METHOD OF PREPARATION OF A GOLD ELECTRODE

Abstract

A method of preparation of a gold electrode, which includes the steps of: a) inkjet printing on a substrate an ink including gold nanoparticles functionalized with a compound Cap of formula (I) HS-A-Polyalkylene glycol (I), wherein A is a bound or an alkyl chain having 1 to 12 carbon atoms and wherein polyalkylene glycol is polyethylene glycol, polypropylene glycol or a mixture thereof; and b) annealing printed ink, wherein the compound Cap has an average molar mass of less than 500 g/mol, preferably an average molar mass of about 200 g/mol. Also, an electrode obtainable by the method of the invention, a sensor including the electrode and the use of the sensor.

Claims

1-15. (canceled)

16. A method of preparation of a gold electrode comprising the steps of: a) inkjet printing on a substrate an ink comprising gold nanoparticles functionalized with a compound Cap of formula (I)
HS-A-Polyalkylene glycol  (I)  wherein A is a bound or an alkyl chain comprising 1 to 12 carbon atoms;  wherein polyalkylene glycol is polyethylene glycol, polypropylene glycol, or a mixture thereof; and b) annealing printed ink; wherein the compound Cap has an average molar mass of less than 500 g/mol, preferably an average molar mass of about 200 g/mol.

17. The method according to claim 16, wherein the printed ink is annealed at a temperature ranging from 200 to 300° C. for 30 minutes to 2 hours.

18. The method according to claim 16, wherein the printed ink is annealed by using pulsed light from a flashlamp.

19. The method according to claim 16, wherein the ink is a suspension of gold nanoparticles functionalized with said compound Cap in a hydroalcoholic medium.

20. The method according to claim 16, wherein steps (a) and (b) are repeated at least twice, preferably steps (a) and (b) are repeated at least four times.

21. The method according to claim 16, further comprising a step of sterilization.

22. The method according to claim 16, further comprising a functionalization step, wherein the gold electrode is functionalized with a biological molecule or a catalyst.

23. The method according to claim 16, wherein the substrate is organic, inorganic or hybrid.

24. The method according to claim 16, wherein the substrate is flexible.

25. The method according to claim 16, wherein the substrate comprises polyimide, polyethylenenaphtalate, glass, silicon dioxide, or a mixture thereof.

26. An electrode obtainable by the method according to claim 16.

27. The electrode according to claim 26, exhibiting a conductivity greater or equal to 1×10.sup.7 S/m.

28. The electrode according to claim 27, having a thickness ranging from 450 to 550 nm.

29. A sensor comprising at least one electrode according to claim 26, wherein said electrode is functionalized with a biological molecule or a catalyst.

30. A method for detection of diabetes markers in a subject, comprising detecting detection of glucose, any other diabetes related analytes, lactate, cholesterol, glycated hemoglobin (HbA1c) or a mixture thereof with a sensor according to claim 29.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 shows cyclic voltammograms of an electrode comprising 4 gold layers prepared by the method of the invention: (a) in acetonitrile+0.1 M Tetrabutylammonium hexafluorophosphate (TBAPF.sub.6) as supporting electrolyte and (b) in acetonitrile+1 mM ferrocene+0.1 M TBAPF.sub.6 as supporting electrolyte (scan rate: 100 mV/s). Inset: cyclic voltammogram of the electrode at 100 mV/s in 0.5 M H.sub.2SO.sub.4. J (mA.Math.cm.sup.−2) is the current density, and E (V/SCE) is the electrochemical potential expressed in the unit of Volt/saturated calomel electrode.

[0077] FIG. 2 is a scanning electron microscopy (SEM) image of a printed ink thermally annealed at 220° C. for one hour. Scale bar is 200 nm.

[0078] FIG. 3 is a scanning electron microscopy (SEM) image of a printed ink photonically annealed under 3 successive light pulses of 180 μs from a Xenon lamp. Scale bar is 200 nm.

EXAMPLES

[0079] The present invention is further illustrated by the following examples.

Example 1: Ink Formulation

[0080] Gold Nanoparticles Synthesis

[0081] 0.225 mmol of HAuCl.sub.4.3H.sub.2O were dissolved in 30 mL of methanol and 5 mL of acetic acid, followed by the addition of 0.1 mmol of compound S-PEG.sub.200. Once completely dissolved, 2 mmol of freshly prepared NaBH.sub.4 in 5 mL of water were added dropwise. The mixture was stirred for two hours at room temperature. After evaporation of solvent, the nanoparticles were purified by dialysis in deionized water using a 12 kDa cut-off membrane and then lyophilized for two days. Said nanoparticles have a size ranging from 2 to 5 nm.

[0082] The ink was prepared by suspending the obtained nanoparticles in a mixed solution of deionized water and ethanol (60:40 v/v) to a concentration of 76 mg.Math.mL.sup.−1.

