Seeded Growth of Large-Area Arrays of Substrate Supported Au Nanoparticles Using Citrate and Hydrogen Peroxide

While seeded growth of quasi-spherical colloidal Au nanoparticles (NPs) has been extensively explored in the literature, the growth of surface supported arrays of such particles has received less attention. The latter scenario offers some significant challenges, including the attainment of sufficient particle-substrate adhesion, growth-selectivity, and uniform mass-transport. To this end, a reaction system consisting of HAuCl₄, citrate, and H₂O₂ is here investigated for the growth of supported arrays of 10 nm Au seeds, derived via block copolymer (BCP) lithography. The effects of the reagent concentrations on the properties of the resultant NPs are evaluated. It is found that inclusion of citrate in the growth medium causes substantial particle desorption from Si surfaces. However, the presence of citrate also yields NPs with more uniformly circular top-view cross sections ("quasi-circular"), motivating the exploration of particle immobilization methods. We demonstrate that atomic layer deposition (ALD) of a single cycle of HfO₂ (∼1 Å), after the seed particle formation, promotes adhesion sufficiently to enable the use of citrate without the added oxide noticeably affecting the shape of the resultant NPs. The presented ALD-based approach differs from the conventional sequence of depositing the adhesion layer prior to the seed particle formation and may have advantages in various processing schemes, such as when surface grafting of brush layers is required in the BCP lithography process. A proof-of-concept is provided for the growth of large-area arrays of supported "quasi-circular" Au NPs, in a rapid one-step process at room temperature.

Facile, one-pot, in aqua synthesis of catalytically competent gold nanoparticles using pyrogallol[4]arene as the sole reagent

Rapid and facile synthesis of macrocycle-capped gold nanoparticles employing pyrogallol[4]arenes as a dual-role reducing and stabilizing agent.

Gold as a modifier of metal nanoparticles: effect on structure and catalysis

Bimetallic gold based catalysts have been prepared using a sol immobilisation technique. Depending on the second metal different structure have been obtained.

In Situ Generation of Two-Dimensional Au-Pt Core-Shell Nanoparticle Assemblies

Two-dimensional assemblies of Au-Pt bimetallic nanoparticles are generated in situ on polyethyleneimmine (PEI) silane functionalized silicon and indium tin oxide (ITO) coated glass surfaces. Atomic force microscopy (AFM), UV-Visible spectroscopy, and electrochemical measurements reveal the formation of core-shell structure with Au as core and Pt as shell. The core-shell structure is further supported by comparing with the corresponding data of Au nanoparticle assemblies. Static contact angle measurements with water show an increase in hydrophilic character due to bimetallic nanoparticle generation on different surfaces. It is further observed that these Au-Pt core-shell bimetallic nanoparticle assemblies are catalytically active towards methanol electro-oxidation, which is the key reaction for direct methanol fuel cells (DMFCs).