WO2021102593A1

WO2021102593A1 - System and method for determining and quantifying the concentration of an analyte, which comprises an optically active diamond-based sensor, a chamber accommodating the sensor, and means for inserting a sample; and use of said sensor

Info

Publication number: WO2021102593A1
Application number: PCT/CL2019/050124
Authority: WO
Inventors: Enrique Javier MUÑOZ TAVERA; Ivan Alonso GONZALEZ PAVEZ; Jerónimo MAZE RIOS; Hossein TAVAKOLI DINANI; Vicente Andres SANTIBAÑEZ CISTERNAS; Raul Manuel GONZÁLEZ BROUWER
Original assignee: Pontificia Universidad Catolica De Chile
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2021-06-03

Abstract

The present invention relates to a system for determining and quantifying the concentration of an analyte in a sample, which comprises: a diamond-based sensor containing optically active colour centres close to the surface; a chamber or cell accommodating the diamond; and means for inserting the sample into the system. The invention also relates to a method for measuring an analyte in a sample containing same, which is carried out in the developed system; and to the use of the sensor.

Description

SYSTEM AND METHOD FOR THE DETERMINATION AND QUANTIFICATION OF THE CONCENTRATION OF AN ANALYTE THAT INCLUDES AN OPTICALLY ACTIVE DIAMOND-BASED SENSOR, A CAMERA HOUSING SAID SENSOR AND MEANS TO ENTER THE SAMPLE; AND USE OF SUCH SENSOR

DESCRIPTIVE MEMORY FIELD OF THE INVENTION

The present invention relates to a system and method for determining and quantifying an analyte, wherein the measurement system comprises a diamond-based sensor having optically active color centers. Likewise, it refers to the use of said diamond-based sensor for the detection and quantification of an analyte that may correspond to an element, ion and / or chemical compound.

BACKGROUND OF THE INVENTION

Highly sensitive chemical sensors that are capable of operating in extreme conditions and that also have the potential to be miniaturized are in high demand in the chemical, mining and gas extraction industries, where the high sensitivity of the sensors is crucial to detect small amounts of chemical elements that could alter the course of industrial processes or toxins that can be harmful to the environment or health. The ability to miniaturize a sensor and work in conditions of high pressure, temperature or corrosive environments is highly desirable to access remote locations, mainly in industries that deal with the extraction of minerals, oil and gas, among others.

The present invention aims to solve this need through the development of a detection method that is based on recent scientific discoveries that show the ability of diamond to detect fluctuations in the electric field. This method is highly sensitive since it is based on the monitoring of coherent properties of molecules inside the diamond that are in turn affected by fluctuations in the electric field produced by chemical reactions. On the other hand, being made of diamond, the sensor presents noble characteristics, such as high resistance to high pressures, high temperatures and chemical resistance to corrosive environments, which makes it ideal for working in a wide range of environmental conditions.

Nanodiamonds

Nanodiamonds, like diamonds, are made up of carbon atoms located in a crystal lattice. Nanodiamonds sometimes have impurities on their surface. This modification in the surface structure produces changes in the optical properties (absorption and emission of radiation).

Nanodiamonds with color centers or optically active molecules can detect the presence of reactants in a chemical reaction by measuring the electronic noise they generate. The color centers are associated with an electronic spin whose dynamics at a very low magnetic field is affected exclusively by fluctuations in the electric field and which can be optically observed through the fluorescence associated with these color centers.

In particular, Nitrogen-Vacancy centers (NV centers) are point defects in diamonds composed of an impurity atom (nitrogen) and a vacancy in the carbon crystal lattice that is characteristic of diamonds. These defects are fluorescent, that is, they emit light at a very particular wavelength.

The inventors have generated stable NV centers at shallow depth (1-10 nm) below the diamond surface by the nitrogen ion beam implantation technique. These centers are sensitive to fields external to the diamond, and in turn, they are stable enough to be used as sensors.

DESCRIPTION OF PRIOR ART There is literature regarding diamond-based sensors with NV centers, and their possible applications.

Patent application WO2018155504 discloses a diamond magnetic sensor comprising a diamond having at least one nitrogen vacancy center (NV) close to the diamond surface, a microwave generator that irradiates the diamond with microwaves, a light generator of excitation that irradiates the NV center in the diamond with excitation light, and a fluorescence detector that receives fluorescent light generated by the NV center in the diamond. The diamond magnetic sensor further comprises a pattern measurement device, which measures the patterns of time variation in the intensity of the magnetic field from changes in fluorescence intensity detected by the fluorescence detector.

