One-pot synthesized plasmonic black gold nanoparticles for efficient photocatalytic CO oxidation

Abstract

Dendritic plasmonic colloidosome, also known as “black gold”, is a unique plasmonic material with broad-spectrum light absorption extending from visible to near-infrared wavelengths. Black gold has demonstrated remarkable performance in challenging and industrially relevant reactions, such as CO₂ reduction, alcohol oxidation, acetylene semi-hydrogenation, and purification of seawater. Unfortunately, one of the major shortcomings of black gold lies in its intricate multi-step synthesis procedure. This involves the step-by-step growth of Au nanoparticles on a dendritic fibrous nanosilica (DFNS) support, a task spanning several days. Furthermore, the need for solid separation through centrifugation after each cycle is an additional bottleneck. Consequently, this complexity poses a challenge for industrial scaling. In this work, we report a simplified and efficient one-pot synthesis of plasmonic black gold. The one-pot method streamlines the synthesis process, significantly reducing the time from days to hours and eliminating the need for solid separation steps, thereby enhancing sustainability. Characterization studies reveal the optimal reaction time of an hour (instead of days) during the growth step, resulting in black gold materials closely resembling those synthesized via the conventional cycle-by-cycle method. We further demonstrated that DPC-60 synthesized via a one-pot protocol efficiently catalyzes CO oxidation under light, achieving 87% CO conversion at 4.0 W cm⁻² without external heating. In situ DRIFTS studies revealed key adsorption sites involved in the CO oxidation reaction, with bridged CO adsorbed on Au⁰ sites reacting faster than linearly adsorbed CO, and CO on high-coordinated Au⁰ sites exhibiting a faster reaction rate than that on low-coordinated sites. Thus, the one-pot synthesis will facilitate rapid exploration of black gold's applications in a range of fields and also pave the way for scalable industrial deployment.