A mechanistic study on the effect of a surface protecting agent on electrocrystallization of silver nanoparticles

Abstract

Cyclic voltammetry and chronoamperometry at characteristic potentials were employed to unravel the mechanism of electrocrystallization of silver nanoparticles (AgNPs) from their aqueous solution in the presence and absence of surface protecting agent tetrabutylammonium tetrafluoroborate (TBABF 4 ). The electrocrystallization parameters viz. initial current density (j 0 ), decay constant (s), diffusion coefficient (D) of Ag(I), number of active sites (N 0 ) and nucleation rate (a) were calculated by fitting the experimentally obtained current transients with the calculated current transients using a hybrid genetic algorithm (HGA).The theoretical currents were calculated from three popular electrocrystallization models viz. Scharifker and Mostany (SM), Sluyters-Rehbach, Wijenberg, Bosco and Sluyters (SRWBS) and Heerman and Tarallo (HT). Each of the three models fitted well by the HGA with the potentiostatic current transients observed at different potentials, both in the absence and in the presence of TBABF 4 with residual sum of squares ($10 À7 ) and reduced c 2 ($10 À10 ). However, the electrocrystallization parameters were distinctly different in each of the three models. Principal component analysis of the calculated parameters i.e. D, N S and aN 0 showed the absence of any correlation among the electrocrystallization parameters derived from the Scharifker and Hills (SH), SM, SRWBS and HT models. Further, the actual nuclei densities of the AgNPs, both in the presence and the absence of TBABF 4 , were found to be significantly higher than the predicted values from any of these models. Since these models are based on different empirical assumptions, one needs be careful in attaching any extra significance to the numerical values of j 0 , s, D, N 0 , "a" of any system only based on the quality of fitting. From the present data, it was conclusively proved that the surface protecting agent slowed down the kinetics of electrocrystallization due to introduction of a higher activation overpotential at the electrode-electrolyte interface and subsequent decreases in the number of nuclei on the electrode surface in the presence of TBA + ions, irrespective of the model.

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

“…[31,32] The work function, Y,c an be expressed by an empirical equation dependento nDE p [Eq. (14)]. Under this condition, the formal redox potential( E 0 ')a nd the standard heterogeneous rate constant (k 0 )o ft he redox reaction can be obtained by Equations (15) and (16).…”

“…[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.…”

“…It has been demonstrated by Brownian dynamic simulation studies that introducing instantaneous nucleation followed by a slow growth process can control the size of the nanoparticles during electrosynthesis . In this respect, several template‐free electrosynthesis strategies have been developed in recent years for the controlled electrochemical synthesis of metal nanoparticles on conventional electrode materials . However, to the best of our knowledge, no attempt has been made to investigate the template‐ and additive‐free electrosynthesis of gold nanoparticles on a hydrophobic, soft substrate such as C‐PDMS, which is presented here from an aqueous solution of HAuCl 4 in dilute hydrochloric acid (HCl).…”

Current atomic-level understanding of electrochemical nucleation and growth on low-energy surfaces

“…Over the years, it has been found that J ST , N ðtÞ, and N 0 obtained experimentally from surface analysis (J ST ÀEXP , N ðtÞ EXP , and N 0ÀEXP ) may be several orders of magnitude higher than those obtained from the CTTs (J ST ÀCTT , N ðtÞ CTT , and N 0ÀCTT ) [19,21,28,41,46,47]. Therefore, some important clarifications related to the interpretation of these data are needed.…”

Template‐free Electrosynthesis of Platinum Nano‐Cauliflowers for Catalysing Electron Transfer Reaction of Plutonium

“…Electrosynthesis is a room-temperature solution phase route to prepare supported metal nanoparticles on electrodes by transferring electrons from external source to the metal ion precursor present in the solution. Although this process can produce metal nanoparticles of best possible chemical purity, the control of size and shape of nanoparticles is very challenging task as it depends on several parameters such as strategy of electrochemical synthesis [5,6], potential pulse parameters [7], nature of the substrate materials [8], and presence of any additional chemical reagents [9]. Different strategies had been adapted to date to prepare platinum nanoparticles of different sizes and shapes by employing cyclic voltammetry at constant scan rate [10] and potentiostatic pulses [11][12][13].…”