ES2589049B2 - Electrochemical device for the analysis of the chemical composition of samples and method for manufacturing an electrode paper sheet - Google Patents

Abstract

Electrochemical device for the analysis of the chemical composition of samples and method for manufacturing an electrode paper sheet. The device comprises a disposable electrode paper sheet (LPE) with a working electrode (WE) that temporarily adheres to a support electrode platform (PE) with a reference electrode (RE), an auxiliary electrode (AE), means of connection (CN) with a system of feeding and registry of data and a zone of contact (ZC). The invention also comprises methods for manufacturing the electrode paper sheet (LPE) and for including metal nanoparticles and / or carbon nanomaterials in the working electrode (WE) of said sheet. # The invention is applicable in the detection, identification and quantification of chemical and biochemical substances, mainly in the sectors of clinical, environmental or agri-food analysis.

Description

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ELECTROCHEMICAL DEVICE FOR THE ANALYSIS OF THE OUIMIC COMPOSITION OF SAMPLES AND METHOD FOR MANUFACTURING AN ELECTRODE PAPER SHEET

The present invention relates to an electrochemical device comprising a sheet of electrodic paper temporarily adhered to a support electrode platform and a method for manufacturing a sheet of adhesive electrode paper. The electrochemical device thus constructed contains the working electrode (WE) in the sheet of electrodic paper and the auxiliary (AE) and reference electrodes (RE) in the support electrode platform. The electrodic paper sheet is disposable after use, leaving the electrodic support platform in its initial state for reuse along with a new sheet of electrodic paper. The sheet of electrodic paper can be modified with different micro or nanomaterials that improve its characteristics for the detection of various substances of interest. The method gives rise to electro-paper sheets, which, attached to a support electrode platform, thus configure the electrochemical device that can be used as a transducer in the development of electrochemical sensors and biosensors.

The invention results from application in the detection, identification and quantification of chemical and biochemical substances, mainly in the sectors of clinical, environmental or agri-food analysis.

STATE OF THE TECHNIQUE

Interest in paper-based microfluidic analytical devices has grown greatly since the group of G. Whitesides introduced the role in microfluidic systems in 2007 (Andres W. Martinez, Scott T. Phillips, Manish J. Butter, George M. Whitesides, Patterned paper as a platform for inexpensive, low-volume, portable bioassays, Angewante Chemical International Edition 2007, 46, 1318-1320; Andres W. Martinez, Scott T. Phillips, Benjamin J. Wiley, Malancha Gupta, George M. Whitesides, FLASH: A rapid method for prototyping paper-based microfluidic devices, Lab on a Chip 2008, 8, 2146-2150).

These analytical devices are very attractive due to their low cost, simplicity, flexibility and their possibility of being discarded. The paper is easy to transport, store and handle, and being mainly made of cellulose, it also allows it to be modified with a large number of functional groups that can be covalently linked to proteins, DNA and small molecules (Robert Pelton, Bioactive paper provides a low-cost platform for diagnostics, Trends in Analytical Chemistry 2009, 28, 925-942).

Electrochemical detection has proved to be one of the most suitable for its integration into paper devices due to the high sensitivity, selectivity and 10 miniaturization capacity it presents (Anni Maattanen, Ulriika Vanamo, Petri Ihalainen, Petri Pulkkinen, Heikki Tenhu, Johan Bobacka , Jouko Peltonen, A low-cost paper-based inkjet-printed platform for electrochemical analyzes, Sensors and Actuators B: Chemical 2013, 177, 153-162; Wijitar Dungchai, Orawon Chailapakul, Charles S. Henry, Electrochemical detection for paper-based microfluidics, Analytical 15 Chemistry 2009, 81, 5821-5826). There are numerous scientific articles describing paper-based electrochemical devices (David M. Cate, Jaclyn A. Adkins, Jaruwan Mettakoonpitak, Charles S. Henry, Recent developments in paper-based microfluidic devices, Analytical Chemistry 2015, 87, 19-41). The most common technique for the manufacture or integration of electrodes in paper devices is printing, where ink or paste is deposited by pressure using a screen or mask {screen-printed) or by means of a template {stencil-printed) ( Wijitar Dungchai, Orawon Chailapakul, Charles S. Henry, Electrochemical detection for paper-based micro fluidics, Analytical Chemistry 2009, 81, 5821-5826; Wen-Jie Lan, E. Jane Maxwell, Claudio Parolo, David K. Bwambok, Anand Bala Subramaniam, George M, 25 Whitesides, Paper-based electroanalytical devices with an integrated, stable reference electrode. Lab on a Chip 2013, 13, 4103-4108). The use of wax to design the shape and size of the electrochemical cell is also somewhat known (Murilo Santhiago, John B. Wydallis, Lauro T. Kubota, Charles S. Henry, Construction and electrochemical characterization of microelectrodes for improved sensitivity in paper- 30 based analytical devices, Analytical Chemistry 2013, 85, 5233-5239). Carbon inks are the most used materials for the development of electrodes in paper devices, but other materials such as gold or silver inks are also used (W.R.

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Araujo, T.R.L.C. Paixao, Fabrication of disposable electrochemical devices using silver ink and office paper, Analyst 2014, 139, 2742-2747; Wijitar Dungchai, Orawon Chailapakul, Charles S. Henry, Electrochemical detection for paper-based microfluidics, Analytical Chemistry 2009, 81, 5821-5826; Anni Maattanen, Ulriika Vanamo, Petri Ihalainen, Petri Pulkkinen, Heikki Tenhu, Johan Bobacka, Jouko Peltonen, A low-cost paper-based inkjet-printed platform for electrochemical analyzes, Sensors and Actuators B: Chemical 2013, 177, 153-162) .