The doctoral thesis entitled “Fluorescent nanodiamonds as a sensor and life Science probe” (Torsten Rendler, 2018, University of Stuttgart) discloses the development of a new modular hybrid sensor platform, using NV to measure the concentration of chemicals. TI relaxometry is applied to gadolinium, Gd (III) detection complexes close to NV. The breakdown of the Gd (III) complexes is activated by changes in pH or by the presence of some reducing agent. The resulting change in TI is used as a measure to determine these amounts. It is indicated that the fluorescence signal from specific sensors can be used to encode information about the local environment, demonstrating sensitivity to viscosity, pH, temperature, or individual chemical compounds. As these sensors are typically on the order of a few nanometers, highly localized monitoring of a desired quantity is possible. Following this approach, it is indicated that a large number of molecular size systems have been developed using different types of strategies: for example, by monitoring changes in fluorescence lifetime, photoluminescence (PL) spectra or the global intensity of emissions. It is indicated that therefore it is a great challenge to design a sensor that selectively responds to a desired quantity and that, like organic sensors, does not degrade over time.

In addition to organic and inorganic sensors, the detection of nanoscale diamond color centers containing nitrogen-vacancy (NV) centers has also been established.

Notwithstanding the foregoing, methods and / or systems for the determination of a specific analyte have not yet been described in the prior art, but it is mainly disclosed that diamond-based sensors have a very promising future in terms of sensitivity and selectivity.

Therefore, there is a strong need to develop systems and methods that include this type of sensors that allow the quantification of analytes that are of importance in industrial applications.

SUMMARY OF THE INVENTION

The present invention relates to a system and method for determining and quantifying an analyte (chemical compound, element or ion). This system comprises a cell containing a diamond-based sensor that has optically active color centers close to the surface at a distance between 2-8 nanometers.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Confocal image of one of the NV implantation areas in the diamond. Figure 2: Photographs of the camera that houses the diamond sensor. Figure 3: Scheme of the system according to the present invention. Figure 4: Scheme of the steps of the measurement method according to the present invention. Figure 5: Illustration of the Flow Chamber housing the diamond-based sensor and sensor image.

Figure 6: Photograph of one embodiment of the system according to the present invention. Figure 7: Photograph of an embodiment of the system according to the present invention. Figure 8: Fluorescence signals associated with different magnetic resonances in the presence of magnetic fields.

Figure 9: Graph of the calibration curve obtained for the determination of copper.

Figure 10: Graph of the sample reading on the calibration curve.

DETAILED DESCRIPTION OF THE INVENTION Diamond based sensor with Nitrogen-Vacuum centers

Diamond with color centers close to the surface is prepared using the nitrogen ion beam implantation technique. This implantation consists of accelerating nitrogen ions (isotope 15) with energies between 0.7 keV and 10 keV and doses between 10 and 10 ions per square centimeter, the latter allowing to control the number of color centers generated. The NV centers generated are stable and lie at a depth between 1 and 10 nm relative to the diamond surface.

These centers are sensitive to fields external to the diamond, and in turn, stable enough to be used as sensors.

Electronic magnetic resonance imaging tests were performed at weak fields to verify the presence of optically active defects due to implantation. Figure 1 shows the image taken by confocal microscopy of one of the implantation areas.

The energies used between 0.7 keV and 10 keV produced color centers between 10 nm and 1 nm in depth with respect to the diamond surface. The dose (number of ions per square centimeter implanted) was also varied to control the number of color centers.

The optical properties of the sensor are obtained by Ramsey resonance spectroscopy, which is similar to that used in clinical resonators, but in this case it is applied on the electronic spins of the diamond and not on the nuclear spins. For this purpose, the experimental setup has a microwave generator with frequencies around 3 gigahertz and with a bandwidth of about 500 megahertz, to achieve resonance between the electronic spins and the microwave radiation. The sample, composed of electrical charges with Random movements, causes an electrical noise that is proportional to the concentration of charges in the solution that is detectable by the color centers.

