Electrochemiluminescence fundamentals and analytical applications

This chapter covers the fundamental theory and the different compounds, materials and composite materials that have been utilised for analytical applications using electrochemiluminescence (ECL). Most commonly ruthenium based systems have been exploited for their optical and electrochemical properties but more recent research has examined the combination of ruthenium with antibodies, aptamers as well as nano-materials to expand the variety of applications to which this ECL material can be applied. The discovery of these new materials has opened up new avenues for ECL sensors within the field of biomedical diagnostic. In addition, new inorganic metal complexes, nanoparticles and polymer systems have also been showed to produce ECL signals and these are now challenging the dominance of ruthenium-based systems. All of these systems undergo similar reactions to produce an ECL response from electrochemical generated intermediates that undergo highly exoergonic reactions, to produce electronically excited states that emit light. These electron-transfer reactions are sufficiently exergonic to allow the excited states of luminophores, including metal complexes, quantum dots and carbon nanocrystals, to be generated without photoexcitation. This chapter highlights the fundamental requirements and pathways for ECL production as well as reviewing the most significant advancements related to the use of these novel materials and their composites, for analytical applications of ECL based systems.