The electrochemical paper devices present different problems at present, two of the most important being the robustness of the connection to the measuring instrument and the irreproducibility in the manufacture of the reference electrode used. As for the connection to the measuring instrument, this is usually done directly using conductive clamps (Murilo Santhiago, John B. Wydallis, Lauro T. Kubota, Charles S. Henry, Construction and electrochemical characterization of microelectrodes for improved sensitivity in paper-based analytical devices, Analytical Chemistry 2013, 85, 5233-5239; Nicolo Dossi, Rosanna Toniolo, Flavia Impellizzieri, Gino Bontempelli, Doped pencil leads for drawing modified electrodes on paper-based electrochemical devices, Journal of Electroanalytical Chemistry 2014, 722-723, 90 -94) that can add a lot of mechanical stress to the paper, or also directly with connectors manufactured in the same laboratory. The fragility, flexibility and lightness of the paper mean that, through direct connection, the paper can become deformed by increasing the electrical resistance of the device as it does not have a robust connection and, in addition, could vary between each device used. On the other hand, the manufacture of reference electrodes on paper is a problem at present, since for a constant electrical potential to be applied in an electrochemical cell, the reference electrode must be very stable and reproducible. Its manufacture in a paper substrate can vary between electrodes making the applied potential different for each device and, therefore, the reproducibility in the measurements is low.

There are numerous commercial electronic platforms mass-produced in a very reproducible way and whose operation has been widely verified, there are also accessories and connectors specific to them that allow a connection between the device and the measuring instrument very robust, of great

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efficiency and with a low electrical resistance. The use of some of these paper-coupled platforms has been previously published (Fen-Ying Kong, Sai-Xi Gu, Wei-Wei Li, Ting-Ting Chen, Qin Xu, Wei Wang, A paper disk equipped with graphene / polyaniline / Au nanoparticles / glucose oxidase biocomposite modified screen-printed electrode: Toward whole blood glucose determination, Biosensors and Bioelectronics 2014, 56, 77-82; Julaluk Noiphung, Temsiri Songjaroen, Wijitar Dungchai, Charles S. Henry, Orawon Chailapakul, Wanida Laiwattanapaisal, Electrochemical detection of glucose from whole blood using paper-based microfluidic devices, Analytica Chimica Acta 2013, 788, 39-45; Nadia Chandra Sekar, Seyed Ali Mousavi Shaegh, Sum Huan Ng, Liya Ge, Swee Ngin Tan, A paper-based amperometric glucose biosensor developed with Prussian blue-modified screen- printed electrodes, Sensors and Actuators B: Chemical 2014, 204, 414-420). However, in these cases, the paper has only been used with the function of preconcentrating the analyte, avoiding matrix effects of the sample or immobilizing reagents. In none of the published cases where paper is attached to a conductive support platform, does the paper function as a working electrode, since it does not have a conductive phase.

DESCRIPTION OF THE INVENTION

The present invention relates to a new electrochemical device based on a sheet of electrodic paper to be used by temporarily adhering it on a support electrode platform. The electrodic paper sheet contains the working electrode of the electrochemical device. The invention also relates to a method of manufacturing the electrochemical paper sheet of the electrochemical device.

One aspect of the invention is therefore an electrochemical device for the analysis of the chemical composition of samples comprising a working electrode on an electrodic paper sheet, and a reference electrode, an auxiliary electrode and connection means with a system. of feeding and recording data in an electrodic support platform, which also includes a contact area. The working electrode of the device is comprised of a sheet of electrodic paper, and is an area with a carbon substrate that is limited by one way.

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closed geometric wax printed on one side and diffused to the opposite side of the sheet of electrodic paper forming a closed geometric shape on both sides. The electrode paper sheet is temporarily adhered to the support electrode platform so that the working electrode of the electrode paper sheet is disposed on the surface of a contact area of the support electrode platform, maintaining contact between both surfaces. The support electrode platform in turn comprises a reference electrode, an auxiliary electrode, a contact area on which the electrode paper sheet is arranged and connection means with a data recording and feeding system.

For the purposes of this invention and its description, one skilled in the art can understand that the term wax is equivalent to any material suitable for printing on paper and its subsequent diffusion, creating a closed geometric shape on both sides of the paper sheet . Some examples besides wax can be resins, inks, polymers, elastomers or other hybrid materials.

In a preferred embodiment, the closed geometry that is printed on the sheet of electrodic paper is a ring. In a more preferred embodiment, the ring has an inside diameter of between 1 and 10 mm.

In another preferred embodiment, the carbon substrate of the working electrode comprised in the sheet of electrodic paper is a graphite composition.

In another preferred embodiment, the carbon substrate of the working electrode comprised in the sheet of electrodic paper is a composition of carbon nanomaterials.

In another preferred embodiment, the electrodic paper sheet also comprises metal nanoparticles arranged in the working electrode by electrodeposition or adsorption. In a more preferred embodiment, the metal nanoparticles are silver, gold, nickel, platinum, palladium or bismuth.

In another preferred embodiment, the electrodic paper sheet also comprises carbon nanomaterials arranged in the working electrode by electrodeposition or adsorption.

