Cruz San Martin, Vinicius

English

Electrodeposition of Au and AuxAg100-x alloys is commonly based on cyanide baths. In this work, AuxAg100-x alloys have been electrodeposited using less toxic thiosulphate solutions. Alloys of different compositions were obtained from solutions with different Au+:Ag+ ion ratios by constant potential deposition. XPS analysis of films of different thicknesses showed that composition of films was homogenous and consistent during growth.Electrodeposited alloys were used to obtain nanoporous gold (NPG) by selective electrochemical Ag dissolution. The potential at which Ag dissolution takes place changed to more positive potentials with increase of Au content as expected. The porous structures were characterised electrochemically by surface area measurements using Pb underpotential deposition (UPD). It was observed that repeated cycling of Pb UPD on NPG led to changes in surface porosity. Following up on studies of surface-alloying during Pb UPD on Au in our group, Pb UPD was explored as a 'tool' to alter the porosity size. The study has shown changes in porosity size depending on number of potential scans, scan rate and initial size of Au ligaments.Electrodeposited AuxAg100-x alloys were analysed by Pb and Cu UPD processes. The main peaks of Pb UPD characteristic for pure Ag shifted towards more positive values for alloys with higher Au content. Also, Pb UPD voltammograms on AuxAg100-x showed an unusual peak, related to the Ag compound and thiosulphate after a systematic study of Pb UPD on pure Ag films electrodeposited from three different solutions. Cu is a metal that forms UPD layer on Au but not on Ag. Cu UPD voltammograms showed similar shifts in the peaks potentials towards more positive values with increase of Au content in alloys. Charges measured for Cu UPD layer decreased with increase in alloy's Ag content. The observations and measurements followed a trend observed on bulk alloys previously reported

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Electrochemical design and characterisation of AuxAg100-x thin films and nanostructures

https://research-information.bris.ac.uk/files/302822936/Final_Copy_2021_09_28_Cruz_San_Martin_V_PhD.pdf

Electrochemical design and characterisation of AuxAg100-x thin films and nanostructures

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