Photochromism of organic compounds is defined as a reversible transformation induced in one or both direction by light between two isomeric states with different properties, such as change in their geometry, polarity, UV-Vis absorption bands, etc. The thickness of poly (N-isopropylacrylamide) (PNIPAM) grafted on gold nanoparticles arrays was measured by atomic force microscopy (AFM) in air at room temperature. The AFM images of GNP arrays recorded before and after grafting of PNIPAM allow estimating the dry PNIPAM thickness which is around 5 nm. In order to characterize the thermosensitive properties of the system, considered its optical extinction changes with temperature in water. At room temperature in water the PNIPAM adopts a swollen conformation. Light irradiations were performed using a spot light source through a NIR long pass filter, to protect samples from thermal effects, and appropriate band pass filters to select either UV or visible light, before reaching the sample.