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In a more preferred embodiment of the device where the carbon substrate of the working electrode comprised in the electrodic paper sheet is a composition of carbon nanomaterials or of the device where the working electrode of the electrode paper sheet also comprises carbon nanomaterials arranged by electrodeposition or adsorption, the carbon nanomaterials are graphene, nanofibers or carbon nanotubes.

In another preferred embodiment, the electrodic paper sheet is temporarily adhered to the support electrode platform by means of a pressure sensitive adhesive (PSA) disposed on the electrode paper sheet.

For the purposes of this invention and its description, a pressure sensitive adhesive, also known by the acronym PSA (Pressure-sensitive adhesive), is one that forms a joint when a pressure is applied to adhere the adhesive and the adherent, without need to add a solvent, water, heat or other means to activate the adhesive.

In another preferred embodiment, the contact area located in the electrodic support platform on which the electrode paper sheet is arranged is an area comprising a conductive material electrically communicated with the connection means.

The adhesive part of the sheet of electrodic paper is made to coincide with an inert area of the support electrode platform so that, after its use and subsequent disposal, the adhesive does not alter the normal operation of the support electrode platform.

The connection of the electrochemical device with a system for feeding and recording data, such as a potentiostat, is done through the support electrode platform, which can be a commercial screen-printed card. The electrodic support platform comprises at least one auxiliary electrode, one reference and connection means. The electrodic support platform also comprises a contact area on which the sheet of electrodic paper is arranged according to the procedure explained below. In this way, the electrochemical device has the auxiliary and reference electrodes of the support electrode platform, and the working electrode of the paper sheet

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electrodica The positioning and fixing of the sheet of electrodic paper on the contact area of the support electrode platform can be carried out by means of an adhesive, the working electrode of the electrode paper sheet being arranged on the contact area of the support electrode platform . In this way, the electrodic paper sheet would only function as a working electrode and the contact area of the support platform only as a connection for that work electrode with the support electrode platform.

Another aspect of the invention is a method for manufacturing one or more sheets of electrode paper of the aforementioned electrochemical device comprising the following steps:

a) Print one or several geometric shapes closed with wax on a sheet of paper.

b) Disseminate the geometric shape or shapes to the opposite side of the sheet of paper by heating the sheet printed in step a) at a diffusion temperature until diffusion occurs.

c) Add a liquid suspension of carbon paste in the internal area delimited by the closed geometric shape or shapes.

d) Heat the sheet of paper with the closed geometric shape or shapes and the liquid suspension to at least the evaporation temperature of the solvents of the liquid suspension, leaving a carbon substrate inside each closed geometric shape forming an electrode of job.

e) Cover each working electrode with a protective layer, apply an adhesive to the rest of the surface of the paper sheet and remove the protective layer.

f) Cut the sheet of paper precisely around the closed geometric shape or shapes to obtain one or more sheets of electrodic paper.

g) Adhere the electro-paper sheet (LPE) to an electrodic support platform (PE) so that the working electrode (WE) of the electro-paper sheet (LPE) is arranged on the surface of the contact area (ZC ) of the electrodic support platform (PE) maintaining the

5 contact between both surfaces.

h) add a solution with a metal salt covering the electrodic paper sheet (LPE) and the reference (RE) and auxiliary (AE) electrodes of the support electrode platform (PE).

i) apply a current for salt reduction and electrodeposition

10 metal nanoparticles on the working electrode (WE) of the sheet

electro paper (LPE).

j) apply a potential for hydrogen desorption;

k) wash the assembly.

In a specific embodiment, the closed geometric shape is a ring. In a more specific embodiment, the ring has an inner diameter of between 1 and 10 mm.

In another specific embodiment, the diffusion temperature of step b) is between 100 ° C and 150 ° C and the diffusion time is between 50 and 120 seconds. These temperature and time intervals ensure a sufficient and controlled diffusion of the wax to obtain a closed geometric shape on both sides in most of the 20 paper compositions based on cellulose, with a high hydrophobic capacity and with the appropriate size for Subsequent modification with the carbon paste and its placement on the support electrode platform.

In another specific embodiment, the carbon paste is a graphite composition. Graphite allows to obtain sheets of electrodic paper with high electrical conductivity, robust and low cost.

In another specific embodiment, the carbon paste is a composition of carbon nanomaterials that allow the improvement of the electrochemical characteristics of the electrochemical device.

In a more specific embodiment, the liquid carbon pulp suspension of step c) is 2 pL of a 23% carbon solution in dimethylformamide. This proportion of carbon and volume of solution used ensures, using these substances, a uniform and reproducible working electrode surface.

5 In another specific embodiment, the evaporation temperature of the solvents

It is between 20 and 100 ° C and the evaporation time is between 15 minutes and 24 hours. These temperature and time intervals ensure, for a wide spectrum of solvents, their total evaporation from the liquid carbon paste suspension.

In another specific embodiment, the adhesive applied in step e) is pressure sensitive (PSA). This type of adhesive allows the easy adhesion of the sheet of electrodic paper to the support electrode platform in a reversible manner, facilitating its subsequent removal without deterioration of the support electrode platform.

In a more preferred embodiment, the solution of step h) is an aqueous solution and the salt is a metal salt of silver, gold, nickel, platinum, palladium or bismuth in a concentration of between 0.1 and 5 mM. The use of aqueous solutions of these metals in this range of concentrations allows the formation of nanoparticles in the working electrode of the sheet of electrodic paper.

