Stimuli-responsive polymer brushes with adsorbed fluorescent semiconductor nanocrystals can be used in solvent-sensitive sensors based on the fluorescence-interference contrast (see figure) of semiconductor nanocrystals near a reflecting silicon surface. The reversible, solvent-depending swelling of a thin, surface-anchored film of poly(2-vinyl pyridine) using hydrophobic CdSeS nanocrystals leads to a high temporal and spatial resolution of the fluorescence images.