Modulated Triple‐Material Nano‐Heterostructures: Where Gold Influenced the Chemical Activity of Silver in Nanocrystals

Abstract

For efficient charge separations, multimaterial hetero-nanostructures are being extensively studied as photocatalysts. While materials with one heterojunction are widely established, the chemistry of formation of multijunction heterostructures is not explored. This needs a more sophisticated approach and modulations. To achieve these, a generic multistep seed mediated growth following controlled ion diffusion and ion exchange is reported which successfully leads to triple-material hetero-nanostructures with bimetallic-binary alloy-binary/ternary semiconductors arrangements. Ag S nanocrystals are used as primary seeds for obtaining AuAg-AuAgS bimetallic-binary alloyed metal-semiconductor heterostructures via partial reduction of Ag(I) using Au(III) ions. These are again explored as secondary seeds for obtaining a series of triple-materials heterostructures, AuAg-AuAgS-CdS (or ZnS or AgInS ), with introduction of different divalent and trivalent ions. Chemistry of each step of the gold ion-induced changes in the rate of diffusion and/or ion exchanges are investigated and the formation mechanism for these nearly monodisperse triple material heterostructures are proposed. Reactions without gold are also performed, and the change in the reaction chemistry and growth mechanism in presence of Au is also discussed.

Sensing of Iron(III) Ion via Modulation of Redox Potential on Biliverdin Protected Silver Nanosurface

“…41,42 Many researchers synthesized silver nanoparticles doped with other metals. 43,44 In a typical synthesis procedure, 8.6 mg of bilirubin in 25 mL of water was taken in a round-bottom flask covered with aluminum foil and 0.5 M NaOH solution was added dropwise for the dissolution of bilirubin in water. Subsequently 5 mL of 15 mM Ag(I) solution was prepared separately by dissolving a required amount of AgNO 3 in Milli-Q water in a 15 mL Falcon tube.…”

Gold-based nanoalloys: synthetic methods and catalytic applications

“…Different from the co-reduction method, seed-mediated diffusion is a two-step approach that involves the preliminary synthesis of well-dened metal nanostructures as the seed, followed by the introduction of other metal elements into the seed to form nanoalloys. [108][109][110][111] With the utilization of different metal precursors and seeds, various kinds of Au-based coreshell alloy NPs can be obtained in the presence of appropriate reductants and surfactants, such as Au-Ag, Au-Sn, Au-Pt, Au-Hg, Au-Cd and Au-Cu-Ag nanoalloys. 112,113 Considering the synthetic mechanism, this sequential order also makes it suitable for generating core-shell structures, in which the size and morphology of the nal products are closely related to the seeds.…”

“…By modulating the adsorption behaviors of O 2 or *OOH on catalyst surfaces, a better performance towards H 2 O 2 generation can be achieved. For example, Au is regarded as a promising electrocatalyst for H 2 O 2 production because of its low over-potential and unique 2e-ORR on the (111) and ( 110) surfaces. 181 However, the poor adsorption capability of O 2 on Au limits its ORR activity.…”

Change in Rate of Catalytic Growths of Nanocrystals Catalyst for Formation of Asymmetric Multicomponent Heterostructures and Their Self-Assembly

“…Nanomaterials acting as catalyst for facilitating growths of other nanomaterials have opened up a new approach for architecting dual and triple material heterostructures. − Among these, silver chalcogenides remained in the forefront for solution processed growths of different groups II–VI semiconductor nanostructures. ,− These silver chalcogenides have unique characteristic which showed temperature dependent phase transitions from α to β form. ,− At higher temperature, the obtained cubic (or β) phase allows movements of Ag­(+) ions within the lattice, creating vacancies. This provided a new opportunity for insertion of other metal ions and facilitated superionic type catalytic growth leading to semiconductor–semiconductor heterostructures.…”

“…Even such types of secondary growth on silver chalcogenides are widely established, but the physical insights of their mechanism was reported in 2013 . Soon after, several such structures using Ag 2 S and Ag 2 Se as catalysts were developed, and even step growths leading to multisegments of semiconductor-heterostructures were formed. − ,,− ,− One of the key advantages of this approach is obtaining zinc-blende nanorods or nanowires which were typically obtained in wurtzite phase from direct colloidal synthesis protocols. − …”