Disclosed is a localised surface plasmon resonance (LSPR) nanopillar assembly. The LSPR assembly is for use in sensing the presence of a biomarker when attached to a quantum dot. The LSPR assembly comprises a substrate and an array. The array comprises a LSPR nanopillar and a polymer spacer attached to the nanopillar. The LSPR assembly further comprises an antibody attached to the at least one polymer spacer. In the LSPR assembly, a combined height of the polymer spacer and antibody is selected by varying the number of monomer units of the polymer spacer, so that, when in use with the biomarker and the quantum dot, the quantum dot is at a predetermined distance from the nanopillar.