This article reviews progress in modifying electrode surfaces with functional organic molecules which act as signalling units upon molecular recognition of a guest molecule or ion. This process triggers a change in the physicochemical properties of the host assembly which can be monitored by an electrochemical response. Topics covered include: molecular recognition in conjugated polymers; molecular recognition in monolayers formed by Langmuir-Blodgett and self assembly techniques; incorporation of recognition sites (‘molecular gates’) in otherwise passivating monolayers; ion channel sensors. Representative redox moieties include: polythiophene and polypyrrole derivatives, paraquat, ferrocene, tetrathiafulvalene, metalloporphyrins, C ₆₀ , Ru(NH ₃ ) ₆ ³⁺ and Fe(bpy) ₂ (CN) ₂ ⁰ . Issues relevant to the development of practical, commercially-viable sensors are considered.

The improved synthesis of large quantities of small (hydrodynamic diameter 6–8 nm) TiO2 and ZrO2 nanoparticles tailored as a high refractive index agent in holographic acrylate photopolymer composites has been developed. The surface of the particles was modified by p-dodecylbenzenesulfonic acid (organic shell weight fraction is about 50–70%) to render them highly compatible with organic monomer mixtures avoiding aggregation. The exposure to the interference pattern provides fast one-step formation of permanent highly efficient volume phase gratings with excellent transparency in the visible range. A high refractive index modulation amplitude n1 of about 0.0165 has been achieved in the composites containing 25 wt% of TiO2 nanoparticles. The level of light scattering in the gratings does not exceed 8–10% compared to the film without nanoparticles. The holographic grating based on acrylates doped with ZrO2 nanoparticles, first employed in this work, exhibited high photostability in contrast to holographic nanocomposites with TiO2 nanoparticles. Possible applications of such photocurable organic–inorganic nanocomposites are holographic diffractive elements for a number of optical and electro-optical applications or devices based on ordered arrays of functional nanoparticles within organic films.