Final Report Summary - PHASE (Phosphonic Acids: Surface Electrochemistry) The aim of the project was to study the electrochemistry of phosphonic acid (PA) molecules on single crystal surfaces of gold and platinum metals along with metallic nano particles (NP), in order to provide an insight into their potential uses in energy production/storage and other electrochemical systems. PAs, which behave as surfactants, have been scarcely studied up to this date. These molecules and their derivatives have been employed for the bio-compatibilization of artificial implants (to reduce the risk of rejection from the patient’s immune system), and as materials in water-free fuel cells, proton-conducting polymer electrolytes at intermediate temperatures (100 to 200 °C), but even in those applications the number of publications up to this date remains low. PAs form interesting surface aggregates as well as aggregates in solution (such as discoidal shaped micelles) due to the strong hydrogen bond interactions between the head groups of their molecules. This confers them with unique properties for water-free electrochemical systems and the fabrication of tailor made metallic NPs for uses in catalysis and sensors. It is for these reasons that, for the first time, a systematic study of the behaviour of these molecules in an electrochemical environment was performed, in order to fully characterize them for guiding their use in future technological applications that can benefit society in fields such as energy production and even medicine through their applications in biosensors. In this project, we have developed a systematic approach for the characterization of PAs. For this we worked with both short carbon chain phosphonic acids, such as the ten-carbon phosphonic acid (DPA) and with water-insoluble PAs, such as the eighteen carbon chain phosphonic acid (OPA). These two molecules represent the two extremes of possible behaviours we can encounter for these species in electrochemical systems. Soluble molecules can exist as monomers freely moving in the water phase, until an electrical potential is applied at the electrode’s surface. Once this potential is applied (and depending on its intensity) the molecules then form different types of surface aggregates which can act as coatings, conferring special properties to the electrode for different applications. In this study, we have developed a systematic methodology to fully characterize the electrochemical behaviour of phosphonic acids. The initial approach was to study the thermodynamics of adsorption by means of classical electrochemical techniques, such as cyclic voltammetry (CV), differential capacitance (DC), chronoamperometry (CA) and chronocoulometry (CC). Once this was achieved, theoretical modelling of the systems, both by density functional theory (DFT) and molecular dynamics (MD) was done, to fully understand the observed phenomena. Finally, possible applications of phosphonic acids for NP fabrication and their use in catalysis and sensors were explored. For this, different techniques such as atomic force microscopy (AFM) along with scanning electron microscopy (SEM) were employed for the characterization of the resulting nano-materials. In addition, the course of the proposed project has allowed us to develop unexpected use of the gold NPs fabricated by means of phosphonic acids templating, in DNA biosensors, through a collaborative project with CONICYT from Chile. Publications on these results are already being prepared.From an individual point of view the Research Fellow has received important training which will be very useful for his future career. He has acquired a deep intellectual knowledge in the application of differential capacitance studies to surfactant systems in electrochemistry and catalytic chemistry.His participation in the supervision of undergraduate and graduate students has provided him with leadership qualities. The participation in international meetings and in the internal group meetings has also improved his knowledge transfer skills.As a conclusion, from this project we have been able to achieve the objectives we proposed in our application. We have demonstrated the possibility of using phosphonic acids for electrocatalysis applications and for the fabrication of nano-materials for other applications such as sensors. Thorough a collaborative effort with the Chilean research council (CONICYT), we have successfully applied the developed nanomaterials to construct a new DNA biosensors for the detection of the helicobacter pylori which will help in the early detection of the infection, thus reducing the risk of developing stomach cancer in patients. This was an unexpected result that further contributes to the application of electrochemistry to fulfilling societal needs not only in the energy sector, but also in medicine.Because of this work the Research Fellow has acquired a strong intellectual knowledge and practical skills which have allowed him to consolidate his future career.