In another more preferred embodiment, the current of step i) is between -10 and -300 pA for 15 and 300 seconds. These intervals of current and time ensure the formation of metal nanoparticles of the metals indicated above in the working electrode of the sheet of electrodic paper.

In another more preferred embodiment, the potential of step j) is between 0 and 0.5 V for 30 and 120 seconds. These intervals of potential and time ensure the desorption of hydrogen formed in the reduction of any of the aforementioned metals.

In another more preferred embodiment, the contact area located in the electrodic support platform on which the electrodic paper sheet is arranged is an area comprising a conductive material electrically communicated with the connection means of the electrodic support platform.

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In another preferred embodiment, the method further comprises the following steps, between step f) and g):

f.l) Add a liquid suspension of carbon nanomaterials on the opposite side to the working electrodes (WE) of the electrodic paper sheet (LPE).

f.2) Evaporate the solvent from the liquid suspension.

In another preferred embodiment, the method further comprises the following steps, between step b) and c):

b.l) Add a liquid suspension of carbon nanomaterials within the area limited by the closed geometric shape or shapes.

b.2) Heat the sheet of paper with the closed geometric form or shapes and the liquid suspension of nanomaterials to at least the evaporation temperature of the solvents of the liquid suspension, leaving a substrate of carbon nanomaterials inside the delimited area by the closed geometric form or shapes.

In a more specific embodiment of any of the embodiments of the method in which the liquid suspension contains carbon nanomaterials, the carbon nanomaterials are graphene, nanofibers or carbon nanotubes.

Several advantages can be obtained with the electrochemical device: the connection with the data feeding and recording system (for example a potentiostat) can be carried out using robust commercial connectors that work for the support electrode platform, eliminating the connection problem that Normally, they have the development and utilization of paper electrode devices. On the other hand, the electrochemical device uses the auxiliary and reference electrodes of the support electrode platform, which are electrodes manufactured in a reproducible manner and on a substrate more stable than paper. The sheet of electrodic paper thus manufactured is temporary and disposable, since it can be peeled off after use, leaving the electrodic support platform in the same initial conditions for the next use. The cost of the support electrode platform is much higher than that of the manufacture of the electro-paper sheets, so the use

of the same would constitute, in general, an important saving. In the development of electrochemical sensors, the most used methodology is the modification of the working electrode with substances necessary for the construction of the sensor part. However, these substances mean that the working electrode can only be used once after which the assembly should be discarded, although the rest of the support electrode platform could still be useful. Using the described technology, the sheet of electrodic paper can be discarded after performing the analysis, and a new sheet of adhesive electrodic paper would be placed for the next measurement. This allows efficient use of economic resources in the analytical sensor industry.

The electrochemical device thus developed allows its modification with different materials in a simple way to obtain analytical tools with different properties. The working electrode of the electrodic paper sheet can be modified with micro and nanomaterials of carbon dispersed in a solution such as graphite, graphene, nanofibers or carbon nanotubes. These

Nanomaterials can be added to the paper by two strategies: on the one hand, after printing and heating the wax with the appropriate closed geometric shape or shapes, a controlled volume of the dispersion would be added over the area bounded by the closed geometric shape or shapes. of nanomaterials 20 by for example a very precise automatic dispenser. In this way, the dispersion of nanomaterials would diffuse inside the area delimited by the closed geometric shape or shapes generating a paper modified with nanomaterials. After this step, it would be allowed to dry for a certain time and then, the carbon paste would be placed as explained previously in the interior of the area delimited by the closed geometric shape or shapes,

achieving the union of the conductive carbon substrate with the nanomaterial, and generating one or several working electrodes modified with nanomaterials. The rest of the manufacturing stages would be similar to the case of the unmodified electrodic paper sheet, as explained above. Another alternative would be the modification of the electrodic sheet or sheets of paper already manufactured with the carbon substrate. The dispersion of the nanomaterial would be added inside the area bounded by the closed geometric shape or forms but on the face opposite to the

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carbon substrate, generating one or several working electrodes modified with nanomaterials.

The modification with nanomaterials can confer some properties to the working electrodes that can be very useful in the development of sensors, such as a greater surface area, electrocatalytic effect of some substances or an increase in the speed of electronic transfer. However, if a conventional electrodic platform is modified with a nanomaterial, it is an irreversible process, and after performing the corresponding measurement, the platform would not return to the initial state. On the other hand, the modification with nanomaterials of the working electrode of the electrodic paper sheet described here would not damage the support electrode platform that would maintain its initial conditions for the next use with a new sheet of electrodic paper.

The working electrode of the electro-paper sheet comprising the electrochemical device object of the invention can also be modified with metal nanoparticles by adsorption of a dispersion of these nanoparticles or by electrodeposition. The electrodeposition can be carried out after the application of an electric current to a solution of a metal salt placed on the electrochemical device for a certain time. In this way, the metal in solution would be reduced by generating metal nanoparticles on the conductive part of the sheet of electrodic paper, that is, on the surface of the working electrode. The size, dispersion and quantity of nanoparticles that are generated could be controlled by varying the magnitude of excitation (electric current), the concentration of the salt used and the time during which the excitation is applied. This variant would allow to generate nanoparticles of different materials such as, for example, gold, silver, platinum, nickel, copper, bismuth, among others. The modification of the working electrode with this type of particles is useful in the development of electrochemical sensors and biosensors.

These devices, fully miniaturized and easily portable, are useful for the analysis, detection, identification and quantification of chemical and biochemical substances, such as neurotransmitters, phenolic compounds, amines, nitro compounds, amino acids, proteins, nucleic acids, ions or complexes.