The sensitivity of the sensor is controlled by a coil that generates an external magnetic field. The sensor reaches its maximum sensitivity when the coil and power supply system cancels the magnetic field produced by the earth. Since this field (magnitude and direction) depends on the place where the measurement is taken. Calibration must be done during sensor power-up.

Microfluidic Chamber and Circuit

A microfluidic system was designed and developed that allows the entry of a solution to be measured and the application of microwave radiation to carry out the measurement protocol. In turn, this microfluidic system aims to keep the flow constant. This system uses 50 mL motorized syringes. The flow can be varied between 0 and 50 mL / s.

The system consists of two inlets for the solution and one outlet that allows connection to the diamond-based sensor. The chamber has a space that allows solutions to enter and mix, which in turn allows an electrode to be placed for pH detection for sensor calibration purposes.

Pieces of material resistant enough to prevent corrosion caused by the solutions that are added and the temperature differences that can be reached were designed and manufactured (see Figure 2). The material used corresponds to a low fluorescence plastic material (Permanox®).

Additionally, a control software was developed in order to measure and manipulate different variables such as pH, internal diameter of an injection system based on motorized syringes (int. Diameter), added volume (volume), addition speed ( rate), among others.

Analyte measurement method The sample to be analyzed that comprises the analyte to be determined must be previously diluted depending on its initial concentration. Then a syringe is entered which is activated by the flow controller that allows the sample to circulate through the Flow Chamber where the diamond is found, as shown in Figure 3. The sample, when interacting with the diamond, changes its properties. optics that are measured by laser excitation and the recording of luminosity by means of a Fluorescence Detector. These optical properties are compared to a calibration curve that has been previously obtained. This comparison allows to know the concentration of the element to be measured in the sample.

The measurement of the analyte (chemical compound, element or ion) present in a sample is carried out through the following steps:

I. Sensor calibration

The diamond-based chemical reaction sensor consists of the reading of electronic noise that is associated with the presence of electrical charges present in a solution. To use the sensor, it must be calibrated for each analyte to be studied.

This first stage consists of determining the magnetic field associated with the longest coherence time of the optically active diamond. The longest coherence time occurs when the applied magnetic field cancels the earth's magnetic field present in the place where the measurement is made, because the optically active diamond has an anisotropic response to the magnetic field. The value of this magnetic field must be obtained each time the Flow Chamber (and therefore the diamond) is used or moved.

II. Sample calibration

This stage consists of calibrating the sensor with respect to a specific sample. For this, three measurements of the coherence time and / or Rabi frequency are taken: the first measurement is carried out in the presence of a solution at neutral pH (deionized water); the second and third measurements of the coherence time and / or frequency of Rabi are carried out with known standard samples with two different concentrations to associate each C1 and C2 concentration to the TI and T2 coherence times. In this way, a linear calibration curve is obtained that will be used in the next stage.

III. Specific sample measurement

This stage consists of measuring the coherence time and / or frequency of Rabí with a solution containing the analyte to be quantified. This time and / or frequency is interpolated to the calibration curve and then the value of the analyte concentration in the solution is determined.

Stages I, II and III are summarized in the scheme of Figure 4.

System for the determination of the analyte

The system by which the above-described method can be carried out comprises a cell containing the described diamond-based sensor, in addition to a microwave generator to achieve resonance between the electronic spins and the microwave radiation. The sample, composed of charged species with random Brownian motion, causes a magnetic noise that is proportional to the concentration of these charges in the solution.

Figure 5 shows the Flow Chamber where the diamond that has been implanted with nitrogen atoms to make it optically active is housed. The image shows a zone of implantation of 5 keV of energy that has been obtained by means of a confocal microscope. The implantation size is only 25 Dm in diameter.

Figure 6 shows the objective lens and the flow chamber connected to a syringe containing the fluid to be analyzed.

Figure 7 shows the most relevant parts of the system according to the present invention: the excitation with a green laser of 532 nm and 1 Watt of power and the fluorescence detector capable of detecting individual photons. The counts of this detector reach several million photons detected per second.

PREFERRED MODALITIES OF THE INVENTION The present invention is directed to a system for the determination and quantification of the concentration of an analyte in a sample that contains it, comprising:

• a diamond sensor containing optically active color centers close to the surface; · A chamber or cell that houses said sensor; Y

• means of getting the sample into the system.

Wherein the optically active color centers correspond to nitrogen ion implantations.

