System and method for detection of an analyte in a gaseous sample

The system i.e. detector (1), has a porous material layer (30) formed at a surface (21) of transparent or translucent substrate (20) so as to longitudinally extend along a fluid flow path of gas sample, where the layer contains a set of probe molecules (31). A generation unit (41) generates flow of gas sample along the flow path, so that the gaseous sample contacts the porous material layer. An optical detection device (50) successively detects modification of spectral properties of one of the probe-molecules at distinct detection zones of the layer distributed along the path. The layer is made of micro porous or sol-gel nanoporous material of metal oxides or polymer. Independent claims are also included for the following: (1) a method for production of a detection system of analytes in a gas sample (2) a method for detecting analytes of interest present in a gas sample.