Chapter 1 provides an overview of the current literature regarding molecular level modification of conducting surfaces. The modification of carbon surfaces are discussed, with particular attention being given to the use of aryldiazonium salt compounds. Patterning of molecular layers using aryldiazonium salts and arylazides is detailed. The objectives of the project are outlined. Chapter 2 contains the general experimental methods, instrumentation, chemicals, and materials used throughout this thesis. Chapter 3 details the development of two technical methods: a heat treatment method for regenerating diazonium-modified or deactivated pyrolysed photoresist film electrodes, and a method for preparing evaporated carbon film electrodes. Although regeneration of the evaporated carbon surfaces was unsuccessful, the surfaces exhibited good electrochemical properties and are useful substrates for studying diazonium-derived films. Chapter 4 reports the covalent modification of carbon, gold, and indium tin oxide surfaces with thin porphyrin films via the electrochemical reduction of porphyrin aryldiazonium salts. Surface characterisation studies revealed that the films are stably-attached and exhibit well-defined redox and optical properties. Chapter 5 describes the preparation and patterning of organic films on carbon and silicon surfaces using arylazides combined with photolithography. Strategies were investigated to generate continuous mixed films and surfaces presenting patterns of one or two components. For all grafted surfaces, the reactivity of tether species was confirmed by coupling electroactive targets or gold nanoparticles to the tethers, followed by electrochemical analysis or surface microscopy. Chapter 6 details the modification of carbon surfaces with diazonium-derived films via aryltriazenes. Also described in this chapter is the development of microfluidics, for use with aryltriazene and aryldiazonium salt solutions, for generating parallel surface patterns. Chapter 7 concludes and answers to the challenges reported in this study. Future directions are briefly discussed.