Photoreactive gold nanoparticles (NP) can be encoded in a spatially resolved fashion using direct laser writing techniques into variable patterns. The surface of the gold nanoparticles is imparted with photoreactivity by tethering photo-caged dienes ('photoenols'), which are able to undergo a rapid Diels-Alder cycloaddition with surface anchored enes. Subsequent to surface encoding, the particles feature residual caged dienes, which can be reactivated for secondary surface encoding.