Efficient Extraction of Energetic Charge Carriers from an Engineered Plasmonic Nanocomposite to Perform Cascade Reactions

Abstract

The realization of plasmon-generated hot charge carriers presents tremendous opportunities for light-harvesting in the field of photocatalysis. However, extracting the energetic charge carriers while competing with their recombination tendency is still a major bottleneck for efficient plasmonic photocatalysis. Therefore, strategic changes in the design principles of hybrid plasmonic nanocomposites to generate highly localized charge carriers at the catalytic site are imperative for hot electrons (holes) transfer to short-lived reaction intermediates. Here, we engineered AuÀ Pt core-shell nanostructures with only a few monolayers of epitaxially grown Pt onto Au nanocubes. The finite element method (FEM) simulations for optical properties of AuÀ Pt system support the design and hypothesis of selective funneling of plasmonic energy/charge carriers from Au core to Pt shell and their potential extraction for activating chemical bonds on AuÀ Pt nanocubes (AuÀ Pt NCs) surface. Further, investigating AuÀ Pt NCs as plasmonic catalysts, we show direct, visual evidence of plasmon-assisted cascade reduction of nonfluorescent resazurin (Rz) dye to nonfluorescent dihydroresorufin (DHRf) via a highly fluorescent resorufin (Rf) intermediate form. In the excitation wavelength-dependent study, the maximum apparent quantum efficiency of 48% (Rz to Rf conversion) and 8.4% (Rf to DHRf conversion) at 561 nm laser excitation demonstrates the plasmon assisted charge carrier driven cascade reduction on AuÀ Pt NCs surface. Control experiments carried out with only Au nanocubes (Au NCs) or Pt seed nanoparticles under the same reaction conditions show no significant cascade reduction of Rz, highlighting the synergistic effect of the plasmonic core and ultrathin catalytic shell.

Photocatalytic NADH Regeneration Employing Au–Pd Core–Shell Nanoparticles: Plasmonic Modulation of Underlying Reaction Kinetics

“…In a two-step seed-mediated synthesis of Au–Pd CS NPs, first, we prepared CTAB-capped Pd seed solution by adding 150 μL of 10 mM H 2 PdCl 4 into 2 mL of 100 mM CTAB solution at 60 °C . Subsequently, 260 μL of freshly prepared ice-cold 10 mM NaBH 4 was added to the above mixture under stirring at 700 rpm.…”

“…24−30 Other than that, Au−Pt and Ag−Pt core−shell NPs were synthesized and then used to reduce resazurin and methylene blue. 31,32 To increase the domain of these bimetallic composites in photocatalysis, we have explored Au−Pd core−shell nanoparticles (Au−Pd CS NPs) to regenerate NADH from its oxidized form β-NAD + in a colloidal solution of this bimetallic composite. Previously, few reports have successfully demonstrated NADH regeneration using immobilized Au−Pd nanorods over cellulose fibers and agarose matrix.…”

“…In a two-step seed-mediated synthesis of Au−Pd CS NPs, first, we prepared CTAB-capped Pd seed solution by adding 150 μL of 10 mM H 2 PdCl 4 into 2 mL of 100 mM CTAB solution at 60 °C. 31 Subsequently, 260 μL of freshly prepared ice-cold 10 mM NaBH 4 was added to the above mixture under stirring at 700 rpm. After 2 min of continuous stirring, the obtained yellowish-brown color solution was incubated at room temperature with a ventilated cap for 2 h. 42,43 As-prepared dark brownish Pd seeds were diluted 10 times in 100 mM CTAC for further use.…”

“…by employing only a thin shell . Earlier attempts have been made to incorporate Pd and Pt metals with plasmonic metals for various catalytic purposes such as ethanol oxidation, hydrogen evolution, and various coupling reactions. − Other than that, Au–Pt and Ag–Pt core–shell NPs were synthesized and then used to reduce resazurin and methylene blue. , …”