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WO-2026096568-A1 - MXENE-BASED ELECTROCHEMICAL PHOSPHATE SENSORS

WO2026096568A1WO 2026096568 A1WO2026096568 A1WO 2026096568A1WO-2026096568-A1

Abstract

Rapid and accurate detection of molecular species with a high degree of selectivity and sensitivity constitutes the ultimate goal of designing sensors for various applications, from studying nutrients in soil-water systems to assessing physiological conditions in human health. For the first time, MXene systems, such as atomically thin two-dimensional Ti 3 C 2 T x layered materials, can be used for electrochemical detection of phosphates, one of the key molecules for sustainability of life on earth, and one of the major contributors to environmental pollution. The MXene sensors are highly selective towards phosphates.

Inventors

  • NAGARAJA, Thiba
  • DAS, SUPREM R.
  • Thakur, Anupma
  • ANASORI, Babak

Assignees

  • KANSAS STATE UNIVERSITY RESEARCH FOUNDATION
  • PURDUE RESEARCH FOUNDATION

Dates

Publication Date
20260507
Application Date
20251029
Priority Date
20241030

Claims (20)

  1. 1. A method of testing a sample for the presence of a target substance comprising: (a) dispersing the sample within a medium comprising a recognition agent that is operable to react with the target substance, wherein the target substance comprises phosphorous, a phosphorous compound, and/or a phosphate; (b) contacting the medium within which the sample is dispersed with a sensing device, the sensing device comprising an MXene electrode containing an MXene, wherein the MXene has a chemical formula of Mn i X tl T v , where “M” denotes a transition metal atom, “X” denotes either C or N, “T x ” denotes one or more surface termination groups, and “n” denotes an integer number ranging from 1 to 3; (c) inducing an electrochemical reaction between the target substance and the recognition agent; and (d) detecting a peak current signal at a characteristic applied voltage with the sensing device, the peak current signal being proportional to the concentration of the target substance within the sample.
  2. 2. The method of claim 1, wherein the target substance comprises a phosphate.
  3. 3. The method of claim 2, wherein the recognition agent comprises molybdenum.
  4. 4. The method of claim 1, wherein “T x ” denotes O, -F, -Cl, and/or -OH.
  5. 5. The method of claim 4, wherein “M” denotes Ti.
  6. 6. The method of claim 5, wherein “X” denotes a carbon.
  7. 7. The method of claim 1, wherein the chemical formula of the MXene is ThC^Tv
  8. 8. The method of claim 1, wherein the MXene is in the form of crystals having an average lateral size of 0.5 to 10 pm.
  9. 9. The method of claim 1, wherein the MXene is multilayered and comprises 1 to 10 layers.
  10. 10. The method of claim 1, wherein the medium comprises an electrolyte.
  11. 11. The method of claim 10, wherein the medium further comprises a chloride and a proton donating species.
  12. 12. The method of claim 11, wherein the proton donating species comprises sulfuric acid and the chloride comprises potassium chloride.
  13. 13. The method of claim 1, wherein the sample comprises soil or water.
  14. 14. The method of claim 1, wherein the step of detecting the peak current signal comprises performing cyclic voltammetry or differential pulse voltammetry analysis.
  15. 15. A method of testing a sample for the presence of a phosphate comprising: (a) dispersing the sample within an electrolyte medium comprising a molybdenum recognition agent that is operable to react with the phosphate and form a phosphomolybdenum complex; (b) contacting the electrolyte medium within which the sample is dispersed with a sensing device, the sensing device comprising an MXene electrode containing an MXene, wherein the MXene has a chemical formula of M n +iXnT x , where “M” denotes Ti, Sc, Mo, Zr, V, or Cr, “X” denotes either C or N, “T x ” denotes one or more surface termination groups, and “n” denotes an integer number ranging from 1 to 3 ; (c) inducing an electrochemical reaction of the phosphomolybdenum complex on a surface of the MXene electrode to thereby form a quantifiable electrochemical signal; and (d) detecting the quantifiable electrochemical signal with the sensing device, the quantifiable electrochemical signal being proportional to the concentration of the phosphate within the sample.
  16. 16. The method of claim 15, wherein the inducing occurs in the absence of an external reducing agent and a reduction catalyst.
  17. 17. The method of claim 15, wherein “T x ” denotes O, -F, -Cl, and/or -OH.
  18. 18. The method of claim 15, wherein “X” denotes a carbon.
  19. 19. The method of claim 15, wherein the chemical formula of the MXene is Ti3C2T A
  20. 20. The method of claim 15, wherein the sample comprises soil or water.

