Nanoparticles with logic and numeracy: towards 'computer-on-a-particle' optoelectronic devices

The review focuses on semiconductor nanoparticles and hybrid materials obtained by immobilisation of various molecular species on nanoparticulate semiconductors. These materials constitute unique systems combining collective properties of solids with structural diversity of molecules which show distinctive photoelectrochemical properties. Theoretical models of electronic interactions between molecules and semiconductor surfaces have been presented. Additionally, the review summarises the idea of small particles that can work as electronic devices. These devices are able to sense the environment and communicate with other devices and with the user. The devices are based on surface modified wide-band gap semiconductors and the photoelectrochemical photocurrent switching effect. This effect has created a new platform for novel chemical switches, logic gates and other information processing devices. The mechanism of photocurrent switching is discussed with respect to the type of surface complex-support interaction. Photoelectrochemical properties of multicomponent photoelectrodes based on wide band gap nanocrystaline semiconductors modified with various molecules were investigated. The review presents some examples of hybrid materials working as logic devices, including reconfigurable ones and simple arithmetic systems together with mechanistic problems related to nanoscale information processing.