydrofuran (THF) and methanol.The GNR was then dissolved in THF and underwent a 10-minute sonication, followed by filtration and additional washes.This entire process was repeated multiple times to thoroughly eliminate any remaining impurities.The desired GNR was yielded as a dark violet powder (21 mg, 86%).The GNR was used without further characterization in the next synthetic step.Eq.S1

Characterization of "clickable" GNRs applied as biointerface
where λL is the laser wavelength (nm),  D the intensity of the D band, and  G the intensity of the G band.

Radial breathing-like mode (RBLM):
The wavenumber of the RBLM, νRBLM, is nearly independent of the edge structure and can be roughly correlated with the GNR width, w (Å), according to 2 Eq. S3  S1.
The employed circuit was previously reported for the fitting of EIS measurements of different IL6 Auaptamer electrochemical biosensors. 3,4Briefly, the circuit consist of a solution resistance (Rs) connected in series to two parallel branches containing, in one side, a constant phase element (CPE), and in the other branch a series connection of the charge transfer resistance (Rct) and a Warburg impedance (Zw), which accounts for the diffusion of the redox couple. 4-(Anthracen-9-yl)phenyl)-5-(4-iodophenyl)-3-phenyl-4-(3-(

Figure S11 .
Figure S11.High-resolution XPS S2p signal of the SAM-coated gold working electrode.

Figure S14 .
Figure S14.Peak current variation as function of the scan rate.

Figure S15 .
Figure S15.Bode (a) and Nyquist (b) plots with the respective fitting of the EIS spectrum for 2.1 nM IL6. Circuit employed for the fitting of the EIS spectra (c).

Figure S16 .Figure S18 .
Figure S16.Magnification at low concentrations of the response curves obtained from DPV (red -signal suppression) and EIS (blue -phase angle shift) for the IL6 binding.Dashed lines indicate the fitting of the signals with the Hill model.

Table S1 .
Results for the fitting of the EIS spectra.