Template-free electrosynthesis of gold nanoparticles of controlled size dispersion for the determination of lead at ultratrace levels

Template‐ and Additive‐free Electrosynthesis and Characterization of Spherical Gold Nanoparticles on Hydrophobic Conducting Polydimethylsiloxane

“…To prevent any pre-adsorptiono ft he gold ions on the C-PDMS, ar elatively high anodic potential (1.5 V) was chosen at the beginning of the potentialp ulse, rather than starting the experiment at the open-circuit potential. [13,15] Figure 2s hows the chronoamperograms recorded at C-PDMS in 1mm HAuCl 4 /0 .4 m HCl at (A) À0.6 Va nd (B) 0.43 V, both after ar est potential at 1.5 Vf or 10 s. In Figure 2(A), ar apid decrease of the cathodic current is visible, which is associated withd ouble layer charginga nd immediate ion-transfers. The subsequentcathodic current increases with time is related to the increase of the overall electroactive area due to the formation of fresh Au nuclei on the C-PDMS substrate and the enhanced mass transfer to the individual nuclei based on hemispherical diffusion of HAuCl 4 .A fter ac ertain time (t m ), the cathodic current reaches am aximum (i m )a st he diffusion zones overlap from the adjacent nuclei dominated by linear diffusion, which is accompanied by ad ecrease of the cathodic current obeying Cottrell equation.…”

“…Although the potential sweep direction was reversed at −0.6 V, the electrodeposition of Au still happened even in the reverse potential scan at a steady rate of mass flow of HAuCl 4 until reaching the potential of 0.63 V. At potentials more anodic than 0.70 V, the reaction shown in Equation (1) is reversed and the deposited Au is anodically oxidized. Since Cl − is a good complexing ligand for Au III , a sharp anodic peak is expected in the positive potential scan . However, we observed a broad anodic peak with multiple humps covering a wide anodic potential range.…”

“…Therefore, based on preliminary experiments, we chose 1.5 V, −0.6 V and 0.43 V for the triple pulse experiment as the suitable precondition, nucleation and growth potentials in the present work. To prevent any pre‐adsorption of the gold ions on the C‐PDMS, a relatively high anodic potential (1.5 V) was chosen at the beginning of the potential pulse, rather than starting the experiment at the open‐circuit potential …”

“…Since Cl À is ag ood complexing ligand for Au III ,as harp anodicp eak is expected in the positive potential scan. [15] However,w eo bserved ab road anodic peak with multiple humps covering aw ide anodic potential range. It suggests that the anodic leaching of Au from C-PDMS is ak inetically sluggish process.…”

“…[12] In this respect, severalt emplate-free electrosynthesis strategies have been developedinrecent years for the controlled electrochemicals ynthesis of metal nanoparticles on conventional electrode materials. [13][14][15][16][17][18][19][20][21][22] However,t ot he best of our knowledge, no attempt has been made to investigate the templateand additive-freee lectrosynthesis of gold nanoparticleso n ah ydrophobic, soft substrate such as C-PDMS, whichi sp resented here from an aqueous solution of HAuCl 4 in dilute hydrochlorica cid (HCl). Any chemical or physical treatment of C-PDMS and addition of further chemicals have been avoided during the electrochemical preparation.…”