Surface plasmonic sensing

A method of analysing a fluid comprising a mixture of two or more analytes, including the step of providing a surface plasmonic sensing device comprising:

• a substrate;
• a first array of localised surface plasmon resonance island structures on the substrate;
• a second array of localised surface plasmon resonance island structures on the substrate,
• wherein:
• the localised surface plasmon resonance island structures of the first and second array respectively have first and second surface functionalisation for selective interaction with respective analytes;
• the first surface functionalisation is different to the second surface functionalisation;
• and
• the method further comprising the steps:
• contacting the first and second arrays with said fluid comprising a mixture of two or more analytes and thereby allowing the analytes selectively to interact with the surface functionalisations available on the first and second arrays of localised surface plasmon resonance island structures;
• illuminating the first and second arrays with electromagnetic radiation to cause localised surface plasmon resonance in the composite array;
• receiving reflected or transmitted electromagnetic radiation from the composite array and detecting said localised surface plasmon resonance to analyse one or more characteristics of said analytes;
• obtaining transmission spectra for the reflected or transmitted electromagnetic radiation from the arrays;
• determining from each transmission spectrum at least one spectral characteristic value;
• and
• arranging said spectral characteristic values in a data matrix and carrying out linear discriminant analysis (LDA) on the data matrix to classify the data in the data matrix.