In one embodiment of the invention, the color centers are produced by the nitrogen ion beam implantation technique which consists of accelerating nitrogen ions with energies between 0.7 and 10 KeV.

In a preferred embodiment of the invention the implants have a depth between 10 nm and 1 nm.

In a more preferred embodiment of the invention the implantations are carried out at doses between 10 ⁹ and 10 ¹² ions / cm ² .

In another embodiment of the invention, the means that allow the entry and exit of the sample correspond to a microfluidic circuit that allows working with a minimum amount of sample.

In a preferred embodiment of the invention, the chamber has a space that allows the solutions to enter and mix. The chamber allows an electrode to be placed for pH detection for sensor calibration purposes. Even more preferably, the chamber further allows to place an electrode for pH detection for sensor calibration purposes.

In one embodiment of the invention, the chamber and means are made of a corrosion resistant material. The present invention is also directed to a method for the determination and quantification of the concentration of an analyte present in a sample that contains it, which is carried out in the system described above, which comprises the following steps:

I. calibrating the sensor by determining the electric field noise associated with the coherence time and / or Rabbi frequency of the optically active diamond sensor;

II. calibrating the specific sample to be measured by determining at least three measures of coherence time and / or Rabbi frequency; Y

III. Measurement of the sample by determining the coherence time and / or Rabí frequency of the sample with the analyte to be quantified.

In one embodiment of the invention, in stage II the first measurement is carried out in the presence of a solution at neutral pH. Where optionally, the neutral pH solution is water.

In another embodiment of the invention, in stage II at least two remaining measurements are carried out with calibration standards of known concentration of the analyte to be determined in stage III, at which the coherence time and / or frequency of Rabí are measured. and the respective concentration is associated to them to obtain a calibration curve. Wherein in stage III the coherence time and / or Rabí frequency of the sample is measured, which is interpolated in the calibration curve and the sample concentration is obtained.

Where because the analyte corresponds to an element, ion and / or chemical compound.

Finally, the present invention refers to the use of the sensor described above for the determination and quantification of the concentration of an analyte by means of the fluorescence of a diamond with optically active color centers. Where the analyte to be measured is selected from metals, pesticides, pH, fuels, pollutants, among others.

EXAMPLE OF APPLICATION

By means of the method and system of the present invention, the concentration of copper present in a sample was determined. I. Sensor calibration

First, an optically active zone was selected that has been produced with an implantation energy of 5 keV and a dose of 10 ¹⁴ ions per square centimeter. This generated in the confocal setup illustrated in Figure 5 a fluorescence intensity of approximately 4 million counts per second.

To observe the coherence time, Ramsey spectroscopy was performed as a function of the applied magnetic field with a current generator that takes the values -10 and 0 mA. To observe the frequency of Rabi, a Rabi spectroscopy was performed as a function of the temporal width of the microwave disturbance.

Figure 8 shows the fluorescence signals associated with 7 magnetic resonances in the presence of magnetic fields generated by a coil system. Each curve is associated with the current of a current source used to power the coil system. As can be seen, the maximum sensitivity was obtained for -8 mA, which is where the maximum coherence time is observed. Therefore, to obtain the maximum sensitivity of the sensor, it is necessary to operate at this current in the power source.

II. Sample calibration

A calibration curve was generated that measures the optical properties of the sensor for two known concentrations of copper. Specifically, the optical properties of the sensor are obtained by Ramsey resonance spectroscopy applied on the electronic spins of the diamond.

Two samples of known concentrations corresponding to 1 mg / L and 100 mg / L were prepared from a standard copper solution. These values define the range must be chosen in such a way that the measured values of the sample to be determined are within the range defined by both points. These concentrations constitute the standard samples to calibrate the sensor. The average of duplicate readings of the Rabi frequencies in MHz obtained are shown in Table 1.

Table 1

Figure 9 shows a calibration curve obtained.

III. Specific sample measurement

A control sample of copper was prepared with a concentration of 50 mg / L, which is within the prepared calibration curve, and the Rabi frequency was measured in duplicate.

The sensor gave a value of 13.81 MHz, which when interpolated in the calibration curve resulted in a copper concentration value of 48.96 mg / L, so the error with respect to the theoretical value was 2.1 % (Figure 10).