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Metallic, being of great interest in the clinical, environmental and agri-food sector, among others.

DESCRIPTION OF THE FIGURES

Fig. 1 shows the scheme of a starting sheet of paper (HP) where closed geometric shapes (FG) are printed with wax in the form of rings that will be subject to the modification described in this invention.

Fig. 2 shows the scheme of Fig. 1 after diffusion of the wax by heating and the addition of the carbon paste in the inner zone of the rings. In Fig. 2A the starting sheet of paper (HP) is shown on the side on which the carbon substrate that formed the working electrodes (WE) has been deposited and in Fig. 2B the sheet of paper is represented (HP) starting from the opposite side. In later stages than those shown in this figure, once the carbon paste has been added, the paper sheet (HP) is heated until the working electrodes (WE) are obtained. Then, they are covered with a protective layer and adhesive is applied to the rest of the surface of the sheet of paper (HP) and the protective layer is removed. Finally, the sheet of paper (HP) is cut precisely around the closed geometric shapes (FG) to obtain several sheets of electrodic paper (LPE). In some described embodiments of the invention, metal nanoparticles and / or carbon nanomaterials are also included in the working electrode (WE).

Fig. 3A represents a diagram of a possible electrodic support platform (PE) that includes the auxiliary electrodes (AE) and reference (RE), the contact area (ZC) and the connections (CN) to the measurement system. In Fig. 3B the placement of the electrodic paper sheet (LPE) is shown on the face containing the working electrode (WE), on the contact area (ZC) of the support electrodic platform (PE). The sheet of electrodic paper (LPE) is folded, with one of its parts already adhered to the electrodic support platform (PE). In Fig. 3C the electrochemical device object of the invention is represented composed of the electrodic paper sheet (LPE) and the support electrode platform (PE).

Fig. 4 shows the cyclical voltamperograms (current intensity, measured in microamps (pA), vs. applied electrical potential, measured in volts (V)) of 250 pM of hexaminrutenium chloride (III) at different scanning speeds (50 , 100, 250 mV / s) in an electrochemical device consisting of an electrodic paper sheet (LPE) with working electrode (WE) composed of a carbon substrate placed on a support electrodic platform (PE) materialized with a ceramic screen printed card.

Fig. 5 shows the cyclic voltamperogram (current intensity, measured in microamps (pA), vs. applied electrical potential, measured in volts (V)) obtained 10 for 250 pM of dopamine in 0.1 M KC1 in an electrochemical device that is It consists of a sheet of electrodic paper (LPE) with working electrode (WE) composed of a carbon substrate and modified with gold nanoparticles (dotted line), and in one with a working electrode (WE) only composed of a Carbon substrate (continuous line), both placed on a ceramic screen printed card as an electronic support platform (PE).

Fig. 6 shows the cyclic voltamperogram (current intensity, measured in microamps (pA), vs. applied electrical potential, measured in volts (V)) obtained for 100 pM of dopamine in 0.1 M H2SO4 in three electrochemical devices. An electrochemical device is composed of an electrodic paper sheet (LPE) with a working electrode (WE) composed of a carbon substrate modified with carbon nanofibers arranged on a support electrode platform (PE) and its voltamperogram is shown by a dashed line. A second electrochemical device is composed of an electrodic paper sheet (LPE) with a working electrode (WE) composed only of a carbon substrate arranged 25 on an electrodic support platform (PE) and its voltamperogram is shown by a continuous line. The third electrochemical device is composed of a sheet of electrodic paper (LPE) with a working electrode (WE) composed of a carbon substrate modified with carbon nanofibers and gold nanoparticles arranged on a support electrode platform (PE) and its voltamperogram It is shown by a dotted line.

EXPLANATION OF A PREFERRED EMBODIMENT

For a better understanding of the present invention, the following examples of preferred embodiment are described, described in detail, which should be understood without limiting the scope of the invention.

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Example 1: Manufacture and electrochemical evaluation of the electrochemical device.

This example illustrates the methodology used for the manufacture of the electrochemical device object of the invention and its electrochemical evaluation with a model system. The manufacturing methodology consisted of the following stages:

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a) Printing with wax on a sheet of paper (HP) of closed geometric shapes (FG) in the form of rings with an internal diameter of 5 mm and an external diameter of 9 mm (Fig. 1).

b) Diffusion of the wax by heating at 110 ° C for 2 minutes on a heating plate. After this process, the closed geometric shapes (FG) in the form of rings resulting from wax had 4 mm of internal diameter and 10 mm of external diameter (Fig. 2).

c) Addition by means of an automatic dispenser of 2 pL of a liquid suspension of 23% carbon paste in dimethylformamide on the inside of the area delimited by the closed geometric forms (FG) printed in the form of rings. The wax prevents the complete diffusion of the suspension resulting in circles of carbon paste of 4 mm in diameter (Fig. 2A).

d) Curing of the carbon paste and evaporation of the solvents, placing the sheet of paper (HP) in an oven at 70 ° C for 30 minutes or at 37 ° C for 24 hours.

e) Addition of adhesive spray to the sheet of paper (HP) after protecting the working electrodes (WE) with several plastics of 4 mm in diameter. In this way, the adhesive covers the sheet of paper except the protected areas, which are the work electrodes (WE). Then, the protective plastics were removed.

f) Cut the paper sheet around the precisely printed rings using a 5 mm circular cutting tool to obtain several

electrodic paper sheets (LPE) with a working electrode (WE). The cutting tool can be a simple punch for paper or for harder materials.

