SELECTIVE OPTICAL DETECTION OF ORGANIC ANALYTES IN LIQUIDS

A method for detection of an organic analyte in a liquid sample, the method including: providing an assay substrate comprising a first component and a second component; the first component including a sensor molecule labeled with a quantum dot, the quantum dot immobilized to an assay substrate surface with a first linker, the sensor molecule having a specific binding site for an organic analyte, the sensor molecule labeled with the quantum dot in a position that has no effect on the organic analyte binding the specific binding site; the second component including a chemical analogue of the organic analyte, the chemical analogue labeled with a fluorescent dye, the chemical analogue linked to the quantum dot with a second linker having a length exceeding Förster radius, and the chemical analogue reversibly binding the specific binding site of the sensor molecule of the first component; applying the liquid sample to the assay substrate; illuminating the assay substrate to excite fluorescence of the quantum dot; detecting fluorescence of the fluorescent dye; determining presence of the organic analyte by detecting a decrease in fluorescence of the fluorescent dye, due to the organic analyte displacing the chemical analogue from the specific binding site and subsiding a fluorescence resonance energy transfer (FRET) effect between the quantum dot and the fluorescent dye.