Example 2: Preparation of a Gold Electrode on a Polyimide Substrate

[0083] A polyimide substrate was cleaned sequentially with acetone, water and isopropanol and was annealed at 220° C. for one hour.

[0084] The previously obtained ink was printed using a Dimatix Materials Printer (FUJIFILM DIMATIX DMP-2850) with 10 pL-droplet cartridges on the polyimide substrate. The ink was printed using 15 μm drop spacing with jetting frequency of 2 kHz. The platform of the printer and the cartridge temperatures were 40° C. and 28° C., respectively. The printed ink was then thermally annealed at 220° C. for one hour.

[0085] FIG. 2 shows the roughness of the thermally annealed printed ink. The obtained roughness factor is 5.

Example 3: Electrode Comprising 4 Gold Layers

[0086] The previously obtained ink was printed using a Dimatix Materials Printer (FUJIFILM DIMATIX DMP-2850) with 10 pL-droplet cartridges on the polyimide substrate. The ink was printed using 15 μm drop spacing with jetting frequency of 2 kHz. The platform of the printer and the cartridge temperatures were 40 and 28° C., respectively. The printed ink was then thermally annealed at 220° C. for one hour, this resulted in a single layer of S-PEG.sub.200 functionalized gold nanoparticles on the substrate. A second, third and fourth layers were successively printed and annealed at 220° C. for one hour.

[0087] An electrical resistivity of (2.0±0.1)×10.sup.−1 Ω.Math.m and (1±0.1)×10.sup.−7 Ω.Math.m, i.e. (2.0±0.1)×10.sup.1 S.Math.m.sup.−1 and (1±0.1)×10.sup.7 S.Math.m.sup.−1 respectively, is obtained for electrodes comprising 2 and 4 layers, respectively.

[0088] The thickness of the gold electrodes with 2 and 4 layers, determined by optical profilometry, is respectively 200 and 518 nm.

[0089] A sheet resistance of 10.sup.6 and 0.22 Ω/sq for gold electrodes of 2 and 4 layers, respectively, is estimated. The 4-layers electrode shows extremely low sheet resistance close to that of bulk gold.

[0090] FIG. 1 shows the electrochemical behavior of a 4-layers electrode in 0.5 M H.sub.2SO.sub.4 medium. A classical gold polycrystalline behavior is observed with the presence of a broad oxidation peak located at 1.3 V and a sharp cathodic peak at 0.8 V/SCE. The cyclic voltammetry performed at different scanning rates in a buffered aqueous solution (PBS) leads to the measure of a differential capacitance of 0.2 mF/cm.sup.2. This value is greater than what is conventionally encountered in polycrystalline gold due to the high specific printed gold surface area.

[0091] Gold electrodes consisting of 4 printed layers exhibited a conductivity of (1±0.1)×10.sup.7 S/m, close to that of Au bulk, after low-temperature thermal annealing.

Example 4: Functionalization of an Electrode

[0092] Two 4-layers electrodes previously obtained were immersed in 6,6′-disulfanediylbis(hexane-6,1-diyOdiferrocenecarboxylate for 35 minutes and 22 hours respectively. The cyclic voltammograms of the electrodes showed the presence of a reversible system corresponding to the ferrocene function, demonstrating the efficient functionalization of the electrodes with ferrocene.

Example 5: Sensor Fabrication

[0093] Three electrodes from example 2 were used.

[0094] A polymer solution containing Glucose Oxydase, a nitrogen-based redox polymer and a reticulating agent were then deposited on top of one gold electrode (working electrode). An Ag/AgCl based screen printing paste was deposited on top of a second gold electrode (reference electrode). The third gold electrode was used without further modification (counter electrode). The three combined electrodes form a typical amperometric glucose sensor.

Example 6: Preparation of a Gold Electrode on a Polyimide Substrate by Photonic Annealing

[0095] A polyimide substrate was cleaned sequentially with acetone, water and isopropanol and was annealed at 220° C. for one hour.

[0096] The previously obtained ink was printed using a Dimatix Materials Printer (FUJIFILM DIMATIX DMP-2850) with 10 pL-droplet cartridges on the polyimide substrate. The ink was printed using 15 μm drop spacing with jetting frequency of 2 kHz. The platform of the printer and the cartridge temperatures were 40° C. and 28° C., respectively. The printed ink was then submitted to 3 successive light pulses of 180 μs with the following parameters: XENON-X1100 system associated with a reference annealing chamber XENON LC-912, Voltage=2800 V, Energy=350 J, distance between the printed ink and the lamp is about 5 cm.

[0097] FIG. 3 shows the roughness of the photonically annealed printed ink. The obtained roughness factor is 3.