Spectrophotometric and Electrochemical Study of Gold‐Iodide in Aqueous Borate Medium

Abstract

The constant-current electrolysis technique was utilized to determine the oxidation state of gold in iodide media. The products from the electrolysis of gold metal in KI with 0.1 M borate were analyzed by means of electrogravimetry for gold and spectrophotometry for 12. At low current density, the gold species formed during the electrolysis process was Au(I) in KI with 0.1 M borate. Voltammetric measurements for the solution resulting from electrochemical dissolution of gold in 1 M KI + 0.1 M K2B407 on a glassy carbon rotating disk electrode enable us to measure the diffusion coefficient of Au(I) in the same medium, which was found to be 6.81 >< iocm2 s. The equilibrium of the chemical reaction between gold and iodine in the medium of 1 M KI + 0.1 M K2B407 was also studied. The experimental results confirmed that the complex formed between Au(I) and iodide is AuI. The stability constant for AuI was determined by direct analysis of equilibrated solutions and was found to be 12 = (AuIfl/(Au)(fl2 = 3.42 X 10° M2. * Electrochemical Society Student Member. * * Electrochemical Society Active Member.

AuBr2–-Engaged Galvanic Replacement for Citrate-Capped Au–Ag Alloy Nanostructures and Their Solution-Based Surface-Enhanced Raman Scattering Activity

“… Meanwhile, I – was oxidized to form I 2 , which combined with excess I – to yield I 3 – (eq S2). As shown in Figure S3, the addition of KI caused the disappearance of the AuCl 4 – peak at 300 nm and the appearance of peaks assigned to I 3 – at 287 and 350 nm . I 3 – can be reduced to I – by the following addition of AA according to stoichiometry, and the solution declined to colorless.…”

Electrodeposition of Gold

“…The stability of the gold cyanide complex causes the reduction potential to occur at very negative potentials, resulting in the coreduction of hydrogen ions, which lowers the plating efficiency and makes the development of electroless plating baths difficult [40]. The release of free cyanide during the reduction of [Au(CN) 2 ] À can be incompatible with positive photoresists used in the microelectronics industry [41,42]. It has also been found that the residual stress of the plated gold can be controlled in noncyanide baths [43,44].…”

“…The bath composition is as follows: The deposition of gold from the iodide-thiosulfate bath was also studied [42]. It was suggested that the chemical reaction preceding the electron transfer step is the dissociation of the [Au(S 2 O 3 ) 2 ] 3À to form [Au(S 2 O 3 ) 2 ] À and S 2 O 2À 3 In each of the studies involving a mixed-thiosulfate bath (sulfite-thiosulfate and iodide-thiosulfate), it was observed that the mixed-salt gold complex is more stable and harder to reduce than either of the single-salt complexes [39][40][41][42]. That is, the Au(I) sulfite-thiosulfate complex is reduced at potentials more negative than either the Au(I) sulfite or Au(I) thiosulfate complex.…”

A comprehensive review of various non-cyanide electroplating baths for the production of silver and gold coatings

“…The electron transfer at the cathode was reported to be slow, and the transfer coefficient (α) was found to be around 0.76. The electrochemical reactions taking place at the anode from an iodide-thiosulphate bath were also reported [166]. Semi-bright, smooth, and uniform gold deposits were obtained using an optimized composition of the electroplating bath at an optimized operating condition.…”