CONCLUSIONS

The developed system, and in particular the chemical sensor, allow the determination and quantification of the concentration of reactants by means of the fluorescence of a diamond. The sensor allows monitoring the concentration of analytes (elements, ions or chemical compounds) by measuring the fluctuations in the electric field that these generate.

Given the versatility of the proposed system that comprises the developed sensor, it allows its use in a multiplicity of industries. For example, in chemical measurements under extreme conditions, the sensor can be used in optimizing the extraction of fuels such as gas and oil. In environmental monitoring, it will be useful in detecting heavy metals such as arsenic, lead and cadmium in lakes, seas and rivers and where conditions of high temperatures and pressures are present. In the optimization of industrial chemical processes as part of the control of the kinetics of industrial chemical reactors and in the certification of food as pesticide concentration sensor. In summary, the developed system allows to generate measurements with greater accuracy and precision in the study of chemical reactions on a nano-metric scale in different environments such as: surface reactions, industrial catalysis, biocatalysis (food), pharmaceuticals and analytical chemistry. In the field of mining, the system and method of the present invention will make it possible to positively impact the increase in copper grade in concentrates and the recovery of elements of interest such as valuable metals (Cu, Mo, Re, U, Ge) , and in the control of impurities.

The foregoing specification is considered solely illustrative of the principles of the invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the preceding section, but should be given the broadest interpretation consistent with the specification as a whole.

Claims

1. System for the determination and quantification of the concentration of an analyte present in a sample that contains it, CHARACTERIZED because it comprises:

• a diamond-based sensor containing optically active color centers close to the surface;

• a chamber or cell that houses said sensor; Y

• means of getting the sample into the system.

2. The system according to claim 1, CHARACTERIZED in that the optically active color centers correspond to nitrogen ion implantations.

3. The system according to claim 2, CHARACTERIZED in that the color centers are produced by the nitrogen ion beam implantation technique that consists of accelerating nitrogen ions with energies between 0.7 and 10 KeV.

4. The system according to claim 2, CHARACTERIZED in that the implants have a depth between 10 nm and 1 nm.

5. The system according to claim 3, CHARACTERIZED in that the implantations are carried out at doses between 109 and 1012 ions / cm 2.

6. The system according to claim 1, CHARACTERIZED in that the means that allow the entry and exit of the sample corresponds to a microfluidic circuit that allows working with a minimum amount of sample.

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7. The system according to claim 1, CHARACTERIZED in that it consists of at least two inlets for the solution and at least one outlet that allows connection with the diamond-based sensor.

8. The system according to claim 1, CHARACTERIZED in that the chamber has a space that allows the entry and mixing of solutions.

9. The system according to claim 1, CHARACTERIZED in that the chamber allows an electrode to be placed for pH detection for sensor calibration purposes.

10. The system according to claim 1, CHARACTERIZED in that the chamber and the means are made of a material resistant to corrosion.

11. Method for determining and quantifying the concentration of an analyte present in a sample that contains it, which is carried out in the system according to claim 1, CHARACTERIZED because it comprises the following steps:

I. calibrate the diamond-based sensor, which contains optically active color centers close to the surface, by determining the electric field noise associated with the coherence time and / or Rabí frequency of said sensor;

12. The method according to claim 11, CHARACTERIZED in that in stage II the first measurement is carried out in the presence of a solution at neutral pH.

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13. The method according to claim 12, CHARACTERIZED in that the solution at neutral pH is water.

14. The method according to claim 11, CHARACTERIZED because in stage II at least two remaining measurements are performed with calibration standards of known concentration of the analyte to be determined in stage III, at which the coherence time is measured. and / or Rabí frequency and the respective concentration is associated with them to obtain a calibration curve.

15. The method according to claim 11, CHARACTERIZED in that in stage III the coherence time and / or Rabí frequency of the sample is measured, which is interpolated in the calibration curve and the sample concentration is obtained.

16. The method according to claim 11, CHARACTERIZED in that the analyte corresponds to an element, ion and / or chemical compound.

17. Use of a chemical sensor based on diamond, CHARACTERIZED because it serves for the determination and quantification of the concentration of an analyte through the fluorescence of a diamond with optically active color centers.

18. The use according to claim 17, CHARACTERIZED in that the analyte to be measured is selected from metals, pesticides, pH, fuels, pollutants, among others.

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