Electrochemical sensor in configuration thereof

1 . A method of determining the presence and/or concentration of hydrogen peroxide in an aqueous solution using an electrochemical sensor comprising:

i. a front porous electrode comprising pores permeable to the aqueous solution and comprising a sensitive surface which is sensitive to the hydrogen peroxide;

ii. an electrolytic conductor bridge permeable to the aqueous solution; and

iii. a back electrode comprising at least a surface and optionally a support;

wherein the front electrode and the back electrode are electrically connected via the electrolytic conductor bridge; wherein the front electrode comprises pores above 0.2 μm of equivalent diameter that connect the external surface of the front electrode and the electrolytic conductor bridge;

wherein the sensitive surface of the front porous electrode is a hydrogen peroxide sensitive surface and is selected from the group consisting of: copper, nickel, Prussian blue-coated materials, Prussian blue-coated composites, palladium, palladium nanomaterials and platinum or platinum derivatives;

wherein the electrochemical sensor is configured so that the aqueous solution only enters in contact with the back electrode through the electrolytic conductor bridge, which in turn only enters in contact with the aqueous solution through the pores of the front electrode;

wherein the electrochemical sensor further comprises means for determining the difference in the electrochemical state between the front electrode and the back electrode;

and wherein the determination of such difference in the electrochemical state indicates the hydrogen peroxide presence and/or concentration in the aqueous solution;

the method comprising:

a. contacting the aqueous solution with the sensitive surface of the front electrode of the electrochemical sensor;

b. determining the difference in the electrochemical state between the front electrode and the back electrode; and

c. determining the presence and/or concentration of the hydrogen peroxide in the aqueous solution based on the difference in the electrochemical state.

2 . The method according to claim 1 , wherein the front electrode of the electrochemical sensor comprises a pore density configured to provide a Herzberg flow rate lower than 2500 s/100 mL.

3 . The method according to claim 1 , wherein the front electrode of the electrochemical sensor comprises pores between 0.2 μm and 50 μm.

4 . The method according to claim 1 , wherein the electrochemical sensor is a current-based sensor; wherein the front electrode is the working electrode and the back electrode is the counter electrode; wherein the counter electrode carries out a complementary Faradaic reaction to the reaction carried out in the working electrode; and wherein the means for determining the difference in the electrochemical state is connected between the front electrode and the back electrode and configured to measure a current flowing between the front electrode and the back electrode.

5 . The method according to claim 4 , wherein the current-based sensor employs the energy generated at the interface of the front electrode when in contact with the aqueous solution to power the sensor.

6 . The method according to claim 4 , wherein the current-based sensor further comprises a voltage source connected between the front electrode and the back electrode configured to apply a potential between the electrodes.

7 . The method according to claim 4 , wherein the electrolytic conductor bridge of the current-based sensor connecting the electrodes is selected from any of the following list consisting of: a polyelectrolyte, a solid polymer electrolyte, an ionogel and a ionomer such as tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

8 . The method according to claim 4 , wherein the back electrode of the current-based sensor comprises a conductive material selected from any of the following list consisting of: zinc, silver/silver chloride, conducting polymers such as PEDOT-PSS and platinum or platinum derivatives such as platinum-coated carbon materials and platinum nanomaterials.

9 . The method according to claim 4 , wherein the hydrogen peroxide sensitive surface of the front electrode and the back electrode of the current-based sensor comprise or are made of platinum.

10 . The method according to claim 4 , wherein the hydrogen peroxide sensitive surface of the front electrode and the back electrode of the current-based sensor comprise or are made of platinum and wherein the electrolytic conductor bridge is tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

11 . The method according to claim 1 , wherein the electrochemical sensor is a potential-based sensor; wherein the front electrode is the working electrode and the back electrode is the reference electrode; wherein the reference electrode provides a stable potential; and wherein the means for determining the difference in the electrochemical state connected between the front electrode and the back electrode and configured to measure the difference in voltage between the front electrode and the back electrode.

12 . The method according to claim 11 , wherein the electrolytic conductor bridge ( 14 ) of the potential-based sensor connecting the electrodes is selected from any of the following list consisting of: a polyelectrolyte, a solid polymer electrolyte, an ionogel and a ionomer such as tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

13 . The method according to claim 11 , wherein the reference electrode of the potential-based sensor comprises a conductive material selected from any of the following list consisting of: silver, platinum, gold, nickel, zinc, copper, silver/silver chloride, conducting polymers such as PEDOT-PSS, aluminium and carbon.

14 . The method according to claim 11 , wherein the hydrogen peroxide sensitive surface of the front electrode and the back electrode of the potential-based sensor comprise or are made of platinum.

15 . The method according to claim 11 , wherein the hydrogen peroxide sensitive surface of the front electrode and the back electrode of the potential-based sensor comprise or are made of platinum and wherein the electrolytic conductor bridge is tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer.

16 . The method according to claim 1 , wherein the front electrode and/or the back electrode of the electrochemical sensor further comprise a support which in turn comprises a conductive material.

17 . The method according to claim 1 , wherein the front electrode, the electrolytic conductor bridge and the back electrode of the electrochemical sensor are configured so that these are stacked.

18 . The method according to claim 1 , wherein the method further determines the presence and/or concentration of a target analyte through the measurement of hydrogen peroxide;

wherein the front electrode of the electrochemical sensor is functionalized with an oxidase or dehydrogenase enzyme selected from the group consisting of glucose oxidase, glucose dehydrogenase, cholesterol oxidase, cholesterol dehydrogenase, lactate oxidase, lactate dehydrogenase, bilirubin oxidase, bilirubin dehydrogenase, amino acids oxidase and amino acids dehydrogenase;

wherein the front electrode of the electrochemical sensor is configured to produce hydrogen peroxide when in contact with the target analyte that the electrochemical sensor measures; and

wherein the method further comprises

determining the presence and/or concentration of the target analyte in the aqueous solution based on the determined concentration of hydrogen peroxide.

19 . The method according to claim 1 , wherein the method further determines the presence and/or concentration of a target analyte in an aqueous solution through the measurement of hydrogen peroxide;

wherein the electrochemical sensor is functionalised with a capture entity that captures the target analyte if present;

wherein the electrochemical sensor further comprises means for detecting the target analyte wherein said means are at least a detection entity and a substrate and wherein said detection entity is capable of detecting the target analyte and is labelled with an enzyme capable of producing hydrogen peroxide when exposed to the substrate, and wherein the method further comprises:

a. contacting the sensitive surface of the front electrode of the electrochemical sensor with the detection entity so that the detection entity binds to the target analyte if present;

b. optionally rinsing the sensitive surface; and adding the substrate so as to produce hydrogen peroxide if the detection entity is present;

c. determining the presence and/or concentration of the target analyte in the aqueous solution based on the difference in the electrochemical state.