Au electrodeposition in presence of selfassembling organics:in situstudy by sum frequency generation and surface enhanced Raman spectroscopy

Electroplating offers the possibility of controlling the functional properties of metal films by acting on the metal distribution from the atomic to the mesoscopic scale. Several types of organics have been used to achieve some degree of control over morphology. In this paper, the authors describe three approaches to the modification of electrodeposited Au surfaces based on self-assembling organics: cathode imprinting via functionalisation of the cathode with a dodecanethiol self-assembled monolayer (SAM); electroplating from an aqueous bath containing self-assembling 2-mercaptopyridine; and electroplating from a suspension of liposomes containing the plating solution. This study is based on in situ surface enhanced Raman and sum frequency generation spectroscopies and complemented with electrochemical measurements and SEM observations. Spectroelectrochemical measurements made it possible to correlate the electrodeposition conditions with the cathodic chemistry in terms of: stability and degree of SAM defectivity; potential dependent adsorption and reorientation of SAM forming molecules; and surface coverage with ligands. Under the same plating conditions, growth morphology is changed from acicular in the absence of additives to: lamellar dendrites with the SEM functionalised cathode; localised spongy features with the liposome containing electrolyte; and cauliflower type grains with the 2-mercaptopyridine containing bath.