5 Then an electrodic paper sheet (LPE) was adhered on a platform

electrodica support (PE) so that the working electrode (WE) of the electrodica paper sheet (LPE) connects to the contact area (ZC) of the electrodica support platform (Fig. 3).

The response of the electrochemical device thus manufactured was studied using a model substance such as hexaaminrutenium. For this, the following steps were carried out:

1. Addition of 40 pL of an aqueous solution of 250 pM of hexaaminrutenium (III) chloride in 0.1 M KC1.

2. Registration of the analytical signal using cyclic voltamperometna by means of

15 application of a potential sweep from 0.1 V to -0.5 V with a

variable scan speed (50, 100, 250 mV / s).

Fig. 4 shows the cyclic voltamperograms of Ru (NH3) 6Cl3 obtained in the device object of the invention under the experimental conditions indicated in the example. As can be seen by the voltamperograms at different scanning rates 20 obtained, the electrochemical process of reduction and subsequent reoxidation of the species [Ru (NH3) 6] 3+ exhibits a good electrochemical behavior in the device object of the invention. The speed of the electronic transfer in the electrochemical device developed is high as indicated by a potential difference of the anodic and cathode peaks of 61 mV, very close to the theoretical value of reversibility (59 mV). This fact indicates that the developed device works perfectly for a model system and even the speed of electronic transfer is greater in the new device compared to the use of a commercial ceramic screen-printed electrode (potential difference of 74 mV). So, in addition to the advantages of being able to reuse this electrodic support platform (PE) with different 30 sheets of electrodic paper (LPE), the improvement in electrochemical behavior

An analyte is a great advantage in the development of electrochemical sensors and biosensors using the device object of the invention.

Example 2: Modification of the working electrode (WE) of an electrodic paper sheet (LPE) with metal nanoparticles.

5 This example illustrates the methodology used for the modification of the electrode of

work (WE) of the electrodic paper sheet (LPE) described in example 1 with metal nanoparticles by electrodeposition that allows the manufacture of a disposable electrodic paper sheet (LPE) whose working electrode (WE) is nanostructured with metal particles . The methodology consisted of the following 10 stages:

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g) Placement of the electrodic paper sheet (LPE) on the support electrode platform (PE).

h) Addition of 40 pL of an aqueous solution of a metal salt in adequate concentration (between 0.1 and 5 mM) covering the electrodic paper sheet (LPE) and the reference electrode (RE) and auxiliary (AE) of the electrode platform support (PE). For example, the metal salt can be AgNC> 3 or HAuCU to generate silver or gold nanoparticles, respectively.

i) Application of a negative current (typically between -10 and -100 pA) to the device for the reduction of the metal cation and generation of nanoparticles on the surface of the working electrode (WE) of the electro-paper sheet (LPE). The application of the current is carried out for a certain time (typically between 60 and 300s).

j) Application of a potential of 0.1 V for 120 s for the desorption of the possible hydrogen generated in the previous stage.

k) Washing with H2O and drying at room temperature.

The response of the electrochemical device thus manufactured was studied using a model substance such as dopamine. For this, the following steps were carried out:

1. Addition of 40 pL of an aqueous solution of 250 pM dopamine in 0.1 M KC1.

2. Registration of the analytical signal using cyclic voltammetry by applying a suitable potential sweep with a scanning speed

5 of 50 mV / s.

The results obtained for the cyclic voltammetry of the dopamine both in the device where the working electrode (WE) of the electrode paper sheet (LPE) is only composed of carbon paste (Fig. 5, continuous line) and in the device where the working electrode (WE) of the sheet of 10 electrode paper (LPE) is further modified with electrodeposited gold nanoparticles (Fig. 5, dotted line) by applying a current of -100 pA for 180 s at a solution of 1 mM of HAuCL * in 0.2 M HC1, are shown in Fig. 5. A better electrochemical behavior can be observed in the device with the electrodic paper sheet (LPE) whose working electrode 15 (WE) is modified with nanoparticles of gold translated into a potential difference between the cathode peak and the smallest anodic peak and a greater intensity of both peaks compared to the device with the electrodic paper sheet (LPE) whose work electrode or (WE) is unstructured. A potential difference is obtained for the device with the electrodic paper sheet 20 (LPE) whose working electrode (WE) is without nanostructuring of 560 mV and for the device with the electrode paper sheet (LPE) whose working electrode (WE) is nanostructured of 70 mV, representing a great improvement in the speed of electronic transfer. This is how the modification of the working electrode (WE) of the electrodic paper sheet (LPE) with nanoparticles 25 is carried out in a very simple way and that produces superior results for the detection of dopamine. The porous nature of the paper and the ability to electrodeposite metal nanoparticles may allow an increase in preconcentration of analytes or recognition elements for application in electrochemical sensors and biosensors, in addition to that electrochemical improvement in detection. The electrodic paper sheet (LPE) is removed after the measurement is carried out, and after the H2O washing of the support electrodic platform (PE) it is ready to perform a new test after adhering a new paper sheet

electrodica (LPE). The example explained for gold nanoparticles is possible with another type of metal nanoparticles, which can be electrodeposited or adsorbed on the working electrode (WE) of the electrode paper sheet (LPE).

