AgAu Nanotubes: Investigating the Effect of Surface Morphologies and Optical Properties over Applications in Catalysis and Photocatalysis

Abstract

We herein report the preparation of AgAu nanotubes displaying controlled surface morphologies and optical properties by varying the reaction temperature during the galvanic reaction between Ag nanowires and AuCl 4 -(aq) . As the AgAu nanotubes presented similar sizes and compositions, they enabled us to isolate the influence of surface morphology and optical properties over their catalytic and plasmonic photocatalytic activities towards methylene blue oxidation. At 25 °C, AgAu nanotubes (AgAu 25) presented branched walls and surface plasmon resonance (SPR) band with low intensities in the visible were obtained. However, at 100 °C, the AgAu nanotubes (AgAu 100) presented smooth surfaces and SPR bands that closely matched the emission spectra of a commercial halogen-tungsten lamp. The AgAu 25 nanotubes displayed better catalytic performances in classical heterogeneous catalysis as a result of its branched walls that lead to increased surface areas relative to the smooth nanotubes. Conversely, AgAu 100 nanotubes showed better activities in plasmonic photocatalysis due to its broader and more intense SPR bands. Thus, our results demonstrate the potential of the control over morphological and optical features towards the optimization of distinct catalytic phenomena.Keywords: AgAu nanotubes, surface morphology, optical properties, catalysis, plasmonic photocatalysis IntroductionMetal nanostructures have played a central role in several branches of science and technology including electronics, 1,2 photonics, 3-5 medicine, 6,7 energy production, 8,9 environmental remediation, 10,11 and catalysis. 12-15 Among various metallic nanomaterials, those based on gold (Au) and silver (Ag) have attracted special attention due to their fascinating optical properties in the visible range as a result of their localized surface plasmon resonance (LSPR) excitation. 16,17 In addition to properties in sensing (enhanced spectroscopies), the LSPR excitation can also be put to work towards the promotion and/or enhancement of chemical processes, the so-called plasmonic catalysis that has emerged as a new frontier in the field of photocatalysis. [18][19][20] Nanoparticles based on noble metals have also been widely employed in the field of heterogeneous catalysis and electrocatalysis due to their good stability and catalytic activities towards a wealth of transformations including oxidations, 15,[21][22][23] reductions, 9,24 coupling reactions, [25][26][27][28] among others. 8,[29][30][31] In these applications, it has been established that the precise control over their morphological and optical properties is a promising strategy to enhance/ optimize their performances. 29,[32][33][34][35][36][37] Even though a large number of protocols have been described for the synthesis of plasmonic nanoparticles, new protocols that further enable the understanding and correlation of how catalytic responses are dependent on their morphological and optical features are needed to offer further insights into the rational design of catalysts with improved p...

Gold and gold-palladium branched nanocrystals for applications in plasmonic catalysis and electrocatalysis

“…[50][51][52] The shape and morphology of these materials have also been investigated in order to obtain more efficient harvesting of light in photocatalysis applications. [53][54][55] However, branched gold nanoparticles have been poorly studied to date towards this application.…”