One .zip folder, containing two subfolders ('main' and 'SI'). Data are organised following the structure and figures of main manuscript and Supplementary Information. Datafiles, and all columns and rows inside datafiles, are explicitly labelled according to the part of the Figure they represent. Darkfield spectra were collected confocally with a spot size of approximately 1µm using broadband white light illumination from a halogen bulb, with specta referenced using a white scattering standard. Raman spectra were collected using either a 633nm or 785nm laser, focussed on individual nanoparticles with a spot size of approximately 1µm and optical power 200µW. Electrical measurements were perfomed with a Source Measure Unit, set to output a voltage and measure a current, with fixed detection range and current compliance for each measurement. Minimal post-processing was applied to the presented data, with post-processing generally limited to subtraction of background dark counts of optical detectors (darkfield and Raman spectroscopy), normalisation of the signal to input illumination (darkfield spectroscopy), and subtraction of average baseline electronic noise (electrical measurements). Additional details on equipment, protocols and simulation data are provided in the main manuscript.