Waveguide with outer coating for analyte detection

A method of using an optical sensing element, for detecting an analyte in a fluid medium, that is obtained by the method comprising:

• providing an optical waveguide comprising an optically transparent material that essentially consists of a metal halide for guiding light through the sensing element;
• depositing an inorganic coating that essentially consists of an inorganic material for adsorbing the analyte from the fluid medium;
• and
• depositing, prior to depositing the inorganic coating, an adhesion promotion material or precursor thereof, onto the optically transparent material, to form an inorganic adhesion promotion layer that essentially consists of a metalloid, a metal, a metal oxide, a metalloid oxide, or mixtures thereof for promoting adhesion of the inorganic material;
• wherein the inorganic coating comprises zirconium oxide and/or zirconium hydroxide for the detection of a pnictogen compound, in particular phosphate, as the analyte, and
• wherein the method of using the optical sensing element comprises:
• contacting at least a portion the inorganic coating with a fluid medium to be tested for presence of said analyte,
• measuring an absorption spectrum of light guided through the optical waveguide, and
• determining a presence or concentration of the analyte based on the measured absorption spectrum.

An optical sensing element for detecting an analyte in a fluid medium, the sensing element comprising:

• an optical waveguide comprising an optically transparent material that essentially consists of a metal halide for guiding light through the sensing element;
• an inorganic coating essentially consisting of an inorganic material for adsorbing the analyte from the fluid medium;
• and
• an inorganic adhesion promotion layer that is formed between the optical waveguide and the inorganic coating,
• wherein the inorganic adhesion promotion layer comprises an adhesion promotion material that essentially consists a metalloid, a metal, a metal oxide, a metalloid oxide, or mixtures thereof for promoting adhesion of the inorganic material.

A detector system for detecting a target analyte comprised in a fluid medium, the detector system comprising:

• an optical sensing element for detecting the target analyte in a fluid medium, the sensing element comprising:
• an optical waveguide comprising an optically transparent material that essentially consists of a metal halide for guiding light through the sensing element;
• an inorganic coating essentially consisting of an inorganic material for adsorbing the target analyte from the fluid medium;
• and
• an inorganic adhesion promotion layer that is formed between the optical waveguide and the inorganic coating,
• wherein the inorganic adhesion promotion layer comprises an adhesion promotion material that essentially consists a metalloid, a metal, a metal oxide, a metalloid oxide, or mixtures thereof for promoting adhesion of the inorganic material;
• a light source for generating light;
• and
• a detector for measuring an absorbance of the light;
• wherein the optical sensing element is positioned along a light path between the light source and the detector,
• wherein the optical waveguide is arranged to guide the light from the light source towards the detector via the light path, and
• wherein at least a portion of the light path overlaps with the inorganic coating to allow the light to interact with the target analyte.