Linear arrays of crystalline nanoparticles are able to act in a manner analogous to an optical fibre, but with much smaller dimensions. This effect relies on the interaction between metallic nanoparticles, which has recently emerged as a strategic area widely applicable across physics, chemistry and biology. The interaction creates highly enhanced, localised electric fields of use in optoelectronics, sensing, smart optical films and single molecule detection. This proposal is focussed on understanding in-depth the interaction between nanocrystals. A key aim is use crystalline metal nanocrystals to build sections of optical circuits which exhibit specific functionality and to assess their use in optoelectronics.