Easy Preparation of Electrode Surfaces with Dispersed Size-Controlled Au Nanoparticles by Electrodeposited PPI-Dendrimers as Templates

Abstract

The main target of this work is the preparation of nanostructurated surfaces with size-controlled gold nanoparticles to obtain effective electrocatalytic surfaces. In this paper, we show that dispersed Au nanoparticles (AuNPs) having diameters of less than 3 nm can be synthesized in situ with aminoferrocenyl-and amidoferrocenyl-poly(propyleneimine) (PPI) dendrimers previously electrodeposited onto electrode surfaces. Dendrimers of first, third and fifth generation have been studied and good dispersed non aggregated nanoparticles were obtained in all the cases. In a similar way than in homogeneous media, inter-dendrimer Au nanoparticles have been obtained when first or third generation dendrimer modified electrodes were used, while smaller nanoparticles were obtained with fifth generation dendrimer, indicating that intra-dendrimer Au nanoparticles have been synthesized. The AuNPs were obtained from a HAuCl 4 solution after chemical reduction with NaBH 4 . The formation of AuNPs was followed by UV-Vis spectroscopy; electrochemistry and ultra-high resolution scan electron microscopy (HRSEM). The obtained electrodes have been successfully used for the tetraelectronic oxygen reduction reaction (ORR) with a low onset potential (0.00 V vs. SCE), high kinetic current densities and also high heterogeneous electron transfer rate constants.

Monodispersed Size-Controlled Gold Nanoparticles from Electrodeposited Aminoferrocenyl Dendrimer-Templates and Their Application as Efficient Hydrogen Peroxide Electrocatalyst

“…The complete AFM study, including depth, arithmetic mean roughness (Ra), square average roughness (Rms) and density as a function of the dendrimer deposited mass and relative electrode sur-face area was reported earlier. 12 In short, it was demonstrated that the compactness, as an apparent density calculated from the dendrimer coverage and the AFM depth measurements, slightly increases for the AMN films as the dendrimer generation increases (0.0027, 0.0064 and 0.0132 mg cm −3 for AMN1, AMN3 and AMN5 respectively). The formation of AuNPs causes a drastic increase in the compactness of films (0.024, 0.035 and 0.059 mg cm −3 for Au-AMN1, Au-AMN3 and Au-AMN5 respectively), more pronounced for the fifth generation, as can be seen in Fig.…”

“…The morphology of these electrode surfaces, with and without AuNPs, was studied earlier. 12 Briefly, the dependence of the sizes of obtained holes and the porosity and density of AMN films on the dendrimer generation, allowed us to prepare monodispersed inter-or intra-dendrimer AuNPs with generation-dependent sizes. The tapping mode AFM imaging (Fig.…”

“…Electrodes preparation.-The modified Au-AMN electrodes were obtained as described previously. 12 Briefly, Pt disk electrodes (3 mm diameter) were polished with 0.1 μm alumina powder, rinsed with water in an ultrasonic bath, and then conditioned by cycles of potential between the limits for hydrogen and oxygen evolution in H 2 SO 4 0.5 M solution until well-defined cyclic voltammograms were obtained. All the generations of dendrimer films were electrodeposited under potentiostatic control at +1.0 V (vs. Ag/Ag + ) from an electrolyte bath containing the redox active species (1 mM ferrocene) and TBAH 0.1 M in deaerated dichloromethane.…”

“…In a recent paper, 12 we have reported the preparation of electrodes modified with monodispersed size-controlled AuNPs, synthesized in situ on aminoferrocenyl (AMN) and amidoferrocenylpoly(propyleneimine) (AMD) dendrimers, previously electrodeposited onto electrode surfaces, and their catalytic application for the tetra-electronic oxygen reduction reaction (ORR) with a low onset potential. The electrodes obtained with AuNPs on AMD dendrimers have been also successfully used for the electrochemical sensing of dopamine.…”

Machine learning–based inverse design for electrochemically controlled microscopic gradients of O 2 and H 2 O 2

“…The is 2.0 × 10 −8 A/m 2 , and is 8.0 × 10 −7 A/m 2 , based on literature and measurement ( SI Appendix , Fig. S5 ) ( 69 , 70 ).…”