Near-field enhancement by plasmonic antennas for photocatalytic Suzuki-Miyaura cross-coupling reactions

Au@C/Pt core@shell/satellite supra-nanostructures: plasmonic antenna-reactor hybrid nanocatalysts

Integration of plasmonic nanoantennas with catalytically active reactors in deliberately designed hybrid supra-nanostructures creates a dual-functional materials platform, based upon which precise modulation of catalytic reaction kinetics becomes accomplishable through optical excitations of plasmon resonances. Here, we have developed a multistep synthetic approach that enables us to assemble colloidal Au@C/Pt core@shell/satellite supra-nanostructures, in which the Au core functions as a light-harvesting plasmonic nanoantenna, the Pt satellites act as catalytically active reactors, and the C shell serves as a nanoscale dielectric spacer separating the reactors from the antenna, respectively. By adjusting several synthetic parameters, the size of the Au core, the thickness of the C shell, and the surface coverage of Pt satellites can all be tuned independently. Choosing Pt-catalyzed cascade oxidation of 3,3',5,5'-tetramethylbenzidine in an aerobic aqueous environment as a model reaction, we have systematically studied the detailed kinetic features of the catalytic reactions both in the dark and under visible light illumination over a broad range of reaction conditions, which sheds light on the interplay between plasmonic and catalytic effects in these antenna-reactor nanohybrids. The plasmonic antenna effect can be effectively harnessed to kinetically modulate multiple crucial steps during the cascade reactions, benefiting from plasmon-enhanced interband electronic transitions in the Pt satellites and plasmon-enhanced intramolecular electronic excitations in chromogenic intermediate species. In addition to the plasmonic antenna effect, photothermal transduction derived from plasmonic excitations can also provide significant contributions to the kinetic enhancements under visible light illumination. The knowledge gained from this work serves as important guiding principles for rational design and structural optimization of plasmonic antenna-reactor hybrid nanomaterials, endowing us with enhanced capabilities to kinetically modulate targeted catalytic/photocatalytic molecule-transforming processes through light illumination.

Promises of Plasmonic Antenna-Reactor Systems in Gas-Phase CO2 Photocatalysis

Sunlight-driven photocatalytic CO2 reduction provides intriguing opportunities for addressing the energy and environmental crises faced by humans. The rational combination of plasmonic antennas and active transition metal-based catalysts, known as "antenna-reactor" (AR) nanostructures, allows the simultaneous optimization of optical and catalytic performances of photocatalysts, and thus holds great promise for CO2 photocatalysis. Such design combines the favorable absorption, radiative, and photochemical properties of the plasmonic components with the great catalytic potentials and conductivities of the reactor components. In this review, recent developments of photocatalysts based on plasmonic AR systems for various gas-phase CO2 reduction reactions with emphasis on the electronic structure of plasmonic and catalytic metals, plasmon-driven catalytic pathways, and the role of AR complex in photocatalytic processes are summarized. Perspectives in terms of challenges and future research in this area are also highlighted.

High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO₂ shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO₂ coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.

Efficient Suzuki-Miyaura cross-coupling reaction by loading trace Pd nanoparticles onto copper-complex-derived Cu/C-700 solid support

The development of efficient carbon-carbon cross-coupling catalysts with low noble metal amounts attracts much attention recently. Herein, a Cu/C-700/Pd nanocomposite is obtained by loading trace Pd²⁺ onto carbon support derived from a novel mononuclear copper complex, {[Cu(POP)₂(Phen)₂]BF₄}. The as-prepared nanomaterial features the facial structure of highly dispersed copper phosphide nanoparticles as well as Pd nanoparticles via neighboring Cu-Pd sites. The Cu/C-700/Pd nanocomposite shows excellent catalytic activity (99.73%) and selectivity in Suzuki-Miyaura cross-coupling reaction, at trace Pd loading (0.43 mol%). Compared with the reported palladium nano catalysts, its advantages are proved. The appealing gateway to this stable, innovative and recyclability, Cu/C-700/Pd nanostructure recommends its beneficial utilization in carbon-carbon coupling and other environmentally friendly processes.