Description

MXENE-BASED ELECTROCHEMICAL PHOSPHATE SENSORS STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT [0001] This invention was made with government support under Award Nos. 1935676 and CMMI-2134607 awarded by the National Science Foundation (NSF). The government has certain rights in the invention. RELATED APPLICATIONS [0002] This application claims the priority benefit of U.S. Provisional Patent Application Serial No. 63/713,842 entitled “MXENE-BASED ELECTROCHEMICAL PHOSPHATE SENSORS,” filed October 30, 2024, the entire disclosure of which is incorporated herein by reference. BACKGROUND 1. Field of the Invention [0003] The present disclosure is generally related to MXene-based electrochemical phosphate sensors with high sensitivity, selectivity, and reliability. 2. Description of the Related Art [0004] Electrochemical sensors are ubiquitous due to their ability to interact and measure the presence of desired species in molecular form in diverse fields, including environmental monitoring, health diagnostics, industrial processes, and many more. The key information is derived from the fundamental interactions between the sensor surface and its immediate environment (typically, a fluid environment in close contact with the sensor). In addition to the interfacial phenomena, such as diffusion, adsorption, charge-transfer, and double layer formation, several other factors are also crucial in evaluating the success of an electrochemical sensor device, particularly in complex real-world applications. These include the degree of signal transduction (sensitivity), reliability under repeated cycling, impact of physical stimuli such as pH and temperature, and selectivity amidst other interfering species. Nanoscale materials with unique geometries, such as nanowires, nanotubes, and nanosheets with semiconducting and metallic type electronic properties, have demonstrated transformative sensing characteristics in the past for electrochemical sensing addressing low sensitivity issues. However, these materials are often functionalized with recognition agents that can cause instabilities, such as leaching and low binding affinities. Therefore, achieving an optimal balance between sensitivity, stability, and reliability, while ensuring selective detection of molecular species in the environment through improved functionalization strategies or with materials that do not require functionalization is the primary goal in developing state-of-the art sensor materials and devices. [0005] Phosphorus in the form of phosphates is essential for all life forms on Earth to carry out many biological processes, such as synthesis of genetic material (DNA and RNA), formation of cell membrane (phospholipids), cellular energy transfer (ATP), activation of enzymes, maintenance of blood pH, and many more. In the agricultural ecosystem, phosphate is one of the major macronutrients for plant growth and reproduction. However, the available phosphate for plants in the soil (inorganic orthophosphates) is often limited due to its tendency to bind with soil particles and metals, forming complexes that render it inaccessible to plants, thereby resorting farmers to apply phosphate fertilizers to maximize the availability of P in soil for plant uptake. Adversely, unregulated use of phosphate as fertilizer disrupts soil microbial activity and poses risks to crop health, ultimately reducing the crop yield. Furthermore, excess phosphate gets leached into nearby water bodies, causing eutrophication. Therefore, maintaining an optimal presence of phosphorus in the soil environment is necessary. This urges careful monitoring of phosphates with the development of reliable sensor technologies. While many laboratory-based techniques exist for detecting phosphate, developing an in-field electrochemical phosphate sensor is preferred for its portability, affordability, rapid response time, and sensitivity. [0006] Several mechanisms have been proposed in the past to develop phosphate-based electrochemical sensors. A common approach involved immobilization of a synthetic anion receptor with an integrated redox active element on a working electrode in voltammetry techniques to create an electrochemical signal for detection. Some sensing of phosphate ions has been conducted in solution phase anion receptors with redox elements as opposed to invariably immobilizing the receptor on the electrode as mentioned before. On the other hand, potentiometric technique often involved the use of an ionophore in a membrane matrix or metal as ion selective electrode (“ISE”) for selective detection of phosphate ions. In other cases, the classical EPA- approved molybdenum blue method used in colorimetric technique to detect phosphates has been utilized. [0007] In the classical method, the phosphomolybdenum complex (“PMC”) formed in the presence of phosphate and molybdate in an acidified medium (Equation (1)) is reduced to a mixed molybdenum oxidation state using an ascorbic