5 Example 3: Modification of the working electrode (WE) of the electrodic paper sheet (LPE) with carbon nanofibers.

This example illustrates the methodology used for the modification of the working electrode (WE) of the electrodic paper sheet (LPE) described in example 1 with carbon nanomaterials, such as nanofibers. In this way an electrochemical device is obtained with a disposable electrode paper sheet (LPE) whose working electrode (WE) is nanostructured by adsorption of the nanomaterial on its surface. In this case, there are two possibilities of modification that could be useful in different applications. On the one hand, the electrodic paper sheet (LPE) can be manufactured with the working electrode (WE) according to

15 was explained in the previous sections, and proceed to modify the front of the sheet

of paper electrodica (LPE) in the inner zone delimited by the ring with the nanomaterial of interest, getting the adsorption of the nanomaterial on the working electrode (WE) of the sheet of electrodica paper (LPE). On the other hand, it is possible to modify the reverse in the inner zone delimited by the ring with the nanomaterial of interest and subsequently carry out the modification with the carbon paste that would come into contact with the nanomaterial to generate the electrodic surface. Next, the methodology of the first case is detailed, which consisted of the following stages:

The electrodic paper sheet (LPE) was manufactured with a working electrode

25 (WE) carbon substrate compound as explained in example 1. After that

proceeded to perform the following stages:

fl) Addition of 2 pL by means of an automatic dispenser of a liquid dispersion of the nanomaterial in adequate concentration (between 0.1 and 1 mg / mL) on the area opposite the carbon substrate of the electrode paper sheet (LPE) and 30 within the inner zone delimited by the wax ring.

5

10

fifteen

twenty

25

30

f.2) Drying at a suitable temperature (70 ° C or ambient T, depending on the solvent used) for 40 minutes for total evaporation of the solvent.

The response of the electrochemical device manufactured with such an electro-paper sheet (LPE) whose working electrode (WE) was nanostructured was studied using a model substance such as dopamine. For this, the following steps were carried out:

1. Placement of the electrodic paper sheet (LPE) on the support electrode platform (PE).

2. Addition of 40 pL of an aqueous solution of 100 pM dopamine in 0.1 M H2SO4.

3. Registration of the analytical signal using cyclic voltammetry by applying a potential sweep from 0 V to 0.5 V with a scanning speed of 50 mV / s.

Fig. 6 shows the dclic voltammeters obtained for dopamine in the device with the electrodic paper sheet (LPE) whose working electrode (WE) is unmodified (only consists of the carbon substrate) (continuous line) and the device with the electro-paper sheet (LPE) whose working electrode (WE) was modified with 1 mg / mL of carbon nanofibers (in aqueous solution) and dried at room T (dashed line). In the case of the device with the electrode paper sheet (LPE) with unmodified working electrode (WE), a quasi-reversible process is obtained with a peak potential difference of 244 mV and an anodic and cathode peak intensity of 1.17 and - 0.91 pA, respectively, while for the device with the electrodic paper sheet (LPE) whose working electrode (WE) is nanostructured a more reversible process is obtained with a peak potential difference of 92 mV and intensities of 1.65 and - 1.59 pA for the anodic and cathode peak, respectively. Therefore, it can be seen how the nanostructuring of the working electrode (WE) of the electroplating paper sheet (LPE) with carbon nanofibers improves the behavior of the electronic transfer process of dopamine. The paper, due to its porous nature, allows to generate a high adsorption capacity of these nanomaterials by increasing the electrode surface area, as observed in the increase in peak intensities. Similar results can be obtained by modifying the electrode

Working (WE) of the electrodic paper sheet (LPE) with other nanomaterials such as graphene or carbon nanotubes.

The sheet of electrodic paper (LPE) is discarded after the measurement has been carried out, and after washing with H2O of the electrodic support platform (PE) it is arranged to perform a new test. This is a clear advantage since, in general, nanostructured electrochemical sensors with carbon nanomaterials have a high adsorption capacity of different substances irreversibly and should normally be discarded. The possibility of discarding only the working electrode, instead of the entire electrode platform, is a great advantage of these devices for this type of applications.

On the other hand, there is the possibility of performing a hybrid modification by carrying out example 3 and then following example 2. In this way, a disposable electrode paper sheet (LPE) would be obtained whose working electrode (WE) is modified with nanofibers. of carbon and gold nanoparticles. As can be seen in Fig. 6 (dotted line), the cyclic voltamperogram obtained for the electrochemical device with the electrode paper sheet (LPE) thus modified exhibits a better electrochemical behavior, with a smaller potential difference (35 mV ) and greater intensity of the anodic and cathode peaks (2.5 and -2.2 | iA, respectively) compared to the use of the device with the electrodic paper sheet 20 (LPE) whose working electrode (WE) is unmodified or modified with the separate nanomaterials, indicating a higher electronic transfer rate and an electroactive area.

