Growth of electrodeposited gold on glassy carbon from a thiosulphate–sulphite electrolyte

Theoretical and experimental studies of the influence of gold ions and DMH on cyanide-free gold electrodeposition

Quantum chemical calculations based on density functional theory (DFT) were employed to determine an appropriate gold source for gold electroplating and to ascertain the stable structures of gold-complexes in cyanide-free electrolyte. Based on the charge distribution of 5,5-dimethylhydantoin (DMH) and the bonding energy of gold complexes, Au³⁺ is the appropriate gold source for DMH-based gold electroplating electrolyte to get greater cathodic polarization and [Au(DMH)₄]⁻ with 2N(4)–Au coordination structure is the most stable form of gold ion in the electrolyte. The influence of DMH, used as the complexing agent, on electrochemical behaviors was investigated using cathodic polarization, cyclic voltammetry, and chronoamperometry measurements. With DMH as the complexing agent, the cathodic polarization of gold electrodeposition was significantly enhanced. DMH concentration was determined as 0.30 mol L⁻¹ based on the investigation of the influence of the DMH concentration on cathodic polarization and gold electrodeposit micromorphology. The kinetic features based on cyclic voltammogram measurements revealed that the electrodeposition was an irreversible process under diffusion control with 0.30 mol L⁻¹ DMH as the complexing agent. The ion and electron transfers were obviously inhibited by DMH. The gold electrodeposition process displayed progressive nucleation according to the Scharifker and Hills nucleation model with various applied potentials. The growth rate of the crystal nucleus was reduced by DMH and promoted by a negative shift of E_ap.

Au³⁺ is the appropriate gold source for the DMH-based gold electroplating electrolyte to get greater cathodic polarization.

Role of polyethyleneimine as an additive in cyanide-free electrolytes for gold electrodeposition

Study of the influence of polyethyleneimine on the cyanide-free gold nucleation process and morphology of gold electrodeposits.

Carbon nanowalls amplify the surface-enhanced Raman scattering from Ag nanoparticles

We report surface-enhanced Raman scattering (SERS) from Ag nanoparticles decorated on thin carbon nanowalls (CNWs) grown by microwave plasma chemical vapor deposition. The Ag morphology is controlled by exposing the CNWs to oxygen plasma and through the electrodeposition process by varying the number of deposition cycles. The SERS substrates are capable of detecting low concentrations of rhodamine 6G and bovine serum albumin, showing much higher Raman enhancement than ordinary planar HOPG with Ag decoration. The major factors contributing to this behavior include: high density of Ag nanoparticles, large surface area, high surface roughness, and the underlying presence of vertically oriented CNWs. The relatively simple procedure of substrate preparation and nanoparticle decoration suggests that this is a promising approach for fabricating ultrasensitive SERS substrates for biological and chemical detection at the single-molecule level, while also enabling the study of fundamental SERS phenomena.