Claims (23)

5 10 fifteen twenty 25 1. Electrochemical device for the analysis of the chemical composition of samples comprising a working electrode (WE), a reference electrode (RE), an auxiliary electrode (AE) and connection means (CN) with a system of power and data recording characterized by The working electrode (WE) is comprised of an electrodic paper sheet (LPE), and is an area with a carbon substrate, which is limited by a closed geometric shape (FG) of wax printed on one side and diffused to the opposite side of the sheet of electrodic paper (LPE) forming a closed geometric shape on both sides, because the reference electrode (RE), the auxiliary electrode (AE) and the connection means (CN) with a feeding system and The data record is included in a support electrode platform (PE) that has a contact area (ZC) and because the electro paper sheet (LPE) is temporarily adhered to the support electrode platform (PE) so that the electrode Work (WE) is arranged on the surface of the contact area (ZC) of the electrodic support platform (PE) maintaining contact between both surfaces. 2. Device according to claim 1 characterized in that the closed geometric shape (FG) is a ring. 3. Device according to claim 2 characterized in that the ring has an inner diameter of between 1 and 10 mm. 4. Device according to claim 1 characterized in that the carbon substrate of the working electrode (WE) of the electrodic paper sheet (LPE) is a graphite composition. 5. Device according to claim 1 characterized in that the carbon substrate of the working electrode (WE) of the electrodic paper sheet (LPE) is a composition of carbon nanomaterials. 5 10 fifteen twenty 25 6. Device according to claim 1 characterized in that the sheet of electrodic paper (LPE) also comprises metal nanoparticles arranged therein by electrodeposition or adsorption. 7. Device according to claim 6 characterized in that the metal nanoparticles are silver, gold, nickel, platinum, palladium or bismuth. 8. Device according to claim 1 characterized in that the electrodic paper sheet (LPE) also comprises carbon nanomaterials arranged by electrodeposition or adsorption. 9. Device according to claims 5 or 8, characterized in that the carbon nanomaterials are graphene, nanofibers or carbon nanotubes. 10. Device according to claim 1 characterized in that the sheet of electrodic paper (LPE) is temporarily adhered to the support electrodic platform (PE) by means of a pressure sensitive adhesive (PSA) disposed on the sheet of electrodic paper (LPE). 11. Method for manufacturing one or more sheets of electrode paper (LPE) of the electrochemical device of claim 1 comprising the following steps: a) print one or more closed geometric shapes (FG) with wax on a sheet of paper (HP); b) diffuse the closed geometric shape (FG) to the opposite side of the paper sheet (HP) by heating the paper sheet (HP) printed in step a) at a diffusion temperature until diffusion occurs; c) add a liquid suspension of carbon paste in the internal area delimited by the closed geometric shape (FG); d) heat the sheet of paper (HP) with the closed geometric form (FG) and the liquid suspension to at least the evaporation temperature of the solvents of the liquid suspension, leaving a 10 fifteen twenty carbon substrate inside each closed geometric shape (FG) forming a working electrode (WE); e) cover each working electrode (WE) with a protective layer, apply an adhesive to the rest of the surface of the paper sheet (HP) and remove said protective layer; f) cut the sheet of paper (HP) precisely around the closed geometric shape (FG) to obtain one or more sheets of electrodic paper (LPE); g) adhering the electrodic paper sheet (LPE) to an electrodic support platform (PE) so that the working electrode (WE) of the electrodic paper sheet (LPE) is disposed on the surface of the contact area (ZC ) of the electrodic support platform (PE) maintaining the contact between both surfaces; h) add a solution with a metal salt covering the electrodic paper sheet (LPE) and the reference (RE) and auxiliary (AE) electrodes of the support electrode platform (PE); i) apply a current for salt reduction and electrodeposite metal nanoparticles on the working electrode (WE) of the electrodic paper sheet (LPE); j) apply a potential for hydrogen desorption; k) wash the assembly. 12. Method according to claim 11 characterized in that the closed geometry (FG) is a ring. 13. Method according to claim 12 characterized in that the ring has an inner diameter of between 1 and 10 mm. 14. Method according to claim 11 characterized in that the diffusion temperature of stage b) is between 100 ° C and 150 ° C and the diffusion time is between 50 and 120 seconds. 15. Method according to revindication 11 characterized in that carbon paste is a graphite composition. 16. Method according to revindication 11 characterized in that the carbon paste is a composition of carbon nanomaterials. 5 17. Method according to revindication 11, 15 or 16 characterized in that the Liquid suspension of carbon paste from step c) is 2 pL of a 23% carbon solution in dimethylformamide. 18. Method according to revindication 11 characterized in that the evaporation temperature of the solvents is between 20 and 100 ° C and the evaporation time 10 is between 15 minutes and 24 hours 19. Method according to revindication 11 characterized in that the adhesive applied in step e) is pressure sensitive (PSA). 20. Method according to revindication 11 characterized in that the solution of step h) is an aqueous solution and the salt is a metal salt of silver, gold, nickel, 15 platinum, palladium or bismuth in a concentration between 0.1 and 5 mM, 21. Method according to claim 11 characterized in that the current of step i) is between -10 and -300 pA for 15 and 300 seconds. 22. Method according to revindication 11 characterized in that the potential of stage j) is between 0 and 0.5 V for 30 and 120 seconds. 20 23. Method according to revindication 11 characterized in that it also includes the following stages, between stage f) and g): f.l) add a liquid suspension of carbon nanomaterials on the opposite side to the working electrodes (WE) of the electrodic paper sheet (LPE); 25 f.2) evaporate the solvent from the liquid suspension. 24. Method according to revindication 11 characterized in that it also comprises the following stages, between stage b) and c): b.l) add a liquid suspension of carbon nanomaterials within the area limited by the closed geometric shape (FG); b.2) heat the sheet of paper (HP) with the closed shape or geometric shapes (FG) and the liquid suspension of nanomaterials up to at least the evaporation temperature of the solvents of the liquid suspension, leaving a substrate of carbon nanomaterials within the area delimited by the closed geometric shape (FG). 25. Method according to claims 16, 23 or 24 characterized in that the 10 carbon nanomaterials are graphene, nanofibers or carbon nanotubes.